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Role of Epigenetics and Surrounding Stroma in Metastasis
In an open-access review article published on Febraury 26, 2015 in the journal Clinical and Translational Medicine, researchers from Boston University School of Medicine (BUSM) shed new light on the underlying processes of tumor metastasis and highlight the role of epigenetics in this process. By comparing embryogenesis with cancer metastasis, the scientists hypothesize that reversible epigenetic events regulate the development of different types of metastatic cancers. They also describe that the surrounding cells of the tumors (stromal cells) play a significant role in this process. The BUSM researchers support the hypothesis that metastasis is more of a gradual process, leading to a heterogenic tumor population with cells of various epigenetic and differentiation statuses. They propose that cancer progenitor cells slow their growth while differentiating into more metastatic forms and then resume rapid division once the cells have metastasized to certain state or grade. Similar processes again take place when that grade of metastatic cancer changes to another grade. As this process is not a one-time event during tumor metastasis, the slowing of growth and increase in differentiation must happen many times. Once the desired grade is achieved, the reverse process needs to take place. Epigenetics is what allows the cells to transform reversibly. In accordance with this hypothesis, metastasized tumors of various types and prognoses demonstrate known epigenetic markers. Localization and growth of the metastatic tumor cells in distant location is another important event in tumor metastasis.