In vitro and in vivo anti-leukemic effects of cladoloside C2 are mediated by activation of Fas/ceramide synthase 6/p38 kinase/c-Jun NH2-terminal kinase/caspase-8

// Seong-Hoon Yun 1 , Eun-Hye Sim 1 , Sang-Heum Han 1 , Tae-Rang Kim 1 , Mi-Ha Ju 2 , Jin-Yeong Han 3 , Jin-Sook Jeong 2 , Sung-Hyun Kim 4 , Alexandra S. Silchenko 5 , Valentin A. Stonik 5 and Joo-In Park 1 1 Department of Biochemistry, Dong-A University College of Medicine, Busan, South Korea 2 Department of Pathology, Dong-A University College of Medicine, Busan, South Korea 3 Department of Laboratory Medicine, Dong-A University College of Medicine, Busan, South Korea 4 Department of Internal Medicine, Dong-A University College of Medicine, Busan, South Korea 5 G.B. Elyakov Pacific Institute of Bio-organic Chemistry, Far-Eastern Branch of the Russian Academy of Sciences, Vladivostok, Russia Correspondence to: Joo-In Park, email: jipark@dau.ac.kr Keywords: marine triterpene glycoside; ceramide synthase 6; JNK; caspase-8; anti-leukemic activity Received: August 03, 2017      Accepted: November 14, 2017      Published: December 08, 2017 ABSTRACT We previously demonstrated that the quinovose-containing hexaoside stichoposide C (STC) is a more potent anti-leukemic agent than the glucose-containing stichoposide D (STD), and that these substances have different molecular mechanisms of action. In the present study, we investigated the novel marine triterpene glycoside cladoloside C 2 from Cladolabes schmeltzii , which has the same carbohydrate moiety as STC. We assessed whether cladoloside C 2 could induce apoptosis in K562 and HL-60 cells. We also evaluated whether it showed antitumor action in mouse leukemia xenograft models, and its molecular mechanisms of action. We investigated the molecular mechanism behind cladoloside C 2 -induced apoptosis of human leukemia cells, and examined the antitumor effect of cladoloside C 2 in a HL-60 and K562 leukemia xenograft model. Cladoloside C 2 dose- and time-dependently induced apoptosis in the analyzed cells, and led to the activation of Fas/ceramide synthase 6 (CerS6)/p38 kinase/JNK/caspase-8. This cladoloside C 2 -induced apoptosis was partially blocked by specific inhibition by Fas, CerS6, and p38 siRNA transfection, and by specific inhibition of JNK by SP600125 or dominant negative-JNK transfection. Cladoloside C 2 exerted antitumor activity through the activation of Fas/CerS6/p38 kinase/JNK/caspase-8 without showing any toxicity in xenograft mouse models. The antitumor effect of cladoloside C 2 was reversed in CerS6 shRNA-silenced xenograft models. Our results suggest that cladoloside C2 has in vitro and in vivo anti-leukemic effects due to the activation of Fas/CerS6/p38 kinase/JNK/caspase-8 in lipid rafts. These findings support the therapeutic relevance of cladoloside C 2 in the treatment of human leukemia.