Additive effect of radiosensitization by 2-deoxy-D-glucose delays DNA repair kinetics and suppresses cell proliferation in oral squamous cell carcinoma.

BACKGROUND: It has well known that, compared to normal cells, tumor cells have a different manner of energy metabolism, which influences the sensitivity of radiotherapy. However, whether inhibition of glycolysis enhances the efficacy of radiotherapy is a matter of debate in oral squamous cell carcinoma (OSCC). The aim of this study was to characterize whether the combination of radiotherapy with the glucose inhibitor 2-deoxy-D-glucose (2-DG) affected DNA repair kinetics. METHODS: To compare the synergistic effect of 2-DG, we examined the cell survival after treatment with radiation, 2-DG, and a combination of the two in five OSCC cell lines and one lip fibroblast cell line, determined using clonogenic survival assay. Changes in the protein levels of DNA repair kinetics such as PARP, Rad51, and Ku-70 were analyzed by Western blotting. Then, using one of the five OSCC cell lines, we assessed the inhibition of xenograft tumor growth in vivo. RESULTS: We found that 2-DG with radiation induced significant inhibition of cell proliferation in cell line SAS (P<.01, one-way ANOVA). Radiation treatment was associated with decreased expression of the DNA repair markers. In additional, combinational treatment with 2-DG and radiation significantly inhibited the xenograft tumor growth compared to the control (P<.05), and treatment with 2-DG or radiation alone. CONCLUSIONS: Our study suggests that 2-DG has synergistic cytotoxic effects when combined with radiotherapy, which might lead to the design of an effective metabolic target therapy in vitro and in vivo.

Hypoxia-induced epithelial-mesenchymal transition is regulated by phosphorylation of GSK3-ß via PI3 K/Akt signaling in oral squamous cell carcinoma.

OBJECTIVE: Epithelial-mesenchymal transition (EMT) plays an important role in cancer invasion and metastasis induced by hypoxia. Here, we examined whether phosphorylation of GSK3-ß via phosphoinositide 3-kinase (PI3 K)/Akt signaling is involved in enhancing the hypoxia-induced EMT in oral squamous cell carcinoma (OSCC). STUDY DESIGN: Experiments were performed in OSCC cell lines (HSC-2, HSC-3, HSC-4, SAS, and HO-1-U-1) under normoxic or hypoxic conditions. The EMT was assessed by Matrigel invasion assays and wound healing assays. OSCC cell lines (HSC-2 and HSC-4) overexpressing hypoxia-inducible factor (HIF)-1α were established to examine the effects of HIF-1α on EMT-related factors. Immunohistochemical staining was performed to examine phosphorylation of GSK3-ß in 33 cases of tongue squamous cell carcinoma. RESULTS: Under hypoxic conditions, OSCC cell lines exhibited HIF-1α expression and showed evidence of the EMT. In cells overexpressing HIF-1α, the levels of phospho-Akt and phospho-GSK3-ß were increased, resulting in induction of the EMT. Inhibition of GSK3-ß phosphorylation suppressed these effects. Moreover, the intensity of pGSK3-ß staining was significantly increased with cN stage and cTNM stage in patients with tongue squamous cell carcinoma. CONCLUSIONS: Our data showed that the hypoxia-induced EMT in OSCC was enhanced by GSK3-ß phosphorylation, suggesting that GSK3-ß may be important in the invasion and metastasis of OSCC.

Relationship of regional adiposity to insulin resistance and serum triglyceride levels in nonobese Japanese type 2 diabetic patients.

The aim of this study was to investigate the relationships between insulin resistance and regional abdominal fat area, body mass index (BMI), and serum lipid profile in nonobese Japanese type 2 diabetic patients. A total of 63 nonobese Japanese type 2 diabetic patients aged 45 to 83 years were examined. The duration of diabetes was 8.4 +/- 0.8 years. BMI, glycosylated hemoglobin (HbA(1c)) levels, and fasting concentrations of plasma glucose, serum lipids (total cholesterol, high-density lipoprotein [HDL] cholesterol, and triglycerides), and serum insulin were measured. The low-density lipoprotein (LDL) cholesterol level was calculated using the Friedewald formula (LDL cholesterol = total cholesterol - HDL cholesterol - 1/5 triglycerides). Insulin resistance was estimated by the homeostasis model assessment (HOMA-IR). Computed tomography (CT) was used to measure cross-sectional abdominal subcutaneous and visceral fat areas in all the patients. Adipose tissue areas were determined at the umbilical level. Subcutaneous and visceral abdominal fat areas were 136.5 +/- 6.0 and 86.0 +/- 4.1 cm(2), respectively. Univariate regression analysis showed that insulin resistance was positively correlated with subcutaneous (r =.544, P <.001) and visceral (r =.408, P =.001) fat areas, BMI (r =.324, P =.009), HbA(1c) (r =.254, P =.001), serum triglycerides (r =.419, P <.001), and serum LDL cholesterol (r =.290, P =.019) levels and was negatively correlated with serum HDL cholesterol level (r =.254, P =.041). Multiple regression analyses showed that insulin resistance was independently predicted by the areas of subcutaneous (F = 6.76, P <.001) and visceral (F = 4.61, P <.001) abdominal fat and serum triglycerides (F = 8.88, P <.001) level, which explained 36.9% of the variability of insulin resistance. Moreover, the present study demonstrated that whereas BMI was positively correlated with visceral (r =.510, P <.001) and subcutaneous (r =.553, P <.001) fat areas, serum triglyceride level was positively associated with visceral (r =.302, P =.015), but not with subcutaneous (r =.222, P =.074) fat area. From these results, it can be suggested that (1) both subcutaneous and visceral abdominal fat areas are independently associated with insulin resistance and (2) visceral fat area, but not the subcutaneous one, is associated with serum triglyceride levels in our nonobese Japanese type 2 diabetic patients.