RB1 and angiosarcoma: Tumors that form in mice xenoengrafted with human ECs co-expressing viral antigens that inactivate tumor suppressors p53 and pRb, together with exogenous expression of hTERT and oncogenic Ras, could be used to model angiosarcoma or malignant hemangioendothelioma (Table 4) (Rhim et al., 1998; MacKenzie et al., 2002).