Abstract 5545: Assessing LGR5 expression levels on colorectal cancer tissue samples for use in LGR5-targeting CAR-T cell therapy clinical trial

Abstract Leucine-rich repeat containing G-protein coupled receptor (LGR5) is stem cell marker that potentiates canonical signaling in the Wnt/β-catenin signaling pathway (Barker et al. 2007). LGR5 is known to be expressed on several tissues; particularly the stem cells within intestinal crypts and the stem cell niche at the base of hair follicles (Barker et al. 2007 and Jaks et al. 2008). The plasticity and stem phenotype of LGR5+ cells has led to their identification as a cancer stem cell marker for some solid tumors including colorectal cancer (CRC) (Barker et al. 2009). This presents LGR5 as a potential target molecule for CAR-T cell directed specific tumor cell killing. For treatment of CRC with LGR5-directed CAR-T cells, it is critical to gain an understanding of the level of LGR5 expression on normal tissue compared with cancerous tissue. The aim of this study was to develop a screening technique for patient selection, and importantly identify potential responders to LGR5-targeting CAR-T cell therapy.Utilizing commercially purchased tissue microarrays a cohort of patient primary tumor biopsies (n=472) were assessed for LGR5 expression; ~60% displayed moderate to high level LGR5 positivity, with a trend toward higher grade, later stage tumors having higher levels of LGR5. LGR5 expression levels on lymph node metastases showed a positive correlation to LGR5 expression on patient-matched primary tumor tissue. Seven out of ten liver biopsies from metastatic colon cancer lesions showed a medium to high level LGR5 staining, indicating this may be used as a screening tool for metastatic CRC patients. We also observed restricted expression of LGR5 across the many normal tissues, suggesting limited off-target effects of LGR5-targeting CAR-T cells.The data obtained in this study provides evidence that LGR5 IHC of biopsies could be used as a diagnostic screening tool of CRC patients for inclusion into a Phase1a/2 clinical trial. Barker N, et al., 2007, Identification of stem cells in small intestine and colon by marker gene Lgr5. Nature 449: 1003–1007 Barker N. et al. 2009, Crypt stem cells as the cells-of-origin of intestinal cancer. Nature 457: 608–611Jaks V. et al. 2008, Lgr5 marks cycling, yet long-lived, hair follicle stem cells. Nat Genet. Nov;40(11):1291-9. Citation Format: Emma J. Thompson, Veronika Bandara, Batjargal Gundsambuu, Silvana Napoli, Stuart Mills, Jade Foeng, Dylan McPeake, Timona Tyllis, Caitlin Abbott, Allison Cowin, Timothy Sadlon, Shaun McColl, Carmela Ricciardelli, Simon C. Barry, Claudine S. Bonder. Assessing LGR5 expression levels on colorectal cancer tissue samples for use in LGR5-targeting CAR-T cell therapy clinical trial. [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 5545.