Abstract 1104: Gene expression profile analysis of hyperthermia-induced radiosensitivity in breast cancer

Abstract Hyperthermia treatment of tumors (43-47°C) is used to sensitize breast cancer tumors to radiotherapy. Thermoradiotherapy significantly increases complete response rate and provides a treatment modality for more aggressive forms of the disease for which treatment options are generally more limited. However, the cellular mechanism underlying hyperthermia-induced radiosensitivity remains unclear. To better understand this phenomenon, we analyzed microarray data from four cell lines following treatment at 45°C for 30 minutes (Gene Expression Omnibus GSE48398). Three of the cell lines, MDA231 (37ºC, n=6; 45ºC, n=3), MDA486 (37ºC, n=6; 45ºC, n=3), and MCF7 (37ºC, n=6; 45ºC, n=6), were malignant breast cancer cell lines. The fourth cell line, MCF10A (37ºC, n=3; 45ºC, n=3), was from non-malignant mammary epithelial tissue. We identified 164 DEGs (adjP < 0.05, Fold change > 2) shared between the four cell lines and 182 DEGS shared by the three cancerous cell lines. Genes involved in radiosensitivity regulation as identified by dbCRSR, a database of radioresistance genes, were significantly dysregulated (Chi-squared test, p = 0.04). Gene ontology analysis using Cytoscape (v3.8.2) found 53 significantly enriched GO terms from an analysis off the DEGs (Benjamini-Hochberg adjP < 0.05). In particular, DEGs were enriched in processes involving G2 cell cycle arrest, apoptosis, and DNA damage checkpoints (adjP<0.005). We identified nine significantly enriched KEGG pathways, which included the ErbB (adjP=0.02), p53 (adjP=0.03), and PD-1 (adjP=0.02) cancer signaling pathways. We constructed a STRING protein-protein interaction network and then identified the 20 DEGs which had the greatest number of interactions. Identification of key genes in regulating hyperthermia-induced radiosensitivity were identified out of these 20 genes using two criteria: 1) overlap with two cancer signaling pathways and 2) involvement in radiosensitivity regulation. PTEN, a tumor suppressor overexpressed by up to 3.2-fold in vitro following hyperthermia, was identified as a key gene that may regulate hyperthermia-induced radiosensitivity in breast cancer. Distinct patterns of gene expression existed between breast cancer cells treated with hyperthermia and non-treated cells. Our data suggest that hyperthermia may exert its effects through arresting cells in the G2 phase, a particularly radiosensitive section of the cell cycle. Understanding the genes and pathways responsible for the heat-induced sensitization of breast cancer will allow us to exploit genetic alterations in tumors and develop non-invasive thermoradiotherapy regimens that more specifically target the tumor. Our study provides the basis for further investigation of genes regulating heat-induced radiosensitization and its molecular mechanism in breast cancer. Citation Format: Kevin Jili Tu, Hong Zhang, Dario Rodrigues, Jason K. Molitoris, Amit Sawant, Hem D. Shukla. Gene expression profile analysis of hyperthermia-induced radiosensitivity in breast cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 1104.