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At least 19 recordsLinked to original sources
PubMed1976

Studies related to antitumor antibiotics. Part V. Reactions of mitomycin C with DNA examined by ethidium fluorescence assay.

The cytotoxic action of the antitumor antibiotic mitomycin C occurs primarily at the level of DNA. Using highly sensitive fluorescence assays which depend on the enhancement of ethidium fluorescence only when it intercalates duplex regions of DNA, three aspects of mitomycin C action on DNA have been studied: (a) cross-linking events, (b) alkylation without necessarily cross-linking, and (c) strand breakage. Cross-linking of DNA is determined by the return of fluorescence after a heat denaturation step at alkaline pH's. Under these conditions denatured DNA gives no fluorescence. The cross-linking was independently confirmed by S1-endonuclease (EC 3.1.4.-) digestion. At relatively high concentrations of mitomycin the suppression of ethidium fluorescence enhancement was shown not to be due to depurination but rather to alkylation, as a result of losses in potential intercalation sites. A linear relationship exists between binding ratio for mitomycin and loss of fluorescence. The proportional decrease in fluorescence with pH strongly suggests that the alkylation is due to the aziridine moiety of the antibiotic under these conditions. A parallel increase in the rate and overall efficiency of covalent cross-linking of DNA with lower pH suggests that the cross-linking event, to which the primary cytotoxic action has been linked, occurs sequentially with alkylation by aziridine and then by carbamate. Mitomycin C, reduced chemically, was shown to induce single strand cleavage as well as monoaklylation and covalent cross-linking in PM2 covalently closed circular DNA. The inhibition of this cleavage by superoxide dismutase (EC 1.15.1.1) and catalase (EC 1.11.1.6), and by free radical scavengers suggests that the degradation of DNA observed to accompany the cytotoxic action of mitomycin C is largely due to the free radical O2. In contrast to the behavior of the antibiotic streptonigrin, mitomycin C does not inactivate the protective enzymes superoxide dismutase or catalase. Lastly, mitomycin C is able to cross-link DNA in the absence of reduction at pH 4. This is consistent with the postulated cross-linking mechansims.

Animals↗
PubMed1978

The effect of mitomycin C on platelet aggregation and adenosine 3',5'-monophosphate metabolism.

The effect of Mitomycin C on aggregation, adenosine 3',5'-monophosphate (cyclic AMP) metabolism and reactions induced by thrombin was studied in rabbit platelets. Mitomycin C inhibited the platelet aggregation induced by adenosine diphosphate or thrombin. The level of radioactive cyclic AMP derived from 8-14C adenine or 8-14C adenosine increased after incubating intact platelets with Mitomycin C. Formation of radioactive adenosine triphosphate also increased though mitochondrial oxidation was not stimulated. Similar effect was observed also in rabbit liver. Mitomycin C failed to stimulate platelet adenyl cyclase but inhibited cyclic AMP phosphodiesterase in the absence of theophylline. In the platelets preincubated with Mitomycin C, thrombin-induced inhibition of adenyl cyclase, stimulation of membrane-bound cyclic AMP phosphodiesterase, and release of 250,000 dalton protein from platelet membranes were prevented. These results suggest that Mitomycin C will affect cellular membrane structure and function, and this extranuclear effect of Mitomycin C will lead to inhibition of aggregation in blood platelets.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed1979

5 FU infusion with mitomycin-C vs. 5 FU infusion with methyl-CCNU in the treatment of advanced upper gastrointestinal cancer: a Southwest Oncology Group Study.

A randomized trial was conducted by the Southwest Oncology Group (SWOG) in advanced carcinoma of the stomach and pancreas. Patients were assigned to receive monthly 5-fluorouracil 96-hour continuous infusions with either bolus mitomycin-C or oral methyl-CCNU. Mitomycin-C and methyl-CCNU were administered every eight weeks. The 5 FU-mitomycin combination produced a 14% and 22% response rate in disseminated stomach and pancreatic carcinoma, respectively. The combination of infusion 5 FU and methyl-CCNU achieved responses in 9% and 5% of stomach and pancreatic tumors, respectively. There was no significant difference in survival between limbs for either tumor. Median survival in gastric carcinoma on the 5 FU-mitomycin regimen was 25 weeks vs. 18 weeks on the 5 FU-METHYL-CCNU arm. In pancreatic carcinoma median survival on the mitomycin limb was 19 weeks as compared to 17 weeks on the methyl-CCNU program. Leukopenia was greater for the first course on the mitomycin limb. Regression analysis demonstrated that performance status was the most important pretreatment characteristic for predicting survival in both tumors. Neither 5 FU infusion combination appears to significantly alter the dismal prognosis of advanced upper gastrointestinal neoplasms.

Antineoplastic Agents↗
PubMed1978

5FU infusion with mitomycin-C versus 5 FU infusion with methyl-CCNU in the treatment of advanced colon cancer: a Southwest Oncology Group Study.

The Southwest Oncology Group (SWOG) in a randomized trial evaluated 5FU infusions in combination with either Mitomycin-C or Methyl-CCNU in patients with disseminated large bowel cancer. A response rate of 18% was noted on the 5FU-Mitomycin limb as compared to 16% on the Methyl-CCNU arm (p = .39). Median survival for all treated patients was 43 weeks on both arms. Myelosuppression was found to be more significant on the Mitomycin-C arm. Regression analysis demonstrated that performance status, sex, and primary site were significant pretreatment characteristics for predicting survival. The response rates associated with this burdensome method of 5FU administration in combination with either Mitomycin-C or Methyl-CCNU appear to offer little advantage over bolus 5FU alone.

Adenocarcinoma↗
PubMed1978

Mitomycin-C alone and in combination with infused 5-fluorouracil to the treatment of disseminated gastrointestinal carcinomas.

One hundred and thirty-two previously untreated patients with metastatic adenocarcinoma of the gastrointestinal (GI) tract were randomized to receive either a 120-hr infusion of 5-fluorouracil (5FU) with mitomycin-C or mitomycin-C alone. Superiority of the combination treatment was demonstrated with remissions in 30 out of 82 (37%) patients versus 9 out of 50 (18%) with the single drug treatment (P = 0.02). The median survial with 5FU--mitomycin-C was 29 weeks, as opposed to 20 weeks with mitomycin-C alone (P = 0.03). The combination produced significantly more severe myelotoxicity than the single drug, and jaundiced patients experienced more myelosuppression than non-jaundiced patients with both treatments.

Adenocarcinoma↗
PubMed1977

Changes in protein synthesis on mitomycin C induction of wild-type and mutant CloDF13 plasmids.

Mitomycin C treatment of Escherichia coli K-12 cells containing the nonconjugative plasmid CloDF13 resulted in inhibition of host chromosome protein synthesis and a high rate of synthesis of two CloDF13-specified proteins whose molecular weights correspond to cloacin and immunity protein. Five molecules of immunity protein were synthesized for each cloacin DF13 molecule. Mitomycin C-treated cells containing a copy mutant of CloDF13 made three to four times as much of each protein as cells containing wild-type CloDF13. CloDF13 plasmids that contained the transposon Tn1 were isolated. Two did not induce after mitomycin C treatment, failing both to inhibit host cell synthesis and to produce the two new proteins. In minicells, they showed reduced CloDF13-specified protein synthesis and produced three Tn1-specified proteins.

Bacteriocins↗
PubMed1978

Experimental results with the combination of bleomycin plus mitomycin C.

This investigation has established the following: 1. Bleomycin, in combination with mitomycin C or other quinone-containing anticancer agents, stimulated the damage to KB cells in culture. 2. In AH66 tumor-bearing rats, the simultaneous treatments of bleomycin plus mitomycin C extend the lifespan. 3. The bleomycin-induced DNA chain breakage was enhanced by the NADPH-dependent microsomal electron transport system. The enhancement was also observed at the level of isolated nuclei and cells. Vitamin K2 and mitomycin C increased breakage at the cellular level by bleomycin and NADPH. 4. Bleomycin-Cu2+ had tendency to increase the lipid peroxidation reaction by the microsomes. However, the reaction was effectively inhibited by antioxidants. 5. Bleomycin induced aldehyde formation from DNA breakage. The formation was effectively inhibited by scavenging reactions with hydralazine hydrochloride or isoniazid. The possibility of suppressing the side effect of bleomycin was discussed in relation to TBA reactive compounds.

Antibiotics, Antineoplastic↗
PubMed1978

Bone marrow and lymphocyte cytogenetics of rhesus monkeys (Macaca mulatta) treated with the clastogen Mitomycin C.

Rhesus monkeys (Macaca mulatta) were used to determine their effectiveness as experimental animals for different cytogenetic tests with mitomycin C (MC). The micronucleus test (MNT and/or chromosome analysis of blood and bone marrow were made before and/or after the treatment with mitomycin C. Thus, the controls data and treated data were obtained from the same animals. With the employed methology, the micronucleus test could not be performed on living animals. Less chromosomal damage was detected in the micronucleus test of post-mortem samples than in the chromosome analysis of bone marrow. No influence by the mutagen could be observed in lymphocyte chromosomes at any of the different times of analysis. In contrast to this, bone-marrow chromosomes seemed to be highly affected by mitomycin C at day 1, 2 and 3 after injection. However, before treatment and at day 14, 16 and 17 after treatment there was no visible increase in chromosomal aberration in bone marrow.

Animals↗
PubMed1975

Autoradiographic study of chick limb cartilage in vivo and in vitro and its response to mitomycin C (MMC).

Effect of mitomycin C on mucopolysaccharide synthesis by the cartilage cells of chick limb bud (5-9 days old) was investigated both in vivo and in vitro by the uptake study of 35S. Control specimens (both in vivo and in vitro) showed higher concentration of silver grains, mostly intercellular, in the initial stages. Hypertrophy of cartilage cells at later stages reduced the matrix, leading to a corresponding decrease in the accumulation of silver grains. In the treated groups, both in vivo and in vitro, the silver grains were found to be less in number during the initial stage of growth than in the corresponding controls, due to the suppressive effect of the mitomycin C. However, during the later period of growth, uptake of 35S was more in the matrix of treated specimens, which was apparently not reduced due to lack of hypertrophy of cartilage cells. The mechanism of the suppressive effect of mitomycin C seems similar in vivo and in vitro.

Animals↗
PubMed1978

Intratumor chemoimmunotherapy with mitomycin C and components from mycobacteria in regression of line 10 tumors in guinea pigs.

Intratumor chemotherapy with the use of mitomycin C and/or immunotherapy caused regression of line 10 carcinomas in strain 2 guinea pigs and resulted in development of tumor-specific immunity. The immunotherapeutic preparation consisted of oil-in-water emulsions containing Mycobacterium cell walls or residues of cell walls termed cell wall skeletons. The latter preparations were combined with trehalose dimycolate, which was isolated by microparticulate chromatography from whole cells of mycobacteria. Reducing mitomycin C to a single intratumor injection of 50 microgram produced little necrotizing effect and a mean tumor regression rate of 17%. Intratumor immunotherapy 1 day after treatment with 50 microgram of mitomycin C resulted in regression of 90% of the treated tumors as compared to mean regression rates of 30 to 50% for immunotherapy alone. In addition, chemoimmunotherapy was more effective than either chemotherapy or immunotherapy alone in producing regression of relatively large, as well as smaller, tumors.

Animals↗
PubMed1978

Long-term follow-up study of gastric cancer patients treated with surgery and adjuvant chemotherapy with mitomycin C.

A group of 496 cases was used in a controlled trial to study the possible value of mitomycin C as an adjuvant to curative surgery for gastric cancer. Patients assigned to receive the drug were given mitomycin C, 0.8 mg/kg body weight intravenously, twice a week for 5 weeks immediately after surgery. The control group was treated with surgery alone. Sixty-six patients were excluded from the study because of non-curative surgery. There was no over-all difference in survival and cancer death rates at 5 and 10 years between treated and control groups. However, a survival rate 18.6% higher at 5 years was observed in the subset of patients who had moderately advanced lymphatic metastases, and a survival rate 26.4% higher at 5 years was observed in the subset of patients who had involved serosa. The difference in cancer death rate was 14.5 and 24.0% in each subset, respectively. These significant differences persisted at 10 years. The effect of chemotherapy seemed to result from the successful inhibition of peritoneal dissemination and local recurrence. An adverse effect was observed in patients in the early stages cancer. These results suggest that mitomycin C could be useful as an adjuvant to curative surgery for moderately advanced stages of gastric cancer.

Adult↗
PubMed1978

Phase II trial of ftorafur with mitomycin C versus ftorafur with methyl-CCNU in untreated colorectal cancer.

In an attempt to substitute ftorafur for burdensome 5-fluorouracil (5-FU) infusions, 52 previously untreated patients were randomized to receive ftorafur with either mitomycin C or methyl-CCNU. Ftorafur was administered monthly as a 2-hour infusion daily x 5 days. Mitomycin C and methyl-CCNU were repeated every 8 weeks. A response rate of 27% (seven responses among 26 patients) was demonstrated on the mitomycin C arm compared to a response rate of 15% (four responses among 26 patients) on the methyl-CCNU arm (P = 0.25). There was no significant difference in the median survival between treatment arms. Central nervous system toxicity occurred in greater than 30% of the patients and appeared to be the limiting factor with ftorafur administration. Alternate schedules of ftorafur should be explored since there appears to be little advantage of a daily ftorafur schedule over conventional 5-FU infusions.

Adenocarcinoma↗
PubMed1976

Phase II study of mitomycin-C, vincristine, and bleomycin in advanced squamous cell carcinoma of the uterine cervix.

Utilizing the stathmokinetic principle of timed vincristine and bleomycin, we combined these two agents with Mitomycin-C. The dose schedule included vincristine 0.5 mg/m2 intravenously (i.v.) geginning on day 1 and repeated twice weekly for 12 weeks; each injection was followed in 6-12 hours by bleomycin 6 mg/m2 for 12 weeks. Mitomycin-C was administered as a 20 mg/m2 bolus beginning on day 2 and repeated at 6-week intervals. Thirty patients were entered into this study, 27 were fully available for response. Thirteen patients (48%) met criteria of response (greater than 50% reduction in volume of measurable tumor). Significant myelosuppression resulted from this therapy. Median leukopenia nadir was 3.8 X 10(3) cells/mm3 and median thrombocytopenia nadir was 116 X 10(3) cells/mm3. Additional toxic reactions included anemia, lassitude, anorexia, peripheral neuropath fever, and skin rash. Despite significant, but manageable, toxicity, this combination appears to represent an improvement in the chemotherapy of a traditionaly refractory solid tumor.

Adult↗
PubMed1979

Effect of mitomycin C and 60Co gamma-irradiation on the replication of SV40 in cell lines of varying permissivity for SV40 replication.

The effects of mitomycin C and 60Co gamma-irradiation, which induce production of SV40 from SV40-transformed hamster cells, on the replication of superinfecting SV40 or virus DNA in cells varying in permissivity for SV40 replication have been examined. These agents enhance replication of SV40 in an uninducible line of SV40-transformed hamster kidney cells and in nonpermissive secondary hamster kidney cells. The same treatments do not affect SV40 replication in semipermissive hamster (BHK21) and human (HEL, HEK) cells and inhibit SV40 replication in permissive monkey (TC-7) cells. We conclude that forms of induction treatment, such as mitomycin C or 60Co gamma-irradiation, modify the expression of host cell factors which determine the level of permissivity for SV40 infection.

Animals↗
PubMed1976

Effects of alkylation by dimethyl sulfate, nitrogen mustard, and mitomycin C on DNA structure as studied by the ethidium binding assay.

The extent of alkylation of DNA by dimethyl sulfate, nitrogen mustard, and the antibiotic mitomycin C is related to the resulting decrease in the fluorescence of intercalated ethidium. The fluorescence losses due to the first two types of reagents show a marked pH dependence, with greater losses of fluorescence being observed at alkaline pH values. At pH 11.6 the fluorescence shows a slow recovery, so that with low levels of methylation (4% deoxyguanosine residues modified) one observes complete return of fluorescence. We postulate that these phenomena are due to conversion of 7-methyldeoxyguanosine to the zwitterionic form, and partial denaturation of the DNA duplex with loss of ethidium binding sites. Hydroxide-ion-catalyzed imidazole ring opening, and the removal of the positive charge permits reannealing with concomitant return of the ethidium intercalation sites. This conclusion is substantiated by enzymatic hydrolysis of 14C-labelled methylated DNA and identifiions of the ethidium assay. The distinctly different behavior of mitomycin C confirms previous conclusions that its alkylation, preferentially on guanine, does not take part at the N-7 position.

Alkylating Agents↗
PubMedDate not supplied

Phase II study of hexamethylmelamine alone and in combination with mitomycin C and vincristine in advanced breast carcinoma.

Fifty-three patients with metastatic breast carcinoma were randomized to treatment with hexamethylmelamine (HMM) as a single agent versus a three-drug reimen of HMM, vincristine, and mitomycin C (HOM). All patients had received prior treatment with 5-fluorouracil, Adriamycin, and cyclophosphamide with or without methotrexate. HMM alone was used in a dose of 300 mg/m2/day x 14 days every 21 days. In the HOM regimen, the HMM dose was 200 mg/m2/day x 21 days, the vincristine dose was 1.5 mg on Days 1, 8, and 15, and the mitomycin C dose was 12 mg/m2 once every 6 weeks. No objective responses were observed with HMM in 15 evaluable patients. The HOM regimen resulted in five partial responses among the 27 evaluable patients. Gastrointestinal toxicity was the limiting toxicity of HMM, and thrombocytopenia was the major toxicity of the HOM regimen.

Adult↗