Abstract PR013: Association of a polymorphic variant in JMJD1C with response to chemoradiotherapy in rectal cancer and head and neck cancer: Implications for a diverse population
Authors: Hasan Adria , Demidova Elena , Czyzewicz Philip , Shah Shreya , Devarajan Karthik , Galloway Thomas J. , Einarson Margret B. , Burtness Barbara , Golemis Erica A. , Meyer Joshua E. , Arora Sanjeevani 
Published: December 2023

Abstract
Neoadjuvant chemoradiotherapy (nCRT) is the standard treatment for locally advanced rectal cancer (LARC). Although nCRT has improved outcomes for many patients, ~70-80% of patients show poor or no response, and CRT is toxic. No biomarker exists that can predict which patients may benefit from nCRT. CRT efficacy arises from unrepaired double-strand breaks (DSBs). Recent work has suggested that dynamic changes in lysine modification of chromatin regulate DSB repair. This study investigated the association of germline single nucleotide polymorphisms (SNPs) in lysine-modifying genes with DSB repair and CRT outcomes in LARC. The LARC patients (n=84) were segregated into poor (PoR) and complete (CR) responders using the Neoadjuvant Rectal score. Blood DNA was sequenced to identified SNPs, matched LARC patient-derived cells were tested for sensitivity to DNA damage, and results correlated. Significant SNP-response correlations were confirmed in an independent cohort of CRT-treated head and neck squamous cell carcinoma (HNSCC) patients who had received chemoradiation (n=90). The HNSCC patients were segregated into 3 groups based on response: disease-free (n=30), recurrent disease (n=28), and never-disease free (n=32). Isogenic HNSCC lines with either the wildtype (WT) or SNP were generated using CRISPR/Cas9 technology, and bulk RNA sequencing and immunofluorescence-based studies were performed to assess pathways affected. LARC CRs were significantly enriched versus PoRs for a germline SNP in the lysine H3K9 demethylase, JMJD1C, resulting in a missense variant (discovery (n=30, p&lt;0.00001), validation (n=54, p=0.001); Fisher’s Exact). In the HNSCC cohort, the JMJD1C SNP was significantly associated with no recurrence (p=0.0003, Fisher’s Exact). LARC patient-derived cell lines carrying the SNP were significantly more sensitive to DSB damage versus those carrying the WT (n=12, p&lt;0.001, Mann-Whitney). Cells bearing the SNP were significantly enriched for altered mRNA levels of genes associated with DNA repair compared with WT cells (q-value&lt;0.05). On irradiation, the SNP cells showed robust activation of DSB repair (γH2AX, BRCA1 foci, JMJD1C nuclear localization) versus the WT cells. Finally, analysis of the JMJD1C SNP frequency in large population datasets found that while it was abundant in European Americans (EAs), it is relatively rare in African Americans (AAs) (EA= 0.3139 vs. AA=0.072; gnomAD population). This study provides novel insight into a SNP in a lysine-modifying gene affecting DSB repair that may serve as a predictive biomarker for CRT response in 2 different cancer types. Our data suggest that host genetics impact DSB repair and warrant further investigation to better understand disparities in response to CRT. Future research will further explore the racial/ethnic disparities in tumor recurrence and confirm results in in vitro and in vivo models of cancer, and in large patient datasets.
Citation Format: Adria Hasan, Elena Demidova, Philip Czyzewicz, Shreya Shah, Karthik Devarajan, Thomas J. Galloway, Margret B. Einarson, Barbara Burtness, Erica A. Golemis, Joshua E. Meyer, Sanjeevani Arora. Association of a polymorphic variant in JMJD1C with response to chemoradiotherapy in rectal cancer and head and neck cancer: Implications for a diverse population [abstract]. In: Proceedings of the 16th AACR Conference on the Science of Cancer Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; 2023 Sep 29-Oct 2;Orlando, FL. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2023;32(12 Suppl):Abstract nr PR013.