Abstract 3304: Gene expression profiling of full-thickness skin after FLASH proton radiotherapy

Abstract

Abstract Purpose: To investigate the transcriptomic changes induced by FLASH proton radiotherapy (F-PRT) that could be responsible for the protection of normal epithelial tissues by radiation-induced toxicities as have been previously shown by us and others. Methods: C57BL/6J mice received 30 Gy of F-PRT or S-PRT to the hind leg at respective dose rates of 69-124 Gy/sec or 0.39-0.65 Gy/sec. RNA sequencing was performed using full-thickness leg skin at 5 days after radiation revealing major pathways regulated by F-PRT and S-PRT. In an endeavor to identify the full repertoire of cells and gene expression profiles that are involved in the sparing effects of FLASH PRT, we expanded our studies to include single-cell RNA sequencing (sc-RNA seq) and examined additional time points such as Day 2 and Day 10 after radiation. Single-cell transcriptome libraries were generated on a 10X Genomics Chromium system. Datasets were acquired from cell samples derived and sequenced from pooled skin samples of three mice per group. Skin from the sequenced mice was also embedded for spatial analysis of gene expression. Results: RNA sequencing revealed that F-PRT uniquely upregulates almost four times more genes compared to S-PRT (F-PRT-uniquely upregulated 489 genes vs S-PRT-uniquely upregulated 129 genes). Also, F-PRT uniquely downregulated 178 genes, compared to the 125 genes uniquely downregulated by S-PRT. GO analysis demonstrates that the keratinization and apoptosis pathways are uniquely upregulated by S-PRT, whereas F-PRT uniquely upregulates genes involved in vascular development pathway. During submission of the abstract, analysis of sc-RNA seq samples was pending. Conclusion: Our comprehensive studies inform on the transcriptomic profiling of skin cell populations that are affected by F-PRT vs S-PRT; this insight will further spur discoveries on the biology of FLASH radiotherapy effects. Citation Format: Anastasia Velalopoulou, Ilias V. Karagounis, Giorgos Skoufos, Ioannis I. Verginadis, Michele Kim, Khayrullo Shoniyozov, Artemis G. Hatzigeorgiou, Eric Diffenderfer, Lei Dong, James Metz, Constantinos Koumenis, Keith A. Cengel, Amit Maity, Theresa M. Busch. Gene expression profiling of full-thickness skin after FLASH proton radiotherapy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 3304.