Oleanolic Acid Induces Autophagy and Apoptosis via the AMPK-mTOR Signaling Pathway in Colon Cancer.

Changxiao Hu,Shengliang Gu,Tian Li,Xiaorong Tang,Kai Xiong,Minhui Yang,Yibo Cao,Tianbao Xiao,Ping Li,Gagan Chhabra

doi:10.1155/2021/8281718

Abstract

Aims The purpose of this study was to explore the biological functions of the mTOR and AMPK signaling pathways in colon cancer (CC). The potential molecular mechanisms by which oleanolic acid (OA) induces autophagy and apoptosis were also investigated. Methods The biological functions of mTOR were analyzed by GeneCards, the Search Tool for the Retrieval of Interacting Genes (STRING), and the Database for Annotation, Visualization and Integrated Discovery (DAVID). Least absolute shrinkage and selection operator (LASSO) regression analysis was used to obtain prognostic and survival data of CC patients from the Gene Expression Omnibus (GEO) database. The effects of OA on the CC cell lines HCT-116 and SW-480 were analyzed by CCK-8, colony formation assay, and high-content system (HCS) array scan. The apoptosis rate of SW-480 and HCT-116 cells was detected by flow cytometry. The mRNA and protein expression levels in HCT-116 and SW-480 cells and NCM-460 normal colonic epithelial cells were detected by RT-PCR and Western blotting. Results mTOR was highly expressed in CC patients and acted as an oncogene. The AMPK signaling pathway mediated by mTOR predicted the poor prognosis of CC patients. OA effectively inhibited the proliferation and viability of CC cells. Furthermore, the apoptosis rate of CC cells was clearly increased following OA administration. Regarding the molecular mechanism of OA, the results indicated that mTOR and the antiapoptosis gene Bcl-2 were downregulated by OA. In addition, regulator genes of autophagy and apoptosis, including BAX, caspase-9, caspase-8, and caspase-3, were significantly upregulated by OA. Moreover, OA upregulated AMPK and its downstream proteins, including TSC2, BAX, Beclin 1, LC3B-II, and ULK1, to induce autophagy and apoptosis in CC cells. Conclusion The findings from this study demonstrate that OA could effectively inhibit the proliferation and viability of CC cells. The anti-CC activity of OA is closely related to the activation of the AMPK-mTOR signaling pathway. Activation of AMPK and inhibition of mTOR are involved in the induction of autophagy and apoptosis by OA. OA induced autophagy and apoptosis mainly in an AMPK activation-dependent manner in CC cells.

Highlights

Colon cancer (CC) is one of the most common malignant tumors and the third most common cancer, after lung and prostate cancer, in the world [1]
Increasing drug resistance and adverse effects related to radiotherapy and Journal of Oncology chemotherapy have severely degraded the quality of life of CC patients. erefore, novel treatment strategies and drugs are urgently required to meet the clinical needs of CC patients
Another study indicated that oleanolic acid (OA) and its analogs with apoptosis-inducing activity effectively inhibited the incidence of abnormal recess and multitree lesions in rats with colon cancer, indicating that

Summary

Introduction

Colon cancer (CC) is one of the most common malignant tumors and the third most common cancer, after lung and prostate cancer, in the world [1]. AMPK activation stimulated autophagy by increasing the protein expression levels of Beclin 1 and LC3-II and decreasing the levels of p-mTOR and p-ULK1 in CC cells [13]. AMPK can negatively regulate the mammalian target of mTOR, thereby inducing autophagy and apoptosis of CC in vivo and in vitro [13, 14]. Another study indicated that OA and its analogs with apoptosis-inducing activity effectively inhibited the incidence of abnormal recess and multitree lesions in rats with colon cancer, indicating that. Activation of AMPK and inhibition of mTOR were involved in autophagy and apoptosis induced by OA. E anticancer activities of OA are closely related to activation of the AMPK-mTOR signaling pathway, which is crucial in apoptosis and autophagy processes. OA induced apoptosis and autophagy predominantly via an AMPK activationdependent mechanism in CC cells

Materials and Methods

Results

Findings

Conflicts of Interest