Abstract PO-061: Deciphering radiation resistance in head and neck cancer using patient derived organoids

Radiation therapy (RT) is an integral component of the standard of care for patients with head and neck squamous cell carcinoma (HNSCC). While advances in radiation delivery methods have led to improved outcomes, radioresistance poses a significant therapeutic challenge and a major cause of poor prognosis in this patient population. To date, a majority of studies investigating mechanisms of radioresistance have employed in vitro monolayer cell culture models that lack the heterogeneity and cell-extracellular matrix interactions. To overcome this limitation, we established and credentialed a panel of 3D patient-derived organoid (PDO) models of HNSCC to identify molecular signatures and signaling pathways that contribute to radiation resistance. A total of 7 PDOs were established from surgical HNSCC specimens and credentialed using a combination of histologic/immunohistochemical evaluation (H&E, cytokeratin, p16), genotyping (HPV), whole exome sequencing (WES) and RNA sequencing analysis. Radiation response of the PDO panel was also examined and assessed for concordance with patient response and PDOs were ranked based on their radiosensitivity and bioinformatic analysis was performed on radiosensitive and radioresistance PDOs to identify molecular pathways associated with resistance. All PDOs retained the histology, p16/HPV status and mutational landscape (p53, HLA-A) of donor patient tissues. Radiation response of PDOs showed excellent (100%) concordance with patient responses (n=5 with history of radiation treatment). RNA-seq revealed identified pathways associated with epithelial mesenchymal transition (IGFBP2, TIMP1, TIMP2, LAMA3, LOXL1), NOTCH signaling (NOTCH1, HES1, FZD1, FZD5, DTX1, NOTCH3, FZD7), E2F targets and G2M checkpoint signaling (MCM2, MCM7, MCM4, PCNA) and the p53 pathway (SFN, NDRG1, ALOX15B). Collectively, our findings illustrate the translational utility of PDOs as a robust platform in identifying potential therapeutic targets that could overcome radiation resistance in HNSCC. Ongoing studies are evaluating the potential of PDOs to serve as a screening platform to identify radiosensitizers through repurposing of FDA-approved drugs to facilitate rapid clinical translation. Citation Format: Vui King Vincent-Chong, Christian Gluck, Pamela A. Hershberger, Satrajit Sinha, Mukund Seshadri. Deciphering radiation resistance in head and neck cancer using patient derived organoids [abstract]. In: Proceedings of the AACR Virtual Special Conference on Radiation Science and Medicine; 2021 Mar 2-3. Philadelphia (PA): AACR; Clin Cancer Res 2021;27(8_Suppl):Abstract nr PO-061.