17-(dimethylaminoethylamino)-17-demethoxygeldanamycin and Neuroblastoma

Neuroblastoma (NB), an embryonal tumor derived from the neural crest, originates from sympathetic nerve system, manifests as thoracic, paraspinous or abdominal tumors, and metastases to bone in high-risk cases. Although NB stands as the most common solid tumor in early childhood and accounts for about 15% of total pediatric cancer death, there has been limited success in searching for novel therapeutic regimen for this lethal disease during the past two decades. Numerous epidemiological and clinical studies have pinpointed anaplastic lymphoma kinase (ALK) and MYCN as potent governors for NB malignant behavior. ALK and MYCN amplification and constitutive active mutations are common in high-risk NB patients. However, there is still lack of evidence showing that a small molecule compound could simultaneously inhibits ALK and MYCN and plays strong negative regulatory roles in NB. Here, we showed that 17-DMAG, a well-known HSP-90 inhibitor, significantly inhibits NB cell growth, arrests cell cycle, and strongly induces NB cell apoptosis. Interestingly, our data suggests that NB cells with both ALK and MYCN amplification/mutation are more sensitive to 17-DMAG treatment, while NB cells with only ALK or MYCN amplification are less sensitive and NB cells without ALK or MYCN amplification/mutation are least sensitive. Moreover, we also found that knocking down ALK and MYCN additively inhibits NB cell growth and that transduction of MYCN largely abolished the ALK-dependent NB cell growth, indicating that there is a cross-talk between MYCN and ALK signaling machinery. Our results provide proof-of-principle that 17-DMAG strongly inhibits NB cell growth by targeting both ALK and MYCN. Our findings might shed a light for further investigation of novel small molecule compound which is safe and exerts similar strong effects in vivo as novel approaches for management of high-risk NB.

Topics: Anaplastic Lymphoma Kinase; Benzoquinones; Cell Line, Tumor; Cell Proliferation; HSP90 Heat-Shock Proteins; Humans; Lactams, Macrocyclic; N-Myc Proto-Oncogene Protein; Neuroblastoma; Nuclear Proteins; Oncogene Proteins; Receptor Protein-Tyrosine Kinases

Neuroblastoma is a childhood cancer that exhibits either a favorable or an unfavorable phenotype. MYCN and MYC are oncoproteins that play crucial roles in determining the malignancy of unfavorable neuroblastoma. The Hsp90 superchaperone complex assists in the folding and function of a variety of oncogenic client proteins. Inhibition of Hsp90 by small molecule inhibitors leads to the destabilization of these oncogenic proteins and consequently suppresses tumor malignancy. Nonetheless, little is known about the effect of Hsp90 inhibition on the stability of MYCN and MYC proteins. In this study, we investigated the effect of Hsp90 inhibition on the phenotype of unfavorable neuroblastoma cells including its effect on MYCN and MYC expression. Two MYCN-amplified neuroblastoma cell lines (IMR5 and CHP134) and two non-MYCN-amplified cell lines (SY5Y and SKNAS) were used to address the effect of Hsp90 inhibition on the malignant phenotype of neuroblastoma. It was found that Hsp90 inhibition in neuroblastoma cell lines resulted in significant growth suppression, a decrease in MYCN and MYC expression, and an increase in the expression of p53. In the TP53-mutated SKNAS cell line, Hsp90 inhibition enhanced the expression of the favorable neuroblastoma genes EFNB2, MIZ-1 and NTRK1 (TrkA). In addition, Hsp90 inhibition reduced HDAC6 expression and enhanced tubulin acetylation. Together our data suggest that Hsp90 inhibition suppresses the growth of neuroblastoma through multiple cellular pathways and that MYC/MYCN destabilization is among the important consequences of Hsp90 inhibition.

Topics: Acetylation; Benzoquinones; Cell Line, Tumor; Cyclin-Dependent Kinase Inhibitor p21; Gene Expression Regulation, Neoplastic; Genes, myc; Genes, p53; HSP90 Heat-Shock Proteins; Humans; Lactams, Macrocyclic; N-Myc Proto-Oncogene Protein; Neuroblastoma; Nuclear Proteins; Oncogene Proteins; Proto-Oncogene Proteins c-akt; Proto-Oncogene Proteins c-myc; Transfection; Tubulin; Tumor Suppressor Protein p53