circRNA_141539 can serve as an oncogenic factor in esophageal squamous cell carcinoma by sponging miR-4469 and activating CDK3 gene.

The abnormal expression and regulation of circular RNA (circRNA) is involved in the occurrence and development of a variety of tumors. The current study aimed to determine the role of circRNA_141539 in esophageal squamous cell carcinoma (ESCC). CircRNA_141539 expression in ESCC was detected via circRNA chip analysis and verified via reverse transcription-quantitative PCR. Associations between circRNA_141539, patient clinicopathological characteristics and prognosis were also statistically analyzed. Additionally, the effects of circRNA_141539 on ESCC cell proliferation and invasion were assessed. A dual-luciferase assay was performed to analyze the interaction between circRNAs, microRNAs (miRs) and mRNAs. The results revealed that circRNA_141539 was significantly up-regulated in patients with ESCC. Furthermore, high circRNA_141539 expressions were significantly associated with TNM stage, differentiation and poor prognosis, revealing high diagnostic value (P<0.05). Furthermore, circRNA_141539 overexpression promoted cell proliferation and invasion, while circRNA_141539 silencing inhibited cell proliferation and invasion (P<0.05). The dual-luciferase reporter assay identified that circRNA_141539 directly binds to miR-4469 and also revealed that cyclin-dependent kinase-3 (CDK3) was negatively regulated by miR-4469. The results indicated that circRNA_141539 served as an oncogenic factor in ESCC by sponging miR-4469 and activating CDK3 expression. circRNA_141539 may present as a novel diagnostic and prognostic biomarker and a therapeutic target for patients with ESCC.

Norcantharidin regulates ERα signaling and tamoxifen resistance via targeting miR-873/CDK3 in breast cancer cells.

MiR-873/CDK3 has been shown to play a critical role in ERα signaling and tamoxifen resistance. Thus, targeting this pathway may be a potential therapeutic approach for the treatment of ER positive breast cancer especially tamoxifen resistant subtype. Here we report that Norcantharidin (NCTD), currently used clinically as an ani-cancer drug in China, regulates miR-873/CDK3 axis in breast cancer cells. NCTD decreases the transcriptional activity of ERα but not ERß through the modulation of miR-873/CDK3 axis. We also found that NCTD inhibits cell proliferation and tumor growth and miR-873/CDK3 axis mediates cell proliferation suppression of NCTD. More important, we found that NCTD sensitizes resistant cells to tamoxifen. NCTD inhibits tamoxifen induced the transcriptional activity as well ERα downstream gene expressions in tamoxifen resistant breast cancer cells. In addition, we found that NCTD restores tamoxifen induced recruitments of ERα co-repressors N-CoR and SMRT. Knockdown of miR-873 and overexpression of CDK3 diminish the effect of NCTD on tamoxifen resistance. Our data shows that NCTD regulates ERα signaling and tamoxifen resistance by targeting miR-873/CDK3 axis in breast cancer cells. This study may provide an alternative therapy strategy for tamoxifen resistant breast cancer.

HuR facilitates cancer stemness of lung cancer cells via regulating miR-873/CDK3 and miR-125a-3p/CDK3 axis.

OBJECTIVES: To study the roles and mechanisms of HuR in cancer stem cell maintenance of lung cancer. RESULTS: HuR expression was increased in tumor spheres of lung cancer cells. Knockdown of HuR suppressed spheroid formation and size, inhibited the expression of stemness-related marker, Oct4, Nanog and ALDH in lung cancer cells. Importantly, HuR and CDK3 expressions were increased in lung cancer tissues compared with normal adjacent tissues, and positively correlated. Mechanistically, HuR directly bound to CDK3, and increased CDK3 mRNA stability and expression. Additionally, miR-873 or miR-125a-3p attenuated the promotion of HuR on CDK3 expression and lung cancer stemness. Furthermore, HuR facilitated lung cancer stemness dependent on CDK3 expression. miR-873 or miR-125a-3p level was negatively correlated with HuR and CDK3 expression levels in lung cancer tissues. CONCLUSIONS: HuR facilitates lung cancer stemness via regulating miR-873/CDK3 and miR-125a-3p/CDK3 axis.

miR-125a-3p inhibits ERα transactivation and overrides tamoxifen resistance by targeting CDK3 in estrogen receptor-positive breast cancer.

Tamoxifen (TAM) is a major adjuvant therapy for patients who are diagnosed with estrogen receptor-α (ER)-positive breast cancer; however, TAM resistance occurs often during treatment and the underlying mechanism is unclear. Here, we report that miR-125a-3p inhibits ERα transcriptional activity and, thus, ER+ breast cancer cell proliferation, which causes cell-cycle arrest at the G1/S stage, inducing apoptosis and suppressing tumor growth by targeting cyclin-dependent kinase 3 (CDK3) in vitro and in vivo. In addition, CDK3 and miR-125a-3p expression levels were measured in 37 cancerous tissues paired with noncancerous samples, and their expression levels were negatively associated with miR-125a-3p level. Of interest, miR-125a-3p level is down-regulated in MCF-7 TAM-resistant (TamR) cells. Of more importance, up-regulation of miR-125a-3p resensitizes MCF-7 TamR cells to TAM, which is dependent on CDK3 expression. These results suggest that miR-125a-3p can function as a novel tumor suppressor in ER+ breast cancer by targeting CDK3, which may be a potential therapeutic approach for TamR breast cancer therapy.-Zheng, L., Meng, X., Li, X., Zhang, Y., Li, C., Xiang, C., Xing, Y., Xia, Y., Xi, T. miR-125a-3p inhibits ERα transactivation and overrides tamoxifen resistance by targeting CDK3 in estrogen receptor-positive breast cancer.

HuR promotes breast cancer cell proliferation and survival via binding to CDK3 mRNA.

HuR, a ubiquitously expressed RNA-binding protein, stabilizes mRNA and regulates its translation. HuR expression was increased at all stages of breast cancer and correlated with poor clinical outcome. However, the detailed mechanisms remain unclear. Here we reported that overexpression of HuR increased CDK3 mRNA stability and thus its protein expression in MDA-MB-231 and MCF-7 cells. Mechanistically, CDK3 mRNA was identified as a target of HuR via bioinformatics and RNA binding protein immunoprecipitation (RIP) assays. Furthermore, treatment with HuR shRNA decreased CDK3 expression, inhibited cell proliferation and promoted cell apoptosis in breast cancer. More importantly, overexpression of CDK3 reversed the suppressive effects of HuR knockdown on cell growth in both MDA-MB-231 and MCF-7 cells. Finally, HuR and CDK3 expression levels were positively correlated and significantly up-regulated in breast cancer samples. And overexpression of HuR attenuated the chemotherapeutical efficiency of breast cancer. Therefore, our results indicate that ectopic expression of HuR promotes breast cancer cell proliferation and survival by directly binding to and stabilizing CDK3 mRNA.

CDK3 is a major target of miR-150 in cell proliferation and anti-cancer effect.

MiR-150, a member of small non-coding RNAs, has been proven to dysregulate in different types of tumor and bear on carcinogenesis and cancer prognosis by regulating the expression of a series of gene including utrophin. Given that utrophin can compensate for dystrophin's absence and be regarded as a promising therapeutic target for Duchenne Muscular Dystrophy (DMD), we further detected the deep role of miR-150 in dystrophic muscle. Using a range of bioinformatic, molecular and cell biology techniques, we declared that miR-150 directly targets cyclin-dependent kinase 3 (CDK3) and leads to the regulation of CDK3 gene expression in both muscle-derived and non-muscle cells. The results indicated the expression of miR-150 was upregulated in mdx muscle and closely related to the lower level of CDK3. Transient transfection of miR-150 into cultured C2C12 cells led to significant decrease in cell proliferation, which is partly mediated via the 3'-UTRs of CDK3 mRNA. Targeting of CDK3 could also play a role, at least in part, in the anti-cancer activity suggested for miR-150 in previous studies. Consistently, the analysis of tumor and matched normal lung tissues indicates that miR-150 downregulation in lung tumors correlates with higher CDK3 levels. In addition, miR-150 transfection experiments with cancer-derived cell lines reveal that miR-150-mediated CDK3 suppression directly induces to growth inhibition. Collectively, our results highlight a novel activity for CDK3 in myoblast cell proliferation and confirm CDK3 as a key target that further enhances the tumor suppressor function proposed for miR-150.

miR-214/199a/199a* cluster levels predict poor survival in hepatocellular carcinoma through interference with cell-cycle regulators.

AIMS: To identify the clinical and functional association of miR-214/199a/199a* cluster in human hepatocellular carcinoma (HCC) and to clarify the mechanism of miR-214. METHODS: Kaplan-Meier and Cox proportional regression analyses were used to determine the association of miR-214/199a/199a* cluster levels with the survival of HCC patients. The role of miR-214 in regulating HCC cell proliferation was studied with miR-214 mimics/inhibitor-treated cells. Furthermore, the inhibition effect of miR-214 on E2F2, cyclin-dependent kinase (CDK) 3 and CDK6 expression was assessed in HCC cell lines with miR-214 mimics/inhibitors to increase/decrease miR-214 expression. Direct binding of miR-214 to the 3'-untranslated regions of E2F2, CDK3, and CDK6 was verified by dual-luciferase reporter assay. RESULTS: In analyzing HCC clinical specimens and cell lines, we discovered a uniform decrease in miR-214/199a/199a* expression in comparison with noncancerous tissue or normal liver epithelial cell lines. Higher miR-214 levels were related with improved patient survival. Overexpression of miR-214 in HCC cells inhibited proliferation by inducing G1-S checkpoint arrest. Conversely, RNA interference-mediated silencing of miR-214 promoted cell-cycle progression and accelerated the proliferation of HCC cells. E2F2, CDK3 and CDK6 were each directly targeted for inhibition by miR-214, and restoring their expression reversed miR-214 inhibition of cell-cycle progression. The relationship between expression of miR-214 and its targets was confirmed in HCC tumor xenografts and clinical specimens. CONCLUSIONS: Our results demonstrate that miR-214 has tumor-suppressive activity in HCC through inhibition of E2F2, CDK3 and CDK6.

MiR-873 regulates ERα transcriptional activity and tamoxifen resistance via targeting CDK3 in breast cancer cells.

miRNAs (microRNAs) are frequently and aberrantly expressed in many cancers. MiR-873 has been revealed to be downregulated in colorectal cancer and glioblastoma. However, its function remains unclear. Here we report that miR-873 is downregulated in breast tumor compared with normal tissue. Enforced expression of miR-873 decreases the transcriptional activity of ER (estrogen receptor)-α but not ERß through the modulation of ERα phosphorylation in ER-positive breast cancer cells. We also found that miR-873 inhibits breast cancer cell proliferation and tumor growth in nude mice. Reporter gene assays revealed cyclin-dependent kinase 3 (CDK3) as a direct target of miR-873. CDK3 was shown to be overexpressed in breast cancer and phosphorylate ERα at Ser104/116 and Ser118. Furthermore, we found that Mir-873 inhibits ER activity and cell growth via targeting CDK3. Interestingly, miR-873 was observed to be downregulated in tamoxifen-resistant MCF-7/TamR cells, while CDK3 is overexpressed in these cells. More importantly, re-expression of miR-873 reversed tamoxifen resistance in MCF-7/TamR cells. Our data demonstrate that miR-873 is a novel tumor suppressor in ER-positive breast cancer and a potential therapeutic approach for treatment of tamoxifen-resistant breast cancer.

CDK3 expression and its clinical significance in human nasopharyngeal carcinoma.

The aim of the current study was to investigate the expression of cyclin-dependent kinase 3 (CDK3) in human nasopharyngeal carcinoma (NPC) and to evaluate its association with the clinicopathological characteristics of patients with NPC. CDK3 expression was examined in three NPC cell lines and one nasopharyngeal epithelial cell line by western blot analysis and in 94 specimens of NPC and 40 specimens of inflamed nasopharyngeal tissue by immunohistochemistry staining. CDK3 was overexpressed in the three NPC cell lines, 5-8F, CNE1 and CNE2, compared with the NP-69 nasopharyngeal epithelial cell line, and was primarily expressed in the cytoplasm. The frequency of CDK3 expression was significantly higher in NPC specimens (67%) compared with inflamed nasopharyngeal tissue specimens (12.5%; P<0.001). CDK3 expression was associated with the degree of infiltration, lymph node metastasis and tumor node metastasis clinical staging, respectively, (P<0.001) in patients with NPC. These results revealed that the expression of CDK3 is associated with the progression of NPC, and may be a potential biomarker for prediction of the prognosis of patients with NPC.