Aromatase inhibitors (AIs) used as adjuvant therapy in postmenopausal women with hormone receptor-positive breast cancer cause diverse musculoskeletal side effects that include bone loss and its associated fracture. About half of the 391 patients treated with AIs in the Barcelona-Aromatase induced bone loss in early breast cancer cohort suffered a significant bone loss at lumbar spine (LS) and/or femoral neck (FN) after 2 years on AI-treatment. In contrast, up to one-third (19.6% LS, 38.6% FN) showed no decline or even increased bone density. The present study aimed to determine the genetic basis for this variability. SNPs in candidate genes involved in vitamin D and estrogen hormone-response pathways (CYP11A1, CYP17A1, HSD3B2, HSD17B3, CYP19A1, CYP2C19, CYP2C9, ESR1, DHCR7, GC, CYP2R1, CYP27B1, VDR and CYP24A1) were genotyped for association analysis with AI-related bone loss (AIBL). After multiple testing correction, 3 tag-SNPs (rs4077581, s11632698 and rs900798) located in the CYP11A1 gene were significantly associated (P!0.005) with FN AIBL at 2 years of treatment. Next, CYP11A1 expression in human fresh bone tissue and primary osteoblasts was demonstrated by RT-PCR. Both common isoforms of human cholesterol side-chain cleavage enzyme (encoded by CYP11A1 gene) were detected in osteoblasts by western blot. In conclusion, the genetic association of CYP11A1 gene with AIBL and its expression in bone tissue reveals a potential local function of this enzyme in bone metabolism regulation, offering a new vision of the steroidogenic ability of this tissue and new understanding of AI-induced bone loss.
Journal of Molecular EndocrinologyResearch M RODRI´GUEZ-SANZ and others CYP11A1 is associated with AI-related bone loss
55:1 69-79http://jme.endocrinology-journals.org Ñ 2015 Society for Endocrinology DOI: 10.1530/JME-15-0079Printed in Great BritainPublished by Bioscientifica Ltd.
IntroductionAromatase inhibitors (AIs) are commonly used as adjuvant therapy in postmenopausal women with hormone receptor-positive breast cancer. Although AIs are generally well tolerated with few serious adverse events, a number of musculoskeletal side effects affecting quality of life have been noted and often lead to discontinuation of therapy (Eastell et al. 2006, Henry et al. 2008.The most common side effects reported with AIs are exacerbation of menopausal symptoms as a result of low estrogen levels; these include pain syndromes, bone loss and associated fracture , Laroche et al. 2014. Several prospective studies and clinical trials have noted the need for assessment and treatment of these musculoskeletal adverse events (Reid et al. 2008, Brufsky et al. 2009, Servitja et al. 2012. In particular, bone mineral density (BMD) reduction and fracture incidence associated with AI therapy can be significantly reduced by oral bisphosphonates (BP) treatment (Bouvard et al. 2014).We are currently conducting a prospective, nonselected, observational, clinical cohort study (BarcelonaAromatase induced bone loss in early breast cancer (B-ABLE...