Induction of 3 beta-hydroxysteroid dehydrogenase/Delta(5)-Delta(4) isomerase type 1 gene transcription in human breast cancer cell lines and in normal mammary epithelial cells by interleukin-4 and interleukin-13

Sex steroids play a crucial role in the development and differentiation of normal mammary gland as well as in the regulation of breast cancer growth. Local intracrine formation of sex steroids from inactive precursors secrete d by the adrenals, namely, dehydroepiandrosterone and its sulfate, may regu late growth and function of peripheral target tissues, including the breast . Both endocrine and paracrine influences on the proliferation of human bre ast cancer cells are well recognized. Breast tumors harbor tumor-associated macrophages and tumor-infiltrating lymphocytes that secrete a wide spectru m of cytokines. These factors may also contribute to neoplastic cell activi ty. The present study was designed to investigate the action of cytokines o n 3 beta-hydroxysteroid dehydrogenase (3 beta-HSD) activity, which is an es sential step in the biosynthesis of active estrogens and androgens in human breast cancer cell lines and in normal human mammary epithelial cells in p rimary culture. 3 beta-HSD activity was undetectable in ZR-75-1 and T-47D e strogen receptor-positive (ER)(+) cells under basal growth conditions. This activity was markedly induced after exposure to picomolar concentrations o f interleukin (IL)-4 or IL-13. The potent stimulatory effect of these cytok ines on 3 beta-HSD activity was also observed in the ER- MDA-MB-231 human b reast cancer cell line and in normal human mammary epithelial cells (HMECs) in primary culture. The stimulation of 3 beta-HSD activity by IL-4 and IL- 13 results from a rapid increase in 3 beta-HSD type 1 mRNA levels as measur ed by RT-PCR and Northern blot analyses. Such an induction of the 3 beta-HS D activity may modulate androgenic and estrogenic biological responses as d emonstrated using ZR-75-1 cells transfected with androgen- or estrogen-sens itive reporter constructs and treated with the adrenal steroid 5-androstene -3 beta,17 beta-diol. The DNA-binding activity of Stat6, a member of the si gnal transducers and activators of transcription gene family, is activated 30 min after exposure to IL-4 and IL-13 in human breast cancer cell lines a s well as in HMECs in primary culture. In these cells, Stat6 activated by I L-4 or IL-13 binds to two regions of the 3 beta-HSD type 1 gene promoter, c ontaining State consensus sequences. IL-4 induction of 3 beta-HSD mRNA and activity is sensitive to staurosporine. This protein kinase inhibitor also inhibits IL-4-induced State DNA-binding activity. Our data demonstrate for the first time that IL-4 and IL-13 induce 3 beta-HSD type 1 gene expression , thus suggesting their involvement in the fine control of sex steroid bios ynthesis from adrenal steroid precursors in normal and tumoral human mammar y cells. Furthermore, aromatase and/or 5 alpha-reductase(s) are expressed i n the mammary gland and in a large proportion of human breast tumors. An in crease in the formation of their substrates, namely, 4-androstenedione and testosterone, may well have a significant impact on the synthesis of active estrogens and androgens in these tissues.