Page 20 - M. Immunology

[M. Immunology-13]

Microphthalmia-associated transcription factor (MITF)

regulates function of myeloid-derived suppressor cells in

tumor microenvironment

Haesun Park¹, Aram Lee¹, Jihyun Lim¹, Jong-Seok Lim¹

¹Biological Science, Sookmyung Women's University, Seoul 04310, Republic of Korea

Myeloid-derived suppressor cells (MDSCs) are immature myeloid cells and known to have immunosuppressive
functions. MDSCs, one of the major components of the tumor microenvironment (TME), contribute to tumor
progression. Microphthalmia-associated transcription factor (MITF) modulates proliferation and development of

melanocytes. Recently, MITF has been evaluated for its function in development of non-pigment cells including
osteoclasts and mast cells. However, the role of MITF in the regulation of immune cells remains to be elusive. In

this study, we investigated the functional role of MITF in MDSCs in TME. We observed the increase of MITF
expression in murine bone marrow-derived MDSCs (BM-MDSCs) cultured with TCCM. It was accompanied by the

up-regulation of MDSC activation markers, such as IL-10, iNOS and arginase 1. In addition, a MITF inhibitor
suppressed the expression of MITF and MDSC activation markers. In contrast, the increase of MITF expression by

IBMX induced up-regulation of expression of MDSC activation markers. Especially, HIF1α regulating function of
MDSCs significantly decreased in MDSCs treated with MITF inhibitor. Collectively, our data suggest that modulation

of MITF expression might regulate the immune suppressive function of MDSCs.