Gene Summary

Gene:PLK2; polo like kinase 2
Aliases: SNK, hSNK, hPlk2
Summary:The protein encoded by this gene is a member of the polo family of serine/threonine protein kinases that have a role in normal cell division. This gene is most abundantly expressed in testis, spleen and fetal tissues, and its expression is inducible by serum, suggesting that it may also play an important role in cells undergoing rapid cell division. Alternatively spliced transcript variants encoding different isoforms have been found for this gene. [provided by RefSeq, Nov 2011]
Databases:OMIM, HGNC, Ensembl, GeneCard, Gene
Protein:serine/threonine-protein kinase PLK2
Source:NCBIAccessed: 01 September, 2019


What does this gene/protein do?
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Cancer Overview

Research Indicators

Publications Per Year (1994-2019)
Graph generated 01 September 2019 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 01 September, 2019 using data from PubMed, MeSH and CancerIndex

Specific Cancers (6)

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: PLK2 (cancer-related)

Qin BB, Tang DF, Ni ML, et al.
The aberrant activation of Wnt pathway caused by β-catenin mutation and its prognostic significance in NK/T-cell lymphoma.
Neoplasma. 2019; 66(1):20-27 [PubMed] Related Publications
The aberrant activation of the Wnt/β-catenin signal has an important role in the progression of cancers. Herein, we investigated β-catenin mutation and the activation of the Wnt pathway in association with the clinical-pathological characteristics, chemo-resistance and prognosis of NK/T-cell lymphoma (NKTCL). Real-time quantitative PCR, immunocytochemistry and immunohistochemistry SP methods detected the levels of β-catenin, c-myc and cyclin D1 in human NKTCL cell lines (SNK-6 and YTS) and NKTCL tissues. Mutation analysis was detected in exon 3 of β-catenin gene; and we analyzed cell viability after histone deacetylase inhibitor (HDACi) treatment. As a result, 19 (38%) of NK/T-cell lymphoma displayed nuclear β-catenin and 16 (32%) contained mutations in exon 3; while no mutations were detected in lymphomas negative for β-catenin nuclear staining (p<0.05). Most mutations affecting β-catenin were adjacent to regulatory phosphorylation sites. β-catenin, c-myc and cyclin D1 were significantly elevated in SNK-6 and YTS cell lines compared to normal NK/T cells (p<0.05). Furthermore, the high expression of β-catenin, c-myc and cyclin D1 significantly correlated with the III/IV Ann Arbor stage. Additionally, the expression of β-catenin in the SNK-6 cell line decreased significantly after treatment with HDACi, and Kaplan-Meier survival analysis revealed that the elevated expression of β-catenin correlated with poor prognosis in NKTCL patients (23.66±2.77 months vs 31.65±1.78 months, p=0.023). In conclusion: mutations in exon 3 of β-catenin and the activated Wnt pathway are common in NK/T-cell lymphoma that has nuclear β-catenin, and it is closely correlated with the Ann Arbor stage and prognosis in NKTCL patients.

Wang L, Bi XW, Zhu YJ, et al.
IL-2Rα up-regulation is mediated by latent membrane protein 1 and promotes lymphomagenesis and chemotherapy resistance in natural killer/T-cell lymphoma.
Cancer Commun (Lond). 2018; 38(1):62 [PubMed] Free Access to Full Article Related Publications
BACKGROUND: Natural killer/T-cell lymphoma (NKTCL) is a highly aggressive non-Hodgkin lymphoma often resistant to chemotherapy. Serum level of soluble IL-2 receptor α (IL-2Rα) is elevated in NKTCL patients and correlates significantly with treatment response and survival. In the current study we examined the potential role of IL-2Rα by over-expressing IL-2Rα in representative cell lines.
METHODS: Levels of IL-2Rα were evaluated in the human natural killer cell line NK-92 and the NKTCL cell line SNK-6. Lentiviral vectors were used to express latent membrane protein 1 (LMP1) in NK-92 cells, and IL-2Rα in both NK-92 and SNK-6 cells. The biological effects of these genes on proliferation, apoptosis, cell cycle distribution, and chemosensitivity were analyzed.
RESULTS: Expression of IL-2Rα was significantly higher in SNK-6 cells than in NK-92 cells. Expressing LMP1 in NK-92 cells remarkably up-regulated IL-2Rα levels, whereas selective inhibitorss of the proteins in the MAPK/NF-κB pathway significantly down-regulated IL-2Rα. IL-2Rα overexpression in SNK-6 cells promoted cell proliferation by altering cell cycle distribution, and induced resistance to gemcitabine, doxorubicin, and asparaginase. These effects were reversed by an anti-IL-2Rα antibody.
CONCLUSIONS: Our results suggest that LMP1 activates the MAPK/NF-κB pathway in NKTCL cells, up-regulating IL-2Rα expression. IL-2Rα overexpression promotes growth and chemoresistance in NKTCL, making this interleukin receptor a potential therapeutic target.

Pitt JJ, Riester M, Zheng Y, et al.
Characterization of Nigerian breast cancer reveals prevalent homologous recombination deficiency and aggressive molecular features.
Nat Commun. 2018; 9(1):4181 [PubMed] Free Access to Full Article Related Publications
Racial/ethnic disparities in breast cancer mortality continue to widen but genomic studies rarely interrogate breast cancer in diverse populations. Through genome, exome, and RNA sequencing, we examined the molecular features of breast cancers using 194 patients from Nigeria and 1037 patients from The Cancer Genome Atlas (TCGA). Relative to Black and White cohorts in TCGA, Nigerian HR + /HER2 - tumors are characterized by increased homologous recombination deficiency signature, pervasive TP53 mutations, and greater structural variation-indicating aggressive biology. GATA3 mutations are also more frequent in Nigerians regardless of subtype. Higher proportions of APOBEC-mediated substitutions strongly associate with PIK3CA and CDH1 mutations, which are underrepresented in Nigerians and Blacks. PLK2, KDM6A, and B2M are also identified as previously unreported significantly mutated genes in breast cancer. This dataset provides novel insights into potential molecular mechanisms underlying outcome disparities and lay a foundation for deployment of precision therapeutics in underserved populations.

Goroshchuk O, Kolosenko I, Vidarsdottir L, et al.
Polo-like kinases and acute leukemia.
Oncogene. 2019; 38(1):1-16 [PubMed] Related Publications
Acute leukemia is a common malignancy among children and adults worldwide and many patients suffer from chronic health issues using current therapeutic approaches. Therefore, there is a great need for the development of novel and more specific therapies with fewer side effects. The family of Polo-like kinases (Plks) is a group of five serine/threonine kinases that play an important role in cell cycle regulation and are critical targets for therapeutic invention. Plk1 and Plk4 are novel targets for cancer therapy as leukemic cells often express higher levels than normal cells. In contrast, Plk2 and Plk3 are considered to be tumor suppressors. Several small molecule inhibitors have been developed for targeting Plk1 inhibition. Despite reaching phase III clinical trials, one of the ATP-competitive Plk1 inhibitor, volasertib, did not induce an objective clinical response and even caused lethal side effects in some patients. In order to improve the specificity of the Plk1 inhibitors and reduce off-target side effects, novel RNA interference (RNAi)-based therapies have been developed. In this review, we summarize the mechanisms of action of the Plk family members in acute leukemia, describe preclinical studies and clinical trials involving Plk-targeting drugs and discuss novel approaches in Plk targeting.

Han T, Lin J, Wang Y, et al.
Forkhead box D1 promotes proliferation and suppresses apoptosis via regulating polo-like kinase 2 in colorectal cancer.
Biomed Pharmacother. 2018; 103:1369-1375 [PubMed] Related Publications
Transcription factor forkhead box D1 (FOXD1), a member of forkhead box family, has been recognized as a caner-related gene. Aberrant expression of FOXD1 is observed in glioma, lung cancer and breast cancer. However, the clinical significance of FOXD1 and its role in colorectal cancer (CRC) are unknown. Here, we found that FOXD1 displayed a higher expression in CRC tissues compared to tumor-adjacent tissues. Upregulation of FOXD1 was further confirmed in CRC tissues compared to normal tissues based on data from three GSE cohorts. Our clinical data indicated that high FOXD1 level was associated with tumor size (≥5 cm) and TNM tumor stage (III + IV). Moreover, both our data and TCGA data found that high expression of FOXD1 predicted poor prognosis of CRC patients. Next, we revealed that FOXD1 knockdown suppressed proliferation, cell cycle progression and induced apoptosis of SW480 cells in vitro. In accordance, FOXD1 overexpression promoted proliferation and reduced apoptosis of HT29 cells. Interestingly, polo-like kinase 2 (Plk2) expression was elevated and it positively correlated with FOXD1 expression in CRC tissues. FOXD1 promoted the expression of Plk2 mRNA and protein in CRC cells. Notably, Plk2 restoration abolished the effect of FOXD1 knockdown on proliferation and apoptosis of SW480 cells. Plk2 knockdown resulted in decreased proliferation and increased apoptosis of FOXD1-overexpressing HT29 cells. Altogether, we demonstrate for the first time that FOXD1 functions as an oncoprotein and a potential prognostic biomarker in CRC.

Zhou J, Zhang C, Sui X, et al.
Histone deacetylase inhibitor chidamide induces growth inhibition and apoptosis in NK/T lymphoma cells through ATM-Chk2-p53-p21 signalling pathway.
Invest New Drugs. 2018; 36(4):571-580 [PubMed] Related Publications
We investigated the anti-tumour effects and the underlying molecular mechanisms of a new oral histone deacetylase inhibitor (HDACi), chidamide, in NK/T cell lymphoma (NKTCL), a rare and highly aggressive non-Hodgkin lymphoma with poor outcomes. SNT-8 and SNK-10 NKTCL cell lines were exposed to different concentrations of chidamide for the indicated time. The treated cells were analysed for cell proliferation, cell cycle progression, and cell apoptosis. Proteins in the AKT/mTOR and MAPK signalling pathways and the DNA damage response (DDR) cell cycle checkpoint pathway were measured by Western blotting. Chidamide inhibited cell proliferation in a dose- and time-dependent manner, arrested cell cycle progression at the G0/G1 phase, and induced apoptosis in the NKTCL cell lines. In addition, we found that chidamide suppressed the phosphorylation levels of proteins in the AKT/mTOR and MAPK signalling pathways and activated the DDR cell cycle checkpoint pathway, that is, the ATM-Chk2-p53-p21 pathway. Expression of EBV genes was also assessed by Real-Time PCR. Chidamide induced EBV lytic-phase gene expression in EBV-positive NKTCL. Our results provide evidence that chidamide shows antitumour effects by inhibiting the AKT/mTOR and MAPK signalling pathways and activating the ATM-Chk2-p53-p21 signalling pathway in vitro.

Matthew EM, Yang Z, Peri S, et al.
Plk2 Loss Commonly Occurs in Colorectal Carcinomas but not Adenomas: Relationship to mTOR Signaling.
Neoplasia. 2018; 20(3):244-255 [PubMed] Free Access to Full Article Related Publications
Plk2 is a target of p53. Our previous studies demonstrated that with wild-type p53, Plk2 impacts mTOR signaling in the same manner as TSC1, and Plk2-deficient tumors grew larger than control. Other investigators have demonstrated that Plk2 phosphorylates mutant p53 in a positive feedback loop. We investigated Plk2's tumor suppressor functions in relationship to mTOR signaling. Archival specimens from 12 colorectal adenocarcinomas were stained for markers including Plk2, phosphorylated mTOR (serine 2448) and ribosomal S6 (Serine 235/236). We show that Plk2 is expressed in normal colon, with a punctate staining pattern in supranuclear cytoplasm. In colorectal adenocarcinoma, Plk2 demonstrates complete or partial loss of expression. Strong expression of phosphorylated mTOR is observed in the invasive front. Phosphorylated S6 expression partially correlates with phosphorylated mTOR expression but appears more diffuse in some cases. p53 and Ki67 expression is diffuse, in the subset of cases examined. In order to determine whether Plk2 is lost prior to the development of invasive cancer, 8 colon polyps from 6 patients were evaluated for Plk2 expression. All polyps are positive for Plk2. A Cancer Genome Atlas search identified Plk2 mutations to be infrequent in colorectal adenocarcinomas. Neither Plk2 methylation (in the gene body) nor copy number variations correlated with changes in mRNA expression levels. Loss of Plk2 expression along with accentuated expression of phosphorylated mTOR and phosphorylated S6 at the invasive front in some colorectal carcinomas is consistent with previous findings that an interaction between Plk2 and TSC1 / mTOR signaling molecules plays a role in tumor suppression. Plk2 protein expression is lost at the same stage in colorectal carcinogenesis as p53. The p53 dependence of Plk2 loss and tumor suppressor function in relationship to mTOR signaling may have therapeutic implications.

Sui X, Zhang C, Zhou J, et al.
Resveratrol inhibits Extranodal NK/T cell lymphoma through activation of DNA damage response pathway.
J Exp Clin Cancer Res. 2017; 36(1):133 [PubMed] Free Access to Full Article Related Publications
BACKGROUND: Extranodal NK/T cell lymphoma (NKTCL) is a highly aggressive non-Hodgkin lymphoma with poor prognosis. Resveratrol (RSV, 3,5,4'-trihydroxystilbene), a natural nontoxic phenolic compound found in the skin of grapes and some other spermatophytes, performs multiple bioactivities, such as antioxidant activity, anti-aging activity, reduction of cardiovascular disease risk and anticarcinogenic effect. Here we report the anti-tumor effect of RSV in NKTCL cell lines SNT-8, SNK-10 and SNT-16.
RESULTS: RSV inhibited NKTCL cell proliferation in a dose- and time-dependent manner and arrested cell cycle at S phase. It induced NKTCL cells apoptosis through mitochondrial pathway, shown as down-regulation of MCl-1 and survivin, up-regulation of Bax and Bad, and activation of caspase-9 and caspase-3. In addition, we found that RSV suppressed the phosphorylation level of AKT and Stat3, and activated DNA damage response (DDR) pathway directly or through up-regulation of Zta of Epstein-Barr virus (EBV). Furthermore, using KU55933 as the inhibitor of pATM, we verified that DDR played an important role in RSV inducing NKTCL apoptosis. RSV also showed synergistic effect on activating DDR pathway in combination with etoposide or ionizing radiation, which resulted in cell proliferation inhibition and apoptosis.
CONCLUSIONS: Our results provide in vitro evidence that RSV produces anti-tumor effect by activating DDR pathway in an ATM/Chk2/p53 dependent manner. So we suggest that RSV may be worthy for further study as an anti-tumor drug for NKTCL treatment.

Shen T, Li Y, Chen Z, et al.
CHOP negatively regulates Polo-like kinase 2 expression via recruiting C/EBPα to the upstream-promoter in human osteosarcoma cell line during ER stress.
Int J Biochem Cell Biol. 2017; 89:207-215 [PubMed] Related Publications
Polo-like kinase 2 (Plk2) is a member of the serine/threonine protein kinase family involved in cell-cycle regulation and cellular response to stresses. However, the alteration of Plk2 in response to endoplasmic reticulum (ER) stress has not been well described. In the present study, we focused on the regulation of Plk2 regulation in response to ER stress. Plk2 expression was dramatically decreased under ER stress induced by brefeldin A (BFA), thapsigargin (TG), or tunicamycin (TM), and this down regulation of Plk2 expression was dependent on activating transcription factor 4 (ATF4) and C/EBP homology protein (CHOP). Luciferase activity analysis of the truncated Plk2 promoter indicated that regions from -2506 to -1806 and from -1002 to -830 of the Plk2 promoter were sensitive to BFA. Additionally, ChIP and ChIP Re-IP assays showed that CHOP and C/EBPα were assembled on the same region of Plk2 promoter. Notably, we identified two C/EBPα responsive elements at positions -2002 and -948, to which C/EBPα or CHOP binding was enhanced by BFA under in vitro and in vivo conditions. Finally, overexpression of Plk2 inhibits cell apoptosis and promotes cell proliferation in response to ER stress. In summary, these results demonstrated that ER stress plays a crucial role in Plk2 expression. CHOP may up-regulate DNA-binding affinities after BFA treatment, via recruiting C/EBPα to the upstream-promoter of Plk2. These findings may contribute to the understanding of the molecular mechanism of Plk2 regulation.

Zhang X, Shi C, Yue G, et al.
The Effects of Lentivirus-mediated shRNA Interference Targeting Mcl-1 on Growth of NK/T-cell Lymphoma.
Neoplasma. 2017; 64(4):511-517 [PubMed] Related Publications
Myeloid leukemia-1 (Mcl-1) gene has been reported as an important factor in various types of cancer, but little research was processed on natural killer (NK)/T-cell lymphoma, a kind of a highly aggressive disease with a poor prognosis. Here we investigated the expression of Mcl-1 in seven lymphoma cell lines and its potential role as a molecular drug target for NK/T-cell lymphoma therapy by using lentivirus-mediated shRNA interference targeting Mcl-1 (lenti-shMcl-1). In our study, the expression of Mcl-1 in different lymphoma cell lines were evaluated firstly, after that lenti-shMcl-1 was constructed and transduced into NK/T-cell lymphoma cell line SNK-6 which had a high level expression of Mcl-1. Methylthiazolete-Trazolium (MTT) assay and flow cytometry (FCA) were employed to detect the status of proliferation and apoptosis after infection. Lastly we investigated the effects of chemotherapy agent vincristine (VCR) combination with lenti-shMcl-1 by MTT and FCA assay. The results showed that Mcl-1 gene expressed in all seven lymphoma cell lines at different levels. Recombinant lentiviruses could infect SNK-6 cells effectively. Mcl-1 expression level was remarkably down-regulated after infection with lenti-shMcl-1. The growth of SNK-6 cells was inhibited significantly through apoptosis pathway. Otherwise, lenti-shMcl-1 also revealed a significant chemosensitizing effect in combination with vincristine. In a word, we demonstrated that lenti-shMcl-1 had a significant anti-NK/T cell lymphoma effect and targeting Mcl-1 therapy could be a promising novel approach in treatment of lymphoma.

Olbryt M, Rusin A, Fokt I, et al.
Bis-anthracycline WP760 abrogates melanoma cell growth by transcription inhibition, p53 activation and IGF1R downregulation.
Invest New Drugs. 2017; 35(5):545-555 [PubMed] Free Access to Full Article Related Publications
Anthracycline chemotherapeutics, e.g. doxorubicin and daunorubicin, are active against a broad spectrum of cancers. Their cytotoxicity is mainly attributed to DNA intercalation, interference with topoisomerase activity, and induction of double-stranded DNA breaks. Since modification of anthracyclines can profoundly affect their pharmacological properties we attempted to elucidate the mechanism of action, and identify possible molecular targets, of bis-anthracycline WP760 which previously demonstrated anti-melanoma activity at low nanomolar concentrations. We studied the effect of WP760 on several human melanoma cell lines derived from tumors in various development stages and having different genetic backgrounds. WP760 inhibited cell proliferation (IC

Pezuk JA, Brassesco MS, de Oliveira RS, et al.
PLK1-associated microRNAs are correlated with pediatric medulloblastoma prognosis.
Childs Nerv Syst. 2017; 33(4):609-615 [PubMed] Related Publications
PURPOSE: Medulloblastoma (MB) is the most common malignant tumor of the central nervous system (CNS) in children. Despite its relative good survival rates, treatment can cause long time sequels and may impair patients' lifespan and quality, making the search for new treatment options still necessary. Polo like kinases (PLKs) constitute a five-member serine/threonine kinases family (PLK 1-5) that regulates different stages during cell cycle. Abnormal PLKs expression has been observed in several cancer types, including MB. As gene regulators, miRNAs have also been described with variable expression in cancer.
METHODS: We evaluated gene expression profiles of all PLK family members and related miRNAs (miR-100, miR-126, miR-219, and miR-593*) in MB cell lines and tumor samples.
RESULTS: RT-qPCR analysis revealed increased levels of PLK1-4 in all cell lines and in most MB samples, while PLK5 was found underexpressed. In parallel, miR-100 was also found upregulated while miR-129, miR-216, and miR-593* were decreased in MB cell lines. Variable miRNAs expression patterns were observed in MB samples. However, a correlation between miR-100 and PLK4 expression was observed, and associations between miR-100, miR-126, and miR-219 expression and overall and event free survival were also evinced in our cohort. Moreover, despite the lack of association with clinico-pathological features, when comparing primary tumors to those relapsed, we found a consistent decrease on PLK2, miR-219, and miR-598* and an increase on miR-100 and miR-126.
CONCLUSION: Specific dysregulation on PLKs and associated miRNAs may be important in MB and can be used to predict prognosis. Although miRNAs sequences are fundamental to predict its target, the cell type may also be consider once that mRNA repertoire can define different roles for specific miRNA in a given cell.

Gümus M, Ozgur A, Tutar L, et al.
Design, Synthesis, and Evaluation of Heat Shock Protein 90 Inhibitors in Human Breast Cancer and Its Metastasis.
Curr Pharm Biotechnol. 2016; 17(14):1231-1245 [PubMed] Related Publications
BACKGROUND: Despite development of novel cancer drugs, invasive ductal breast carcinoma and its metastasis are still highly morbid. Therefore, new therapeutic approaches are being developed and Hsp90 is an important target for drug design. For this purpose, a series of benzodiazepine derivatives were designed and synthesized as novel Hsp90 inhibitor.
METHODS: Benzodiazepine derivatives anticancer activities were determined by XTT cell proliferation assay against human breast cancer cell line (MCF-7). Effects of the compounds on endothelial function were monitored on human vascular endothelium (HUVEC) cell line as well. In order to determine the anti-proliferative mechanism of the compounds, in silico molecular docking studies were performed between Hsp90 ATPase domain and the benzodiazepine derivatives. Further, these compounds perturbation on Hsp90 ATPase function were tested. Fluorescence binding experiments showed that the derivatives bind Hsp90 effectively. Expression analysis of known cancer drug target genes by PCR array experiments suggest that the benzodiazepine derivatives have remarkable anticancer activity.
RESULTS: A representative Benzodiazepine derivative D5 binds Hsp90 with Kd value of 3,93 μM and with estimated free energy of binding -7.99 (kcal/mol). The compound decreases Hsp90 ATPase function and inhibit Hsp90 client protein folding activity. The compound inhibits expression of both Hsp90 isoforms and key proteins (cell cycle receptors; PLK2 and TERT, kinases; PI3KC3 and PRKCE, and growth factors; IGF1, IGF2, KDR, and PDGFRA) on oncogenic pathways.
CONCLUSION: Benzodiazepine derivatives presented here display anticancer activity. The compounds effect on both breast cancer and endothelial cell lines show their potential as drug templates to inhibit breast cancer and its metastasis.

Bi XW, Wang H, Zhang WW, et al.
PD-L1 is upregulated by EBV-driven LMP1 through NF-κB pathway and correlates with poor prognosis in natural killer/T-cell lymphoma.
J Hematol Oncol. 2016; 9(1):109 [PubMed] Free Access to Full Article Related Publications
BACKGROUND: Natural killer/T-cell lymphoma (NKTCL) is an Epstein-Barr virus (EBV)-associated, highly aggressive lymphoma. Treatment outcome remains sub-optimal, especially for advanced-stage or relapsed diseases. Programmed cell death receptor 1 (PD-1) and PD ligand 1 (PD-L1) have become promising therapeutic targets for various malignancies, but their role in the pathogenesis and their interactions with EBV in NKTCL remains to be investigated.
METHODS: Expression of PD-L1 was measured in NK-92 (EBV-negative) and SNK-6 (EBV-positive) cells by western blot, quantitative real-time PCR and enzyme-linked immunosorbent assay, and flow cytometry, respectively. Latent membrane protein 1 (LMP1)-harboring lentiviral vectors were transfected into NK-92 cells to examine the correlation between LMP1 and PD-L1 expression. Proteins in the downstream pathways of LMP1 signaling were measured in NK-92 cells transfected with LMP1-harboring or negative control vectors as well as in SNK-6 cells. PD-L1 expression on tumor specimens and serum concentration of soluble PD-L1 were collected in a retrospective cohort of patients with Ann Arbor stage I~II NKTCL, and their prognostic significance were analyzed.
RESULTS: Expression of PD-L1 was significantly higher in SNK-6 cells than in NK-92 cells, at both protein and mRNA levels. Expression of PD-L1 was remarkably upregulated in NK-92 cells transfected with LMP1-harboring lentiviral vectors compared with those transfected with negative control vectors. Proteins in the MAPK/NF-κB pathway were upregulated in LMP1-expressing NK-92 cells compared with the negative control. Selective inhibitors of those proteins induced significant downregulation of PD-L1 expression in LMP1-expressing NK-92 cells as well as in SNK-6 cells. Patients with a high concentration of serum soluble PD-L1 (≥3.4 ng/ml) or with a high percentage of PD-L1 expression in tumor specimens (≥38 %) exhibited significantly lower response rate to treatment and remarkably worse survival, compared with their counterparts. A high concentration of serum soluble PD-L1 and a high percentage of PD-L1 expression in tumor specimens were independent adverse prognostic factors among patients with stage I~II NKTCL.
CONCLUSIONS: PD-L1 expression positively correlated LMP1 expression in NKTCL, which was probably mediated by the MAPK/NF-κB pathway. PD-L1 expression in serum and tumor tissues has significant prognostic value for early-stage NKTCL.

Zhao HB, Zhang XF, Shi F, et al.
Comparison of the expression of human equilibrative nucleotide transporter 1 (hENT1) and ribonucleotide reductase subunit M1 (RRM1) genes in seven non-Hodgkin lymphoma cell lines.
Genet Mol Res. 2016; 15(2) [PubMed] Related Publications
We investigated the variability in the expression of human equilibrative nucleoside transporter 1 (hENT1) and ribonucleotide reductase subunit M1 (RRM1) in non-Hodgkin lymphoma cell lines. hENT1 and RRM1 mRNA expression levels in natural killer (NK) cells and seven non-Hodgkin lymphoma cell lines (YTS, SNK-6, Jeko-1, ly-1, Raji, Karpas, and Jurket) were studied using reverse-transcription quantitative real-time polymerase chain reaction (RT-qPCR) and the results were compared using the Student t-test. mRNA expression of hENT1 was detectable in YTS, SNK-6, Jeko-1, ly-1, Raji, Karpas, Jurket, and NK cells, which revealed variability in gene expression. There were significant differences in the mRNA expression values of hENT1 (P = 0.021) and RRM1 (P = 0.002) compared to those in NK cells. mRNA expression of both hENT1 and RRM1 was closely associated with non-Hodgkin lymphoma cell proliferation. Differential expression analysis of hENT1 and RRM1 in non-Hodgkin lymphoma cell lines may provide novel drug leads for precision medicine.

Liu F, Zhang S, Zhao Z, et al.
MicroRNA-27b up-regulated by human papillomavirus 16 E7 promotes proliferation and suppresses apoptosis by targeting polo-like kinase2 in cervical cancer.
Oncotarget. 2016; 7(15):19666-79 [PubMed] Free Access to Full Article Related Publications
The infection with high-risk human papillomavirus is linked to cervical cancer, nevertheless, the role of miRNAs regulated by HPV oncogenes in cancer progression remain largely unknown. Here, we knocked down endogenous E6/E7 in HPV16-positive CaSki cell lines, screened differences in miRNA expression profile with control using miRNA array. 38 miRNAs were down-regulated and 6 miRNAs were up-regulated in the E6/E7 silenced CaSki cells (>2-fold changes with P <0.05). The levels of miR-27b, miR-20a, miR-24, miR-93, and miR-106b were verified by qPCR in E6/E7 silenced CaSki and SiHa cells. MiR-27b, up-regulated by E7, promoted CaSki and SiHa cell proliferation and invasion, inhibit paclitaxel-induced apoptosis. Dual-luciferase experiment confirmed miR-27b down-regulated its target gene PLK2 through the "seed regions". The tumor suppressor PLK2 inhibited SiHa cell proliferation, reduced cell viability, and promoted paclitaxel/cisplatin -induced apoptosis. Furthermore, DGCR8 was found to mediate the up-regulation of miR-27b by HPV16 E7. Our study demonstrated that HPV16 E7 could increase DGCR8 to promote the generation of miR-27b, which accelerated cell proliferation and inhibited paclitaxel-induced cell apoptosis through down-regulating PLK2. These findings provide an insight into the interaction network of viral oncogene, miR-27b and PLK2, and support the potential strategies using antisense nucleic acid of miR-27b for therapy of cervical cancer in the future.

Kim SJ, Kim JH, Ki CS, et al.
Epstein-Barr virus reactivation in extranodal natural killer/T-cell lymphoma patients: a previously unrecognized serious adverse event in a pilot study with romidepsin.
Ann Oncol. 2016; 27(3):508-13 [PubMed] Related Publications
BACKGROUND: Romidepsin, a histone deacetylase (HDAC) inhibitor, has been approved for the treatment of relapsed and refractory peripheral T-cell lymphoma. However, the efficacy and safety of romidepsin has never been studied in patients with relapsed or refractory extranodal natural killer (NK)/T-cell lymphoma (ENKTL).
PATIENTS AND METHODS: We conducted an open-label, prospective pilot study to evaluate the efficacy and feasibility of romidepsin in the treatment of patients with ENKTL. The treatment was intravenous infusion of romidepsin (14 mg/m(2)) for 4 h on days 1, 8, and 15 of a 28-day cycle, and was repeated until disease progression or the occurrence of unacceptable toxicity.
RESULTS: A total of five patients enrolled on to this pilot study. However, three patients developed fever and elevated liver enzyme and bilirubin levels immediately after their first administration of romidepsin. We suspected that these events were associated with Epstein-Barr virus (EBV) reactivation because of the rapidly elevated EBV DNA titers in blood from these patients. An in vitro study with the ENKTL cell line SNK-6 cells also showed that HDAC inhibitors including romidepsin increased the copy number of EBV DNA in a dose-dependent manner. These findings suggested that romidepsin-induced histone acetylation reversed the repressed state of the genes required for EBV reactivation and that romidepsin treatment may have caused EBV reactivation in EBV-infected tumor cells in ENKTL patients. Therefore, we discontinued the enrollment of patients into this pilot study.
CONCLUSIONS: Our study suggests that the use of romidepsin may cause severe EBV reactivation in patients with ENKTL.

Hu ZB, Liao XH, Xu ZY, et al.
PLK2 phosphorylates and inhibits enriched TAp73 in human osteosarcoma cells.
Cancer Med. 2016; 5(1):74-87 [PubMed] Free Access to Full Article Related Publications
TAp73, a member of the p53 tumor suppressor family, can substitute for p53 function, especially in p53-null and p53-mutant cells. However, TAp73 enrichment and phosphorylation change its transcriptional activity. Previously, we found that the antitumor function of TAp73 was reactivated by dephosphorylation. Polo-like kinase 2 (PLK2) plays an important role in bone development. Using a biological information database and phosphorylation prediction software, we hypothesized that PLK2 phosphorylates TAp73 and inhibits TAp73 function in osteosarcomas. Actually,we determined that PLK2 physically binds to and phosphorylates TAp73 when TAp73 protein abundance is up-regulated by cisplatin. PLK2-phosphorylated TAp73 at residue Ser48 within the TA domain; phosphorylation of TAp73 was abolished by mutating this residue. Moreover, PLK2 inhibition combined with cisplatin treatment in osteosarcoma Saos2 cells up-regulated p21 and puma mRNA expression to a greater extent than cisplatin treatment alone. Inhibiting PLK2 in TAp73-enriched Saos2 cells resulted in inhibited cell proliferation, increased apoptosis, G1 phase arrest, and decreased cell invasion. However, these changes did not occur in TAp73 knockdown Saos2 cells. In conclusion, these findings reveal a novel PLK2 function in the phosphorylation of TAp73, which prevents TAp73 activity in osteosarcoma cells. Thereby, this research provides an insight into the clinical treatment of malignant tumors overexpressing TAp73.

Gee HE, Buffa FM, Harris AL, et al.
MicroRNA-Related DNA Repair/Cell-Cycle Genes Independently Associated With Relapse After Radiation Therapy for Early Breast Cancer.
Int J Radiat Oncol Biol Phys. 2015; 93(5):1104-14 [PubMed] Related Publications
PURPOSE: Local recurrence and distant failure after adjuvant radiation therapy for breast cancer remain significant clinical problems, incompletely predicted by conventional clinicopathologic markers. We had previously identified microRNA-139-5p and microRNA-1274a as key regulators of breast cancer radiation response in vitro. The purpose of this study was to investigate standard clinicopathologic markers of local recurrence in a contemporary series and to establish whether putative target genes of microRNAs involved in DNA repair and cell cycle control could better predict radiation therapy response in vivo.
METHODS AND MATERIALS: With institutional ethics board approval, local recurrence was measured in a contemporary, prospectively collected series of 458 patients treated with radiation therapy after breast-conserving surgery. Additionally, independent publicly available mRNA/microRNA microarray expression datasets totaling >1000 early-stage breast cancer patients, treated with adjuvant radiation therapy, with >10 years of follow-up, were analyzed. The expression of putative microRNA target biomarkers--TOP2A, POLQ, RAD54L, SKP2, PLK2, and RAG1--were correlated with standard clinicopathologic variables using 2-sided nonparametric tests, and to local/distant relapse and survival using Kaplan-Meier and Cox regression analysis.
RESULTS: We found a low rate of isolated local recurrence (1.95%) in our modern series, and that few clinicopathologic variables (such as lymphovascular invasion) were significantly predictive. In multiple independent datasets (n>1000), however, high expression of RAD54L, TOP2A, POLQ, and SKP2 significantly correlated with local recurrence, survival, or both in univariate and multivariate analyses (P<.001). Low RAG1 expression significantly correlated with local recurrence (multivariate, P=.008). Additionally, RAD54L, SKP2, and PLK2 may be predictive, being prognostic in radiation therapy-treated patients but not in untreated matched control individuals (n=107; P<.05).
CONCLUSIONS: Biomarkers of DNA repair and cell cycle control can identify patients at high risk of treatment failure in those receiving radiation therapy for early breast cancer in independent cohorts. These should be further investigated prospectively, especially TOP2A and SKP2, for which targeted therapies are available.

Zhang X, Zhao L, Li X, et al.
ATP-binding cassette sub-family C member 4 (ABCC4) is overexpressed in human NK/T-cell lymphoma and regulates chemotherapy sensitivity: Potential as a functional therapeutic target.
Leuk Res. 2015; 39(12):1448-54 [PubMed] Related Publications
Nasal-type natural killer/T-cell (NK/T-cell) lymphomas are subtypes of non-Hodgkin's lymphoma (NHL), which are typically more clinically aggressive. There is, however relatively little understanding of nasal-type NK/T-cell lymphoma molecular pathogenesis. Thus, in this study we applied RNA sequencing to systematically screen for altered gene expression in human NK/T-cell lymphoma cell lines YTS and SNK-6 versus normal NK cells. We found that ATP-binding cassette sub-family C Member 4 (ABCC4) levels were significantly upregulated both in human NK/T-cell lymphoma YTS and SNK-6 cells, as compared with normal NK cells. These expression levels were further confirmed by real-time PCR. Protein levels of ABCC4 were also significantly higher in YTS and SNK-6 cells as compared with normal NK cells. Clinically relevant, ABCC4 expression levels were significantly higher in human NK/T-cell lymphoma tissues as compared with control nasal mucosa tissues, confirmed by immunohistochemical staining. In addition, we explored the biological function of such ABCC4 upregulation. Overexpression of ABCC4 by lentivirus transfection induced chemotherapy resistance to epirubicin (EPI) and cisplatin (DDP) in YTS cells. In contrast, knockdown of ABCC4 expression by shRNA contributed to chemotherapy sensitivity by both EPI and DDP. Furthermore, overexpression of ABCC4 inhibited, while downregulation of ABCC4 increased, YTS cell apoptosis following treatment by EPI or DDP. Therefore, the present study identified ABCC4 to be overexpressed in human NK/T-cell lymphoma cells, to regulate chemotherapy sensitivity to EPI and DDP, and possibly to be a functional therapeutic target. These findings may provide a basic rationale for new approaches in the effort to develop anti-tumor therapeutics for NK/T-cell lymphoma.

Bhullar KS, Jha A, Rupasinghe HP
Novel carbocyclic curcumin analog CUR3d modulates genes involved in multiple apoptosis pathways in human hepatocellular carcinoma cells.
Chem Biol Interact. 2015; 242:107-22 [PubMed] Related Publications
Anticancer activity of a novel curcumin analog (E)-2-(4-hydroxy-3-methoxybenzylidene)-5-((E)-3-(4-hydroxy-3-methoxyphenyl)acryloyl)cyclopentanone (CUR3d) was studied using a human hepatocellular carcinoma cell line (HepG2). The results showed that CUR3d completely inhibits the tumor cell proliferation in a dose- and time-dependent manner. CUR3d at 100 μmol/L activated the pro-apoptotic caspase-3 along with downregulation of anti-apoptotic BIRC5 and Bcl2. CUR3d treatment controlled the cancer cell growth by downregulating the expression of PI3K/Akt (Akt1, Akt2) pathway along with NF-κB. CUR3d down-regulated the members of epidermal growth receptor family (EGFR, ERBB3, ERBB2) and insulin like growth receptors (IGF1, IGF-1R, IGF2). This correlated with the downregulation of G-protein (RHOA, RHOB) and RAS (ATF2, HRAS, KRAS, NRAS) pathway signaling. CUR3d also arrested cell cycle via inhibition of CDK2, CDK4, CDK5, CDK9, MDM2, MDM4 and TERT genes. Cell cycle essential aurora kinases (AURKα, AURKβ) and polo-like kinases (PLK1, PLK2, PLK3) were also modulated by CUR3d. Topoisomerases (TOP2α, TOP2β), important factors in cancer cell immortality, as well as HIF-1α were downregulated following CUR3d treatment. The expression of protein kinase-C family (PRKC-A, PRKC-D, PRKC-E) was also attenuated by CUR3d. The downregulation of histone deacetylases (Class I, II, IV) and PARP I further strengthened the anticancer efficacy of CUR3d. Downregulation of carcinogenic cathepsins (CTSB, CTSD) and heat shock proteins exhibited CUR3d's potency as a potential immunological adjuvant. Finally, the non-toxic manifestation of CUR3d in healthy liver and lung cells along with downregulation of drug resistant gene ABCC1 further warrant need for advance investigations.

Sun L, Zhao Y, Shi H, et al.
LMP1 promotes nasal NK/T-cell lymphoma cell function by eIF4E via NF-κB pathway.
Oncol Rep. 2015; 34(6):3264-71 [PubMed] Related Publications
Nasal natural killer T-cell lymphoma (NKTL) is a highly malignant tumor that is closely associated with Epstein-Barr virus (EBV) infection. Latent membrane protein 1 (LMP1) is encoded by EBV and plays an important role in EBV-induced cell transformation. Therefore, we assessed the function of LMP1 as a stimulant of NKTL progression and the underlying mechanism. A human EBV-positive NKTL cell line (SNK-6) was transfected with pcDNA3.1-LMP1, LV-LMP1 shRNA or LV-eukaryotic translation initiation factor 4E (eIF4E)-shRNA. Then, 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) assay was used to assess the proliferation of SNK-6 cells, and cell migration and invasion were analyzed by transwell chamber assay. Flow cytometry was used to analyze the cell cycle and apoptosis. The results showed LMP1 was highly expressed in SNK-6 cells compared with control groups. Following pretreatment with LMP1 shRNA, the proliferation of SNK-6 cells was inhibited and resulted in a G0/G1 phase arrest. A reduction in invasion and migration was also observed. LMP1 silencing promoted cell apoptosis. Further mechanistic analysis suggested that LMP1 overexpression induced the expression of eIF4E, while eIF4E-shRNA dramatically attenuated the increase in cell proliferation, invasion, migration and the inhibition of apoptosis triggered by LMP-1 upregulation. Moreover, the effect of LMP1 on eIF4E expression was mediated by the NF-κB pathway. Therefore, this finding may provide a potential target against NKTL.

Fontebasso AM, Shirinian M, Khuong-Quang DA, et al.
Non-random aneuploidy specifies subgroups of pilocytic astrocytoma and correlates with older age.
Oncotarget. 2015; 6(31):31844-56 [PubMed] Free Access to Full Article Related Publications
Pilocytic astrocytoma (PA) is the most common brain tumor in children but is rare in adults, and hence poorly studied in this age group. We investigated 222 PA and report increased aneuploidy in older patients. Aneuploid genomes were identified in 45% of adult compared with 17% of pediatric PA. Gains were non-random, favoring chromosomes 5, 7, 6 and 11 in order of frequency, and preferentially affecting non-cerebellar PA and tumors with BRAF V600E mutations and not with KIAA1549-BRAF fusions or FGFR1 mutations. Aneuploid PA differentially expressed genes involved in CNS development, the unfolded protein response, and regulators of genomic stability and the cell cycle (MDM2, PLK2),whose correlated programs were overexpressed specifically in aneuploid PA compared to other glial tumors. Thus, convergence of pathways affecting the cell cycle and genomic stability may favor aneuploidy in PA, possibly representing an additional molecular driver in older patients with this brain tumor.

Wu T, Wang S, Wu J, et al.
Icaritin induces lytic cytotoxicity in extranodal NK/T-cell lymphoma.
J Exp Clin Cancer Res. 2015; 34:17 [PubMed] Free Access to Full Article Related Publications
BACKGROUND: Extranodal NK/T-cell lymphoma (ENKL) is an aggressive hematological malignancy associated with Epstein-Barr virus (EBV) infection. It is often resistant to conventional chemotherapy and has a poor prognosis. Icaritin, a compound derived from Chinese herbal medicine, Herba Epimedii, has been reported to exert antitumor effects on a variety of cancer cell lines. In the present study, we investigated the cytotoxic effects of Icaritin on the two EBV-positive ENKL cell lines SNK-10 and SNT-8, along with the underlying molecular mechanisms.
METHODS: ENKL cell lines SNK-10 and SNT-8 were exposed to different concentrations of Icaritin for the indicated time. Treated cells were analyzed for cell proliferation, cell cycle, and cell apoptosis. Phosphorylation of Stat3 and Akt proteins in signaling pathways and the EBV-encoded LMP1 proteins were measured by Western blot. Expression of EBV genes was assessed by Real-Time PCR.
RESULTS: Our results showed that Icaritin dose-dependently inhibits ENKL cell proliferation and induces apoptosis and cell cycle arrest at G2/M phase. Additionally, Icaritin upregulates Bax, downregulates Bcl-2 and pBad, and activates caspase-3 and caspase-9. The anti-proliferative and pro-apoptotic effects of Icaritin are likely mediated by inhibition of Stat3 and Akt pathways through LMP1 downregulation. Importantly, Icaritin induces EBV lytic gene expression in ENKL cells, and the combination of Icaritin and the antiviral drug ganciclovir (GCV) is more effective in inducing ENKL cells apoptosis than Icaritin or GCV alone.
CONCLUSIONS: These findings indicate that EBV-targeted approaches may have significant therapeutic potential for ENKL treatment.

Sun L, Zhao Y, Shi H, et al.
LMP-1 induces survivin expression to inhibit cell apoptosis through the NF-κB and PI3K/Akt signaling pathways in nasal NK/T-cell lymphoma.
Oncol Rep. 2015; 33(5):2253-60 [PubMed] Related Publications
The latent membrane protein-1 (LMP-1) is essential for Epstein-Barr virus (EBV)-induced nasal natural killer/T-cell lymphoma (NKTL). The aim of the present study was to evaluate the role of LMP-1 in NKTL. Two human EBV-positive NKTL cell lines (SNK-6 and SNT-8) were transfected with pcDNA3.1-LMP-1 or LMP-1 siRNA. Compared with the blank control, the cell apoptosis rates were decreased by 10.31 and 12.05% after pcDNA3.1-LMP-1 transfection and increased by 41.48 and 35.63% after lentiviral LMP-1 siRNA infection in the SNK-6 and SNT-8 cells. Survivin expression was induced by LMP-1, and the effect was attenuated by inhibitors of survivin, NF-κB and PI3K/Akt. Reduction in cell apoptosis by LMP-1 was also inhibited by inhibitors of survivin, NF-κB and PI3K/Akt. For the in vivo assay, tumor-bearing mice were established by subcutaneous injection with differentially treated SNT-8 cells into the back of the nude mice, and the tumor growth in the different groups was recorded. The results revealed that tumor formation and growth were also inhibited by treatment with survivin, NF-κB and PI3K/Akt inhibitors. Collectively, LMP-1-induced survivin expression inhibited cell apoptosis through the NF-κB and PI3K/Akt pathways, and survivin may be a new target for the treatment of NKTL induced by EBV.

Liu LY, Wang W, Zhao LY, et al.
Silencing of polo-like kinase 2 increases cell proliferation and decreases apoptosis in SGC-7901 gastric cancer cells.
Mol Med Rep. 2015; 11(4):3033-8 [PubMed] Related Publications
Polo‑like kinase 2 (PLK2) is a serine/threonine protein kinase, which has vital roles during mitosis and the centrosome cycle. In acute myeloblastic leukemia and hepatocarcinogenesis, PLK2 acts as a tumor suppressor; however, the function of PLK2 in gastric cancer remains to be elucidated. In the present study, PLK2 was overexpressed in gastric cancer tissues and three types of gastric cancer cells, SGC‑7901, MKN‑45 and BGC‑823. Transfection of SGC‑7901 gastric cancer cells with small interfering (si)RNA against PLK2 exerted no effect on the ratio of cells at different stages of the cell cycle compared with that of the untransfected and control siRNA‑transfected cells. In addition, silencing of PLK2 significantly enhanced the growth of SGC‑7901 cells through inhibiting apoptosis. Furthermore, apoptosis‑associated genes Bax and caspase 3 were found to be downregulated at the protein level. In conclusion, these results suggested that PLK2 may act as a tumor suppressor in gastric cancer, therefore indicating its therapeutic potential.

Ji WG, Zhang XD, Sun XD, et al.
miRNA-155 modulates the malignant biological characteristics of NK/T-cell lymphoma cells by targeting FOXO3a gene.
J Huazhong Univ Sci Technolog Med Sci. 2014; 34(6):882-888 [PubMed] Related Publications
This study investigated the effects of miRNA-155 on malignant biological characteristics of NK/T-cell lymphoma cell lines and the possible mechanism. The expression of miRNA-155 was detected in lymphoma cell lines from different sources (SNK-6, YTS, Jurkat and DOHH2) by real-time PCR. Lentiviral vectors (pLL3.7) that could overexpress or downexpress miRNA-155 were constructed. Recombinant lentiviral particles were prepared and purified, and their titers determined. The expression of miRNA-155 in the infected SNK-6 cells and the cell proliferation were detected by PCR and CCK-8, respectively. Flow cytometry was used to determine the apoptosis of infected SNK-6 cells. The target of miRNA155 was predicted from Targetscan website. The effect of miRNA155 on FOXO3a expression was examined by Western blotting. The results showed that among the human NK/T-cell lymphoma cell lines SNK-6, YTS, Jurkat and DOHH2, the expression of miRNA-155 was highest in SNK-6. The infection efficiency of the recombinant lentivirus in SNK-6 was more than 70% at multiplicity of infection (MOI) of 100. The expression of miRNA-155 was significantly increased in SNK-6 cells infected by lentivirus vectors with high expression of miRNA-155 (4 times higher than the control group), and profoundly decreased in those infected with lentiviruses with low expression of miRNA-155. The proliferation of letivirus-infected SNK-6 cells was decreased as the expression of miRNA-155 reduced. The apoptosis rate was increased with the reduction in the expression of miRNA-155. FOXO3a was found to be a possible target of miRNA155, as suggested by Targetscan website. Western blotting showed that the expression of FOXO3a was significantly elevated in SNK-6 cells with miRNA-155 inhibition. It was concluded that reduction in miRNA-155 expression can inhibit the proliferation of SNK-6 lymphoma cells and promote their apoptosis, which may be associated with regulation of FOXO3a gene.

Ward A, Sivakumar G, Kanjeekal S, et al.
The deregulated promoter methylation of the Polo-like kinases as a potential biomarker in hematological malignancies.
Leuk Lymphoma. 2015; 56(7):2123-33 [PubMed] Related Publications
Deregulation of Polo-like kinase (PLK) transcription via promoter methylation results in perturbations at the protein level, which has been associated with oncogenesis. Our objective was to further characterize the methylation profile for PLK1-4 in bone marrow aspirates displaying blood neoplasms as well as in cells grown in vitro. Clinically, we have determined that more than 70% of lymphoma and myelodysplastic syndrome (MDS)/leukemia bone marrow extracts display a hypermethylated PLK4 promoter region in comparison to the normal. Decreased PLK4 protein expression due to promoter hypermethylation was negatively correlated with JAK2 overexpression, a common occurrence in hematological malignancies. In vitro examination of the PLKs under biologically relevant condition of 5% O2 revealed that the highly conserved PLKs respond to lower oxygen tension at both the DNA and the protein level. These findings suggest that PLK promoter methylation status correlates with disease and tumorigenesis in blood neoplasms and could serve as a biomarker.

Tian Y, Fu S, Qiu GB, et al.
MicroRNA-27a promotes proliferation and suppresses apoptosis by targeting PLK2 in laryngeal carcinoma.
BMC Cancer. 2014; 14:678 [PubMed] Free Access to Full Article Related Publications
BACKGROUND: miRNA-27a has been confirmed as an important regulator in carcinogenesis and other pathological processes. Whether and how it plays a role in the laryngeal carcinoma is unknown.
METHODS: Mature miRNA-27a expression in laryngeal cancer was detected by qRT-PCR. Gain-of-function studies using mature miR-27a were performed to investigate cell proliferation and apoptosis in the Hep2 cells. In silico database analysis and luciferase reporter assay were applied to predict and validate the direct target, respectively. Loss-of-function assays were performed to investigate the functional significance of the miR-27a target gene. qRT-PCR and Western blot were used to evaluate mRNA and protein levels of the target, respectively.
RESULTS: miR-27a was significantly up-regulated in the laryngeal tumor tissues compared to the adjacent non-tumor tissues. In silico database analysis result revealed that PLK2 is a potential target of miR-27a. luciferase reporter assay result showed the direct inhibition of miR-27a on PLK2-3'UTR. In the cases with miR-27a up-regulation, PLK2 protein expression level was significantly lower in cancer tissues than that in the adjacent non-tumor tissues, which showed a negative correlation with miR-27a expression level. Both miR-27a and knockdown of PLK2 caused the increase of the cell viability and colony formation and inhibition of the late apoptosis in the Hep2 cell lines. Moreover, miR-27a but not PLK2 also repressed the early apoptosis in the Hep2 cells. Additionally, no alteration of the Hep2 cell cycle induced by miR-27a was detected.
CONCLUSIONS: miR-27a acts as an oncogene in laryngeal squamous cell carcinoma through down-regulation of PLK2 and may provide a novel clue into the potential mechanism of LSCC oncogenesis or serve as a useful biomarker in diagnosis and therapy in laryngeal cancer.

Liu LY, Wang W, Zhao LY, et al.
Mir-126 inhibits growth of SGC-7901 cells by synergistically targeting the oncogenes PI3KR2 and Crk, and the tumor suppressor PLK2.
Int J Oncol. 2014; 45(3):1257-65 [PubMed] Related Publications
MicroRNA (miRNA)-126 (miR-126) was reported to be downregulated and to act as a tumor suppressor in cancers of the lung, cervix, bladder and prostate. However, the functions of miR-126 in gastric cancer appear to be diverse and are largely unknown. MiR-126 was reported to act as a tumor suppressor by targeting the Crk gene, or as an oncogene by targeting the SOX2 gene in gastric cancer. We identified that the expression of miR-126 was decreased in gastric cancer cell lines and tissues. PLK2, a tumor suppressor gene, was directly regulated by miR-126 in SGC-7901 cells. Overexpression of miR-126 not only suppressed the growth and clone formation of SGC-7901 cells, but also induced apoptosis in vitro, whereas inhibition of miR-126 slightly promoted SGC-7901 cell proliferation. The cell cycle was not affected by miR-126. Moreover, miR-126 suppressed tumor growth in vivo in a xenograft model. PLK2, PI3KR2 and Crk were regulated by miR-126 in SGC-7901 cells. We infer that the functions of miR-126 in gastric cancer depend on synergistic targeting balance between oncogenes and anti-oncogenes. Our study indicates that miR-126 is a tumor suppressor, which in the future may become a therapeutic target for gastric cancer.

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