NEW YORK, June 03 (Reuters) -- Exercisers have been told that stretching should be an important part of their regimen. Likewise, it seems that tissue cells benefit from a micro-environment that compels them to stretch and flatten, and the resulting shape can mean the difference between cell life and death.
These findings, from a study published in Science, are of great interest to researchers studying tumor growth.
Most structural cells of the body must attach to each other and to the surrounding extracellular matrix in order to grow and develop normally. Attachment is facilitated by a class of proteins called integrins.
Only two types of cells can survive without attachment and spreading: cells that circulate in the blood, and some types of tumor cells, which leave the original tumor site and travel through the body to form metastatic tumors.
For other types of cells, lack of attachment can mean death by apoptosis, a kind of self-destruction that is programmed into cells, awaiting the appropriate chemical signal.
Dr. Christopher S. Chen and other researchers at Harvard Medical School studied this process in branching capillary networks, the framework of connections between arteries and veins. A full understanding of the suicide mechanism in capillary cells would give cancer researchers a powerful tool, since angiogenesis, or the formation of new blood vessels, is necessary for tumor growth.
The authors cultivated human and bovine capillary cells in the laboratory, where they were able to control cell growth and the degree of spreading by precise placement of growth factors within the culture medium.
Cells that were forced to spread out over a relatively large surface survived better and proliferated faster than cells that were allowed to have a more rounded shape. Cell shape determined whether individual cells lived or committed chemical suicide, regardless of other factors such as the type of adhesion proteins present in the medium.
The mechanism by which cells affect changes in cell geometry is not known. Living cells may be able to detect mechanical deformations in a cell or nucleus, "sensing their degree of extension or compression" and changing their expansion rate accordingly, the researchers suggest.
By the same token, this "shape-dependent regulation" may be lost when cells become malignant, leading to the unrestricted, chaotic growth that's characteristic of cancerous lesions, they say.
