Using circulating tumor DNA (ctDNA) from patients with mCRC and with acquired cetuximab resistance....Cell viability analysis suggested that in the presence of cetuximab in combination with 10 μmol/L 5-FU, compared with mock transfected cells, DiFi cells overexpressing p.K944N, p.V955G, p.V955I, p.K966E, p.E542K, p.E545K, and p.H1047R exhibited a high degree of resistance...These results demonstrate that these candidate mutations are likely to be involved in conferring resistance...