To investigate the effect of heat stress (HS) on COX-2 expression, primary blood monocytes from healthy donors, human umbilical vein endothelial cells (HUVECs) and two human cancer cell lines, HCT116 colorectal adenocarcinoma and lymphoblastoid Jurkat cells, known to express low levels of COX-2 mRNA and protein [14], [15], [16], [17], were incubated at 43°C for 40 min and allowed to recover at 37°C for 90 min. This evidence concerns the gene PTGS2 and colorectal adenocarcinoma.