PSG9 is exclusively expressed by placental cells. Quantitative RT-PCR analysis of PSG9 transcript (a) and northern blot analysis of different normal tissues (1 μg mRNA/lane) probed with the labelled PSG9 cDNA (b) shows specific expression of PSG9 in placenta. (a-b). Colorectal cancer cell lines were also examined for PSG9 expression level by quantitative- (c) and semi-quantitative RT-PCR (d). Highest expression level of PSG9 was detected in SW480 cells and was lowest in the RKO cell line (c-d).