Gene Summary

Gene:AXL; AXL receptor tyrosine kinase
Aliases: ARK, UFO, JTK11, Tyro7
Summary:The protein encoded by this gene is a member of the Tyro3-Axl-Mer (TAM) receptor tyrosine kinase subfamily. The encoded protein possesses an extracellular domain which is composed of two immunoglobulin-like motifs at the N-terminal, followed by two fibronectin type-III motifs. It transduces signals from the extracellular matrix into the cytoplasm by binding to the vitamin K-dependent protein growth arrest-specific 6 (Gas6). This gene may be involved in several cellular functions including growth, migration, aggregation and anti-inflammation in multiple cell types. Alternative splicing results in multiple transcript variants of this gene. [provided by RefSeq, Jul 2013]
Databases:OMIM, VEGA, HGNC, Ensembl, GeneCard, Gene
Protein:tyrosine-protein kinase receptor UFO
Source:NCBIAccessed: 16 March, 2015


What does this gene/protein do?
Show (39)

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.

  • MicroRNAs
  • AXL
  • Quinazolines
  • Epidermal Growth Factor Receptor
  • Vascular Endothelial Growth Factor Receptor-2
  • Intercellular Signaling Peptides and Proteins
  • Phosphorylation
  • Proto-Oncogene Proteins
  • Base Sequence
  • Neoplasm Metastasis
  • Adenocarcinoma
  • Immunohistochemistry
  • Cancer Gene Expression Regulation
  • Translational Medical Research
  • Apoptosis
  • Gene Expression Profiling
  • Neoplasm Invasiveness
  • Epithelial-Mesenchymal Transition
  • Promoter Regions
  • Messenger RNA
  • Oncogene Proteins
  • c-MET
  • Mutation
  • Breast Cancer
  • Cell Movement
  • Chromosome 19
  • Western Blotting
  • Oligonucleotide Array Sequence Analysis
  • Non-Small Cell Lung Cancer
  • siRNA
  • Drug Resistance
  • Protein Kinase Inhibitors
  • Platelet-Derived Growth Factor Receptors
  • Cell Proliferation
  • Cell Survival
  • Thyroid Cancer
  • Molecular Sequence Data
  • Gene Expression
  • Antineoplastic Agents
  • Lung Cancer
  • Neoplastic Cell Transformation
Tag cloud generated 16 March, 2015 using data from PubMed, MeSH and CancerIndex

Specific Cancers (4)

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

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

Latest Publications: AXL (cancer-related)

Li M, Lu J, Zhang F, et al.
Yes-associated protein 1 (YAP1) promotes human gallbladder tumor growth via activation of the AXL/MAPK pathway.
Cancer Lett. 2014; 355(2):201-9 [PubMed] Related Publications
The transcriptional coactivator Yes-associated protein 1 (YAP1), a key regulator of cell proliferation and organ size in vertebrates, has been implicated in various malignancies. However, little is known about the expression and biological function of YAP1 in human gallbladder cancer (GBC). In this study we examined the clinical significance and biological functions of YAP1 in GBC and found that nuclear YAP1 and its target gene AXL were overexpressed in GBC tissues. We also observed a significant correlation between high YAP1 and AXL expression levels and worse prognosis. The depletion of YAP1 using lentivirus shRNAs significantly inhibited cell proliferation by inducing cell cycle arrest in S phase in concordance with the decrease of CDK2, CDC25A, and cyclin A, and resulted in increased cell apoptosis and invasive repression in GBC cell lines in vitro. Furthermore, knockdown of YAP1 also inhibited tumor growth in vivo. Additionally, we demonstrated that the activation of the AXL/MAPK pathway was involved in the oncogenic functions of YAP1 in GBC. These results demonstrated that YAP1 is a putative oncogene and represents a prognostic marker and potentially a novel therapeutic target for GBC.

Nguyen KQ, Tsou WI, Calarese DA, et al.
Overexpression of MERTK receptor tyrosine kinase in epithelial cancer cells drives efferocytosis in a gain-of-function capacity.
J Biol Chem. 2014; 289(37):25737-49 [PubMed] Article available free on PMC after 12/09/2015 Related Publications
MERTK, a member of the TAM (TYRO3, AXL, and MERTK) receptor tyrosine kinases, has complex and diverse roles in cell biology. On the one hand, knock-out of MERTK results in age-dependent autoimmunity characterized by failure of apoptotic cell clearance, while on the other, MERTK overexpression in cancer drives classical oncogene pathways leading to cell transformation. To better understand the interplay between cell transformation and efferocytosis, we stably expressed MERTK in human MCF10A cells, a non-tumorigenic breast epithelial cell line devoid of endogenous MERTK. While stable expression of MERTK in MCF10A resulted in enhanced motility and AKT-mediated chemoprotection, MERTK-10A cells did not form stable colonies in soft agar, or enhance proliferation compared with parental MCF10A cells. Concomitant to chemoresistance, MERTK also stimulated efferocytosis in a gain-of-function capacity. However, unlike AXL, MERTK activation was highly dependent on apoptotic cells, suggesting MERTK may preferentially interface with phosphatidylserine. Consistent with this idea, knockdown of MERTK in breast cancer cells MDA-MB 231 reduced efferocytosis, while transient or stable expression of MERTK stimulated apoptotic cell clearance in all cell lines tested. Moreover, human breast cancer cells with higher endogenous MERTK showed higher levels of efferocytosis that could be blocked by soluble TAM receptors. Finally, through MERTK, apoptotic cells induced PD-L1 expression, an immune checkpoint blockade, suggesting that cancer cells may adopt MERTK-driven efferocytosis as an immune suppression mechanism for their advantage. These data collectively identify MERTK as a significant link between cancer progression and efferocytosis, and a potentially unrealized tumor-promoting event when MERTK is overexpressed in epithelial cells.

Letelier P, García P, Leal P, et al.
miR-1 and miR-145 act as tumor suppressor microRNAs in gallbladder cancer.
Int J Clin Exp Pathol. 2014; 7(5):1849-67 [PubMed] Article available free on PMC after 12/09/2015 Related Publications
The development of miRNA-based therapeutics represents a new strategy in cancer treatment. The objectives of this study were to evaluate the differential expression of microRNAs in gallbladder cancer (GBC) and to assess the functional role of miR-1 and miR-145 in GBC cell behavior. A profile of miRNA expression was determined using DharmaconTM microarray technology. Differential expression of five microRNAs was validated by TaqMan reverse transcription quantitative-PCR in a separate cohort of 8 tumors and 3 non-cancerous samples. Then, we explored the functional role of miR-1 and miR-145 in tumor cell behavior by ectopic in vitro expression in the GBC NOZ cell line. Several miRNAs were found to be aberrantly expressed in GBC; most of these showed a significantly decreased expression compared to non-neoplastic tissues (Q value<0.05). The differential expression of 7 selected miRNAs was confirmed by real time PCR. Pathway enrichment analysis revealed that the most deregulated miRNAs (miR-1, miR-133, miR-143 and miR-145) collectively targeted a number of genes belonging to signaling pathways such as TGF-β, ErbB3, WNT and VEGF, and those regulating cell motility or adhesion. The ectopic expression of miR-1 and miR-145 in NOZ cells significantly inhibited cell viability and colony formation (P<0.01) and reduced gene expression of VEGF-A and AXL. This study represents the first investigation of the miRNA expression profile in gallbladder cancer, and our findings showed that several miRNAs are deregulated in this neoplasm. In vitro functional assays suggest that miR-1 and miR-145 act as tumor suppressor microRNAs in GBC.

Ren D, Li Y, Gong Y, et al.
Phyllodes tumor of the breast: role of Axl and ST6GalNAcII in the development of mammary phyllodes tumors.
Tumour Biol. 2014; 35(10):9603-12 [PubMed] Related Publications
Phyllodes tumor exhibits an aggressive growth. The expression of many biological markers has been explored to discriminate between different grades of phyllodes tumor and to predict their behavior. The purpose of this study was to evaluate the implications of Axl and ST6GalNAcII in phyllodes tumors. Real-time PCR, Western blot, and immunohistochemical were used to analyze differential expression of ST6GalNAcII and Axl in phyllodes tumor (PT) cell lines and tissue specimens. RNAi assay, ECM invasion assay, and tumorigenicity assay were used to analyze the altered expression of ST6GalNAcII gene effects on the expression of Axl and invasive ability of phyllodes tumor cells in vitro and in vivo. Compared to benign tumors, borderline and malignant ones showed a remarkable increase in mRNA levels of Axl and ST6GalNAcII gene, and it was higher in malignant tumor cells than in borderline tumor cells. When ST6GalNAcII was silenced, compared to the control, the expression level of Axl was significantly reduced in malignant tumor cell transfectants and knockdown of ST6GalNAcII gene significantly inhibited invasive activity in malignant tumor cells. The high expression of ST6GalNAcII and Axl was significantly correlated with tumor grade and distance metastasis by immunohistochemical analysis. Axl and ST6GalNAcII expression increases with increasing tumor grade in mammary phyllodes tumors. ST6GalNAc II might be participated in the glycosylation of Axl, and this Axl glycosylation may mediate the tumorigenicity, invasion, and distant metastasis of PT cells.

Kim KC, Choi EH, Lee C
Axl receptor tyrosine kinase is a novel target of apigenin for the inhibition of cell proliferation.
Int J Mol Med. 2014; 34(2):592-8 [PubMed] Related Publications
The Axl receptor tyrosine kinase (RTK), along with Tyro 3 and Mer, belongs to the TAM subfamily that promotes survival, stimulates proliferation and/or inhibits apoptosis. In various types of human cancer, including breast, lung and prostate cancer, Axl expression is increased and correlates with an advanced clinical stage. In this study, we examined whether apigenin has an effect on Axl expression, which in turn can affect cell proliferation. The treatment of the non‑small cell lung cancer (NSCLC) cells, A549 and H460, with apigenin decreased Axl mRNA and protein expression in a dose‑dependent manner. Axl promoter activity was also inhibited by apigenin, indicating that apigenin suppressed Axl expression at the transcriptional level. Upon treatment with apigenin, the viability of both the A549 and H460 cells was gradually decreased and the anti-proliferative effects were further confirmed by the dose‑dependent decrease in the clonogenic ability of the apigenin‑treated cells. Subsequently, we found that the viability and clonogenic ability of the cells treated with apigenin was less or more affected by transfection of the cells with a Axl-expressing plasmid or Axl targeting siRNA, compared to transfection with the empty vector or control siRNA, respectively. In addition, apigenin increased the expression of p21, a cyclin-dependent kinase inhibitor, but reduced the expression of X-linked inhibitor of apoptosis protein (XIAP). These cell cycle arrest and pro-apoptotic effects of apigenin were also attenuated or augmented by the up- or downregulation of Axl expression, respectively, which suggests that Axl is a novel target of apigenin through which it exerts its inhibitory effects on cell proliferation. Taken together, our data indicate that apigenin downregulates Axl expression, which subsequently results in the inhibition of NSCLC cell proliferation through the increase and decrease of p21 and XIAP expression, respectively.

Rettew AN, Getty PJ, Greenfield EM
Receptor tyrosine kinases in osteosarcoma: not just the usual suspects.
Adv Exp Med Biol. 2014; 804:47-66 [PubMed] Related Publications
Despite aggressive surgical and chemotherapy protocols, survival rates for osteosarcoma patients have not improved over the last 30 years. Therefore, novel therapeutic agents are needed. Receptor tyrosine kinases have emerged as targets for the development of new cancer therapies since their activation leads to enhanced proliferation, survival, and metastasis. In fact, aberrant expression and activation of RTKs have been associated with the progression of many cancers. Studies from our lab using phosphoproteomic screening identified RTKs that are activated and thus may contribute to the signaling within metastatic human osteosarcoma cells. Functional genomic screening using siRNA was performed to distinguish which of the activated RTKs contribute to in vitro phenotypes associated with metastatic potential (motility, invasion, colony formation, and cell growth). The resulting RTK hits were then validated using independent validation experiments. From these results, we identified four RTKs (Axl, EphB2, FGFR2, and Ret) that have not been previously studied in osteosarcoma and provide targets for the development of novel therapeutics.

D'Alfonso TM, Hannah J, Chen Z, et al.
Axl receptor tyrosine kinase expression in breast cancer.
J Clin Pathol. 2014; 67(8):690-6 [PubMed] Related Publications
AIMS: Triple-negative breast cancer comprises a clinically aggressive group of invasive carcinomas. We examined a published gene expression screen of a panel of breast cancer cell lines to identify a potential triple-negative breast cancer-specific gene signature, and attempted to verify our findings by performing immunohistochemical analysis on tissue microarrays containing a large cohort of invasive breast carcinomas.
METHODS: The microarray dataset for a panel of human breast cancer cell lines was interrogated for triple-negative breast cancer-specific genes. Membranous immunohistochemical expression of the protein product of the AXL gene was assessed semiquantitatively in 569 invasive breast carcinomas grouped according to molecular subgroup by immunohistochemistry.
RESULTS: AXL was significantly upregulated in triple-negative/basal B cell lines compared with luminal or basal A cell lines. No significant difference was observed in the level of immunohistochemical expression of Axl protein between triple-negative breast cancers and other molecular subgroups (p=0.257). Axl expression was significantly associated with lymphovascular invasion (LVI) in all subgroups combined (p=0.033), and within the luminal A (p=0.002) and triple-negative breast cancer subgroups (p=0.026).
CONCLUSIONS: Despite preferential upregulation of AXL in triple-negative/basal B cell lines, analysis of Axl protein expression in a large series of patients' breast tumours revealed no association between Axl expression and triple-negative breast cancer or other subtype. The association of Axl expression with LVI supports previous work that implicates Axl as a promoter of invasiveness in breast cancer cell lines. Further studies are necessary to explore whether Axl expression of individual breast cancer tumours can be clinically useful.

Wang Y, Xia H, Zhuang Z, et al.
Axl-altered microRNAs regulate tumorigenicity and gefitinib resistance in lung cancer.
Cell Death Dis. 2014; 5:e1227 [PubMed] Article available free on PMC after 12/09/2015 Related Publications
The involvement of Axl kinase in non-small cell lung cancer's (NSCLC) acquired resistance to tyrosine kinase inhibitors (TKIs) gefitinib or erlotinib has been identified recently, but the mechanism by which Axl contributes to TKI resistance is largely unknown. MicroRNAs (miRNAs) repress gene expression and their critical role in tumorigenesis has been implicated. To investigate the role of miRNAs in the Axl-mediated acquired gefitinib resistance, we examined the Axl-mediated miRNA changes in gefitinib-resistant lung cancers. A panel of Axl kinase-altered miRNAs was identified. In this study, we validate and report that miR-374a and miR-548b modulated by Axl have essential roles in cell cycle arrest, gefitinib-induced apoptosis, epithelial-to-mesenchymal transition, migration and tumorigenesis of gefitinib-resistant lung cancer cells in vitro and in vivo by targeting Wnt5a and CCNB1 genes, respectively. Of clinical significance, high expression of Axl and miR-374a and low expression of miR-548b are associated with poor disease-free survival postoperatively. These findings indicate that the modulation of specific miRNAs may provide a therapeutic target to treat or reverse gefitinib resistance in NSCLC with high expression of Axl in the future.

Konieczkowski DJ, Johannessen CM, Abudayyeh O, et al.
A melanoma cell state distinction influences sensitivity to MAPK pathway inhibitors.
Cancer Discov. 2014; 4(7):816-27 [PubMed] Article available free on PMC after 12/09/2015 Related Publications
UNLABELLED: Most melanomas harbor oncogenic BRAF(V600) mutations, which constitutively activate the MAPK pathway. Although MAPK pathway inhibitors show clinical benefit in BRAF(V600)-mutant melanoma, it remains incompletely understood why 10% to 20% of patients fail to respond. Here, we show that RAF inhibitor-sensitive and inhibitor-resistant BRAF(V600)-mutant melanomas display distinct transcriptional profiles. Whereas most drug-sensitive cell lines and patient biopsies showed high expression and activity of the melanocytic lineage transcription factor MITF, intrinsically resistant cell lines and biopsies displayed low MITF expression but higher levels of NF-κB signaling and the receptor tyrosine kinase AXL. In vitro, these MITF-low/NF-κB-high melanomas were resistant to inhibition of RAF and MEK, singly or in combination, and ERK. Moreover, in cell lines, NF-κB activation antagonized MITF expression and induced both resistance marker genes and drug resistance. Thus, distinct cell states characterized by MITF or NF-κB activity may influence intrinsic resistance to MAPK pathway inhibitors in BRAF(V600)-mutant melanoma.
SIGNIFICANCE: Although most BRAF(V600)-mutant melanomas are sensitive to RAF and/or MEK inhibitors, a subset fails to respond to such treatment. This study characterizes a transcriptional cell state distinction linked to MITF and NF-κB that may modulate intrinsic sensitivity of melanomas to MAPK pathway inhibitors.

Suda K, Mizuuchi H, Sato K, et al.
The insulin-like growth factor 1 receptor causes acquired resistance to erlotinib in lung cancer cells with the wild-type epidermal growth factor receptor.
Int J Cancer. 2014; 135(4):1002-6 [PubMed] Related Publications
Epidermal growth factor receptor (EGFR)-tyrosine kinase inhibitor (TKI) therapy often provides a dramatic response in lung cancer patients with EGFR mutations. In addition, moderate clinical efficacy of the EGFR-TKI, erlotinib, has been shown in lung cancer patients with the wild-type EGFR. Numerous molecular mechanisms that cause acquired resistance to EGFR-TKIs have been identified in lung cancers with the EGFR mutations; however, few have been reported in lung cancers with the wild-type EGFR. We used H358 lung adenocarcinoma cells lacking EGFR mutations that showed modest sensitivity to erlotinib. The H358 cells acquired resistance to erlotinib via chronic exposure to the drug. The H358 erlotinib-resistant (ER) cells do not have a secondary EGFR mutation, neither MET gene amplification nor PTEN downregulation; these have been identified in lung cancers with the EGFR mutations. From comprehensive screening of receptor tyrosine kinase phosphorylation, we observed increased phosphorylation of insulin-like growth factor 1 receptor (IGF1R) in H358ER cells compared with parental H358 cells. H358ER cells responded to combined therapy with erlotinib and NVP-AEW541, an IGF1R-TKI. Our results indicate that IGF1R activation is a molecular mechanism that confers acquired resistance to erlotinib in lung cancers with the wild-type EGFR.

Esposito CL, Cerchia L, Catuogno S, et al.
Multifunctional aptamer-miRNA conjugates for targeted cancer therapy.
Mol Ther. 2014; 22(6):1151-63 [PubMed] Article available free on PMC after 01/06/2015 Related Publications
While microRNAs (miRNAs) clearly regulate multiple pathways integral to disease development and progression, the lack of safe and reliable means for specific delivery of miRNAs to target tissues represents a major obstacle to their broad therapeutic application. Our objective was to explore the use of nucleic acid aptamers as carriers for cell-targeted delivery of a miRNA with tumor suppressor function, let-7g. Using an aptamer that binds to and antagonizes the oncogenic receptor tyrosine kinase Axl (GL21.T), here we describe the development of aptamer-miRNA conjugates as multifunctional molecules that inhibit the growth of Axl-expressing tumors. We conjugated the let-7g miRNA to GL21.T and demonstrate selective delivery to target cells, processing by the RNA interference machinery, and silencing of let-7g target genes. Importantly, the multifunctional conjugate reduced tumor growth in a xenograft model of lung adenocarcinoma. Therefore, our data establish aptamer-miRNA conjugates as a novel tool for targeted delivery of miRNAs with therapeutic potential.

Liu YP, Wang J, Avanzato VA, et al.
Oncolytic vaccinia virotherapy for endometrial cancer.
Gynecol Oncol. 2014; 132(3):722-9 [PubMed] Article available free on PMC after 01/06/2015 Related Publications
OBJECTIVE: Oncolytic virotherapy is a promising modality in endometrial cancer (EC) therapy. In this study, we compared the efficacy of the Copenhagen and Wyeth strains of oncolytic vaccinia virus (VV) incorporating the human thyroidal sodium iodide symporter (hNIS) as a reporter gene (VVNIS-C and VVNIS-W) in EC.
METHODS: Infectivity of VVNIS-C and VVNIS-W in type I (HEC1A, Ishikawa, KLE, RL95-2, and AN3 CA) and type II (ARK-1, ARK-2, and SPEC-2) human EC cell lines was evaluated. Athymic mice with ARK-2 or AN3 CA xenografts were treated with one intravenous dose of VVNIS-C or VVNIS-W. Tumor regression and in vivo infectivity were monitored via NIS expression using SPECT-CT imaging.
RESULTS: All EC cell lines except KLE were susceptible to infection and killing by VVNIS-C and VVNIS-W in vitro. VVNIS-C had higher infectivity and oncolytic activity than VVNIS-W in all cell lines, most notably in AN3 CA. Intravenous VVNIS-C was more effective at controlling AN3 CA xenograft growth than VVNIS-W, while both VVNIS-C and VVNIS-W ceased tumor growth and induced tumor regression in 100% of mice bearing ARK-2 xenografts.
CONCLUSION: Overall, VVNIS-C has more potent oncolytic viral activity than VVSIN-W in EC. VV appears to be most active in type II EC. Novel therapies are needed for the highly lethal type II EC histologies and further development of a VV clinical trial in type II EC is warranted.

Ji W, Choi CM, Rho JK, et al.
Mechanisms of acquired resistance to EGFR-tyrosine kinase inhibitor in Korean patients with lung cancer.
BMC Cancer. 2013; 13:606 [PubMed] Article available free on PMC after 01/06/2015 Related Publications
BACKGROUND: Despite an initial good response to epidermal growth factor receptor (EGFR)-tyrosine kinase inhibitor (TKI), resistance to treatment eventually develops. Although several resistance mechanisms have been discovered, little data exist regarding Asian patient populations.
METHODS: Among patients at a tertiary referral hospital in Korea who initially responded well to gefitinib and later acquired resistance to treatment, we selected those with enough tissues obtained before EGFR-TKI treatment and after the onset of resistance to examine mutations by mass spectrometric genotyping technology (Asan-Panel), MET amplification by fluorescence in situ hybridization (FISH), and analysis of AXL status, epithelial-to-mesenchymal transition (EMT) and neuroendocrine markers by immunohistochemistry.
RESULTS: Twenty-six patients were enrolled, all of whom were diagnosed with adenocarcinoma with EGFR mutations (19del: 16, L858R: 10) except one (squamous cell carcinoma with 19del). Secondary T790M mutation was detected in 11 subjects (42.3%) and four of these patients had other co-existing resistance mechanisms; increased AXL expression was observed in 5/26 patients (19.2%), MET gene amplification was noted in 3/26 (11.5%), and one patient acquired a mutation in the phosphatidylinositol-4, 5-bisphosphate 3-kinase catalytic subunit alpha isoform (PIK3CA) gene. None of the patients exhibited EMT; however, increased CD56 expression suggesting neuroendocrine differentiation was observed in two patients. Interestingly, conversion from L858R-mutant to wild-type EGFR occurred in one patient. Seven patients (26.9%) did not exhibit any known resistance mechanisms. Patients with a T790M mutation showed a more favorable prognosis.
CONCLUSION: The mechanisms and frequency of acquired EGFR-TKI resistance in Koreans are comparable to those observed in Western populations; however, more data regarding the mechanisms that drive EGFR-TKI resistance are necessary.

Xu J, Jia L, Ma H, et al.
Axl gene knockdown inhibits the metastasis properties of hepatocellular carcinoma via PI3K/Akt-PAK1 signal pathway.
Tumour Biol. 2014; 35(4):3809-17 [PubMed] Related Publications
The objective of this study is to clarify the possible role and mechanism of Axl in the tumorigenicity and metastasis process of hepatocellular carcinoma. The mRNA and protein expression levels of Axl in MHCC97-H and MHCC97-L cell lines were evaluated by real-time PCR and Western blot analysis. The key factor of phosphatidylinositol-3-kinase (PI3K)/Akt-p21-activated kinases-1 (PAK1) signaling pathway was studied after Axl expression was downregulated by shRNA. Finally, we analyzed the expression status of Axl protein expression in hepatocellular carcinoma tissues and its relationship with the prognosis of hepatocellular carcinoma. Axl was observed to be higher expressed in MHCC97-H cell lines compared to MHCC97-L cell lines. The downregulation of Axl in MHCC97-H cell lines resulted in the inhibition of the invasion ability of MHCC97-H cells both in vitro and in vivo. Interestingly, blocking PI3K/Akt signaling pathway by LY294002 or Akt siRNA could remarkably inhibit the PAK1 activation and cell invasion. Finally, the Axl protein expression was positively correlated with differentiation, lymph node metastasis, and clinical stage in patients with hepatocellular carcinoma patients (all P < 0.01). These findings suggest that Axl can also regulate the metastasis process of hepatocellular carcinoma and may serve as a new prognostic marker and therapeutic target for treating hepatocellular carcinoma metastasis.

Ohanna M, Cheli Y, Bonet C, et al.
Secretome from senescent melanoma engages the STAT3 pathway to favor reprogramming of naive melanoma towards a tumor-initiating cell phenotype.
Oncotarget. 2013; 4(12):2212-24 [PubMed] Article available free on PMC after 01/06/2015 Related Publications
Here, we showed that the secretome of senescent melanoma cells drives basal melanoma cells towards a mesenchymal phenotype, with characteristic of stems illustrated by increased level of the prototype genes FN1, SNAIL, OCT4 and NANOG. This molecular reprogramming leads to an increase in the low-MITF and slow-growing cell population endowed with melanoma-initiating cell features. The secretome of senescent melanoma cells induces a panel of 52 genes, involved in cell movement and cell/cell interaction, among which AXL and ALDH1A3 have been implicated in melanoma development. We found that the secretome of senescent melanoma cells activates the STAT3 pathway and STAT3 inhibition prevents secretome effects, including the acquisition of tumorigenic properties. Collectively, the findings provide insights into how the secretome of melanoma cells entering senescence upon chemotherapy treatments increases the tumorigenicity of naïve melanoma cells by inducing, through STAT3 activation, a melanoma-initiating cell phenotype that could favor chemotherapy resistance and relapse.

Whitman SP, Kohlschmidt J, Maharry K, et al.
GAS6 expression identifies high-risk adult AML patients: potential implications for therapy.
Leukemia. 2014; 28(6):1252-8 [PubMed] Article available free on PMC after 01/06/2015 Related Publications
Emerging data demonstrate important roles for the TYRO3/AXL/MERTK receptor tyrosine kinase (TAM RTK) family in diverse cancers. We investigated the prognostic relevance of GAS6 expression, encoding the common TAM RTK ligand, in 270 adults (n=71 aged<60 years; n=199 aged ⩾60 years) with de novo cytogenetically normal acute myeloid leukemia (CN-AML). Patients expressing GAS6 (GAS6+), especially those aged ⩾60 years, more often failed to achieve a complete remission (CR). In all patients, GAS6+ patients had shorter disease-free (DFS) and overall (OS) survival than patients without GAS6 expression (GAS6-). After adjusting for other prognostic markers, GAS6+ predicted CR failure (P=0.02), shorter DFS (P=0.004) and OS (P=0.04). To gain further biological insights, we derived a GAS6-associated gene-expression signature (P<0.001) that in GAS6+ patients included overexpressed BAALC and MN1, known to confer adverse prognosis in CN-AML, and overexpressed CXCL12, encoding stromal cell-derived factor, and its receptor genes, chemokine (C-X-C motif) receptor 4 (CXCR4) and CXCR7. This study reports for the first time that GAS6 expression is an adverse prognostic marker in CN-AML. Although GAS6 decoy receptors are not yet available in the clinic for GAS6+ CN-AML therapy, potential alternative therapies targeting GAS6+-associated pathways, for example, CXCR4 antagonists, may be considered for GAS6+ patients to sensitize them to chemotherapy.

Lv G, Lv T, Qiao S, et al.
RNA interference targeting human integrin α6 suppresses the metastasis potential of hepatocellular carcinoma cells.
Eur J Med Res. 2013; 18:52 [PubMed] Article available free on PMC after 01/06/2015 Related Publications
BACKGROUND: Increased metastasis has been proved to be associated with a poor prognosis for hepatocellular carcinoma (HCC). There are higher-level expressions of integrin α6 in the tissues of HCC patients with a higher fatality rate. The aim of this study is to investigate the effect of short hairpin RNA (shRNA) silencing integrin α6 expression on the proliferation and metastasis in HCC cell lines.
METHODS: Two human HCC cell lines, HepG2 and Bel-7402 were transfected with shRNA targeting human integrin α6. Protein and mRNA expression level were determined by western blot and real-time quantitative reverse transcription-polymerase chain reaction (qRT-PCR) to detect the transfected efficacy. The metastasis potential of HCC cells was evaluated by their proliferation, adhesion and invasion abilities. Cell proliferation was measured by MTT assay. Adhesion ability was measured by adhesion and spreading assays. The expression of matrix metalloproteinases (MMPs) was measured by qRT-PCR. The potential of invasion was measured by qRT-PCR and Transwell chamber assay. PI3K inhibitor LY294002 was used to explore the signal pathways of integrin α6 in HCC cells.
RESULTS: Western blot and qRT-PCR detection showed that over 75% of integrin α6 expression in HCC cells was through knockdown by shRNA. Proliferation, adhesion, spreading and invasion of HepG2 and Bel-7402 cells were dramatically decreased in cells transfected with shRNA compared to the control cells. P-ERK and p-AKT were reduced by shRNA targeting integrin α6 and PI3K inhibitor LY294002.
CONCLUSION: Knockdown integrin α6 can inhibit the proliferation and metastasis of HCC cells through PI3K/ARK and MAPK/ERK signal pathways by shRNA in vitro. Integrin α6 can mediate the metastasis potential, and can be used as a candidate target for therapy in HCC resulting in improved patients' survival.

Lee CH, Liu SY, Chou KC, et al.
Tumor-associated macrophages promote oral cancer progression through activation of the Axl signaling pathway.
Ann Surg Oncol. 2014; 21(3):1031-7 [PubMed] Related Publications
BACKGROUND: Recent studies suggest that tumor-associated macrophages (TAMs) promote tumor growth and metastasis. Our previous report demonstrated that Axl signaling promotes carcinogenesis and progression of oral squamous cell carcinoma (OSCC). This study aims to test the potential involvement of growth arrest-specific gene 6 (Gas6)/Axl signaling in the protumoral effect of TAMs.
METHODS: Co-culture experiments by incubation of OSCC cells (YD38 and OE) and macrophages (THP-1) were performed. The expression of Gas6/Axl and epithelial-mesenchymal transition (EMT) genes were examined in YD38 and OE cells. The effect of Gas6/Axl signaling on co-cultured cancer cells was further investigated by knocking down Axl expression and neutralizing Gas6. Axl and TAM distribution were analyzed by immunohistochemistry in OSCC tissues.
RESULTS: Activation of Axl signaling and increased expression of mesenchymal markers, along with increased invasion/migration ability of OSCC cells, was noted upon co-culture with THP-1. Neutralization of Gas6 in the co-culture system or knockdown of Axl in YD38 caused the co-culture effects to be diminished. Co-culture with THP-1 increased nuclear factor (NF)-κB nuclear translocation and transcription activity in YD38 cells. A significant association between the TAM count and expression of phosphorylated Axl (P = 0.004) was found in vivo cancer tissues.
CONCLUSIONS: TAMs play a protumor role in OSCC and likely promote tumor progression through activation of the Gas6/Axl-NF-κB signaling pathway. Therefore, Gas6/Axl and NF-κB signaling in OSCC cells may be a putative target for therapeutic intervention.

Skoda J, Neradil J, Zitterbart K, et al.
EGFR signaling in the HGG-02 glioblastoma cell line with an unusual loss of EGFR gene copy.
Oncol Rep. 2014; 31(1):480-7 [PubMed] Related Publications
Epidermal growth factor receptor (EGFR) gene amplification and the overexpression of EGFR are described as common features of glioblastoma multiforme (GBM). Nevertheless, we previously reported the loss of EGFR gene copy in a GBM specimen from a patient with an unusually favorable course of the disease, and the HGG-02 cell line with this aberration was successfully derived from this tumor. Here, we present a detailed analysis of changes in gene expression and cell signaling in the HGG-02 cell line; the GM7 reference cell line with a standard EGFR gene copy number derived from a very aggressive GBM was used as a control. We confirmed the downregulation of EGFR expression and signaling in HGG-02 cells using different methods (RTK analysis, gene profiling and RT-PCR). Other changes that may have contributed to the non-aggressive phenotype of the primary tumor were identified, including the downregulated phosphorylation of the Axl and Trk receptors, as well as increased activity of JNK and p38 kinases. Notably, differences in PDGF signaling were detected in both of these cell lines; HGG-02 cells preferentially expressed and signaled through PDGFRα, and PDGFRβ was strongly overexpressed and phosphorylated in the GM7 reference cell line. Using expression profiling of cancer-related genes, we revealed the specific profile of HGG-02 cells that included upregulated tumor-suppressors as well as downregulated genes associated with the extracellular matrix. This study represents the first comprehensive analysis of gene expression and cell signaling in glioblastoma cells with lower EGFR gene dosage. As indicated by our results, the TAM receptors, Trk receptors and PDGFRs need to be investigated further since their regulation appears to be important for glioblastoma biological features as well as the clinical course of the disease.

Heckmann D, Maier P, Laufs S, et al.
The disparate twins: a comparative study of CXCR4 and CXCR7 in SDF-1α-induced gene expression, invasion and chemosensitivity of colon cancer.
Clin Cancer Res. 2014; 20(3):604-16 [PubMed] Related Publications
PURPOSE: In colorectal cancer, increased expression of the CXC chemokine receptor 4 (CXCR4) has been shown to provoke metastatic disease due to the interaction with its ligand stromal cell-derived factor-1 (SDF-1). Recently, a second SDF-1 receptor, CXCR7, was found to enhance tumor growth in solid tumors. Albeit signaling cascades via SDF-1/CXCR4 have been intensively studied, the significance of the SDF-1/CXCR7-induced intracellular communication triggering malignancy is still only marginally understood.
EXPERIMENTAL DESIGN: In tumor tissue of 52 patients with colorectal cancer, we observed that expression of CXCR7 and CXCR4 increased with tumor stage and tumor size. Asking whether activation of CXCR4 or CXCR7 might result in a similar expression pattern, we performed microarray expression analyses using lentivirally CXCR4- and/or CXCR7-overexpressing SW480 colon cancer cell lines with and without stimulation by SDF-1α.
RESULTS: Gene regulation via SDF-1α/CXCR4 and SDF-1α/CXCR7 was completely different and partly antidromic. Differentially regulated genes were assigned by gene ontology to migration, proliferation, and lipid metabolic processes. Expressions of AKR1C3, AXL, C5, IGFBP7, IL24, RRAS, and TNNC1 were confirmed by quantitative real-time PCR. Using the in silico gene set enrichment analysis, we showed that expressions of miR-217 and miR-218 were increased in CXCR4 and reduced in CXCR7 cells after stimulation with SDF-1α. Functionally, exposure to SDF-1α increased invasiveness of CXCR4 and CXCR7 cells, AXL knockdown hampered invasion. Compared with controls, CXCR4 cells showed increased sensitivity against 5-FU, whereas CXCR7 cells were more chemoresistant.
CONCLUSIONS: These opposing results for CXCR4- or CXCR7-overexpressing colon carcinoma cells demand an unexpected attention in the clinical application of chemokine receptor antagonists such as plerixafor.

Lee HJ, Jeng YM, Chen YL, et al.
Gas6/Axl pathway promotes tumor invasion through the transcriptional activation of Slug in hepatocellular carcinoma.
Carcinogenesis. 2014; 35(4):769-75 [PubMed] Related Publications
Hepatocellular carcinoma (HCC) is one of the most common fatal cancers worldwide. Other than the sorafenib treatment, no effective systemic therapy has been available thus far. Most targets in molecularly targeted therapy for cancer are receptor tyrosine kinases (RTKs). Therefore, identifying activated RTKs in HCC is critical for developing new molecularly targeted therapies. Using a phospho-RTK array, we found that Axl is one of the most frequently activated RTKs in liver cancer cell lines. The knockdown of Axl by RNA interference significantly reduced cell migration and invasion in the HCC cell lines HA22T and Mahlavu. Stimulation of HCC cell lines by Axl ligand growth arrest-specific 6 (Gas6) enhanced cell migration and invasion. The Gas6/Axl pathway enhanced the expression of the epithelial-mesenchymal transition-inducing transcription factor Slug, which is essential for the invasion-promoting activity of Axl. Treating HCC cells with the Axl inhibitor bosutinib suppressed Slug expression and decreased the invasiveness of HCC cell lines. These findings indicate that Gas6/Axl regulates tumor invasion through the transcriptional activation of Slug.

Lemke G
Biology of the TAM receptors.
Cold Spring Harb Perspect Biol. 2013; 5(11):a009076 [PubMed] Related Publications
The TAM receptors--Tyro3, Axl, and Mer--comprise a unique family of receptor tyrosine kinases, in that as a group they play no essential role in embryonic development. Instead, they function as homeostatic regulators in adult tissues and organ systems that are subject to continuous challenge and renewal throughout life. Their regulatory roles are prominent in the mature immune, reproductive, hematopoietic, vascular, and nervous systems. The TAMs and their ligands--Gas6 and Protein S--are essential for the efficient phagocytosis of apoptotic cells and membranes in these tissues; and in the immune system, they act as pleiotropic inhibitors of the innate inflammatory response to pathogens. Deficiencies in TAM signaling are thought to contribute to chronic inflammatory and autoimmune disease in humans, and aberrantly elevated TAM signaling is strongly associated with cancer progression, metastasis, and resistance to targeted therapies.

Dunne PD, McArt DG, Blayney JK, et al.
AXL is a key regulator of inherent and chemotherapy-induced invasion and predicts a poor clinical outcome in early-stage colon cancer.
Clin Cancer Res. 2014; 20(1):164-75 [PubMed] Article available free on PMC after 01/06/2015 Related Publications
PURPOSE: Despite the use of 5-fluorouracil (5-FU)-based adjuvant treatments, a large proportion of patients with high-risk stage II/III colorectal cancer will relapse. Thus, novel therapeutic strategies are needed for early-stage colorectal cancer. Residual micrometastatic disease from the primary tumor is a major cause of patient relapse.
EXPERIMENTAL DESIGN: To model colorectal cancer tumor cell invasion/metastasis, we have generated invasive (KRASMT/KRASWT/+chr3/p53-null) colorectal cancer cell subpopulations. Receptor tyrosine kinase (RTK) screens were used to identify novel proteins that underpin the migratory/invasive phenotype. Migration/invasion was assessed using the XCELLigence system. Tumors from patients with early-stage colorectal cancer (N = 336) were examined for AXL expression.
RESULTS: Invasive colorectal cancer cell subpopulations showed a transition from an epithelial-to-mesenchymal like phenotype with significant increases in migration, invasion, colony-forming ability, and an attenuation of EGF receptor (EGFR)/HER2 autocrine signaling. RTK arrays showed significant increases in AXL levels in all invasive sublines. Importantly, 5-FU treatment resulted in significantly increased migration and invasion, and targeting AXL using pharmacologic inhibition or RNA interference (RNAi) approaches suppressed basal and 5-FU-induced migration and invasion. Significantly, high AXL mRNA and protein expression were found to be associated with poor overall survival in early-stage colorectal cancer tissues.
CONCLUSIONS: We have identified AXL as a poor prognostic marker and important mediator of cell migration/invasiveness in colorectal cancer. These findings provide support for the further investigation of AXL as a novel prognostic biomarker and therapeutic target in colorectal cancer, in particular in the adjuvant disease in which EGFR/VEGF-targeted therapies have failed.

Cichoń MA, Szentpetery Z, Caley MP, et al.
The receptor tyrosine kinase Axl regulates cell-cell adhesion and stemness in cutaneous squamous cell carcinoma.
Oncogene. 2014; 33(32):4185-92 [PubMed] Related Publications
Axl is a receptor tyrosine kinase (RTK) upregulated in various tumors including cutaneous squamous cell carcinoma (SCC). Axl expression correlates with poor prognosis and induction of epithelial-mesenchymal transition (EMT), hence we hypothesized that Axl is involved in the disruption of cell-cell adhesion to allow invasion and chemotherapy resistance of the cancer stem cell population. Cutaneous SCC cell lines with stable knockdown of Axl were generated using retroviral vectors. Axl depletion altered expression of intercellular junction molecules increasing cell-cell adhesion with downregulation of Wnt and TGFβR signaling. Furthermore, Axl expression correlated with the expression of putative cancer stem cell markers, CD44 and ALDH1, increased resistance to chemotherapy drugs, enhanced sphere formation ability and expression of EMT features by cancer stem cells. Axl depletion resulted in loss of tumor formation in an in vivo zebrafish xenograft model. In conclusion, these data suggest that abrogation of Axl results in loss of cancer stem cell properties indicating a role for Axl as a therapeutic target in chemotherapy-resistant cancer.

Giles KM, Kalinowski FC, Candy PA, et al.
Axl mediates acquired resistance of head and neck cancer cells to the epidermal growth factor receptor inhibitor erlotinib.
Mol Cancer Ther. 2013; 12(11):2541-58 [PubMed] Related Publications
Elevated expression and activity of the epidermal growth factor receptor (EGFR) is associated with development and progression of head and neck cancer (HNC) and a poor prognosis. Clinical trials with EGFR tyrosine kinase inhibitors (e.g., erlotinib) have been disappointing in HNC. To investigate the mechanisms mediating resistance to these agents, we developed an HNC cell line (HN5-ER) with acquired erlotinib resistance. In contrast to parental HN5 HNC cells, HN5-ER cells exhibited an epithelial-mesenchymal (EMT) phenotype with increased migratory potential, reduced E-cadherin and epithelial-associated microRNAs (miRNA), and elevated vimentin expression. Phosphorylated receptor tyrosine kinase profiling identified Axl activation in HN5-ER cells. Growth and migration of HN5-ER cells were blocked with a specific Axl inhibitor, R428, and R428 resensitized HN5-ER cells to erlotinib. Microarray analysis of HN5-ER cells confirmed the EMT phenotype associated with acquired erlotinib resistance, and identified activation of gene expression associated with cell migration and inflammation pathways. Moreover, increased expression and secretion of interleukin (IL)-6 and IL-8 in HN5-ER cells suggested a role for inflammatory cytokine signaling in EMT and erlotinib resistance. Expression of the tumor suppressor miR-34a was reduced in HN5-ER cells and increasing its expression abrogated Axl expression and reversed erlotinib resistance. Finally, analysis of 302 HNC patients revealed that high tumor Axl mRNA expression was associated with poorer survival (HR = 1.66, P = 0.007). In summary, our results identify Axl as a key mediator of acquired erlotinib resistance in HNC and suggest that therapeutic inhibition of Axl by small molecule drugs or specific miRNAs might overcome anti-EGFR therapy resistance.

Vazquez-Martin A, Cufí S, Oliveras-Ferraros C, et al.
IGF-1R/epithelial-to-mesenchymal transition (EMT) crosstalk suppresses the erlotinib-sensitizing effect of EGFR exon 19 deletion mutations.
Sci Rep. 2013; 3:2560 [PubMed] Article available free on PMC after 01/06/2015 Related Publications
Using non-small cell lung carcinoma (NSCLC) cells harboring the erlotinib-sensitizing Epidermal Growth Factor Receptor (EGFR) exon 19 mutation delE746-A750, we developed erlotinib-refractory derivatives in which hyperactive Insulin-like Growth Factor-1 Receptor (IGF-1R) signaling associated with enrichment in epithelial-to-mesenchymal transition (EMT)-related morphological and transcriptional features. We then explored whether an IGF-1R/EMT crosstalk was sufficient to promote erlotinib refractoriness in the absence of second-site EGFR mutations, MET and AXL hyperactivation. Transforming Growth Factor-beta1 (TGFβ1)-induced mesenchymal trans-differentiation was sufficient to impede erlotinib functioning in the presence of drug-sensitive delE746-A750 EGFR mutation. Pharmacological blockade of IGF-1R fully prevented the TGFβ1's ability to activate an EMT protein signature [E-cadherin low/vimentin high]. The sole presence of erlotinib was capable of rapidly activate an IGF-1R-dependent, vimentin-enriched mesenchymal-like phenotype in delE746-A750-mutated epithelial cells. Even if transient, NSCLC cells' intrinsic plasticity to undergo crosstalk between IGF-1R and EMT signaling pathways can sufficiently eliminate the erlotinib-sensitizing effect of highly prevalent EGFR mutations and suggests the urgent need for dual IGF-1R/EMT-targeting strategies to circumvent erlotinib resistance.

Kim HR, Kim WS, Choi YJ, et al.
Epithelial-mesenchymal transition leads to crizotinib resistance in H2228 lung cancer cells with EML4-ALK translocation.
Mol Oncol. 2013; 7(6):1093-102 [PubMed] Related Publications
Epithelial-mesenchymal transition (EMT) is associated with reduced sensitivity to many chemotherapeutic drugs, including EGFR tyrosine kinase inhibitors. Here, we investigated if this reduced sensitivity also contributes to resistance to crizotinib, an ALK inhibitor of lung cancer that exhibits the EML4-ALK translocation. We established a crizotinib-resistant subline (H2228/CR), which was derived from the parental H2228 cell line by long-term exposure to increasing concentrations of crizotinib. Characteristics associated with EMT, including morphology, EMT marker proteins, and cellular mobility, were analyzed. Compared with H2228 cells, the growth of H2228/CR cells was independent of EML4-ALK, and H2228/CR cells showed cross-resistance to TAE-684 (a second-generation ALK inhibitor). Phenotypic changes to the spindle-cell shape were noted in H2228/CR cells, which were accompanied by a decrease in E-cadherin and increase in vimentin and AXL. In addition, H2228/CR cells showed increased secretion and expression of TGF-β1. Invasion and migration capabilities were dramatically increased in H2228/CR cells. Applying TGF-β1 treatment to parental H2228 cells for 72 h induced reversible EMT, leading to crizotinib resistance, but this was reversed by the removal of TGF-β1. Suppression of vimentin in H2228/CR cells by siRNA treatment restored sensitivity to crizotinib. Furthermore, these resistant cells remained highly sensitive to the Hsp90 inhibitors, similar to the parental H2228 cells. In conclusion, we suggest EMT is possibly involved in acquired resistance to crizotinib, and that HSP90 inhibitors could be a promising option for the treatment of EMT.

Ben-Batalla I, Schultze A, Wroblewski M, et al.
Axl, a prognostic and therapeutic target in acute myeloid leukemia mediates paracrine crosstalk of leukemia cells with bone marrow stroma.
Blood. 2013; 122(14):2443-52 [PubMed] Related Publications
Acute myeloid leukemia (AML) represents a clonal disease of hematopoietic progenitors characterized by acquired heterogenous genetic changes that alter normal mechanisms of proliferation, self-renewal, and differentiation.(1) Although 40% to 45% of patients younger than 65 years of age can be cured with current therapies, only 10% of older patients reach long-term survival.(1) Because only very few novel AML drugs were approved in the past 2 decades, there is an urgent need to identify novel targets and therapeutic strategies to treat underserved AML patients. We report here that Axl, a member of the Tyro3, Axl, Mer receptor tyrosine kinase family,(2-4) represents an independent prognostic marker and therapeutic target in AML. AML cells induce expression and secretion of the Axl ligand growth arrest-specific gene 6 (Gas6) by bone marrow-derived stromal cells (BMDSCs). Gas6 in turn mediates proliferation, survival, and chemoresistance of Axl-expressing AML cells. This Gas6-Axl paracrine axis between AML cells and BMDSCs establishes a chemoprotective tumor cell niche that can be abrogated by Axl-targeting approaches. Axl inhibition is active in FLT3-mutated and FLT3 wild-type AML, improves clinically relevant end points, and its efficacy depends on presence of Gas6 and Axl. Axl inhibition alone or in combination with chemotherapy might represent a novel therapeutic avenue for AML.

Rosell R, Bivona TG, Karachaliou N
Genetics and biomarkers in personalisation of lung cancer treatment.
Lancet. 2013; 382(9893):720-31 [PubMed] Related Publications
Non-small-cell lung cancer is often diagnosed at the metastatic stage, with median survival of just 1 year. The identification of driver mutations in the epidermal growth factor receptor (EGFR) as the primary oncogenic event in a subset of lung adenocarcinomas led to a model of targeted treatment and genetic profiling of the disease. EGFR tyrosine kinase inhibitors confer remission in 60% of patients, but responses are short-lived. The pre-existing EGFR Thr790Met mutation could be a subclonal driver responsible for these transient responses. Overexpression of AXL and reduced MED12 function are hallmarks of resistance to tyrosine kinase inhibitors in EGFR-mutant non-small-cell lung cancer. Crosstalk between signalling pathways is another mechanism of resistance; therefore, identification of the molecular components involved could lead to the development of combination therapies cotargeting these molecules instead of EGFR tyrosine kinase inhibitor monotherapy. Additionally, novel biomarkers could be identified through deep sequencing analysis of serial rebiopsies before and during treatment.

Suleiman L, Négrier C, Boukerche H
Protein S: A multifunctional anticoagulant vitamin K-dependent protein at the crossroads of coagulation, inflammation, angiogenesis, and cancer.
Crit Rev Oncol Hematol. 2013; 88(3):637-54 [PubMed] Related Publications
Since its discovery in 1970, protein S (PS) has emerged as a key vitamin K-dependent natural anticoagulant protein at the crossroads of multiple biological processes, including coagulation, apoptosis, atherosclerosis, angiogenesis/vasculogenesis, and cancer progression. Following the binding to a unique family of protein tyrosine kinase receptors referred to as Tyro-3, Axl and Mer (TAM) receptors, PS can lead to regulation of coagulation, phagocytosis of apoptotic cells, cell survival, activation of innate immunity, vessel integrity and angiogenesis, and local invasion and metastasis. Because of these dynamics and multiple functions of PS, which are largely lost following invalidation of the mouse PROS1 gene, this molecule is currently intensively studied in biomedical research. The purpose of this review is to provide a brief chronicle of the discovery and current understanding of the mechanisms of PS signaling, and how PS and their signaling partners regulate various cellular functions, with a particular focus on TAM receptors.

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