Gene Summary

Gene:STK11; serine/threonine kinase 11
Aliases: PJS, LKB1, hLKB1
Summary:This gene, which encodes a member of the serine/threonine kinase family, regulates cell polarity and functions as a tumor suppressor. Mutations in this gene have been associated with Peutz-Jeghers syndrome, an autosomal dominant disorder characterized by the growth of polyps in the gastrointestinal tract, pigmented macules on the skin and mouth, and other neoplasms. Alternate transcriptional splice variants of this gene have been observed but have not been thoroughly characterized. [provided by RefSeq, Jul 2008]
Databases:OMIM, HGNC, Ensembl, GeneCard, Gene
Protein:serine/threonine-protein kinase STK11
Source:NCBIAccessed: 16 March, 2015


What does this gene/protein do?
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Pathways:What pathways are this gene/protein implicaed in?
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Cancer Overview

Research Indicators

Publications Per Year (1990-2015)
Graph generated 16 March 2015 using data from PubMed using criteria.

Literature Analysis

Mouse over the terms for more detail; many indicate links which you can click for dedicated pages about the topic.

Tag cloud generated 16 March, 2015 using data from PubMed, MeSH and CancerIndex

Specific Cancers (5)

Data table showing topics related to specific cancers and associated disorders. Scope includes mutations and abnormal protein expression.

Entity Topic PubMed Papers
Peutz-Jeghers SyndromeSTK11 mutations in Peutz-Jeghers Syndrome
PJS is autosomal-dominant condition caused by mutations of STK11, characterized by gastrointestinal polyposis, mucocutaneous pigmentation, and predisposition to a range of epithelial cancers: including colorectal, gastric, pancreatic, breast, ovarian cancers and sex cord tumors with annular tubules).
View Publications360
Lung CancerSTK11 and Lung Cancer View Publications72
Breast CancerSTK11 and Breast Cancer View Publications45
Lung Cancer, Non-Small CellSTK11 and Non-Small Cell Lung Cancer View Publications30
Pancreatic CancerSTK11 and Pancreatic Cancer View Publications28

Note: list is not exhaustive. Number of papers are based on searches of PubMed (click on topic title for arbitrary criteria used).

Latest Publications: STK11 (cancer-related)

Cao C, Gao R, Zhang M, et al.
Role of LKB1-CRTC1 on glycosylated COX-2 and response to COX-2 inhibition in lung cancer.
J Natl Cancer Inst. 2015; 107(1):358 [PubMed] Article available free on PMC after 01/01/2016 Related Publications
BACKGROUND: Cyclooxygenase-2 (COX-2) directs the synthesis of prostaglandins including PGE-2 linking inflammation with mitogenic signaling. COX-2 is also an anticancer target, however, treatment strategies have been limited by unreliable expression assays and by inconsistent tumor responses to COX-2 inhibition.
METHODS: We analyzed the TCGA and Director's Challenge lung cancer datasets (n = 188) and also generated an LKB1-null lung cancer gene signature (n = 53) to search the Broad Institute/Connectivity-MAP (C-MAP) dataset. We performed ChIP analyses, real-time polymerase chain reaction, immunoblotting, and drug testing of tumor cell lines (n = 8) and primary lung adenocarcinoma surgical resections (n = 13).
RESULTS: We show that COX-2 is a target of the cAMP/CREB coactivator CRTC1 signaling pathway. In addition, we detected a correlation between LKB1 status, CRTC1 activation, and presence of glycosylated, but not inactive hypoglycosylated COX-2 in primary lung adenocarcinoma. A search of the C-MAP drug database discovered that all high-ranking drugs positively associated with the LKB1-null signature are known CRTC1 activators, including forskolin and six different PGE-2 analogues. Somatic LKB1 mutations are present in 20.0% of lung adenocarcinomas, and we observed growth inhibition with COX-2 inhibitors in LKB1-null lung cancer cells with activated CRTC1 as compared with LKB1-wildtype cells (NS-398, P = .002 and Niflumic acid, P = .006; two-tailed t test).
CONCLUSION: CRTC1 activation is a key event that drives the LKB1-null mRNA signature in lung cancer. We also identified a positive feedback LKB1/CRTC1 signaling loop for COX-2/PGE2 regulation. These data suggest a role for LKB1 status and glycosylated COX-2 as specific biomarkers that provide a framework for selecting patients for COX-2 inhibition studies.

Chan KT, Asokan SB, King SJ, et al.
LKB1 loss in melanoma disrupts directional migration toward extracellular matrix cues.
J Cell Biol. 2014; 207(2):299-315 [PubMed] Article available free on PMC after 27/04/2015 Related Publications
Somatic inactivation of the serine/threonine kinase gene STK11/LKB1/PAR-4 occurs in a variety of cancers, including ∼10% of melanoma. However, how the loss of LKB1 activity facilitates melanoma invasion and metastasis remains poorly understood. In LKB1-null cells derived from an autochthonous murine model of melanoma with activated Kras and Lkb1 loss and matched reconstituted controls, we have investigated the mechanism by which LKB1 loss increases melanoma invasive motility. Using a microfluidic gradient chamber system and time-lapse microscopy, in this paper, we uncover a new function for LKB1 as a directional migration sensor of gradients of extracellular matrix (haptotaxis) but not soluble growth factor cues (chemotaxis). Systematic perturbation of known LKB1 effectors demonstrated that this response does not require canonical adenosine monophosphate-activated protein kinase (AMPK) activity but instead requires the activity of the AMPK-related microtubule affinity-regulating kinase (MARK)/PAR-1 family kinases. Inhibition of the LKB1-MARK pathway facilitated invasive motility, suggesting that loss of the ability to sense inhibitory matrix cues may promote melanoma invasion.

Lancaster JM, Powell CB, Chen LM, et al.
Society of Gynecologic Oncology statement on risk assessment for inherited gynecologic cancer predispositions.
Gynecol Oncol. 2015; 136(1):3-7 [PubMed] Related Publications
Women with germline mutations in the cancer susceptibility genes, BRCA1 or BRCA2, associated with Hereditary Breast & Ovarian Cancer syndrome, have up to an 85% lifetime risk of breast cancer and up to a 46% lifetime risk of ovarian, tubal, and peritoneal cancers. Similarly, women with mutations in the DNA mismatch repair genes, MLH1, MSH2, MSH6, or PMS2, associated with the Lynch/Hereditary Non-Polyposis Colorectal Cancer (HNPCC) syndrome, have up to a 40-60% lifetime risk of both endometrial and colorectal cancers as well as a 9-12% lifetime risk of ovarian cancer. Mutations in other genes including TP53, PTEN, and STK11 are responsible for hereditary syndromes associated with gynecologic, breast, and other cancers. Evaluation of the likelihood of a patient having one of these gynecologic cancer predisposition syndromes enables physicians to provide individualized assessments of cancer risk, as well as the opportunity to provide tailored screening and prevention strategies such as surveillance, chemoprevention, and prophylactic surgery that may reduce the morbidity and mortality associated with these syndromes. Evaluation for the presence of a hereditary cancer syndrome is a process that includes assessment of clinical and tumor characteristics, education and counseling conducted by a provider with expertise in cancer genetics, and may include genetic testing after appropriate consent is obtained. This commentary provides guidance on identification of patients who may benefit from assessment for the presence of a hereditary breast and/or gynecologic cancer syndrome.

Okon IS, Coughlan KA, Zhang C, et al.
Protein kinase LKB1 promotes RAB7-mediated neuropilin-1 degradation to inhibit angiogenesis.
J Clin Invest. 2014; 124(10):4590-602 [PubMed] Article available free on PMC after 27/04/2015 Related Publications
After internalization, transmembrane receptors (TMRs) are typically recycled back to the cell surface or targeted for degradation. Efficient TMR trafficking is critical for regulation of several processes, including signal transduction pathways, development, and disease. Here, we determined that trafficking of the angiogenic receptor neuropilin-1 (NRP-1) is abrogated by the liver kinase B1 (LKB1), a serine-threonine kinase of the calcium calmodulin family. We found that aberrant NRP-1 expression in tumor cells from patients with lung adenocarcinoma is associated with decreased levels of LKB1. In cultured lung cells, LKB1 accentuated formation of a complex between NRP-1 and RAB7 in late endosomes. LKB1 specifically bound GTP-bound RAB7, but not a dominant-negative GDP-bound form of RAB7, promoting rapid transfer and lysosome degradation of NRP-1. siRNA-mediated depletion of RAB7 disrupted the transfer of NRP-1 to the lysosome, resulting in recovery of the receptor as well as increased tumor growth and angiogenesis. Together, our findings indicate that LKB1 functions as a RAB7 effector and suppresses angiogenesis by promoting the cellular trafficking of NRP-1 from RAB7 vesicles to the lysosome for degradation. Furthermore, these data suggest that LKB1 and NRP-1 have potential as therapeutic targets for limiting tumorigenesis.

Yalniz Z, Tigli H, Tigli H, et al.
Novel mutations and role of the LKB1 gene as a tumor suppressor in renal cell carcinoma.
Tumour Biol. 2014; 35(12):12361-8 [PubMed] Related Publications
The tumor suppressor LKB1 gene is a master kinase and inhibits mammalian target of rapamycin (mTOR) by activating AMP-activated protein kinase (AMPK) and AMPK-related kinases. LKB1 is a critical intermediate in the mTOR signaling pathway, and mutations of the LKB1 gene have been implicated in the development of different tumor types. Recent evidence indicates that LKB1 alterations contribute to cancer progression and metastasis by modulating vascular endothelial growth factor (VEGF) production. The Ras homolog enriched in brain (RHEB) protein is a component of the mTOR pathway and functions as a positive regulator of mTOR. However, the mechanisms and effectors of RHEB in mTOR signaling are not well known. In this study, we analyzed the expression of RHEB and HIF1α genes in correlation with LKB1 gene mutations. All coding exons and exon/intron boundaries of the LKB1 gene were analyzed by direct sequencing in 77 renal cell carcinoma (RCC) tumors and 62 matched noncancerous tissue samples. In 51.6 % of the patients, ten different mutations including four novel mutations in the coding sequences and six single nucleotide substitutions in the introns were observed. Rheb and HIF1α expression levels were not statistically different between the tumor and corresponding noncancerous tissue samples. However, expression of the Rheb gene was upregulated in the tumor samples carrying the intron 2 (+24 G→T) alteration. Association between the gene expression and tissue protein levels was also analyzed for HIF1α in a subgroup of patients, and a high correlation was confirmed. Our results indicate that the LKB1 gene is frequently altered in RCC and may play a role in RCC progression.

Lao G, Liu P, Wu Q, et al.
Mir-155 promotes cervical cancer cell proliferation through suppression of its target gene LKB1.
Tumour Biol. 2014; 35(12):11933-8 [PubMed] Related Publications
MicroRNAs (miRNAs) are important regulators of many physiological and pathological processes, including cell proliferation, apoptosis, and cell cycle arrest. In this study, we aimed to investigate the biological role of miR-155 in cervical cancer and the underlying molecular mechanism involved in tumorigenesis. The expression of miR-155 in human cervical cancer tissues was detected by real-time PCR. MTT assay and BrdU incorporation assay were used to measure the proliferation of cervical cancer cells. Apoptosis cells and cell cycle distribution were analyzed by flow cytometry. We found that the expression of miR-155 was upregulated in cervical cancer tissues compared to the adjacent non-cancer tissues. Overexpression of miR-155 promoted the proliferation of Hela and SiHa cells. By contrast, downregulation of miR-155 inhibited the growth of cervical cancer cells. Flow cytometry analysis showed that low expression of miR-155 promoted apoptosis and induced cell cycle arrest in Hela and SiHa cells. Moreover, the mRNA and protein expression of LKB1 was significantly reduced in cervical cancer tissues. Luciferase reporter assay demonstrated that LKB1 was a target gene of miR-155, suggesting that miRNA-155 promoted the proliferation of cervical cancer cells by regulating LKB1 expression.

Goodwin JM, Svensson RU, Lou HJ, et al.
An AMPK-independent signaling pathway downstream of the LKB1 tumor suppressor controls Snail1 and metastatic potential.
Mol Cell. 2014; 55(3):436-50 [PubMed] Article available free on PMC after 07/08/2015 Related Publications
The serine/threonine kinase LKB1 is a tumor suppressor whose loss is associated with increased metastatic potential. In an effort to define biochemical signatures of metastasis associated with LKB1 loss, we discovered that the epithelial-to-mesenchymal transition transcription factor Snail1 was uniquely upregulated upon LKB1 deficiency across cell types. The ability of LKB1 to suppress Snail1 levels was independent of AMPK but required the related kinases MARK1 and MARK4. In a screen for substrates of these kinases involved in Snail regulation, we identified the scaffolding protein DIXDC1. Similar to loss of LKB1, DIXDC1 depletion results in upregulation of Snail1 in a FAK-dependent manner, leading to increased cell invasion. MARK1 phosphorylation of DIXDC1 is required for its localization to focal adhesions and ability to suppress metastasis in mice. DIXDC1 is frequently downregulated in human cancers, which correlates with poor survival. This study defines an AMPK-independent phosphorylation cascade essential for LKB1-dependent control of metastatic behavior.

Co NN, Iglesias D, Celestino J, et al.
Loss of LKB1 in high-grade endometrial carcinoma: LKB1 is a novel transcriptional target of p53.
Cancer. 2014; 120(22):3457-68 [PubMed] Article available free on PMC after 15/11/2015 Related Publications
BACKGROUND: Liver kinase B1 (LKB1) is a serine/threonine kinase that functions as a tumor suppressor and regulates cell polarity, proliferation, and metabolism. Mutations in LKB1 are associated with Peutz-Jeghers syndrome as well as sporadic cervical and lung cancers. Although LKB1-null mice develop invasive endometrial cancers, the role and regulation of LKB1 in the pathogenesis of human endometrial cancer are not well defined and are the focus of these studies.
METHODS: LKB1 protein and messenger RNA (mRNA) expression levels were evaluated in high-grade and low-grade endometrioid endometrial cancer (EEC) and cell lines by reverse transcriptase-polymerase chain reaction analysis, Western blot analysis, and immunohistochemistry. Mutational and promoter analyses of the LKB1 gene (serine/threonine kinase 11 [STK11]) were performed to identify the mechanisms that contribute to the loss of LKB1 in high-grade EEC.
RESULTS: Analysis of the LKB1 gene in low-grade and high-grade EECs revealed no genetic mutations, suggesting that alterations in LKB1 transcription may be responsible for LKB1 protein loss in high-grade EEC. Analysis of the LKB1 promoter revealed 4 putative tumor protein 53 (p53) binding sites. Quantitative chromatin immunoprecipitation demonstrated that p53 bound directly to 1 of these sites and increased LKB1 promoter activity 140-fold. LKB1 promoter activity, mRNA, and protein levels were suppressed after silencing of p53 with small interfering RNA and were elevated in cells that overexpressed p53. Levels of p53 mRNA and protein expression were decreased in high-grade EEC and were positively correlated with LKB1 protein levels (Spearman correlation, r=0.601; P<.001).
CONCLUSIONS: LKB1 is a direct transcriptional target of p53. The loss of wild-type p53 in high-grade EEC may contribute to the LKB1 loss observed in these more aggressive tumors.

Linher-Melville K, Singh G
The transcriptional responsiveness of LKB1 to STAT-mediated signaling is differentially modulated by prolactin in human breast cancer cells.
BMC Cancer. 2014; 14:415 [PubMed] Article available free on PMC after 15/11/2015 Related Publications
BACKGROUND: Liver kinase 1 (LKB1) is an important multi-tasking protein linked with metabolic signaling, also controlling polarity and cytoskeletal rearrangements in diverse cell types including cancer cells. Prolactin (PRL) and Signal transducer and activator of transcription (STAT) proteins have been associated with breast cancer progression. The current investigation examines the effect of PRL and STAT-mediated signaling on the transcriptional regulation of LKB1 expression in human breast cancer cells.
METHODS: MDA-MB-231, MCF-7, and T47D human breast cancer cells, and CHO-K1 cells transiently expressing the PRL receptor (long form), were treated with 100 ng/ml of PRL for 24 hours. A LKB1 promoter-luciferase construct and its truncations were used to assess transcriptional changes in response to specific siRNAs or inhibitors targeting Janus activated kinase 2 (JAK2), STAT3, and STAT5A. Real-time PCR and Western blotting were applied to quantify changes in mRNA and protein levels. Electrophoretic mobility shift (EMSA) and chromatin immunoprecipitation (ChIP) assays were used to examine STAT3 and STAT5A binding to the LKB1 promoter.
RESULTS: Consistent with increases in mRNA, the LKB1 promoter was up-regulated by PRL in MDA-MB-231 cells, a response that was lost upon distal promoter truncation. A putative GAS element that could provide a STAT binding site mapped to this region, and its mutation decreased PRL-responsiveness. PRL-mediated increases in promoter activity required signaling through STAT3 and STAT5A, also involving JAK2. Both STATs imparted basally repressive effects in MDA-MB-231 cells. PRL increased in vivo binding of STAT3, and more definitively, STAT5A, to the LKB1 promoter region containing the GAS site. In T47D cells, PRL down-regulated LKB1 transcriptional activity, an effect that was reversed upon culture in phenol red-free media. Interleukin 6, a cytokine activating STAT signaling in diverse cell types, also increased LKB1 mRNA levels and promoter activity in MDA-MB-231 cells.
CONCLUSIONS: LKB1 is differentially regulated by PRL at the level of transcription in representative human breast cancer cells. Its promoter is targeted by STAT proteins, and the cellular estrogen receptor status may affect PRL-responsiveness. The hormonal and possibly cytokine-mediated control of LKB1 expression is particularly relevant in aggressive breast cancer cells, potentially promoting survival under energetically unfavorable conditions.

Chong HK, Wang T, Lu HM, et al.
The validation and clinical implementation of BRCAplus: a comprehensive high-risk breast cancer diagnostic assay.
PLoS One. 2014; 9(5):e97408 [PubMed] Article available free on PMC after 15/11/2015 Related Publications
Breast cancer is the most commonly diagnosed cancer in women, with 10% of disease attributed to hereditary factors. Although BRCA1 and BRCA2 account for a high percentage of hereditary cases, there are more than 25 susceptibility genes that differentially impact the risk for breast cancer. Traditionally, germline testing for breast cancer was performed by Sanger dideoxy terminator sequencing in a reflexive manner, beginning with BRCA1 and BRCA2. The introduction of next-generation sequencing (NGS) has enabled the simultaneous testing of all genes implicated in breast cancer resulting in diagnostic labs offering large, comprehensive gene panels. However, some physicians prefer to only test for those genes in which established surveillance and treatment protocol exists. The NGS based BRCAplus test utilizes a custom tiled PCR based target enrichment design and bioinformatics pipeline coupled with array comparative genomic hybridization (aCGH) to identify mutations in the six high-risk genes: BRCA1, BRCA2, PTEN, TP53, CDH1, and STK11. Validation of the assay with 250 previously characterized samples resulted in 100% detection of 3,025 known variants and analytical specificity of 99.99%. Analysis of the clinical performance of the first 3,000 BRCAplus samples referred for testing revealed an average coverage greater than 9,000X per target base pair resulting in excellent specificity and the sensitivity to detect low level mosaicism and allele-drop out. The unique design of the assay enabled the detection of pathogenic mutations missed by previous testing. With the abundance of NGS diagnostic tests being released, it is essential that clinicians understand the advantages and limitations of different test designs.

Kaufman JM, Amann JM, Park K, et al.
LKB1 Loss induces characteristic patterns of gene expression in human tumors associated with NRF2 activation and attenuation of PI3K-AKT.
J Thorac Oncol. 2014; 9(6):794-804 [PubMed] Article available free on PMC after 15/11/2015 Related Publications
INTRODUCTION: Inactivation of serine/threonine kinase 11 (STK11 or LKB1) is common in lung cancer, and understanding the pathways and phenotypes altered as a consequence will aid the development of targeted therapeutic strategies. Gene and protein expressions in a murine model of v-Ki-ras2 Kirsten rat sarcoma viral oncogene homolog (Kras)-mutant lung cancer have been studied to gain insight into the biology of these tumors. However, the molecular consequences of LKB1 loss in human lung cancer have not been fully characterized.
METHODS: We studied gene expression profiles associated with LKB1 loss in resected lung adenocarcinomas, non-small-cell lung cancer cell lines, and murine tumors. The biological significance of dysregulated genes was interpreted using gene set enrichment and transcription factor analyses and also by integration with somatic mutations and proteomic data.
RESULTS: Loss of LKB1 is associated with consistent gene expression changes in resected human lung cancers and cell lines that differ substantially from the mouse model. Our analysis implicates novel biological features associated with LKB1 loss, including altered mitochondrial metabolism, activation of the nuclear respiratory factor 2 (NRF2) transcription factor by kelch-like ECH-associated protein 1 (KEAP1) mutations, and attenuation of the phosphatidylinositiol 3-kinase and v-akt murine thymoma viral oncogene homolog (PI3K/AKT) pathway. Furthermore, we derived a 16-gene classifier that accurately predicts LKB1 mutations and loss by nonmutational mechanisms. In vitro, transduction of LKB1 into LKB1-mutant cell lines results in attenuation of this signature.
CONCLUSION: Loss of LKB1 defines a subset of lung adenocarcinomas associated with characteristic molecular phenotypes and distinctive gene expression features. Studying these effects may improve our understanding of the biology of these tumors and lead to the identification of targeted treatment strategies.

Simbolo M, Mian C, Barollo S, et al.
High-throughput mutation profiling improves diagnostic stratification of sporadic medullary thyroid carcinomas.
Virchows Arch. 2014; 465(1):73-8 [PubMed] Related Publications
Sporadic medullary thyroid carcinoma (MTC) harbors RET gene somatic mutations in up to 50 % of cases, and RAS family gene mutations occur in about 10 %. A timely and comprehensive characterization of molecular alterations is needed to improve MTC diagnostic stratification and design-tailored therapeutic approaches. Twenty surgically resected sporadic MTCs, previously analyzed for RET mutations by Sanger sequencing using DNA from formalin-fixed paraffin-embedded samples, were investigated for intragenic mutations in 50 cancer-associated genes applying a multigene Ion AmpliSeq next-generation sequencing (NGS) technology. Thirteen (65 %) MTCs harbored a RET mutation; 10 were detected at both Sanger and NGS sequencing, while 3 undetected by Sanger were revealed by NGS. One of the 13 RET-mutated cases also showed an F354L germline mutation in STK11. Of the seven RET wild-type MTCs, four cases (57.1 %) harbored a RAS mutation: three in HRAS (all Q61R) and one in KRAS (G12R). The three remaining MTCs (15 %) resulted as wild-type for all the 50 cancer-related genes. Follow-up was available in all but one RET-mutated case. At the end of follow-up, 7 of 12 (58 %) RET-mutated patients had relapsed, while the 4 RAS-mutated MTC patients were disease-free. Two of the three patients with MTC wild-type for all 50 genes relapsed during the follow-up period. Detection of mutations by NGS has the potential to improve the diagnostic stratification of sporadic MTC.

Liu X, Mody K, de Abreu FB, et al.
Molecular profiling of appendiceal epithelial tumors using massively parallel sequencing to identify somatic mutations.
Clin Chem. 2014; 60(7):1004-11 [PubMed] Related Publications
BACKGROUND: Some epithelial neoplasms of the appendix, including low-grade appendiceal mucinous neoplasm and adenocarcinoma, can result in pseudomyxoma peritonei (PMP). Little is known about the mutational spectra of these tumor types and whether mutations may be of clinical significance with respect to therapeutic selection. In this study, we identified somatic mutations using the Ion Torrent AmpliSeq Cancer Hotspot Panel v2.
METHODS: Specimens consisted of 3 nonneoplastic retention cysts/mucocele, 15 low-grade mucinous neoplasms (LAMNs), 8 low-grade/well-differentiated mucinous adenocarcinomas with pseudomyxoma peritonei, and 12 adenocarcinomas with/without goblet cell/signet ring cell features. Barcoded libraries were prepared from up to 10 ng of extracted DNA and multiplexed on single 318 chips for sequencing. Data analysis was performed using Golden Helix SVS. Variants that remained after the analysis pipeline were individually interrogated using the Integrative Genomics Viewer.
RESULTS: A single Janus kinase 3 (JAK3) mutation was detected in the mucocele group. Eight mutations were identified in the V-Ki-ras2 Kirsten rat sarcoma viral oncogene homolog (KRAS) and GNAS complex locus (GNAS) genes among LAMN samples. Additional gene mutations were identified in the AKT1 (v-akt murine thymoma viral oncogene homolog 1), APC (adenomatous polyposis coli), JAK3, MET (met proto-oncogene), phosphatidylinositol-4,5-bisphosphate 3-kinase (PIK3CA), RB1 (retinoblastoma 1), STK11 (serine/threonine kinase 11), and tumor protein p53 (TP53) genes. Among the PMPs, 6 mutations were detected in the KRAS gene and also in the GNAS, TP53, and RB1 genes. Appendiceal cancers showed mutations in the APC, ATM (ataxia telangiectasia mutated), KRAS, IDH1 [isocitrate dehydrogenase 1 (NADP+)], NRAS [neuroblastoma RAS viral (v-ras) oncogene homolog], PIK3CA, SMAD4 (SMAD family member 4), and TP53 genes.
CONCLUSIONS: Our results suggest molecular heterogeneity among epithelial tumors of the appendix. Next generation sequencing efforts have identified mutational spectra in several subtypes of these tumors that may suggest a phenotypic heterogeneity showing mutations that are relevant for targeted therapies.

Okamoto I, Sakai K, Morita S, et al.
Multiplex genomic profiling of non-small cell lung cancers from the LETS phase III trial of first-line S-1/carboplatin versus paclitaxel/carboplatin: results of a West Japan Oncology Group study.
Oncotarget. 2014; 5(8):2293-304 [PubMed] Article available free on PMC after 15/11/2015 Related Publications
Archival formalin-fixed, paraffin-embedded (FFPE) tumor specimens were collected from advanced NSCLC patients enrolled in LETS phase III trial comparing first-line S-1/carboplatin with paclitaxel/carboplatin and subjected to multiplex genotyping for 214 somatic hotspot mutations in 26 genes (LungCarta Panel) and 20 major variants of ALK, RET, and ROS1 fusion genes (LungFusion Panel) with the Sequenom MassARRAY platform. MET amplification was evaluated by fluorescence in situ hybridization. A somatic mutation in at least one gene was identified in 48% of non-squamous cell carcinoma and 45% of squamous cell carcinoma specimens, with EGFR (17%), TP53 (11%), STK11 (9.8%), MET (7.6%), and KRAS (6.2%). Mutations in EGFR or KRAS were associated with a longer or shorter median overall survival, respectively. The LungFusion Panel identified ALK fusions in six cases (2.5%), ROS1 fusions in five cases (2.1%), and a RET fusion in one case (0.4%), with these three types of rearrangement being mutually exclusive. Nine (3.9%) of 229 patients were found to be positive for de novo MET amplification. This first multiplex genotyping of NSCLC associated with a phase III trial shows that MassARRAY-based genetic testing for somatic mutations and fusion genes performs well with nucleic acid derived from FFPE specimens of NSCLC tissue.

Zhang X, Chen H, Wang X, et al.
Expression and transcriptional profiling of the LKB1 tumor suppressor in cervical cancer cells.
Gynecol Oncol. 2014; 134(2):372-8 [PubMed] Related Publications
OBJECTIVES: To characterize the biological activities of LKB1, examine LKB1 protein expression and identify LKB1-regulated genes that may serve as therapeutic targets in cervical cancer.
METHODS: Proliferation of cervical cancer HeLa cells expressing LKB1 was examined. LKB1 expression in normal cervical tissues and cervical cancers was assessed by immunohistochemistry. Gene expression profiles of cervical cancer HeLa cells stably expressing LKB1 were analyzed by microarray. Differentially expressed genes were analyzed using Gene Ontology (GO) terms and the Kyoto Encyclopedia of Genes and Genomes (KEGG) PATHWAY database. Quantitative RT-PCR was used to validate the microarray data. The expression of lipid phosphatase inositol polyphosphate 4-phosphatase type II (INPP4B) was confirmed by western blotting.
RESULTS: Expression of LKB1 inhibited HeLa cell proliferation, activated AMPK and was lost in more than 50% of cervical carcinomas. More than 200 genes were differentially expressed between HeLa cells with and without LKB1. Bioinformatics analysis with GO annotation indicated that LKB1 plays a role in receiving diverse stimuli and converting them into molecular signals. KEGG PATHWAY analysis showed that 8 pathways were significantly regulated. These include arginine and proline metabolism and inositol phosphate metabolism. The differential expression of 7 randomly selected genes was confirmed by quantitative RT-PCR. Furthermore, the steady-state level of INPP4B protein was up-regulated in LKB1-overexpressing cells.
CONCLUSIONS: This study establishes LKB1 as an important tumor suppressor in cervical cancer and sheds light on a novel signaling pathway regulated by LKB1.

Goncharova EA, Goncharov DA, James ML, et al.
Folliculin controls lung alveolar enlargement and epithelial cell survival through E-cadherin, LKB1, and AMPK.
Cell Rep. 2014; 7(2):412-23 [PubMed] Article available free on PMC after 15/11/2015 Related Publications
Spontaneous pneumothoraces due to lung cyst rupture afflict patients with the rare disease Birt-Hogg-Dubé (BHD) syndrome, which is caused by mutations of the tumor suppressor gene folliculin (FLCN). The underlying mechanism of the lung manifestations in BHD is unclear. We show that BHD lungs exhibit increased alveolar epithelial cell apoptosis and that Flcn deletion in mouse lung epithelium leads to cell apoptosis, alveolar enlargement, and an impairment of both epithelial barrier and overall lung function. We find that Flcn-null epithelial cell apoptosis is the result of impaired AMPK activation and increased cleaved caspase-3. AMPK activator LKB1 and E-cadherin are downregulated by Flcn loss and restored by its expression. Correspondingly, Flcn-null cell survival is rescued by the AMPK activator AICAR or constitutively active AMPK. AICAR also improves lung condition of Flcn(f/f):SP-C-Cre mice. Our data suggest that lung cysts in BHD may result from an underlying defect in alveolar epithelial cell survival, attributable to FLCN regulation of the E-cadherin-LKB1-AMPK axis.

Wang YQ, Dai WM, Chu XY, et al.
Downregulation of LKB1 suppresses Stat3 activity to promote the proliferation of esophageal carcinoma cells.
Mol Med Rep. 2014; 9(6):2400-4 [PubMed] Related Publications
The tumor suppressor liver kinase B1 (LKB1) encodes a serine/threonine kinase. The defect in LKB1 is the primary cause of Peutz-Jeghers syndrome (PJS). Inactivation of LKB1 by mutations or loss of LKB1 expression is associated with ovarian, lung and pancreatic cancer; however, the correlation between LKB1 and esophageal carcinoma remains unknown. Thus, quantitative PCR was performed to determine the clinical significance of LKB1 expression in 60 cases of esophageal cancer and its adjacent normal epithelium. LKB1 expression was observed to significantly downregulate the accompanying cancer progression, which was verified at the protein level by western blot analysis. Furthermore, the phosphorylated signal transducer and activator of transcription 3 (Stat3) level is reversibly associated with LKB1 expression. To determine the function of LKB1 in esophageal cancer, LKB1 expression is induced in TE1 esophageal cancer cells. The results show that LKB1 overexpression suppresses the proliferation of TE1 cells, downregulates the expression of cyclin D1 and Myc and represses Stat3 phosphorylation. Suppression of cell proliferation and cyclin D1 expression by LKB1 is fully inhibited by constitutively active Stat3C coexpression, suggesting that LKB1 inhibits esophageal cancer cell proliferation through suppression of Stat3 transaction. In conclusion, downregulation of LKB1 expression suppresses Stat3 activity that may promote tumor growth during esophageal cancer progression.

Li L, Yu C, Ren J, et al.
Synergistic effects of eukaryotic coexpression plasmid carrying LKB1 and FUS1 genes on lung cancer in vitro and in vivo.
J Cancer Res Clin Oncol. 2014; 140(6):895-907 [PubMed] Related Publications
PURPOSE: LKB1 and FUS1 are two kinds of new tumor suppressor genes as well as early-stage genes in lung cancer. Recent studies showed that LKB1 and FUS1 play important roles in lung carcinogenesis process. We hypothesized that combined gene therapy with LKB1 and FUS1 could inhibit lung cancer growth and development synergistically.
METHODS: In this study, two kinds of tumor suppressor genes, LKB1 and FUS1, were constructed in an eukaryotic coexpression plasmid pVITRO(2), and then, we evaluated the synergistic effects of the two genes on anticancer activity and explored the relevant molecular mechanisms.
RESULTS: We defined coexpression of LKB1 and FUS1 could synergistically inhibited lung cancer cells growth,invasion and migration and induced the cell apoptosis and arrested cell cycle in vitro. Intratumoral administration of liposomes: pVITRO(2)–LKB1–FUS1 complex (LPs–pVITRO(2)–LKB1–FUS1) into subcutaneous lung tumor xenograft resulted in more significant inhibition of tumor growth. Furthermore, intravenous injection of LPs–pVITRO(2)–LKB1–FUS1 into mice bearing experimental A549 lung metastasis demonstrated synergistic decrease in the number of metastatic tumor nodules. Finally, combined treatment with LKB1 and FUS1 prolonged overall survival in lung tumor-bearing mice. Further study showed tha tthe synergistic anti-lung cancer effects of coexpression ofLKB1 and FUS1 might be related to upregulation of p-p53, p-AMPK and downregulation of p-mTOR, p-FAK, MMPs, NEDD9, VEGF/R and PDGF/R.
CONCLUSIONS: Our results suggest that combined therapy with eukaryotic coexpression plasmid carrying LKB1 and FUS1 genes may be a novel and efficient treatment strategy for human lung cancer.

Wang Z, Wu B, Mosig RA, et al.
STK11 domain XI mutations: candidate genetic drivers leading to the development of dysplastic polyps in Peutz-Jeghers syndrome.
Hum Mutat. 2014; 35(7):851-8 [PubMed] Related Publications
Peutz-Jeghers syndrome (PJS) is a rare hereditary disorder resulting from mutations in serine/threonine kinase 11 (STK11) and characterized by gastrointestinal (GI) hamartomatous polyps, mucocutaneous pigmentation, and an increased risk for specific cancers. Little is known about the genetic implications of specific STK11 mutations with regard to their role in dysplastic and malignant transformation of GI polyps. Peripheral blood genomic DNA samples from 116 Chinese PJS patients from 52 unrelated families were investigated for STK11 mutations. Genotype-phenotype correlations were investigated. The mutation detection rate was 67.3% (51.9% point mutations, 15.4% large deletions). Fourteen out of the 25 point mutations identified were novel. Nearly one-third of all mutations, 8/27 (29.6%), were in exon 7, the shortest out of the nine exons. Strikingly, mutations affecting protein kinase domain XI, encoded in part by exon 7, correlated with a 90% (9/10) incidence of GI polyp dysplasia. In contrast, only two out of 17 (11.8%) nondomain XI mutations were linked to polyp dysplasia (P = 0.0001). The extent of the association between dysplasia and the development of GI-related cancers is currently unknown but our results highlight a novel STK11 genotype-phenotype association as the basis for future genetic counseling and basic research studies.

Liang X, Li ZL, Jiang LL, et al.
Suppression of lung cancer cell invasion by LKB1 is due to the downregulation of tissue factor and vascular endothelial growth factor, partly dependent on SP1.
Int J Oncol. 2014; 44(6):1989-97 [PubMed] Related Publications
LKB1 encodes a serine/threonine kinase generally inactivated in many human cancers, which mediates cancer cell proliferation, migration and differentiation. Recent studies indicated that LKB1 exhibits potent anti-metastatic activity. However, the underlying molecular mechanisms of this activity remain unclear. In this study, we re‑introduced LKB1 into A549 lung cancer cells that lack the LKB1 gene to investigate how LKB1 affects tumor invasiveness and metastasis. We demonstrated that overexpression of the LKB1 protein in lung cancer cells resulted in significant inhibition of invasion. Furthermore, transfected lung cancer cells with LKB1 suppressed tissue factor (TF) and vascular endothelial growth factor (VEGF) expression at both the mRNA and protein levels. Here, we provided evidence showing that downregulation of TF and VEGF by LKB1 is correlated well with the inhibition of cell invasion. Overexpression of the LKB1 protein in human lung cancer is significantly associated with a decrease in activity and expression of the transcription factor SP1. Constitutive activation of the transcription factor Sp1 plays a critical role in TF and VEGF overexpression. We conclude that suppression of lung cancer cell invasion by LKB1 through downregulation of TF and VEGF may partly depend on its inhibitory effect on the transcription factor Sp1. Collectively, our data provide a novel molecular mechanism for the antitumor activity of LKB1 and may help further improve its effectiveness in controlling lung cancer growth and invasion.

Dai L, Fu L, Liu D, et al.
Novel and recurrent mutations of STK11 gene in six Chinese cases with Peutz-Jeghers syndrome.
Dig Dis Sci. 2014; 59(8):1856-61 [PubMed] Related Publications
BACKGROUND: The serine/threonine kinase 11 (STK11) gene is the main causal gene in Peutz-Jeghers syndrome (PJS). Abnormal STK11 may increase cancer risk of PJS patients via affecting its target proteins such as P53, AMPK, and PTEN. In this study, we investigated the molecular basis of six Chinese PJS patients.
MATERIALS AND METHODS: Blood samples were collected from four Chinese PJS families and two sporadic patients. The entire coding region of the STK11 gene was amplified by polymerase chain reaction and analyzed by direct sequencing. Functions of mutants were assessed by PolyPhen-2, Swiss-Model software, and luciferase reporter assay.
RESULTS: Novel mutations (c.842_843insC, c.804_805insG, and c.922T>G) and recurrent mutations (c.526G>A, c.180C>G, and c.1062C>G) were identified. Missense mutation c.922T>G and c.526G>A were predicted as probably damaging by PolyPhen-2, while c.1062C>G was benign. Mutation c.108C>G was a nonsense mutation. The 284Ter mutants of c.842_843insC and c.804_805insG significantly diminished the capacity of P53 activity in 293FT cells.
CONCLUSIONS: Our results support that STK11 gene mutations underlie Chinese patients with PJS. Mutation involving partial kinase domain disrupts normal function of STK11. Our results also enlarge the spectrum of STK11 variants in PJS patients.

Javle M, Rashid A, Churi C, et al.
Molecular characterization of gallbladder cancer using somatic mutation profiling.
Hum Pathol. 2014; 45(4):701-8 [PubMed] Related Publications
Gallbladder cancer is relatively uncommon, with a high incidence in certain geographic locations, including Latin America, East and South Asia, and Eastern Europe. Molecular characterization of this disease has been limited, and targeted therapy options for advanced disease remain an open area of investigation. In the present study, surgical pathology obtained from resected gallbladder cancer cases (n = 72) was examined for the presence of targetable, somatic mutations. All cases were formalin fixed and paraffin embedded (FFPE). Two approaches were used: (a) mass spectroscopy-based profiling for 159 point ("hot spot") mutations in 33 genes commonly involved in solid tumors and (b) next-generation sequencing (NGS) platform that examined the complete coding sequence of in 182 cancer-related genes. Fifty-seven cases were analyzed for hot spot mutations; and 15, for NGS. Fourteen hot spot mutations were identified in 9 cases. Of these, KRAS mutation was significantly associated with poor survival on multivariate analysis. Other targetable mutations included PIK3CA (n = 2) and ALK (n = 1). On NGS, 26 mutations were noted in 15 cases. TP53 and PI3 kinase pathway (STK11, RICTOR, TSC2) mutations were common. One case had FGF10 amplification, whereas another had FGF3-TACC gene fusion, not previously described in gallbladder cancer. In conclusion, somatic mutation profiling using archival FFPE samples from gallbladder cancer is feasible. NGS, in particular, may be a useful platform for identifying novel mutations for targeted therapy.

Pradella LM, Evangelisti C, Ligorio C, et al.
A novel deleterious PTEN mutation in a patient with early-onset bilateral breast cancer.
BMC Cancer. 2014; 14:70 [PubMed] Article available free on PMC after 15/11/2015 Related Publications
BACKGROUND: An early age at Breast Cancer (BC) onset may be a hallmark of inherited predisposition, but BRCA1/2 mutations are only found in a minority of younger BC patients. Among the others, a fraction may carry mutations in rarer BC genes, such as TP53, STK11, CDH1 and PTEN. As the identification of women harboring such mutations allows for targeted risk-management, the knowledge of associated manifestations and an accurate clinical and family history evaluation are warranted.
CASE PRESENTATION: We describe the case of a woman who developed an infiltrating ductal carcinoma of the right breast at the age of 32, a contralateral BC at age 36 and another BC of the right breast at 40. When she was 39 years-old, during a dermatological examination, mucocutaneous features suggestive of Cowden Syndrome, a disorder associated to germ-line PTEN mutations, were noticed. PTEN genetic testing revealed the novel c.71A > T (p.Asp24Val) mutation, whose deleterious effect, suggested by conservation data and in silico tools, was definitely demonstrated by the incapacity of mutant PTEN to inhibit Akt phosphorylation when used to complement PTEN-null cells. In BC tissue, despite the absence of LOH or somatic mutations of PTEN, Akt phosphorylation was markedly increased in comparison to normal tissue, thus implying additional somatic events into the deregulation of the PI3K/Akt/mTOR pathway and, presumably, into carcinogenesis. Hence, known oncogenic mutations in PIK3CA (exons 10 and 21) and AKT1 (exon 2) were screened in tumor DNA with negative results, which suggests that the responsible somatic event(s) is a different, uncommon one.
CONCLUSION: This case stresses the importance of clinical/genetic assessment of early-onset BC patients in order to identify mutation carriers, who are at high risk of new events, so requiring tailored management. Moreover, it revealed a novel PTEN mutation with pathogenic effect, pointing out, however, the need for further efforts to elucidate the molecular steps of PTEN-associated carcinogenesis.

Kobayashi Y, Masuda K, Kimura T, et al.
A tumor of the uterine cervix with a complex histology in a Peutz-Jeghers syndrome patient with genomic deletion of the STK11 exon 1 region.
Future Oncol. 2014; 10(2):171-7 [PubMed] Related Publications
Patients with Peutz-Jeghers syndrome (PJS) have a risk of complicating malignant tumors, including cancer of the uterine cervix. Mutations in the STK11 gene have been identified as being responsible for PJS. However, the genotype-phenotype correlation in PJS is poorly understood, especially with respect to malignant tumors. Here, we report a detailed analysis of a case of a cervical tumor in a PJS patient showing a large genomic deletion in exon 1 of STK11 without human papillomavirus infection. Histological examination revealed a complex histology consisting of three components: lobular endocervical gland hyperplasia (LEGH), minimal deviation adenocarcinoma (MDA) and mucinous adenocarcinoma. Immunohistochemistry for STK11 was positive in the LEGH and MDA components, while that of the mucinous adenocarcinoma stained very faintly. These findings support a close relationship among LEGH, MDA and mucinous adenocarcinoma and imply that inactivation of STK11 may occur during progression from MDA to mucinous adenocarcinoma.

Tan DS, Camilleri-Broët S, Tan EH, et al.
Intertumor heterogeneity of non-small-cell lung carcinomas revealed by multiplexed mutation profiling and integrative genomics.
Int J Cancer. 2014; 135(5):1092-100 [PubMed] Related Publications
Non-small-cell lung cancer (NSCLC) is a heterogeneous disease, with a burden of genomic alterations exceeding most other tumors. The goal of our study was to evaluate the frequencies of co-occurring mutations and copy-number aberrations (CNAs) within the same tumor and to evaluate their potential clinical impact. Mass-spectrometry based mutation profiling using a customized lung cancer panel evaluating 214 mutations across 26 key NSCLC genes was performed on 230 nonsquamous NSCLC and integrated with genome-wide CNAs and clinical variables. Among the 138 cases having at least one mutation, one-third (41, 29.7%) showed two or more mutations, either in the same gene (double mutation) or in different genes (co-mutations). In epidermal growth factor receptor (EGFR) mutant cancers, there was a double mutation in 18% and co-mutations in the following genes: TP53 (10%), PIK3CA (8%), STK11 (6%) and MET (4%). Significant relationships were detected between EGFR mutation and 1p, 7p copy gains (harboring the EGFR gene) as well as 13q copy loss. KRAS mutation was significantly related with 1q gain and 3q loss. For Stage I, tumors harboring at least one mutation or PIK3CA mutation were significantly correlated with poor prognosis (p-value = 0.02). When combining CNAs and mutational status, patients having both KRAS mutation and the highest related CNA (3q22.3 copy loss) showed a significant poorer prognosis (p-value = 0.03). Our study highlights the clinical relevance of studying tumor complexity by integrative genomic analysis and the need for developing assays that broadly screen for both "actionable" mutations and copy-number alterations to improve precision of stratified treatment approaches.

Gong F, Liu H, Li J, et al.
Peroxiredoxin 1 is involved in disassembly of flagella and cilia.
Biochem Biophys Res Commun. 2014; 444(3):420-6 [PubMed] Related Publications
Cilia/flagella are evolutionarily conserved cellular organelles. In this study, we demonstrated that Dunaliella salina Peroxiredoxin 1 (DsPrdx1) localized to the flagella and basal bodies, and was involved in flagellar disassembly. The link between DsPrdx1 and flagella of Dunaliella salina (D. salina) encouraged us to explore the function of its human homologue, Homo sapiens Peroxiredoxin 1 (HsPrdx1) in development and physiology. Our results showed that HsPrdx1 was overexpressed, and cilia were lost in esophageal squamous cell carcinoma (ESCC) cells compared with the non-cancerous esophageal epithelial cells Het-1A. Furthermore, when HsPrdx1 was knocked down by short hairpin RNA (shRNA) lentivirus in ESCC cells, the phenotype of cilia lost can be reversed, and the expression levels of tumor suppressor genes LKB1 and p-AMPK were increased, and the activity of the oncogene Aurora A was inhibited compared with those in cells transfected with scrambe-shRNA lentivirus. These findings firstly showed that Prdx1 is involved in disassembly of flagella and cilia, and suggested that the abnormal expression of the cilia-related gene including Prdx1 may affect both ciliogenesis and cancernogenesis.

Kim HR, Cho BC, Shim HS, et al.
Prediction for response duration to epidermal growth factor receptor-tyrosine kinase inhibitors in EGFR mutated never smoker lung adenocarcinoma.
Lung Cancer. 2014; 83(3):374-82 [PubMed] Related Publications
OBJECTIVES: Among non-small cell lung cancer (NSCLC) patients harboring activating epidermal growth factor receptor (EGFR) mutations, ∼ 20-30% exhibit de novo resistance to EGFR-tyrosine kinase inhibitor (TKI). The aim of this study was to examine whether mutations in the EGFR-downstream genes may be associated with de novo resistance to EGFR-TKIs in EGFR mutation-positive patients.
MATERIALS AND METHODS: Sixty-eight never-smoker adenocarcinoma patients with an activating EGFR mutation were included in the mutational analysis and 55 patients treated with EGFR-TKIs were analyzed for the treatment outcomes to EGFR-TKIs. We concurrently analyzed mutations in PIK3CA, PTEN, AKT and STK11, which are all EGFR-downstream genes. Mutations in PIK3CA, PTEN, AKT, and STK11 were analyzed by polymerase chain reaction-based sequencing.
RESULTS: PIK3CA mutations were detected in 4.4% (3/68) of patients, PTEN mutations in 16.1% (11/68), AKT mutations in 5.9% (4/68), and STK11 mutations in 13.2% (9/68). One patient with an activating exon 21 L858R mutation concomitantly had an exon 20 T790M mutation in EGFR. The proportion of patients who had mutations in EGFR-downstream genes was 32.4% (22/68). When we analyzed the treatment outcome of 55 patients treated with EGFR-TKI, the presence of mutations in EGFR-downstream genes correlated with a poor overall response rate to EGFR-TKIs (63.6 vs.14.5% in patients with mutation in EGFR-downstream gene, P<0.0001), shorter median progression-free survival (12.0 vs. 3.0 months, P=0.060), and shorter median overall survival (18.9 vs. 25.0 months, P=0.048).
CONCLUSION: Mutations in the EGFR-downstream genes may confer resistance to EGFR-TKIs and result in poor treatment outcomes in never-smoker adenocarcinoma patients with activating EGFR mutations.

Richetta AG, Silvestri V, Giancristoforo S, et al.
Mutational profiling in melanocytic tumors: multiple somatic mutations and clinical implications.
Oncology. 2014; 86(2):104-8 [PubMed] Related Publications
In this study, we analyzed multiple somatic mutations in 10 genes relevant in melanoma tumorigenesis and targeted therapies. Overall, 45% of the tumors showed mutations and, in particular, 33% had multiple mutations. Based on our results, we conclude that the assessment of mutation status of multiple genes, including CDKN2A, could provide a genetic profile that can be useful as a prognostic and therapeutic marker in melanocytic tumors.

Jian SF, Hsiao CC, Chen SY, et al.
Utilization of liquid chromatography mass spectrometry analyses to identify LKB1-APC interaction in modulating Wnt/β-catenin pathway of lung cancer cells.
Mol Cancer Res. 2014; 12(4):622-35 [PubMed] Related Publications
UNLABELLED: STK11/LKB1, a serine/threonine protein kinase and tumor suppressor, is a key upstream kinase of adenine monophosphate-activated protein kinase, which is a kinase involved in controlling cell polarity and maintaining cellular energy homeostasis. LKB1 is mutated in a significant number of Peutz-Jeghers syndrome (PJS) cases and sporadic cancers, and is most frequently mutated in lung adenocarcinomas; however, little is known about how LKB1 is involved in lung cancer progression. In this study, immunoprecipitation-HPLC tandem mass spectrometry (IP-LC-MS/MS) was performed to identify novel proteins interacting with LKB1 in lung cancer. Interestingly, many LKB1-interacting proteins acquired from the LC-MS/MS approach were mapped, using MetaCore pathway analysis, to the cystic fibrosis transmembrane conductance regulator activation pathway. Moreover, it was determined that LKB1 directly interacts with APC, and this LKB1-APC interaction was further confirmed by reverse immunoprecipitation assays, but GSK3β was dispensable for the association of LKB1 and APC. Importantly, LKB1 binds to APC to suppress the Wnt/β-catenin signaling pathway, which is known to be involved in cell proliferation and migration. Subsequent analysis of the downstream targets of the Wnt/TCF pathway led to the identification of several Wnt-regulated genes, such as CD44, COX-2, survivin, and c-Myc, whose expression levels are downregulated by LKB1. In summary, these results demonstrate that LKB1 regulates the Wnt pathway through a direct interaction with APC to suppress the tumorigenic/metastatic potential of lung tumors.
IMPLICATIONS: LKB1 status influences the molecular circuitry (Wnt/β-catenin pathway), cellular biology, and may serve as a potential therapeutic node in genetically defined subsets of lung cancer.

Fang R, Zheng C, Sun Y, et al.
Integrative genomic analysis reveals a high frequency of LKB1 genetic alteration in Chinese lung adenocarcinomas.
J Thorac Oncol. 2014; 9(2):254-8 [PubMed] Related Publications
Liver kinase B1 (LKB1) genetic alteration in lung cancer involves not only point mutations and small deletion of several base pairs but also exonic loss. However, most of recent studies in LKB1 gene status only focus on point mutations and small deletion, and thus may underestimate the actual frequency of LKB1 genetic alteration in lung cancer. Thus, an integrative analysis of LKB1 genetic alteration is timely and important for providing a better estimate for the incidence of genetic alterations in this important tumor suppressor gene. One hundred and seven lung adenocarcinomas with more than 70% tumor have been analyzed for mutation of LKB1 as well as LKB1 large deletions detection by using multiplex ligation-dependent probe amplification analysis. These samples were also analyzed for EGFR, KRAS, HER2, BRAF, ALK, ROS1, and RET status in stepwise method. Among 107 lung adenocarcinomas analyzed, 29 (27.1%) harbored LKB1 genetic alteration. Twenty-three (21.5%) harbored LKB1 large exonic deletions and eight (7.48%) had LKB1 points mutations, two samples harbored both LKB1 large exonic deletions and point mutations. Eighty-seven samples (81.31%) harbored known driver mutations and 20 samples (18.69%) had no identifiable driver mutations. A high rate of LKB1 genetic alteration in Chinese lung adenocarcinomas is revealed by the integrative analysis of point mutation and exonic deletion. Moreover, LKB1 genetic alterations are concurrent with EGFR, KRAS, HER2, and CD74-ROS fusions.

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