Tumors are provocateurs
As we age, so-called resting malignant cells appear in various human organs. The number of these cells is extremely small and is not recorded by modern diagnostic methods. Such cells do not cause the formation of tumors, but scientists at the Whitehead Institute for Biomedical Research have found that the appearance of primary tumors in the body stimulates individual cancer cells to form "secondary" malignant neoplasms.
Until now, researchers have mainly been studying the effect of the tumor microenvironment on tumor growth and have paid much less attention to the effect of the general state of the body on this process. There are several publications that certain types of bone marrow cells are embedded in the stroma surrounding and feeding tumors. However, it was not clear whether the tumors are passive recipients of stromal progenitor cells circulating in the body, or actively attract stem cells from cellular reservoirs such as bone marrow.
As part of their work, the authors injected "provoking" human breast cancer tumor cells into animals simultaneously with passive "reacting" cells of human origin. Such passive cells formed extremely rapidly growing tumors, but only in the presence of provoking malignant cells.
In addition, scientists have found that the provoking tumor changes the state of the bone marrow, but the mechanisms of this effect remained unknown. Perhaps the primary tumor, with the help of some factors, mobilizes bone marrow cells that stimulate the growth of secondary tumors. An obligatory participant in this mechanism is the osteopontin synthesized by the primary tumor, but by itself it does not affect the growth of secondary tumors.
Provoking breast tumors also stimulated the growth of human secondary colon cancer fragments implanted in animals, which proves their ability to stimulate the growth of metastatic cells disseminated throughout the body and indicates the universality of the signaling mechanisms involved. This discovery casts doubt on the well-established hypothesis that primary tumors suppress the growth of their own metastases.
The clinical significance of the results of the work is evidenced by the fact that elevated levels of osteopontin are recorded in the blood of women with metastatic breast cancer. Theoretically, blocking with the help of specific antibodies of osteopontin or other tumor-produced factors that attract bone marrow cells to secondary tumors can prevent the generalization of cancer. This proposal is still hypothetical, but the authors emphasize that to date there are no methods of targeted treatment of metastases responsible for most deaths from cancer.
Portal "Eternal youth" www.vechnayamolodost.ru based on the materials of ScienceDaily
16.06.2008