The role of DNA methylation in ovarian cancer chemoresistance: A narrative review

Pralatrexate represses the resistance of HCC cells to molecular targeted agents via the miRNA-34a/Notch pathway

Metabolism-related pathways are important targets for intervention in the treatment of hepatocellular carcinoma (HCC), but few studies have reported on the combination of inhibitors of folate metabolism-related enzymes and molecularly targeted drugs for HCC. The results of the present work are the first to reveal the effects of an inhibitor of dihydrofolate reductase (DHFR), pralatrexate, on the sensitivity of HCC cells to molecularly targeted agents examined using multiple assays. In HCC cells, knockdown of DHFR or treatment with pralatrexate enhanced the sensitivity of HCC cells to molecularly targeted agents, such as sorafenib, regorafenib, lenvatinib, cabozantinib, or anlotinib. Mechanically, pralatrexate decreased the methylation rates of miRNA-34a's promoter region to enhance the expression of miRNA-34a. Treatment with pralatrexate inhibited the expression of Notch and its downstream factors by enhancing the expression of miRNA-34a in HCC cells. In clinical specimens, the expression of miRNA-34a was negatively correlated with DHFR expression, while DHFR expression was positively correlated with the Notch intracellular domain (NICD) and downstream factors of the Notch pathway. The expression of miRNA-34a was negatively correlated with DHFR expression, while the methylation rates of miRNA-34a's promoter were positively related to DHFR. The effect of pralatrexate on the metabolic profile of HCC cells is very different from that of small molecule inhibitors related to glycolipid metabolism. Therefore, pralatrexate upregulates the sensitivity of HCC cells to molecularly targeted drugs. These results expand our understanding of folate metabolism and HCC and can help provide more options for HCC treatment.

Current strategies for early epithelial ovarian cancer detection using miRNA as a potential tool

Ovarian cancer is one of the most aggressive and significant malignant tumor forms in the female reproductive system. It is the leading cause of death among gynecological cancers owing to its metastasis. Since its preliminary disease symptoms are lacking, it is imperative to develop early diagnostic biomarkers to aid in treatment optimization and personalization. In this vein, microRNAs, which are short sequence non-coding molecules, displayed great potential as highly specific and sensitive biomarker. miRNAs have been extensively advocated and proven to serve an instrumental part in the clinical management of cancer, especially ovarian cancer, by promoting the cancer cell progression, invasion, delayed apoptosis, epithelial-mesenchymal transition, metastasis of cancer cells, chemosensitivity and resistance and disease therapy. Here, we cover our present comprehension of the most up-to-date microRNA-based approaches to detect ovarian cancer, as well as current diagnostic and treatment strategies, the role of microRNAs as oncogenes or tumor suppressor genes, and their significance in ovarian cancer progression, prognosis, and therapy.

DNA methylation characteristics associated with chemotherapy resistance in epithelial ovarian cancer

Objective

The high mortality rate of epithelial ovarian cancer (EOC) is often attributed to the frequent development of chemoresistance. DNA methylation is a predictive biomarker for chemoresistance.

Methods

This study utilized DNA methylation profiles and relevant information from GEO and TCGA to identify different methylated CpG sites (DMCs) between chemoresistant and chemosensitive patients. Subsequently, we constructed chemoresistance risk models with DMCs. The genes corresponding to candidate DMCs in chemoresistance risk models were further analyzed to identify different methylated gene symbols (DMGs) associated with chemoresistance. The DMGs that showed a strong correlation with the corresponding DMCs were analyzed through immunohistochemistry.

Results

Compared to chemosensitive EOC patients, chemoresistant patients showed 423 hypermethylated CpGs and 1445 hypomethylated CpGs. The chemoresistance risk models based on DMCs have shown the improved predictive ability for chemoresistance in EOC (AUC = 65.0-76.2%). The methylations of cg25510164, cg13154880, cg15362155 and cg08665359 were strongly associated with decreased risk of chemoresistance. Conversely, the methylation of cg08872590 and cg14739437 significantly increased the risk. We identified 13 DMGs, from 47 DMCs corresponding genes, between chemosensitive and chemoresistant samples. Among the DMGs, the expression levels of DDR2 and OPCML exhibited strong correlations with the corresponding DMCs. DDR2 and OPCML both showed enhanced expression in chemoresistant ovarian microarray tissue.

Conclusions

Hypomethylated CpGs may play a significant role in DNA methylation associated with chemoresistance in EOC. The epigenetic modification of DDR2 could have important implications for the development of chemoresistance. Our study provides valuable insights for future research on DNA methylation in the chemoresistance of EOC.

DNA methylation-mediated repression of microRNA-410 promotes the growth of human glioma cells and triggers cell apoptosis through its interaction with STAT3

This study's purpose was to confirm the observed underexpression of miRNA-410 in glioma tissues and several glioma cells by Quantitative RT-PCR. Our findings suggest that epigenetic alterations occurring at the promoter region of miR-410 may be responsible for the reduced expression of miR-410 in glioma. The occurrence of DNA methylation in the miR-410 promoter was verified to be more prevalent through glioma tissues contrasted to adjacent non-tumor brain tissues through the utilization of methylation-specific PCR and CpG bisulfite sequencing sites in the miR-410 promoter region. Accordantly, miR-410 expression in glioma cell lines was observed to be significantly lesser in comparison to that of the human fetal glial cell line. In addition, it was demonstrated through gain- and loss-of-function investigations that miR-410 exerts significant regulation over cell growth, cell cycle development, and glioma cell apoptosis. The findings of the Luciferase reporter assay and western blot analysis indicate that miR-410 has a direct effect on the 3'-UTR of signal transducer and activator of transcription 3 (STAT3), thereby inhibiting its expression within glioma cells. Besides, our clinical investigation indicates a negative association between miR-410 expression and STAT3 within the glioma tissues of humans. In aggregate, the data provided in this investigation indicates that miR-410 is subjected to underexpression via DNA methylation. Furthermore, it has been observed to perform its function as a tumor suppressor in glioma cells through direct targeting of STAT3. The previously mentioned results could potentially have significant implications for the advancement of a new therapeutic approach for treating glioma.