Zebrafish improve understanding of cancer growth
Experiments on zebrafish larvae have revealed how cancer cells harness the immune system to quicken the spread of the disease.
Researchers found that cancer cells are less likely to spread if white blood cells, the body's immune cells, are prevented from contacting the cancer cells.
Cancer cells are renowned for their ability to avoid being destroyed by the body's immune system. It now seems that cancer cells also co-opt the body's immune system to help them grow.
Researchers activated cancer in skin pigment cells, called melanocytes, by introducing a cancer-promoting gene, called an oncogene. The cancer cells were also tagged using a fluorescent protein so that they could be tracked as they moved through the zebrafish. As zebrafish are completely translucent it is easy to see cells as they move around the fish and grow.
Cancer cells were found to actively attract immune cells. Researchers discovered the chemical hydrogen peroxide was the attractant: hydrogen peroxide is a natural by-product of the body's energy producing processes.
To test this further, the researchers reduced the production of hydrogen peroxide in the zebrafish. They found that white blood cells did not move to the cancer site and fewer cancer cells formed. This also happened when the development of the zebrafish's immune cells was blocked.
As well as attracting white blood cells, researchers observed tethers linking together white blood cells and cancer cells. In some cases, when white blood cells started to leave the area they appeared to be held back by cancer cells.
The results were the same when using a different type of cancer cell and when the cancer cells were injected into mucus secreting cells instead of skin pigment cells.
Cancer growth in zebrafish resembles that in mammals, making it likely that the findings are applicable to human cancer growth. The research could lead to new therapies for early-stage cancer in humans.
Read more about animals in cancer research here.