<p>Transcriptomics Analysis of the Tumor-Inhibitory Pathways of 6-Thioguanine in MCF-7 Cells via Silencing DNMT1 Activity</p>

Abstract

Background: 6-thioguanine (6-TG), as a conventional "ancient" drug for the treatment of acute leukemia, has been proved to have extensive anti-tumor roles. This study was created to investigate the hidden function of 6-TG on the MCF-7 breast cancer cell line (ER+, PR+) and its mechanisms. Methods: MCF-7 cells were treated with 6-TG, and the IC50 value was measured by a cell counting kit-8 assay. Differentially expressed genes (DEGs) were confirmed by RNA-seq analysis. Apoptosis and cell cycle consequences were determined by flow cytometry and Western blot analyses. Results: The results showed that colony formation decreased markedly and the percentage of cell apoptosis increased after 6-TG treatment. DNMT1 mRNA and protein expression decreased, and FAS expression increased. Moreover, 6-TG also induced MCF-7 cells to undergo G2/M phase cell cycle arrest and upregulated CDKN1A (p21). Conclusion: Overall, our results suggest that 6-TG may induce FAS-mediated exogenous apoptosis and p21-dependent G2/M arrest by inhibiting the activity of DNMT1 in MCF-7 breast cancer cells.

Construction and analysis of competing endogenous RNA network of MCF‑7 breast cancer cells based on the inhibitory effect of 6‑thioguanine on cell proliferation

“…Based on the online database of StarBase V2.0, the lncRNA-miRNA pairs were predicted and seven candidate lncRNAs and 125 miRNAs were compared. Both pathway enrichment and the results of a previous study (12) demonstrated that apoptosis and the p53 signaling pathway were the two main pathways induced by 6-TG in MCF-7 cells, and the aberrant expression of mRNAs from these two pathways is depicted in Table II. Next, the target miRNAs of these differentially expressed mRNAs were predicted using TargetScan, miRDB and miRTarBas online software.…”

“…Data processing and differential expression analysis. The sequencing data of samples from the MCF-7 control and 6-TG groups were obtained from a previous study (12). The raw data were available from the NCBI GEO database (https://www.…”

“…The raw data were available from the NCBI GEO database (https://www. ncbi.nlm.nih.gov/geo/) (GSE130161) (12). The differential expression of lncRNAs were confirmed by performing normalization and log 2 conversion.…”

“…The cells were cultured in high-glucose DMEM (Gibco; Thermo Fisher Scientific, Inc.) supplemented with 10% FBS (Biological Industries), 1% MEM nonessential amino acids (Gibco; Thermo Fisher Scientific, Inc.), 1% GluMAX and 1% penicillin-streptomycin solution (Gibco; Thermo Fisher Scientific, Inc.). The effects of 6-TG on cell viability were determined through the Cell Counting Kit-8 assay, and MCF-7 cells were treated with a half-maximal inhibitory concentration of 6-TG ( 12 ).…”

“…Following further research, 6-TG has proven to have therapeutic effects on inflammatory bowel disease, children's gliomas and pancreatic cancer (9)(10)(11). In a previous study, 6-TG was shown to inhibit MCF-7 breast cancer cell proliferation by increasing FAS expression, thereby activating the apoptosis pathway (12). Therefore, regarding the treatment of breast cancer with 6-TG, the mechanism underlying the effects of this drug warrant further exploration.…”