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Epidermal growth factor-responsive and -refractory carcinomas initiated with N-methyl-N-nitrosourea in rat urinary
K Fujimoto1, Y Tanaka, A Rademaker
1Department of Pathology, Northwestern University Medical School, Chicago, Illinois 60611-3008, USA.
Abstract:
We tested the role of epidermal growth factor (EGF) in the development of low-grade superficial bladder tumors by using a heterotopically transplanted rat urinary bladder system. Weekly EGF administration (250 ng/0.5 ml of phosphate-buffered 2.1% NaCl solution) for 28 weeks into heterotopically transplanted rat urinary bladders initiated with a low dose of N-methyl-N-nitrosourea resulted in a significant increase in the incidence (17 of 25 versus 6 of 30 rats; P < 0.001) and the mean number of tumors per bladder (1.08 versus 0.20; P < 0.001) as compared with those for a vehicle-only group. Changing to vehicle without EGF for the last 8 weeks resulted in tumors in 8 of 24 rats (P = 0.02 versus the EGF group), comparable to the rate for controls. Switching from vehicle to EGF for the last 8 weeks resulted in tumors in 15 of 24 rats, comparable to the rate in the 28-week EGF group. When tumors were divided into two groups according to size (>4.2 mm3 and