26 February 2008

Tumor vessels are formed from precancerous stem cells

For the growth of tumors, an abundant blood supply is necessary, but it is still unclear how they ensure the growth of the vascular network that feeds them. Scientists at Ohio State University, working under the guidance of Dr. Jian-Xin Gao, have found that the blood vessels of a tumor can be formed by precancerous stem cells.

The results obtained indicate that tumor vessels are mainly formed by the cells of the tumor itself (precancerous stem cells), and normal precursors of vascular endothelium give rise to only a small fraction of the cells that make up them. This explains the inability of many antiangiogenic drugs to block tumor growth. The fact is that the effectiveness of such drugs is tested on normal endothelial cells or their precursors, the properties of which may differ significantly from the properties of precancerous stem cells.

Normal stem cells are non-specialized and can give rise to various types of cells. The data obtained in recent years indicate that tumors consist of a small number of cancer stem cells and the bulk of malignant cells formed as a result of their division. It is believed that newly identified precancerous stem cells can either remain benign or become malignant under the influence of certain external influences.

As part of the work, the authors grew mouse precancerous stem cells in the laboratory and transplanted them to immunodeficient mice. After some time, the formed tumors were removed and analyzed for the presence of various molecular markers. The results of the analysis showed that the tumor blood vessels mainly consisted of cells whose precursors were transplanted precancerous cells. In appearance, these cells were markedly different from normal vascular cells.

Precancerous stem cells produced as many angiogenic (stimulating vascular growth) factors as typical tumor cells, however, they had much greater potential in the formation of new blood vessels and large tumor masses.

When studying the processes of formation of new blood vessels in human tumors transplanted to mice, the authors obtained results corresponding to the data obtained using a completely mouse model.

The study of human tumors of the cervix and breast revealed similar anomalies of appearance and distorted profiles of molecular markers in the cells of their blood vessels. This indicates that the ability of these tumors to form blood vessels is most likely associated with the precancerous stem cells that are part of them.

The article by Shen R. et al. "Precancerous Stem Cells Can Serve As Tumor Vasculogenic Progenitors" is published in the journal PLoS One

Portal "Eternal youth" www.vechnayamolodost.ru based on the materials of ScienceDaily


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