OCC1 was initially identified as a novel human cDNA overexpressed in a colon carcinoma cell line. Elevated levels of OCC1 mRNA were observed in three of eight colon carcinomas, suggesting that OCC1 may be a hallmark of only a subset of colon carcinomas. It is highly expressed in skeletal muscle, kidney, placenta, and pancreas tissues, with low to no expression in heart, brain, lung and liver tissues. At least two different OCC1 mRNA species are known to exist.