Novel fetal genes (fls353 and fls485) have been successfully isolated from human fetal liver-derived cDNAs. These genes were specifically expressed in tissues including fetal tissues which are thought to contain a large number of undifferentiated cells and actively differentiating/proliferating cells. High levels of expression of these genes were observed also in a variety of cancer cells. The proteins and genes encoding the proteins can be used as the tool for developing drugs for the treatment of tumors.