Targeted Inhibition of Src Kinase Signaling Attenuates Pancreatic Tumorigenesis

Abstract

Elevated Src expression correlates with malignant potential and metastatic disease in many tumors including pancreas cancer. We sought to characterize the molecular effects of Src kinase inhibition with dasatinib (BMS-354825) a novel, multi-targeted kinase inhibitor that targets Src family kinases, in pancreas ductal adenocarcinoma (PDA). We identified sensitive and resistant PDA cell lines to dasatinib treatment and tested the molecular effects of Src inhibition in vitro and in vivo. We show for the first time that cellular localization of Src expression impacts survival in patients with PDA. Pancreas tumors with increased membranous expression of Src result in decreased survival compared with tumors that have increased cytoplasmic Src expression. Src kinase inhibition with dasatinib markedly inhibits cell proliferation, migration, invasion, cell cycle progression and anchorage independent growth and stimulates apoptosis. This is accompanied by decreased phosphorylation of Src, FAK, paxillin, AKT, STAT3, ERK, JNK and MAPK, as well as decreased cyclinD1 expression in a time and concentration-dependent manner. Furthermore, siRNA to Src results in significant decrease in cell proliferation, invasion and migration of pancreas cancer cells. Dasatinib treatment also inhibits in vivo pancreas tumor growth. Mechanisms of resistance to Src inhibition appear to be related to a lack of inhibition of STAT3 and MAPK signaling. These results establish a mechanistic rationale for Src inhibition with dasatinib as a therapeutic target in the treatment of pancreas cancer and identify potential biomarkers of resistance to Src inhibition.

A Preclinical Evaluation of SKLB261, a Multikinase Inhibitor of EGFR/Src/VEGFR2, as a Therapeutic Agent against Pancreatic Cancer

“…It has been well established that STAT3 activation regulates oncogenic signaling in many tumor types and leads to increased cell survival, proliferation, and tumor growth (43)(44)(45)(46). Furthermore, recent studies have also shown that activated STAT3 is a biomarker of resistance to Src inhibition with dasatinib treatment in resistant PANC-1 cells (32,36). Consistent with these reports, we found that dasatinib did not inhibit the STAT3 phosphorylation in PANC-1 cells in vitro.…”

“…Significantly, gemcitabine appeared to increase the phosphorylation of EGFR and ERK in both BxPC-3 and PANC-1 cells at a concentration of 10 mmol/L, which is consistent with a previous report (35). Of note, SKLB261 reduced the STAT3 phosphorylation in a concentration-dependent manner in both BxPC-3 cells and PANC-1 cells, which is reported to be one of the mechanisms of resistance to Src inhibition in pancreatic cancer cells (36).…”

Phase 2 placebo-controlled, double-blind trial of dasatinib added to gemcitabine for patients with locally-advanced pancreatic cancer

“…Dasatinib decreases cell proliferation, cell cycle progression, anchorage independent growth, migration, and invasion in PDAC cell lines in vitro [10,19] and significantly inhibited the development of metastases in vivo with no effect on overall survival, probably due to progression of the primary tumor. Thus, there is evidence to support the hypothesis that Src kinase inhibitors may function as anti-metastatic agents in PDAC [10].…”

“…Treatment of pancreatic cancer cell lines in vitro with dasatinib inhibits invasion and migration at concentrations that inhibit Src kinase activity [10,19], as well as proliferation and anchorage-independent cell growth [19,20]. Dasatinib inhibits pancreatic tumor growth in vivo in xenograft models [19,20] and inhibits the development of metastases in vivo in a genetically-engineered mouse model of pancreatic cancer [10], suggesting that this agent might best be used in patients without metastatic disease to prevent development of distant metastases. Unpublished data from the first author's laboratory suggests that there was a trend to improved overall survival with the combination of gemcitabine and dasatinib compared to dasatinib alone in a genetically-engineered mouse model of pancreatic cancer that did not reach statistical significance (p = 0.08).…”

Src Inhibition Is Still a Relevant Target in Pancreatic Cancer

“…There are significant preclinical data to support the rationale for Src inhibition as a potentially effective therapeutic target in PCa [3][4][5][6]. However, the presumption that a single biologic agent would significantly improve survival in metastatic PCa is inconsistent with prior clinical investigation and preclinical data.…”