Abstract 4229: Differential impact of rice bran based dietary interventions during inflammation-associated colorectal cancer on distinct immune infiltrates and their spatial distribution signature
Authors: Kumar Robin , Maurya Akhilendra K. , Bugata Lakshmi S. , Kabir Md. I. , Tomar Munendra , Agarwal Rajesh , Ryan Elizabeth P. , Raina Komal 
Published: April 2023

Abstract
Modulating the immune cell infiltrates in the colonic tissue via dietary intervention or modulation of the gut microbiota and its crosstalk with the components of the diet is now recognized as an effective strategy to protect against inflammation-associated colorectal cancer (CRC). In this regard, we recently reported, both gut microbiota-dependent and independent mechanisms for dietary rice bran (RB) meditated protective efficacy against inflammation-associated azoxymethane/dextran sodium sulfate (AOM/DSS)-induced CRC. We also reported that ex vivo fermentation of RB with beneficial microbe ‘Bifidobacterium longum’ did not exhibit similar protective benefits as RB in damaged colonic tissues in the absence of gut microbiota [germ-free (gf) mice]. The role of rice bran (RB) constituents as prebiotics and in preserving gut barrier and a healthy gut microbiota led to in-depth investigation into the protective efficacy of RB against CRC. Accordingly, in the present study, we performed multiplex imaging (9 color panel) to assess immune sub-typing and spatial phenotypic signature of the colonic tissue/tumor microenvironment in the AOM/DSSgf mice [following RB and fermented RB (FRB) dietary intervention]. Briefly, we determined the presence of T cells [CD3+], cytotoxic T cells [CD3+ CD8+], helper T cells [CD3+ CD8−], regulatory T (Treg) cells [CD3+CD8−FoxP3+), natural killer (NK) cells [CD49b+], NKT cells [CD3+CD49b+], macrophage (MΦ) [F4/80 +], M1 [F4/80+iNOS+CD206−] and M2 [F4/80+CD206+] subtypes and B cells [B220+]. Results indicated an overall high infiltration of immune cells in female AOM/DSSgf mice on control diet compared to males, which was positively correlated with severe pathological changes observed in the female colon tissues. Notably, RB and FRB diets showed a differential impact on the sub-type of immune cells and their spatial localization. Protective efficacy of RB was associated with decrease in infiltration of T cells (including their subtypes). Interestingly, while cytotoxic T cells were lower in FRB (AOM/DSSgf) female mice, there was a significant increase in pro-inflammatory M1 MΦ sub-types in colon tissue of mice marred by epithelial erosion which compromised FRB potential. Spatial distance analysis also indicated that immune cells were distantly spaced in RB intervention groups compared to FRB and AOM/DSSgf controls. Though, M2 MΦ were relatively higher in number in AOM/DSSgf controls, their presence did not have influence on protective efficacy or lack thereof. In general, it was inferenced that the protective efficacy of the RB diets in the absence of gut microbiota was positively correlated with modulation of T cell infiltration while inflammation-associated CRC and epithelial erosion in FRB diet groups were associated with skewed MΦ sub-types-with increased presence of M1MΦ.
Citation Format: Robin Kumar, Akhilendra K. Maurya, Lakshmi S. Bugata, Md. I. Kabir, Munendra Tomar, Rajesh Agarwal, Elizabeth P. Ryan, Komal Raina. Differential impact of rice bran based dietary interventions during inflammation-associated colorectal cancer on distinct immune infiltrates and their spatial distribution signature. [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 4229.