Further characterization of the exosomes by flow cytometry for exosome markers CD63 and CD81 [22] did not reveal any significant differences between the ESCC parental and resistant-cell derived exosomes (Additional file 3: Figure S2), indicating that the exosome population is the same between ESCC parental and resistant cells. The gene discussed is CD63; the disease is esophageal squamous cell carcinoma.