Abstract C018: Spatial profiling of tumor associated cells expressing endoplasmic reticulum stress proteins predicts poor outcomes in pancreatic cancer patients
Authors: Porter Georgia M. , Norris Murray , Apte Minoti , Merlot Angelica 
Published: January 2024

Abstract
The crosstalk between pancreatic cancer (PC) cells and cells of the tumor microenvironment (TME), such as immune cells and cancer associated fibroblasts (CAFs), has important implications for tumor progression. It is evident that the expression of endoplasmic reticulum (ER) stress proteins (e.g., BiP or CHOP) in tumor cells has survival implications for patients. For example, high BiP expression in tumor cells is correlated with poor survival in PC patients. However, the effect of these proteins in TME cells is currently unknown. We have employed quantitative multiplex immunofluorescence on a tumor microarray cohort of 259 treatment naive pancreatic cancer patient samples and 41 normal pancreas samples. We investigated the impact of expression of ER stress proteins BiP or CHOP in CAFS (α-SMA+), immune cells (CD45+), endothelial cells (CD31+) and tumor cells (PanCK+). HALO AI (Indica Labs) was used to conduct cell/tissue classifications and spatial proximity analysis. Notably, the proportion of CAFs and endothelial cells expressing BiP or CHOP was significantly (p&lt;0.01-0.0001) increased in tumor sections compared to non-tumor sections. When considering the tumor sections, increased BiP expression in CAFs and endothelial cells was found to be correlated with vascular invasion (p=0.0388 and p=0.0318 respectively). Interestingly, there was also a positive correlation between the percent of total CAFs and the percent of BiP positive cells (p=0.0037, r=0.293) or CHOP positive cells (p=0.0001, r=0.235), suggesting that ER stress could be associated with activation of CAFs. Spatial analysis was next utilized to explore the distribution of cells expressing BiP or CHOP within the TME. Remarkably, when examining the average distance in a 500 μm radius, our findings showed that immune cells expressing BiP or CHOP were located significantly (p&lt;0.0001) closer to tumor cells compared to non-expressing immune cells. Interestingly, increased distance of CHOP expressing immune cells to tumor cells was negatively correlated (p=0.037, r=-0.137) with tumor size. We next examined these cells within a 20 μm radius of tumor cells, as it represents a physiologically feasible distance for direct cell-cell contact. Increased numbers of CHOP CD45 cells within the 20 μm radius was correlated with poorer overall survival (p=0.0062) and event free survival (p=0.046). Similarly, in CAFS, BiP expressing cells were found on average closer to tumor cells (p&lt;0.0001), although this was not associated with patient survival. The observed correlation between elevated ER stress in TME cells with adverse patient outcomes indicates the importance of BiP or CHOP as potential therapeutic targets. Furthermore, the spatial analysis results provide insights into the organization of TME cells, shedding light on the significance of ER stress in the TME. These findings contribute to our understanding of the complex interplay between ER stress, tumor biology, and patient outcomes in PC.
Citation Format: Georgia M. Porter, Murray Norris, Minoti Apte, Angelica Merlot. Spatial profiling of tumor associated cells expressing endoplasmic reticulum stress proteins predicts poor outcomes in pancreatic cancer patients [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Pancreatic Cancer; 2023 Sep 27-30; Boston, Massachusetts. Philadelphia (PA): AACR; Cancer Res 2024;84(2 Suppl):Abstract nr C018.