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Tomabechi R, Kishimoto H, Sato T, Saito N, Kiyomiya K, Takada T, Higuchi K, Shirasaka Y, Inoue K. SLC46A3 is a lysosomal proton-coupled steroid conjugate and bile acid transporter involved in transport of active catabolites of T-DM1. PNAS Nexus 2022; 1:pgac063. [PMID: 36741448 PMCID: PMC9896951 DOI: 10.1093/pnasnexus/pgac063] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/02/2022] [Accepted: 05/17/2022] [Indexed: 02/07/2023]
Abstract
Antibody-drug conjugates (ADCs) represent a new class of cancer therapeutics that enable targeted delivery of cytotoxic drugs to cancer cells. Although clinical efficacy has been demonstrated for ADC therapies, resistance to these conjugates may occur. Recently, SLC46A3, a lysosomal membrane protein, was revealed to regulate the efficacy of trastuzumab emtansine (T-DM1), a noncleavable ADC that has been widely used for treating breast cancer. However, the role of SLC46A3 in mediating T-DM1 cytotoxicity remains unclear. In this study, we discovered the function of SLC46A3 as a novel proton-coupled steroid conjugate and bile acid transporter. SLC46A3 preferentially recognized lipophilic steroid conjugates and bile acids as endogenous substrates. In addition, we found that SLC46A3 directly transports Lys-SMCC-DM1, a major catabolite of T-DM1, and potent SLC46A3 inhibitors attenuate the cytotoxic effects of T-DM1, suggesting a role in the escape of Lys-SMCC-DM1 from the lysosome into the cytoplasm. Our findings reveal the molecular mechanism by which T-DM1 kills cancer cells and may contribute to the rational development of ADCs that target SLC46A3.
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Affiliation(s)
- Ryuto Tomabechi
- Department of Biopharmaceutics, School of Pharmacy, Tokyo University of Pharmacy and Life Sciences, 1432-1, Horinouchi, Hachioji, Tokyo 192-0392, Japan
| | - Hisanao Kishimoto
- Department of Biopharmaceutics, School of Pharmacy, Tokyo University of Pharmacy and Life Sciences, 1432-1, Horinouchi, Hachioji, Tokyo 192-0392, Japan
| | - Taeka Sato
- Department of Biopharmaceutics, School of Pharmacy, Tokyo University of Pharmacy and Life Sciences, 1432-1, Horinouchi, Hachioji, Tokyo 192-0392, Japan
| | - Naoki Saito
- Department of Biopharmaceutics, School of Pharmacy, Tokyo University of Pharmacy and Life Sciences, 1432-1, Horinouchi, Hachioji, Tokyo 192-0392, Japan
| | - Keisuke Kiyomiya
- Department of Biopharmaceutics, School of Pharmacy, Tokyo University of Pharmacy and Life Sciences, 1432-1, Horinouchi, Hachioji, Tokyo 192-0392, Japan
| | - Tappei Takada
- Department of Pharmacy, The University of Tokyo Hospital, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8655, Japan
| | - Kei Higuchi
- Department of Biopharmaceutics, School of Pharmacy, Tokyo University of Pharmacy and Life Sciences, 1432-1, Horinouchi, Hachioji, Tokyo 192-0392, Japan
| | - Yoshiyuki Shirasaka
- Faculty of Pharmacy, Institute of Medical, Pharmaceutical and Health Sciences, Kanazawa University, Kakuma-machi, Kanazawa 920-1192, Japan
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