The novel melphalan prodrug J1 inhibits neuroblastoma growthin vitroandin vivo

Abstract

Neuroblastoma is the most common extracranial solid tumor of childhood. The activity of J1 (L-melphalanyl-p-Lfluorophenylalanine ethyl ester), an enzymatically activated melphalan prodrug, was evaluated in neuroblastoma models in vitro and in vivo. Seven neuroblastoma cell lines with various levels of drug resistance were screened for cytotoxicity of J1 alone or in combination with standard cytotoxic drugs, using a fluorometric cytotoxicity assay. J1 displayed high cytotoxic activity in vitro against all neuroblastoma cell lines, with IC 50 values in the submicromolar range, significantly more potent than melphalan. The cytotoxicity of J1, but not melphalan, could be significantly inhibited by the aminopeptidase inhibitor bestatin. J1 induced caspase-3 cleavage and apoptotic morphology, had additive effects in combination with doxorubicin, cyclophosphamide, carboplatin, and vincristine, and synergistically killed otherwise drugresistant cells when combined with etoposide. Athymic rats and mice carrying neuroblastoma xenografts [SH-SY5Y, SK-N-BE(2)] were treated with equimolar doses of melphalan, J1, or no drug, and effects on tumor growth and tissue morphology were analyzed. Tumor growth in vivo was significantly inhibited by J1 compared with untreated controls. Compared with melphalan, J1 more effectively inhibited the growth of mice with SH-SY5Y xenografts, was associated with higher caspase-3 activation, fewer proliferating tumor cells, and significantly decreased mean vascular density. In conclusion, the melphalan prodrug J1 is highly active in models of neuroblastoma in vitro and in vivo, encouraging further clinical development in this patient group.

The Cell Biology of Neuroblastoma

“…This places promoters near genes that they would normally not affect, and this increases the likelihood of converting a proto-oncogene to an oncogene. In the highest risk form of neuroblastoma the cells contain cytogenetic alterations such as MYCN amplification or 1p deletion (Wickstrom et al, 2007). The 6p22 locus is associated with clinically aggressive neuroblastoma .…”

“…It consolidates the response to induction chemotherapy (Pritchard et al, 2005). The melphalan prodrug J1 (L-melphalanylp-L-fluorophenylalanine ethyl ester) displayed high cytotoxic activity in vitro against seven neuroblastoma cell lines, with IC50 values in the submicromolar range (Wickstrom et al, 2007). J1 induced caspase-3 cleavage and apoptotic morphology, had additive effects with doxorubicin, cyclophosphamide, carboplatin, and vincristine, and killed otherwise drugresistant cells when combined with etoposide (Wickstrom et al, 2007).…”

“…The melphalan prodrug J1 (L-melphalanylp-L-fluorophenylalanine ethyl ester) displayed high cytotoxic activity in vitro against seven neuroblastoma cell lines, with IC50 values in the submicromolar range (Wickstrom et al, 2007). J1 induced caspase-3 cleavage and apoptotic morphology, had additive effects with doxorubicin, cyclophosphamide, carboplatin, and vincristine, and killed otherwise drugresistant cells when combined with etoposide (Wickstrom et al, 2007). Also susceptible to J1 were athymic rats and mice carrying neuroblastoma xenografts containing SH-SY5Y and SK-N-BE(2) cells (Wickstrom et al, 2007).…”

“…J1 induced caspase-3 cleavage and apoptotic morphology, had additive effects with doxorubicin, cyclophosphamide, carboplatin, and vincristine, and killed otherwise drugresistant cells when combined with etoposide (Wickstrom et al, 2007). Also susceptible to J1 were athymic rats and mice carrying neuroblastoma xenografts containing SH-SY5Y and SK-N-BE(2) cells (Wickstrom et al, 2007). Of all the alkylating agents, cyclophosphamide stands at the forefront of therapy in neuroblastoma.…”

“…Neuroblastoma is the third most common solid tumor in children and is the most common extracranial solid tumor in children (Maris, 2010;Coulter et al, 2008;Wickstrom et al, 2007). It is highly malignant and has a poor outcome despite aggressive treatment, even with autologous stem cell transplantation (Sartelet et al, 2008).…”