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Abstract
Oestrogens and androgens stimulate growth in hormone-dependent breast and prostate cancers respectively. Modern strategies seek to remove the influence of hormones on tumour growth using anti-oestrogens (breast) or anti-androgens (prostate) which block the action of the hormone on its receptor. For prostate cancer patients LHRH (luteinising hormone releasing hormone) agonists, which decrease testes synthesis of testosterone are also used. Newer alternative (or sequential) strategies aim to deplete circulating and tissue levels of the respective mitogenic hormone by inhibition of a specific target enzyme involved in its steroidogenic pathway: for breast cancer - aromatase (P450AROM) or 17β-hydroxysteroid dehydrogenase (17β-HSD) Type 1 isoenzyme or the metabolic enzyme oestrogen sulfatase; for prostate cancer - 17α-hydroxylase: 17, 20-lyase (P450 17) or 5α-steroid reductase (5α-SR) or 17β-HSD Type 3 isoenzyme. The use of P450AROM inhibitors as sequential agents in breast cancer patients is well established; inhibitors of the other target enzymes are under development and could be sequential or combinational agents. Certain P450 17 inhibitors for prostatic cancer treatment protect the metabolism of retinoic acid (RAMBAs) and 1α,25-dihydroxy vitamin D-3, thereby being cellular differentiation and antiproliferative mimics. These new cytochrome P450 targets and the built-in action of the P450 17 inhibitors may be shown at a later date to alter or delay the progression of the disease from hormone-dependent to hormone-independent. This review discusses the progress made in developing of clinically useful steroidogenesis inhibitors for the relevant disease and some of the difficulties encountered in maintaining/achieving remission due to the changing nature of the disease.
