Identification of Epigenetic Regulatory Networks of Gene Methylation-miRNA-Transcription Factor Feed-Forward Loops in Basal-like Breast Cancer.

Basal-like breast cancer (BLBC) is associated with poor prognosis, high recurrence rates, and limited therapeutic options, largely due to its molecular heterogeneity and complexity, which include epigenetic alterations. This study investigated epigenetic regulatory networks in BLBC by analyzing DNA methylation in distal cis-regulatory regions and its impact on genes, transcription factors (TFs), and microRNAs (miRNAs) expression. Data from TCGA were processed using the ELMER and DESeq2 tools to identify differentially methylated regions and differentially expressed genes, TFs, and miRNAs. The FANMOD algorithm was used to identify the regulatory interactions uncovering the feed-forward loops (FFLs). The analysis identified 110 TF-mediated FFLs, 43 miRNA-mediated FFLs, and five composite FFLs, involving 18 hypermethylated and 32 hypomethylated genes, eight upregulated and nine downregulated TFs, and 21 upregulated and seven downregulated miRNAs. The TF-mediated FFLs major regulators involved the AR, EBF1, FOS, FOXM1, and TEAD4 TFs, while key miRNAs were miR-3662, miR-429, and miR-4434. Enriched pathways involved cAMP, ErbB, FoxO, p53, TGF-beta, Rap1, and Ras signaling. Differences in hallmark gene set categories reflected distinct methylation and miRNA expression profiles. Overall, this integrative analysis mapped the intricate epigenetic landscape of BLBC, emphasizing the role of FFLs as regulatory motifs that integrate DNA methylation, TFs, and miRNAs in orchestrating disease's development and progression and offering potential targets for future diagnostic and therapeutic strategies.