Cucurbitacin B and SCH772984 exhibit synergistic anti-pancreatic cancer activities by suppressing EGFR, PI3K/Akt/mTOR, STAT3 and ERK signaling
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Jingkai Zhou1, Tiangang Zhao2, Linfeng Ma2, Min Liang2, Ying-Jie Guo2 and Li-Mei Zhao1
1Department of Pharmacy, Shengjing Hospital of China Medical University, Shenyang, China
2School of Life Sciences, Jilin University, Changchun, China
Ying-Jie Guo, email: [email protected]
Li-Mei Zhao, email: [email protected]
Keywords: cucurbitacin B, SCH772984, pancreatic cancer, EGFR, ERK
Received: June 29, 2017 Accepted: September 21, 2017 Published: October 09, 2017
Cucurbitacin B (CuB) is a natural tetracyclic triterpene product and displays antitumor activity across a wide array of cancers. In this study, we explored the anti-pancreatic cancer activity of CuB alone and in combination with SCH772984, an ERK inhibitor, in vitro and in vivo. CuB inhibited proliferation of pancreatic cancer cells by arresting them in the G2/M cell cycle phase. This was associated with inhibition of EGFR expression and activity and downstream signaling, including PI3K/Akt/mTOR and STAT3. Interestingly, ERK activity was markedly enhanced by activating AMPK signaling after 12 h of CuB treatment. SCH772984 potentiates the cytotoxic effect of CuB on pancreatic cancer cells through complementary inhibition of EGFR, PI3K/Akt/mTOR, STAT3 and ERK signaling, followed by an increase in the pro-apoptotic protein Bim and a decrease in the anti-apoptotic proteins Mcl-1, Bcl-2, Bcl-xl and survivin. Furthermore, combined therapy with CuB and SCH772984 resulted in highly significant growth inhibition of pancreatic cancer xenografts. These results may provide a basis for further development of combining CuB and ERK inhibitors to treat pancreatic cancer.
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