Abstract B42: MDSCs accumulation within metastatic liver is modulated by CXCR4/CXCL12 axis after HSCs interaction with C26 in the ICAM-1 regulated inflammatory milieu
Authors: Benedicto Aitor , Romayor Irene , Arteta Beatriz 
Published: February 2019

Abstract
Introduction: Inflammation and immune suppression mediate tumor progression. During liver metastasis, tumor cells interact with and cross the hepatic sinusoidal line formed by liver sinusoidal endothelial cells (LSECs). In this inflammatory milieu, hepatic stellate cells (HSCs) are recruited into the nascent foci initiating the contact with the tumor cells. These cross-talks modulate the tumor microenvironment into a more tolerant one, in part by attracting myeloid derived suppressor cells (MDSCs). However, the mechanisms regulating the initiation of the inflammatory response and the recruitment of HSCs and MDSCs during the development of liver metastasis from colorectal cancer is not fully characterized. We aim to unmask mediators of the inflammatory response triggered after tumor cells interaction with LSECs and in the recruitment of HSC. Besides, the involvement of CXCR4/CXCL12 axis in the cross-talk between tumor cells and the recruited HSCs will be analyzed, with focus on the HSCs-mediated recruitment of MDSCs.
Methods: To do so, the involvement of primary LSECs and tumor cells in the levels of inflammatory factors were measured by ELISA. Afterwards, the effect of both tumor-activated LSECs and sICAM-1 activated C26 cells in the recruitment of HSCs and their secretion of promigratory factors was studied. Moreover, the expression and role of CXCR4/CXCL12 axis in amplifying the migratory potential of HSCs and C26 was determined by using CXCL12 and the CXCR4 antagonist AMD3100. Finally, the role of CXCL12-CXCR4 in the hepatic stellate cell and MDSCs recruitment during liver metastasis and disease progression was analyzed in vivo by means of AMD3100 treatment.
Results: Tumor-endothelial interplay increased secretion of IL-1β, IL-6, PGE2, and TNF-α, partly abrogated by blocking endothelial ICAM-1. Additionally, sICAM-1 activation of C26 could mimic this inflammatory response. Moreover, sICAM-1 stimulated CT26 derived medium significantly increased not only HSCs migration but also the matrix remodeling factors such as MMP-2 and uPA activity and the angiogenic factor VEGF. Additionally, tumor-derived conditioned medium promoted the expression of CXCR4, while CXCL12 increased the migratory potential of HSCs which was abrogated by blocking CXCL12/CXCR4 interaction through AMD3100. In vivo, the administration of AMD3100 revealed impaired infiltration of ASMA expressing HSCs into the metastatic lesions, along with reduced CD11b+Ly6G+ MDSC counts in the invaded organ. These observations were in line with 2-fold reduced metastatic area in AMD3100 treated mice liver.
Conclusions: We can conclude that ICAM-1 mediates the early inflammatory response driving to HSC recruitment and their contribution to matrix remodeling and angiogenesis. These recruited HSC increase their expression of CXCR4 which could amplify their response to CXCL12 and thus trigger a positive feedback recruiting more C26 and HSCs. In vivo, these recruited HSCs might induce the recruitment of MDSCs via CXCR4/CXCL12 axis decreasing the local immune response. Therefore, blocking CXCR4/CXCL12 axis might be a potential therapeutic strategy to increase the antitumor immune response by different mechanisms mediated by both tumor and stromal cells.
Citation Format: Aitor Benedicto, Irene Romayor, Beatriz Arteta. MDSCs accumulation within metastatic liver is modulated by CXCR4/CXCL12 axis after HSCs interaction with C26 in the ICAM-1 regulated inflammatory milieu [abstract]. In: Proceedings of the AACR Special Conference on Tumor Immunology and Immunotherapy; 2017 Oct 1-4; Boston, MA. Philadelphia (PA): AACR; Cancer Immunol Res 2018;6(9 Suppl):Abstract nr B42.