Mechanisms of stromal cell recruitment


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Robert A Weinberg
Whitehead Institute for Biomedical Research, Massachusetts, United States

Abstract

The recruitment of stromal cells to almost all carcinomas is essential for the vigorous growth of these tumors. In addition to tumor-associated neovasculature, a variety of other cell types must be incorporated into the tumor-associated stroma in order to enable malignant growth. In principle, this recruitment could come from the stroma of normal tissue that is adjacent to the incipient tumor. However, our work has demonstrated that more complex, systemic interactions are operative in some and perhaps all tumors. Thus, some aggressively growing tumors send signals to the bone marrow to stimulate the formation of tumor-promoting bone marrow cells of the hematopoietic lineage. Such cells are then mobilized into the circulation and can be recruited by distantly located tumors, including those that would, on their own, remain indolent. The resulting recruitment of such bone marrow derived cells enables the otherwise-indolent tumor to recruit an active stroma and grow vigorously. Hence, tumor growth must be viewed as a systemic process rather than one that is confined exclusively to the tissue in which a tumor arises.

Acknowledgements
Sandra McAllister, Brigham and Women's Hospital, Boston, USA