Role of Differentially Expressed Proteins in Acquired Resistance to Cdk4/6 Inhibitor in Breast Cancer

Abstract CDK4/6 inhibitors (Abemaciclib, Ab and Palbociclib, Pb) stop the G1-phase in cell-cycle being used to cure advanced stage of breast cancer (BC). Acquired resistance is a major challenge in BC therapy. The molecular signature of the therapy resistance for Ab and Pb drugs in BC should be explored. Here, we developed Ab/Pb-resistant cell-models and explored the molecular changes. Drug’s resistance cells were developed in MCF-7 cells by continuous drug treatment and it was confirmed by MTT-assay, PI-staining-microscopy, and real-time-qPCR. Global proteome profiling done by Labelled-free-Proteome-Orbitrap-Fusion-MS-MS technique. Bioinformatics tools used to analyse the proteome data. Ab-resistant and Pb-resistant MCF-7 cells showed increased tolerance for the respective drug. The BCL-2 and MCL-1 survival genes were up-regulated, while the apoptosis genes BAD, BAX, CASP-3 and PARP-1were down-regulated in the resistant cells. Expression of the MDR-1, ABCG2, ESR-1, CDK4, CDK6, and Cyclin-D1 genes were increased in both resistance cells. For proteomics, 237 and 239 proteins were expressed differently in the resistant Ab and Pb cells, respectively. The NUDT5, PEPD, ABAT, ATP1B1, GGCT, and SELENBP1 proteins were down-regulated and the SBSN, HSD17B10, CD9, PDIA3, PSMB4, SLC2A1, and VTN proteins were up-regulated in Ab-resistant cells. The NUDT5, PEPD, and GGCT proteins were down-regulated, while CD47, HIST1H2BN, LMNA, VTN, PSMB5, HBB, PSMA7, FLNB, PRDX4, VDAC1, GOT2, HSPA5, SERPINH1, EIF4A2, FTH, and VIM proteins were up-regulated in Pb-resistant cells. These proteins are a new set of prognostic markers and drug targets for overcoming the respective drug resistance. However, it is necessary to perform an in vivo or clinical assessment.