OTC and acute lymphoblastic leukemia: Several approaches aimed at blocking the trophic activities of MSCs on blasts appear worthy of future investigations, such as, for example, GS inhibitors for ALL (Ehsanipour et al., 2013; Chiu et al., 2017), OTC inhibitors for T-ALL (Kwong-Lam and Chi-Fung, 2013) and Cyst(e)inase for CLL (Cramer et al., 2017).