Abstract 5286: M2 to M1 repolarization of tumor-associated macrophages via the lysosomal effect of itraconazole
Authors: Takimoto Yumi , Tsubamoto Hiroshi , Sakata Kazuko , Isono-Taniguchi Roze , Ueda Tomoko , Shibahara Hiroaki 
Published: March 2024

Objective: Itraconazole (ITZ), an antifungal agent, has been reported to have tumor agnostic anticancer effects. Previous reports have shown prolonged survival in patients with lung and ovarian cancer who received ITZ. The anticancer mechanisms vary depending on the cancer type and stromal cells. Based on our previous studies, we focused on tumor-associated macrophages (TAMs).

Methods: Anti-tumorigenic M1 and pro-tumorigenic M2 macrophages were established from THP-1 cells and their phenotypes were determined based on morphology, cell surface antigens by Western blotting, and secreted proteins by ELISA. Bulk proteomic analysis of cell proteins was conducted using liquid chromatography-tandem mass spectrometry. The viability of CaSki cervical cancer cells was evaluated both in culture with the supernatant and co-culture with M2 macrophages after treatment with ITZ (10-5 M). Single-cell RNA sequencing (scRNA-seq) with surface labeling of M2 macrophages with and without the ITZ was performed. Using LoupeBrowser (10x Genomics, Inc.), ITZ-treated M2 macrophages were divided into two groups, one with newly emerged clusters after ITZ treatment (group 1) and the other (group 2). Differentially expressed genes between group 1 and group 2 were identified based on a two-fold and a 0.05 adjusted p value and were subjected to Reactome pathway analysis. Significant pathways were identified based on both p value &lt; 0.05 and FDR &lt;0.3. A triple-labeling immunofluorescence study was conducted to detect cholesterol, IL-1β, and organelles (the endoplasmic reticulum, phagosome, and lysosome).

Results: ITZ changed M2 macrophages to M1-like morphology and protein expression. While co-culture with M2 macrophages promoted cancer cell proliferation, both culture with the supernatant and co-culture with ITZ-treated M2 macrophages significantly inhibited CaSki cell growth. scRNA-seq identified newly emerged clusters (group 1) among M2 macrophages following ITZ treatment. Group 1 had elevated mRNA expression of M1 markers, including IL1β, IL6, CD86, TL4, GAPDH, and RKM, compared to group 2. Group 1 expressed the CD86 and TLR4 surface antigen proteins. Pathway analysis identified 176 significant pathways including lysosome vesicle biogenesis. Immunofluorescence analysis showed that M1-like macrophages in ITZ-treated M2 macrophages had enlarged lysosomes containing cholesterol.

Conclusion: ITZ repolarized THP-1 derived M2 macrophage to an M1-like phenotype. The mechanism of repolarization involves intracellular cholesterol accumulation via lysosomal dysfunction.

Citation Format: Yumi Takimoto, Hiroshi Tsubamoto, Kazuko Sakata, Roze Isono-Taniguchi, Tomoko Ueda, Hiroaki Shibahara. M2 to M1 repolarization of tumor-associated macrophages via the lysosomal effect of itraconazole [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(6_Suppl):Abstract nr 5286.