Cambogin exerts anti-proliferative and pro-apoptotic effects on breast adenocarcinoma through the induction of NADPH oxidase 1 and the alteration of mitochondrial morphology and dynamics

Abstract

// Kaikai Shen 1, * , Fangfang Lu 1, * , Jianling Xie 4, 5 , Minfeng Wu 1 , Bo Cai 1 , Yurong Liu 1 , Hong Zhang 1, 3 , Hongsheng Tan 1, 3 , Yingyi Pan 1 , Hongxi Xu 1, 2, 3 1 School of Pharmacy, Shanghai University of Traditional Chinese Medicine, Shanghai 201203, China 2 Institute of Arthritis Research, Shanghai Academy of Chinese Medical Sciences, Guanghua Integrative Medicine Hospital/Shanghai University of T.C.M, Shanghai 201203, China 3 Engineering Research Center of Shanghai Colleges for TCM New Drug Discovery, Shanghai 201203, China 4 Nutrition & Metabolism, South Australian Health & Medical Research Institute, North Terrace, Adelaide SA5000, Australia 5 Centre for Biological Sciences, Life Sciences Building, University of Southampton, Southampton, SO17 1BJ, UK * These authors have contributed equally to this work Correspondence to: Hongxi Xu, email: xuhongxi88@gmail.com Yingyi Pan, email: pyy16@126.com Keywords: breast cancer, cambogin, reactive oxygen species, NADPH oxidase 1, thioredoxin-1/ASK1 complex Received: December 02, 2015      Accepted: June 29, 2016      Published: July 13, 2016 ABSTRACT Cambogin, a bioactive polycyclic polyprenylated acylphoroglucinol (PPAP) derived from the Garcinia genus, possesses proapoptotic effect in medulloblastoma and breast cancer cells. We have previously demonstrated that the proapoptotic effect of cambogin is driven by the production of reactive oxygen species (ROS). Here we have shown that the inhibitory effect of cambogin on cell proliferation is associated with the loss of mitochondrial transmembrane potential (Δ Ψ m ) and mitochondrial fragmentation. Cambogin also promotes the mutual complex formation of the membrane-bound subunit p22 phox of NADPH oxidase 1 (NOX1), as well as the phosphorylation of the cytosolic subunit p47 phox , subsequently enhancing membrane-bound NOX1 activity, which leads to increases in intracellular and mitochondrial levels of O 2 .- and H 2 O 2 . Pharmacological inhibition of NOX1 using apocynin (pan-NOX inhibitor), ML171 (NOX1 inhibitor) or siRNA against NOX1 prevents the increases in O 2 .- and H 2 O 2 levels and the anti-proliferative effect of cambogin. Antioxidants, including SOD (superoxide dismutase), CAT (catalase) and EUK-8, are also able to restore cell viability in the presence of cambogin. Besides, cambogin increases the dissociation of thioredoxin-1 (Trx1) from ASK1, switching the inactive form of ASK1 to the active kinase, subsequently leads to the phosphorylation of JNK/SAPK, which is abolished upon ML171 treatment. The proapoptotic effect of cambogin in breast cancer cells is also aggravated upon knocking down Trx1 in MCF-7 cells. Taken in conjunction, these data indicate that the anti-proliferative and pro-apoptotic effect of cambogin is mediated via inducing NOX1-dependent ROS production and the dissociation of ASK1 and Trx1.