Smart bomb drug zaps cancer cells in mice
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A smart anti-cancer bomb that acts like a Trojan horse can penetrate deep into tumours where it explodes and destroys cancerous cells without harming healthy ones, according to study findings published in the journal Cancer Medicine.
Researchers at the Massachusetts Institute of Technology (MIT) who devised the molecular size bomb tested it in mice with skin or lung cancer. Mice given the treatment lived more than three times longer than untreated rodents.
The scientists believe it could have the same effect in humans.
"We’re quite hopeful and optimistic that as we translate this into humans the results pan out as they have in animals,” Professor Ram Sasisekharan, of MIT’s Biological Engineering Division, said in an interview.
The smart bomb uses nanotechnology which manipulates materials on a molecular or atomic scale, to deliver chemotherapy drugs to destroy the tumour and anti-angiogenesis agents to block its blood supply.
Lung cancer usually occurs because some outside factor, called a carcinogen, has triggered the growth of abnormal, cancerous cells in the lung. These cancerous cells multiply out of control and eventually form a mass called a tumor. As the tumor grows, it destroys nearby areas of the lung. Eventually, the tumor’s abnormal cells can spread (metastasize) to nearby lymph nodes and to distant organs, such as the brain. In most cases, the carcinogens that trigger lung cancer are chemicals found in cigarette smoke.
Lung cancers are divided into two basic groups, non–small-cell lung cancer and small-cell lung cancer, based on the microscopic appearance of the tumor cells. These two groups are treated differently.
After the bomb, which is like a balloon within a balloon, is injected into the bloodstream it travels to the tumour and burrows deep inside. The outer membrane then disintegrates and releases an anti-angiogenesis drug so the blood vessels feeding the tumour collapse.
NO SIDE EFFECTS
The drug-packed nanocell trapped inside the tumour explodes unleashing the chemotherapy drug to kill the cancerous cells. No healthy cells are destroyed so debilitating side effects such as hair loss, vomiting, nausea and weight loss could be eliminated.
“If you don’t really shut the supply lines the tumour cells can escape and that is how they metastasise (spread). By killing the supply lines you are limiting the leaching of the chemotherapy agents to the healthy cells,” Sasisekharan said.
Eighty percent of the mice treated with the nanocell bomb lived longer than 65 days while rodents receiving the best chemotherapy lasted only 30.
Mice that had no treatment died at 20 days.
The smart bomb was more effective against melanoma than lung cancer which the scientists, who reported the findings in the science journal Nature, said shows the need to change the design of the bomb to attack different types of cancer.
“It’s an elegant technique for attacking the two compartments of a tumour, its vascular system and the cancer cells,” Judah Folkman, a cancer expert at the Children’s Hospital Boston, said in a statement.
Because the smart bomb, which is a new approach to drug delivery, uses existing drugs and materials the researchers think it could have a similar impact in humans.
They also believe it could be adapted to work for other types of cancer and illnesses and to test drug combinations.
“We’ve been able to show you can definitely decrease toxicity (of the drugs) and increase efficacy,” said Sasisekharan.
In melanoma, cells that give skin its color (pigment-forming cells) undergo cancerous changes and reproduce aggressively to form a life-threatening tumor. Melanoma, the deadliest form of skin cancer, is the seventh most common cancer in the United States, and is increasing at faster rates than any other cancer. Current estimates predict that one in 75 Americans will develop melanoma during his or her lifetime. In 1960, only one in 600 Americans was expected to develop this cancer.
Why melanoma rates are soaring isn’t known. It could be from increased exposure to the sun during recreational activities, or possibly from global changes, such as the depletion of the ozone, a gas in the atmosphere that absorbs many harmful solar rays. A person’s pattern of sun exposure appears to contribute more to the risk of developing melanoma than the total amount of lifetime sun exposure. Short bursts of intense sun appear most dangerous, especially if you get sunburned. Sun exposure can cause changes (mutations) in skin cells’ genes, the code within each cell that instructs the cell if, how, and when to duplicate itself. Recently, researchers identified a gene mutation that is shared by the majority of melanoma tumor cells. It is probably this gene mutation that starts the cancer.
Revision date: July 9, 2011
Last revised: by Andrew G. Epstein, M.D.
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