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A Mitomycin C-resistant Jensen Rat Sarcoma: Isolation and Transplantation Studies^*

( Division of Tumor Biology, Sloan-Kettering Institute for Cancer Research, Sloan-Kettering Division, Graduate School of Medical Sciences, Cornell University, New York, New York)

A transplantable rat tumor, the Jensen sarcoma, has been selected for resistance to the action of mitomycin C. Initial treatment consisted of 0.15 mg/kg. After seven passages through rats, the treatment dose was raised to 0.5 mg/kg. Under normal circumstances, this dose of antibiotic completely inhibits tumor growth. The stability of this resistance was proved by passage of the tumor through more than twenty generations in untreated rats.

The antibiotic-resistant tumor was also found to have the following characteristics: (a) growth as a firm mass with less necrosis and central liquefaction than is ordinarily observed in the sensitive sarcoma; (b) a greater tendency to persist for longer periods of time in the rat host before showing drastic signs of regression; (c) a slow growth rate in cortisone-treated Swiss mice; (d) poor transplantability to neonatal mice; and (e) cross-resistance to nitrogen mustard in tests with the cortisone-treated Swiss mouse.

^* This study was supported in part by research grant CY-3784 from the National Cancer Institute, National Institutes of Health, U.S. Public Health Service, Bethesda, Maryland; in part by contracts SA-43-ph-1923 and SA-43-ph-2445 from the Cancer Chemotherapy National Service Center, Silver Springs, Maryland.

Received 4/16/62.