Synergistic cytotoxicity between dimethyl sulfoxide and antineoplastic agents against ovarian cancer in vitro.

Dimethyl sulfoxide is a well-known differentiating agent that has been shown to inhibit tumor growth in vitro. We hypothesized that antineoplastic agents might show synergistic cytotoxicity when combined with 10% dimethyl sulfoxide. Twenty-four malignant ovarian tumors were removed and used in tests to determine the cytotoxicities of 10% dimethyl sulfoxide alone, each of six antineoplastic agents alone, and 10% dimethyl sulfoxide plus each antineoplastic agent. Cytotoxicity results for 10% dimethyl sulfoxide alone and each antineoplastic agent alone were used to evaluate each combination of dimethyl sulfoxide and an antineoplastic agent for synergy. There were 14 synergistic responses that were statistically significant at the p less than 0.01 confidence level between 10% dimethyl sulfoxide and an antineoplastic agent against the ovarian tumors. Seven of these responses were significant at the p less than 0.0003 level. This is strong evidence that true synergistic cytotoxicity occurs when an antineoplastic agent is combined with 10% dimethyl sulfoxide. We conclude that intraperitoneal delivery of antineoplastic agents in 10% dimethyl sulfoxide may be useful in the treatment of certain ovarian cancers.