Scientists in the US have identified a pathway that allows cancer to spread from one part of the body to other, a development they say may help to understand the disease better.
Jun-Lin Guan, a professor in the department of molecular medicine in the College of Veterinary Medicine at Cornell University, used a cultured cell line to study cancer, reports the university's website.
They used these cells to create a model system for cancer cells, which means its basic pathway exists in real-world systems while the actual proteins that act on the system may vary.
In the model system, the researchers discovered critical differences between cancer cells and normal cells regarding a mechanism called endocytosis -- which cells employ to let materials enter through the cell membrane, the report said.
They used a protein called v-Src derived from an oncogenic virus, which has the ability to transform a normal cell into one with many features resembling those found in cancer cells.
While this virus has not been found in humans, it does lead to tumour growth in chickens and created cancerous cells in the cultured system. In the study, they found that v-Src attaches to an enzyme, called focal adhesion kinase, inside the cell.
This association jumpstarts a series of cascading interactions between proteins in the cell that ultimately block some cell-surface proteins from entering through the cell's membrane.
One of the proteins not allowed entry is called MT1-MMP. As this material accumulates on the cell surface, it degrades the connective tissue that holds the cancerous cell in place. The build-up of MT1-MMP also activates an enzyme called MMP2, which further degrades the connective tissue.
In this way, the cancer cell loses its moorings and can float off to spread around the body. While no one has found v-Src in human cancer patients, a number of other cancers have been linked to viruses, including the herpes virus and its association with cervical cancer.
The study reveals how connective tissue holding a cancer cell in place might degrade, unmooring the diseased cell and allowing it to spread to other parts of the body.
"We looked at a relatively late stage of cancer and its spread within the body," Guan said. "The spreading part is less well understood, and it's the spreading that is killing people."
Medindia on Cancer: Further information
Cancer occurs when cells divide in an uncontrolled manner. In the human body, a process called cell division, constantly replaces the cells in the tissues that are lost. Normally, cells divide and produce the exact number of cells required. In cancer, cells divide for no apparent reason and form a mass of extra tissue becoming big enough to be noticed as a growth or tumor.
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