Abstract 5556: Monotherapy of anti-CXCL16 antibody is a potential therapeutic for macrophage-enriched triple-negative breast cancer by modulating tumor immune microenvironment and glutamine metabolism
Authors: Kim Min Joo , Sun Hyun Jin , Kang Geun-Hyung , Kim Seong Keun , Cho Sun Wook 
Published: June 2022

CXCL16, as a chemotactic cytokine, has been observed in various human solid cancers. The effects of CXCL16 on tumor behavior is controversial and showed tissue-specific manners. In breast cancers, previous studies have showed that CXCL16 mainly originated from mesenchymal stromal cells or cancer-associated fibroblasts and played pro-tumorigenic roles. CXCL16 is highly expressed in triple-negative breast cancers (TNBC) in TCGA dataset for breast cancer. This study aimed to investigate the therapeutic effects of CXCL16 neutralizing antibody and its mechanisms in TNBC. To establish a xenograft mouse model of TNBC, MDA-MB-231 cells were injected subcutaneously to athymic nude mice, and mice were randomized into anti-CXCL16 and control groups. When measurable tumors were established, anti-CXCL16 neutralizing antibody (CLS-A101, cellus inc.) or control IgG were intravenously injected. Tumor growth was significantly delayed in the anti-CXCL16 group than the control group by 67% for 3 weeks. Flow cytometric analysis showed that macrophages (CD11b+F4/80+ cells) and myeloid derived suppressor cells (MDSC, CD11b+GR1+ cells) were decreased in the anti-CXCL16 group than the control group. Histologic examination showed that anti-CXCL16 antibody significantly reduced tumor vessel formation and decreased macrophage infiltration in both intra- and peri-tumoral area. Collectively, treatment of anti-CXCL16 antibody reduced tumor growth by inhibiting macrophage and MDSC infiltration following reduced tumor angiogenesis. To explore the mechanistic insight into the monotherapy of anti-CXCL16 antibody, we further analyzed the metabolic changes. In human tumor tissues, TNBC harboring high expression of CXCL16 showed significant shift of glutamine metabolism pathway-related genes (upregulation of GLS and downregulation of GLUL, GLUD1, and GLUD2) toward accumulating glutamate. For cellular experiments, CXCL16-enriched cancer/macrophage co-cultured conditioned medium (co-CM) or cancer single-cultured conditioned medium (s-CM) were treated to cancer cells, and glutamine and glutamate levels were measured. In MDA-MB-231 cells, co-CM treatment significantly enhanced glutamate/glutamine ratio and anti-CXCL16 antibody significantly decreased it. Consistently, glutamate measures in tumor lysates from TNBC xenograft were lower in the anti-CXCL16 group than the control group. In conclusion, anti-CXCL16 antibody (CLS-A101) inhibited immune suppressive myeloid cell infiltration followed tumor angiogenesis and glutamate productions in cancer cells. These dual actions on both tumor immune microenvironment and cancer cell metabolism enables anti-CXCL16 antibody to be a potential monotherapy for TNBC.

Citation Format: Min Joo Kim, Hyun Jin Sun, Geun-Hyung Kang, Seong Keun Kim, Sun Wook Cho. Monotherapy of anti-CXCL16 antibody is a potential therapeutic for macrophage-enriched triple-negative breast cancer by modulating tumor immune microenvironment and glutamine metabolism [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 5556.