Multi-omics Characterization of Acquired Olaparib Resistance in BRCA1 and BRCA2 Mutant Breast Cancer Cell Lines.

Poly (ADP-ribose) polymerase inhibitors (PARPi) are widely used as targeted therapies against breast cancers with BRCA mutations. However, the development of resistance to PARPi poses a significant challenge for long-term efficacy of these therapies, warranting further understanding of mechanisms of PARPi resistance. Here, we generated and characterized Olaparib resistance in BRCA1/2 mutant breast cancer cell lines MDAMB436 and HCC1428 using a systems-level multi-omics approach, including transcriptome, proteome, phosphoproteome, and ADP-ribosylation analysis. Our analyses revealed that resistance development strongly correlated with protein expression changes, while modest effects on phosphorylation- and ADP-ribosylation-dependent signaling pathways were observed. We found that BRCA1 expression was reestablished in OR MDAMB436 cell lines, while PARP1 expression was decreased. In OR HCC1428 cell lines, the BRCA2 mutation was not reverted. However, we observed increased expression of Fanconi anemia group D2 (FANCD2), histone parylation factor 1 (HPF1), and Nicotinamide phosphoribosyltransferase (NAMPT) in various cell lines, suggesting increased replication fork protection, and changes in the ADPr pathway and adaptation of metabolic pathways as resistance mechanisms. Our findings provide valuable insights into the complex landscape of PARPi resistance, offering potential targets for further investigation and therapeutic intervention.