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KPNA2 promotes cell proliferation and tumorigenicity in epithelial ovarian carcinoma through upregulation of c-Myc and downregulation of FOXO3a.

ABSTRACT: Karyopherin alpha 2 (KPNA2), a member of the karyopherin family, has a central role in nucleocytoplasmic transport and is overexpressed in many cancers. Our previous study identified KPNA2 as significantly upregulated in epithelial ovarian carcinoma (EOC), correlating with poor survival of patients. However, the precise mechanism of this effect remains unclear. The aim of the present study was to examine the role of KPNA2 in the proliferation and tumorigenicity of EOC cells, and its clinical significance in tumor progression. Real-time quantitative RT-PCR analysis revealed high expression levels of KPNA2 in 162 out of 191 (84.8%) fresh EOC tissues, which was significantly correlated with International Federation of Gynecology and Obstetrics (FIGO) stage, differentiation, histological type, recurrence, and prognosis of EOC patients. Our results showed that upregulation of KPNA2 expression significantly increased the proliferation and tumorigenicity of EOC cells (EFO-21 and SK-OV3) in vitro and in vivo, by promoting cell growth rate, foci formation, soft agar colony formation, and tumor formation in nude mice. By contrast, knockdown of KPNA2 effectively suppressed the proliferation and tumorigenicity of these EOC cells in vitro and in vivo. Our results also indicated that the molecular mechanisms of the effect of KPNA2 in EOC included promotion of G1/S cell cycle transition through upregulation of c-Myc, enhanced transcriptional activity of c-Myc, activation of Akt activity, suppression of FOXO3a activity, downregulation of cyclin-dependent kinase (CDK) inhibitor p21Cip1 and p27Kip1, and upregulation of CDK regulator cyclin D1. Our results show that KPNA2 has an important role in promoting proliferation and tumorigenicity of EOC, and may represent a novel prognostic biomarker and therapeutic target for this disease.

SUBMITTER: Huang L

PROVIDER: S-EPMC3763430 | biostudies-other | 2013 Aug

REPOSITORIES: biostudies-other

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Project description:BackgroundPeripheral serotonin is involved in tumorigenesis and induces a pro-proliferative effect in hepatocellular carcinoma (HCC) cells; however, the intracellular mechanisms by which serotonin exerts a mitogenic effect remain unclear. In this research, we examined whether FOXO3a, a transcription factor at the interface of crucial cellular processes, plays a role downstream of serotonin in HCC cells.ResultsThe cell viability and expression of FOXO3a was assessed in three HCC cell lines (Huh7, HepG2 and Hep3B) during serum deprivation in the presence or absence of serotonin. Serum free media significantly inhibited HCC proliferation and led to reduced expression and nuclear accumulation of FOXO3a. Knockdown of FOXO3a enhanced the ability of serum deprivation to inhibit HCC cells proliferation. And overexpression of non-phosphorylated FOXO3a in HCC cells reversed serum-deprivation-induced growth inhibition. Serotonin reversed the serum-deprivation-induced inhibition of cell proliferation and upregulated FOXO3a in Huh7 cells; however, serotonin had no effect on the proliferation of serum-deprived HepG2 or Hep3B cells. In addition to proliferation, serotonin also induced phosphorylation of AKT and FOXO3a in serum-deprived Huh7 cells but not in HepG2 and Hep3B cells. However, the phosphorylation of FOXO3a induced by serotonin did not export FOXO3a from nucleus to cytoplasm in serum-deprived Huh7 cells. Consequently, we demonstrated that serotonin promoted the proliferation of Huh7 cells by increasing the expression of FOXO3a. We also provide preliminary evidence that different expression levels of the 5-HT2B receptor (5-HT2BR) may contribute to the distinct effects of serotonin in different serum-deprived HCC cells.ConclusionsThis study demonstrates that FOXO3a functions as a growth factor in serum-deprived HCC cells and serotonin promotes the proliferation of serum-deprived HCC cells via upregulation of FOXO3a, in the presence of sufficient levels of the serotonin receptor 5-HT2BR. Drugs targeting the serotonin-5-HT2BR-FOXO3a pathway may provide a novel target for anticancer therapy.

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KPNA2 promotes cell proliferation and tumorigenicity in epithelial ovarian carcinoma through upregulation of c-Myc and downregulation of FOXO3a.

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