Combined actions of 5-fluorouracil and 1-(2-chloroethyl)-3-(4-methylcyclohexyl)-1-nitrosourea on human colonic carcinoma cells in vitro

Two lines of human colonic carcinoma cells have different sensitivities to 5-fluorouracil and 1-(2-chlorethyl)-3-(4-methylcyclohexyl)-1-nitrosourea (methyl-CCNU). The growth of the BE line is 50% inhibited by 330 microM 5-fluorouracil and 15 microM methyl-CCNU, and the HT-29 line is 50% inhibited by 85 and 140 microM, respectively. On cloning, 50% of BE cells are killed by 500 microM 5-fluorouracil and 6 microM methyl-CCNU, and the HT-29 cells are killed by 250 and 120 microM respectively. When the drugs were combined, there were additive effects which occurred in cell growth of both lines and killing of BE cells. Synergism occurred in killing HT-29 cells when a low concentration of 5-fluorouracil was combined with methyl-CCNU. The synergism did not increase with increasing concentrations of 5-fluorouracil. Both drugs caused growth delay of spheroids (HT-29 cells), an effect that was additive when the drugs were combined. Growth inhibition of both lines in monolayer culture by 5-fluorouracil was more sensitive than was cell killing or inhibition of spheroid growth but, with methyl-CCNU, killing of BE cells was more sensitive than was growth inhibition. HT-29 cells showed similar sensitivity to methyl-CCNU in all three systems. The type and sensitivity of drug effect seen in vitro depends on the particular drug used, the cell line tested, and the parameter measured.

Current management of advanced and locally unresectable gastric carcinoma

Gastric cancer is the most chemotherapy-responsive adenocarcinoma of the major gastrointestinal sites. For patients with advanced disease, the response rates and survival achieved with recently designed Adriamycin-based regimens represent an improvement over the past use of 5-fluourouracil alone or combined with a chloroethylnitrosourea. Effective palliative treatment can be administered in an out-patient setting without the necessity of producing severe or life-threatening toxicity. Nevertheless, response durations are finite, as is patient survival. It is essential that Phase II trials of new drugs be continued in an attempt to identify agents with greater therapeutic activity for this disease. For the locally unresectable stage, combined modality therapy incorporating palliative resection of the primary tumor, regional radiation therapy and chemotherapy, has provided long-term disease-free survival for 15--25% of all patients. The most promising aspect of current clinical investigation is the application of the Adriamycin-based drug combinations in controlled trials of surgical adjuvant therapy.

Use of the agar diffusion chamber for the exposure of human tumor cells to drugs

Human melanoma xenografts in immune-deprived mice have been used to assess the value of the agar diffusion chamber for chemosensitivity testing. Tumor cells were treated with melphalan, Adriamycin, or methyl trans-1-(2-chloroethyl)-3-(4-methylcyclohexyl)-1-nitrosourea either as solid tumors growing in mice or as suspensions in agar in i.p. diffusion chambers. Survival of clonogenic human tumor cells was measured by the agar diffusion chamber assay in both cases. Cell survival curves were log-linear for treatment of tumor cells in vivo or in the chambers. For melphalan the slopes of survival curves were significantly greater for treatment in the chambers than as solid tumors in vivo, but for methyl trans-1-(2-chloroethyl(-3-(4-methylcyclohexyl)-1-nitrosourea or Adriamycin, they were indistinguishable. Experiments with [14C]melphalan showed that the levels of drug achieved were less inside the diffusion chambers than in the tumors in vivo so that the sensitivity of tumor cells to melphalan was much greater when they were treated in chambers. The differences in drug exposure and in cellular chemosensitivity between chambers and tumors suggest caution in the interpretation of drug testing using this system, but the log-linear nature of the dose-response curves is an important feature which may be useful in the eventual development of optimal chemosensitivity testing systems.

[Enhancement of MeCCNU potency (chemosensitization) by misonidazole in a human melanoma xenograft system]

In addition to the well-known radiosensitizing properties of misonidazole its potential for chemosensitization has been investigated recently. According to results obtained mostly with conventional murine tumor systems, the degree of such chemosensitization depends on the particular tumor system, the type of antineoplastic agent and the dose of misonidazole employed. Our experiments were conducted with a human melanoma transplanted onto (nu/nu) mice. At the dose level of 1 g/kg misonidazole toxicity was enhanced by a factor of about 3, whereas antineoplastic activity was enhanced only by a factor of about 1.8. Therefore, the usefulness of such chemosensitization remains limited, especially since under clinical circumstances this dose of misonidazole would cause unacceptable neurotoxicity. The retention of radiotivity from 14C-MeCCNU is increased in neoplastic as well as in normal tissues by a factor of 1.3.DNA interstrand crosslinks measured 24 hours after drug exposure, however, are increased by a factor of about 2. Despite their nonselective reaction at the level of molecular pharmacology, drugs with sensitizing or protective properties may well constitute a valuable addition to the serial synthesis of chemical congeners in drug development. The use of oxazaphosphorines is quoted as an example where selective protection from urotoxicity is afforded by sodium-2-mercaptoethanesulfonate.

Clinical and chemotherapeutic study of hepatocellular carcinoma in Malaysia: a comparison with African and American patients

Twenty Malaysian patients with unresectable primary liver cell cancer were prospectively studied at the General Hospital, Kuala Lampur, and were compared for clinical features with an equal number each of African and American patients being studied by the Eastern Cooperative Oncology Group. The patients received intravenous 5-FU and oral MeCCNU which was used for the first time in an Asian country. Most of the Malaysian patients were Chinese, belonged to younger age groups, and presented with massive hepatomegaly, jaundice, and fever. Toxicity to MeCCNU invariably occurred in the form of leukopenia or thrombocytopenia, but none life threatening. Partial response was seen in 20% of Malaysians as compared to 16% in Americans and none in Africans. Malaysians achieved a median survival of 16 weeks compared to 28 weeks in Americans and only eight weeks in Africans. Malaysian Chinese patients were all HBc Ab + ve. Other factors which may have played an etiologic role in the induction of primary liver cancer included alcohol, Chinese herbal medicines, aflatoxin and habitual use of medicated rubbing oils.

[Cancer chemotherapy with special reference to pharmacokinetics of nitrosoureas]

This paper provides an overview of cancer chemotherapy with special reference to the pharmacokinetics of the nitrosoureas. At physiological PH, the chloroethylnitrosoureas can be decomposed into an isocyanate and 2-chloroethyl diazene hydroxide. Therefore, it is clear that they have both alkylation and carbamoylation actions. In addition to the spontaneous chemical dissociation, the nitrosoureas can be metabolized by liver microsomal enzymes to more polar hydroxylated products, and certain nitrosoureas can be denitrosated by these enzymes to the parent urea. Since the lipid-soluble nitrosoureas and some of the water-soluble nitrosoureas such as ACNU and MCNU demonstrated to cross the blood-brain barrier, they have been used in the treatment of primary brain tumors and tumors and tumors of metastatic origin. It has been demonstrated from the results of our study and other reports that the alkylation of DNA by ACNU progresses more slowly as compared with that of other alkylating agents. This is an important finding in relation to the appearance of delayed myelosuppression of the nitrosoureas and in the design of dose schedules of these agents. The major clinical emphasis has been directed towards the more active chloroethylnitrosoureas with reduced myelosuppression, and attempts are now made for this purpose. Unfortunately, the results of phase I and II trials of the newly developed nitrosoureas suggest that these agents produce delayed and cumulative bone marrow toxicity. Antitumor activity of the nitrosoureas is frequestly observed in chronic myelocytic leukemia, malignant lymphoma, brain tumors and small cell carcinoma of the lung, and less frequently in gastrointestinal carcinoma, multiple myeloma and malignant melanoma. In order to enhance clinical effects of the nitrosoureas, further investigation of the design in therapeutic schedules on the basis of their pharmacokinetic characteristics will be needed.

[The combination methyl-CCNU, vincristine, 5-fluorouracil and streptozotocin in the treatment of advanced colo-rectal adenocarcinoma]

Sixteen patients with advanced colo-rectal cancer were treated with the combination methyl-CCNU, vincristin, 5-fluorouracil and streptozotocin (MOF-Strepto). Seven cases were previously untreated. A partial remission was observed only in one patient (6%, confidence limits to 95%: 1-17%). Marked gastrointestinal and hematologic toxicity was registered. Based on this experience the authors are unable to confirm other pilot studies claiming major antitumor activity for MOF-Strepto in the treatment of advanced colo-rectal cancer.

Phase II trial of methyl-CCNU, vincristine, 5-fluorouracil, and streptozotocin (MOF-Strep) in patients with disseminated pancreatic carcinoma

A phase II trial of methyl-CCNU, 5-fluorouracil (5-Fu), vincristine, and streptozotocin (MOF-Strep) was conducted on 20 patients with pancreatic carcinoma. There were two partial remissions (10%) lasting 3 and 10 months. In addition, there were two minor responses. The predominant toxicity was gastrointestinal, although hematologic and renal toxicity were also seen. Since the response rate to MOF-Strep does not appear to exceed that to 5-Fu alone, the usefulness of this combination in patients with pancreatic carcinoma is limited.

The oncostatic effect of methyl-CCNU on various experimental lymphoreticular neoplasms

Studies on the chemotherapeutic potential of methyl-CCNU on experimental leukemias were undertaken. A number of murine transplantable in vivo lines (chemical carcinogen-induced T and B leukemias; radiation- and viral-induced T leukemias of C57BL/6, C3H/eb and SJL/J origin; radiation-induced myeloid leukemias and spontaneous reticulum cell neoplasms of SJL/J mine) were used in these studies. The optimal dose of methyl-CCNU and optimal timing of administration were extensively investigated on two sample lines of T cell leukemias of C57BL/6 mice. Leukemic cell eradication could be achieved in almost all of the different leukemias treated, irrespective of whether induction was brought about by chemical or physical means or due to a viral leukemogenic agent. Studies undertaken to elucidate the effect of methyl-CCNU on the establishment of preleukemic cells following induction of leukemia by the radiation leukemia virus (RadLV) or by total body irradiation, indicated the oncostatic effect of methyl-CCNU on early preleukemic cells.

Adjuvant chemotherapy in colon and gastric cancer

The adjuvant chemotherapy of colorectal and gastric cancer is being actively investigated. Studies of both single antineoplastic agents and combinations of several drugs have been used. In colorectal cancer, single-agent therapy has not resulted in improved survival. Combination chemotherapy studies are at too early a stage to be evaluated. In gastric cancer, single-agent chemotherapy has not been effective as adjunctive treatment to surgery. Combinations of active agents in gastric cancer hold promise as effective surgical adjuvant therapy.

Response of metastatic cloacogenic carcinoma to treatment with semustine

A case of cloacogenic carcinoma of the anorectal junction with pulmonary metastases is presented. Treatment with Semustine (Methyl-CCNU) resulted in a partial response lasting 15 months. Cloacogenic carcinoma is an uncommon neoplasm against which only a few chemotherapeutic agents have been tried. Semustine should be considered in the treatment of metastatic cloacogenic carcinoma.

Nephrotoxicity of semustine (methyl-CCNU) in patients with malignant melanoma receiving adjuvant chemotherapy

The nephrotoxicity of semustine (methyl-CCNU) has been studied in 45 adult patients with surgically resected Stage I or II malignant melanoma who received this drug as adjuvant chemotherapy. Abnormalities of renal function (including three cases of renal failure) were noted in seven of 45 patients (16 percent); all these patients received more than 1,400 mg/m2. This represents an incidence of 26 percent in patients receiving more than 1,400 mg/m2 of semustine. Two distinct patterns emerged. Abnormal serum creatinine levels developed in two patients while receiving semustine and later progressed to renal failure. Five patients had normal serum creatinine levels throughout their treatment courses but had abnormal creatinine values one month to two years following the completion of drug therapy. Renal failure developed in one of these patients, but the remaining four have had stable renal function for one to two years of additional follow-up. No clinical signs of renal insufficiency were detected in any patients receiving less than 1,400 mg/m2 of semustine. No changes unequivocally attributable to semustine were seen in eight patients at autopsy despite the fact that three had received greater than 1,900 mg/m2 of nitrosourea. This incidence of nephrotoxicity appears to be significantly lower than that previously reported in children. Guidelines for future therapy with semustine are described.

[Immunochemotherapeutic treatment of gastrointestinal neoplasms]

The results obtained with a three-fold association of drugs (VCR, 5Fu, MeCCNU) in the treatment of 68 patients suffering from advanced carcinoma of the gastroenteric system followed up over an approximately four year period at the Savona Oncology Centre are reported. The percentage of positive responses (CR + PR) was 75% for carcinoma of the colon-rectum and 44.4% for stomach cancer. The results obtained in intestinal carcinoma proved more satisfactory than those reported in the literature. This could be attributed to the contemporaneous use of Corynebacterium parvum which boosts the immunitary state and so enhances the defences of the host organism, making it more sensitive to polychemotherapy. In the light of this hypothesis, stress is laid on the need to use an immunochemotherapy approach for the treatment of advanced carcinoma of the gastroenteric apparatus.

Erythrocyte osmotic fragility in patients receiving hyperthermia with and without chemotherapy

The osmotic fragility of erythrocytes was studied in 24 patients receiving whole-body hyperthermia, with and without concomitant chemotherapy, for 2-4 hours as an adjuvant to chemotherapy for advanced metastatic disease. No alteration in osmotic fragility of erythrocytes was observed with whole-body hyperthermia.