This report indicates that not only does the preoperative administration of cyclophosphamide or radiation prevent the kinetic changes observed in a distant tumor focus following tumor removal but that the preoperative administration of the antiestrogen tamoxifen and the luteinizing hormone-releasing hormone analogue Zoladex are equally effective in that regard. It also provides evidence indicating that serum obtained from mice treated with those therapies when transferred to a recipient bearing a tumor of a similar type to that in the donor fails to stimulate DNA synthesis in the tumor of the recipient. In contrast, an increase in labeling index occurs following transfer of serum obtained following tumor removal from untreated mice. Moreover, when tumor-bearing mice were treated by each of the four modalities prior to receiving serum obtained from untreated donors following removal of a tumor, no kinetic changes were observed in the tumor of the serum recipient.
This investigation was supported in part by USPHS Grant RO1-CA-14972 awarded by the National Cancer Institute, Department of Health and Human Services.