Abstract 5247: Reprogramming tumor microenvironment with intratumor macrophage adoptive cell therapy in melanoma

Abstract The interplay between tumor cells and immune cells within the tumor microenvironment (TME) dictates protumor or antitumor immune responses. Tumor-associated macrophages (TAMs) respond to signals of the TME and exhibit a spectrum of phenotypes ranging between M1 (antitumor) and M2 (protumor) macrophages. In most tumor types, including melanoma, the balance between M1 and M2 macrophages is critical with a higher M1/M2 ratio favoring antitumor immunity. Therefore, strategies enhancing the M1/M2 ratio can significantly alter the TME towards antitumor immunity. In this study, we administered luciferase and GFP-expressing M1 macrophages as an adoptive cell therapy (ACT) through intravenous (i. v) and intratumor routes respectively, into mice bearing SM1 murine melanoma tumors to determine the effective treatment modality. We reprogrammed antitumor M1 macrophages ex-vivo with HDAC6 inhibitors to lock into the M1 phenotype and administered intratumorally as ACT in the syngeneic SM1 murine melanoma and humanized NSG-SGM3 melanoma models. We performed histological analysis of tumors for macrophage markers, immune phenotyping of infiltrated immune cells, single-cell secretome analysis of tumor macrophages, and single-cell RNA-seq analysis of CD45+ immune cell populations to demonstrate the benefit of macrophage ACT. Tail vein injected, luciferase-expressing M1 macrophages localized in the lungs and spleen, failed to reach the tumor as visualized by IVIS imaging, suggesting that i. v administration is ineffective for macrophage therapy. On the contrary, intratumor M1 macrophage ACT resulted in diminished tumor growth. Single-cell RNA-seq analysis of the CD45+ sorted tumor-associated immune cell population revealed distinct macrophage subsets and a significant M1/M2 macrophage ratio increase. NicheNet cell-cell interaction analysis indicated that M1-like TAMs activated infiltrating T-cells and monocytes through ligand-receptor interactions. Trajectory analysis of infiltrated monocytes indicated differentiation toward inflammatory macrophages in ACT tumors. Flow cytometry analysis corroborated that ACT increased the M1/M2 macrophage ratio and an increase in CD8 effector T-cells. Furthermore, HDAC6i-treated macrophages increased antigen cross-presentation. Single-cell secretome analysis of F4/80+ TAMs by the Isoplexis platform revealed polyfunctionality of HDAC6-treated M1 macrophages secreting inflammatory cytokine Tnfa and T-cell recruiting chemokine Cxcl10. Histological examination of tumor sections for macrophage phenotypic markers suggested that transplanted macrophages retained the M1 phenotype post-ACT in both SM1 murine and NSG-SGM3 melanoma tumor models. We demonstrated the potential of reprogramming macrophages ex vivo with HDAC6 inhibitors as a feasible macrophage cell therapy to treat solid tumors. Citation Format: Satish Kumar Reddy Noonepalle, Nithya Gajendran, Manasa Suresh, Xintang Li, Maria D. Hernandez, Christian Zevallos Delgado, Nima Aghdam, Michael Berrigen, Tessa Knox, Karen Tan, Marie Durr, Eduardo Sotomayor, Katherine B. Chiappinelli, Duncan Wardrop, Anelia Horvath, Brett A. Shook, Norman H. Lee, Anatoly Dritschilo, Rohan Fernandes, Karthik Musunuri, Maho Shibata, Alejandro Villagra. Reprogramming tumor microenvironment with intratumor macrophage adoptive cell therapy in melanoma abstract. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts) ; 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84 (6Suppl): Abstract nr 5247.