Anomalous induction of mycobacteriophages mediated by mitomycin C.
Mitomycin C has been found to stimulate the production of long-tailed defective bacteriophages and poly tails in thick cell wall mycobacterial mutants.
Microscopy, Electron↗
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"Induction" of colicin factor E2-P9 by mitomycin C.
Mitomycin C increases the titers of colicin E2-P9 without increasing the amount of colicin factor deoxyribonucleic acid.
Centrifugation, Density Gradient↗
The derivation of 1a-demethylmitomycin G from mitomycin C.
Mitomycin G (2) was derived from porfiromycin (10b) in 3 steps via the methanesulfonate (14b) in an overall yield of 39%. On the basis of the established method for the introduction of an exomethylene group in mitomycins with a 9a-methoxy group, the preparation of biologically more important 1a-demethylmitomycin G (5) from mitomycin C (1) was accomplished by the use of a protective acetyl group on the aziridine in an overall yield of 57%. 1a-Demethylmitomycin K (6) was obtained from 5 in a yield of 42%. In a preliminary evaluation of their antitumor activity, compound 5 showed superior activity against sarcoma 180 (sc-ip) to its 1a-methyl congener, i.e., mitomycin G (2).
Animals↗
Differential activation of p53 by the various adducts of mitomycin C.
Mitomycin C (MC) is a cytotoxic chemotherapeutic agent that causes DNA damage in the form of DNA cross-links as well as a variety of DNA monoadducts and is known to induce p53. The various DNA adducts formed upon treatment of mouse mammary tumor cells with MC as well as 10-decarbamoyl MC (DMC) and 2,7-diaminomitosene (2,7-DAM), the major MC metabolite, have been elucidated. The cytotoxicity of DMC parallels closely that of MC in a number of rodent cell lines tested, whereas 2,7-DAM is relatively noncytotoxic. In this study, we investigate the ability of MC, DMC, and 2,7-DAM to activate p53 at equidose concentrations by treating tissue culture cell lines with the three mitomycins. Whereas MC and DMC induced p53 protein levels and increased the levels of p21 and Gadd45 mRNA, 2,7-DAM did not. Furthermore, MC and DMC, but not 2,7-DAM, were able to induce apoptosis efficiently in ML-1 cells. Therefore the 2,7-DAM monoadducts were unable to activate the p53 pathway. Interestingly, DMC was able to initiate apoptosis via a p53-independent pathway whereas MC was not. This is the first finding that adducts of a multiadduct type DNA-damaging agent are differentially recognized by DNA damage sensor pathways.
Apoptosis↗
Alkylation of calf thymus DNA with reductively activated mitomycin C.
Mitomycin C (MMC) was catalytically reduced in the presence of a nucleotide or calf thymus DNA. Reaction with 5'-guanylic acid (5'-GMP) gave 1,2-cis-2, 7-diamino-1-(5'-guanylyl) mitosene. Reaction with calf thymus DNA gave modified DNA, which on enzymatic hydrolysis gave two alkylated 5'-deoxyguanylic acid (MG-1 and MG-2) and an alkylated 5'-deoxyadenylic acid (MA). This is the first example of isolation of nucleotides from DNA modified by MMC.
Alkylation↗
Chemical modification of DNA with muta-carcinogens. III. Reductive alkylation of DNA with mitomycin C.
Mitomycin C (MMC) binds to DNA after its reductive activation by catalytic hydrogenation with Pd on charcoal. Three modified nucleotides, named MG-1, MG-2, and MA, were isolated from the modified DNA after enzymatic hydrolysis to 5'-nucleotides. The structures of these modified nucleotides were deduced from their 1H-NMR and UV spectra, and from studies of the chemically transformed derivatives (hydrolysis, methylation, diazotization, and thioketonization). These three modified nucleotides were concluded to be 1,2-trans-2,7-diamino-1-(N2-deoxyguanylyl)mitosene (MG-1), 2,7-diamino-1-(O6-deoxyguanylyl)mitosene (MG-2) and 2,7-diamino-1-(N6-deoxyadenylyl)mitosene (MA). The same modified nucleotides were identified in DNA extracted from the livers of rats treated with MMC.
Alkylation↗
Evaluation of the stability of extemporaneously prepared ophthalmic formulation of mitomycin C.
Mitomycin C (MMC) is a cytostatic agent topically used in conjunctival neoplasms, secondary to glaucoma filtering, pterygium, and strabismus surgery to increase the success rate. The topical formulation of MMC for ocular use is always extemporaneously prepared. Our study evaluated the stability of extemporaneously prepared formulations of MMC at different concentrations (150, 300, & 600 microg/mL) kept at different temperatures (25 degrees , 4 degrees , and -70 degrees C) and at different pH range (6, 7, and 8). Aliquots from the above formulations were subjected for quantification of MMC on days 0, 7, 14, 21, and 28 using high-performance liquid chromatography. MMC stored at 25 degrees C for 6 months was also subjected to flow cytometry and compared to freshly prepared MMC. The results indicated that the degradation of MMC is very high in acidic pH at room temperature. Increasing the pH to 7 or 8 and keeping MMC at low temperatures significantly decreased the degradation of MMC. Interestingly, the flow cytometry data revealed that the 6-month-old MMC showed an antiproliferative effect compared to that of freshly prepared MMC. To conclude, the extemporaneously prepared MMC at pH between 7 and 8 and stored in the refrigerator can increase the duration of its stability. However, the antiproliferative study using flow cytometry revealed that degraded MMC retained its activity even after degradation.
Antibiotics, Antineoplastic↗
Genetic localization and molecular characterization of two key genes (mitAB) required for biosynthesis of the antitumor antibiotic mitomycin C.
Mitomycin C (MC) is an antitumor antibiotic derived biosynthetically from 3-amino-5-hydroxybenzoic acid (AHBA), D-glucosamine, and carbamoyl phosphate. A gene (mitA) involved in synthesis of AHBA has been identified and found to be linked to the MC resistance locus, mrd, in Streptomyces lavendulae. Nucleotide sequence analysis showed that mitA encodes a 388-amino-acid protein that has 71% identity (80% similarity) with the rifamycin AHBA synthase from Amycolatopsis mediterranei, as well as with two additional AHBA synthases from related ansamycin antibiotic-producing microorganisms. Gene disruption and site-directed mutagenesis of the S. lavendulae chromosomal copy of mitA completely blocked the production of MC. The function of mitA was confirmed by complementation of an S. lavendulae strain containing a K191A mutation in MitA with AHBA. A second gene (mitB) encoding a 272-amino-acid protein (related to a group of glycosyltransferases) was identified immediately downstream of mitA that upon disruption resulted in abrogation of MC synthesis. This work has localized a cluster of key genes that mediate assembly of the unique mitosane class of natural products.
Amino Acid Sequence↗
A unique cytosolic activity related but distinct from NQO1 catalyses metabolic activation of mitomycin C.
Mitomycin C (MMC) is a prototype bioreductive drug employed to treat a variety of cancers including head and neck cancer. Among the various enzymes, dicoumarol inhibitable cytosolic NAD(P)H:quinone oxidoreductase1 (NQO1) was shown to catalyse bioreductive activation of MMC leading to cross-linking of the DNA and cytotoxicity. However, the role of NQO1 in metabolic activation of MMC has been disputed. In this report, we present cellular and animal models to demonstrate that NQO1 may play only a minor role in metabolic activation of MMC. We further demonstrate that bioreductive activation of MMC is catalysed by a unique cytosolic activity which is related but distinct from NQO1. Chinese hamster ovary (CHO) cells were developed that permanently express higher levels of cDNA-derived NQO1. These cells showed significantly increased protection against menadione toxicity. However, they failed to demonstrate higher cytotoxicity due to exposure to MMC under oxygen (normal air) or hypoxia, as compared to the wild-type control CHO cells. Disruption of the NQO1 gene by homologous recombination generated NQO1-/- mice that do not express the NQO1 gene resulting in the loss of NQO1 protein and activity. The cytosolic fractions from liver and colon tissues of NQO1-/- mice showed similar amounts of DNA cross-linking upon exposure to MMC, as observed in NQO1+/+ mice. The unique cytosolic activity that activated MMC in cytosolic fractions of liver and colon tissues of NQO1-/- mice was designated as cytosolic MMC reductase. This activity, like NQO1, was inhibited by dicoumarol and immunologically related to NQO1.
Animals↗
32P-analysis of DNA adducts in somatic and reproductive tissues of rats treated with the anticancer antibiotic, mitomycin C.
Mitomycin C (MMC) is a clinically used drug with mutagenic and antitumor activities, presumably elicited through its covalent binding to DNA, however, little is known about MMC binding to DNA in vivo. A 32P-postlabeling method that does not require radiolabeled test compounds was employed here to study the formation of DNA adducts in somatic and reproductive tissues of rats 24 h after an i.p. dose of 9 mg/kg MMC. Among 14 tissues studied in female rats, MMC-DNA adduct levels were within a 2-fold range in 11 tissues, i.e. bladder, colon, esophagus, heart, kidney, liver, lung, ovary, pancreas, small intestine and stomach (minimum levels of 9.6-21.9 adducts per 10(7) N). Three other tissues, i.e. brain, spleen and thymus, exhibited lower adduct levels (0.2 5.4 and 1.4 adducts, respectively, per 10(7) N). Liver DNA adduct levels were 32% lower in male than in female rats. Testicular DNA contained 2.5 adducts per 10(7) N, i.e. 5.3 times less than ovarian DNA. 32P-labeled adduct patterns were qualitatively similar among the different tissues and consisted of 10 adducts, one of which comprised 71 (+/- 5)% of the total. All these adducts were chromatographically identical to adducts formed by the reaction of chemically reduced MMC with DNA in vitro, demonstrating that metabolic activation of MMC occurred via reduction. Using homopolydeoxyribonucleotides modified with MMC, in vivo adducts were shown to be mostly (greater than 90%) guanine derivatives and small amounts of adenine, cytosine and thymine products. Most of the adducts appeared to be monofunctional derivatives of DNA nucleotides. Dose-dependent MMC-DNA adduct formation was determined in rat liver over an 82-fold range of MMC administered (0.11-9.0 mg/kg). The lowest dose level studied was 4.5 times lower than the recommended single dose for human cancer chemotherapy (20 mg/m2). Thus, these results predict that 32P-postlabeling methodology is suitable to monitor and quantify DNA adducts in tissue biopsies of patients receiving MMC chemotherapy.
Animals↗
[A prospective and randomized study of the complete response, index of recurrences and progression in superficial bladder carcinoma treated with mitomycin C alone versus mitomycin C and BCG alternatively].
The results of a comparative randomized study on intravesical chemoprophylaxis are presented. The study comprised 66 patients; one group of 29 patients received mitomycin C alone, while another group of 37 patients received mitomycin C and alternating BCG therapy. This latter treatment modality was found to achieve a slightly higher complete response rate and a much lower tumor progression rate. Although these results were not statistically significant (p > 0.05), they indicate that if the study were comprised of a larger series, the combined modality may be shown to achieve better results than the other modalities currently used.
BCG Vaccine↗
Sequence-specific DNA damage induced by reduced mitomycin C and 7-N-(p-hydroxyphenyl)mitomycin C.
Mitomycin C reduced with sodium borohydride induced the DNA damage at deoxyguanosines preferentially in dinucleotide sequence G-T. The DNA damage produced strand breaks when subsequently heated. The DNA damage scarcely occurred when the end-labeled DNA was preincubated with ethidium bromide or actinomycin D before the addition of mitomycin C and the reducing agent. Fully reduced mitomycin C did not induce the DNA damage. The mitomycin C-inducing DNA damage seems to require the intercalation of the partially reduced mitomycin C of short life time, probably semiquinone radical, between DNA base pairs. The inhibitory effects of sodium chloride and radical scavengers suggested that the requirement of the covalent bond formation of mitomycin C to DNA and the involvement of oxygen radicals in the DNA damage. 7-N-(p-hydroxyphenyl)mitomycin C, which is reported to show a higher antitumor activity and a lower toxicity than mitomycin C, was readily reduced with dithiothreitol and induced the sequence-specific DNA damage, whereas mitomycin C was not.
Bacteriophage phi X 174↗
Characterization of liposomes and an emulsion containing mitomycin C or lipophilic mitomycin C prodrugs.
The characteristics of liposomes and an oil-water emulsion containing either mitomycin C (MMC) or its lipophilic prodrugs were investigated. Prodrugs were incorporated into liposomes and oil droplets of an oil-water emulsion, and this incorporation was dependent on the lipid content of the liposomes and droplets. A good correlation was observed between the calculated lipid:water partition ratios and partition coefficients in chloroform:water. The prodrugs were rapidly distributed between the lipid and aqueous phases when they were injected into the dispersion medium of empty liposomes and an oil-water emulsion, or when the formulations incorporating prodrugs were diluted with water. Addition of prodrugs to liposomes containing perylene resulted in a decrease of fluorescence. Based on these findings, prodrugs were concluded to be incorporated into lipidic dispersion formulations based on their partitioning behavior. N1a-[(Nonyloxy)carbonyl]MMC (7) showed the highest incorporation into lipidic formulations, while prodrugs with moderate lipophilicities were rapidly released from lipid particles. Liposomes incorporating 7 maintained their multilamellar vesicular form as shown by electron microscopy and by examining their entrapping capacity for water soluble marker dyes. The release of prodrug 7 from both formulations was slow in a buffer solution, but considerable release and conversion to the parent drug were observed when rat plasma was added to the same system. These results suggest that the stability of MMC could be improved by incorporation into lipidic formulations and that a suitable release rate in vivo could be accomplished by use of a prodrug.
Chemical Phenomena↗
Comparative studies on the action of 7-N-[2-[[2-(gamma-L-glutamylamino)ethyl]dithio]ethyl]mitomycin C and of mitomycin C on cultured HL-60 cells and isolated phage and plasmid DNA.
The mechanism of action of a new mitomycin C (MMC) derivative, KT6149, was studied in human leukemia HL-60 cells and in isolated phage and plasmid DNA, and its effects were compared with those of MMC. Cell growth was markedly inhibited by KT6149, with an IC50 of 2 x 10(-9) M, that for MMC being 2 x 10(-8) M. DNA synthesis of HL-60 cells as determined by incorporation of [3H]-thymidine was also inhibited by KT6149, with an IC50 of 2 x 10(-7) M as compared with 2 x 10(-6) M for MMC. RNA and protein synthesis were less markedly inhibited at low concentrations. Alkaline sucrose density-gradient centrifugation revealed a significant decrease in sedimentation velocity for cellular DNA of the cells after 1 h treatment with KT6149 at concentrations higher than 10(-7) M. In contrast, no such change was observed for DNA of cells treated with MMC, even at a concentration of 10(-5) M. In a cell-free system, analysis by agarose gel electrophoresis patterns showed that the drug induced a decrease in the amount of covalently closed circular DNA of phage PM2 and an increase in that of open circular DNA in the presence of dithiothreitol (DTT), whereas MMC did not cause any change in DNA subfraction amounts. Furthermore, the electrophoretic mobility of linearized pBR322 DNA in alkaline agarose gel was significantly decreased by KT6149 in the presence of DTT and FeSO4, no such change being observed in the case of MMC. The results clearly indicate that the inhibitory effects of KT6149 on the growth and DNA synthesis of HL-60 cells are more potent than those of MMC and that KT6149-induced DNA damage is due to single-strand scission and to cross-linking of DNA, suggesting a mode of activation different from that of MMC.
Antineoplastic Agents↗
Determination of the new anticancer agent KW 2149, 7-N-[2-[2-(gamma-L-glutamylamino)ethyl)dithio)ethyl]mitomycin C, an analogue of mitomycin C.
The new mitomycin 7-N-[2-[2-(gamma-L-glutamylamino)ethyl)dithio)ethyl] mitomycin C (KW 2149) (I) proved to be active against a wide variety of experimental tumours. In order to perform pharmacokinetic studies with the new drug in Phase I sessions, a fast and reliable method has been developed based on the data of previous assays for mitomycin C. XAD-2 was preferred for isolation of I from blood plasma. The recovery of I was 50% whereas that of mitomycin C was 85%. Optimal separation was obtained on octadecyl silica columns with methanol-water (45:55, v/v) as mobile phase, while ultraviolet absorbance detection was performed at 375 nm. The assay enabled determination of I in a plasma concentration range of 20-1000 ng/ml using porfiromycin as internal standard.
Antineoplastic Agents↗
A randomized trial with mitomycin-C/ifosfamide versus mitomycin-C/vindesine versus cisplatin/etoposide in advanced non-small-cell lung cancer.
192 evaluable patients with advanced inoperable non-small-cell lung cancer were treated with either mitomycin-C/ifosfamide (A), mitomycin-C/vindesine (B), or cisplatin/etoposide (C) in a prospective randomized trial. The response rates for each treatment arm were 30.0% (A), 22.7% (B), and 25% (C), respectively. There was no statistically significant difference (p = 0.4) between treatment arms. The median survival time was 27 weeks (A), 23 weeks (B), and 25 weeks (C), respectively. With regard to toxicity the combination mitomycin-C/vindesine was superior to treatment arms A and C. Nausea and vomiting (WHO 3 + 4) occurred only in 6.1% of the patients versus 43.3% of those treated with mitomycin-C/ifosfamide and 36.7% of those treated with cisplatin/etoposide. This difference is statistically highly significant (p = 0.0001). Because of its very low toxicity, especially for gastrointestinal symptoms, the combination mitomycin-C/vindesine was judged superior to the other combinations. None of these regimens, however, had a major impact on survival in advanced non-small-cell lung cancer.
Adult↗
Structure-activity comparison of mitomycin C and mitomycin A analogues (review).
Over 600 analogues of mitomycin C (MMC) have been made in the past and more recently a number of Mitomycin A (MMA) derivatives have been prepared. Since many of the MMA type had the same organic side chain at the 7-position as previously prepared MMC analogues it was of interest to see if the biological effects of MMCs could predict for those of MMAs. Using the P388 leukemia model it was possible to compare the activity of 27 matched pairs and the potency of 24 pairs. It was found that antitumor effects did not correlate but that MMAs were significantly more potent than MMCs. These findings were duplicated in tests of 7 pairs against subcutaneously implanted B16 melanoma. We conclude that any MMA derivative would have a high likelihood of being more potent than its MMC equivalent but that its antitumor effects must be independently determined since they cannot be predicted from the results with MMC analogs.
Animals↗
Randomized phase II study of irinotecan plus mitomycin C vs. oxaliplatin plus mitomycin C in patients with advanced fluoropyrimidine/leucovorin-pretreated colorectal cancer.
INTRODUCTION: Irinotecan and oxaliplatin are two new agents with promising activity in advanced colorectal cancer. Based on preclinical and clinical evidence that both drugs might act synergistically with mitomycin C, a randomized study using a 'pick the winner' design was undertaken to determine the effectiveness and tolerance of these two combination schedules in patients with fluoropyrimidine/leucovorin-pretreated advanced colorectal cancer. PATIENTS AND METHODS: Sixty-four patients with metastatic colorectal cancer, who progressed while receiving or within 6 months after discontinuing palliative chemotherapy with fluoropyrimidines/leucovorin were enrolled onto this study. They were randomly assigned to treatment with irinotecan 120 mg/m2 on days 1 + 15 plus mitomycin C 8 mg/m2 on day 1 (arm A) or oxaliplatin 85 mg/M2 on days 1 + 15 plus mitomycin C 8 mg/m2 on day 1 (arm B). In both treatment arms, courses were repeated every 4 weeks. RESULTS: The objective response rate in arm A is 7/33 (21.2%; 95% confidence interval, 9.0-38.9%) as compared to 5/31 in arm B (16.1%; 95% CI, 5.5-34.7%). Stable disease was noted in 48.5 vs. 45.2%, whereas the tumor progressed in 30.3 vs. 38.7%, respectively. Similar to the recorded response activities, the difference of the two combination regimens in terms of median time to progression (7.0 vs. 5.2 months) and overall survival (12.0 vs. 11.2 months) was only minor and clincally insignificant. The tolerance of treatment was acceptable in both arms, though severe adverse reactions requiring dose reductions (30 vs. 16%) and treatment delays (22 vs. 13% of courses) were more commonly noted with irinotecan/mitomycin C. The most common toxicities in arm A were neutropenia (85%; WHO grade 3/4 in 33%), thrombocytopenia (52%), diarrhea (45%), emesis (52%) and alopecia (92%). In arm B, common toxicities included neutropenia (68%; grade 3/4 in 13%), thrombocytopenia (81%), emesis (52%), and peripheral neutropathy (48%). CONCLUSIONS: Both mitomycin C combination regimens seem to provide an acceptable therapeutic index in patients with fluoropyrimidine/leucovorin-pretreated metastatic colorectal cancer. In view of the increasing need for a broader chemotherapeutic armentarium for second-line therapy of this common malignant disease, both regimens may be worthwhile to undergo further clinical investigation.
Adenocarcinoma↗