<；P>；PROBLEM TO BE SOLVED: To provide a novel amino acid transporter molecule mediating transportation of amino acids, which are nutrients essentially required in the survival and proliferation of various normal cells constituting a living body and various pathology-associated abnormal cells such as tumor cells, into cells and being expressed specifically in tumor cells compared with normal cells； and drugs for treating various pathogenic conditions such as tumor (cancer) which are obtained by identifying and isolating the amino acid transporter molecule and identifying a substance capable of inhibiting the biological activity and/or expression of this molecule. <；P>；SOLUTION: Intensive studies were made to identify a tumor cell membrane surface molecule conjugating or interacting with a cell membrane surface 4F2 molecule seemingly playing an important role in the activation of an unknown amino acid transporter. As a result, a gene encoding the novel amino acid transporter molecule, which mediates the incorporation of various neutral amino acids, various drugs or physiological substances into cells, has been found out and a substance capable of inhibiting the incorporation of amino acids via this molecule and thus inhibiting the proliferation of tumor cells has been also found out. <；P>；COPYRIGHT: (C)2011,JPO&INPIT
