title: Aromatase inhibitor-associated bone fractures: a case-cohort GWAS and functional genomics.
abstract: Bone fractures are a major consequence of osteoporosis. There is a direct relationship between serum estrogen concentrations and osteoporosis risk. Aromatase inhibitors (AIs) greatly decrease serum estrogen levels in postmenopausal women, and increased incidence of fractures is a side effect of AI therapy. We performed a discovery case-cohort genome-wide association study (GWAS) using samples from 1071 patients, 231 cases and 840 controls, enrolled in the MA.27 breast cancer AI trial to identify genetic factors involved in AI-related fractures, followed by functional genomic validation. Association analyses identified 20 GWAS single nucleotide polymorphism (SNP) signals with P < 5E-06. After removal of signals in gene deserts and those composed entirely of imputed SNPs, we applied a functional validation "decision cascade" that resulted in validation of the CTSZ-SLMO2-ATP5E, TRAM2-TMEM14A, and MAP4K4 genes. These genes all displayed estradiol (E2)-dependent induction in human fetal osteoblasts transfected with estrogen receptor-α, and their knockdown altered the expression of known osteoporosis-related genes. These same genes also displayed SNP-dependent variation in E2 induction that paralleled the SNP-dependent induction of known osteoporosis genes, such as osteoprotegerin. In summary, our case-cohort GWAS identified SNPs in or near CTSZ-SLMO2-ATP5E, TRAM2-TMEM14A, and MAP4K4 that were associated with risk for bone fracture in estrogen receptor-positive breast cancer patients treated with AIs. These genes displayed E2-dependent induction, their knockdown altered the expression of genes related to osteoporosis, and they displayed SNP genotype-dependent variation in E2 induction. These observations may lead to the identification of novel mechanisms associated with fracture risk in postmenopausal women treated with AIs.
authors.affiliation: Division of Clinical Pharmacology (M.L., L.W., R.M.W.), Department of Molecular Pharmacology and Experimental Therapeutics; Departments of Oncology (J.N.I.) and Health Sciences Research (A.B., G.D.J., E.E.C., D.J.S.); and Division of Endocrinology (S.K.), Mayo Clinic, Rochester, Minnesota 55905; Massachusetts General Hospital (P.E.G.), Harvard University, Boston, Massachusetts 02114; Rikagaku Kenkyūsho Center for Integrative Medical Science (M.K., Y.F.), Yokohama, Japan 230-0045; School of Medicine (Y.N.), Chicago University, Chicago, Illinois 60637; National Cancer Institute of Canada Clinical Trials Group (J.-A.W.C., L.E.S.), Kingston, Ontario, Canada K7L 3N6; and Division of Oncology (M.J.E.), Department of Medicine, Washington University School of Medicine, St Louis, Missouri 63110.
authors.forename: Mohan
authors.initials: M
authors.lastname: Liu
authors.forename: Paul E
authors.initials: PE
authors.lastname: Goss
authors.forename: James N
authors.initials: JN
authors.lastname: Ingle
authors.forename: Michiaki
authors.initials: M
authors.lastname: Kubo
authors.forename: Yoichi
authors.initials: Y
authors.lastname: Furukawa
authors.forename: Anthony
authors.initials: A
authors.lastname: Batzler
authors.forename: Gregory D
authors.initials: GD
authors.lastname: Jenkins
authors.forename: Erin E
authors.initials: EE
authors.lastname: Carlson
authors.forename: Yusuke
authors.initials: Y
authors.lastname: Nakamura
authors.forename: Daniel J
authors.initials: DJ
authors.lastname: Schaid
authors.forename: Judy-Anne W
authors.initials: JA
authors.lastname: Chapman
authors.forename: Lois E
authors.initials: LE
authors.lastname: Shepherd
authors.forename: Matthew J
authors.initials: MJ
authors.lastname: Ellis
authors.forename: Sundeep
authors.initials: S
authors.lastname: Khosla
authors.forename: Liewei
authors.initials: L
authors.lastname: Wang
authors.forename: Richard M
authors.initials: RM
authors.lastname: Weinshilboum
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000077384:Anastrozole; D000730:Androstadienes / Q000009:adverse effects / Q000494:pharmacology / Q000627:therapeutic use; D047072:Aromatase Inhibitors / Q000009:adverse effects* / Q000494:pharmacology / Q000627:therapeutic use; D015519:Bone Density / Q000187:drug effects; D005260:Female; D059647:Gene-Environment Interaction; D055106:Genome-Wide Association Study; D005838:Genotype; D006801:Humans; D008875:Middle Aged; D009570:Nitriles / Q000009:adverse effects / Q000494:pharmacology / Q000627:therapeutic use; D010024:Osteoporosis / Q000139:chemically induced* / Q000235:genetics*; D058866:Osteoporotic Fractures / Q000139:chemically induced* / Q000235:genetics*; D020641:Polymorphism, Single Nucleotide; D014230:Triazoles / Q000009:adverse effects / Q000494:pharmacology / Q000627:therapeutic use
chemical_list: D000730:Androstadienes; D047072:Aromatase Inhibitors; D009570:Nitriles; D014230:Triazoles; D000077384:Anastrozole; C056516:exemestane