EGFR inhibitors promote an effective therapeutic response in about 50%–55% of the patients with Ras/Braf-wt CRC, whereas Braf- and Kras-mutant CRC cells are completely resistant.9 In accordance with clinical data, treatment with cetuximab affected the cell viability of about a half of the Ras/Braf-wt primary colorectal cancer sphere cells (CSphCs) and delayed the outgrowth of tumour xenografts (figure 1A, online supplemental figure 1A, B and online supplemental table 1). The gene discussed is KRAS; the disease is colorectal cancer.