Immunohistochemical staining of heme oxygenase-1 (HO-1) in colorectal cancer tissues and adjacent normal colon tissues. (a) and (b) HO-1 expressions in normal colon tissues, samples being negative staining and positive staining respectively. (c), (e) and (g) Examples of HO-1 expressions in colon cancer tissues of different histological differentiation. (d), (f) and (h) Examples of HO-1 expressions in rectal cancer tissues of different histological differentiation. In colorectal cancers, many stromal cells in including neutrophils (i), fibroblasts (j), macrophages (k) and vascular endothelial cells (l) are positively stained by HO-1. Arrows and Amplification indicate the representative positive sites.