Interferon response gene signature linked to CDK4/6 inhibition resistance

Aberrant interferon signaling is associated with intrinsic resistance to CDK4/6 inhibition in patients with estrogen receptor (ER)-positive breast cancer.

Molecular profiling of ER-positive breast cancer cell lines and breast cancer patients demonstrates that interferon signaling is associated with reduced sensitivity to CDK4/6 inhibition, and that an interferon-related palbociclib resistance signature (IRPS) predicts poor prognosis in luminal breast cancer patients, said Carmine De Angelis, MD, PhD, at the 2019 San Antonio Breast Cancer Symposium.

Despite the improvement in outcomes with CDK4/6 inhibition in combination with endocrine therapy in patients with metastatic ER-positive/HER2-negative breast cancer, intrinsic and acquired resistance to CDK4/6 inhibitors is common. “Deciphering the molecular basis for sensitivity and resistance to CDK4/6 inhibitors is crucial to identify predictive biomarkers as well as potential novel therapeutic targets to improve patient outcome,” said Dr. De Angelis, from Baylor College of Medicine, Houston.

Multiple breast cancer ER-sensitive and ER-resistant cell lines and tumor samples from two clinical trials of CDK4/6 inhibition in the neoadjuvant setting—NeoPalANA (palbociclib) and neoMONARCH (abemaciclib)—were analyzed.

Gene cell enrichment analysis identified the interferon-alpha response and interferon-gamma response among the top ranked gene signatures enriched in cell lines resistant to palbociclib compared with those sensitive to palbociclib. Using gene expression data from the Cancer Dependency Map (DepMap), increased resistance to CDK4/6 knockdown by messenger RNA was associated with higher interferon signaling in ER-positive, HER2-negative cell lines.

To determine if the interferon signaling was associated with intrinsic resistance to CDK4/6 inhibitors in ER-positive/HER2-negative breast cancer patients, the researchers interrogated the baseline gene expression profile of CDK4/6 inhibitor-resistant tumor vs. sensitive tumor from the NeoPalANA and neoMONARCH trials. “This analysis revealed that the interferon gamma and the interferon alpha response as well as the IRPS were among the top enriched signatures in the CDK4/6-resistant tumors,” said Dr. De Angelis.

The behavior and prognostic value of the signature within primary breast cancer tumors was assessed in patients with ER-positive/HER2-negative breast cancer using the TCGA, METABRIC, and KMplot datasets. In this analysis, the IRPS score was found to be significantly higher in luminal B compared with luminal A subtypes in both the TCGA and METABRIC datasets. “We also found that patients with high IRPS breast cancer had a significantly lower breast cancer-specific survival compared with patients with low IRPS scores,” said Dr. De Angelis. “This result was independent of the luminal subtype.”

In estimating the infiltration of immune and stromal cells within each tumor in the TCGA dataset, it was found that high IRPS tumors did not present with high infiltration of interferon-producing cells, suggesting that interferon signaling is tumor epithelial-derived in a substantial number of primary ER-positive, HER2-negative breast cancers. In addition, in ER-positive, HER-2 negative tumors, immune checkpoint expression was found to be significantly correlated with IRPS score. “Also, we found that the top two immune subsets that correlate with high IRPS score were the M1 macrophages and the immunosuppressive T regulatory cells,” said Dr. De Angelis.

Future studies are warranted to provide mechanistic insights into the association between interferon signaling and response to CDK4/6 inhibition, said De Angelis, as well to investigate the therapeutic potential of combinations with immune checkpoint inhibitors.