Head and Neck Squamous Cell Carcinoma Patient-Derived Cancer-Associated Fibroblasts Undergo Senescence While Retaining Protumorigenic Properties After Ex Vivo Irradiation.

Abstract

The majority of patients with head and neck squamous cell carcinoma (HNSCC) receive radiation therapy (RT) as part of their treatment plan. Even though RT is highly effective in HNSCC, therapeutic efficacy for advanced HNSCC is relatively low; one-third of patients with HNSCC treated with RT experience locoregional relapse within 5 years after treatment. Cancer-associated fibroblasts (CAFs) are one of the most prominent cell types in the tumor microenvironment in advanced HNSCC and play a key role in therapy resistance. Here, we characterize the response of primary human HNSCC-derived CAFs to radiation and its consequences for CAF function and explore the targetability of radiation-induced senescent CAFs. Using primary human HNSCC-derived CAFs, we show that CAFs survive single-dose RT ≤68 Gy, and fractionated doses of 3 × 8 Gy; CAFs do not die but go into senescence after radiation. Importantly, we show that the CAF secretome is capable of enhancing both HNSCC cell proliferation and migration, and that CAFs retain these capabilities after radiation. Lastly, we demonstrate that irradiated CAFs display increased sensitivity to Navitoclax (ABT-263), a senolytic drug that selectively induces cell death in senescent cells. This work highlights the importance of CAFs in RT and offers rationale for exploring combinations of RT and CAF-targeting approaches in HNSCC.