Epigenetic changes in tumor suppressor genes, P15, P16, APC-3 and E-cadherin in body fluid

Application of the CRISPR/Cas9-based gene editing technique in basic research, diagnosis, and therapy of cancer

The 2020 Nobel Prize in Chemistry was awarded to Emmanuelle Charpentier and Jennifer Doudna for the development of the Clustered regularly interspaced short palindromic repeats/CRISPR-associated nuclease9 (CRISPR/Cas9) gene editing technology that provided new tools for precise gene editing. It is possible to target any genomic locus virtually using only a complex nuclease protein with short RNA as a site-specific endonuclease. Since cancer is caused by genomic changes in tumor cells, CRISPR/Cas9 can be used in the field of cancer research to edit genomes for exploration of the mechanisms of tumorigenesis and development. In recent years, the CRISPR/Cas9 system has been increasingly used in cancer research and treatment and remarkable results have been achieved. In this review, we introduced the mechanism and development of the CRISPR/Cas9-based gene editing system. Furthermore, we summarized current applications of this technique for basic research, diagnosis and therapy of cancer. Moreover, the potential applications of CRISPR/Cas9 in new emerging hotspots of oncology research were discussed, and the challenges and future directions were highlighted.

Modified CDKN2B (p15) and CDKN2A (p16) DNA methylation profiles in urban pesticide applicators

Gene-specific changes in DNA methylation by pesticides in occupationally exposed populations have not been studied extensively. Of particular concern are changes in the methylation profile of tumor-suppressor, such as CDKN2B and CDKN2A, genes involved in oncogenesis. The aim of this study was to evaluate the methylation profiles of CDKN2B and CDKN2A genes in urban pesticide applicators and their relationship with occupational exposure to pesticides. A cross-sectional study was conducted in 186 urban pesticide applicators (categorized as high or moderate exposures) and 102 participants without documented occupational exposures to pesticides. Acute and chronic pesticide exposures were evaluated by direct measurement of urinary dialkylphosphates, organophosphate metabolites, and a structured questionnaire, respectively. Anthropometric characteristics, diet, clinical histories, and other variables were estimated through a validated self-reported survey. DNA methylation was determined by pyrosequencing of bisulfite-treated DNA. Decreased DNA methylation of the CDKN2B gene was observed in pesticide-exposed groups compared to the non-exposed group. In addition, increased methylation of the CDKN2A promoter was observed in the moderate-exposure group compared to the non-exposed group. Bivariate analysis showed an association between CDKN2B methylation and pesticide exposure, general characteristics, smoking status, and micronutrients, while changes in CDKN2A methylation were associated with pesticide exposure, sex, educational level, body mass index, smoking status, supplement intake, clinical parameters, and caffeine consumption. These data suggest that pesticide exposure modifies the methylation pattern of CDKN2B and CDKN2A genes and raise important questions about the role that these changes may play in the regulation of cell cycle activities, senescence, and aging.

Prognostic value of aberrant hypermethylation in pleural effusion of lung adenocarcinoma

Lung adenocarcinoma is one of the most frequent causes of malignant pleural effusions (MPE). The presence of MPE bears a poor prognosis. Although epigenetic changes are commonly related to human neoplasia, scarce date is available on patients with MPE. We aimed to estimate the prognostic value of DNA methylation of tumor suppressor genes from pleural fluid. Thirty patients with MPE due to lung adenocarcinoma were prospectively included. Methylation-specific (MS) PCR was used to study the methylation status of the promoter region of tumor suppressor genes p16/INK4a, MGMT, BRCA1 and RARβ in pleural fluid. Clinical data and survival were collected. Survival analysis was performed using Kaplan-Meier plots and Cox regression. Hypermethylation in at least one gene was detected in 25 patients (83.3%). On multivariate analysis factors significantly associated with shorter survival were the lack of hypermethylation in any of the studied genes (hazard ratio = 9.3; p = 0.001), Charlson index ≥ 3 (hazard ratio = 9.6, p = 0.002) and no oncological treatment (hazard ratio = 11.1; p < 0.001). Analysis of aberrant promoter hypermethylation of tumor suppressor genes may be useful in predicting prognosis, but further studies are needed to validate our findings.