Targeting breast cancer metabolism with a novel inhibitor of mitochondrial ATP synthesis.

Myoung Sook Kim,Paul Shapiro,Brian M Polster,Ramon Martinez,Santosh Kesari,Antonino Passaniti,Ramkishore Gernapudi,Yessenia Cedeño Cedeño,Elmar Nurmemmedov

doi:10.18632/oncotarget.27743

Abstract

Inhibitors of mitochondrial respiration and ATP synthesis may promote the selective killing of respiration-competent cancer cells that are critical for tumor progression. We previously reported that CADD522, a small molecule inhibitor of the RUNX2 transcription factor, has potential for breast cancer treatment. In the current study, we show that CADD522 inhibits mitochondrial oxidative phosphorylation by decreasing the mitochondrial oxygen consumption rate (OCR) and ATP production in human breast cancer cells in a RUNX2-independent manner. The enzyme activity of mitochondrial ATP synthase was inhibited by CADD522 treatment. Importantly, results from cellular thermal shift assays that detect drug-induced protein stabilization revealed that CADD522 interacts with both α and β subunits of the F1-ATP synthase complex. Differential scanning fluorimetry also demonstrated interaction of α subunits of the F1-ATP synthase to CADD522. These results suggest that CADD522 might target the enzymatic F1 subunits in the ATP synthase complex. CADD522 increased the levels of intracellular reactive oxygen species (ROS), which was prevented by MitoQ, a mitochondria-targeted antioxidant, suggesting that cancer cells exposed to CADD522 may elevate ROS from mitochondria. CADD522-increased mitochondrial ROS levels were enhanced by exogenously added pro-oxidants such as hydrogen peroxide or tert-butyl hydroperoxide. Conversely, CADD522-mediated cell growth inhibition was blocked by N-acetyl-l-cysteine, a general ROS scavenger. Therefore, CADD522 may exert its antitumor activity by increasing mitochondrial driven cellular ROS levels. Collectively, our data suggest in vitro proof-of-concept that supports inhibition of mitochondrial ATP synthase and ROS generation as contributors to the effectiveness of CADD522 in suppression of tumor growth.

Highlights

Breast cancer (BC) is the second leading cause of cancer-related deaths among women, but early detection and improved treatment options have led to increased patient survival
Our extended studies demonstrate that ATP levels and mitochondrial ATP synthase activity significantly increase in Hs578t cells after RUNX2 KD compared to non-targeting control (NTC) (Supplementary Figure 1A and 1B)
These findings indicate that RUNX2 KD results in activation of mitochondrial ATP synthase activity, which may lead to increases in respiration [54], ATP production and reactive oxygen species (ROS) generation

Summary

Introduction

Breast cancer (BC) is the second leading cause of cancer-related deaths among women, but early detection and improved treatment options have led to increased patient survival. Chemotherapy, www.oncotarget.com radiation and hormonal therapy are useful in treating advanced BC [2], targeting cancer metabolism has become an attractive therapeutic option [3,4,5,6]. Alterations of mitochondrial function are associated with development of several types of cancer [7]. In contrast to Warburg’s first observations, maintaining functional mitochondria appears to be key for cancer cell survival and proliferation [8]. Mitochondria are still functional in glycolytic cancer cells (with high Glut-1 and phosphoAkt expression) producing abundant amounts of ATP [9]. Functional mitochondria that are respiration competent are critical for tumorigenesis and targeting mitochondrial metabolism may be a novel and successful therapeutic strategy for cancer [7]

Methods

Results

Conclusion