N-acetylcysteine chemoprotection without decreased cisplatin antitumor efficacy in pediatric tumor models

Decreasing oxidative damage with the antioxidant agent N-acetylcysteine (NAC) can block the side effects of chemotherapy, but may diminish anti-tumor efficacy. We tested the potential for interactions of high dose NAC against a minimally effective cisplatin chemotherapy regimen in rat models of human pediatric cancers. Athymic rats received subcutaneous implantation of human SK-N-AS neuroblastoma cells or intra-cerebellar implantation of human D283-MED medulloblastoma cells. Rats were untreated or treated with cisplatin (3 or 4 mg/kg IV) with or without NAC (1,000 mg/kg IV) 30 min before or 4 h after cisplatin treatment. Blood urea nitrogen (BUN) and tumor volumes were measured. Cisplatin decreased the growth of SK-N-AS neuroblastoma subcutaneous tumors from 17.7 +/- A 4.9 to 6.4 +/- A 2.5 fold over baseline 2 weeks after treatment (P < 0.001). Pretreatment with NAC decreased cisplatin efficacy, while 4 h delayed NAC did not significantly affect cisplatin anti-tumor effects (relative tumor volume 6.8 +/- A 2.0 fold baseline, P < 0.001). In D283-MED medulloblastoma brain tumors, cisplatin decreased final tumor volume to 3.9 +/- A 2.3 mm(3) compared to untreated tumor volume of 45.9 +/- A 38.7 (P = 0.008). Delayed NAC did not significantly alter cisplatin efficacy (tumor volume 6.8 +/- A 8.1 mm(3), P = 0.014 versus control). Cisplatin was minimally nephrotoxic in these models. NAC decreased cisplatin-induced elevations in BUN (P < 0.02). NAC chemoprotection did not alter cisplatin therapy, if delayed until 4 h after chemotherapy. These data support a Phase I/II clinical trial of delayed NAC to reduce ototoxicity in children with localized pediatric cancers.