Emodin, as a mitochondrial uncoupler, induces strong decreases in adenosine triphosphate (ATP) levels and proliferation of B16F10 cells, owing to their poor glycolytic reserve.

Yuma Sugiyama,Toshiyuki Shudo,Akira Kakizuka,Aki Watanabe,Sho Hosokawa,Masaki Nakano

doi:10.1111/gtc.12712

Yuma Sugiyama, Toshiyuki Shudo + Show 4 more

Open Access

https://doi.org/10.1111/gtc.12712

Copy DOI

Abstract

Many types of cancer cells show a characteristic increase in glycolysis, which is called the "Warburg effect." By screening plant extracts, we identified one that decreases cellular adenosine triphosphate (ATP) levels and suppresses proliferation of malignant melanoma B16F10 cells, but not of noncancerous MEF cells. We showed that its active ingredient is emodin, which showed strong antiproliferative effects on B16F10 cells both in vitro and in vivo. Moreover, we also found that emodin can function as a mitochondrial uncoupler. Consistently, three known mitochondrial uncouplers also displayed potent antiproliferative effects and preferential cellular ATP reduction in B16F10 cells, but not in MEF cells. These uncouplers provoked comparable mitochondrial uncoupling in both cell types, but they manifested dramatically different cellular effects. Namely in MEF cells, these uncouplers induced three to fivefold increases in glycolysis from the basal state, and this compensatory activation appeared to be responsible for the maintenance of cellular ATP levels. In contrast, B16F10 cells treated with the uncouplers showed less than a twofold enhancement of glycolysis, which was not sufficient to compensate for the decrease of ATP production. Together, these results raise the possibility that uncouplers could be effective therapeutic agents specifically for cancer cells with prominent "Warburg effect."

Highlights

Even with the impressive advances in medical care over the last several decades, about one out of two Japanese suffers from cancer over their lifetime, and one third of Japanese die of cancer
We first evaluated the mitochondrial membrane potential (MMP) by using tetramethylrhodamine methyl ester (TMRM) and we found that the addition of emodin rapidly reduced the MMP, which dropped to levels approximately 30% of those before its addition, within only 30 min (Figure 4a) (Qu et al, 2013)
Given the enhanced sensitivity of B16F10 cells to emodin, we focused on another energy‐producing system, glycolysis, in cells treated with uncouplers

Summary

| INTRODUCTION

Even with the impressive advances in medical care over the last several decades, about one out of two Japanese suffers from cancer over their lifetime, and one third of Japanese die of cancer. In 2000, it was reported that a target of metformin in cancer cells was mitochondrial respiratory chain complex I (El‐Mir et al, 2000; Owen, Doran, & Halestrap, 2000), and this drug is being tested in clinical trials for different types of cancers (Vernieri et al, 2016). We evaluated compounds that reduce ATP levels in B16F10 cells and found a plant extract from rhizomes of Polygonum cuspidatum (RPC). This plant extract has long been administrated to human body as a component of a traditional medicine, and various types of pharmacological effects are known like treating cough, hepatitis, jaundice, arthralgia and skin burns. We propose mitochondrial uncoupling as a potential therapeutic strategy for cancer treatment, especially for cancers with enhanced energetic demands and reduced glycolytic reserves, like melanoma

| RESULTS

| DISCUSSION

| EXPERIMENTAL PROCEDURES

Findings

F2-1 Peak B