RAC1 and neoplasm: The tumor suppressor function of p140Cap has been historically ascribed to its unique ability to behave as an adaptor protein that interferes with the activity of several oncogenic circuitries, including receptor and non-receptor tyrosine kinase pathways, for instance Src, Egfr and Erbb2 signaling, and small GTPase signaling, involving Rac1 and Tiam1, thereby down-modulating key cancer-relevant phenotypes, foremost proliferation and invasion, involved in tumor progression and metastasis24.