Immunomodulation of FOXP3 regulatory T cells by the aromatase inhibitor letrozole in breast cancer patients

Abstract

Purpose: We have shown previously that tumor infiltration by FOXP3 + regulatory T cells (Treg) is associated with increased relapse and shorter survival of patients with both in situ and invasive breast cancer. Because estrogen regulatesTreg numbers in mice and promotes the proliferation of human Tregs, we hypothesized that blocking estrogen receptor-α signaling would abrogate Tregs and be associated with response to hormonal therapy and increased survival. Experimental Design: FOXP3+ Tregs were quantified in tumor samples collected at baseline by incisional biopsy and after 6 months at definitive surgery in 83elderly breast cancer patients (T2-4 N0-1) enrolled in a randomized phase II trial..