Barbara Forseth

Alteration of EGF-receptor binding in human breast cancer cells by antineoplastic agents

Polypeptide growth factors bind to membrane receptors on human breast cancer cells and stimulate cell proliferation, suggesting that they may be important in growth regulation. Inhibition of the stimulatory effects of these factors might result in antineoplastic activity. Since cytotoxic drugs have been shown to alter cell membrane characteristics, we have examined the effects of a variety of antitumor drugs on the binding of epidermal growth factor (EGF) to the membrane receptor of human breast cancer cells. Twenty-four standard or investigational cytotoxic drugs were screened at a concentration of one-tenth the achievable peak plasma level for their ability to inhibit binding of 125I-EGF to its receptor in MCF-7 human breast cancer cells. Although at this concentration statistically significant inhibition of binding was observed with 11 drugs, the maximum inhibition observed was only 27%. Five agents, representing classes of drugs with different modes of action, were then studied in more detail. Of these, preincubation with 5-fluorouracil, 4-hydroperoxy-cylophosphamide and doxorubicin inhibited MCF-7 colony formation in a dose-dependent manner, but these drugs had no effect on EGF-binding even at a concentration of 10 times the peak plasma level. Preincubation of cells with vinblastine and cisplatin, however, resulted in both reduced colony survival and a parallel reduction in EGF receptor binding. Membrane integrity, as measured by trypan blue exclusion, was not altered. Scatchard analysis of EGF binding demonstrated that the major effect of cisplatin was a reduction in binding affinity. We conclude that cisplatin and vinblastine at high concentrations can inhibit the binding of EGF to human breast cancer cells offering an additional possible mechanism for their antiproliferative activity.

Direct cloning of human malignant melanoma in soft agar culture

An in vitro soft agar technique was used to culture human malignant melanoma cells from 61 solid tumors, 17 lymph nodes, 11 effusions, and four bone marrow specimens from 93 patients with malignant melanoma. Colonies grew in soft agar from 64 (69%) of the 93 specimens. Fifty‐five percent of the specimens cultured formed

Activity of 9-10 Anthracenedicarboxaldehyde bis((4,5-dihydro-1 H-imidazol-2-yl)hydrazone)dihydrochloride (CL216,942) in a Human Tumor Cloning System

30 colonies per 500,000 nucleated cells plated. Light microscopy, electron microscopy, tumor marker, and athymic nude mouse studies provided evidence the colonies were composed of malignant melanoma cells. Drug sensitivity studies utilizing the cloning technique showed similarities between in vitro results and the general clinical experience noted with the same drugs. The human tumor cloning system represents a new model for future basic biology and clinical studies of human malignant melanoma.

Elimination of extrachromosomally amplified MYC genes from human tumor cells reduces their tumorigenicity.

SummaryWe have utilized a recently developed human tumor cloning system to screen for antitumor effects in vitro of a new anthracene derivative, CL216,942. The object was to determine whether the system is useful for pinpointing the types of tumors in patients which should be studied in early phase II clinical trials. Tumors from 684 patients were placed in culture (27 different histologic tumor types). Two hundred seventy-three tumors both grew and formed enough colonies for drug sensitivity assays. In vitro antitumor activity was noted for CL216,942 against human breast cancer, ovarian cancer, renal cancer, squamous cell, small cell and large cell lung cancer, lymphoma, acute myelogenous leukemia, melanoma, adenocarcinoma of unknown origin, adrenal cancer, gastric cancer, pancreatic cancer, and head and neck cancer. The drug definitely showed no in vitro activity against colon cancer. These date indicate that CL216,942 has a wide spectrum of in vitro antitumor activity. A comparison of these in vitro results with the results of phase II clinical trials with the drug should allow an evaluation of the utility of the human cloning system for predicting clinical activity of a new compound.