Tyrosine kinase inhibitors (TKIs) are frequently used in combined therapy to enhance treatment efficacy and overcome drug resistance. The present study analyzed the effects of three inhibitors, sunitinib, gefitinib, and lapatinib, combined with iron-chelating agents, di-2-pyridylketone-4,4-dimethyl-3-thiosemicarbazone (Dp44mT) or di-2-pyridylketone-4-cyclohexyl-4-methyl-3-thiosemicarbazone (DpC). Simultaneous administration of the drugs consistently resulted in synergistic and/or additive activities against the cell lines derived from the most frequent types of pediatric solid tumors. The results of a detailed analysis of cell signaling in the neuroblastoma cell lines revealed that TKIs inhibited the phosphorylation of the corresponding receptor tyrosine kinases, and thiosemicarbazones downregulated the expression of epidermal growth factor receptor, platelet-derived growth factor receptor, and insulin-like growth factor-1 receptor, leading to a strong induction of apoptosis. Marked upregulation of the metastasis suppressor N-myc downstream regulated gene-1 (NDRG1), which is known to be activated and upregulated by thiosemicarbazones in adult cancers, was also detected in thiosemicarbazone-treated neuroblastoma cells. Importantly, these effects were more pronounced in the cells treated with drug combinations, especially with the combinations of lapatinib with thiosemicarbazones. Therefore, these results provide a rationale for novel strategies combining iron-chelating agents with TKIs in therapy of pediatric solid tumors.

• Keywords
• NDRG1, neuroblastoma, pediatric solid tumors, receptor tyrosine kinases, thiosemicarbazones, tyrosine kinase inhibitors,
• Publication type
• Journal Article MeSH

Despite constant advances in the field of pediatric oncology, the survival rate of high-risk neuroblastoma patients remains poor. The molecular and genetic features of neuroblastoma, such as MYCN amplification and stemness status, have established themselves not only as potent prognostic and predictive factors but also as intriguing targets for personalized therapy. Novel thiosemicarbazones target both total level and activity of a number of proteins involved in some of the most important signaling pathways in neuroblastoma. In this study, we found that di-2-pyridylketone 4-cyclohexyl-4-methyl-3-thiosemicarbazone (DpC) potently decreases N-MYC in MYCN-amplified and c-MYC in MYCN-nonamplified neuroblastoma cell lines. Furthermore, DpC succeeded in downregulating total EGFR and phosphorylation of its most prominent tyrosine residues through the involvement of NDRG1, a positive prognostic marker in neuroblastoma, which was markedly upregulated after thiosemicarbazone treatment. These findings could provide useful knowledge for the treatment of MYC-driven neuroblastomas that are unresponsive to conventional therapies.

• Keywords
• DpC, EGFR, MYC, NDRG1, lipid droplet, neuroblastoma, thiosemicarbazone,
• MeSH
• Gene Amplification drug effects   MeSH
• Models, Biological MeSH
• Iron Chelating Agents pharmacology   MeSH
• Down-Regulation drug effects   MeSH
• ErbB Receptors metabolism   MeSH
• Phosphorylation drug effects   MeSH
• Stress, Physiological drug effects   MeSH
• Intracellular Signaling Peptides and Proteins metabolism   MeSH
• Humans MeSH
• Cell Line, Tumor MeSH
• Neuroblastoma metabolism   pathology   MeSH
• Cell Cycle Proteins metabolism   MeSH
• N-Myc Proto-Oncogene Protein metabolism   MeSH
• Proto-Oncogene Proteins c-akt metabolism   MeSH
• Pyridines pharmacology   MeSH
• Signal Transduction * MeSH
• Thiosemicarbazones pharmacology   MeSH
• Cell Shape drug effects   MeSH
• Gene Silencing drug effects   MeSH
• Up-Regulation drug effects   MeSH
• Check Tag
• Humans MeSH
• Publication type
• Journal Article MeSH
• Names of Substances
• Iron Chelating Agents MeSH
• di-2-pyridylketone 4-cyclohexyl-4-methyl-3-thiosemicarbazone MeSH Browser
• ErbB Receptors MeSH
• Intracellular Signaling Peptides and Proteins MeSH
• N-myc downstream-regulated gene 1 protein MeSH Browser
• Cell Cycle Proteins MeSH
• N-Myc Proto-Oncogene Protein MeSH
• Proto-Oncogene Proteins c-akt MeSH
• Pyridines MeSH
• Thiosemicarbazones MeSH