Expression of Tie1, Tie2, and angiopoietins 1, 2, and 4 in Kaposi's sarcoma and cutaneous angiosarcoma

The angiopoietins are recently described growth factors for vascular endoth elium, The Tiel and Tie2 receptors are expressed by endothelium. Acquired i mmune deficiency syndrome (AIDS)-associated Kaposi's sarcoma (KS) and cutan eous angiosarcoma are malignancies of endothelial origin. KS involves prima rily the skin and mucosal surfaces and is common in AIDS patients. In an ef fort to determine whether the angiopoietins and Tie receptors play a role i n the pathobiology of angiosarcoma and KS, we studied the expression of ang iopoietin-1, angiopoietin-2, angiopoietin-4, Tiel, and Tie2 mRNAs in biopsi es of KS from 12 AIDS patients, in biopsies of cutaneous angiosarcoma from two patients, and in control biopsies of normal skin from three volunteers by in situ hybridization, Strong expression of angiopoietin-2, Tiel, and Ti e2 mRNAs was detected in the tumor cells of KS and cutaneous angiosarcomas, in contrast to the focal low-level expression in normal skin biopsies. Foc al low-level expression of angiopoietin-1 was seen in KS, cutaneous angiosa rcomas, and in normal skin. Focal low-level expression of angiopoietin-4 wa s identified in a minority of KS lesions. These findings suggest that the a ngiopoietins and Tie receptors may play an important role in the pathobiolo gy of KS and cutaneous angiosarcoma and identify additional potential-targe ts for therapeutic intervention in these vascular malignancies.