Metformin combined with aspirin significantly inhibit pancreatic cancer cell growth in vitro and in vivo by suppressing anti-apoptotic proteins Mcl-1 and Bcl-2.

Wen Yue,Yong Lin,Chung S Yang,Xiang-Lin Tan,Xi Zheng,Robert S Dipaola,Huarong Huang,Qing Xu,Darren Carpizo

doi:10.18632/oncotarget.4126

Abstract

Metformin and aspirin have been studied extensively as cancer preventive or therapeutic agents. However, the effects of their combination on pancreatic cancer cells have not been investigated. Herein, we evaluated the effects of metformin and aspirin, alone or in combination, on cell viability, migration, and apoptosis as well as the molecular changes in mTOR, STAT3 and apoptotic signaling pathways in PANC-1 and BxPC3 cells. Metformin and aspirin, at relatively low concentrations, demonstrated synergistically inhibitory effects on cell viability. Compared to the untreated control or individual drug, the combination of metformin and aspirin significantly inhibited cell migration and colony formation of both PANC-1 and BxPC-3 cells. Metformin combined with aspirin significantly inhibited the phosphorylation of mTOR and STAT3, and induced apoptosis as measured by caspase-3 and PARP cleavage. Remarkably, metformin combined with aspirin significantly downregulated the anti-apoptotic proteins Mcl-1 and Bcl-2, and upregulated the pro-apoptotic proteins Bim and Puma, as well as interrupted their interactions. The downregulation of Mcl-1 and Bcl-2 was independent of AMPK or STAT3 pathway but partially through mTOR signaling and proteasome degradation. In a PANC-1 xenograft mouse model, we demonstrated that the combination of metformin and aspirin significantly inhibited tumor growth and downregulated the protein expression of Mcl-1 and Bcl-2 in tumors. Taken together, the combination of metformin and aspirin significantly inhibited pancreatic cancer cell growth in vitro and in vivo by regulating the pro- and anti-apoptotic Bcl-2 family members, supporting the continued investigation of this two drug combination as chemopreventive or chemotherapeutic agents for pancreatic cancer.

Highlights

Metformin and aspirin, two emerging candidate drugs of cancer chemoprevention, have been reported to decrease the risk of different types of cancers, including pancreatic cancer [1,2,3,4,5,6]
In a PANC-1 xenograft mouse model, we demonstrated that the combination of metformin and aspirin significantly inhibited tumor growth and downregulated the protein expression of Mcl-1 and Bcl-2 in tumors
Our results showed that metformin combined with aspirin could significantly downregulate anti-apoptotic proteins Mcl-1 and Bcl-2 and upregulate pro-apoptotic proteins Bim and Puma

Summary

Introduction

Two emerging candidate drugs of cancer chemoprevention, have been reported to decrease the risk of different types of cancers, including pancreatic cancer [1,2,3,4,5,6]. In a pooled analysis of 25,570 patients in eight trials, Rothwell et al recently reported that daily aspirin use reduced deaths due to several common cancers, including significant reductions in colorectal and pancreatic cancer deaths, with most benefit seen after 5 years of the scheduled trial treatment [7]. These investigations suggest that both metformin and aspirin have preventive effects against the development of pancreatic cancer. A derivative of aspirin, nitric oxide–donating aspirin (NO-ASA), showed chemopreventive effect in pancreatic cancer cell lines [18] and transgenic mice models [19]

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Conclusion