Cancer cells killed by healthy cells

Yasuyuki Fujita of University College London and Yoichiro Tamori of Florida State University led an international team in discovering a process by which normal cells can kill off carcinoma cells.

Carcinomas originate in the layer of cells called the ephithelium. These cells make up the lungs and various glands as well as parts of the digestive tract. In the earliest stages of tumorigenesis, one or a few cancerous cells find themselves surrounded by normal, healthy cells. Sometimes those healthy cells are capable of killing the tumor cells, but in other cases, the cancer cells manage to evade them and replicate themselves. It seems that the healthy cells compete with the cancerous cells in some way. What allows them to do this? That was the question the team of scientists set out to answer.

Flies and mammals are both known to have a tumor suppressor gene called Lgl (which stands for lethal giant larvae—hey it was discovered in flies first). When functional, Lgl prevents cells from becoming cancerous. It was also known that Lgl worked in association with one or more hitherto unknown proteins. The team of scientists managed to trap Lgl’s binding partner, and discovered that it was a single protein subsequently named ‘Mahjong’.

Next, the researchers tested fly cells that were missing the Mahjong gene. When surrounded by normal cells, the Mahjong minus cells died, but when surrounded by other Mahjong minus cells, they didn’t die. They repeated this test with canine kidney cells and saw the same result. In other words, the Mahjong mutants were losing the competition with the normal cells. Over-expressing Mahjong also rescued Lgl mutants from dying, though the reverse was not true.

The scientists hope that this new information will help them give normal cells a competitive edge over tumor cells in the earliest stages of tumorigenesis.