Relationship of tumor and stromal autophagy and endocrine responsiveness in breast cancer tissues.

Abstract

571 Background: Neoadjuvant endocrine therapy has been employed to improve surgical outcomes for endocrine responsive breast cancers in post-menopausal women. Endocrine responsiveness is estimated by the expression levels of hormone receptors although heterogeneity in the response is well recognized. To improve the clinical outcome, it is critical to understand how cancer tissues react to the endocrine treatment. Methods: Pre-treatment biopsy samples and post-treatment surgical samples were obtained from 116 patients enrolled onto the multicenter prospective study of neoadjuvant exemestane therapy, JFMC34-0601. Fifty-four paired samples were available for the study. Estrogen receptor, progesterone receptor, HER2, Ki-67 by immunohistochemistry and pathological response were centrally evaluated. Apoptosis was assessed by TUNEL (Roche Diagnostics, Mannheim) and M30 (Roche Diagnostics, Mannheim). Autophagy was assessed by anti-beclin 1 (Novus Biologicals, CO) and anti-LC3 (MBL, Nagoya). Clinical response was assessed based on the RECIST criteria. The Wilcoxon rank-sum test and chi-square test were used for the statistical analysis. Results: The expression of autophagy markers, beclin and LC3, in cancer cells showed significant increases by exemestane (beclin p=0.016; LC3 p=0.0004) whereas TUNEL did not show any change and M30 expression decreased (p=0.01). The increase of beclin expression was associated with the clinical response: responders showed an increase (p=0.039) while non-responders did not. Importantly, the treatment increased autophagy markers not only in cancer cells but in stromal cells (beclin p<0.0001; LC3 p=0.024) while it did not change TUNEL in stromal cells. Patients with stromal beclin-positive showed poor clinical response (3/12) and poor pathological response (0/12) while those with stromal beclin-negative showed good clinical response (26/39) and good pathological response (16/38) (clinical response p=0.011; pathological response p=0.0064). Conclusions: This study suggested that exemestane induced autophagy in both cancer and stromal cells. In addition, stromal autophagy correlated with clinical and pathological response to the endocrine treatment.