Expression of sirtuin 1 in breast cancer

Abstract

Breast cancer is the most frequent malignancy in women. Recent studies have proposed that sirtuin 1 (SIRT1) may play a certain role in the tumorgenesis and disease progression of cancer. Therefore, in this study, we demonstrate the localization of SIRT1 in the breast cancer cells by immunohistochemistry method and try to correlate the expression level of SIRT1 with various clinical-pathological parameters as well as the survival time of breast cancer patients. One hundred and eighteen breast cancer cases, arrayed as dual‐cores, were studied in the tissue microarray blocks for their SIRT1 nuclear and cytoplasmic stain.

The expression of SIRT1 is found in over 95% of the tumor samples. Although the active functioning site of SIRT1 is known to be mainly the nucleus, both nuclear and cytoplasmic localization score are assessed separately for SIRT1 expression for more accurate statistically analysis. By bi‐variate Pearson correlation analysis, high nuclear localization of SIRT1 is significantly correlated with low tumor grade (p=0.006) and ER (p=0.001) and PR positive status (p=0.044). Moreover, the cytoplasmic localization score of SIRT1 shows positive correlation with tumor grade (p=0.010). The relationship of SIRT1 expression and survival time of breast cancer patient was studied by Kaplan‐Meier analysis. Despite a marginal fail in obtaining a statistically significant result, the trend in survival curve clearly indicated that nuclear localization of SIRT1 is associated with a poorer overall survival (p=0.052).

Although the pathway of how SIRT1 affects the survival of breast cancer patient is still unknown, many studies suggested that it is largely due to the deacetylated inactivation of p53 tumor suppressor protein by SIRT1. In conclusion, we propose that nuclear localization of SIRT1 can be a potential prognostic factor of breast cancer patients.