The heat shock protein 90 inhibitor SNX-2112 inhibits B16 melanoma cell growth in vitro and in vivo

Abstract

Abstract. SNX-2112 is a selective heat shock protein 90 (Hsp90) inhibitor which can exert a potent anticancer activity. In this study, we investigated the effects of SNX-2112 on B16 melanoma cells in vitro and in vivo. The 3-(4,5-dimetrylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide (MTT) assay and flow cytometric analysis demonstrated that SNX-2112 dosedependently inhibited the growth of B16 cells, and induced G0/ G1 cell cycle arrest and apoptosis. Western blotting revealed that SNX-2112 lead to the degradation of Hsp90 client proteins including Akt, IKKα, NF-κB, B-Raf and GSK3β. Furthermore, we assessed the antitumor effect of SNX-2112 in vivo, using a xenograft model in C57BL/6 mice. Oral administration of SNX-2112 significantly inhibited the growth of B16 tumors in mice, with a 47% inhibition observed at dose of 80 mg/kg/day for 15 days, compared to control tumors. Hematoxylin-eosin (H&E) staining of xenograft tissues showed that SNX-2112 also inhibited angiogenesis and lead to a lower blood vessel density in the tumors, compared to the control group. These findings demonstrate that SNX-2112 can exhibit a potent anticancer activity against B16 melanoma cells both in vitro and in vivo, by inhibiting cell proliferation and inducing cell cycle arrest and apoptosis in a mechanism dependent on the degradation of Hsp90 client proteins. IntroductionHsp90 is an important ATP-dependent molecular chaperone required for protein folding, as well as the assembly and maintenance of the conformational stability of a diverse range of client proteins. Hsp90 client proteins play key roles in cellular metabolism, trafficking, signal transduction, chromatin remodeling, cell growth and differentiation (1-4). Hsp90 client proteins include cell survival and proliferation regulators, such as Akt, IKK, Raf, GSK3 and NF-κB (5-7). Hsp90 is overexpressed in tumor cells compared to their normal counterparts (8), and inhibition of Hsp90 has been considered as a possible strategy for the treatment of cancer.Currently, 14 drug candidates which target Hsp90 are undergoing clinical trials for multiple indications, either as single agents or in combination therapy, including 17-(allylamino)-17-demethoxygeldanamycin (17-AAG), 17-allylamino-17-demethoxygeldanamycin hydroquinone hydrochloride (IPI-504) and BIIB021 (9). 17-AAG was the first Hsp90 inhibitor to undergo phase III clinical trials, and is well tolerated and has a good therapeutic efficacy. However, 17-AAG has several potential limitations, including poor solubility, limited bioavailability and unsatisfactory hepatotoxicity (10-12). This has led to efforts to identify new, safer and more effective Hsp90 inhibitors for clinical applications.SNX-2112, a selective Hsp90 inhibitor, can bind to the N-terminal adenosine triphosphate binding site of Hsp90 and can exert significant growth inhibition of various cancer cell lines both in vitro and in vivo (13,14). In our previous research, SNX-2112 displayed promising anti-tumor activity in human chronic leukemia 16). In addition, SNX-2112 is ...

Inhibitors of HSP90 in melanoma

“…SNX-2112 more potently inhibited melanoma cell proliferation than 17-AAG [133,134], and arrested cells in G0/G1 phase of cell cycle in a dose-dependent manner [133]. SNX-2112 induced a time-dependent degradation of HSP90 client proteins crucial for melanoma cell maintenance including AKT, IKKα, BRAF and glycogen synthase kinase 3 beta (GSK-3β) [133]. SNX-2112 also induced apoptosis in melanoma cells [132,134], which was associated with an activation of caspase-3, caspase-7 and caspase-8, and PARP cleavage.…”

“…SNX-2112 is an N-terminal domain binding HSP90 inhibitor containing the 2-aminobenzamide scaffold [132]. SNX-2112 more potently inhibited melanoma cell proliferation than 17-AAG [133,134], and arrested cells in G0/G1 phase of cell cycle in a dose-dependent manner [133]. SNX-2112 induced a time-dependent degradation of HSP90 client proteins crucial for melanoma cell maintenance including AKT, IKKα, BRAF and glycogen synthase kinase 3 beta (GSK-3β) [133].…”

Suppression of Esophageal Cancer Stem-like Cells by SNX-2112 Is Enhanced by STAT3 Silencing

“…At the same time, they found that suppression of Hsp90 effectively targeted the functionality of thyroid CSCs, which prevented their migration and invasion (White et al, 2016). In our previous studies, the Hsp90 inhibitor SNX-2112 demonstrated antitumor activity by induction of apoptosis and cell cycle arrest of melanoma cells, and inhibiting tumor growth in vivo (Liu et al, 2012a;Liu et al, 2012b;Wang et al, 2014). In addition, it exerted its inhibitory effect on various cancer cells by binding to the N-terminal adenosine triphosphate binding site of Hsp90 (Wang et al, 2015).…”

Hsp90 Inhibitor SNX-2112 Enhances TRAIL-Induced Apoptosis of Human Cervical Cancer Cells via the ROS-Mediated JNK-p53-Autophagy-DR5 Pathway

“…We have previously proven that SNX-2112 was a novel, highly efficient, and highly selective small molecule inhibitor of Hsp90 that could competitively integrate with the N-terminal ATP-binding site of Hsp90 and exhibit anticancer activity in cancer cells, including breast cancer [34], multiple myeloma [35], melanoma [36, 37], chronic myeloid leukemia [38], esophageal cancer [39], and head and neck squamous cell carcinomas [40]. Especially in human hepatocellular carcinoma cells, SNX-2112 could induce apoptosis, elevating the role of ER stress [41].…”