Quan Hao

MiR-489 modulates cisplatin resistance in human ovarian cancer cells by targeting Akt3.

MicroRNAs are a conserved class of small noncoding RNA molecules that harbour the capacity to regulate protein-coding gene expression at the post-transcriptional level. In the current study, we show that miR-489 is downregulated in cisplatin (CDDP)-resistant ovarian cancer cells, SKOV3/CDDP and OVCAR3/CDDP cells. MiR-489 overexpression results in an inhibition of SKOV3 and OVCAR3 cell survival and cell growth after CDDP treatment and an induction of cell apoptosis. Inhibition of miR-489 yields the opposite results. In addition, miR-489 overexpression increases the sensitivity of SKOV3/CDDP and OVCAR3/CDDP cells to CDDP and inhibits their colony number. Akt3 is validated as a direct target of miR-489 in SKOV3, OVCAR3, SKOV3/CDDP and OVCAR3/CDDP cells. In addition, miR-489 suppresses Akt3 protein expression by binding sites on its 3′UTR. Knockdown of Akt3 results in a similar effect as that because of miR-489 overexpression; importantly, Akt3 silencing rescues the functions induced by miR-489. Furthermore, we also use the Akt3 inhibitor, MK-2206 2HCl, to determine the role of Akt3 in CDDP resistance. Our study showed that MK-2206 2HCl increased the sensitivity of SKOV3/CDDP and OVCAR3/CDDP cells to CDDP. Taken together, our results indicate that miR-489 inhibited CDDP resistance and cell growth, and promotes apoptosis by suppressing Akt3 expression. Furthermore, the identification of a novel miR-489-based pathway in CDDP-resistant ovarian cancer will facilitate the development of therapeutic strategies.

Folate Intake and Methylenetetrahydrofolate Reductase Gene Polymorphisms as Predictive and Prognostic Biomarkers for Ovarian Cancer Risk

Folic acid and methylenetetrahydrofolate reductase (MTHFR) may affect the development of human cancer. However, few studies have evaluated folate intake and MTHFR in susceptibility to and prognosis of patients with ovarian cancer. We conducted a prospective case-control study in 215 ovarian cancer patients and 218 controls (all Chinese) between Jan. 2004 and Jan. 2007. MTHFR C677T genotyping was done by PCR-RFLP. All patients were followed up until Dec. 2010. We found a 2.43-fold increased risk of ovarian cancer among MTHFR 677TT carriers, and a decreased risk of ovarian cancer in individuals with high folate intake (OR = 0.54, 95% CI = 0.32–0.94). Cox regression survival analysis showed that among the ovarian cancer patients, those carrying the 677TT genotype had a higher risk of death (HR = 2.17, 95% CI = 1.20–4.79), while high folate intake was associated with a lower risk of death (HR = 0.43, 95% CI = 0.33–0.88). Moreover, MTHFR 677CC carriers with higher folate intake showed a lower risk of death from ovarian cancer (HR = 0.32, 95% CI = 0.27–0.82). In summary, high folate intake may lessen susceptibility and improve the prognosis of ovarian cancer patients, while the MTHFR 677TT genotype appears to increase ovarian cancer risk and worsen its prognosis in a Chinese population.

PTEN overexpression improves cisplatin-resistance of human ovarian cancer cells through upregulating KRT10 expression

Multi-drug resistance (MDR) is a common cause of the failure of chemotherapy in ovarian cancer. PTEN, a tumor suppressor gene, has been demonstrated to be able to reverse cisplatin-resistance in ovarian cancer cell line C13K. However, the downstream molecules of PTEN involved in the resistance-reversing effect have not been completely clarified. Therefore, we screened the downstream molecules of PTEN and studied their interactions in C13K ovarian cancer cells using a 3D culture model. Firstly, we constructed an ovarian cancer cell line stably expressing PTEN, C13K/PTEN. MTT assay showed that overexpression of PTEN enhanced the sensitivity of C13K cells to cisplatin, but not to paclitaxel. Then we examined the differently expressed proteins that interacted with PTEN in C13K/PTEN cells with or without cisplatin treatment by co-immunoprecipitation. KRT10 was identified as a differently expressed protein in cisplatin-treated C13K/PTEN cells. Further study confirmed that cisplatin could induce upregulation of KRT10 mRNA and protein in C13K/PTEN cells and there was a directly interaction between KRT10 and PTEN. Forced expression of KRT10 in C13K cells also enhanced cisplatin-induced proliferation inhibition and apoptosis of C13K cells. In addition, KRT10 siRNA blocked cisplatin-induced proliferation inhibition of C13K/PTEN cells. In conclusion, our data demonstrate that KRT10 is a downstream molecule of PTEN which improves cisplatin-resistance of ovarian cancer and forced KRT10 overexpression may also act as a therapeutic method for overcoming MDR in ovarian cancer.