WASHINGTON, April 18 (Xinhua) -- Swiss researchers have proposed a possible solution for early cancer warning using a synthetic gene network implanted under the skin and a mole might appear if cancer is detected.

A study, published on Wednesday in the journal Science Translational Medicine, showed that the prototype device may recognize four most common types of cancer, namely prostate, lung, colon and breast cancer, at a very early stage when the level of calcium in the blood is elevated due to the developing tumor.

The early warning system comprises a genetic network that biotechnologists integrate into human body cells, which in turn are inserted into an implant. The encapsulated gene network is then implanted under the skin where it constantly monitors the blood calcium level.

According to the researchers, as soon as the calcium level exceeds a particular threshold value over a longer period of time, a signal cascade will initiate production of the body's tanning pigment melanin in the genetically modified cells. The skin then forms a brown mole that is visible to the naked eye.

Martin Fussenegger, professor with the Department of Biosystems Science and Engineering at ETH Zurich in Basel, said the mole appeared long before the cancer becomes detectable through conventional diagnosis.

Fussenegger said the mole does not mean that the person is likely to die soon but simply means clarification and whether necessary treatment is needed.

The researchers used calcium as the indicator of the development of the four types of cancer, as it is regulated strongly in the body.

Bones serve as a buffer that can balance out concentration differences. However, when too much calcium is detected in the blood, this may serve as a sign for one of the four cancers.

Fussenegger said that the service life of such an implant was limited. "Encapsulated living cells last for about a year, according to other studies. After that, they must be inactivated and replaced," he said.

The researchers have tested their early warning system in a mouse model and on pig skin. It functioned reliably during these tests. Moles developed only when the calcium concentration reached a high level.

However, scientists still have a long way to go before human testing can begin.

The concept of "biomedical tattoo", as Fussenegger described this new finding, would also be applicable to other gradually developing illnesses, such as neurodegenerative diseases and hormonal disorders.