(0638) Effect of Radiation on the Secretome and Viability of Cutaneous Squamous Cell Carcinomas and Schwann Cell Lines

Introduction: Perineural invasion (PNI) is a predictor of poor prognosis for head and neck cutaneous squamous cell carcinoma (cSCC) patients. The molecular mechanisms underlying PNI remain largely unknown, with recent evidence suggesting it involves reciprocal signaling between cancer and nervous system cells mediated by secreted molecules. One treatment that has been shown to clinically improve outcomes for PNI-positive disease is adjuvant radiation therapy (aRT). In our study, we aim to analyze and compare the secretome of irradiated and non-irradiated cancer and Schwann cells.

Methods: A human cSCC (cSCC-A431) and 2 Schwann (HS11, FHSC) cell lines were cultured in their respective media and irradiated with one fraction of radiation at 0, 2, 4, or 8 Gray. Conditioned culture media were harvested on post-irradiation day 2 and a cytokine array was performed for each experimental condition. Arrays were imaged on a chemiluminescence imager and analyzed using ImageJ software. CellTiter-Glo assays were used to assess cell viability on post-irradiation day 4.

Results: cSCC-A431, HS11, and FHSC cells secreted several cytokines into the conditioned media, including chemokine ligand 5 (CCL5), monocyte chemoattractant protein 1 (MCP-1), interleukin 6 (IL-6), interleukin 8 (IL-8), and macrophage inflammatory protein 3 alpha (MIP-3-alpha). Among these cytokines, the secreted concentration of IL-8 changed most significantly between radiation doses across cell lines, with higher expression at 2 Gy compared to 0 Gy in both cSCC and Schwann cells. There was no statistically significant decrease in cell viability in all cell lines between 0 and 2 Gy, signifying the observed differences in secreted cytokine concentrations are due to changes in cellular physiology rather than post-irradiation cell viability.

Conclusions: Radiation modulates the secretion of several cytokines by cSCC and Schwann cells. A better understanding of the molecular crosstalk between cancer and supporting nerve cells may provide insight into the biology of PNI and how adjuvant radiation slows PNI progression.