Tissue differences but limited sex steroid responsiveness of c-fos and c-jun in human fibroids and myometrium.

Sex steroids influence the growth of mammalian uterine tissues and the proto-oncogenes c-fos and c-jun have been implicated in the cascade of cellular events induced by the cyclic influence of oestrogen and progesterone. To investigate the role of these proto-oncogenes for fibroid growth their mRNA expression was measured in myometrium and fibroids under different hormonal conditions, using a solution hybridization method. Fibroids and myometrium were collected at surgery from premenopausal, postmenopausal and pregnant women as well as women treated with a gonadotrophin releasing hormone agonist (GnRHa; Goserelin). The phase of the menstrual cycle was determined in all the untreated, premenopausal, non-pregnant women. The mRNA expression of c-fos and c-jun in fibroids was significantly lower than in homologous myometrium. No significant differences in c-fos expression were observed in myometrium, or fibroids, due to menstrual cycle phase, GnRHa treatment, pregnancy or the menopause. The c-jun expression in myometrium from pregnant women without fibroid disease was significantly higher than the corresponding control myometrium from premenopausal, non-pregnant women. These results demonstrate a tissue difference in the expression of c-fos and c-jun between myometrium and fibroids.