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PubMed1997

Micronuclei, centromere-positive micronuclei and chromosome nondisjunction in cytokinesis blocked human lymphocytes following mitomycin C or vincristine treatment.

The influence of sampling time on the frequencies of micronuclei, centromere-positive micronuclei and chromosome nondisjunction was investigated in binucleated lymphocytes following treatment with a known clastogen (mitomycin C) or an aneuploidy-inducing agent (vincristine sulfate). Cytochalasin B (6 micrograms/ml) was added 44 h after mitogen stimulation and cultures were harvested 12, 28, 36 and 48 h thereafter. Micronucleated cells and micronuclei were significantly induced by the two treatments at all sampling times. Furthermore, in situ hybridization with an 'all centromeres' probe showed that vincristine-induced micronuclei were prevalently centromere-positive whereas in mitomycin C-treated cultures only a minor fraction of induced micronuclei contained the hybridization signals. Chromosome nondisjunction rates, as measured by in situ hybridization with chromosome 7- and 11-specific alphoid probes, significantly increased following vincristine treatment. Chromosome nondisjunction and total micronucleus frequencies were found to increase with time both in controls and in mutagen-treated cultures, whereas the percentage of centromere-positive micronuclei in the different treatments was not influenced by the sampling time. Our data suggest that even in the presence of 6 micrograms/ml cytochalasin B, the abnormal segregation of binucleated cells may contribute to the baseline level of micronuclei and influence the results obtained. The introduction of a short cytochalasin B treatment (between 12 and 28 h) in the cytokinesis-blocked micronucleus assay may avoid the cytochalasin B effect on micronucleus frequencies.

Aneuploidy↗
PubMed1998

Mitomycin-C in the treatment of tracheal cicatrix after tracheal reconstruction.

OBJECTIVE: To demonstrate the potential use of Mitomycin-C (MMC) in the treatment of difficult and recurrent tracheal stenosis. DESIGN: Case series. SETTING: Tertiary care setting. PATIENTS: A retrospective chart review was performed on five pediatric patients with severe, recurrent tracheal granulation and cicatrix after tracheal reconstruction who were treated with topical MMC as an adjunct to bronchoscopy and laser treatment. MMC was applied intraoperatively on saturated pledgets at a dose of 0.1 mg/ml for 2 min to the area where the cicatrix had been lysed. The five patients were able to be decannulated. DISCUSSION: Mitomycin-C is an anti metabolite known to inhibit fibroblast proliferation in vitro. This agent has been used with a high success rate in glaucoma filtration surgery to promote patency of the trabecula. The results of this preliminary application in the pediatric airway as well as the mechanism of action will be discussed.

Administration, Topical↗
PubMed2002

Pulmonary veno-occlusive disease after neoadjuvant mitomycin chemotherapy and surgery for lung carcinoma.

Pulmonary veno-occlusive disease (PVOD), an uncommon cause of pulmonary hypertension (PH) has been reported following treatment of a variety of different malignancies with various chemotherapy. We report here the cases of two patients with non-small cell lung cancer (NSCLC) who developed fatal PH after combined treatment with surgery and a mitomycin containing perioperative chemotherapy (PCT). PVOD was documented at autopsy in one patient and was strongly suspected in the other patient who had an identical clinical presentation and in whom the work-up looking for another cause of PH was negative. Mitomycin was incriminated in both cases. Without questioning the potential interest of perioperative chemotherapy in resectable NSCLC, these observations illustrate the risks related to the combination of pneumotoxic chemotherapy and thoracic surgery.

Antibiotics, Antineoplastic↗
PubMed2002

Vinorelbine plus cisplatin versus cisplatin plus vindesine and mitomycin C in stage IIIB-IV non-small cell lung carcinoma: a prospective randomized study.

PURPOSE: To compare a regimen of vinorelbine and cisplatin (VC) to the combination of mitomycin, vindesine, and cisplatin (MVP) in patients with stage IIIB or stage IV non-small cell lung cancer (NSCLC). The main endpoits were analysis of objective response rates, toxicity, time to progression, and overall survival. PATIENTS AND METHODS: 247 eligible patients were randomized to receive (a) vinorelbine 25 mg/m(2) intravenous bolus on days 1 and 8 plus cisplatin 100 mg/m(2) on day 1 every 4 weeks, or (b) mitomycin c 8 mg/m(2) i.v. on day 1, vindesine 3 mg/m(2) i.v. on days 1, 8, 15 and 22, plus cisplatin 100 mg/m(2) on day 1 every 4 weeks. In subsequent cycles vindesine was given every other week. For both treatments a maximum of six cycles was planned. Patients with performance status 0-2 according to the ECOG scale were enrolled. Response and toxicity were evaluated according to the WHO criteria. Analysis of clinical efficacy was performed according to an intent-to-treat analysis. RESULTS: No statistically significant differences in clinical efficacy were observed between the two chemotherapy regimens. The overall objective response rates were 39% (95% CL, 31-49%) in the VC arm and 42% (95% CL, 33-51%) in the MVP arm (P=0.13). Median time to progression was 4.2 and 4.5 months for the MVP arm and the VC arm, respectively. Median overall survival was 7 months in the VC arm and 8 months in the MVP one (log-rank test, P=0.898). These differences were not statistically significant. However, leukopenia and thrombocytopenia were significantly higher in the MVP arm than in the VC (P=0.0001; P=0.0002). Grade 3 alopecia was more frequent in the MVP arm than in the VC one (P<0.001), which was associated with higher rate of phlebitis (P=0.037). CONCLUSION: Data achieved in this study suggest that the vinorelbine-cisplatin doublet is similar to the three-drug MVP regimen in term of overall response rate, time to progressive disease, and overall survival. However, hematological toxicity and alopecia are more frequent and severe in the MVP regimen which therefore appears to be less tolerable than the VC regimen. The combination of vinorelbine and cisplatin may be considered as a reference treatment for future studies on the treatment of advanced NSCLC.

Adult↗
PubMed1997

Endotheliopathy: a continuum of hemolytic uremic syndrome due to mitomycin therapy.

Hemolytic uremic syndrome (HUS) is a rare, often fatal complication of mitomycin C therapy. It is generally accepted that HUS is, in part, caused by endothelial cell dysfunction. Endothelial cells modulate blood flow, blood pressure, and myointimal proliferation. Endothelial cells synthesize and release products that modulate vascular tone and regulate vascular smooth muscle cell growth. We describe a patient who developed HUS secondary to mitomycin C, resulting in end-stage renal disease and necessitating chronic hemodialysis. Over several months, the patient subsequently developed multisystem organ failure involving the heart, liver, and intestine that was associated with angiographically documented small, distal vessel occlusive disease and ultrasonographically identified coronary artery intimal hyperplasia. We propose that a diffuse ongoing endothelial cell dysfunction (ie, endotheliopathy) is the putative mechanism for this patient's clinical course. To our knowledge, this continuum of HUS presenting as a multisystem, progressive disorder has not been previously reported.

Adult↗
PubMed1978

Induced chromosomal aberrations in somatic cells of Nigella sativa L. by mitomycin C.

A cytological study was carried out on root tips of Nigella sativa L. by treatment with Mitomycin C at 0.001% for six time intervals (10, 15, 20, 30, 40, and 50 min). The chromosomal abnormalities were increasingly proportionate to the increase in time of treatment. The seedlings treated with a 0.001% concentration of Mitomycin C for 10 min. did not show any significant effect. At other time intervals, the effect was observed to be quite significant. Beyond 40 min. treatment almost all the cells would become sticky. Thirty minutes' treatment showed significant effect, inducing various types of chromosomal aberrations in the anaphase, such as bridges and fragments of 34.13% and 48.07%, respectively.

Anaphase↗
PubMed2003

In vivo cell kinetic measurements in a randomized trial of continuous hyperfractionated accelerated radiotherapy with or without mitomycin C in head-and-neck cancer.

PURPOSE: Tumor cell repopulation is still considered to be a major cause of failure in radiotherapy. In this study, we investigated the influence of cell kinetic parameters on the outcome of patients treated in a randomized trial of accelerated fractionation, with or without mitomycin C, vs. conventional fractionation. METHODS AND MATERIALS: Sixty-two patients were studied using administration of bromodeoxyuridine (BrdUrd), and cell kinetic parameters were measured using flow cytometry. The patients were treated with either 70 Gy for 7 weeks or 55.3 Gy for 17 continuous days (V-CHART) with or without 20 mg/m(2) mitomycin C on day 5. RESULTS: The potential doubling time (Tpot) and labeling index (LI) failed to provide any prognostic information with regard to local control or survival. However, the duration of the S phase (Ts) revealed patients whose tumors had a long Ts had significantly worse local control (p = 0.028) and survival (p = 0.034) irrespective of treatment. A similar trend was evident within the different treatment arms particularly associated with overall survival. CONCLUSIONS: The Ts values of head-and-neck squamous cell cancers provided prognostic information that predicted clinical outcome irrespective of treatment schedule in this study. This neglected parameter of the Tpot method might provide information related to redistribution of cells during fractionated radiotherapy.

Analysis of Variance↗
PubMed2003

Phase II study of three-dimensional conformal radiotherapy and concurrent mitomycin-C, vinblastine, and cisplatin chemotherapy for Stage III locally advanced, unresectable, non-small-cell lung cancer.

PURPOSE: To evaluate the feasibility, treatment outcome, and toxicity of hyperfractionated three-dimensional conformal radiotherapy (CRT) and concurrent mitomycin-C, vinblastine, and cisplatin (MVP) chemotherapy in locally advanced, unresectable, Stage III non-small-cell lung cancer (NSCLC). METHODS AND MATERIALS: Between August 1993 and December 1996, 161 patients with unresectable Stage III NSCLC were entered into this trial, and 146 (91%) completed the treatment. Hyperfractionated RT was given to a total dose of 64.8-70 Gy (1.2 Gy/fraction, b.i.d.) with two cycles of concurrent MVP chemotherapy (mitomycin-C 6 mg/m(2) on Days 2 and 29, vinblastine 6 mg/m(2) on Days 2 and 29, and cisplatin 60 mg/m(2) on Days 1 and 28). Of the 146 patients who completed the treatment, 78 received noncoplanar three-dimensional CRT using 4-6 fields and 17 received coplanar-segmented CRT. The clinical tumor response was assessed 1 month after RT completion by CT. Toxicity was graded using the Southwestern Oncology Group criteria. The normal tissue complication probability for the lung was calculated to determine the correlation with radiation pneumonitis, if any. Nineteen (13%) had Stage IIIA and 127 (87%) had IIIB disease, including 16 patients with pleural effusion and 20 with supraclavicular lymph node metastasis. RESULTS: The response rate was 75%, composed of 22% complete responders and 53% partial responders. With a minimal follow-up of 45 months, the overall survival rate was 51.2% at 1 year, 25.1% at 2 years, and 14.8% at 5 years; the median survival was 12 months. Patients achieving a complete response (n = 32) had a 2-year overall survival rate of 49.8% and a 5-year survival rate of 39.2% compared with 22.5% and 11.4%, respectively, for the partial responders (n = 78; p = 0.0001). The actuarial local progression-free survival rate for all patients was 65.4% at 1 year, 42.1% at 2 years, and 36.3% at 4 years, and the actuarial distant-free survival rate was 65.4% at 1 year, 42.1% at 2 years, and 36.2% at 5 years. Severe weight loss (>10%) occurred in 20 (13.7%) of the 146 patients during treatment, 42 patients (29%) developed radiation pneumonitis (29 Grade 1 and 13 Grade 2). The average normal tissue complication probability value of the patients who had radiation pneumonitis was significantly greater than that of patients without pneumonitis (66.0% vs. 26.4%). Four patients died of treatment-related toxicity. CONCLUSION: Hyperfractionated three-dimensional CRT and concurrent chemotherapy, as described here, is a well-tolerated regimen with acceptable toxicity. More effective treatment schemes are required to improve local disease control and overall survival.

Adult↗
PubMed1998

Continuous hyperfractionated accelerated radiotherapy with/without mitomycin C in head and neck cancer.

PURPOSE: To evaluate the effect of mitomycin C to an accelerated hyperfractionated radiation therapy. The aim was to test a very short schedule with/without mitomycin C (MMC) with conventional fractionation in histologically verified squamous cell carcinoma of the head and neck region. METHODS AND MATERIALS: From October 1990 to December 1996, 188 patients entered the trial. Tumors originated in the oral cavity in 54, oropharynx in 82, larynx in 20, and hypopharynx in 32 cases, respectively. Patients' stages were predominantly T3 and T4 (158/188, 84%) and most patients had lymph node metastases (144/188, 77%) at diagnosis. Only 22 patients were female, 166 were male, the median age of patients was 57 years (range 34 to 76 years). Patients were randomized to one of the following three treatment options: conventional fractionation (CF) consisting of 70 Gy in 35 fractions over 7 weeks (65 patients) or continuous hyperfractionated accelerated radiation therapy (V-CHART; 62 patients) or continuous hyperfractionated accelerated radiation therapy with 20 mg/sqm MMC on day 5 (V-CHART + MMC; 61 patients). By the accelerated regimens, the total dose of 55.3 Gy was delivered within 17 consecutive days, by 33 fractions. On day 1, a single dose of 2.5 Gy was given, from day 2 to 17 a dose of 1.65 Gy was delivered twice: the interfraction interval was 6 hours or more. RESULTS: Mucositis was very intense after accelerated therapy, most patients experiencing a grade III/IV reaction. The mucosal reaction did not differ whether MMC was administered or not. Patients treated by accelerated fractionation experienced a confluent mucosal reaction 12-14 days following start of therapy and recovered (no reaction) within 6 weeks. The skin reaction was not considered different in the three treatment groups. Those patients treated with additional chemotherapy experienced a grade III/IV hematologic toxicity in 12/61 patients. Initial complete response (CR) was recorded in 43% following CF, 58% after V-CHART, and 67% after V-CHART + MMC, respectively (p < 0.05). Actuarial survival (Kaplan-Meier) was significantly improved in the combined treated patients. Local tumor control was 28%, 32%, and 56% following CF, V-CHART, and V-CHART + MMC, respectively (p < 0.05). CONCLUSION: We conclude that our continuous hyperfractionated accelerated radiation therapy regimen is equal to conventional fractionation, suggesting that by shortening the overall treatment time from 7 weeks to 17 days a reduction in dose from 70 Gy to 55.3 Gy is possible, with maintenance of local tumor control rates. The administration of MMC to the accelerated regimen is tolerable and improves the outcome for patients significantly.

Adult↗
PubMed2000

SOS induction of the recA gene by UV-, gamma-irradiation and mitomycin C is mediated by polyamines in Escherichia coli K-12.

Polyamines are involved in a wide range of cellular metabolism. In this study we investigated the effects of polyamines on the SOS induction of the recA gene by exposure to UV-, gamma-irradiation and mitomycin C employing polyamine-deficient mutant and wild type Escherichia. coli strains carrying recA'::'lacZ transcriptional fusion. In the polyamine-deficient mutant, the induction factor of the recA gene by UV-, gamma-irradiation and mitomycin C-treatment are about 3.0-, 2.5- and 4-fold lower, respectively, than those of the wild type. The exogenous addition of polyamines restored the reduced induction of the recA gene to the wild type level. Tri-amine spermidine effectively restored the recA induction to a level similar to the wild type, while being less restored by the di-amine putrescine. The restoration of recA induction by polyamines may be accomplished in a dose- and charge-dependent manner. Our results strongly suggest that polyamines may play an essential role as the SOS inducing mediator following exposure to damaging agents in E. coli and provide important information that tackles an interesting question in how cells respond to chemical and physical stresses.

DNA Repair↗
PubMed1999

Mitomycin C linked to DNA minor groove binding agents: synthesis, reductive activation, DNA binding and cross-linking properties and in vitro antitumor activity.

Mitomycin C (MC) is a natural cytotoxic agent used in clinical anticancer chemotherapy. Its antitumor target appears to be DNA. Upon bioreductive activation MC alkylates and cross-links DNA. MC derivatives were synthesized in which MC was linked to DNA minor groove binding agents, analogous to netropsin and distamycin. One, two and three N-methylpyrrole carboxamide units were conjugated with MC by a (CH2)5-tether to the 7-amino group of MC (11, 12 and 13, respectively). In contrast to MC 11, 12 and 13 displayed non-covalent affinity to DNA. Their bioreductive activation by NADPH-cytochrome c reductase proceeded as fast as that of MC. Metabolites arising from reductive and low-pH activation were characterized and found to be analogous to those of MC. DNA cross-linking activities were weak and decreased with an increasing number of N-methylpyrrole carboxamide units linked with the mitomycin molecule. No adducts were formed with calf thymus DNA in detectable amounts. In vitro antitumor activities of 11-13 were determined using the NCI in vitro antitumor screen. The conjugates 11-13 are growth inhibitory; however, their activities are 1.5-2 orders of magnitude lower than that of MC. COMPARE analysis indicates that the mechanism of the action of 11 and 12 correlates moderately with MC but negatively with distamycin. Conjugate 13 correlates neither with MC nor with distamycin. The results suggest that the basic cause of the observed low activity of the MC-minor groove binder conjugates is the fast irreversible decay of the activated MC, competing effectively with the slow drug delivery to CpG sites, required for the alkylation.

Animals↗
PubMed2001

Sarcomas metastatic to the liver: response and survival after cisplatin, doxorubicin, mitomycin-C, Ethiodol, and polyvinyl alcohol chemoembolization.

PURPOSE: To evaluate the response to and survival after chemoembolization with cisplatin, doxorubicin, mitomycin-C, Ethiodol, and polyvinyl alcohol for patients with sarcomas metastatic to the liver that are surgically unresectable. MATERIALS AND METHODS: Sixteen patients were treated. Primary tumors included 11 gastrointestinal leiomyosarcomas, two splenic angiosarcomas, one leiomyosarcoma of the broad ligament, one leiomyosarcoma of the inferior vena cava, and one malignant fibrous histiocytoma of the colon. Chemoembolization with cisplatin, doxorubicin, mitomycin-C, Ethiodol, and polyvinyl alcohol particles was performed 1-5 times at approximately monthly intervals (mean, 2.8). Pre- and posttreatment cross-sectional imaging was performed 1 month after completion of treatment and then every 3 months. Thirty-day response was graded according to World Health Organization/Eastern Cooperative Oncology Group criteria. Survival was calculated with use of Kaplan-Meier analysis. RESULTS: Two patients (13%) exhibited partial morphologic response, 11 patients (69%) were morphologically stable, and three (19%) demonstrated progression of disease 30 days after completion of treatment. Among the 13 responders, two underwent partial hepatectomy after initial treatment. Seven developed intrahepatic progression at a mean of 10 months and a median time of 8 months. The remaining four patients had no documented intrahepatic progression at the time of last imaging follow-up. Nine patients developed extrahepatic progression at a mean time of 6.3 months and a median time of 6 months, of whom four underwent additional surgical resection. Response to therapy was based on time of first intervention. Cumulative survival from time of diagnosis with use of Kaplan-Meier analysis was 81% at 1 year, 54% at 2 years, and 40% at 3 years. Median survival time was 20 months. Cumulative survival from initial chemoembolization was 67% at 1 year, 50% at 2 years, and 40% at 3 years, with a median survival time of 13 months. The thirty-day mortality rate was zero. CONCLUSION: Durable tumor response with chemoembolization is possible in this form of metastatic disease, which is highly resistant to systemic chemotherapy.

Chemoembolization, Therapeutic↗
PubMed1999

Molecular characterization and analysis of the biosynthetic gene cluster for the antitumor antibiotic mitomycin C from Streptomyces lavendulae NRRL 2564.

BACKGROUND: The mitomycins are natural products that contain a variety of functional groups, including aminobenzoquinone- and aziridine-ring systems. Mitomycin C (MC) was the first recognized bioreductive alkylating agent, and has been widely used clinically for antitumor therapy. Precursor-feeding studies showed that MC is derived from 3-amino-5-hydroxybenzoic acid (AHBA), D-glucosamine, L-methionine and carbamoyl phosphate. A genetically linked AHBA biosynthetic gene and MC resistance genes were identified previously in the MC producer Streptomyces lavendulae NRRL 2564. We set out to identify other genes involved in MC biosynthesis. RESULTS: A cluster of 47 genes spanning 55 kilobases of S. lavendulae DNA governs MC biosynthesis. Fourteen of 22 disruption mutants did not express or overexpressed MC. Seven gene products probably assemble the AHBA intermediate through a variant of the shikimate pathway. The gene encoding the first presumed enzyme in AHBA biosynthesis is not, however, linked within the MC cluster. Candidate genes for mitosane nucleus formation and functionalization were identified. A putative MC translocase was identified that comprises a novel drug-binding and export system, which confers cellular self-protection on S. lavendulae. Two regulatory genes were also identified. CONCLUSIONS: The overall architecture of the MC biosynthetic gene cluster in S. lavendulae has been determined. Targeted manipulation of a putative MC pathway regulator led to a substantial increase in drug production. The cloned genes should help elucidate the molecular basis for creation of the mitosane ring system, as well efforts to engineer the biosynthesis of novel natural products.

Amino Acid Sequence↗
PubMed2002

A comparison between mouse and fish micronucleus test using cyclophosphamide, mitomycin C and various pesticides.

A comparative analysis between mouse and fish erythrocyte micronuclei (MN) assays was carried out using cyclophosphamide, mitomycin C and various pesticides such as alliete, brestanid, decis 25 CE (deltamethrin), kelthane 480 CE (dicofol), roundup (glyphosate), imazapyr and thiram. The aim of this study was to evaluate the fish species Tilapia rendalli as a suitable organism for the detection of genotoxicants in water. The clastogens cyclophosphamide and mitomycin C induced MN in both test-systems. Insecticides: decis 25 CE increased T. rendalli MN frequencies at doses of 1.0 and 5.0mg/kg, but not at the highest dose, and in mice there was no MN induction. Kelthane 480 CE also induced a significant MN frequency in T. rendalli, but not in mice. Fungicides: alliete and brestanid induced MN only in T. rendalli, while thiram was negative in both assays. Herbicides: imazapyr induced MN in T. rendalli at the maximum tolerated dose only, while roundup induced MN at three dosed levels. In mice both herbicides presented negative results. This study revealed that fish MN assay can be used as a genotoxicological test-system since some methodological particularities were observed.

Animals↗
PubMedDate not supplied

Topical mitomycin C effect on swine vocal folds healing.

UNLABELLED: Several adjuvant therapies to surgery have been used to modulate the healing process of vocal folds, including topic mitomycin (MTC). AIM: to evaluate the effect of topical MTC in the healing process of vocal folds 30 days after the exeresis of a mucosal fragment with CO2 laser in a swine model (control group without mitomycin and study group with topical MTC), with collagen deposition measurement. STUDY TYPE: prospective experimental in swine. METHODS: two groups of 6 swine each were subjected to exeresis of a mucosal fragment of the vocal fold with CO2 laser. Immediately after the procedure MTC was applied topically for three minutes on the study group. Thirty days later the animals were slaughtered and samples of the vocal folds were collected for histological analysis, with the purpose of quantifying collagen deposition by Picrosirius Red stain. RESULTS: the average area of total collagen in the vocal folds in the control group was 2.648,03 microm2, whereas in the study group it was 2.200,30 microm2 (p=0.0043). CONCLUSION: topical application of MTC after the exeresis of a mucous fragment of vocal fold with CO2 laser in swine significantly decreased total collagen deposition.

Administration, Topical↗
PubMedDate not supplied

Antisense sequence-directed cross-linking of DNA oligonucleotides by mitomycin C.

Oligodeoxyribonucleotides (ODNs) conjugated with mitomycin C (MC) via (-CH2-)n tethers of different lengths (n = 6, 12) to their terminal 5'-phosphate were synthesized, and their interaction with target complementary single-stranded DNA oligonucleotides was investigated. MC, a clinically used natural anticancer drug, is known to act as a bioreductive alkylating agent of duplex DNA with a remarkable preference for 5'-d(CG) sequences. The usual enzymatic bioreductive techniques known to trigger MC to alkylate DNA were employed in the reaction between the MC-oligonucleotide conjugates and their targets radiolabeled by 32P at their 5'-phosphate. A slow-moving radiolabeled product, detected by polyacrylamide gel electrophoresis using phosphorimaging techniques, was obtained in 15-25% yield with complementary DNA as target. Formation of these products was dependent upon complementary duplex formation. Evidence is presented that the DNA target is alkylated by the mitomycin C moiety of the ODN conjugate at the 2-amino group of a guanine base. These findings suggest that the MC-ODN conjugates may be useful specific inhibitors of cellular or viral gene expression. To our knowledge this is the first report on ODN conjugates of a reductively activated drug of known therapeutic value.

Base Sequence↗
PubMed1995

Binding of 2,7-diaminomitosene to DNA: model for the precovalent recognition of DNA by activated mitomycin C.

Mitomycin C (MC), mitomycin A, porfiromycin, BMY-25067, and BMY-25287, antitumor antibiotics collectively termed "mitosanes", were found to have no appreciable binding affinity to various natural and synthetic DNAs, as tested by UV spectrophotometry and equilibrium dialysis. Further tests of DNA binding applied to MC including thermal melting measurements, displacement of ethidium fluorescence, and unwinding of closed circular DNA were similarly negative. In contrast, 2,7-diaminomitosene (2,7-DAM), a major end product of the reductive activation of MC, binds to the same series of DNAs by all of these criteria. In the presence of DNA its UV absorbance at the 313 nm maximum decreased and underwent a slight red shift. This effect was used for determining DNA binding constants (Kb) by the spectrophotometric titration method. At pH 6.0 the Kbs of three natural DNAs with varying GC content, as well as poly(dA-dT).poly(dA-dT), and poly(dG-dC).poly(dG-dC), were all in the range of (1.2-5.3) x 10(4) (M nucleotide)-1, with no apparent specificity of binding. Poly(dG-m5dC).poly(dG-m5dC) displayed a slightly higher Kb ((7.5-8.4) x 10(4)). Binding of other, closely related mitosenes was tested to calf thymus DNA by equilibrium dialysis. Neither the presence of a 1-OH substituent, removal of the 10-carbamoyl group, nor methylation of the 2-amino group modifies the binding affinity of the mitosenes significantly. The 1-phosphate substituent abolishes binding. The binding of 2,7-DAM to DNA increased with decreasing pH and decreasing ionic strength. It was determined that 2,7-DAM is protonated at the 2-amino group with a pKa = 7.55, and this correlated well with the observed pH dependence of the binding, indicating that the binding affinity has a strong electrostatic component. This was confirmed by the finding that the extrapolated Kb to 1 M Na+ concentration diminishes to only 10% of the value of Kb at 0.01 M Na+ concentration. Viscosity tests showed conclusively that 2,7-DAM intercalates in DNA, in a nonspecific manner. DNA binding by 2,7-DAM is shown to be a close model of the binding of the reduced activated form of MC, previously characterized indirectly [Teng, S. P., Woodson, S. A., and Crothers, D. M. (1989) Biochemistry 28, 3901-3907]. The nonspecific precovalent binding of the active form may serve in the cell to concentrate the drug at its critical target, DNA.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

Isolation and structure of an intrastrand cross-link adduct of mitomycin C and DNA.

A new covalent mitomycin C-DNA adduct (4) was isolated from DNA exposed to reductively activated mitomycin C (MC) in vitro. The MC-treated DNA was hydrolyzed enzymatically under certain conditions, and the new adduct was isolated from the hydrolysate by HPLC. Its structure was determined by ultraviolet and circular dichroism spectroscopy and chemical and enzymatic transformations conducted on microscale. In the structure, a single 2" beta, 7"-diaminomitosene residue is linked bifunctionally to two guanines in the dinucleoside phosphate d(GpG). The guanines are linked at their N2 atoms to the C1" and C10" positions of the mitosene, respectively. A key to the structure was a finding that removal of the mitosene from the adduct by hot piperidine yielded d(GpG); another was that the adduct was slowly converted to the known interstrand cross-link adduct 3 by snake venom diesterase and alkaline phosphatase. Adduct 4 represents an intrastrand cross-link in DNA formed by MC. Of the two possible strand-polarity isomers of 4, 4a in which the mitosene 1"-position is linked to the 3'-guanine of d(GpG) is designated as the proper structure, on the basis of the mechanism of the cross-linking reaction. The same adduct 4 was isolated from poly(dG).poly(dC), synthetic oligonucleotides containing the GpG sequence, and Micrococcus luteus and calf thymus DNAs. The relative yields of interstrand and intrastrand cross-links (3 and 4) were determined under first-order kinetic conditions; an average 3.6-fold preference for the formation of 3 over that of 4 was observed. An explanation for this preference is proposed.(ABSTRACT TRUNCATED AT 250 WORDS)

Alkylation↗