New Cancer Drug Has Been Very Effective in Animal Trials
A new method of attacking cancer cells, developed by researchers in Australia, has proved surprisingly effective in animal tests.The method is intended to sidestep two major drawbacks of standard chemotherapy: the treatment’s lack of specificity and the fact that cancer cells often develop resistance to treatment.
The new method, called EnGeneIC, uses “minicells” to deliver a variety of agents to tumor cells, including both anti-cancer toxins and mechanisms for suppressing the genes that make tumors resistant to toxins.The “minicells” are generated from mutant bacteria which, each time they divide, pinch off small bubbles of cell membrane. The “minicells” can be loaded with chemicals and coated with antibodies that direct them toward tumor cells.No tumor cell, so far as is known, produces a specific surface molecule for toxins to act on. But 80 percent of solid tumors have their cell surfaces studded with extra-large amounts of the receptor for a particular hormone, known as epidermal growth factor.The “minicells” can be coated with an antibody that recognizes the receptor for epidermal growth factor, so they are more likely to attach themselves to tumors than to the normal cells of the body. The tumor cells engulf and destroy the “minicells”, a standard defense against bacteria, and in doing so are exposed to whatever cargo the “minicells” carry.
In one surprisingly effective test of the method, reported online Sunday in Nature Biotechnology, mice were implanted with a human uterine tumor that was highly aggressive and resistant to many drugs. All of the treated animals were free of tumor cells after 70 days of treatment; the untreated mice were dead after a month.
Dr. Robert M. Hoffman, of the University of California, San Diego, said that the “minicells” were “good strategy and good science” but that the researchers had implanted the human tumors under the mice’s skin, a position from which they do not usually spread through the body. So the experiments do not answer the question of whether “minicells” can attack metastasized cancer, he said.
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