Overexpression of GEFs, such as Tiam1 in gastric [20], prostate cancer [73], lung adenocarcinoma [74], and in squamous-cell carcinoma of the head and neck (SCCHN) [75], and Vav3 in prostate [76] and gastric cancer [77] may enhance Rac activity. Here, VAV3 is linked to head and neck squamous cell carcinoma.