Abstract 6803: TRIM16 regulates IL-6 secretion in head and neck cancer-associated fibroblasts

Abstract

Abstract Despite current therapy, head and neck squamous cell carcinoma (HNSCC), the 7th most common cancer worldwide, is associated with high morbidity and mortality. Response to current therapies could be improved with a better understanding of the tumor microenvironment of HNSCC. We previously reported that cancer-associated fibroblasts (CAFs), the most abundant stromal cell type in the HNSCC microenvironment, have elevated levels of basal autophagy than oral fibroblasts from cancer-free subjects (NF). Disrupting autophagy in CAFs with Beclin-1 siRNA reduced secretion of IL-6, IL-8, and other factors known to promote HNSCC progression. The recent emerging role of autophagy in secretion of tumor promoting factors has high impact because (i) the mechanism can provide a new target to block the secretion of protumor factors from CAFs that contribute to HNSCC progression, and (ii) these cytokines can serve as potential indicators for the efficacy of autophagy-targeted therapies. To this end, we carried out an unbiased assessment of the proteins associated with autophagosomes in primary CAFs from HNSCC samples using mass spectrometry. We performed immunoprecipitation of LC3B from the isolated small vesicles of the CAFs, identified and validated the association of several trafficking proteins in secretory autophagy including VAMP3 and SNAP23. Further, the tripartite motif (TRIM) proteins have been shown to mediate the fate of autophagosomes either for degradation or secretion. We hypothesized that TRIM proteins are involved in transport of secretory autophagosomes. Our data demonstrate CAFs express higher levels of TRIM16 mRNA than NF. We demonstrate immunogold labeling of TRIM16 or IL-6 localized to the autophagosomes using transmission electron microscopy. Further, using immunofluorescence, we demonstrated the colocalization of TRIM16 and IL-6, as well as IL-6 and LC3B in cytoplasmic puncta. In addition, we used proximity ligation assays to confirm the interaction of TRIM16 and IL-6, as well as IL-6 and LC3B. TRIM16 knockdown using siRNA in CAFs reduced the secretion of IL-6 as measured by ELISA. In conclusion, we demonstrate an important role of TRIM16 in secretory autophagy making it a potential therapeutic target to mitigate CAF-mediated HNSCC growth. Citation Format: Thuc Ly, Bailey Pickard, Avisha Pandey, Noraida Martinez-Rivera, Eduardo Rosa-Molinar, Michael Washburn, Wen-Xing Ding, Sufi Mary Thomas. TRIM16 regulates IL-6 secretion in head and neck cancer-associated fibroblasts [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 6803.