The present invention relates to a diagnosis method of cancer using SYG972 gene and to the genomic DNA and to a promoter regulating transcription of the gene. Expression of SYG972 gene is greatly reduced in breast cancer cells compared to normal breast cells. Therefore the present invention provides a method of diagnosis method by using the gene of the present invention or its fragments as a probe. SYG972 genomic according to the present invention is composed of 4 exons and 3 introns. Promoter is 3 kb long from the transcription initiating site in the 5′ direction. SYG972 genomic DNA and promoter can be used to design and screen drugs to promote or to inhibit apoptosis and differentiation of cells, especially to screen drugs to treat cancer, a disease wherein cell growth and differentiation is abnormal.