Caspase-8-dependent autophagy regulates neutrophil infiltration in oral squamous cell carcinoma.

Oral squamous cell carcinoma (OSCC) is a subtype of head and neck cancer that arises in the multilayered epithelia of the mouth and lips. Although inactivating mutations in CASP8 are frequently found in human OSCC their role in the disease is unknown. To investigate this, we deleted Casp8 in the oral epithelium of adult mice. Loss of Caspase-8 resulted in defects in the tongue epithelial barrier and triggered a neutrophil-rich immune infiltrate distinct from that observed on epidermal Casp8 deletion. Oral Casp8 deletion led to activation of autophagy. Inhibition of autophagy partially rescued epithelial integrity in Casp8(-/-) mice, while induction of autophagy in wild type mice resulted in oral barrier defects and excessive neutrophil infiltration. On treatment with the carcinogen 4-nitroquinoline-1-oxide Casp8(-/-) mice showed increased susceptibility to developing oral tumors. Depletion of neutrophils reduced tumor incidence, which correlated with a reduction in reactive oxygen species and decreased epithelial DNA damage. Our findings establish a functional link between epithelial integrity, autophagy, and the tumor immune microenvironment, placing Caspase-8 at the center of these processes.