Tumor angiogenesis increases in chronically stressed animals. (A) microvessel density was higher in the stress groups than in the control, the vessel density was calculated statistically using Image Pro Plus 6.0 software (Media Cybernetics Inc., Bethesda, MD, USA). (B) the expression levels of VEGF, MMP-2, and MMP-9 in the tumor samples from control and stressed animals were determined by immunohistochemistry, all photographs were taken at 400×. (C) the expression of VEGF, MMP-2, and MMP-9 at mRNA level in the tumor samples. (D) quantification of mRNA by RT-PCR. (E) the protein expression of VEGF, MMP-2, and MMP-9 was determined using western blot analysis. (F) quantification of western blot data. Data from at least three independent experiments with duplicate determinations are expressed as means ± SEM. *P < 0.05 vs control.