Analysis of 41 cancer cell lines reveals excessive allelic loss and novel mutations in the SIRT1 gene

Abstract

SIRT1 is an evolutionarily conserved protein deacetylase that modulates stress response, cellular metabolism and aging in model organisms. While SIRT1 exerts beneficial effects in protecting against age-related diseases, the role of SIRT1 in cancer has been controversial. SIRT1 promotes cell survival by deacetylating, and thereby negatively regulating the activity of important tumor suppressors such as p53. In this regard, SIRT1 has been considered to be a potential oncogene, and SIRT1 inhibitors have been studied for possible anticancer therapeutic effects. In contrast, it has been shown that SIRT1 deficiency leads to increased genomic instability and tumorigenesis, and that overexpression of SIRT1 attenuates cancer formation in mice, suggesting it may also act as a tumor suppressor. Based on this evidence, SIRT1-activating molecules could act as candidate chemotherapeutic drugs. In order to gain insight into the role of SIRT1 in cancer, we performed a comprehensive resequencing analysis of the SIRT1 gene in 41 tumor cell lines and found an unusually excessive homozygosity, which was confirmed to be allelic loss by microsatellite analysis. Furthermore, we found two novel SIRT1 mutations (D739Y and R65_A72del) in addition to the known, rare non-synonymous variation resulting in I731V. In vitro assays using purified SIRT1 protein showed that these mutations do not alter SIRT1 deacetylase activity or telomerase activity, which was shown to be regulated by SIRT1. We conclude that allelic loss or mutations in the SIRT1 gene occur prevalently during tumorigenesis, supporting the assertion that SIRT1 may serve as a tumor suppressor.

Keywords: :

• SIRT1
• breast cancer
• cell line
• allelic loss
• gene mutation
• tumor suppressor

Disclosure of Potential Conflicts of Interest

No potential conflicts of interest were disclosed.

Acknowledgments

We would like to thank the Genomics Shared Facility at the Albert Einstein College of Medicine for their assistance with the Microsatellite analysis. We also thank Dr. Mieke Schutte for providing the DNAs for all the breast cancer cell lines and Dr. Matthew Levy for providing the HeLa cell line. All the amplified products were sequenced from Macrogen USA. This work was funded by NIH grant AG024391, AG027734 and AG17242. Y.S. is the recipient of a Glenn Award for Research in Biological Mechanisms of Aging. B.P.H. was supported by an NSERC PGS-D Fellowship.