A series of studies in mice were performed to determine the interaction of two sulfur nucleophiles, oral n-acetylcysteine (NAC) and intravenous sodium thiosulfate (Na₂S₂O₃) with the anticancer drug mitomycin C (MMC). Neither nucleophile reduced MMC lethality or hematopoietic toxicity. Both increased the antitumor activity of MMC in mice bearing P-388 and L-1210 leukemias. There was no nucleophile reduction of MMC effects on normal bone marrow stem cells (CFUs) using a murine spleen colony forming assay. In contrast, the nucleophiles significantly enhanced MMC bone marrow toxicity. Three clonogenic human tumor cell lines (HEC-1A endometrial, 8226 myeloma, WiDr colon) were relatively resistant to MMC and the nucleophiles did not increase activity. A human breast cancer cell line (MCF-7) was sensitive to MMC and this activity was blocked by glutathione. Oxygen free radical scavengers did not reduce MMC activity. A novel isocratic high performance liquid chromatography (HPLC) assay (48:52, methanol:0.01M phosphate buffer) using ultraviolet detection at 365 nm was used to characterize MMC-protein binding and murine pharmacokinetics. The k' for MMC was 7.91 and 9.86 for porfiromycin. Peaks were confirmed by mass spectroscopy. MMC was bound 30% to albumin and S-9 microsomal proteins and 60-70% to calf thymus DNA. MMC uptake into mouse bone marrow was enhanced by the nucleophiles and was rapidly cleared from the plasma (half-life 0.5 hours). In vitro MMC metabolism with rat liver S-9 microsomes demonstrated production of a polar eluting, putative MMC metabolite (K' = 4.486, lambda maximum 300 nm). This metabolite was inactive in the in vitro clonogenic tumor cell assay. Finally, molecular pharmacology studies using alkaline DNA elution showed that MMC causes both DNA-DNA and DNA-protein crosslinks. There was no evidence for free radical-induced DNA strand scission by MMC. There was also some evidence of moderate DNA protection with the sulfur nucleophiles.
| Identifer | oai:union.ndltd.org:arizona.edu/oai:arizona.openrepository.com:10150/187675 |
| Date | January 1984 |
| Creators | Dorr, Robert Thomas |
| Contributors | Alberts, David S. |
| Publisher | The University of Arizona. |
| Source Sets | University of Arizona |
| Language | English |
| Detected Language | English |
| Type | text, Dissertation-Reproduction (electronic) |
| Rights | Copyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author. |
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