The p53 tumor-suppressor gene is inactivated in over 50% of all human
cancers, In normal cells, p53 induces growth arrest and apoptosis in r
esponse to DNA damage. We show that p53 acts as potent tumor-suppresso
r gene independent of its well-documented effects on tumor-cell prolif
eration and apoptosis. p53 activates target genes in a murine fibrosar
coma cell-line but does not affect tumor cell-cycle progression or sur
vival. Exogenous expression of wt-p53 does, however, block the angioge
nic potential of the tumor cells resulting in formation of dormant tum
ors in vivo. These data provide evidence that: (1) p53 acts as a tumor
suppressor gene independent of its anti-proliferative effects; (2) By
inhibiting angiogenesis p53 can indirectly induce apoptosis in vivo b
ut not in vitro; (3) p53-gene therapy which alters a tumors angiogenic
potential, can revert tumors to a dormant phenotype.