Abraham Goldin

Current results of the screening program at the division of cancer treatment, national cancer institute

Abstract The prospective screening program at the Division of Cancer Treatment, National Cancer Institute, has now been in operation for several years and is making steady progress in the identification of new synthetic compounds and natural products of potential interest for the clinic. Data are presented on four categories of drugs that have been tested in the new screening panel: (a) clinically established antitumor agents; (b) new drugs and drugs for which there is renewed clinical interest based on activity in the new screen and previously inadequate clinical trial; (c) drugs in the initial phases of clinical trial; (d) compounds in development. An analysis of the data is presented, taking into account a series of important questions that are being addressed prospectively to the new screen. Although the ability to provide definitive answers must await feedback from clinical testing of compounds recommended by the screen, some generalizations appear to be emerging, and these are discussed. A comparison is made of the activity of drugs in the treatment of human tumors growing in two sites, subcutaneously and under the renal capsule. The subrenal capsule model appears to be somewhat more sensitive to drugs than the subcutaneous model and may provide certain advantages for initial panel testing. Attention is drawn to the potential usefulness in a screening program of the newly developed clonogenic techniques for growing human tumors. The screening program at the Division of Cancer Treatment is viewed as a dynamic entity, subject to modification in accordance with acquired experience.

Chemotherapy of human colon cancer xenografts in athymic nude mice

The lack of effective chemotherapy in advanced colon cancer and difficulties in evaluating response in clinical trials indicate a need for experimental models to screen new agents for activity against this specific type of cancer. Xenografts of human colon cancer in nude mice reproduce many features of the original tumor specimen and could be expected to predict drug response for colon cancer with more specificity than previously used screens. NIH‐Swiss nude mice bearing subcutaneous (s.c.) trocar implants of tumor tissue were used in these studies. Three serially transplantable lines of human colon cancer (designated “HT”, “CA”, and “BE”), which range in their degree of differentiation from well‐differentiated adenocarcinoma to undifferentiated carcinoma, were used for drug testing. Treatment was delayed until tumors had reached 60‐600 mg in mass to correspond to advanced tumors in patients. Drugs being developed for clinical trial by NCI were selected for testing against the xenografts based on promising activity against transplantable murine tumor lines and difference in mechanism of action. Two antimetabolites, PALA and Bakers antifol, a mitotic spindle poison, maytansine, and a DNA intercalating agent, AMSA, produced no significant regression in any of the three colon xenograft lines. From the group of the nitrosoureas, methylCCNU and chlorozotocin were tested. MethylCCNU caused no regression of line HT, a transient response of line CA and complete regressions of line BE. Chlorozotocin also caused regression of line BE but had no effect on the other tumor lines. The results of chemotherapy studies with human colon cancer xenografts in nude mice reflect the clinical situation where few objective responses are achieved with presently available chemotherapy. We would conclude from these studies that information about activity against colon cancer of a new drug may be gained by testing the drug against a panel of human colon cancer xenografts. Careful clinical followup studies and parallel studies with xenograft systems should establish the correlation between individual clinical response and response in the xenograft system.

Eradication Of Leukaemic Cells (L1210) by Methotrexate and Methotrexate Plus Citrovorum Factor

Eradication Of Leukaemic Cells (L1210) by Methotrexate and Methotrexate Plus Citrovorum Factor

The effect of reduced derivatives of folic acid on toxicity and antileukemic effect of methotrexate in mice

Abstract Mice inoculated with leukemia L1210 were treated with combinations of methotrexate (amethopterin) and one of the following folic acid derivatives: (a) folic acid, (b) dihydrofolic acid, (c) tetrahydrofolic acid, (d) 10-formyltetrahydrofolic acid, (e) 5-formyltetrahydrofolic acid (citrovorum factor), and (f) prefolic A (5-methyltetrahydrofolic acid). Daily treatment was started 3 days after leukemic inoculation. Treatment with methotrexate (MTX) alone, or in combination with folic acid, resulted in a considerable prolongation of lifetime. All other treatments resulted in leukemic death of the animals at the same time as the untreated controls; i.e. the antileukemic effect of methotrexate was blocked by the metabolite. Delayed administration of ctirovorum factor and prefolic A, after large doses of MTX, showed that both compounds were effective in reducing toxicity but had little or no effect on the antileukemic activity when given 12 to 24 hr after MTX. At 48 hr after administration of MTX neither compound protected against the toxicity of the drug. In view of the extreme sensitivity of dihydrofolic reductase to inhibition by MTX in vitro , it was of particular interest that dihydrofolic acid was able to bring about extensive reversal of the antileukemic effect and toxicity of this substance. A study of folic and dihydrofolic reductase activity in the livers of mice which had received combinations of MTX and folic acid derivatives showed that there was no difference in the extent of inhibition, regardless of whether the combination was toxic or nontoxic to the animals.

Effects of cyclophosphamide and adriamycin on the healing of surgical wounds in mice

Administration of therapeutic dose levels of cyclophosphamide as a single dose or as daily treatments for 5 days during the perisurgical period resulted in a significant decrease in the strength of surgical skin wounds in mice as measured 21 days after surgery. Administration of a single dose of 200 mg/kg either at the time of surgery or up to 4 days prior to or after surgery impaired 21‐day wound strength, with the most extensive depression observed when the drug was given 1 or 2 days after surgery. Earlier stages of wound healing (day 3 or day 7) were not as sensitive to cyclophosphamide. Adriamycin in the therapeutic dosage range for mice did not significantly impair wound healing. This drug had an effect only at the LD10 dosage level. Combination treatment with cyclophosphamide plus adriamycin at the time of surgery impaired 21‐day wound strength to a greater degree than observed with either agent alone, but did not significantly depress wound strength 3 or 7 days after surgery. These studies indicate that dosage level, the time of drug administration relative to surgery, and the time at which wound strength measurements are made are important parameters in determination of the effects of antineoplastic agents on wound healing.

Impaired growth of a radiation-induced lymphoma in intact or lethally irradiated allogeneic athymic (nude) mice.

Radioinduced lymphomas were maintained in mice by serial transplantation of neoplastic cells and mortality of mice was recorded for 60 days. Mice were x- irradiated at a dose rate of 137 R/min. Lethally irradiated mice were resistant to an incompatible lymphoma as determined by 125I-IUdR uptake values of the spleen. The lack of influence of an immunodepressive factor and the observation that lethal irradiation did not abrogate the relative resistance to tumor challenge appeared to exclude the possibility that the reduced growth of the lymphoma in nude mice is the result of a conventional allograft reaction.

The effectiveness of the anthracycline analog 4'-epidoxorubicin in the treatment of experimental tumors: a review

SummaryThe current report presents the data of the Division of Cancer Treatment of the National Cancer Institute (NCI) on the antitumor activity of the anthracycline antibiotic 4′-epidoxorubicin in experimental tumor systems. Direct comparisons are made with doxorubicin in individual experiments, and the data are related to those of earlier studies in the form of a review of experimental activity, in order to assess the relative activity of 4′-epidoxorubicin and doxorubicin. The experimental test models utilized by the NCI for these studies included the leukemias P388 and L1210, B-16 melanoma, Lewis lung carcinoma, the colon tumors 26 and 38, and the mammary tumors CD8F1 and C3H16/C. The human tumors growing in xenograft in athymic mice included the models LX-1 lung tumor, CX-1 colon tumor, and MX-1 mammary tumor. Additional comparisons were made with the tumor models Gross leukemia, sarcoma 180, MSV-induced sarcoma, MS-2 tumor, and a variety of human tumors growing in athymic mice, as well as with in vivo toxicologic and in vitro cytotoxicity models. Although for 4′-epidoxorubicin there is only a minimal alteration of the configuration of the doxorubicin molecule, quantitative comparison of 4′-epidoxorubicin and doxorubicin revealed not only similarities but also differences in biological activity. Both drugs showed activity against a broad spectrum of experimental tumors, with 4′-epidoxorubicin more effective against some tumors and equally effective against others. 4′-Epidoxorubicin evidenced less toxicity than doxorubicin in both acute and chronic toxicity studies with retention of therapeutic effectiveness and showed reduced cardiotoxicity. With 4′ -epidoxorubicin there resulted a higher therapeutic index and therapeutic ratio, permitting the use of higher dosage and a greater margin of safety. The preclinical differences in therapeutic and toxicologic manifestations of 4′-epidoxorubicin, reflecting apparent alterations in pharmacologic properties and mode of action in comparison with doxorubicin, support the broad spectrum clinical trials of this already-demonstrated clinically active drug.

Drug Induced Modulation of Immune Responses in Mice: Effects of 5-(3,3-Dimethyl-1-Triazeno)-Imidazole-4-Carboxamide (DTIC) and Cyclophosphayide (CY)

Graded doses of Cyclophosphamide (Cy) or 5-(3,3-dimethyl-1-triazeno)-imidazole-4-carboxamide (DTIC) were given to CD2F1 or C57Bl/6 mice. One, 45 or 60 days later the animals were tested for allograft responses, competence of producing cytotoxic lymphocytes in vitro and lethal graft-versus-host disease (GVHD) in vivo, delayed-type hypersensitivity (DTH) and humoral antibody responses against sheep red blood cells (SRBC). Both agents produced strong inhibitory effects, except for DTH, when given 1 day before the antigenic stimulus. However immunodepression lasted for at least 60 days after DTIC, whereas relatively rapid recovery of immune responsiveness was detected in mice treated with Cy. When Cy or DTIC were given to allogeneic donor mice 1 day before spleen cell transfer, immunodepressed recipients did not undergo GVHD. However when drugs were administered to recipient mice inoculated with allogeneic spleen cells, lethal GVHD occurred when Cy but not DTIC was given to the hosts. DTH responses were potentiated by Cy when the drug was given 1 day before sensitization. In contrast hypersensitivity reactions were not affected by DTIC treatment. It was concluded that DTIC is a potent and long-lasting immunodepressive agent, capable of affecting various T-cell subpopulations and possibly B lymphocytes in mice. Since the drug inhibits immune response when given before the antigenic stimulation, it was suggested that DTIC acts through a mechanism similar to that of alkylating non phase-specific agents.

Combined effects of antineoplastic agents and anti-lymphoma allograft reactions

Abstract Combined effects of chemotherapy and anti-lymphoma allograft responses were studied in mice inoculated intraperitoneally (i.p.) with leukemia cells incompatible for multiple minor histocompatibility loci (MMHL) and treated with graded doses of 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU), vincristine (VCR), cyclophosphamide (Cy), 5-(3,3-dimethly-1-triazeno)-imidazole-4-carboxamide (DTIC) or hexamethyl-melamine (HMM). The results showed that: (a) no appreciable difference in survival times was found, as a rule, in leukemic compatible or allogeneic mice not subjected to drug treatment; (b) both BCNU and Cy markedly prolonged the survival times of compatible leukemic mice, but only treatment with BCNU resulted in chemo-immune collaborative activity when the drug was administered to allogeneic hosts; (c) DTIC was moderately active in compatible mice and no additive or synergistic effects were found in allogeneic hosts; (d) VCR, little or no effect in prolonging the survival times of leukemic compatible mice, proved to be highly efficient when given to allogeneic recipients; (e) HMM was totally ineffective in prolonging the survival time of either compatible or allogeneic mice. These studies evidenced that no obvious relationship could be found between the anti-leukemic activity of different drugs and their antineoplastic effectiveness when combined with antitumor immune responses.

18F-5-fluorouridine, A New Probe For Measuring The Proliferation Of Tissue in vivo☆

(1) Increased metabolic trapping of labeled fluorouridine reflects the interaction of three parameters in rapidly proliferating tissues: increased rates of intracellular phosphorylation, increased rates of transport, and increased rates of synthesis of RNA. (2) We have taken advantage of these metabolic phenomena, demonstrating in this paper that the uptake of 18F-5-fluorouridine, a positron-emitting radiopharmaceutical, can provide a very practical means for measuring changes in proliferative states of tissues in vivo. (3) Two major changes in proliferative states have been examined: one involves changes in growth of normal mouse tissues induced by pharmacological agents; the other involves tumor growth and neoplastic infiltration in mice and rabbits. (4) We describe tracer experiments with 18F-5-fluorouridylate, prepared by enzymatic means, and with 18F-5-fluorouridine, prepared by both enzymatic means and direct radiochemical procedures. (5) Uptakes of 18F after a pulse of 18F-5-fluorouridine were increased in mouse spleen following phenylhydrazine treatment to induce increased splenic erythropoiesis. (6) Uptakes of 18F in various mouse tissues were decreased following pretreatment with actinomycin D. This finding is consistent with the known inhibitory action of actinomycin on RNA synthesis. (7) Intracerebral Zimmerman ependymoblastoma tumors showed extraordinarily high uptakes of fluorine-18 in mice injected intravenously with 18F-5-fluorouridylate or with 18F-5-fluorouridine in contrast to very low uptakes by normal brain tissue. (8) After intracerebral injection of mice with suspensions of L1210 leukemia cells, distant organs such as lung, liver, and spleen became involved. These tissues showed significant increases of radioactivity after pulse labeling with 18F-5-fluorouridylate consistent with histological evidence for infiltration of these tissues by neoplastic cells. (9) Intramuscular VX2 carcinoma tumors in rabbits showed localized uptakes of 18F significantly higher than surrounding normal muscle tissue. (10) The most important clinical implication of the present work is the promise that 18F-5-fluorouridine uptakes can be followed in humans by positron emission tomography. This would provide a direct means of measuring different rates of in vivo proliferation in neoplasms, hematologic tissues and other organs undergoing rapid growth changes.