P. Pazos et al., PROMOTER EFFECT OF MEDROXYPROGESTERONE ACETATE (MPA) IN N-METHYL-N-NITROSOUREA (MNU) INDUCED MAMMARY-TUMORS IN BALB C MICE/, Carcinogenesis, 19(3), 1998, pp. 529-531
The promoter effect of medroxyprogesterone acetate (MPA) on mammary ca
rcinogenesis in female BALB/c mice was investigated using methylnitros
ourea (MNU) as initiator. Nine out of 43 animals developed mammary car
cinomas in the group treated with MNU (50 mg/kg) and MPA (administrati
on of 40 mg every 3 months) starting 1 week after MNU administration.
No tumors appeared in controls receiving only MNU or MPA during the ti
me course of the experiment (9 months). The tumors were lobular adenoc
arcinomas showing different degrees of squamous differentiation with l
ow or undetectable estrogen and progesterone receptors, and expressing
epidermal growth factor receptors. These results support the hypothes
is that MPA promotes the growth of MNU induced lesions.