Impaired tumor growth, metastasis, angiogenesis and wound healing in annexin A1-null mice

Despite 2 decades of research, no clear function for annexin A1 (AnxA1) has been established. Using AnxA1-KO mice, we show that tumor growth and metastasis are significantly decreased, whereas rodent survival and tumor necrosis are greatly increased when tumors grow in AnxA1-KO mice. Systems analysis of gene expression in these tumors specifically implicates 2 related vascular functions, angiogenesis and wound healing, in this impairment. Both tumor vascular development and wound healing are greatly retarded in KO tissues. Aortic ring assays reveal induced AnxA1 expression on sprouting endothelial cells of normal mice whereas KO aortas exhibit impaired endothelial cell sprouting that is rescued by adenoviral expression of AnxA1. Key differences in specific gene regulation may define new molecular pathways mediating angiogenesis, including a reset profile of pro- versus anti-angiogenic factors, apparently distinct for physiological versus pathological angiogenesis. These studies establish novel pro-angiogenic functions for AnxA1 in vascular endothelial cell sprouting, wound healing, and tumor growth and metastasis, thereby uncovering a new functional target for repairing damaged tissue and treating diseases such as cancer. They also provide critical new evidence that the tumor stroma and its microenvironment can greatly affect tumor progression and metastasis.