On the other hand, in hepatocytes, pancreatic β cells, and many cancer cells, CASP3 and CASP7 activation is inhibited by the presence of X–linked inhibitor of apoptosis protein (XIAP), an important regulator of apoptosis which effectively blocks the apoptotic cascade, preventing cells from undergoing apoptosis even in the presence of apoptotic signals [29]. This evidence concerns the gene CASP3 and cancer.