NGEF and Familial prostate cancer: The mechanism of RhoA activation downstream of EphA receptors in prostate cancer cells is unknown but a number of GEFs such as Ephexin or Vav have been shown to be required for EphA-induced growth cone collapse, an event that closely resembles cell retraction during CIL (Cowan et al., 2005; Shamah et al., 2001).