Combination Treatment With Inhibitors of ERK and Autophagy Enhances Antitumor Activity of Betulinic Acid in Non-small-Cell Lung Cancer In Vivo and In Vitro.

Chao-Yue Sun,Shi-Juan Mai,Di Cao,Bing Feng,Hui-Yun Wang,Shan-Shan Zhang,Qian-Nan Ren,Ning-Ning Zhou

doi:10.3389/fphar.2021.684243

Abstract

Aberrant activation of the Ras–ERK signaling pathway drives many important cancer phenotypes, and several inhibitors targeting such pathways are under investigation and/or approved by the FDA as single- or multi-agent therapy for patients with melanoma and non–small-cell lung cancer (NSCLC). Here, we show that betulinic acid (BA), a natural pentacyclic triterpenoid, inhibits cell proliferation, and induces apoptosis and protective autophagy in NSCLC cells. Thus, the cancer cell killing activity of BA is enhanced by autophagy inhibition. Mitogen-activated protein kinases, and especially ERK that facilitates cancer cell survival, are also activated by BA treatment. As such, in the presence of ERK inhibitors (ERKi), lung cancer cells are much more sensitive to BA. However, the dual treatment of BA and ERKi results in increased protective autophagy and AKT phosphorylation. Accordingly, inhibition of AKT has a highly synergistic anticancer effect with co-treatment of BA and ERKi. Notably, autophagy inhibition by hydroxychloroquine (HCQ) increases the response of lung cancer cells to BA in combination with ERKi. In vivo, the three-drug combination (BA, ERKi, and HCQ), resulted in superior therapeutic efficacy than single or dual treatments in the xenograft mouse model. Thus, our study provides a combined therapy strategy that is a highly effective treatment for patients with NSCLC.

Highlights

Lung cancer incidence continues to decline in some countries, it remains the leading cause of cancer-related death in the world (Melosky et al, 2018; Siegel et al, 2018; Siegel et al, 2020), in which approximately 84% of lung cancers are non–small-cell lung cancer (NSCLC), and 70% of newly diagnosed NSCLC is in an advanced or metastatic stage (Kelly et al, 2018; Reinmuth, 2018)
betulinic acid (BA) inhibited the proliferation of NSCLC cells, which is concordant with the reported results (Kutkowska et al, 2017)
These results indicate that BA-induced apoptosis mediates inhibition of proliferation in NSCLC cells

Summary

Introduction

Lung cancer incidence continues to decline in some countries, it remains the leading cause of cancer-related death in the world (Melosky et al, 2018; Siegel et al, 2018; Siegel et al, 2020), in which approximately 84% of lung cancers are non–small-cell lung cancer (NSCLC), and 70% of newly diagnosed NSCLC is in an advanced or metastatic stage (Kelly et al, 2018; Reinmuth, 2018). There are many therapeutic options for NSCLC patients, the 5-year survival rate of NSCLC remains less than 15% in China (Macdonagh et al, 2018). Exploring effective strategies especially multiple drug combinations is a challenge for clinical management and improving survival in NSCLC patients. Autophagy has emerged as a pro-survival mechanism in response to adverse environmental conditions or therapeutic challenges (Das et al, 2018), indicating that autophagy can confer drug resistance. Inhibition of autophagy has the potential to kill cancer cells or improve anticancer therapeutics. Autophagy can induce cell death, termed autophagic cell death, and such autophagy inducers have potential to kill cancer cells (Fulda and Kogel, 2015). Pharmacological manipulation of autophagy, based on the differential cell fate, has the potential to enhance cancer therapy

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Conclusion