Alimentary TractLST-2, A human liver-specific organic anion transporter, determines methotrexate sensitivity in gastrointestinal cancers*,**,*,**,♢
Section snippets
Isolation of the human liver-specific transporter 2 cDNA
A human liver complementary DNA (cDNA) library was constructed using the λZAPII vector (Stratagene).10 Independent clones (5 × 105) were screened with human liver-specific transporter (LST)-111 under low stringency. As a result, 42 independent hybridization-positive clones were isolated. Among these, 1 clone (pH 7), which was distinct from LST-1, was isolated. Multiple sequence alignments of amino acid sequences and phylogenetic tree construction were carried out using Clustal W.12 The
Isolation and hepatic distribution
The isolated cDNA, termed LST-2, encodes 702 amino acids (Mr 77,398). The hydrophobicity analysis20 suggests the presence of 12 transmembrane domains, which is characteristic of organic anion transporters (Figure 1A).
Conclusion
We have shown that LST-2 is one of a key molecule in the delivery of MTX to gastrointestinal cancers. Because of the exclusive expression of LST-2 in the cancer cells, LST-2 may represent a new therapeutic target for the treatment of such cancers with less side effects.
Acknowledgements
The authors thank Drs. K. J. Seth and M. R. Kaplan for discussions.
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Cited by (0)
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Address requests for reprints to: Takaaki Abe, Division of Nephrology, Endocrinology, and Vascular Medicine, Department of Medicine, Tohoku University Graduate School of Medicine, 1-1 Seiryo-cho, Aobaku, Sendai, 980-8574, Japan. e-mail: [email protected]; fax: (81) 22-717-7168.
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Drs. Abe, Unno, and Onogawa contributed equally to this study.
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Supported in part by research grants from the Ministry of Education, Science and Culture of Japan, Yamanouchi Foundation, Osaka Cancer Research Foundation, Nakatomi Foundation, Novartis Foundation, Ono Medical Research Foundation, Inamori Foundation, Welfide Medical Research Foundation, and Uehara Memorial Foundation.
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This study was approved by the Ethical Committee of Tohoku University.
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The sequence of human LST-2 has been deposited under the GenBank accession number AF187815, and the genomic sequence of LST-2 has been deposited under the Genbank accession number AF195785.