Steroid Sulfatase Inhibitors: Their Potential in the Therapy of Breast Cancer

: Steroid sulfatase (STS) is the only well characterized enzyme in human cells that is capable to desulfate estrone 3-sulfate (E1S) and dehydroepiandrosterone sulfate (DHEAS) as a first step in the conversion of these precursors to active hormones. STS has been found to be highly expressed in estrogen-dependent breast tumors in post-menopausal women and is regarded as a crucial component of the local estrogen production that is required for tumor growth and survival. Inhibitors of STS are expected to block the intra-tumoral estrogen synthesis and, therefore, are considered as potential new therapeutic agents for the treatment of estrogen-dependent cancers of the breast and the endometrium. In this review, we give an overview on the current status in the field of medicinal chemistry of STS inhibitors. Newer developments comprise potent aryl sulfamate-based irreversible inhibitors, and several types of reversible inhibitors. Other directions include compounds with dual mode of action, such as compounds that block both STS and aromatase, or act as STS inhibitors and antiproliferative or antiangiogenic agents at the same time. In particular, these agents featuring an extended mode of action hold promise to be included in the armamentarium to fight endocrine-dependent cancer.