Zadka Ł, et al. Pol Arch Intern Med 2020.
INTRODUCTION: Exosomes are currently considered as the new biomarkers of colorectal cancer (CRC). Tetraspanins (CD9, CD63) belong to the well-known exosome markers, but can also be found on other subtypes of extracellular vesicles (EVs).
OBJECTIVES: The aim of this study was to estimate the expression level of exosome markers and EVs in CRC.
PATIENTS AND METHODS: The expression level of CD9 and CD63 antigens was evaluated by immunohistochemical (IHC) staining on 109 patients diagnosed with CRC. Immunohistochemistry results were verified by Nanoparticle tracking analysis (NTA), as well as Western Blot (WB) and Transmission electron microscopy (TEM) methods. Exosomes isolation was performed on solid tissues. The immunohistochemical expression of both tetraspanins was compared with expression of cellular proliferation marker Ki-67.
RESULTS: A significantly higher level in expression of exosome markers was observed in CRC compared to the normal colonic mucosa. The NTA method found significantly higher concentrations of nanoparticles in CRC tissues than in the normal controls. There was a strong positive correlation between exosome markers and Ki-67 antigen. The expression level of both tetraspanins was significant different for lymph node staging (N stage).
CONCLUSIONS: Exosome markers and EVs were more pronounced in CRC samples compared to the normal controls. Immunohistochemical evaluation of tetraspanins reflects the results obtained by the NTA. The process of exocytosis appears to play an important role in the pathogenesis of CRC. To the best of our knowledge, such analysis was carried out for the first time.