TUMOUR KINOME RE-WIRING GOVERNS RESISTANCE TO PALBOCICLIB IN OESTROGEN RECEPTOR POSITIVE BREAST CANCERS, HIGHLIGHTING NEW THERAPEUTIC MODALITIES

Estrogen receptor positive (ER+) breast cancers are the most common type of breast cancer. Despite the great efficacy of endocrine therapies, resistance remains a problem. Therefore, there is an immediate need for new, effective therapies in ER+ BC. In this study, we have explored the role of a potent CDK4/6 inhibitor called palbociclib. In order to identify differential phosphoproteomic events that underpin the mode of action and recurrence for this treatment, we generated a panel of palbociclib-sensitive and resistant cell lines and did quantitative, shotgun phosphoproteomics using titanium IMAC. Palbociclib sensitive cell lines (wt-MCF7 or MCF7-LTED) were cultured in phenol red-free RPMI supplemented with 10% FBS and 1nM estradiol or 10% dextran-coated charcoal (DCC) respectively. Thereafter, palbociclib resistant cell lines were generated using 1μΜ palbociclib concentration. Samples were harvested at baseline and at the point of resistance.