The gene for a novel transmembrane protein containing epidermal growth factor and follistatin domains is frequently hypermethylated in human tumor cells

A DNA fragment frequently hypermethylated in tumor cells was isolated using a novel screening strategy termed methylation-sensitive arbitrarily primed PCR. The isolated sequence corresponded to a CpG island at the 5' end of a previously unknown gene, TPEF (transmembrane protein containing epidermal growth factor and follistatin domains). Expression of TPEF was observed using Northern master blot analysis of a variety of normal tissues including colon, bladder, and prostate tissue. TPEF maps to human chromosome 2q33, where frequent loss of heterozygosity is seen in various human tumors, and TPEF was not expressed in most human colon and various other tumor cell lines examined by reverse transcription-PCR. Nine of 11 tumor cell lines were highly methylated in the 5' region and the first exon of the gene that demonstrated features characteristic of a CpG island. However the other two cell lines, which expressed TPEF, were hypomethylated in the 5' end of the gene. The region was also hypermethylated in 11 of 16 primary bladder tumors and in 3 of 4 primary colon tumors when compared with adjacent normal tissue. Our results suggest that potential tumor suppressor genes can be isolated from human tumors by virtue of their altered methylation patterns.