Abstract
BackgroundAdiponectin is inversely related to BMI, positively correlates with insulin sensitivity, and has anti-atherogenic effects. In recent years, adiponectin has been well studied in the field of oncology. Adiponectin has been shown to have antiproliferative effects on gastric cancer, and adiponectin expression is inversely correlated with clinical staging of the disease. However, no studies have reported the correlation between serum adiponectin and receptor expression with disease progression.MethodsIn this study, we evaluated expression levels of 2 adiponectin receptors--AdipoR1 and AdipoR2--and attempted to correlate their expression with prognosis in gastric cancer patients. AdipoR1 and AdipoR2 expression in gastric cancer cell lines (MKN45, TMK-1, NUGC3, and NUGC4) was evaluated by western blotting analysis, and the antiproliferative potential of adiponectin was examined in vitro. Serum adiponectin levels were evaluated in 100 gastric cancer patients, and the expression of AdipoR1 and AdipoR2 was assessed by immunohistochemical staining.ResultsMKN45 and NUGC3 expressed higher levels of AdipoR1 compared to NUGC4, even though there was no significance in AdipoR2 expression. The antiproliferative effect of adiponectin was confirmed in MKN45 and NUGC3 at 10 μg/ml. No significant associations were observed between serum adiponectin levels and clinicopathological characteristics, but lymphatic metastasis and peritoneal dissemination were significantly higher in the negative AdipoR1 immunostaining group (24/32, p = 0.013 and 9/32, p = 0.042, respectively) compared to the positive AdipoR1 group (lymphatic metastasis, 33/68; peritoneal dissemination, 8/68). On the other hand, AdipoR2 expression was only associated with histopathological type (p = 0.001). In survival analysis, the AdipoR1 positive staining group had significantly longer survival rates than the negative staining group (p = 0.01). However, multivariate analysis indicated that AdipoR1 was not an independent prognostic factor on patient's survival on gastric cancer.ConclusionsIn gastric cancer, adiponectin has the possibility to be involved in cell growth suppression via AdipoR1. The presence of AdipoR1 could be a novel anticancer therapeutic target in gastric cancer.
Highlights
Adiponectin is inversely related to BMI, positively correlates with insulin sensitivity, and has antiatherogenic effects
Expression of adiponectin receptor 1 (AdipoR1)/R2 and effect of adiponectin on gastric cancer cells To determine the expression of AdipoR1/R2 in gastric cancer cell lines, western blotting analysis was performed
No significant differences were observed in expression of adiponectin receptor 2 (AdipoR2) (Figure 1B)
Summary
Adiponectin is inversely related to BMI, positively correlates with insulin sensitivity, and has antiatherogenic effects. Adiponectin has been shown to have antiproliferative effects on gastric cancer, and adiponectin expression is inversely correlated with clinical staging of the disease. Serum adiponectin levels correlate with insulin sensitivity and lipid metabolism [6,7]. Recent studies have shown that decreased plasma adiponectin levels significantly correlate with the risk of various cancers such as esophageal [17], colorectal [18], breast [19], endometrial [20], prostate [21], renal cell [22], and gastric cancer [23]. Adiponectin may provide indirect protection against carcinogenesis by affecting insulin sensitivity and inflammatory states, it has direct anti-carcinogenic effects through the AMP-activated protein kinase (AMPK) system. Independent of AMPK activation, adiponectin decreases production of reactive oxygen species (ROS) [25], which may result in decreased activation of mitogen-activated-protein-kinase (MAPK) [26] and subsequently results in inhibition of cell proliferation
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