MAPRE3 as an epigenetic target of EZH2 restricts ovarian cancer proliferation in vitro and in vivo.

Ovarian cancer (OC) is a lethal gynecologic cancer and the common cause of death within women worldwide. The polycomb group protein enhancer of zeste homolog 2 (EZH2) is a histone methyltransferase highly expressed in various tumors, including OC. However, the mechanistic basis of EZH2 oncogenic activity in OC remain incompletely understood. Bioinformatics analysis showed that the expression of MAPRE3 was lower in OC tissues than in normal tissues, and was positively correlated with the overall survival. MAPRE3 overexpression decreased cell growth, inducing cell cycle arrest and apoptosis in OC cells, whereas MAPRE3 silencing promoted proliferation and accelerated cell cycle progression of OC cells. The in vivo study validated that overexpression of MAPRE3 impeded tumor formation and growth of OC xenografts in nude mice. In addition, knockdown of EZH2 in OC cells downregulated H3K27me3 expression and increased MAPRE3 expression. Inhibiting EZH2 in OC cells reduced the enrichment of H3K27me3 on the promoter of MAPRE3. Furthermore, MAPRE3 silencing significantly reversed changes in the expression of cell cycle and apoptosis-related markers and cell growth mediated by EZH2 knockdown in OC cells. MAPRE3 functions as a suppressor of OC and is epigenetic repressed by EZH2, suggesting a potential therapeutic strategy for OC by targeting EZH2/MAPRE3 axis.

Bioinformatic mining of kinase inhibitors that regulate autophagy through kinase signaling pathways.

The aim of this study was to predict the kinase inhibitors that may regulate autophagy. A total of 62 kinases were obtained through text mining by importing the keyword 'autophagy' and a 'protein kinase' Excel file to PubMed. Subsequently, 146 kinases were derivated through screening in the PubMed database by importing the 'autophagy­associated gene' and 'protein kinase' files. Following intersection of the above two methods, 54 candidate autophagy­associated kinases were obtained. Enrichment analysis indicated that these candidate autophagy­associated kinases were mainly enriched in pathways such as the calcium, Wnt, HIF­1 and mTOR signaling pathways. Among the 54 kinases, 24 were identified through text mining to have specific kinase inhibitors that regulate the corresponding functions; a total of 56 kinase inhibitors were found to be involved in the regulation of these 24 kinases. In total, nine of these 56 kinase inhibitors identified had been widely reported in autophagy regulation studies, 23 kinase inhibitors had been seldom reported and 24 had never been reported. Therefore, introducing these kinases into autophagy regulation analysis in subsequent studies may produce important results.

CDK2 and CDK4 play important roles in promoting the proliferation of SKOV3 ovarian carcinoma cells induced by tumor-associated macrophages.

A large quantity of M2-polarized tumor-associated macrophages (TAMs) is present in the tissue, ascitic fluid and peritoneum of ovarian cancer patients. A thorough understanding of the roles of M2-TAM in the development of ovarian cancer may provide new insight into the treatment of this disease. The rapid advancement of omics techniques presents a great challenge to biologists to extract meaningful biological information from vast pools of data. In the present study, using microarray method, we identified 996 genes in SKOV3 ovarian carcinoma cells that underwent expression level changes under the influence of TAMs. Subsequently, based on the protein-protein interactions network and the differentially expressed genes, a network showing the influence of TAMs on SKOV3 cells was constructed. The resulting network was analyzed with CFinder software and four modules were found; these modules were further analyzed using David software to perform functional annotations. It was found that module I was mainly related to tumorigenesis and cell cycle. Hence, 31 genes in module I were analyzed with Cytoscape software to generate a gene-function network, which revealed that four gene proteins (E2F1, RB1, CDK2 and CDK4) were functional. Based on literature review, we postulated that CDK2 and CDK4 were key players in the network. In the subsequent molecular experiments, western blot analysis and kinase activity detection demonstrated that TAMs can significantly boost the expression levels and activities of CDK2 and CDK4 in SKOV3 cells. With 3H-TdR incorporation and flow cytometry assay, the proliferation and cell cycle distribution of SKOV3 cells were detected in the absence or presence of CDK2 and CDK4 inhibitors and the results confirmed that the two kinases played a key role in TAM cells enhancing SKOV3 cell proliferation by promoting G0/G1 to S transition. In the present study, we identified the specific changes in the gene expression profile of SKOV3 cells under the influence of TAMs and explored a method for analyzing the gene expression profile data. The results may aid in the design of subsequent molecular experiments.

Dihydroartemisinin potentiates the anticancer effect of cisplatin via mTOR inhibition in cisplatin-resistant ovarian cancer cells: involvement of apoptosis and autophagy.

Dihydroartemisinin (DHA) exhibits anticancer activity in tumor cells but its mechanism of action is unclear. Cisplatin (DDP) is currently the best known chemotherapeutic available for ovarian cancer. However, tumors return de novo with acquired resistance over time. Mammalian target of rapamycin (mTOR) is an important kinase that regulates cell apoptosis and autophagy, and its dysregulation has been observed in chemoresistant human cancers. Here, we show that compared with control ovarian cancer cells (SKOV3), mTOR phosphorylation was abnormally activated in cisplatin-resistant ovarian cancer cells (SKOV3/DDP) following cisplatin monotherapy. Treatment with cisplatin combined with DHA could enhance cisplatin-induced proliferation inhibition in SKOV3/DDP cells. This mechanism is at least partially due to DHA deactivation of mTOR kinase and promotion of apoptosis. Although autophagy was also induced by DHA, the reduced cell death was not found by suppressing autophagic flux by Bafilomycin A1 (BAF). Taken together, we conclude that inhibition of cisplatin-induced mTOR activation is one of the main mechanisms by which DHA dramatically promotes its anticancer effect in cisplatin-resistant ovarian cancer cells.