Control of cell proliferation by steroids: the role of 17HSDs

Sex steroid hormone signaling regulates the development, growth, and functioning of the breast and the prostate and plays a role in the development and progression of cancer in these organs. The intracellular concentration of active sex steroid hormones in target tissues is regulated by several enzymes, including 17beta-hydroxysteroid dehydrogenases (17HSDs). Changes in the expression patterns of these enzymes may play a pathophysiological role in malignant transformation. We recently analyzed the mRNA expressions of the 17HSD type 1, 2, and 5 enzymes in about 800 breast carcinoma specimens. Both 17HSD type 1 and 2 mRNAs were detected in normal breast tissue from premenopausal women but not in specimens from postmenopausal women. The patients with tumors expressing 17HSD type 1 mRNA or protein had significantly shorter overall and disease-free survival than the other patients. The expression of 17HSD type 5 was significantly higher in breast tumor specimens than in normal tissue. Cox multivariate analyses showed that 17HSD type 1, tumor size, and estrogen receptor alpha (ERalpha) had independent prognostic significance. We developed, using a LNCaP prostate cancer cell line, a model to study the malignant transformation of prostate cancer and showed that androgen-sensitive LNCaP cells are transformed into neuroendocrine-like cells when cultured without androgens and, eventually into highly proliferating androgen-independent cells. We conducted Northern hybridizations and microarrays to analyze the gene expression during these processes. Substantial changes in the expressions of steroid metabolizing enzymes occurred during the transformation process. The variations in steroid-metabolizing enzymes during cancer progression may be crucial in the regulation of the growth and function of organs.