In this context, it is worth mentioning that Tybulewicz’s group has shown recently that deficiencies in either Rac or Vav family genes may favor the survival of TCRβ– thymocytes due to hyperactivation of the Notch signaling pathway [27], a route usually deregulated in human lymphoblastic leukemia [28]. Here, VAV1 is linked to acute lymphoblastic leukemia.