Antiretroviral therapies including a HIV protease inhibitor (HIV-PI) have reduced AIDS-KS incidence and induce KS regression in treated patients. This cannot be explained solely with drug-mediated HIV suppression and immune reconstitution. We have shown that HIV-PI such as Indinavir or Saquinavir block KS-like lesions in mice by inhibiting angiogenesis and tumor cell invasion through a blockade of matrix metalloprotease 2 (MMP2) proteolytic activation.