RNA sequencing of luminal breast cancer patient-derived xenografts (PDX) library to capture tumor heterogeneity and explore the mechanisms of resistance to CDK4/6 inhibitors

Combining CDK4/6 inhibitors (CDK4/6i) with endocrine therapy has proven clinically effective and represents now the first-line treatment for advanced Luminal Breast Cancer (LBC) patients. However, resistance to CDK4/6i almost invariably arises in these patients, emphasising the critical need to comprehend these mechanisms and develop new strategies to overcome resistance. We report on the generation and characterisation of a LBC PDX displaying acquired resistance to CDK4/6i palbociclib. Treating a sensitive luminal BC PDX with the CDK4/6i palbociclib revealed that, despite initial tumour shrinkage, some tumours might eventually regrow under drug treatment. RNA sequencing, followed by gene set enrichment analyses, unveiled that this PDX have become refractory to CDK4/6i, both at biological and molecular level.