Figure 5B summarizes the involvement of RAC1 in tumorigenesis and drug-resistance. RAS signaling-mediated tumorigenesis and RAC1-PAK1 pathway-mediated resistance against RAS–RAF pathway-targeted drugs in cancers have been of particular interest. Mechanistic involvement of RAC1 in the development of chemo-resistance, radio-resistance, resistance to targeted therapies and immune evasion opened the opportunities for interfering RAC1 signaling pathway in cancer therapeutics [95]. This evidence concerns the gene PAK1 and cancer.