Other enzymes, such as PGI, PGK-1 and ENO-2, were found to be downregulated in an epidermal growth factor receptor (EGFR)-mutant non-small-cell lung cancer (NSCLC) with advanced resistance to EGFR tyrosine kinase inhibitors (TKIs), such as erlotinib. The gene discussed is EGFR; the disease is non-small cell lung carcinoma.