CRK and oral cavity squamous cell carcinoma: Since Nishihara et al. [66] reported overexpression of Crk in various cancer tissues, including lung, gastric, and breast cancer tissues, Crk has been reported to be overexpressed in glioblastoma [41,49,50,56], lung cancer [67], breast cancer [25], oral squamous cell carcinoma [53], bladder cancer [45], gastric cancer [68,69], and kidney cancer [56] tissues (Table 1).