Sirtuin 1 (SIRT1), originally identified as a longevity gene, is induced by caloric restriction, and regulates various cellular functions including DNA repair, cell survival and metabolism via the deacetylation of target proteins such as histone and p53. These functions are considered to act dualistically as preventing or facilitating cancer. This study aimed to clarify the expression and role of SIRT1 in endometrial carcinoma. Because a high-calorie diet was a well-known risk factor for endometrial carcinoma, we first hypothesized that SIRT1 might be downregulated in normal endometrial glandular cells of obese women. However, no correlation was observed between the expression of SIRT1 and body mass index (BMI). In contrast, regardless of BMI, the immunohistochemical expression of SIRT1 was significantly higher in endometrial carcinoma (108 cases) than in normal endometria (60 cases) (Po0.05), and its overexpression was associated with a shorter survival (Po0.05). Our experiments in vivo revealed that SIRT1 accelerated the proliferation of endometrial carcinoma cell lines (HHUA, HEC151, and HEC1B). SIRT1 overexpression significantly enhanced the resistance for cisplatin and paclitaxel in HHUA cells. Although p53 is an important target protein for SIRT1, the selective SIRT1 inhibitor (EX527) significantly suppressed the proliferation and cisplatin resistance of three endometrial carcinoma cell lines regardless of the p53 mutation status. In addition, SIRT1 overexpression in HHUA cells accelerated tumor growth and cisplatin resistance in nude mice, and EX527 significantly suppressed the growth of tumors of HHUA and HEC1B cells. No adverse effect of EX527 was observed in these mice. In conclusion, SIRT1 is involved in the acquisition of the aggressive behavior associated with endometrial carcinoma, and the SIRT1 inhibitor, EX527, may be a useful agent for the treatment of this malignancy.

BACKGROUND: SIRT1 is a longevity gene that forestalls aging and age-related diseases including cancer, and has recently attracted widespread attention due to its overexpression in some cancers. We previously identified the overexpression of SIRT1 in ovarian carcinoma (OvCa) as a poor prognostic factor. However, mechanistic insights into the function of SIRT1 in OvCa have yet to be elucidated. METHODS: Quantitative real-time reverse PCR (qRT-PCR) and Western blotting were employed to examine the expression of SIRT1 in a panel of human OvCa cell lines. si-RNA or sh-RNA and cDNA technologies were utilized to knockdown or overexpress SIRT1, respectively. The effects of SIRT1 on proliferation and chemoresistance were examined using a WST-1 assay, and the underlying mechanisms were confirmed using an apoptotic assay, and the quantification of glutathione (GSH), and reactive oxygen species (ROS). The aggressiveness of SIRT1 was analyzed using in vitro invasion and migration assays. RESULTS: SIRT1 was more strongly expressed in OvCa cell lines than in the immortalized ovarian epithelium at the gene and protein levels. Stress up-regulated the expression of SIRT1 in dose- and time-dependent manners. SIRT1 significantly enhanced the proliferation (P < .05), chemoresistance (P < .05), and aggressiveness of OvCa cells by up-regulating multiple antioxidant pathways to inhibit oxidative stress. Further study into the overexpression of SIRT1 demonstrated the up-regulation of several stemness-associated genes and enrichment of CD44v9 via an as-yet-unidentified pathway. CONCLUSIONS: Our results suggest that SIRT1 plays a role in the acquisition of aggressiveness and chemoresistance by OvCa, and has potential as a therapeutic target for OvCa.

PurposeLipocalin 2 (LCN2) is a secretory protein that is involved in various physiological processes including iron transport. We previously identified LCN2 as an up-regulated gene in endometrial carcinoma, and found that the overexpression of LCN2 and its receptor, SLC22A17, was associated with a poor prognosis. However, the functions and mechanism of action of LCN2 currently remain unclear.MethodsThe LCN2-overexpressing endometrial carcinoma cell lines, HHUA and RL95-2, and LCN2-low-expressing one, HEC1B, were used. The effects of LCN2 on cell migration, cell viability, and apoptosis under various stresses, including ultraviolet (UV) irradiation and cisplatin treatment, were examined using the scratch wound healing assay, WST-1 assay, and Apostrand assay, respectively.ResultsLCN2-silencing using shRNA method significantly reduced the migration ability of cells (p<0.05). Cytotoxic stresses significantly decreased the viability of LCN2-silenced cells more than that of control cells. In contrast, LCN2 overexpression was significantly increased cisplatin resistance. These effects were canceled by the addition of the iron chelator, deferoxamine. After UV irradiation, the expression of phosphorylated Akt (pAkt) was decreased in LCN2-silenced cells, and the PI3K inhibitor canceled the difference induced in UV sensitivity by LCN2. The cisplatin-induced expression of pAkt was not affected by LCN2; however, the expression of p53 and p21 was increased by LCN2-silencing.ConclusionsThese results indicated that LCN2 was involved in the migration and survival of endometrial carcinoma cells under various stresses in an iron-dependent manner. The survival function of LCN2 may be exerted through the PI3K pathway and suppression of the p53-p21 pathway. These functions of LCN2 may increase the malignant potential of endometrial carcinoma cells.

Sirtuin 1 (SIRT1), originally identified as a longevity gene, regulates DNA repair and metabolism by deacetylating target proteins such as p53. SIRT1 plays a key role in the pathophysiology of metabolic diseases and neurodegenerative disorders, and is considered to protect against age-related diseases including cancer. In contrast, SIRT1 may be oncogenic because its overexpression has been detected in many cancers. The aim of the present study was to clarify the expression and the role of SIRT1 in ovarian carcinoma (OvCa). The expression of SIRT1 was evaluated immunohistochemically in 16 cases of normal ovaries, 35 cases of endometriosis with/without carcinoma, and 68 cases of OvCa (endometrioid, 16; clear cell, 20; mucinous, 16; serous, 16). Staining results were evaluated semiquantitatively by the Immunoreactive Scoring System, and the relationships with clinicopathologic features and outcomes of patients were analyzed. The expression of SIRT1 was higher in endometrioid, mucinous, and clear-cell carcinomas than in the inclusion cysts of normal ovaries, but not in serous carcinoma (P=0.038). The expression of SIRT1 on OvCa did not correlate with age, stage, location of metastasis, or capsular penetration. However, elevated SIRT1 expression was a significant predictor of shorter survival in univariate (P=0.038) and multivariate (P=0.037) survival analyses, regardless of the tumor stage. Results of the present study suggest a positive role for SIRT1 in the development of OvCa and its potential as a novel therapeutic target.