Cyclophosphamide delays 3-methylcholanthrene sarcoma induction in mice

Abstract

THERE is increasing evidence to show that suppressor T lymphocytes facilitate the growth of neoplasms that have tumour-specific transplantation antigens^1–6. Studies on suppressor cell activity with respect to various non-tumour antigens have shown that treatment of mice with cyclo-phosphamide depresses suppressor cell-mediated mechanisms to a greater extent than the effector arm of the immune response^7–9, provided the proper dose and timing for drug administration was used. Based on these observations we speculated that treatment of mice with Cyclophosphamide during the latency period of tumour induction might prevent (or at least delay) the appearance of primary tumours. We show here that this hypothesis is correct. In BALB/c mice given 3-methylcholanthrene (MCA) and injected with cyclophosphamide (2 mg per mouse) every 10 days, the appearance of primary sarcomas was delayed. Because the effects were striking, and were obtained with one of the drugs most commonly used in cancer chemotherapy, we decided to report the data. We are, however, aware that explanations for the drug effect other than interference with suppressor cell activity are equally possible, including a direct effect of the drug on tumour cells.