Genetic and Methylation-Induced Loss of miR-181a2/181b2 within chr9q33.3 Facilitates Tumor Growth of Cervical Cancer through the PIK3R3/Akt/FoxO Signaling Pathway

Purpose: Loss of Chr9q31-33 is one of the most common chromosome imbalances of cervical cancer, but the underlying mechanism has not been well documented. Experimental Design: The loss ofheterozygosity (LOH) status of Chr9q31-33 was investigated utilizing 26 microsatellite markers. We detected the expression of miR-181a2/181b2 by qRT-PCR analysis of cervical cancer cell lines and 100 paired tumor samples and corresponding adjacent non-tumor tissues. Kaplan-Meier and Cox proportional hazard regression analyses were performed to identify the prognostic value of miR-181a2/181b2. Regulation of expression was analyzed by methylation-specific PCR. The tumorsuppressing effects of miR-181a2/181b2 were determined in vitro and in vivo. The target gene and signaling pathway thatmediated the function of miR-181a2/181b2 were also identified. Results: Chr9q33.3 was identified as one of the most deleted regions in cervical cancer. Underexpression of miR-181a2/181b2 was detected in 46% of cervical cancer and was induced by the LOH of chr9q33.3 and promoter hypermethylation. Attenuated miR-181a2/181b2 expression predicted a poor prognostic phenotype and advanced clinical stage of cervical cancer. miR-181a2/181b2 prominently dampened cell-cycle progression, suppressed cell growth, and promoted apoptosis of tumor cells in vitro. They also effectively impeded tumor formation and growth in vivo. miR-181a2/181b2 exert the tumor suppressor ability by depressing the direct target PIK3R3 (p55 gamma) and consequently modulating the PIK3R3/Akt/FoxO signaling pathway. Conclusions: We demonstrated a cause-and-effect event beginning from loss of chr9q33.3, a frequent event in cervical cancer, to the underexpression of miR-181a2/181b2, leading to the elevated activation of the PI3K pathway. Clin Cancer Res; 23(2); 575-86. (C) 2016 AACR.