Palbociclib (PD-0332991) is an inhibitor for cyclin-dependent kinase 4/6 complex and exhibits more activity in luminal ER+ breast cancer. However, sensitivity of breast cancer stem cells (BCSCs) to PD-0332991 treatment and expression patterns of cell cycle regulatory genes after PD-0332991 treatment in BCSCs are still unclear. This study aims to determine response of BCSCs to PD-0332991 treatment.
Materials and Methods: An experimental in vitro study was designed on breast cancer cell lines. MCF-7 and BCSCs cell lines were used in this study. Water soluble tetrazolium salt-1 (WST-1) test was used for the cytotoxicity assay. Cell cycle distribution pattern and apoptosis were examined with flow cytometry according to IC50 values at 48th h. Real-Time PCR was used to detect expression profiles of CDKN1A, CHEK1, CDKN2A, CDC25A, and CCND1 genes.
Results: PD-0332991 decreased cell proliferation in both cell lines. G0/G1 arrest was detected for both cell lines. There was no apoptotic effect of PD-0332991 on MCF-7 cells and BCSCs. In MCF-7 cells, expression levels of CDKN1A, CDKN2A, and CCND1 genes were increased as 3.11, 3.21, and 1.05 folds, respectively. Expression levels of CHEK1 and CDC25A genes were decreased as 4.75 and 3.73 folds, respectively. In BCSCs, expression levels of CDKN1A, CHEK1, CDKN2A, and CCND1 were decreased as 1.15, 2.01, 1.32, and 1.68 folds, respectively. No expression of CDC25A gene was found in BCSCs group.
Conclusion: In this study, it was observed that PD-0332991 leads to different expression profiles for cell cycle regulatory genes between BCSCs and breast cancer cells.