The authors studied the effect of two modified steroids containing different proportions (%) of alkylating agents alone or in combination on sister chromatid exchange (SCE) rates and on human lymphocyte proliferation kinetics. The antitumor activity of these compounds was tested on leukemia P388- and leukemia L1210-bearing mice. The two chemicals in mixtures enhance SCE induction and antitumor activity in a synergistic manner. The homo-aza-steroidal ester of p-bis(2-chloroethyl)aminophenyl acetic acid was found to be more effective than the homo-aza-steroidal ester of o-bis(2-chloroethyl)aminobenzoic acid in causing cytogenetic damage and antineoplastic activity. A correlation was observed between the magnitude of the SCE response and the depression of the cell proliferation index. The order of the antitumor effectiveness of the five different treatments tested coincided with the order of the cytogenetic effects they induced.

Combination chemotherapy is widely and routinely used for most cancer patients. The main objective of this study is an effort to develop new anticancer drugs and procedures with enhanced antitumor activity and reduced toxicity. This study was designed to determine the antileukemic and cytogenetic activity of five mixtures of three specific steroidal esters of aromatic nitrogen mustards in different proportions. This is the next step of two previous studies where the combination of two such esteric analogues was investigated with promising results. All of the five mixtures used proved active against leukemia P388 and in the induction of sister chromatid exchanges, indicating that the combination of the same class of compounds can be successful, especially when a highly potent agent is combined with another less active but probably mechanistically supplementary one. These results can be used in future experiments in order to further scout the specific role of the steroidal part of these molecules in the antileukemic potency of them.

Enhanced sister chromatid exchange (SCE) frequency by either melphalan (Mel) or epirubicin (Epir) was observed when human lymphocytes were exposed in vitro to 9-nitro-20(S)-camptothecin (9NC). A correlation was observed between the magnitude of the SCE response and the depression of the cell proliferation index. The antitumor activity of Mel and of 9NC was tested on leukemia P-388-bearing mice. The two chemicals in combination enhance antitumor activity in a synergistic manner. Therefore, the in vivo antitumor effect of Mel in conjunction with 9NC appears to correlate well with the in vitro synergistic effect on SCE induction caused by the combined Mel plus 9NC treatment. Teratogenesis Carcinog. Mutagen. 20:141-146, 2000.

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