We have discovered a protein in humans, herein referred to as collagen like gene (CLG) product (SEQ ID NOS: 12 and 13), that is expressed in human prostate cancer and breast cancer cell lines but not in normal adult, placenta, lung, liver, skeletal muscle, kidney or pancreas tissues. We have also discovered that the level of CLG mRNA expression correlates positively with the metastatic potential of the cancer cell lines tested.