CDC42 Inhibitors Alter Patterns of Vessel Arborization in Skin and Tumors in vivo

Abstract

Tumors that arise in the epidermis must develop a vascular supply to grow beyond a millimeter in depth. Despite this dependence on angiogenesis for tumor growth, melanoma tumors are minimally responsive to anti-angiogenesis agents. Existing methods to measure changes in angiogenesis rely on two dimensional approaches that have limited ability to capture changes in the three-dimensional architecture of the tumor vascular network. Here we integrate antibody infusion, optical tissue clearing, multiphoton imaging, and three-dimensional semi-automated tracing to quantify changes in the vascular architecture of skin and tumors. Initial studies used this new vessel visualization approach to demonstrate that RhoJ knockout mice have marked differences in vessel arborization in the skin despite having similar numbers of endothelial cells. Small molecules that inhibit CDC42 GTPases, which include RhoJ, RhoQ, and CDC42, inhibit tumor growth and vessel branching within tumors to a similar degree as Braf inhibitors. In contrast to Braf inhibitors, which only affect vessel arborization in tumors, CDC42 inhibitors alter vessel arborization in normal skin, colon, and human skin organoids. Taken together, these studies identify a new class of pharmacologic agents that inhibit vessel branching in both normal skin and tumors which could have utility in treating skin cancer and skin disorders characterized by pathologic angiogenesis.