Dose Of Mitomycin C Research Articles

Cystic bleb formation and related complications in limbus- versus fornix-based conjunctival flaps in pediatric and young adult trabeculectomy with mitomycin C

Objective Comparison of fornix- and limbus-based conjunctival flaps with respect to cystic bleb-related complications of trabeculectomy with high-dose mitomycin C (MMC) in pediatric and young adult glaucoma. Design Retrospective nonrandomized comparative interventional case series. Participants Thirty-seven patients. Methods Identification of patients aged <30 years from operating theater records from 1995 and 1996 of the Moorfields Pediatric Glaucoma Service who had trabeculectomy with an MMC concentration of ≥0.4 mg/ml. Over a 2-year period, 37 consecutive operations matching these criteria were performed by a single surgeon: 20 with a limbus-based flap and 17 with a fornix-based flap. Except for the conjunctival incision and associated alteration in antimetabolite application and wound closure, the surgical technique was not significantly different between the groups. Main outcome measures Bleb evolution and complications. Results The age at time of surgery, MMC concentration, history of one or more previous surgeries, and follow-up were similar in the 2 groups. The risk of cystic bleb formation was greater in the limbus-based flap group (90% in the limbus-based group vs. 29% in the fornix-based group; P<0.001). Late hypotony and bleb-related ocular infection were more common in the limbus-based flap group ( P<0.05) and occurred earlier. There were four episodes of bleb-related infection (20%) in the limbus-based group (three of these [15%] were bleb-related endophthalmitis) and none in the fornix-based group. Conclusions In pediatric and young adult trabeculectomy with high doses of MMC, limbus-based flaps may be more likely to develop serious bleb-related complications and may develop these earlier than fornix-based flaps. The higher rates of complications could be attributable to the differences in bleb morphology, with limbus-based flap cases more likely to develop cystic blebs.

Potentiation of photodynamic therapy with hypericin by mitomycin C in the radiation-induced fibrosarcoma-1 mouse tumor model.

Hypericin, a polycyclic quinone obtained from plants of the genus Hypericum, has been shown to be a promising photosensitizer. We investigated the combination of hypericin-photodynamic therapy (PDT) and a bioreductive drug mitomycin C (MMC) in the present study. The radiation-induced fibrosarcoma-1 tumors were exposed to laser light (120 J/cm2 at 595 nm) 24 h after an intravenous injection of hypericin (1 mg/kg). Hypericin-PDT alone significantly decreased tumor perfusion and oxygen tension as demonstrated by India ink staining technique and OxyLite pO2 measurement, respectively. The in vivo-in vitro cell-survival assay revealed about 60% direct tumor cell killing immediately after PDT. No significant delayed tumor cell death was observed after PDT, which suggests that vascular damage does not contribute significantly to the overall tumor cell death. Injection of a 2.5 mg/kg dose of MMC 20 min before light application significantly decreased tumor cell survival and delayed tumor growth compared with PDT or MMC alone. No greater skin reaction was observed after the combination of MMC and PDT than after PDT alone. Our study demonstrates that combining hypericin-PDT with MMC can be effective in enhancing tumor response with little side effect.

Effect of mitomycin-C on the bioavailability of the radiopharmaceutical (99m)technetium-phytic acid in mice: a model to evaluate the toxicological effect of a chemical drug.

The many desirable characteristics of technetium-99m ((99m)Tc) have stimulated the development of labelling techniques for different molecular and cellular structures. It is generally accepted that a variety of factors can alter the biodistribution of radiopharmaceuticals and one such factor is drug therapy. Because patients on chemotherapeutic treatment receive a radiopharmaceutical in a nuclear medicine procedure, we have studied in Balb/c mice the effect of mitomycin-C on the biodistribution of the radiopharmaceutical (99m)Tc-phytic acid ((99m)Tc-PHY) used in hepatic scintigraphy. Mitomycin-C is an antineoplastic agent obtained from Streptomyces caesptosus and is used on the treatment of disseminated adenocarcinoma of the stomach or pancreas. Three doses of mitomycin-C were administered via the ocular plexus into Balb/c mice. One hour after the last dose, (99m)Tc-PHY was administered and the animals were sacrificed. The organs were isolated, the radioactivity was determined in a well counter and the percentages of radioactivity in the organs were calculated. The results have shown that the percentage radioactivity has been increased in stomach, spleen, lung, thyroid and bone, decreased in pancreas and thymus and not altered in ovary, uterus, kidney, heart, liver and brain. The changes in the distribution of (99m)Tc-PHY may be the result of metabolic processes and/or therapeutic actions produced by the administration of mitomycin-C.

Survival and induction of SOS in Escherichia coli treated with cisplatin, UV-irradiation, or mitomycin C are dependent on the function of the RecBC and RecFOR pathways of homologous recombination

Resistance of tumors to drugs such as cisplatin and mitomycin C (MMC) is an important factor limiting their usefulness in cancer chemotherapy. The antitumor effects of these drugs are due to the formation of bifunctional adducts in DNA, with cisplatin causing predominantly intrastrand-crosslinks and MMC causing interstrand-crosslinks. The SOS chromotest was used to study the cellular mechanisms that process DNA damage in Escherichiacoli exposed to cisplatin, ultraviolet irradiation (UV) and MMC and subsequently facilitate the production of a molecular signal for induction of the SOS response. Strains used in the SOS chromotest have a fusion of lacZ with the sfiA (sulA) gene so that the amount of SOS inducing signal, which is modulated by the ability of the cell to repair DNA, is measured by assaying β-galactosidase activity. SOS induction in a strain proficient in homologous recombination (HR) was compared with that in isogenic strains deficient in HR due to a blocked RecBC pathway caused by a recB mutation or a blocked RecFOR pathway caused by a recO mutation. The effect of cisplatin treatment in a uvrA mutant strain blocked at the first step of NER was compared with that in an isogenic strain proficient in NER. Cellular resistance was measured as percent colony forming units (cfu) for cells treated with increasing doses of cisplatin, MMC and UV relative to that in untreated control cultures. The importance of both HR pathways for resistance to these treatments was demonstrated by decreased survival in mutants with the recB mutant being more sensitive than the recO mutant. SOS induction levels were elevated in the sensitive recB strain relative to the HR proficient strain possibly due to stalled and/or distorted replication forks at crosslinks in DNA. In contrast, induction of SOS was dependent on RecFOR activity that is thought to act at daughter strand gaps in newly synthesized DNA to mediate production of the signal for SOS induction. Proficiency in NER was necessary for both survival and high levels of SOS induction in cisplatin treated cells.

Irinotecan and Mitomycin C in 5-Fluorouracil-Refractory Colorectal Cancer Patients

Purpose: To define the maximum tolerated dose (MTD) of irinotecan (CPT-11) given on days 1 and 8 with mitomycin C (MMC) given on day 1 in a monthly cycle, and to assess the toxicity and activity of this regimen in patients with previously treated colorectal carcinoma. Methods: Fifty-two patients, all pretreated with adjuvant 5-fluorouracil (20 patients) and/or one (35 patients) or two (8 patients) lines of chemotherapy, were entered in this study. Escalating doses of CPT-11 (starting from 150 mg/m²) were administered on days 1 and 8, with escalating doses of MMC (starting from 8 mg/m²) given on day 1, recycling every 28 days. At least 3 patients were treated at each dose level. Escalation proceeded unless 2 out of 3 or 4 out of 6 patients experienced a dose-limiting toxicity (DLT) after the first cycle. Results: Twelve patients were entered in the phase I study, and 4 consecutive dose levels were tested. At the last dose level (CPT-11 200 mg/m² plus MMC 10 mg/m²) 4 of 6 patients experienced a DLT (i.e., grade 4 neutropenia in 2 patients and grade 3 diarrhea in 2 patients). Therefore, this dose level was considered as the MTD. Forty patients were treated at the previous dose level (CPT-11, 175 mg/m² plus MMC 10 mg/m²). One complete, 4 partial, 3 minor responses and 11 cases of stable disease were registered, giving a response rate of 12% [95% confidence interval (CI), 4–27%] and an overall control of tumor growth in 47% (95% CI, 31–64%) of patients. The median time to treatment failure was 6 months (range 1–19+). The median survival time was 14.5 months, and the 1-year and 2-year probability of survival were 56 and 43%. Neutropenia and diarrhea affected 62 and 58% of patients, grade 3 or 4 being registered in 26 and 23% of them, respectively. One episode of neutropenic fever was reported. Other acute toxicities were usually mild and manageable. Conclusions: CPT-11 175 mg/m² on days 1 and 8 associated with MMC 10 mg/m² on day 1, every 4 weeks, is a safe and moderately active regimen in heavily pretreated patients with advanced colorectal carcinoma. The role of MMC in this combination is doubtful, and further attempts with other new agents should be made to improve the outcome in these patients.

Mitomycin C Influence on Inhibition of Cellular Proliferation and Subsequent Synthesis of Type I Collagen and Laminin in Primary and Recurrent Pterygia

The purpose was to investigate the biological effects of mitomycin C (MMC) on the inhibition of cellular proliferation and the subsequent synthesis of extracellular matrix like type I collagen (PIP) and laminin on primary and recurrent pterygia. The ³H-thymidine assay for cellular proliferation was consistent with the MMC dose and time response of both pterygia. The cellular inhibitory effect of MMC was greater on recurrent pterygial cells than primary ones. The inhibition of laminin by MMC followed the dose and time-response curves, with a stronger effect found in recurrent pterygial cells, but no significant difference between the two types concerning type I collagen synthesis. The inhibition of fibroblast proliferation and subsequent synthesis of laminin by MMC was more marked in recurrent pterygium than the primary one.

Mitomycin C as an alternative to irradiation to inhibit the feeder layer growth in long-term culture assays

Mitomycin C (MMC), an antitumoral antibiotic, has been described inhibiting the proliferation of different cell types in vitro. Since irradiation is commonly used to stop the cell growth of adherent cells in several experimental models, we aimed to define the optimal dose and incubation time of MMC capable of inhibiting the growth of murine fibroblasts, used as an adherent feeder layer in long-term hematopoietic culture assay. M2 10B4 (both parental and engineered to produce human IL-3 and G-CSF) and Sl/Sl (engineered to produce human IL-3 and steel factor) murine fibroblast cell-lines, frequently used in LTC-IC assay, were incubated with increasing doses of MMC for either a short (3 h) or a long (16 h) period. The efficiency of MMC in stopping the cell growth was evaluated for 5 days following MMC removal. The effects of MMC treatment on human hematopoietic cells were studied using both LTC-IC and limiting dilution (CAFC) assays. The growth of M2 10B4 cells was stopped at 3 and 16 h in the presence of 20 microg/mL and 2 microg/mL of MMC, respectively while Sl/Sl fibroblasts required a lower dose of drug (2 and 0.2 microg/mL, respectively). No significant difference was found between the number of LTC-IC or CAFC obtained from cultures containing irradiated or MMC-treated feeder cells. MMC inhibits the growth of murine fibroblasts used as adherent feeder cells in long-term culture assays, without interfering with the subsequent growth of co-cultured hemopoietic cells. Different cell types might present a different sensitivity to MMC and therefore a dose-response curve to MMC has to be obtained for each cell type of interest.

Involvement of apoptosis in mitomycin C hypersensitivity of Chinese hamster cell mutants

To elucidate the mechanisms of the mammalian cell defense against cross-linking agents, we studied previously cellular responses to mitomycin C (MMC) treatment in two MMC-hypersensitive hamster cell mutants’ V-H4 and V-C8, as well as their parental cell line V79. In the present report, we investigated whether alterations in cell cycle checkpoints and induction of apoptosis could be responsible for the MMC hypersensitivity of the V-H4 and V-C8 mutant cell lines. First, we found that parental and mutant cells exhibited similar cell cycle responses to MMC concentrations of equivalent cytotoxicity, arguing against a defective cell cycle checkpoint in hypersensitive cell lines. In contrast, we showed that mutant cells underwent greater levels of apoptosis following MMC treatment than parental cells. These findings indicate that increased induction of apoptosis contributes to the hypersensitivity of V-H4 and V-C8 cells to the growth inhibitory effect of MMC. This differential apoptotic response was observed with both equimolar and equitoxic MMC doses and was specific to the cross-linking agent MMC, suggesting that control of the apoptotic process is altered in both MMC-hypersensitive mutants. The defective genes in V-H4 and V-C8 cells would then function in the regulation of an apoptotic pathway triggered by MMC-induced damage and independent of p53-mediated transcription.

Combined therapy with chemotherapeutic agents and herpes simplex virus type 1 ICP34.5 mutant (HSV-1716) in human non-small cell lung cancer.

A replication-selective herpes simplex virus type 1 ICP34.5 mutant (HSV-1716) has shown efficacy both in vitro and in vivo against human non-small cell lung cancer (NSCLC) cell lines but complete eradication of tumor has not been accomplished with a single viral treatment in our murine xenograft models. Therefore, strategies to enhance the efficacy of this treatment were investigated. We determined the oncolytic activity of HSV-1716 in NCI-H460 cells in combination with each of four chemotherapeutic agents: mitomycin C (MMC), cis-platinum II (cis-DDP), methotrexate (MTX), or doxorubicin (ADR). Isobologram analysis was performed to evaluate the interaction between the viral and chemotherapeutic agents. The oncolytic effect of HSV-1716 in combination with MMC was synergistic in two of five NSCLC cell lines. In the other three cell lines, the combined effect appeared additive. No antagonism was observed. The in vivo effect of this combination was then examined in a murine xenograft model. NCI-H460 flank tumors were directly injected with HSV-1716 (4 x 106 PFU) followed by intravenous MMC administration (0.17 mg/kg) 24 hr later. After 3 weeks, the mean tumor weight in the combined treatment group was significantly less than either individual treatment in an additive manner. The synergistic dose of MMC neither augmented nor inhibited viral replication in vitro and HSV-1716 infection did not upregulate DT-diaphorase, which is the primary enzyme responsible for MMC activation. In summary, the combination of HSV-1716 with common chemotherapeutic agents may augment the effect of HSV-based therapy in the treatment of NSCLC.

The Effect of Hydroxyurea on Rabbit Subconjunctival Fibroblast Culture and Use of Hydroxyurea in Rabbits after Glaucoma Filtration Surgery

In an in vitro study, rabbit subconjunctival fibroblasts were cultured and the effects of an antineoplastic drug, hydroxyurea (HU), on fibroblast proliferation and fibroblast attachment was investigated. The effects of HU were compared with those of mitomycin C (MMC). Different concentrations of HU and MMC were added to culture medium. The HU doses which led to 50% of inhibition (ID₅₀) and the dose which led to about 90% of inhibition (subtoxic high dose, STHD) were determined to be 8 and 1,000 μg/ml, respectively. ID₅₀ of MMC and its STHD which led to about 100% inhibition were found to be 0.01 and 1 μg/ml, respectively. Reversibility studies revealed that inhibition disappeared depending on the dose and incubation period of both HU and MMC. In an in vivo study, glaucoma filtration surgery (GFS) was performed in rabbits which were treated with HU (treatment group) and distilled water (control group). Tissue samples were taken from the subconjunctival area treated at 1 h, 1 day, 5 days and 30 days postoperatively. The biopsy specimens were then placed in tissue culture media. Fibroblast outgrowth rates detected in the HU group were found to be significantly lower than those in the control group in the specimens taken at the end of the first hour. The difference was significant on culture days 9–15 in the biopsy specimens taken on day 1 while it was not significant in those taken on days 5 and 30.

The effect of mitomycin-C on the biodistribution of 99Tcm-MDP in Balb/c mice

Drug therapy can alter the biodistribution of radiopharmaceuticals. We studied the effect of mitomycin-C, a drug used in oncology, on the biodistribution in mice of 99Tcm-methylene diphosphonic acid (99Tcm-MDP). Three doses of mitomycin-C were administered. After the last dose, 99Tcm-MDP was injected and the animals were killed. The organs were isolated, their weight determined and the percent per gram injected dose (%ID/g) calculated. The %ID/g had increased in the pancreas, ovary, stomach, uterus, kidneys, spleen, thymus, heart, liver and lungs, but did not change significantly in thyroid, bone or brain. As a change in 99Tcm-MDP uptake by bone is not observed, a modification to bone scintigraphy is not required. As mitomycin-C treatment altered 99Tcm-MDP uptake in some organs, any hot spots should be evaluated carefully to avoid a misdiagnosis.

Effect of the cisplatin-procaine complex DPR in combination with several anticancer agents on murine P388 leukemic cells in vitro and in vivo.

We evaluated in vitro the antiproliferative activity of DPR (Fig. 1), a new cisplatin-derived compound, in combination with five conventional anticancer drugs: the antimetabolites 5-fluorouracil (5FU) and methotrexate (MTX), the alkylating agent mitomycin C (MMC), the antimicrotubule agent taxol (TAX) and the intercalating agent of the antracycline group doxorubicin (DOX), against murine P388 leukemic cells. MTT assay was used to determine growth inhibition after incubation of cells for 72 hours in the presence of single or combined drugs. The additive, synergistic or antagonistic nature of the combined drug effect was determined using the isobole method. In our cellular model, synergism was the prevailing result observed when DPR was combined with MMC. Conversely, antagonism was observed when DPR was combined with TAX. When DPR was administered together with the other antineoplastic drugs, the final effect was dependent on the concentrations of single agents. The study in vitro of the association between DPR and MMC was extended in vivo in BDF-1 female mice bearing i.p. P388 leukemic cells. Our data in vivo confirmed those obtained in vitro, demonstrating the therapeutic advantage of the association of ineffective doses of DPR (2 and 7 mg/kg) and MMC (3.2 mg/kg) over the administration of MMC alone.

The Effect of Mitomycin C on Molteno Implant Surgery

The authors assess whether adjunctive mitomycin C improves Molteno tube shunt surgery in terms of intraocular pressure (IOP), visual acuity, and complication rates. Twenty-five eyes of twenty-five consecutive patients undergoing double-plate Molteno implant surgery were randomized to receive either mitomycin C (MMC) 0.4 mg/mL for 2 minutes or a control balanced salt solution in a masked, prospective study. Intraocular pressure, visual acuity, and complications were recorded 1 week and 1, 3, 6, and 12 months after surgery. A repeated measures analysis of variance (ANOVA) model was used to test the overall effect of the drug on IOP and percent change from preoperative IOP. Thirteen eyes received balanced salt solution and 12 eyes received MMC. There was no difference between the groups with respect to age, preoperative IOP, log mean angle of resolution (LogMar) visual acuity, or number of preoperative medications. Except for week 1, there were no differences between the groups at any of the clinic visits with respect to IOP and percent change from baseline IOP. Analysis of the visual acuity (LogMar) showed reduction in vision for both groups. Complications were similar in each group, as were number of postoperative hypotensive agents required. Adjunct MMC does not demonstrate a significant difference in outcomes compared with placebo in pressure-ridged Molteno implant surgery. Results of this study are limited by a small number of patients in each group and a fixed dose of MMC.

Bone Marrow Failure in the Fanconi Anemia Group C Mouse Model After DNA Damage

Fanconi anemia (FA) is a pleiotropic inherited disease that causes bone marrow failure in children. However, the specific involvement of FA genes in hematopoiesis and their relation to bone marrow (BM) failure is still unclear. The increased sensitivity of FA cells to DNA cross-linking agents such as mitomycin C (MMC) and diepoxybutane (DEB), including the induction of chromosomal aberrations and delay in the G2 phase of the cell cycle, have suggested a role for the FA genes in DNA repair, cell cycle regulation, and apoptosis. We previously reported the cloning of the FA group C gene (FAC) and the generation of a Fac mouse model. Surprisingly, the Fac -/- mice did not show any of the hematologic defects found in FA patients. To better understand the relationship of FA gene functions to BM failure, we have analyzed the in vivo effect of an FA-specific DNA damaging agent in Fac -/- mice. The mice were found to be highly sensitive to DNA cross-linking agents; acute exposure to MMC produced a marked BM hypoplasia and degeneration of proliferative tissues and caused death within a few days of treatment. However, sequential, nonlethal doses of MMC caused a progressive decrease in all peripheral blood parameters of Fac -/- mice. This treatment targeted specifically the BM compartment, with no effect on other proliferative tissues. The progressive pancytopenia resulted from a reduction in the number of early and committed hematopoietic progenitors. These results indicate that the FA genes are involved in the physiologic response of hematopoietic progenitor cells to DNA damage.

Cell Growth Inhibition and DNA Incorporation of Mitomycin C in Cell Culture

The present study was performed to clarify the effects of a 4-min exposure of mitomycin C (MMC) on cell growth, the cell cycle and MMC dose incorporated into DNA, using Chang’s cultured human conjunctival cells. A low dose of MMC ranging from 0.00025 to 0.004% showed dose-dependent cytotoxicity when cell growth was active. Fifty percent cell viability was found when cells were treated with 0.001% MMC. A flow cytometer showed that 0.001% MMC inhibited the DNA synthetic phase. After 0.04% MMC was exposed to 3 ×10⁶ cells and immediately rinsed, DNA was isolated to measure the dose of MMC detected from DNA. The total amount of DNA was 7 µg from which 3 µg of MMC was detected by high performance liquid chromatography. The above results revealed that the lowest concentration of MMC which caused 50% cell viability and cell cycle inhibition was 0.001% and that MMC was rapidly incorporated into DNA.

A prospective randomised trial of protracted venous infusion 5-fluorouracil with or without mitomycin C in advanced colorectal cancer

To compare protracted venous infusion (PVI) 5-fluorouracil (5-FU) with and without mitomycin C (MMC) in a prospectively randomised study and analyse for tumour response, survival, toxicity and quality of life (QL). Two hundred patients with advanced colorectal cancer received PVI 5-FU 300 mg/m2/day for a maximum of 24 weeks and were randomised to PVI 5-FU alone or PVI 5-FU + MMC 10 mg/m2 (7 mg/m2 from June 1995) 6 weekly for 4 courses. Overall response was 54% (95% confidence interval [CI] 44.1%-63.9%) with PVI 5-FU + MMC compared to 38% (95% CI: 28.3%-47.7%) for PVI 5-FU alone (P = 0.024). The median failure free survival was 7.9 months in PVI 5-FU plus MMC and 5.4 months with PVI 5-FU alone (P = 0.033) and at one year 31.9% for the combination compared to 17.7% for PVI 5-FU alone. Median survival was 14 months with MMC and 15 months in 5-FU alone; one-year survival 51.7% vs. 57.2%. PVI 5-FU + MMC caused more overall haematological toxicity but CTC grades 3/4 was increased only for thrombocytopaenia. Two patients treated with a cumulative dose of MMC of 40 mg/m2 developed haemolytic uraemic syndrome warranting the reduction in cumulative MMC dose to 28 mg/m2. The global QL scores were better for PVI 5-FU + MMC arm at 24 weeks, but the remaining QL data showed no differences. PVI 5-FU + MMC results in failure-free survival and response advantage, tolerable toxicity and better QL when compared to PVI 5-FU alone but no overall survival advantage. There is no irreversible toxicity with MMC at a cumulative dose of 28 mg/m2.

Mitomycin lung toxicity. Acute and chronic phases.

Pulmonary toxicity is a rare but well described side effect of mitomycin C (MMC). We describe 14 cases of MMC pulmonary toxicity that were detected in four clinical trials performed at The Mayo Clinic using MMC-containing regimens for nonsmall cell lung cancer (NSCLC) and by reviewing the charts of patients treated at The Mayo Clinic with MMC-containing regimens for NSCLC from 1976 to 1995. The median age was 61 (range 44-84) years, with an M:F ratio of 1:1. The median number of cycles of MMC to develop toxicity was four (range two to five) with a median cumulative dose of MMC of 29 mg/m2. MMC toxicity occurred despite pre-medication with corticosteroids in 11 patients. At diagnosis of MMC lung toxicity, the median diffusing lung capacity (DLCO) was 9 and PaO2 was 49 mm Hg. Of those having bronchoscopy, four patients had pulmonary histologic changes consistent with lung injury. Two patients had bronchioalveolar lavages that were nondiagnostic. All patients responded initially to corticosteroids, but approximately 40% had progressive pulmonary insufficiency despite high doses of corticosteroids. This chronic, progressive phase of MMC lung toxicity is a largely underestimated sequelae of MMC.

Pharmacokinetics of Mitomycin C (MMC) after Intraperitoneal Administration of MMC-Gelatin Gel and Its Anti-tumor Effects against Sarcoma-180 Bearing Mice

Gelatin viscous solution containing mitomycin C (MMC) was prepared and its antitumor effects were evaluated toward sarcoma-180 (S-180) ascite tumor bearing mice. Among various gelatin concentrations, 3% and 5% gelatin solutions potentiated the antitumor effects of MMC (7.5 mg/kg) against S-180 bearing mice. A “bell-shaped” profile was observed between % release of MMC from the gelatin matrix and increased life span (ILS) %. On the other hand, in the case of 10 mg/kg dose of MMC, 7.5% and 10% gelatin solutions potentiated its antitumor effects. At both doses of 7.5 and 10 mg/kg of MMC, decrease in body weight of mice after intraperitoneal administration of MMC were suppressed by increasing the concentration of gelatin. To confirm a possible mechanism for increase in ILS % after intraperitoneal (i.p.) administration of the gelatin viscous solution containing MMC, we examined the pharmacokinetics of MMC after i.p. administration into rats. By the use of 3% gelatin solution, mean residence time (MRT) and Tmax values were significantly prolonged, and Cmax was decreased as compared with the administration of MMC solution. These results suggested that the enhancement of antitumor effect of MMC by the gelatin viscous solution could be caused by decrease in the clearance rate of MMC from the peritoneal cavity to systemic circulation due to decreasing its diffusivity in gelatin matrix.

Anti-tumour activity of photodynamic therapy in combination with mitomycin C in nude mice with human colon adenocarcinoma

The interaction of photodynamic therapy (PDT) and a chemotherapeutic drug, mitomycin C (MMC), was investigated using WiDr human colon adenocarcinoma tumours implanted on Balb/c athymic nude mice. The WiDr tumours were treated with PDT alone, MMC alone or with both. It was found that the combined treatment produced a greater retardation in the growth of the WiDr tumour than monotherapy with MMC or PDT. The synergistic effect was especially prominent when PDT was used in combination with a low dose of MMC (1 mg kg-1), since treatment of 1 mg kg-1 MMC alone had no effect on the tumour. The anti-tumour activity of PDT was found to be increased with MMC of 5 mg kg-1. The response of normal skin on mice feet to PDT slightly greater when PDT was combined with 5 mg kg-1 MMC than when PDT was applied alone, while no detectable additional effect on skin photosensitivity was observed when PDT was combined with 1 mg kg-1 MMC. An enhanced uptake of Photofrin in tumours was found 12 h and 24 h after administration of MMC. The effect of MMC on the cell cycle distribution of cell dissociated directly from the tumours was studied. The results suggest that the increased susceptibility to photoinactivation of Photofrin-sensitised tumours may be due to MMC-induced accumulation of the tumour cells in S-phase.

Preferential effects of the chemotherapeutic DNA crosslinking agent mitomycin C on inducible gene expression in vivo

The immediate effects of a single dose of the chemotherapeutic DNA crosslinking agent, mitomycin C (MMC), on the expression of several constitutive and drug-inducible genes were examined in a simple in vivo system, the 14 day chick embryo. We observed no effect of MMC on the steady-state mRNA expression of the constitutively expressed beta-actin, transferrin, or albumin genes. In contrast, MMC treatment significantly altered both the basal and drug-inducible mRNA expression of two glutethimide-inducible genes, 5-aminolevulinic acid (ALA) synthase and cytochrome P450 CYP2H1. The basal expression of these genes was transiently but significantly increased over a 24 hr period following a single dose of MMC. Conversely, MMC significantly suppressed the glutethimide-inducible expression of these genes when administered 1 to 24 hr prior to the inducing drug. The effects of MMC on both basal and drug-inducible ALA synthase and CYP2H1 mRNA expression were principally a result of changes in the transcription rates of these genes. In contrast, MMC treatment had little or no effect on glutethimide-induced expression of ALA synthase or CYP2H1 when administered 1 hr after the inducing drug, suggesting that a very early event in the induction process represents the target for these MMC effects. Covalent binding studies demonstrated that the effects of MMC on gene expression were closely correlated temporally with formation of [3H]-porfiromycin-DNA adducts. These results support the hypothesis that genotoxic chemicals specifically target their effects to inducible genes in vivo.