KITLG and cancer: We have recently shown that inactivation of SCF E3 ubiquitin ligases by siRNA knockdown of either RBX1 or RBX2 (also known as SAG, Sensitive to Apoptosis Gene) sensitized human cancer cells to radiation [23], [24], [25], and that Sag knockout also sensitized mouse embryonic stem cells to radiation via inducing apoptosis [26].