The novel thiosemicarbazone, di-2-pyridylketone 4-cyclohexyl-4-methyl-3-thiosemicarbazone (DpC), inhibits neuroblastoma growth in vitro and in vivo via multiple mechanisms.
BACKGROUND
Neuroblastoma is a relatively common and highly belligerent childhood tumor with poor prognosis by current therapeutic approaches. A novel anti-cancer agent of the di-2-pyridylketone thiosemicarbazone series, namely di-2-pyridylketone 4,4-dimethyl-3-thiosemicarbazone (Dp44mT), demonstrates promising anti-tumor activity. Recently, a second-generation analogue, namely di-2-pyridylketone 4-cyclohexyl-4-methyl-3-thiosemicarbazone (DpC), has entered multi-center clinical trials for the treatment of advanced and resistant tumors. The current aim was to examine if these novel agents were effective against aggressive neuroblastoma in vitro and in vivo and to assess their mechanism of action.


METHODS
Neuroblastoma cancer cells as well as immortalized normal cells were used to assess the efficacy and selectivity of DpC in vitro. An orthotopic SK-N-LP/Luciferase xenograft model was used in nude mice to assess the efficacy of DpC in vivo. Apoptosis in tumors was confirmed by Annexin V/PI flow cytometry and H&E staining.


RESULTS
DpC demonstrated more potent cytotoxicity than Dp44mT against neuroblastoma cells in a dose- and time-dependent manner. DpC significantly increased levels of phosphorylated JNK, neuroglobin, cytoglobin, and cleaved caspase 3 and 9, while decreasing IkBα levels in vitro. The contribution of JNK, NF-ĸB, and caspase signaling/activity to the anti-tumor activity of DpC was verified by selective inhibitors of these pathways. After 3 weeks of treatment, tumor growth in mice was significantly (p < 0.05) reduced by DpC (4 mg/kg/day) given intravenously and the agent was well tolerated. Xenograft tissues showed significantly higher expression of neuroglobin, cytoglobin, caspase 3, and tumor necrosis factor-α (TNFα) levels and a slight decrease in interleukin-10 (IL-10).


CONCLUSIONS
DpC was found to be highly potent against neuroblastoma, demonstrating its potential as a novel therapeutic for this disease. The ability of DpC to increase TNFα in tumors could also promote the endogenous immune response to mediate enhanced cancer cell apoptosis.
Department of Stomatology, Affiliated Hospital of Hainan Medical University, Hainan, People's Republic of China.|School of Stomatology, Hainan Medical University, Hainan, People's Republic of China.|Department of Paediatrics & Adolescent Medicine, Queen Mary Hospital, The University of Hong Kong, Hong Kong, SAR, China.
Zhu-Ling
ZL
Guo
Molecular Pharmacology and Pathology Program, Department of Pathology, University of Sydney, Sydney, New South Wales, Australia. d.richardson@sydney.edu.au.
Des R
DR
Richardson
Molecular Pharmacology and Pathology Program, Department of Pathology, University of Sydney, Sydney, New South Wales, Australia.
Danuta S
DS
Kalinowski
Molecular Pharmacology and Pathology Program, Department of Pathology, University of Sydney, Sydney, New South Wales, Australia.
Zaklina
Z
Kovacevic
School of Professional and Continuing Education, The University of Hong Kong, Hong Kong, SAR, People's Republic of China.
Kian Cheng
KC
Tan-Un
Department of Paediatrics & Adolescent Medicine, Queen Mary Hospital, The University of Hong Kong, Hong Kong, SAR, China. gcfchan@hku.hk.
Godfrey Chi-Fung
GC
Chan
Thiosemicarbazone; cancer treatment; di-2-pyridylketone 4,4-dimethyl-3-thiosemicarbazone (Dp44mT); molecular pharmacology; neuroblastoma
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