A group of investigators in Italy have developed what they have termed 'xenopatients' to help identify novel biomarkers for patients. They used genetically characterized samples taken from 85 patients with metastatic colorectal cancer. These in vitro 'xenopatients' responded in a similar way to the anti-EGFR antibody cetuximab as the patients from whom they had been derived. Interestingly, in the cetuximab-resistant tumors that also had wild-type status for the genes KRAS, NRAS, BRAF and PIK3CA, 36% of the samples had HER2 amplification (in unselected tumors this was only found in 2.7% of cases). This amplification was also see in clinically non-responsive KRAS wild-type patients (13.6%). These results indicate that inhibition of HER2 and EGFR might offer a useful therapy option for these patients.