The CYP17A1 inhibitor abiraterone exhibits estrogen receptor agonist activity in breast cancer.

Cytochrome P450 17A1 (CYP17A1) is the requisite enzyme for synthesis of sex steroids, including estrogens and androgens. As such, inhibition of CYP17A1 is a target for inhibiting the growth of hormone-dependent cancers including prostate and breast cancer. Abiraterone, is a first in class potent and selective CYP17A1 inhibitor that has been approved for the treatment of castration-resistant prostate cancer. Given that, androgens are the precursors for estrogen production, it has been proposed that abiraterone could be an effective form of treatment for estrogen receptor (ER)-positive breast cancer, though its utility in this context has yet to be established. Abiraterone has a core steroid-like chemical structure, and so we hypothesized that it may bind to nuclear steroid receptors including ER and have estrogenic activity. We tested this hypothesis by investigating abiraterone's ability to directly modulate ER signaling in breast cancer cell line models. We show that abiraterone directly activates ER, induces ER-target gene expression, and elicits estrogen-response-element reporter activity in the ER-positive cell lines MCF-7 and T47D. Abiraterone also induced cell proliferation by ~2.5-fold over vehicle in both MCF-7 and T47D cells. Importantly, abiraterone-induced cell proliferation and ER-activity was blocked by the selective estrogen receptor downregulator (SERD) fulvestrant, confirming that abiraterone directly acts at the ER. These data suggest that abiraterone should be combined with other ER antagonists when used for the clinical management of ER-positive breast cancer.

Predicted Benign and Synonymous Variants in CYP11A1 Cause Primary Adrenal Insufficiency Through Missplicing.

Primary adrenal insufficiency (PAI) is a potentially life-threatening condition that can present with nonspecific features and can be difficult to diagnose. We undertook next generation sequencing in a cohort of children and young adults with PAI of unknown etiology from around the world and identified a heterozygous missense variant (rs6161, c.940G>A, p.Glu314Lys) in CYP11A1 in 19 individuals from 13 different families (allele frequency within undiagnosed PAI in our cohort, 0.102 vs 0.0026 in the Genome Aggregation Database; P < 0.0001). Seventeen individuals harbored a second heterozygous rare disruptive variant in CYP11A1 and two had very rare synonymous changes in trans (c.990G>A, Thr330 = ; c.1173C>T, Ser391 =). Although p.Glu314Lys is predicted to be benign and showed no loss-of-function in an Escherichia coli assay system, in silico and in vitro studies revealed that the rs6161/c.940G>A variant, plus the c.990G>A and c.1173C>T changes, affected splicing and that p.Glu314Lys produces a nonfunctional protein in mammalian cells. Taken together, these findings show that compound heterozygosity involving a relatively common and predicted "benign" variant in CYP11A1 is a major contributor to PAI of unknown etiology, especially in European populations. These observations have implications for personalized management and demonstrate how variants that might be overlooked in standard analyses can be pathogenic when combined with other very rare disruptive changes.

A high rate of novel CYP11B1 mutations in Saudi Arabia.

Despite ethnic variation, 11 ß-hydroxylase deficiency (11ß-OHD) has generally been considered the second most common subtype of congenital adrenal hyperplasia (CAH). We report a high rate of novel mutations in this gene (CYP11B1) in patients from Saudi Arabia. We studied 16 patients with 11ß-OHD from 8 unrelated families. DNA was isolated from peripheral blood. The 9 exons and exon-intron boundaries of CYP11B1 were PCR-amplified and directly sequenced. The novel mutations were functionally characterized using subcloning, in vitro mutagenesis, cell transfection and 11-deoxycortisol: cortisol conversion assays. Six mutations were found in these 8 unrelated families. Three of these mutations are completely novel and two have just been recently described as novel mutations from the same population. These include a single nucleotide insertion mutation in codon 18 (c.53_54insT) leading to frameshift and truncation in 4 siblings, a novel mutation (c.1343G>C, p.R448P) in 3 unrelated families, a novel mutation (c.1394A>T, p.H465L) in 2 siblings, a novel mutation (c.617G>T, p.G206V) in 1 patient, and a recently described non-sense novel mutation (c.780G>A, p.W260X) in another patient. Out of the 6 mutations described in this report, only one mutation (p.Q356X) was reported previously. In vitro functional testing of the 3 missense and nonsense novel mutations revealed complete loss of the 11 hydroxylase activity. We conclude that 11 ß-OHD in Saudi Arabia has a unique genotype with a high rate of novel mutations. The novel p. R448P mutation is the most common mutation in this highly inbred population.

The Metabolism, Analysis, and Targeting of Steroid Hormones in Breast and Prostate Cancer.

Breast and prostate cancers are malignancies in which steroid hormones drive cellular proliferation. Over the past century, this understanding has led to successful treatment strategies aimed to inhibit hormone-mediated tumor growth. Nonetheless, disease relapse and progression still pose significant clinical problems, with recurrent and metastatic tumors often exhibiting resistance to current drug therapies. The central role of androgens and estrogens in prostate and breast cancer etiology explains not only why endocrine therapies are often initially successful but also why many tumors ultimately become resistant. It is hypothesized that reducing the concentration of active hormones in the systemic circulation may be insufficient to block cancer progression, as this action selects for tumor cells that can generate active steroids from circulating precursors. This review aims to highlight the currently known differences of steroid biosynthesis in normal physiology versus hormone-dependent cancers, modern approaches to the assessment and targeting of these pathways, and priorities for future research.