because hormones of pregnancy are thought to alter the mammary gland such that the epithelial cells are less susceptible to future carcinogenic insults , the present study was conducted to determine the ability of short-term treatment with 17 beta-estradiol and/or progesterone , administered immediately after puberty , to prevent mammary cancers in rats subsequently exposed to n-nitroso-n-methylurea [ ( nmu ) cas:684-93-5 ] .
C0039869
thought
C0004927
conducted