Characterization of TIM3 and its ligands in colorectal cancer.

Abstract

3547 Background: TIM-3 is an inhibitory checkpoint glycoprotein found on innate and adaptive immune cells and is highly expressed on tumor infiltrating lymphocytes. TIM-3 and its ligands, Galectin 9 (Gal9), HMGB1 and CEACAM1 play a critical role in immune regulation and preclinical data suggest a role in the pathogenesis of colorectal cancer (CRC). We aimed to characterize the molecular features and prognostic value of TIM3 and its ligands in CRC. Methods: Tumor molecular profiling was performed from 15,026 FFPE samples by NextGen Sequencing on DNA (592 genes or WES) and RNA (WTS) and immunohistochemistry (IHC) at Caris Life Sciences (Phoenix, AZ). Top quartile transcripts per million (TPMs) for TIM-3, Gal9, HMGB1 and CEACAM1 were considered high (Q4) while bottom quartile low (Q1) expression (exp). X2/Fisher-exact tests were used for comparison and significance was determined as P-value adjusted for multiple comparison and this was found for the results reported here ( Q < 0.05). Cell infiltration in the tumor microenvironment (TME) was estimated by quanTIseq. Real-world overall survival (OS) information was obtained from insurance claims data and Kaplan-Meier estimates were calculated for molecularly defined pts. Results: Gal 9/TIM3-high tumors had higher prevalence (prev) of high tumor mutational burden (TMB ≥ 10 Mut/Mb) (12% vs. 8%; 14% vs. 6%), deficiency in mismatch repair (dMMR) (9% vs. 5%; 10% vs. 4%), PD-L1 exp (5% vs. 3%; 7% vs. 2%), and was highest in transverse (Fold Change; FC: 1.05, 1.12) and right sided tumors (1.04, 1.10) compared to left sided tumors, and CMS4. In contrast, HMGB1 and CEACAM1-high tumors had lower prev of dMMR (5% vs. 8%, 3% vs. 12%), PD-L1 exp (3% vs. 5%, 3% vs. 6%) and TMB-H (8% vs. 11%, 6% vs. 16%), and was highest in CMS2. In MSS tumors, Gal9/TIM3-high tumors were associated (assoc) with lower frequency of TP53, amplifications (amp) of FLT1/3, CDX2, FOXO1, and CDK8 while CEACAM1 and HMGB1-high were assoc with higher mutation (mut) rates of TP53, APC, NRAS, amp of FLT1/3, CDX2, CDX8, and lower mut in GNAS, FBXW7 and RNF43. High Gal9 and TIM3 exp was assoc with higher infiltration of B cells, M1 and M2 macrophages, NK cells, CD4+ and C8+ T cells, and Tregs, while high HMGB1 and CEACAM1 exp was negatively assoc with Tregs, M1 macrophages, monocytes and CD8+ T cells. High exp of Gal9, TIM3, HMGB1, and CEACAM1 was assoc with worse OS in the entire cohort (HR 0.90, 95%CI, 0.84-0.97, P = 0.005, HR 0.81, 95% CI, 0.75-0.87, P< 0.00001; HR 0.88, 95% CI, 0.82-0.95, P < 0.001; HR 0.80; 95%CI, 0.74-0.86, P < 0.00003, respectively). Conclusions: Strong assoc were identified between Gal9/TIM3, HMGB1 and CEACAM1 gene exp and IO biomarkers, distinct molecular features, CMS, TME cell infiltration, and patient outcomes in CRC. Significantly different mut frequencies may signify unique subsets of CRC. These findings provide rationale for further evaluation of TIM3 and its ligands in CRC as prognostic biomarkers and potential therapeutic targets modifying the TME.