Abstract 5087: Combination therapy of immune checkpoint inhibitor and HIF1α/c-MET peptide vaccine suppresses metastasis by modulating tumor microenvironment in triple-negative breast cancer
Authors: Hong JinHwa , Lee Jimin , Lim Soon Young , Kim Ju Won , Lim Ah Reum , Park Kyong Hwa 
Published: April 2023

Abstract
Triple-negative breast cancer (TNBC) accounts for 20% of all breast cancer and has limited therapeutic option except for immunotherapy because ER, PR, and HER2 targeted for treatment are absent. It also tends to be more aggressive meaning more likely to metastasize faster to other organs such as lungs, liver, and bone, and its recurrence rate is high which leads to a poor prognosis. Immunotherapy is an option to treat TNBC such as programmed death ligand 1 (PD-L1) antibody. However, tumor cells use various immune evasion mechanisms in addition to PD-1/PD-L1 pathway to interrupt the effect of immunotherapy. Moreover, tumor microenvironment (TME) is one of the important factors for the effective anti-tumor immune responses from immunotherapy. Hypoxia is a typical event in TNBC. Hypoxia inducible factor 1-alpha (HIF1α) is a transcription factor that regulates angiogenesis by expressing VEGF, and in addition, upregulates the c-MET which increases the proliferation, migration, and survival of tumor cells. Moreover, HIF1α directly regulates the expression of CD47. CD47 is a transmembrane protein that binds to SIRPα of macrophages to inhibit the phagocytosis of macrophages. Therefore, the efficacy of immune checkpoint inhibitors decreases even if there is a higher degree of tumor-infiltrating lymphocytes (TILs). Combination therapy with immune checkpoint and tumor associated antigens (TAAs) derived peptide vaccine could inhibit metastasis. In present study, we found that HIF1α/c-MET peptide vaccination delayed metastasis in C3(1)Tag mouse. We also investigated whether combination therapy with immune checkpoint inhibitors and peptide vaccine inhibited metastasis. Next, we observed that combination strategy of HIF1α/c-MET peptide vaccine and treated anti-PD-L1 antibody or/and anti-CD47 antibody was more effective in systemically inoculated M6 cells growth in C3(1)Tag mice. Immunohistochemical analysis of the tumors showed that the protein expression of CD47, HIF1α, and c-MET were significantly decreased. On the other hand, CD4+ T cells, CD8+ T cells and M1 macrophages increased, but M2 macrophages decreased, resulting in delayed metastasis in combination therapy group compared to single therapy and control group. In addition, IFNγ ELISPOT showed that peptide vaccination significantly increased the HIF1α/c-MET specific IFNγ-secreting T cell response in splenocytes. We also assessed osteoclastogenesis in bones, which showed reduction of osteoclast in combination therapy group compared to single therapy and control group.Taken together, combination therapy with immune checkpoint inhibitor targeting PD-L1 and CD47 and peptide vaccine appears to be a promising strategy that inhibit metastasis by modulating tumor microenvironment in triple negative breast cancer.
Citation Format: JinHwa Hong, Jimin Lee, Soon Young Lim, Ju Won Kim, Ah Reum Lim, Kyong Hwa Park. Combination therapy of immune checkpoint inhibitor and HIF1α/c-MET peptide vaccine suppresses metastasis by modulating tumor microenvironment in triple-negative breast cancer. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 5087.