The expression and correlation of SIRT1 and Phospho-SIRT1 in colorectal cancer

Abstract

SIRT1 is the homologue of sir2 in mammals, which is a nicotinamide adenine dinucleotide (NAD(+)) dependent histone deacetylase. SIRT1 is involved in many physiological processes, such as metabolism, senescence, inflammatory response, neuroprotection, and tumorigenesis by acetylating histones and multiple transcription factors. However, the exact role of SIRT1 in tumor is still under controversial. Immunohistochemistry and Western blot were performed to investigate the expressions and subcellular localizations of SIRT1 and Phospho-SIRT1 in colorectal cancer tissues and adjacent normal tissues. The relationship between SIRT1 or Phospho-SIRT1 and clinicopathological characteristics was also analyzed. Real-Time PCR was performed to investigate the transcriptional level of SIRT1 mRNA in colorectal cancer tissues and adjacent normal tissues. SIRT1 and Phospho-SIRT1 were both localized in the nucleus. The expressions of SIRT1 and Phospho-SIRT1 were higher in colorectal cancer tissues than normal tissues. SIRT1 expression in cancer tissues was associated with patient age, TNM stage and mutant P53 loss. Phospho-SIRT1 expression in cancer tissues was associated with Ki67. SIRT1 and Phospho-SIRT1 were highly correlated in cancer tissues and normal tissues. The ratios of Phospho-SIRT1 and SIRT1 expression in cancer tissues were higher than normal tissues. SIRT1 mRNA level was no significant difference in cancer tissues and normal tissues. SIRT1 have a dual character in colorectal cancer, and Phospho-SIRT1 may determine the role of SIRT1 in colorectal cancer formation.

Keywords: Ki67; P53; Phospho-SIRT1; SIRT1; colorectal cancer.

Figure 1

SIRT1 and Phospho-SIRT1 were detected by IHC (100 × and 400 × magnification). Mann-Whitney U test was used to analysis expression difference of SIRT1 or Phospho-SIRT1 in cancer tissues and normal tissues. A. Brown staining was seen localized to the nucleus of cells. SIRT1 expression in cancer tissues and normal tissues were 60% and 25%, respectively, Phospho-SIRT1 expression were 38% and 15%, respectively. B. Final IHC staining score of each slide was scored by multiplying the staining density by the staining area, and staining scores were shown as a scatter plot. The average score of SIRT1 in cancer tissues and normal tissues were 4.780 ± 0.353 and 2.450 ± 0.373, respectively (P < 0.05), the average scores of Phospho-SIRT1 were 3.020 ± 0.228 and 1.900 ± 0.261, respectively (P < 0.05).

Figure 2

SIRT1 and Phospho-SIRT1 were detected by WB. Mann-Whitney U test was used to analysis expression differences of SIRT1 or Phospho-SIRT1 in cancer tissues and normal tissues. A. Tumor tissues and normal tissues were both extracted for whole protein, cytoplasmic protein and nuclear protein (T = tumor tissue, N = normal tissue). Cytoplasm protein was normalized with β-actin and nucleus protein was normalized with H3. SIRT1 and Phospho-SIRT1 were both localized in the nucleus of cancer tissues and normal tissues. B. Relative expression of SIRT1 and Phospho-SIRT1 in tumor tissues and normal tissues. SIRT1 expression in cancer tissues and normal tissues were 1.351 ± 0.020 and 0.825 ± 0.015, respectively (P < 0.05), Phospho-SIRT1 expression were 0.747 ± 0.022 and 0.381 ± 0.0148, respectively (P < 0.05).

Figure 3

Spearman correlation analysis was used to examine the expression correlation between Phospho-SIRT1 and SIRT1. Phospho-SIRT1 and SIRT1 had a highly positive correlation in both tumor tissues (r = 0.872) and normal tissues (r = 0.735). The ratios of Phospho-SIRT1 and SIRT1 expression in tumor tissues were higher than normal tissues.