Intratumoural inflammation and endocrine resistance in breast cancer

It is becoming clear that inflammation-associated mechanisms can affect progression of breast cancer and modulate responses to treatment. Estrogen receptor alpha (ERα (ESR1)) is the principal biomarker and therapeutic target for endocrine therapies in breast cancer. Over 70% of patients are ESR1-positive at diagnosis and are candidates for endocrine therapy. However, ESR1-positive tumours can become resistant to endocrine therapy. Multiple mechanisms of endocrine resistance have been proposed, including suppression of ESR1. This review discusses the relationship between intratumoural inflammation and endocrine resistance with a particular focus on inflammation-mediated suppression of ESR1.