GK5 and adenocarcinoma: Zhou et al. have discovered that exosomal GK5 mRNA was significantly higher in the plasma of gefitinib-resistant adenocarcinoma patients than in the plasma of gefitinib-sensitive patients, and that the mRNA and protein levels of GK5 were significantly higher in gefitinib-resistant human non-small cell lung cancer PC9R and H1975 cells than in gefitinib-sensitive PC9 cells [43].