Abstract

Background: Triple-negative breast cancer (TNBC) remains a clinical challenge due to its aggressive nature and the frequent emergence of therapeutic resistance. While the role of protein-coding genes in DNA repair is well-documented, the regulatory contributions of the non-coding genome, specifically long intergenic non-coding RNAs (lincRNAs), remain largely undefined. Objectives: In this study, we characterize the biological significance of LincRNA-BC7, a novel transcript identified within the breast cancer field effect. Methods: Through a combined in silico and in vitro approach, we investigated the transcriptional dynamics of the LincRNA-BC7/miR-663a/BRCA1 axis in response to the PARP inhibitor, Olaparib. Results: Our results demonstrate that Olaparib induces selective cytotoxicity in BRCA1-deficient MDA-MB-231 cells while sparing non-cancerous HEK293 cells, a response accompanied by a significant downregulation of LincRNA-BC7 and a reciprocal upregulation of BRCA1. Bioinformatics analysis through BLASTN, miRBase, and KEGG revealed that LincRNA-BC7 contains highly complementary binding sites for miR-663a, suggesting it functions as a competing endogenous RNA (ceRNA) or “molecular sponge.” Conclusions: By sequestering miR-663a, LincRNA-BC7 appears to modulate the expression of critical signaling nodes within the PI3K-AKT and TP53 pathways, thereby influencing cellular sensitivity to DNA-damaging agents. These findings suggest that LincRNA-BC7 is a key determinant of the aggressive TNBC phenotype and the response to PARP inhibition. Our study establishes the LincRNA-BC7/miR-663a axis as a novel biomarker for precision risk stratification and a promising therapeutic target to enhance treatment outcomes in BRCA1-associated breast cancers.

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