685 proteins were found to be selectively enriched in exosomes at more than five-fold higher level as compared to total cellular membrane proteins (Table S2), including 18 proteins, which were previously reported as potential lung cancer biomarkers, THBS1, ANXA6, HIST1H4A, COL18A1, MDK, SRGN, ENO1, TUBA4A, SLC3A2, GPI, MIF, MUC1, TALDO1, SLC7A5, ICAM1, HSP90AA1, G6PD, and LRP1 (Table 1). The gene discussed is MDK; the disease is lung cancer.