Abstract 3929: The FAD-directed LSD1 specific inhibitor, INCB059872, inhibits cell migration and metastasis by suppressing premetastatic niche formation in a spontaneous metastasis mouse model
Authors: Lee Sang Hyun , Diamond Melody , Chadderton Antony , Liu Huiqing , Volgina Alla , Roman Valerie , Weber Michael , He Chunhong , Stewart Rebecca , Hertel Denise , Liu Phillip , Wu Liangxing , Oliver Julian , Yeleswaram Swamy , Roberts Alan , Yao Wenqing , Hollis Gregory , Huber Reid , Scherle Peggy , Ruggeri Bruce 
Published: August 2018

Abstract
The primary cause of cancer associated mortality is tumor metastasis. The concept of the tumor pre-metastatic niche is supported by evidence of changes at distal pre-metastatic sites that create a permissive environment to allow disseminated tumor cells to seed. Myeloid-derived suppressor cells (MDSCs) remodel the tumor microenvironment and function as immunosuppressive cells to promote tumor growth. Previously, we demonstrated that the clinical stage LSD1 specific inhibitor, INCB059872 significantly reshaped the myeloid compartment in the murine 4T1 syngeneic murine model of breast cancer. Treatment with INCB059872 significantly reduced the population of MDSCs in the tumor microenvironment. Since it has been reported that MDSCs promote establishment of a pre-metastatic niche, we hypothesized that INCB059872 could suppress or delay metastatic processes in the 4T1 model and thereby could impact spontaneous metastases to the lung. In vitro, INCB059872 significantly suppressed cancer cell migration of triple negative breast cancer cells, SUM145PT. In vivo, the effect of INCB059872 on forming the metastatic niche using the 4T1 mouse breast tumor model was explored. Vehicle treated animals exhibited a significant infiltration of MDSCs to the primary tumor and lungs prior to cancer cells metastasizing. In contrast, INCB059872 administration significantly suppressed the infiltration of MDSCs in primary tumor and lung tissues. Histological analyses further demonstrated the reduction of metastatic loci in lung with INCB059872 treatment. Plasma levels of CCL2, a cytokine which is required for the recruitment and functional specialization of MDSCs, were significantly reduced in animals treated with INCB059872. These data suggest a possible mechanism to reduce infiltration of MDSCs into lung tissues. Notably, analyses of molecular pathways using RNA-Seq identified that components of the EMT associated pathway are also downregulated in tumors treated with INCB059872, which further supports the role of INCB059872 in the inhibition of metastasis. Taken together, these preclinical data suggest that inhibition of LSD1 with INCB059872 can suppress metastasis through multiple molecular and cellular mechanisms, notably by inhibition of the formation of the pre-metastatic niche by modulating the population of MDSCs in the primary tumor and distal tissues.
Citation Format: Sang Hyun Lee, Melody Diamond, Antony Chadderton, Huiqing Liu, Alla Volgina, Valerie Roman, Michael Weber, Chunhong He, Rebecca Stewart, Denise Hertel, Phillip Liu, Liangxing Wu, Julian Oliver, Swamy Yeleswaram, Alan Roberts, Wenqing Yao, Gregory Hollis, Reid Huber, Peggy Scherle, Bruce Ruggeri. The FAD-directed LSD1 specific inhibitor, INCB059872, inhibits cell migration and metastasis by suppressing premetastatic niche formation in a spontaneous metastasis mouse model [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 3929.