Activation of the interferon signaling pathway is associated with resistance to CDK4/6 inhibitors and immune checkpoint activation in ER-positive breast cancer [RNA-seq]
CDK4/6 inhibitors are highly effective against ER+/HER2- breast cancer (BC); however, intrinsic and acquired resistance is common. Elucidating the molecular features of sensitivity and resistance to CDK4/6 inhibitors may lead to the identification of predictive biomarkers and novel therapeutic targets, paving the way toward improving patient outcomes. Parental BC cells and their endocrine-resistant derivatives (EndoR) were used in this study. Derivatives with acquired resistance to palbociclib (PalboR) were generated from parental and estrogen deprivation-resistant MCF7 and T47D cells. Transcriptomic and proteomic analyses were performed in palbociclib-sensitive and PalboR lines. We found that parental and EndoR BC lines showed varying degrees of sensitivity to palbociclib. Transcriptomic analysis of these cell lines identified an association between high Interferon (IFN) signaling and reduced sensitivity to CDK4/6 inhibitors, thus an 'IFN-Related Palbociclib-Resistance Signature' (IRPS) was derived. In two neoadjuvant trials of a CDK4/6 inhibitor plus endocrine therapy, IRPS and other IFN-related signatures were highly enriched in patients with tumors exhibiting intrinsic resistance to CDK4/6 inhibition. PalboR derivatives displayed a dramatic activation of IFN/STAT1-signaling compared to their short-term treated or untreated counterparts. In primary ER+/HER2- tumors, the IRPS score was significantly higher in lumB than lumA subtype and correlated with increased gene expression of immune checkpoints, endocrine resistance, and poor prognosis. Our study demonstrates that aberrant IFN-signaling is associated with intrinsic resistance to CDK4/6 inhibitors. Experimentally, acquired resistance to palbociclib is associated with activation of the IFN-pathway, which warrants additional studies to clarify its involvement in resistance to CDK4/6 inhibitors. Overall design: RNA-seq of ER+ breast cancer cell models and derivatives with resistance to endocrine therapy or dual resistance to estrogen deprivation and palbociclib, in duplicates, using Illumina NextSeq500.