title: Estrone-3-sulphate, a potential novel ligand for targeting breast cancers.
abstract: The current study investigates the potential of estrone-3-sulphate (E3S) as a ligand for targeting Organic Anion Transporting Polypeptides (OATP), a family of membrane associated uptake transporters, for detection and diagnosis of hormone dependent breast cancers. E3S, an OATP substrate, is a predominant source of tumour estradiol in post-menopausal patients. To assess the potential of E3S as a ligand, distribution of exogenous E3S was determined at the whole body, tumour and cellular levels in murine models of hormone-dependent (MCF-7) and independent (MDA-MB-231) breast cancers. The highest levels of tumour uptake were observed at 6 h post injection (p.i) with significant difference (p = 0.04) between the level in MCF-7 (13.9±3.1%ID/g) and MDA-MB-231 (10.4±1.1%ID/g) (%ID/g: percentage of the total injected dose per gram tissue). The highest tumour-to-blood ratios (MCF-7∶7.4±1.2; MDA-MB-231∶9.1±2.1) were observed at 48 p.i., and highest tumour-to-muscle ratios (MCF-7∶10.7±1.5; MDA-MB-231∶3.8±0.7) were observed at 6 h p.i. Analogous to total tumour uptake, ex vivo tumour cell uptake at 2 h p.i. was 6 fold higher in MCF-7 in comparison to MDA-MB-231 tumour cells. Blocking studies, conducted by pre-administration of 100-fold excess E3S, resulted in significantly lower (MCF-7: p = 0.01; MDA-MB-231: p = 0.02) tumour uptake in both xenograft models, suggesting the involvement of an active carrier-mediated process. The expression of OATP1A2 was detected in tumour sections from both xenografts, with significantly higher expression (p = 0.002) in the MCF-7 xenografts. Overall, the higher tumour uptake and tumour-to-muscle ratio, alongside the higher expression of OATP1A2, in the MCF-7 xenograft model suggests the potential of E3S to serve as a novel ligand for targeting hormone dependent breast cancers.
authors.affiliation: Department of Pharmaceutical Sciences, Leslie Dan Faculty of Pharmacy, University of Toronto, Toronto, Ontario, Canada.
authors.forename: Nilasha
authors.initials: N
authors.lastname: Banerjee
authors.forename: Humphrey
authors.initials: H
authors.lastname: Fonge
authors.forename: Andrew
authors.initials: A
authors.lastname: Mikhail
authors.forename: Raymond M
authors.initials: RM
authors.lastname: Reilly
authors.forename: Reina
authors.initials: R
authors.lastname: Bendayan
authors.forename: Christine
authors.initials: C
authors.lastname: Allen
mesh_terms: D000818:Animals; D001943:Breast Neoplasms / Q000188:drug therapy* / Q000378:metabolism; D045744:Cell Line, Tumor; D004958:Estradiol / Q000378:metabolism; D004970:Estrone / Q000031:analogs & derivatives* / Q000378:metabolism / Q000493:pharmacokinetics / Q000494:pharmacology; D005260:Female; D006801:Humans; D008024:Ligands; D061986:MCF-7 Cells; D051379:Mice; D008819:Mice, Nude; D027701:Organic Cation Transport Proteins / Q000378:metabolism
chemical_list: D008024:Ligands; D027701:Organic Cation Transport Proteins; D004970:Estrone; D004958:Estradiol; C017296:estrone sulfate