ARF1 and cancer: Western blotting, WST-1, and colony formation assays (Figure 5I-K) indicated that, unlike parental cells, ectopic ARF1 expression could not increase p-ERK expression or cell proliferation in IQGAP1-knockout HCT116 and RKO cells (Figure S6A-C), suggesting that IQGAP1 was essential for the ARF1 function in cancer.