Sensitivity of human ovarian carcinoma cells to interferon and other antitumor agents as assessed by an in vitro semi-solid agar technique.

To determine the sensitivity in vitro of human ovarian carcinoma cells to the antiproliferative effects of human leukocyte interferon, 18 samples of ascitic fluid from 15 affected patients were cultured in semi-solid agar by the technique of Hamburger and Salmon. Cultures were examined at weekly intervals after initiation and the number and size of each tumor colony recorded. Growth as defined by increase in total tumor colony number with time was obtained in 45% of the samples, or 53% of the patients, or 67% of the ascitic fluid samples with tumor cells demonstrated by Pap smear. No growth occurred in samples from recently treated patients or in samples devoid of tumor cells as assessed by Pap smear. Response to interferon directly incorporated into the agar culture system or preincubated with cells prior to their inclusion in culture was defined as reduction in total colony number by greater than or equal to 50% and partial response by greater than or equal to 25% reduction. The response rate for samples, The nontreated controls of which showed evidence of growth, was 71%, and that of samples that contained tumor colonies with no increase in growth during the culture period was 75%. Sensitivity to interferon was not related to the histology or grade of the tumor or to the stage of the disease. In general the responsiveness of the tumor cells to interferon ran parallel to the overall responsiveness to a variety of other chemotherapeutic agents. As this culture system has been proven by other investigators to be predictive of in vivo resistance to antitumor drugs with considerable accuracy and also to be predictive of in vivo response to a lesser degree, it will be important to determine whether similar relationships between in vitro and in vivo sensitivity obtain for interferon.