γ-secretase inhibitor up-regulates vascular endothelial growth factor receptor-2 and endothelial nitric oxide synthase

Effect of DAPT, a gamma secretase inhibitor, on tumor angiogenesis in control mice

BACKGROUND

Notch signaling is a key factor for angiogenesis in physiological and pathological condition and γ-secretase is the regulator of Notch signaling. The main goal of this study was to assess the effect of (N-[N-(3,5-Diflurophenaacetyl-L-alanyl)]-S-phenylglycine t-Butyl Ester) DAPT, a γ-secretase inhibitor, on serum angiogenic biomarkers, and tumor angiogenesis in control mice.

MATERIALS AND METHODS

Tumor was induced by inoculation of colon adenocarcinoma cells (CT26) in 12 male Balb/C mice. When tumors size is reached to a 350 ± 50 mm(3), the animals were randomly divided into two groups: control and DAPT (n = 6/group). DAPT was injected subcutaneously 10 mg/kg/day. After 14 days, blood samples were taken and the tumors were harvested for immunohistochemical staining.

RESULTS

Administration of DAPT significantly increased serum nitric oxide concentration and reduced vascular endothelial growth factor receptors-1 (VEGFR1) concentration without changes on serum VEGF concentration. DAPT reduced tumor vascular density in control mice (280.6 ± 81 vs. 386 ± 59.9 CD31 positive cells/mm(2)), although, it was not statistically significant.

CONCLUSION

It seems that γ-secretase inhibitors can be considered for treatment of disorders with abnormal angiogenesis such as tumor angiogenesis.

Analysis of the expression of the Notch3 receptor protein in adult lung cancer

Abnormalities in the Notch signaling system are considered to play a role in the tumorigenesis of bronchiogenic carcinoma. The present study aimed to investigate the expression of Notch3 in adult lung cancer patients and its role in the pathogenesis of primary bronchiogenic carcinoma. The expression of the Notch3 protein in lung squamous cell carcinoma, adenocarcinoma, small cell carcinoma and corresponding non-tumor tissues was detected by immunohistochemistry. To investigate the expression of Notch3 in adenocarcinoma tissues, Notch3 mRNA and protein expression were measured with reverse transcription polymerase chain reaction (RT-PCR) and western blot analysis, respectively. It was demonstrated that Notch3 had a stronger positive degree of expression in lung squamous cell carcinoma and adenocarcinoma compared with the corresponding non-tumor tissue (P<0.01). The expression of Notch3 in small cell carcinoma tissue was lower compared with that of the corresponding non-tumor tissue (P<0.01). The expression of Notch3 in the lung adenocarcinoma group was the highest of the three lung carcinoma groups (P<0.01). RT-PCR revealed that the expression of Notch3 mRNA in the lung adenocarcinoma group was higher than that of the normal lung group, but there was no statistically significant difference (P=0.05). The expression of Notch1 protein in the lung adenocarcinoma group was significantly higher compared with the normal lung group (P<0.01), as shown by western blot analysis. Notch3 may be involved in the pathogenesis of bronchogenic carcinoma, in particular in the promotion of the lung cancer oncogene, and a difference in its expression may exist in the various pathological types.