Despite numerous achievements and worldwide efforts to successfully cure cancer suffering patients, there is still a long way to go before achieving this goal. About 10 millions of people died from cancer over the world in 2020 1, making this pathology the first cause of premature death. From now, tumors are mainly diagnosed via medical imaging and biopsies analysis. The latter requires collecting tissues directly in patients and are then invasive and not optimal for daily monitoring. Thus, more precise and patient-friendly manners to evaluate the presence and evolution of tumors and metastasis are urgently needed to help for diagnosis and prognosis of the disease in both healthy and affected patients.
Extracellular vesicles as a biomarker
Could extracellular vesicles (EVs) be an answer by providing a promising diagnostic tool? The growing interest shown by the scientific community for these cell-secreted nanoparticles has led to deeper understanding of their biogenesis and functions. EVs comprise different types of vesicles, including exosomes (30-150 nm) that are formed in multivesicular bodies before being released from plasma membrane into extracellular matrix2. They can carry a variety of molecules including membrane-bound proteins, cytosolic proteins, DNA, coding and non-coding RNA, lipids, that constitute their cargo3.
Thus, upon release, EVs can serve as a powerful communication system by delivering information to the recipient cells in close environment or by entering general circulation4. Number of mechanisms can be initiated and/or stimulated by EVs, e.g. cell proliferation, tissue repairing, cell migration but also immunomodulation (pro- and anti-inflammatory signals)2. EVs content reflects the physiological state and the genetic material of the parental cell5.
Easily recovered from blood and other body fluids as urine, saliva, sweat, milk, cerebrospinal fluid (CSF) of patients, EVs then offer a direct and reliable window on general body situation allowing to discover potential abnormalities. It is worth noting that EVs are able to cross the blood-brain barrier from blood to CSF and conversely. It means that, in the blood, you can access information from the central nervous system, avoiding the quite invasive lumbar puncture to recover CSF6.
Role of extracellular vesicles in cancer
Whether they are good or bad guy, EVs play in cancer disease an important role too7. Tumors environment is highly complex and cells need to communicate in order to survive, proliferate, escape immune system, reshape their microenvironment and to have access to blood circulation via neoangiogenesis8–10.
For all these tasks, cancer cells secrete a large amount of EVs, even more compared to healthy cells and this could be explained by the strenuous environment surrounding tumor cells e.g. hypoxic11, acidic12 and inflammatory conditions. Not only to communicate between them, cancer cells also release EVs to influence the behavior of neighbor cells. One striking example is the induction, promoting and stimulation of the epithelial to mesenchymal transition mechanism by EVs, which is very significant for cancer metastasis5,13.
More importantly for clinic, these tumor cells-produced EVs harbor some specificities in terms of molecules that they carry. In our “omics” era, numerous methods are available to analyze multiple characteristics of EVs after isolation in terms of number and molecular content (PCR, RNA analysis, western blot, microscopy, flow cytometry, raman spectroscopy etc.)14. RNAs are strongly expressed in tumor cells secreted-EVs. Importantly, amount and types vary compared to normal cells.
Among RNAs, recent works show that micro RNAs (miRNA) are serious candidates as specific biomarkers, allowing to distinguish different types of cancer, with good accuracy15,16. EVs-miRNA-21 is the most reported biomarker and can help to detect glioblastoma, pancreatic, colorectal, colon, liver, breast, ovarian and esophageal cancers. miRNA-21 induces the production of vascular endothelial growth factor (VEGF) promoting angiogenesis17. Some protein cargos also emerge as possible diagnostic markers e.g. Glypican-1 for colorectal cancer18,19, Caveolin-1 and CD63 for melanomas, glioblastomas and prostate cancers20, epithelial growth factor receptor (EGFR) for brain cancers21, CD82 for breast cancers22, CD91 for lung cancers23. Although promising, proteins are still in study for potential cancer biomarkers. It then appears that an efficient diagnostic method should rely on multi-omics analysis, with different RNAs as well as proteins, to obtain precise conclusions.
Thus, developing breakthrough and innovative methods to reliably establish diagnostics in healthy, suspicious and cancer patients represents a major and promising goal for both clinical organizations and companies around the world. Many actors in health ecosystem such as Mursla (UK), Exosomics (Italy), Exosomedx (USA), Biological Dynamics (USA), Mercy BioAnalytics (USA), currently work on making these liquid biopsy technologies affordable, fast and user-friendly to ensure a smooth process from patients to clinicians. Each company develops their own innovating processes.
Mursla’s technology relies on millions of nanosensors per chip that provide excellent detection resolution and will focus on liver cancers. Exosomics isolates tumor-derived exosomes to analyze more reliably their contents. Exosomedx aims to detect prostate cancers by co-isolation of DNA and RNA to precisely analyze low abundant mutations occurring in early-stage diseases.
They commercialize ready-to-use diagnostic kits for urine testing. Biological Dynamics, along with their Verita platform, combine exosome detection with cell-free DNA to help early-stage diagnostic and fast patient support.
Reach out for more
1. Sung, H. et al. Global Cancer Statistics 2020: GLOBOCAN Estimates of Incidence and Mortality Worldwide for 36 Cancers in 185 Countries. CA. Cancer J. Clin. 71, 209–249 (2021).
2. Kalluri, R. & LeBleu, V. S. The biology , function , and biomedical applications of exosomes. Science 367, eaau6977 (2020).
3. Théry, C., Ostrowski, M. & Segura, E. Membrane vesicles as conveyors of immune responses. Nat. Rev. Immunol. 9, 581–593 (2009).
4. Valadi, H. et al. Exosome-mediated transfer of mRNAs and microRNAs is a novel mechanism of genetic exchange between cells. Nat. Cell Biol. 9, 654–659 (2007).
5. Mashouri, L. et al. Exosomes: composition, biogenesis, and mechanisms in cancer metastasis and drug resistance. Mol. Cancer 18, 75 (2019).
6. Chiasserini, D. et al. Proteomic analysis of cerebrospinal fluid extracellular vesicles: A comprehensive dataset. J. Proteomics 106, 191–204 (2014).
7. Xie, F. et al. Extracellular Vesicles in Cancer Immune Microenvironment and Cancer Immunotherapy. Adv. Sci. 6, 1901779 (2019).
8. Zhou, W. et al. Cancer-Secreted miR-105 Destroys Vascular Endothelial Barriers to Promote Metastasis. Cancer Cell 25, 501–515 (2014).
9. Ronquist, K. G., Ek, B., Stavreus-Evers, A., Larsson, A. & Ronquist, G. Human prostasomes express glycolytic enzymes with capacity for ATP production. Am. J. Physiol.-Endocrinol. Metab. 304, E576–E582 (2013).
10. Żmigrodzka, M., Guzera, M., Miśkiewicz, A., Jagielski, D. & Winnicka, A. The biology of extracellular vesicles with focus on platelet microparticles and their role in cancer development and progression. Tumor Biol. 37, 14391–14401 (2016).
11. Ramteke, A. et al. Exosomes secreted under hypoxia enhance invasiveness and stemness of prostate cancer cells by targeting adherens junction molecules: HYPOXIC-EXOSOMES ROLE IN PCA AGGRESSIVENESS. Mol. Carcinog. 54, 554–565 (2015).
12. Parolini, I. et al. Microenvironmental pH Is a Key Factor for Exosome Traffic in Tumor Cells. J. Biol. Chem. 284, 34211–34222 (2009).
13. Le, M. T. N. et al. miR-200–containing extracellular vesicles promote breast cancer cell metastasis. J. Clin. Invest. 124, 5109–5128 (2014).
14. Hilton, S. H. & White, I. M. Advances in the analysis of single extracellular vesicles: A critical review. Sens. Actuators Rep. 3, 100052 (2021).
15. Fitts, C. A., Ji, N., Li, Y. & Tan, C. Exploiting Exosomes in Cancer Liquid Biopsies and Drug Delivery. Adv. Healthc. Mater. 8, 1801268 (2019).
16. Kalluri, R. The biology and function of exosomes in cancer. J. Clin. Invest. 126, 1208–1215 (2016).
17. Liu, Y. et al. STAT3-regulated exosomal miR-21 promotes angiogenesis and is involved in neoplastic processes of transformed human bronchial epithelial cells. Cancer Lett. 370, 125–135 (2016).
18. Li, J. et al. GPC1 exosome and its regulatory miRNAs are specific markers for the detection and target therapy of colorectal cancer. J. Cell. Mol. Med. 21, 838–847 (2017).
19. Melo, S. A. et al. Glypican-1 identifies cancer exosomes and detects early pancreatic cancer. Nature 523, 177–182 (2015).
20. Logozzi, M. et al. High Levels of Exosomes Expressing CD63 and Caveolin-1 in Plasma of Melanoma Patients. PLoS ONE 4, e5219 (2009).
21. Graner, M. W. et al. Proteomic and immunologic analyses of brain tumor exosomes. FASEB J. 23, 1541–1557 (2009).
22. Wang, X. et al. Exosomal protein CD82 as a diagnostic biomarker for precision medicine for breast cancer. Mol. Carcinog. 58, 674–685 (2019).
23. Ueda, K. et al. Antibody-coupled monolithic silica microtips for highthroughput molecular profiling of circulating exosomes. Sci. Rep. 4, 6232 (2015).