Abstract 2882: Investigating mechanisms of radioresistance in TYK2 knockout head and neck cancer cells

Abstract

Abstract Radiation therapy is the primary form of treatment of head and neck squamous cell carcinoma (HNSCC). However, more than half of patients experience disease progression with standard of care treatment. To investigate novel therapeutic targets, a CRISPR screen was done to identify genes that are associated with radioresistance. The screening results indicated that JAK1 and TYK2 knockout (KO) resulted in radioresistance in HNSCC. Preliminary data suggests that loss of JAK1 causes an enhanced G2/M arrest phenotype and enhanced genome stability that contribute to radioresistance. To investigate whether TYK2 KO caused changes to the cell cycle and genome stability as observed in JAK1 KO, Western blots, cell cycle assays, and micronuclei staining experiments were performed. Cal27, a HNSCC cell line, was used. Cal27 cells were transduced with a non-targeting control (NT2) guide RNA (gRNA) or two different gRNAs targeting TYK2 to generate TYK2 KO cells. Western Blot analysis was performed to determine changes in signaling upon TYK2 KO. Additional conditions included radiation and treatments with Interferon gamma, Interferon alpha and Interleukin-6 to activate the canonical JAK-STAT pathways. Overall, there were minimal changes in downstream signaling between the treatments and the knockouts. Cell cycle analysis via flow cytometry revealed no changes between the NT2 and TYK2 KO cells, potentially corroborating signaling results. Forty percent of TYK2 KO cells were arrested at the G2/M checkpoint at 8 hrs and 24 hrs after radiation treatment, but twenty percent returned to the G1 phase at 24 hrs. This indicates that loss of TYK2 is not responsible for cell cycle arrest. Lastly, micronuclei formation was observed to measure genomic instability. Twenty thousand Cal27 NT2 and TYK2 KO cells were seeded. They were allowed to incubate for 48 hrs before treatment with 4 Gy. Micronuclei staining revealed minimal differences between NT2 and TYK2 KO cell lines, although there were significant differences between the control and the radiation groups. Overall, radioresistance by TYK2 KO is not caused by changes in cell cycle or genomic instability as demonstrated with JAK1 KO. To understand how TYK2 is causing radioresistance in HNSCC, next steps would be to see if there are changes in proliferation. If MTT assays demonstrate significant changes, downstream signaling in growth pathways will be measured. If there is no increased proliferation, we will examine changes in DNA damage repair. Citation Format: Nicole Mayerli Constante, Vanessa Kelley, Joseph Contessa. Investigating mechanisms of radioresistance in TYK2 knockout head and neck cancer cells [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 2882.