Role of tumour derived exosomes in manuring the metastatic niche in patients with lung cancer liver metastasis: Beyond seed soil hypothesis

Metastatic lung cancer is often diagnosed at a late stage and is widely known to metastasize to the liver in the Asian population, but the underlying mechanism still remains unclear. Tumour derived exosomes (TDEs) play an important role in metastasis and its contributions to the development of the pre-metastatic niche formation is of utmost importance. In this study serum, derived tumour exosomes form lung cancer liver metastatic patients showed active incorporation by A549 cells in a concentration and time-dependent manner and induced migratory/invasive properties. Moreover, it was observed that cellular uptake of exosomes was increased during G2/M phase stimulating the cells to enter cell cycle phases leading to cell proliferation. Further, we observed that E-cadherin, beta catenin, VEGFA, CDKN2A and TGFBR2 were differentially expressed in treated A549 cells demonstrating an important role of these TDEs in altering the tumour microenvironment. In vivo model demonstrated an increase in serum SGPT and SGOT levels whereas the histopathological examination showed patches of pneumonitis in lungs and advanced inflammation in the liver. Conclusively, our results depict an undisputable role of these exosomes as key modulators in the formation of the pre-metastatic niche required for the colonization of circulating tumour cells (CTCs) ultimately leading to distant metastasis.