Abstract 3178: Targeting CXCR2 signaling inhibits KRAS(G12D) induced autocrine growth transformation by suppressing ERK activation in pancreatic cancer

Abstract

Pancreatic ductal adenocarcinoma (PDAC) is a disease with poor survival. Somatic KRAS mutations are present in almost 95% of PDAC patients and are known to a play pivotal role in PDAC genesis and progression. The G12D substitution is the predominant form detected in PDAC. By constitutively activating diverse downstream signaling pathways (like ERK/MEK) KRAS mutations are known to drive autocrine growth transformation in cancer cells. However, the lack of therapeutics for direct targeting of mutant KRAS necessitate a proper understanding of its downstream mechanisms, which may aid in the development of specific therapeutics. CXCR2 is a receptor for the ELR-positive CXC subfamily of chemokines, which are established regulators of leukocyte chemotaxis during inflammation. Aberrant expression of CXCR2 and its ligands has been reported in various cancers including PDAC. Both autocrine and paracrine events mediated by CXCR2 signaling lead to the manifestation of tumor growth, metastasis and angiogenesis. RAS is a known regulator of cytokine production including CXC chemokines. Whilst much of the work done formerly has indicated a paracrine role for KRAS-induced production of CXC chemokines in the biology of PDAC the precise autocrine effects of KRAS induced CXCR2 signaling remain uncertain. We examined the tumors derived from PDX-cre-LSL-kras(G12D) mice and observed a specific expression of Cxcr2 in the cytokeratin positive duct cells. Based on this preliminary observation the objective of our current study is to evaluate the autocrine role of CXCR2 signaling in the KRAS(G12D) -induced PDAC development. Two human cell line models having exogenously expressed KRAS(G12D): hTERT-HPNE-/KRAS(G12D) and hTERT-HPNE-E6-E7-st/KRAS(G12D) were used for our in vitro studies. CXCR2 inhibition achieved using antagonists (SCH-527123 and SCH-479833) significantly (P ≤ 0.05) suppressed the in vitro proliferation, anchorage independent growth and migration potential of KRAS(G12D) bearing cells in a dose dependent manner. We generated stable clones of hTERT-HPNE-E6-E7-st/KRAS(G12D) cells having knock-down for CXCR2. Complementing our observations from CXCR2 inhibition the hTERT-HPNE-E6-E7-st/KRAS(G12D)-shCXCR2 cells demonstrated a significant (P ≤ 0.05) decrease in in vitro cell growth, colony formation and migration compared to the control cells. Additionally, both hTERT-HPNE-E6-E7-st/KRAS(G12D)-shCXCR2 cells and hTERT-HPNE-E6-E7-st/KRAS(G12D) cells treated with SCH-527123 demonstrated inhibited phosphorylation of Erk downstream of KRAS. We next extended our investigation in vivo. The hTERT-HPNE-E6-E7-st/KRAS(G12D)-shCXCR2 cells showed reduced tumor growth compared to the control cells in subcutaneous implants. To conclude, our data provides evidence for the role of the CXCR2 signaling axis in regulation of KRAS(G12D) induced autocrine cellular transformation in PDAC. Citation Format: Abhilasha Purohit, Michelle Varney, Satya Rachagani, Pavan Myneni, Michel Ouellette, Surinder K. Batra, Rakesh K. Singh. Targeting CXCR2 signaling inhibits KRAS(G12D) induced autocrine growth transformation by suppressing ERK activation in pancreatic cancer. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 3178. doi:10.1158/1538-7445.AM2015-3178