Thalidezine, a novel AMPK activator, eliminates apoptosis-resistant cancer cells through energy-mediated autophagic cell death.

Betty Yuen Kwan Law,Jing Rong Wang,Paolo Saul Coghi,An Guo Wu,Wai Kit Chan,Yuan Qing Qu,Wei Zhang,Jianru Guo,Liang Liu,Simon Wing Fai Mok,Xiao Jun Yao,Ni Zhang,Flora Gordillo-Martínez,Su Wei Xu,Xing Xing Fan,Elaine Lai Han Leung,Vincent Kam Wai Wong

doi:10.18632/oncotarget.15616

Betty Yuen Kwan Law, Jing Rong Wang + Show 15 more

Open Access

https://doi.org/10.18632/oncotarget.15616

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Journal: Oncotarget	Publication Date: Feb 22, 2017
Citations: 32	License type: cc-by

Affiliation: Macau University of Science and Technology

Abstract

Cancers illustrating resistance towards apoptosis is one of the main factors causing clinical failure of conventional chemotherapy. Innovative therapeutic methods which can overcome the non-apoptotic phenotype are needed. The AMP-activated protein kinase (AMPK) is the central regulator of cellular energy homeostasis, metabolism, and autophagy. Our previous study showed that the identified natural AMPK activator is able to overcome apoptosis-resistant cancer via autophagic cell death. Therefore, AMPK is an ideal pharmaceutical target for chemoresistant cancers. Here, we unravelled that the bisbenzylisoquinoline alkaloid thalidezine is a novel direct AMPK activator by using biolayer interferometry analysis and AMPK kinase assays. The quantification of autophagic EGFP-LC3 puncta demonstrated that thalidezine increased autophagic flux in HeLa cancer cells. In addition, metabolic stress assay confirmed that thalidezine altered the energy status of our cellular model. Remarkably, thalidezine-induced autophagic cell death in HeLa or apoptosis-resistant DLD-1 BAX-BAK DKO cancer cells was abolished by addition of autophagy inhibitor (3-MA) and AMPK inhibitor (compound C). The mechanistic role of autophagic cell death in resistant cancer cells was further supported through the genetic removal of autophagic gene7 (Atg7). Overall, thalidezine is a novel AMPK activator which has great potential to be further developed into a safe and effective intervention for apoptosis- or multidrug-resistant cancers.

Highlights

The AMP-activated protein kinase (AMPK), a serine/threonine kinase, is a heterotrimeric complex containing one catalytic α subunit and regulatory β and γ subunits
AMPK directly phosphorylates a number of downstream targets including ACC, ULK, and Mammalian target of rapamycin complex 1 (mTORC1), which act as mediator/effectors to metabolism, cell growth, and autophagy [1, 4,5,6]
Immunoblot results indicated an increase in AMPK phosphorylation accompanied by a reduction in phosphorylated p70S6K, a downstream target of mTOR, in response to thalidezine after eight hours of treatment (Figure 1D)

Summary

Introduction

The AMP-activated protein kinase (AMPK), a serine/threonine kinase, is a heterotrimeric complex containing one catalytic α subunit and regulatory β and γ subunits. AMP or ADP can directly bind to the regulatory γ subunits of AMPK, leading to a conformational change that promotes its activation [1]. Full AMPK activation requires specific phosphorylation of the α subunit at Thr172 by upstream kinases [2, 3]. AMPK restores cellular energy levels by promoting catabolic and inhibiting anabolic processes. AMPK directly phosphorylates a number of downstream targets including ACC, ULK (protein kinases that initiate autophagy), and mTORC1 (mammalian target of rapamycin complex 1), which act as mediator/effectors to metabolism, cell growth, and autophagy [1, 4,5,6]. The process engulfs regions of cytoplasm, protein aggregates, and damaged organelles into doublemembrane autophagosomes, which fuse with lysosomes for further degradation and cellular recycling [5,6,7]

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