In this study, to investigate the pharmacological effects of cetuximab in KRAS mutant-bearing CRC, we systematically examined the global expression changes in cetuximab-treated xenograft mouse tumors generated with KRAS mutant-harboring LS174T colorectal cancer cells and identified that significantly downregulated TNS4 by cetuximab is closely associated with oncogenic potential of a subset of CRC cell lines harboring KRAS activating mutations. The gene discussed is KRAS; the disease is colorectal cancer.