Ethanol stimulates tumor progression and expression of vascular endothelial growth factor in chick embryos.

BACKGROUND

The mechanisms by which alcohol consumption causes cancer have not been established due to a lack of experimental studies.

METHODS

A chick embryo chorioallantoic membrane (CAM) model that bore human fibrosarcoma (HT1080) was used to determine whether the administration of physiologically relevant doses of ethanol could stimulate tumor growth, angiogenesis, metastasis, and vascular endothelial growth factor (VEGF) expression in tumors. HT1080 cells were inoculated onto the "upper CAM" on Day 8, saline or ethanol was administrated at a dose of 0.25 g/kg per day on the CAM, and the tumors were harvested on Day 17. VEGF mRNA and protein were determined by Northern blot analysis and enzyme-linked immunosorbent assay. Intratumoral vascular volume density (IVVD) was determined by point counting on periodic acid-Schiff-stained sections. Intravasation of HT1080 cells was determined using human-Alu polymerase chain reaction analysis. The effects of ethanol on VEGF expression and cell proliferation were examined in cultured HT1080 cells.

RESULTS

Ethanol treatment for 9 days caused a 2.2-fold increase in tumor volume (867 +/- 138 mm(3) vs. 402 +/- 28 mm(3)), a 2.1-fold increase in IVVD (0.021 +/- 0.004 mm(3)/mm(3) vs. 0.010 mm(3)/mm(3) +/- 0.002 mm(3)/mm(3)), and a significant increase in VEGF mRNA or protein expression in tumors compared with a group of control embryos (n = 6 embryos; P < 0.01). Ethanol treatment caused an increase > 8-fold in the intravasated HT1080 cells in the CAM group compared with the control group (n = 6 embryos; P < 0.01). Physiologically relevant levels of ethanol (10 mM and 20 mM) caused a dose-related increase in VEGF mRNA and protein expression in cultured HT1080 cells. The ethanol-HT1080-conditioned media increased the proliferation of endothelial cells, but not of HT1080 cells.

CONCLUSIONS

The findings suggest that the induction of angiogenesis and VEGF expression by ethanol represents an important mechanism of cancer progression associated with alcoholic beverage consumption.