Novel action of epidermal growth factor on caspase 3 and its potential as a chemotherapeutic adjunct for neuroblastoma

We previously reported that epidermal growth factor (EGF) induced cleaved caspase 3 expression and apoptosis in human neuroblastoma cells. We hypothesized that EGF upregulates total caspase 3 expression, thereby enhancing the cytotoxic potency of chemotherapeutic agents.

Wild-type (WT) and doxorubicin-resistant (Dox-R) SK-N-SH neuroblastoma cells were incubated with EGF 0 to 250 ng/mL for 24 hours or with 5 ng/mL for 0 to 5 days, and total caspase 3 expression and transcription were determined by immunoblots and reverse transcription and polymerase chain reaction, respectively. Cell proliferation was determined after EGF (5 ng/mL) incubation for 1 to 5 days. Cells incubated with EGF (5 ng/mL) for 24 hours before doxorubicin treatment were used to determine the effect of EGF on cell replication and cleaved caspase 3 expression.

Wild-type and Dox-R cells had maximal total caspase 3 expression after incubation with EGF (5 ng/mL) for 3 and 5 days, respectively, and a corresponding increase in DNA transcription. Treating the cells with or without EGF (5 ng/mL) resulted in similar replication rate. However, cell death was increased by EGF pretreatment and doxorubicin when compared with that by doxorubicin alone (WT, 53% +/- 8%; Dox-R, 44% +/- 9%; P < .05). Cleaved caspase 3 expression was upregulated when cell death was increased.

Epidermal growth factor upregulates the expression and transcription of total caspase 3 in WT and Dox-R cells in a concentration- and time-dependent manner. Epidermal growth factor pretreatment augments the cytotoxic effect of doxorubicin.