1. PI3K/AKT pathway-mediated regulation of p27(Kip1) is associated with cell cycle arrest and apoptosis in cervical cancer
Shyam Babu Prasad, Suresh Singh Yadav, Mitali Das, Arusha Modi, Soni Kumari, Lakshmi Kant Pandey, Sunita Singh, Satyajit Pradhan, Gopeshwar Narayan Cell Oncol (Dordr). 2015 Jun;38(3):215-25. doi: 10.1007/s13402-015-0224-x. Epub 2015 Mar 28.
Background: The cyclin-dependent kinase inhibitor p27(Kip1) is known to act as a putative tumor suppressor in several human cancers, including cervical cancer. Down-regulation of p27(Kip1) may occur either through transcription inhibition or through phosphorylation-dependent proteolytic degradation. As yet, the mechanism underlying p27(Kip1) down-regulation and its putative downstream effects on cervical cancer development are poorly understood. Here we assessed the expression and sub-cellular localization of p27(Kip1) and its effects on proliferation, cell cycle progression and (inhibition of) apoptosis in cervical cancer cells. Methods: Primary cervical cancer samples (n = 70), normal cervical tissue samples (n = 30) and cervical cancer-derived cell lines (n = 8) were used to assess the expression of p27(Kip1) and AKT1 by RT-PCR, Western blotting and immunohistochemistry, respectively. The effects of the PI3K inhibitor LY294004 and the proteasome inhibitor MG132 on cervical cancer cell proliferation were investigated using a MTT assay. Apoptosis and cell cycle analyses were carried out using flow cytometry, and sub-cellular p27(Kip1) localization analyses were carried out using immunofluorescence assays. Results: We observed p27(Kip1) down-regulation (p = 0.045) and AKT1 up-regulation (p = 0.046) in both the primary cervical cancer samples and the cervical cancer-derived cell lines, compared to the normal cervical tissue samples tested. Treatment of cervical cancer-derived cell lines with the PI3K inhibitor LY294002 resulted in a reduced AKT1 activity. We also observed a dose-dependent inhibition of cell viability after treatment of these cell lines with the proteasome inhibitor MG132. Treatment of the cells with LY294002 resulted in a G1 cell cycle arrest, a nuclear expression of p27(Kip1), and a cytoplasmic p27(Kip1) accumulation after subsequent treatment with MG132. Additionally, we found that the synergistic effect of MG132 and LY294002 resulted in a sub-G1 cell cycle arrest and apoptosis induction through poly (ADP-ribose) polymerase (PARP) cleavage. Conclusion: Our data suggest that p27(Kip1) down-regulation in cervical cancer cells is primarily regulated through PI3K/AKT-mediated proteasomal degradation. The observed synergistic effect of the MG132 and LY294002 inhibitors may form a basis for the design of novel cervical cancer therapies.
2. Inhibition of microRNA-181a may suppress proliferation and invasion and promote apoptosis of cervical cancer cells through the PTEN/Akt/FOXO1 pathway
Hongmei Xu, Jihong Zhu, Cong Hu, Hua Song, Yiyang Li J Physiol Biochem. 2016 Dec;72(4):721-732. doi: 10.1007/s13105-016-0511-7. Epub 2016 Aug 18.
MicroRNAs (miRNAs) are endogenous, non-coding, small RNAs, which play a critical role in regulating varieties of the biological and pathologic processes. miR-181a has been reported to participate in tumorigenic progression. However, the roles of miR-181a in cervical cancer (CC) are still unknown. The aim of this research was to explore the effects and molecular mechanism of miR-181a in CC cells. In this paper, the levels of miR-181a in CC cell lines were determined by real-time PCR. We found that the levels of miR-181a were evidently enhanced in CC cell lines compared with normal cervical epithelium cells. Then, the miR-181a inhibitor was transiently transfected into HeLa and CaSKi cells using Lipofectamine 2000 reagent. Subsequently, the Cell Counting Kit-8 (CCK-8) and BrdU-ELISA results showed that down-regulation of miR-181a inhibited the cell viability and proliferation. Our data also demonstrated that miR-181a inhibitor arrested cell cycle progression of HeLa and CaSKi cells by up-regulation of p21 and p27 expressions. In addition, inhibition of miR-181a promoted apoptosis of HeLa and CaSKi cells due to increasing Bax expression and decreasing Bcl-2 expression. Ultimately, the effect of miR-181a inhibitor on the PTEN/Akt/FOXO1 signaling pathway was investigated by Western blot. From our results, down-regulation of miR-181a increased the expression of PTEN and decreased phosphorylation of Akt and FOXO1. Altogether, miR-181a might be an oncogene in CC cells. The potential mechanism was that inhibition of miR-181a might suppress proliferation and invasion and promote apoptosis of HeLa and CaSKi cells by modulating the PTEN/Akt/FOXO1 signaling pathway.
3. Knockdown of hnRNP A2/B1 inhibits cell proliferation, invasion and cell cycle triggering apoptosis in cervical cancer via PI3K/AKT signaling pathway
Xiang Shi, Li Ran, Yao Liu, Shu-Huai Zhong, Ping-Ping Zhou, Ming-Xin Liao, Wen Fang Oncol Rep. 2018 Mar;39(3):939-950. doi: 10.3892/or.2018.6195. Epub 2018 Jan 5.
Cervical cancer is currently one of the major threats to women's health. The overexpression of heterogeneous nuclear ribonucleoprotein A2/B1 (hnRNP A2/B1) as the biomarker has been investigated in various cancers. In our previous study, we found that lobaplatin induced apoptosis and cell cycle arrest via downregulation of proteins including hnRNP A2/B1 in cervical cancer cells. However, the underlying relationship between hnRNP A2/B1 and cervical cancer remained largely unknown. hnRNP A2/B1 knock‑down in HeLa and CaSki cells was performed by shRNA transfection. The expression of hnRNP A2/B1 was detected by western blot and Quantitative Real‑time PCR. Cell proliferation, migration, invasion and the IC50 of lobaplatin and irinotecan were determined by MTT assay, Transwell assay, Plate colony formation assay and wound healing assay. Flow cytometry was perfomed to investigate cell apoptosis and the cell cycle. The expression of PI3K, AKT, p‑AKT, p21, p27, caspase‑3, cleaved caspase‑3 were revealed by western blot. Nude mouse xenograft model was undertaken with HeLa cells and the xenograft tumor tissue samples were analyzed for the expression of PCNA and Ki‑67 by immunohistochemistry and the cell morphology was evaluated by hematoxylin and eosin (H&E). Results revealed that hnRNP A2/B1 was successfully silenced in HeLa and CaSki cells. hnRNP A2/B1 knock‑down significantly induced the suppression of proliferation, migration, invasion and also enhancement of apoptosis and reduced the IC50 of lobaplatin and irinotecan. The expression of p21, p27 and cleaved caspase‑3 in shRNA group were significantly upregulated and the expression of p‑AKT was reduced both in vitro and in vivo. The results of immunohistochemistry showed that PCNA and Ki‑67 were significantly downregulated in vivo. The growth of nude mouse xenograft tumor was significantly reduced by hnRNP A2/B1 knock‑down. Taken together, these data indicate that inhibition of hnRNP A2/B1 in cervical cancer cells can inhibit cell proliferation and invasion, induce cell‑cycle arrestment and trigger apoptosis via PI3K/AKT signaling pathway. In addition, after silencing hnRNP A2/B1 can increase the sensitivity of cervical cancer cells to lobaplatin and irinotecan.
