SIRT1 and prostate carcinoma: The immunostaining of SIRT1 has revealed that both the proportion of positive cells and staining intensity are significantly increased in human prostate cancer specimens.50 SIRT1 was also highly expressed in other types of human cancer tissues, such as ovary, liver, breast, stomach, and pancreas.51–55 In case of human colorectal cancer, SIRT1 overexpression was detected as well.56 However, other investigations have revealed pronounced SIRT1 expression in both normal colon and tumor tissues, even though expression is substantially reduced in some higher grade colon tumors.41,57