Abstract 6880: Immune infiltration in inflammatory and myofibroblastic cancer-associated fibroblast high microenvironments of colorectal cancer
Authors: Gadalla Yousef , Johnson Katherine A. , Nath Sharanya , Pasch Cheri A. , Deming Dustin A. 
Published: March 2024

Background: Cancer-associated fibroblasts are major modulators of the tumor microenvironment (TME) and play a large role in the immune system’s response to tumors. The direct effect that myofibroblastic CAFs (myCAFs) and inflammatory CAFs (iCAFs) have on immune infiltration is not well studied in colorectal cancer (CRC). Here we investigate the effects that myCAFs and iCAFs have on immune infiltration in human CRCs.

Methods: The Cancer Genome Atlas (TCGA) Colorectal Adenocarcinoma PanCancer Atlas dataset was accessed via cBioPortal. Cancers were separated into myCAF prominent (MP) by high gene expression (Z-score &gt; 1) of ACTA2 and TAGLN and iCAF prominent (IP) by expression of PDPN and ICAM1. Gene Set Enrichment Analysis (GSEA) was performed on differential expression results comparing these groups. Additionally, bulk RNA sequencing results were analyzed for immune cell subsets using Cibersortx. Statistical analysis was completed in R.

Results: Of 592 cancer samples, 24 were MP and 9 IP. There was no significant difference in age (MP median age 63, IP median age 70, q = 0.6) nor sex (MP 17 female/7 male; IP 4 female/5 male, q=0.9). MP have 1/24 profiled patients with MSIsensor score &gt;=3.5 and 2/24 patients with MSI MANTIS score &gt; 0.4; IP have 3/9 profiled patients with MSIsensor score &gt;=3.5 and 3/9 patients with MSI MANTIS score &gt;0.4. IP cancers were enriched for gene sets associated with enhanced immune cell infiltration (Inflammatory Response, Interferon Gamma Response, Allograft rejection, TNFA signaling via NFKB, IL6 JAK STAT3 signaling, Interferon Alpha Response, Complement, IL2 STAT5 signaling and Apoptosis, all q&lt; 0.001). MP cancers were enriched in the KRAS signaling Down gene set (q=.009). IP cancers had a higher proportion of infiltrating immune cells than MP cancers by CibersortX analysis (iCAF median = 2.829, myCAF median= 2.284, p &lt; 0.01). IP cancers had higher CD4 memory cells (p &lt;0.001, iCAF median = 0.455, myCAF mean = 0.318), NK resting cells (p&lt;0.001, 0.228, 0.103), M1-like macrophages (p &lt;0.01, 0.1977,0.107), and neutrophils (p&lt;0.01, 0.0298, 0). MP cancers had a higher number of NK activated cells (p = 0.04, iCAF median = 0, myCAF median = 0). M1-like macrophage gene markers were higher expressed in IP cancers compared to MP cancers, though not significantly (NOS2 log2FC = 0.66, q = 0.652; IL1A 3.25, 0.0375; IL23A 1.34, 0.151; IL26 1.31, 0.32). Additionally, IP cancers tended to express markers for activated CD8+ T cells, though only IFNG was significant (GZMB, log2FC = 0.97, q = 0.337; IFNG, 2.16, q&lt;0.001; PRF1, 1.12, q=0.198).

Conclusion: These analyses indicate that iCAFs play the major role in modulating the immune infiltration of cancers. These data highlight the need for further research into the mechanisms by which different CAF subtypes alter the immune microenvironment.

Citation Format: Yousef Gadalla, Katherine A. Johnson, Sharanya Nath, Cheri A. Pasch, Dustin A. Deming. Immune infiltration in inflammatory and myofibroblastic cancer-associated fibroblast high microenvironments of colorectal cancer [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 6880.