To better understand the molecular mechanisms of paclitaxel resistance in ovarian carcinoma, we evaluated the expression of miRNAs using miRNA microarray between human ovarian carcinoma SKOV3 cells and paclitaxel resistant SKOV3-TR30 cells. Results showed that 69 miRNAs were upregulated while 102 miRNAs were downregulated in SKOV3-TR30 cells. Using real-time PCR, we further clarified that miR-17~92 was overexpressed in SKOV3-TR30 cells compared with that in SKOV3 cells. We then established stable virally transduced SKOV3-TR30-m-PTIP-Sponge all SKOV3-TR30 cells and its vector-only control SKOV3-TR30-m-PTIP-GFP cells. Real time-PCR revealed that SKOV3-TR30-m-PTIP-Sponge all cells expressed approximately 6.18-fold lower levels of miR-17~92 compared with the control group. Decreased expression of miR-17~92 resulted in cell cycle arrest in the G2/M phase and growth inhibition. After the transduction, the BIM protein level was increased in SKOV3-TR30 cells and luciferase reporter assays revealed that miR-17~92 binds directly to the 3'-UTR of BIM. Results of luciferase reporter assays accompanied with Western Blot showed that although miR-17~92 binds directly to the 3'-UTR of PTEN, the PTEN protein expression level was upregulated slightly while the result is of no statistical significance. Our results showed that miR-17~92 could be a causal factor of the downregulation of BIM in SKOV3-TR30 cells and thus induce the paclitaxel resistance in SKOV3-TR30 cells.
Ota, A.; Tagawa, H.; Karnan, S.; Tsuzuki, S.; Karpas, A.; Kira, S.; Yoshida, Y.; Seto, M. Identification and characterization of a novel gene, C13orf25, as a target for 13q31-q32 amplification in malignant lymphoma. Cancer Res 2004, 64, 3087–3095.
Tanaka, M.; Grossman, H.B. In vivo gene therapy of human bladder cancer with PTEN suppresses tumor growth; down regulates phosphorylated Akt, and increases sensitivity to doxorubicin. Gene Ther 2003, 10, 1636–1642.
Wu, H.; Cao, Y.; Weng, D.; Xing, H.; Song, X.; Zhou, J.; Xu, G.; Lu, Y.; Wang, S.; Ma, D. Effect of tumor suppressor gene PTEN on the resistance to cisplatin in human ovarian carcinoma cell lines and related mechanisms. Cancer Lett 2008, 271, 260–271.
Baumhoer, D.; Zillmer, S.; Unger, K.; Rosemann, M.; Atkinson, M.J.; Irmler, M.; Beckers, J.; Siggelkow, H.; von Luettichau, I.; Jundt, G.; et al. MicroRNA profiling with correlation to gene expression revealed the oncogenic miR-17~92 cluster to be up-regulated in osteosarcoma. Cancer Genet 2012, 205, 212–219.