PROS1 and colorectal carcinoma: In order to determine why different CRC cell lines exhibit different patterns when Nkx2.5 is overexpressed, we measured the levels of antitumor protein p53 (38, 40, 61–63) and its downstream effector p21WAF1/CIP1 (64, 65) since Nkx2.5 behaves like p53 and it may interact with p53-related pathway as another NK2 family member Nkx2.1 (17–19, 25).