Abstract 942: CXCR2 acts as a checkpoint regulator of the pancreatic stellate cells activity within pancreatic cancer tumor microenvironment
Authors: Awaji Mohammad , Varney Michelle , Purohit Abhilasha , Batra Surinder K. , Singh Rakesh K. 
Published: July 2017

Pancreatic cancer (PC) is a grotesque disease featured by an inflamed complex tumor microenvironment (TME) that contribute to advancing tumor progressing. Oncogenic K-ras, the most common mutation in PC, amplifies inflammation within TME through overexpression of multiple immune factors such as CXCR2 and its ligands. K-ras induced overexpression of CXCR2 axis, made CXCR2 seem intuitively a good target for PC treatment. In KC, a spontaneous PC mouse model with oncogenic K-ras, genetic ablation of CXCR2 caused anti-tumor events such as increased apoptosis and decreased angiogenesis; and also presented pro-tumorigenic events; most notably was the increased fibrosis and metastasis to the liver. These observations have shed light on the possible role the CXCR2 on the other TME component especially pancreatic stellate cells (PSCs). The aim of this study is to determine the differential effect of K-ras status and CXCR2 chemokines expression in the PC cells on their interaction with PSCs. Unidirectional segregated co-culture studies were conducted using conditioned media (CM). CM collected from PSCs were used to grow multiple PC cell lines, and CM obtained from different PC cell lines were used to culture PSCs. Cellular proliferation and gene expression were analyzed. Furthermore, PSCs proliferation potentials were assessed as those cells treated with exogenous CXCL1 and CXCL8, or PC cell lines derived-CM in the presence or absence of CXCR2 antagonists. Co-culture studies revealed that PSC-derived CM had increased proliferation of PC cell lines positive to oncogenic K-ras as well as increasing their expression of multiple chemokines such as CXCL1, CXCL5, and CCL2. On the other hand, PC cell lines with a wildtype K-ras were inhibited by PSC-derived CM treatment. PSCs proliferation potentials were decreased with CM derived from oncogenic K-ras positive PC cell lines and increased with CM derived from PC cell lines with wildtype K-ras. Furthermore, CM from oncogenic K-ras PC cell lines has increased the expression of multiple pro-tumorigenic genes in the PSCs including cytokines such as IL-10, IL-4 and IL-13, and chemokines such as CXCL2 and CXCL7. Also, treating PSCs with exogenous CXCL1 and CXCL8 exhibited a similar proliferation inhibition to that observed with oncogenic K-ras PC derived CM treatment. CXCR2 antagonists have shown rescued inhibition or enhanced proliferation of PSCs when incorporated with CXCR2 chemokine or PC cell line derived CM treatment. These observations suggest that K-ras status of PC dictates their interaction with PSCs within the TME. We have demonstrated that oncogenic K-ras through increased production of CXCR2 chemokine would dampen PSCs proliferation and further orient them to support tumor progression by increased expression of pro-tumorigenic genes. Besides, we observed that CXCR2 inhibition in PSCs would increase their proliferation which may further their fibrogenic activity.

Citation Format: Mohammad Awaji, Michelle Varney, Abhilasha Purohit, Surinder K. Batra, Rakesh K. Singh. CXCR2 acts as a checkpoint regulator of the pancreatic stellate cells activity within pancreatic cancer tumor microenvironment [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 942. doi:10.1158/1538-7445.AM2017-942