Abstract 3930: The therapeutic implications of consensus genomic subtypes of gastric adenocarcinoma

Abstract Background: Gastric adenocarcinoma (GAC) is heterogeneous lethal disease in genomic and clinical level. Although the clinical relevance of genomic and molecular subtypes of GAC has been demonstrated, differences in classification methods have made it difficult to use these findings in clinical applications. We aim to examine a consensus of genomic subtypes and correlate them with clinical outcomes. Method: We collected genomic data from 2527 GAC tumors and divided the data into discovery (n = 1427) and validation sets (n = 1100). A cluster of clusters approach (COCA) was used to find consensus subtypes of gastric tumors. We constructed the GAC predictor of the integrated consensus subtype with 120 genes (GPICS120) and applied it to the validation data set in order to validate the clinical significance of the new subtypes. By analyzing genomic and proteomic data we evaluated each subtype's potential response rate to standard and experimental treatments such radiation therapy, targeted therapy, and immunotherapy and further validated their functional significance in cell line models. Results: We identified 6 clinically and molecularly distinct genomic consensus subtypes (CGSs) by integrating 8 previously established genomic subtypes. CGS1 is characterized by worst prognosis, remarkably high stem cell characteristics, high IGF1 expression, and low genomic alterations. CGS2 showed canonical epithelial gene expression patterns. CGS3 and CGS4 are characterized by high copy number alterations and low immune activity. CGS5 has highest mutation burden and moderately elevated immune activity that is characteristics of MSI-high tumors. The majority of CGS6 tumors have extremely high methylation, high immune activity, and are EBV-positive. The most intriguing finding is that CGS1 is the most responsive to immunotherapy whereas CGS3 is significantly associated with benefit of chemoradiation therapy due to high basal level of ferroptosis. Furthermore, we showed that ferroptosis inducer statin sensitized radiation-resistant GAC cells to ionizing radiation, suggesting that statin can be used to enhance the efficacy of chemoradiation in GAC and it would warrant further investigation in preclinical models. Conclusion: Consensus subtype is robust classification system and can serve as the basis for future clinical trials as well as pre-clinical research into targeted subtype-based therapies. Citation Format: Yun Seong Jeong, Young-Gyu Eun, Sung Hwan Lee, Sang-Hee Kang, Sun Young Yim, Eui Hyun Kim, Joo Kyung Noh, Bo Hwa Sohn, Ju-Seog Lee. The therapeutic implications of consensus genomic subtypes of gastric adenocarcinoma [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 3930.