Abstract 4271: The ITGA2 (CD49b) collagen receptor excludes the CD8+ T cell infiltration in pancreatic ductal adenocarcinoma
Authors: Eissa Ibrahim Ragab , Abston Eric D. , Kuruppu Darshini , Wang Yongtao , Qiao Guoliang , Qadan Motaz , Lanuti Michael , Tanabe Kenneth K. 
Published: March 2024

Abstract
BACKGROUND: Pancreatic ductal adenocarcinoma cancer (PDAC) is characterized by an enriched extracellular matrix and limited T cell infiltration, which poses challenges for immunotherapy. The significant accumulation of collagen type I (COL1) in PDAC tumor microenvironment raises questions about its functional role in PDAC progression and its interactions with the cellular compartments. OBJECTIVE: The objective of this study was to investigate whether the collagen receptors expressed by cancer cells modulate the anti-tumor activity of CD8+ tumor-infiltrated lymphocytes (CD8+ TILs).METHODS: Collagen receptor expression patterns in PDAC were examined using flow cytometry, western blot, multiplex immunofluorescence, RNA seq, and scRNA seq databases in KPC and treatment-naïve PDAC that were resected from patients. The KPC cell line, known as Hy15549, was established from KPC mouse model (Ptf1-Cre; LSL-KRAS-G12D; Trp53 Lox/+). Using CRISPR-Cas9, we conducted targeted deletions for either ITGA2(CD49b) or ITGB1(CD29), as well as generating double knockouts for both CD49b and CD29. Growth of these cell lines implanted into the flanks of immunocompetent, immunodeficient mice was measured, as well as after CD8+ T cell depletion in immunocompetent mice. We analyzed TILs using FACs. We used multiplex immunofluorescence to analyze tumors microenvironment including collagen fiber alignment. Downstream signaling pathways were assessed using RNA seq and western blot. RESULTS: CD49b is highly expressed specifically in PDAC cancer cells, as assessed in both KPC cell flank tumors and resected human PDAC. Using adhesion assay, we found that CD49b specifically binds to Col1 rather than ColIV. KPC CD29b KO exhibited a complete loss of adhesion to both Col1 and ColIV. Tumor growth of the KPC CD49b KO, KPC CD29 KO, KPC CD49b CD29 KO was observed to be significantly slower than KPC WT despite identical in vitro growth kinetics. Knockout of CD49b in tumors promoted intratumoral infiltration of CD8+ T cells and significantly impeded tumor growth. Tumor growth by KPCCD49bKO was rescued by depletion of CD8+ T cells. In contrast to observations in immune-competent mice, KPCCD49bKO tumor growth was similar to KPCwt in immunodeficient nude mice. Analysis of downstream signaling in KPCCD49bKO tumors revealed a decrease of FAK as well as pFAk expression pathway. The proteomic profiling of KPCCD49bKO revealed an increase of CXCL10 chemokine. Moreover, In the absence of CD49b, the orientation of collagen fiber alignment appeared more scattered, with thinner fibers. This altered alignment could potentially contribute to immune cell infiltration.Conclusion:These findings reveal a previously unreported function of CD49b in PDAC cancer progression and the immune response within the TME. Together, our study reveals a mechanism underlying immune exclusion and suggests a novel immunotherapeutic target in PDAC.
Citation Format: Ibrahim Ragab Eissa, Eric D. Abston, Darshini Kuruppu, Yongtao Wang, Guoliang Qiao, Motaz Qadan, Michael Lanuti, Kenneth K. Tanabe. The ITGA2 (CD49b) collagen receptor excludes the CD8+ T cell infiltration in pancreatic ductal 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 4271.