Progesterone-induced immunosuppression in breast cancer is mediated by the coordinated action of different immune escape mechanisms

MARIANA SALATINO; TOMÁS DALOTTO; DIEGO O. CROCI; VICTORIA SUNDBLAD; SEBASTIÁN DERGAN-DYLON; JUAN MARTÍN ILARREGUI; MARTA TOSCANO; GABRIEL A. RABINOVICH

Buenos Aires

Congreso; First French-Angentine Immunology congress (FAIC); 2010

Sociedad Argentina de Inmunología y Sociedad Francesa de Inmunología

Based on the anti-inflammatory and tolerogenic properties of progesterone and its ability to promote breast cancer progression, we sought to examine whether progesterone creates an immunosuppressive tumor microenvironment, either by controlling galectin-glycan interactions, favoring the secretion of inhibitory cytokines such as TGF-£] or inducing the differentiation of regulatory T cells (Tregs). The progesterone analogue medroxiprogesterone acetate (MPA) markedly up-regulated expression of galectin-1 in two hormone-dependent human breast cancer cell lines and in a mouse mammary adenocarcinoma (C4HD) at both protein and mRNA levels (2-3 folds). This effect was abrogated by pre-treatment with the antiprogestin RU486 indicating that the progesterone receptor was involved. In vitro MPA-treatment of mouse splenocytes induced a significant increase in the frequency of Tregs (Ct 5¡Ó0.4%, MPA 10-7M 18¡Ó1.8%; p<0.01), skewed the balance toward a Th2-type cytokine profile (IFNƒ×/IL-10 Ct 25¡Ó2, MPA 3¡Ó0.4; p<0.01) and induced a dose-dependent inhibition of T-cell proliferation (MPA 10-7M 50% inhibition). In vivo MPA-treatment of C4HD tumor-bearing mice increased the frequency of Tregs in spleen (Ct 11¡Ó0.4%, MPA 17¡Ó2%), tumor-draining lymph nodes (Ct 10¡Ó0.4%, MPA 15¡Ó1.7%; p<0.05) and tumor microenvironment (Ct 12¡Ó4% MPA 25¡Ó6%; p<0.05).  Augmented frequency of Treg cells induced by MPA was associated with increased synthesis of TGF-£]1 and up-regulated expression of the SMAD4 transcription factor (3-fold) in splenocytes suggesting a progesterone-regulated axis involving galectin-1, Treg cells and the TGF-£] pathway. Finally, progesterone favored the homing of Tregs to tumor sites through induction of tumor-derived CCL22 (2-fold increase). Our results demonstrate that progesterone hierarchically fosters an immunosuppressive tumor microenvironment by co-ordinately regulating galectin-1 expression, stimulating the TGF-£] pathway and augmenting the frequency of Treg cells.