AN ANTI-CANCER “smart cell” that uses nanotechnology to penetrate tumours and destroy them from the inside has been developed in America.

The drug-packed “nanocell” has been successfully tested on two forms of cancer in mice, shrinking tumours and prolonging survival far more effectively than other therapies.

If the technique works as well in human beings, it could transform the treatment of many cancers, allowing doctors to harness nanotechnology to kill tumours without affecting healthy tissue.

At present, cancer is generally treated by surgery, or by chemotherapy and radiotherapy, which cause serious side-effects as they destroy healthy cells, too.

The potential of nanotechnology to improve on this, creating drugs that attack cancer cells alone, excites many scientists.

Ram Sasisekharan, Professor of Biological Engineering at the Massachusetts Institute of Technology (MIT), who led the research, said: “The fundamental challenges in cancer chemotherapy are its toxicity to healthy cells and drug resistance by cancer cells.”

He said that nanocells promised to overcome both problems.

In experiments on mice with melanoma, a form of skin cancer, and the Lewis variant of lung cancer, the nanocell proved considerably more effective than standard treatments.

Some 80 per cent of the mice with melanoma treated in this way survived for at least 65 days. This compared with survival of 30 days for mice treated with the best current therapy, and 20 days for untreated animals.

There were also benefits against lung cancer, though these were less dramatic, which suggests that the technology will need to be adjusted to attack different forms of the disease.

The nanocell developed at MIT measures 200 nanometres across — 500 times smaller than the thickness of a human hair — and combines two drugs that use different methods to treat cancer.

Its outer layer carries an “antiangiogenesis” agent that attacks the blood vessels with which tumours feed themselves. Beneath this it carries a chemotherapy drug that is toxic to cancer cells.

Professor Sasisekharan likened the plan of attack to “dropping the bombs while cutting the supply lines”.

Drugs that target angiogenesis are widely thought to be a good way to treat cancer, but they have a drawback: once the blood supply to a tumour is cut off, these vessels cannot be used to deliver drugs to kill it. The nanocell approach, described today in the journal Nature, gets around this by using the particular properties of very small particles.

The nanocell’s size means that it is taken up preferentially by tumour cells, but not by healthy tissue.

Once it is inside the tumour cell, the outer membrane disintegrates, releasing the antiangiogenesis drug and causing blood vessels feeding the cancer to collapse. The nanocell’s inner “balloon”, full of chemotherapy drugs, is then trapped inside the tumour, where it can release its lethal payload slowly without danger of damaging healthy tissue.

Shiladitya Sengupta, another member of the study team, said: “We designed the nanocell keeping the practical problems in mind. We created a balloon within a balloon, resembling an actual cell.”

Professor Sasisekharan said: “This model enables us rationally and systematically to evaluate drug combinations and loading mechanisms. It’s not going to stop here. We want to build on this concept.”

Other experts agreed that the approach was promising, though more research is needed to ensure that it is safe and effective in human patients.

Judah Folkman, of Children’s Hospital Boston, said: “It’s an elegant technique for attacking the two compartments of a tumour, its vascular system and the cancer cells.”

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