Abstract 71: Differential infiltration of key immune cell populations across malignancies varying by immunogenic potential and likelihood of response to immunotherapy

Abstract Background: Emerging literature has identified key immune cell populations that appear to significantly impact immune activation or suppression in patients with cancer. We investigated candidate populations and their differential infiltration within tumors as estimated from mRNA co-expression levels of corresponding cellular markers. Methods: We utilized clinical and transcriptomic data from patients with melanoma, urothelial, ovarian, and pancreatic carcinomas enrolled in the Total Cancer Care Protocol (NCT03977402) to which patients provided a written informed consent. We analyzed mRNA co-expression levels of biomarkers defining stem-like tumor-infiltrating lymphocytes (TILs) (TCF7, IL7R, CXCR5, CD28, and CD27), tissue-resident memory (TRM) T cells (CD69 and CD103), early dysfunctional T cells (PD1+, CCR5+, TCF7+, TIM3-), late dysfunctional T cells (PD1+, CD38+, CD39+, CD101+, TIM3+), activated-potentially anti-tumor (APA) T cells (PD1+, CD27+, CD28+, CD137+, GITR+), and Butyrophilin 3 A (BTN3A) isoforms (BTN3A1, BTN3A2, BTN3A3). Mann-Whitney U or Kruskal-Wallis H tests were used to compare median gene expression signature scores between immunotherapy (IO) responders (2 years survival) and non-responders (2 years survival). Cox regression was used to assess 2-year survival outcomes following immunotherapy. Results: We found a significant difference in the estimated infiltration of APA T-cells in melanoma (P = 4. 67 Χ10−12 and P = 5. 80 Χ10−12) and in urothelial carcinoma (P = 1. 86 Χ10−09 and P = 1. 38 Χ10−09) as compared to ovarian and pancreatic tumors, respectively. There was less TRM T-cell infiltration in ovarian compared to melanoma (P = 2. 23 Χ10−8), urothelial (P = 3. 86 Χ10−28) and pancreatic (P = 7. 85 Χ10−9). A similar trend was seen with stem-like T-cells, early dysfunctional T cells, and late dysfunctional T cells. Differences in the expression of BTN3A isoforms were less apparent between the different tumors, with a trend towards higher expression in melanoma. In melanoma, a higher density of stem-like TIL, TRM, early dysfunctional T cells, late dysfunctional T cells, activated-potentially anti-tumor T cells, and BTN3A isoforms were associated with improved survival (P = 0. 0075, 0. 00059, 0. 013, 0. 005, 0. 0016 and 0. 041, respectively). A higher density of stem-like TIL was associated with improved survival in the urothelial cohort (P = 0. 028). TRM gene signature had the best AUCROC as a moderate predictor of survival in our melanoma cohort (AUROC = 0. 65) ; Examining the 6 signatures in public datasets of IO treated melanoma patients, they were similarly predictive of survival (AUROC of 0. 61 - 0. 64). Conclusions: Our results support a higher infiltration of key cellular elements related to immune activation within immunogenic versus non-immunogenic tumors supporting a central role in anti-tumor immune response. Citation Format: Ahmad A. Tarhini, Islam Eljilany, Sam Coleman, Dale J. Hedges, Martin McCarter, John Carpten, Howard Colman, Abdul Rafeh Naqash, Igor Puzanov, Susanne Arnold, Michelle Churchman, Patrick Hwu, William S. Dalton, George J. Weiner, Aik Choon Tan, Jose R. Conejo-Garcia, Paulo C. Rodriguez. Differential infiltration of key immune cell populations across malignancies varying by immunogenic potential and likelihood of response to immunotherapy 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 (6Suppl): Abstract nr 71.