Increased risk of cognitive impairment or dementia in women who underwent oophorectomy before menopause

Emerging evidence has unveiled the contribution of tumor microenvironment to the regulation of chemotherapeutic outcomes. However, the impact of chemotherapy on anti-tumor immunity and immunosuppression still remains elusive. In this study, we investigated the role of chemotherapy-derived inflammatory responses in the differentiation of myeloid-derived suppressive cells (MDSC). The anti-cancer agents Gemcitabine and Carboplatin induced the activation of MAPK pathway in mouse mammary cancer cell line EO771 and also stimulated cytokine and chemokine production including GM-CSF and IL-6. The supernatants of Gemcitabine-treated tumor cells promoted more bone marrow-derived monocytic MDSC differentiation, and enhanced their immunosuppressive activity on effector T cells. The expression of MDSC associated molecules such as Arginase and iNOS significantly increased in M-MDSC induced by the supernatant of Gemcitabine-treated tumor cells. In vivo treatment of EO771 tumors with Gemcitabine increased the suppressive function of MDSC. Our findings also suggest that Dectin-1 activation by β-glucan could significantly reduce MDSC suppressive function. Together, these results describe a role of chemotherapy-derived inflammation in the modification of chemotherapy-treated tumor microenvironment and suggest the targeting of Dectin-1 signaling may benefit cancer patients by reprogramming MDSC in chemotherapy setting.