Stem cells are the "fifth column" of cancer
Cornell University researchers working under the guidance of associate Professor Claudia Fischbach-Teschl have found that adipose tissue stem cells, often used for reconstructive surgery after operations to remove tumors of different locations, including mastectomies, in the presence of even single malignant cells can form a microenvironment that promotes the growth of cancerous tumors.
The mesenchymal stem cells of adipose tissue studied by the authors contribute to the restoration of the functions of damaged tissues, including by activating the formation of new blood vessels. Therefore, they are a promising material for tissue engineering and reconstructive surgery.
However, as it turned out, when cultured in an environment containing chemical compounds synthesized by tumor cells, stem cells isolated from adipose tissue do not differentiate into adipocytes. Instead, they begin to synthesize factors in large quantities that stimulate the growth of blood vessels (angiogenesis), and turn into myofibroblasts – cells involved in the development of tumors.
These changes lead to the densification of the extracellular matrix surrounding the cells, which is a characteristic sign of breast cancer (thanks to which the tumor can be detected by palpation).
Myofibroblasts make the surrounding tissue denser, which, according to the principle of positive feedback, triggers a cascade of further changes in the behavior of stem cells, leading to the creation of even more favorable conditions for tumor growth.
The images show the size of the tumor and the structure of collagen fibers in the absence (left) and in the presence (right) of stem cells.
The researchers observed such changes in a series of experiments with stem cells and breast cancer cell lines of varying degrees of aggressiveness. They collected the medium in which malignant cells were cultured, sowed stem cells into it and observed the changes taking place with them.
The main stimulators of the transformation of the stem cell phenotype into the myofibroblast phenotype were two factors secreted by tumor cells: transforming growth factor-beta (TGF-beta) and interleukin-8. The data obtained in laboratory conditions were confirmed in experiments on mice, in whose mammary glands stem and tumor cells were injected.
Indirect confirmation of experimental data is also the fact that obese women are at an increased risk of developing breast cancer. The presence of a large amount of adipose tissue also means the presence of a large number of corresponding stem cells, which, theoretically, can increase the risk of a tumor.
Article by Chandler et al. Implanted adipose progenitor cells as physicochemical regulators of breast cancer is published in the journal Proceedings of the National Academy of Science.
Evgeniya Ryabtseva
Portal "Eternal youth" http://vechnayamolodost.ru based on the materials of Medical Xpress: Some stem cells can trigger tumors.
13.06.2012