Immunohistochemical staining of SFRP1, SFPR2, SDC2, and PRIMA1 on representative colonic biopsy specimens. Immunohistochemical analyses were performed to determine the protein expression changes of SFRP1 (A, B, C), SFRP2 (D, E, F), SDC2 (G, H, I), and PRIMA1 (J, K, L) in normal, colorectal adenoma, and cancer samples. Decreasing protein levels of all 4 markers were observed along the colorectal adenoma-carcinoma sequence. Digital microscopy images, 30 x magnification; scale bar: 50 μm.