Progress in understanding tumor growth

Chinese researchers have identified a protein that enhances tumor growth by promoting the growth of blood vessels¹. The protein, β-arrestin1, is associated with a number of cell signaling pathways implicated in cancer growth.

The researchers used a strain of mice engineered to over-express β-arrestin1 to examine its effect on tumor progression. Malignant tumor cells were injected either under the skin or into the veins of the mice and the rate of tumor growth was compared to that seen in normal mice.

The tumors appeared faster and grew significantly larger in mice over-expressing β-arrestin1. In addition, the tumors in the β-arrestin1 mice had many more small blood vessels. Further investigation showed increased activity of the protein matrix metalloproteinase 9, and enhanced secretion of vascular endothelial growth factor — both associated with the process of blood vessel formation in tumors, known as angiogenesis.

The researchers observed a similar increase in matrix metalloproteinase 9 activity and small blood vessel formation in human microvascular endothelial cells in vitro.

Further experiments indicated that the phosphatidylinositol3-kinase (PI3K) signaling pathway was involved in angiogenesis enhanced by β-arrestin1.

The authors say their results point to a role for β-arrestin1 in promoting tumor growth in vivo by providing a suitable microenvironment for blood vessel formation.