Includes legends for all supplementary figures. S1: CAFs exhibit increased LC3 puncta per cell compared to NF. S2: CAF autophagy inhibition significantly decreases HNSCC in vitro progression. S3: IL-6 and IL-8 induce fibroblast autophagy. S4: bFGF treatment increases autophagy regulated secreted factors. S5: Autophagy inhibition reduces HNSCC in combination therapy, and does not affect CAF proliferation.
ARTICLE ABSTRACTDespite therapeutic advancements, there has been little change in the survival of patients with head and neck squamous cell carcinoma (HNSCC). Recent results suggest that cancer-associated fibroblasts (CAF) drive progression of this disease. Here, we report that autophagy is upregulated in HNSCC-associated CAFs, where it is responsible for key pathogenic contributions in this disease. Autophagy is fundamentally involved in cell degradation, but there is emerging evidence that suggests it is also important for cellular secretion. Thus, we hypothesized that autophagy-dependent secretion of tumor-promoting factors by HNSCC-associated CAFs may explain their role in malignant development. In support of this hypothesis, we observed a reduction in CAF-facilitated HNSCC progression after blocking CAF autophagy. Studies of cell growth media conditioned after autophagy blockade revealed levels of secreted IL6, IL8, and other cytokines were modulated by autophagy. Notably, when HNSCC cells were cocultured with normal fibroblasts, they upregulated autophagy through IL6, IL8, and basic fibroblast growth factor. In a mouse xenograft model of HNSCC, pharmacologic inhibition of Vps34, a key mediator of autophagy, enhanced the antitumor efficacy of cisplatin. Our results establish an oncogenic function for secretory autophagy in HNSCC stromal cells that promotes malignant progression. Cancer Res; 77(23); 6679–91. ©2017 AACR.