Microenvironmental Hypoxia Induces Dynamic Changes in Lung Cancer Synthesis and Secretion of Extracellular Vesicles

SIMPLE SUMMARY: Human cells can communicate with each other by releasing small packets of protein called ‘vesicles’ that are absorbed by other cells nearby and at distant locations, leading to major changes in biological activity. This is also the case for cancer cells within developing tumours, which become starved of oxygen when they outgrow local blood supplies. We wondered whether oxygen starvation might cause cancer cells to alter the protein cargo they package into vesicles, which could play an important role in supporting further tumour development. We found that under oxygen-starved conditions, cancer cells release far higher numbers of vesicles that are actively packed with proteins known to enhance tumour survival, support distribution to other body sites, and suppress patient immune responses. Cancer vesicles could therefore be used to develop new diagnostic tests that inform doctors about disease progression, and may also represent useful drug targets for new types of patient treatment. ABSTRACT: Extracellular vesicles (EVs) mediate critical intercellular communication within healthy tissues, but are also exploited by tumour cells to promote angiogenesis, metastasis, and host immunosuppression under hypoxic stress. We hypothesize that hypoxic tumours synthesize hypoxia-sensitive proteins for packing into EVs to modulate their microenvironment for cancer progression. In the current report, we employed a heavy isotope pulse/trace quantitative proteomic approach to study hypoxia sensitive proteins in tumour-derived EVs protein. The results revealed that hypoxia stimulated cells to synthesize EVs proteins involved in enhancing tumour cell proliferation (NRSN2, WISP2, SPRX1, LCK), metastasis (GOLM1, STC1, MGAT5B), stemness (STC1, TMEM59), angiogenesis (ANGPTL4), and suppressing host immunity (CD70). In addition, functional clustering analyses revealed that tumour hypoxia was strongly associated with rapid synthesis and EV loading of lysosome-related hydrolases and membrane-trafficking proteins to enhance EVs secretion. Moreover, lung cancer-derived EVs were also enriched in signalling molecules capable of inducing epithelial-mesenchymal transition in recipient cancer cells to promote their migration and invasion. Together, these data indicate that lung-cancer-derived EVs can act as paracrine/autocrine mediators of tumorigenesis and metastasis in hypoxic microenvironments. Tumour EVs may, therefore, offer novel opportunities for useful biomarkers discovery and therapeutic targeting of different cancer types and at different stages according to microenvironmental conditions.