Tumors of the heart and stomach induced in European hamsters by intravenous administration of N-methyl-N-nitrosourea

Atorvastatin has cardiac safety at intensive cholesterol-reducing protocols for long term, yet its cancer-treatment doses with chemotherapy may cause cardiomyopathy even under coenzyme-Q10 protection

Statins provide strong clinical benefits via reducing stroke deaths, and they are also considered for tumor reduction and chemo-sensitization. High dose atorvastatin in adults (80 mg daily, approx. 1 mg/kg) is proven to afford greater protection against cardiac deaths than does a standard lipid-lowering dose in coronary syndrome. For cancer trials, mega doses up to 30 mg/kg have been used for short term treatments but neither a high nor a mega-dose of atorvastatin has been tested for long term cardiac safety. This may be of special concern, since some animal studies showed deleterious effects of statins on cardiac tissue, which may be related with coenzymeQ (CoQ) depletion. We performed an electron microscopic analysis of rat hearts after low, high-or mega-dose atorvastatin therapy and with or without MNU (methyl-nitrosourea)-stress. MNU + daily high dose atorvastatin treatment for 13 months did not produce severe cardiac toxicity with CoQ. However, at mega doses (30 mg/kg) and with MNU, mitochondrial damage and myofibrillary disintegration was obvious. Strong proliferation of mitochondria under high dose atorvastatin therapy with CoQ may explain the lack of cardiotoxicity; and this finding seems to parallel recent data that statins induce HNF-4 and PPAR-alpha, both responsible for mitochondria-proliferation. Employment of statins for tumor chemo-sensitization at high-dosage and for long term treatments may require strategies to direct the mevalonate-entry differentially into cardiac and tumor cells and to develop a protocol analogous to folic acid salvage of methotrexate toxicity.

The effect of intraperitoneal N-methyl-N-nitrosourea on hamster palatal gingiva and intermolar mucosa

Fifty 4- to 6-week-old male random-bred golden hamsters were injected intraperitoneally with a weight-related dose (12.5 mg/kg body weight) of N-methyl-N-nitrosourea (NMU) three times a week for 4 weeks. Groups of seven animals were killed 10, 16 and 22 weeks after the first injection. The palatal gingiva from six animals and the intermolar mucosa from 21 animals was examined. Seven male age-matched untreated control animals were killed at each period. Although all NMU-treated hamsters showed dysplastic and neoplastic changes similar to those in human oral squamous-cell carcinoma, other changes such as acantholytic dyskeratosis, invading cysts, duct-like structures and basaloid islands and cords were not. The extent and severity of the changes increased with time so that by 22 weeks there was extensive involvement of the palatal bone and marrow spaces, the molar periodontal ligament and the greater palatine neurovascular bundle by neoplastic epithelium. The invading epithelium was derived from the junctional, crevicular and palatal gingival and intermolar epithelium. The latent period for the crevicular and junctional epithelia was shorter than that for the palatal gingival and intermolar epithelium. The invasive changes from the latter epithelium were often preceded by exophytic changes such as epithelial projections, papillae and papillomas. Such changes were infrequent for the gingival, crevicular and junctional epithelia. The study shows that intraperitoneal NMU acts as a complete carcinogen on the palatal gingival and intermolar epithelium in hamsters.

The carcinogenic effect of 1,1-diethyl-3-methyl-3-nitrosourea in European hamsters

Laboratory-bred European hamsters received subcutaneous injections of 1,1-diethyl-3-methyl-3-nitrosourea once weekly for life. The animals developed mainly squamous cell carcinomas of the nasal and oral cavities and malignant sarcomas (schwannomas) of the glandular stomach. The average tumour latency was shorter in females (24 weeks) than in males (28 weeks), while tumour incidence was 80% for both sexes.