The expression of αvβ3 integrin and the receptor tyrosine kinase AXL was found to be upregulated in erlotinib-resistant NSCLC cell lines (HCC827 ER and HCC4006 ER), as well as in tumor specimens obtained from NSCLC patients who had developed acquired resistance to erlotinib [130]. The gene discussed is NTRK1; the disease is non-small cell lung carcinoma.