The effect of heroin on tumor growth and survival time was studied in mice with neuroblastoma. Daily SC injections of either 3, 6, 10, or 15 mg/kg heroin were initiated either 2 weeks prior to tumor cell inoculations (pre-treated groups) of 106 S20Y cells or one week after tumor transplantation (post-treated groups); control animals received saline injections prior to tumor cell inoculation (saline-tumor group). Heroin administration that began prior to tumor cell inoculation was effective in inhibiting tumor growth and prolonging life-span at all dosages utilized, but a dose-related response was not observed. A prolongation in mean survival time of 32-39% and median survival time of 8-50% was found in tumor-bearing animals of the pre-treated groups in comparison to mice in the saline-tumor group. Tumor growth was retarded in mice pre-treated with heroin, but mean tumor size of these animals was comparable to controls on the day of death. Only one post-treated group, 6 mg/kg, was observed to have alterations in tumor growth and survival time. Heroin's action in retarding tumor growth and prolonging life-span was blocked by concomitant administration of an opiate antagonist (naloxone, 10 mg/kg). These results suggest that, in addition to heroin's analgesic and behavioral properties, this opiate may have an even greater biologic significance by modulating neoplasia.
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