Rhein sensitizes human colorectal cancer cells to EGFR inhibitors by inhibiting STAT3 pathway

Yan Zhuang; Ying Bai; Yan Hu; Yueqin Guo; Lingyuan Xu; Wanle Hu; Lehe Yang; Chengguang Zhao; Xiaokun Li; Haiyang Zhao

doi:10.2147/OTT.S206833

Rhein sensitizes human colorectal cancer cells to EGFR inhibitors by inhibiting STAT3 pathway

Onco Targets Ther. 2019 Jul 3:12:5281-5291. doi: 10.2147/OTT.S206833. eCollection 2019.

Authors

Yan Zhuang^#^{1

2}, Ying Bai^#^{1

2}, Yan Hu^#³, Yueqin Guo^{1

2}, Lingyuan Xu^{1

2}, Wanle Hu⁴, Lehe Yang^{1

2}, Chengguang Zhao^{1

2}, Xiaokun Li^{1

2}, Haiyang Zhao^{1

2}

Affiliations

¹ The Institute of Life Sciences, Wenzhou University, Wenzhou, Zhejiang 325035, People's Republic of China.
² School of Pharmaceutical Sciences, Wenzhou Medical University, Wenzhou, Zhejiang 325035, People's Republic of China.
³ Department of Pharmacy, Taizhou Enze Medical Center (Group), Taizhou Hospital of Zhejiang Province, Taizhou, Zhejiang 317000, People's Republic of China.
⁴ Department of Coloproctology, The Second Affiliated Hospital and Yuying Children's Hospital, Wenzhou Medical University, Wenzhou, Zhejiang 325000, People's Republic of China.

^# Contributed equally.

Abstract

Background: Activation of epidermal growth factor receptor (EGFR) has been reported in a variety of cancer types, including colorectal cancer (CRC), and represents a potential chemotherapeutic drug target. EGFR tyrosine kinase inhibitors (EGFR-TKIs) have been increasingly applied in the clinical treatment of CRC, but development of drug resistance during the treatment has greatly limited their application. Signal transducer and activator of transcription 3 (STAT3) and its mediated signal transduction pathway play an important role in the occurrence, development and metastasis of CRC, and are related to the development of EGFR-TKI resistance in CRC.

Methods: Cell viability, colony formation and cellular morphology were examined to evaluate the potent antiproliferative effect of the STAT3 inhibitor napabucasin, LY5 and rhein on the human CRC cell lines HCT116, SW620, RKO and DLD-1. Flow cytometry-based analysis was employed to determine whether rhein can affect the cell cycle and apoptosis. The expression level of phosphorylated STAT3 (P-STAT3), and cell cycle- and apoptosis-related proteins BCL2, CDC2 BAX, Cyclin D1 and Cyclin B1 were detected by Western blot analysis.

Results: This study revealed that rhein can significantly reduce cell viability and stimulate apoptosis in human CRC cells in a dose-dependent manner. In addition, rhein induced cell cycle arrest at the G2/M phase in CRC cells and dose-dependently inhibited the expression of cell cycle-related proteins. Additionally, it was found that napabucasin, LY5 and rhein considerably sensitized cells to the EGFR-TKI erlotinib, thus suppressing CRC cell proliferation. Rhein also inhibited the phosphorylation of its downstream target STAT3. Inhibition of STAT3 and EGFR phosphorylation was also observed after treatment with a combination of rhein and EGFR inhibitors.

Conclusion: This study confirmed the synergistic effect of STAT3 inhibitor and EGFR inhibitor in CRC cell lines. Additionally, we found that rhein sensitizes human CRC cells to EGFR-TKIs by inhibiting STAT3 pathway. When combined with EGFR-TKIs, rhein may be a novel STAT3 inhibitor in CRC.

Keywords: EGFR; STAT3; colorectal cancer; rhein; tyrosine kinase inhibitor.