title: The human carnitine transporter SLC22A16 mediates high affinity uptake of the anticancer polyamine analogue bleomycin-A5.
abstract: Bleomycin is used in combination with other antineoplastic agents to effectively treat lymphomas, testicular carcinomas, and squamous cell carcinomas of the cervix, head, and neck. However, resistance to bleomycin remains a persistent limitation in exploiting the full therapeutic benefit of the drug with other types of cancers. Previously, we documented that the Saccharomyces cerevisiae L-carnitine transporter Agp2 is responsible for the high affinity uptake of polyamines and of the polyamine analogue bleomycin-A5. Herein, we document that the human L-carnitine transporter hCT2 encoded by the SLC22A16 gene is involved in bleomycin-A5 uptake, as well as polyamines. We show that NT2/D1 human testicular cancer cells, which highly express hCT2, are extremely sensitive to bleomycin-A5, whereas HCT116 human colon carcinoma cells devoid of detectable hCT2 expression or MCF-7 human breast cancer cells that only weakly express the permease showed striking resistance to the drug. NT2/D1 cells accumulated fluorescein-labeled bleomycin-A5 to substantially higher levels than HCT116 cells. Moreover, L-carnitine protected NT2/D1 cells from the lethal effects of bleomycin-A5 by preventing its influx, and siRNA targeted to hCT2 induced resistance to bleomycin-A5-dependent genotoxicity. Furthermore, hCT2 overexpression induced by transient transfection of a functional hCT2-GFP fusion protein sensitized HCT116 cells to bleomycin-A5. Collectively, our data strongly suggest that hCT2 can mediate bleomycin-A5 and polyamine uptake, and that the rate of bleomycin-A5 accumulation may account for the differential response to the drug in patients.
authors.affiliation: Maisonneuve-Rosemont Hospital Research Center, University of Montreal, Montreal, Quebec H1T 2M4, Canada. aouidamustapha@yahoo.fr
authors.forename: Mustapha
authors.initials: M
authors.lastname: Aouida
authors.forename: Richard
authors.initials: R
authors.lastname: Poulin
authors.forename: Dindial
authors.initials: D
authors.lastname: Ramotar
mesh_terms: D000903:Antibiotics, Antineoplastic / Q000493:pharmacokinetics; D001761:Bleomycin / Q000031:analogs & derivatives* / Q000493:pharmacokinetics; D001943:Breast Neoplasms; D045744:Cell Line, Tumor; D003110:Colonic Neoplasms; D019008:Drug Resistance, Neoplasm; D005260:Female; D006801:Humans; D008297:Male; D027701:Organic Cation Transport Proteins / Q000378:metabolism*; D010599:Pharmacokinetics; D011073:Polyamines / Q000493:pharmacokinetics; D013736:Testicular Neoplasms
chemical_list: D000903:Antibiotics, Antineoplastic; D027701:Organic Cation Transport Proteins; D011073:Polyamines; C467737:SLC22A16 protein, human; D001761:Bleomycin; C025703:bleomycetin