TI-227 is a cancer metastasis-associated gene isolated from the B16-F10 mouse melanoma subline that preferentially metastasizes to the lung following intravenous injection. TI-227 is more highly expressed in the B16-F10 and colon26-nl17 sublines, which preferentially metastasize to the lung following intravenous injection, than in the B16-BL6 and colon26-nl22 sublines, which preferentially metastasize to the lung following subcutaneous injection. Since TI-227 could not be detected in normal tissues, there is a possibility that it is expressed specifically in tumors that preferentially metastasize to the lung following intravenous inoculation. Although the 5' end of TI-227 was analyzed, its total sequence contained no obvious open reading frame. However comparison with the isolated human counterpart, TI-227H gene, revealed a highly homologous region near the 3' end, which was expected to contain a very short open reading frame.