ASCORBIC-ACID RECYCLING IN N-MYC AMPLIFIED HUMAN NEUROBLASTOMA-CELLS

The present study investigated the ability of two neuroblastoma cell l ines (SK-N-SH, with one copy of N-myc, and SK-N-BE(2), with over 150 c opies of N-myc) to recycle ascorbate by quantifying semidehydroascorba te reductase and dehydroascorbate reductase activities. Both cell line s expressed dehydroascorbate activity (SK-N-SH 28.4+/-9.8, SK-N-BE(2) 21.7+/-5.2 nmol/min/mg protein). Intracellular semidehydroascorbate ac tivity was present only in SK-N-BE(2) cells (4.7+/-1.2 nmol/min/mg pro tein). Extracellular ascorbate was regenerated by semidehydroascorbate membrane activity, the activity of SK-N-BE(2) being twice that of SK- N-SH cells. The present data may explain the ability of the tumor to p rogress or regress through mechanisms involving both myc oncogene and apoptosis.