Secreted-type glycoprotein WNTs bind to seven-transmembrane-type WNT receptors encoded by Frizzled genes (FZD1-FZD10) to transduce signals to the beta-catenin--TCF pathway, the JNK pathway, or the Ca(2+)-releasing pathway. Wrch1 gene is a down-stream target gene of Wnt1 in C57MG cells, and encodes a Cdc42-related GTPase with the potential to activate the JNK pathway. Here, we isolated human WRCH1 cDNAs (accession no. AB074878) from gastric cancer cell lines OKAJIMA, MKN7, MKN28, MKN45, MKN74, and KATO-III, all of which showed a nucleotide substitution (343 C-->T) without amino-acid substitution compared with WRCH1 cDNA isolated by another group. WRCH1 gene, consisting of at least 3 exons, was mapped to human chromosome 1q42.11-q42.3 by using bioinformatics. WRCH1 mRNA was more highly expressed in corpus callosum, hippocampus, cerebral cortex, and also in several parts within adult brain than in other normal tissues including stomach, pancreas, and placenta. Amounts of WRCH1 mRNA in 40 human cancer cell lines were lower than that in normal stomach, pancreas, or placenta. WRCH1 mRNA was significantly up-regulated in 4 cases of primary kidney tumors, 1 case each of primary colon, gastric, breast, ovarian, and uterus cancer. On the other hand, WRCH1 mRNA was significantly down-regulated in 6 cases of colon tumors, 2 cases of primary kidney cancer and breast cancer. Expression of WRCH1 mRNA was down-regulated by beta-estradiol in MCF-7 cells. This is the first report on comprehensive expression analyses on WRCH1 mRNA.