Tumor angiogenesis affords new targets for
cancer therapy, since inhibition of angiogenesis suppresses
tumor growth by cutting out the supply of
oxygen and nutrients. Anti-angiogenic
therapy is thought to be free of the severe side effects that are usually seen with cytotoxic anticancer drugs. Furthermore, anti-angiogenic
therapy is thought not only to eradicate primary
tumor tissues, but also to suppress
tumor metastases. However, it is uncertain whether this
therapy causes
tumor regression because it inhibits only angiogenic events. Recently, a novel anti-angiogenic
therapy called anti-neovascular
therapy (ANET) has become notable. This
therapy inflicts indirect lethal damage on
tumor cells by damaging newly formed blood vessels using anti-
cancer drugs targeting the angiogenic vasculature, since cytotoxic anti-
cancer drugs cause damage to proliferating neovascular endothelial cells as well as
tumor cells. Moreover, neovascular endothelial cells would not be expected to acquire drug-resistance. Traditional
chemotherapy, which directly targets
tumor cells, has potential problems such as low specificity and severe side effects. On the contrary, in ANET, severe side effects may be suppressed, since traditional anti-
cancer agents are delivered to the neovessels by DDS technology. Besides the usage of DDS technology, anti-neovascular scheduling of
chemotherapy, or metronomic-dosing
chemotherapy, has also been attempted in which anti-
cancer drugs are administered on a schedule to damage neovessels. In this review, we describe traditional anti-angiogenic
therapy and ANET. We also discuss anti-angiogenic
cancer photodynamic therapy (
PDT), since
PDT is clinically applied to treat
age-related macular degeneration (AMD), in which uncontrolled angiogenesis occurs.