N. Gupta, S. Srivastava
Jul 1, 2019
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Experimental and Molecular Therapeutics
Abstract
Breast cancer is one of the most common malignancies and the second leading cause of cancer related mortality among women in U.S., thus developing new strategies to control breast cancer is an important mission. Repurposing of old drugs as new anti-cancer drugs is important as it can save time and cost of drug development. Proguanil is used in combination with atovaquone for the treatment of malaria. In this study, we determined the anticancer effects of proguanil in breast cancer cells. Proguanil significantly reduced the viability of MDA-MB-231, HCC1806 and MCF-7 breast cancer cells with IC50 of 42μM, 44μM and 40μM respectively after 72 h of treatment and induced apoptosis as exhibited by FITC/Annexin assay and cleavage of caspase 3 as well as PARP. Proguanil also reduced the survival of several patient-derived cells with IC50 in the range of 30-40μM. The anti-cancer effects of proguanil were associated with the generation of ROS and persistent disruption of mitochondrial membrane potential. ROS generation by proguanil was about 2-3 fold more as compared to control in MDA-MB-231 and HCC1806 cells. The generation of ROS was inhibited when the cells were pretreated with a general antioxidant N-acetyl cysteine (NAC). Moreover, exposure of MDA-MB-231 and HCC1806 cells to proguanil was also associated with increased expression of Bax, p-H2AX, c-caspase9 and down-regulation of bcl-2 and survivin. We further evaluated the oxygen consumption rate with proguanil treatment in breast cancer cells using flux analyzer. Our results showed significant decrease in the mitochondrial respiration rate and ATP production rate after proguanil treatment. Furthermore, 20mg/kg proguanil when given orally suppressed the growth of 4T1 breast tumors in female Balb/c mice by 55%. Tumors from proguanil treated mice demonstrated increased apoptosis, which was related to the increased expression of p-H2AX and Bax. Taken together, these results show that proguanil is an effective inhibitor of in vitro and in-vivo growth of breast cancer cells. These findings provide the rationale for further clinical investigation of proguanil against breast cancer. Citation Format: Nehal Gupta, Sanjay Srivastava. Oxidative stress by proguanil suppresses breast tumor growth [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 4795.