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Doctors usually give breast cancer patients several cancer drugs; they claim that these drugs produce better results than treatment with just a single drug. Now researchers have found that two powerful drugs can cure breast cancer.

Researchers from the Massachusetts Institute of Technology (MIT) have discovered that erlotinib and doxorubicin have the capability to kill a particularly malignant type of breast cancer cells. 

Researchers had been studying complex cell-signalling pathways that control cells' behaviour: how much they grow, when they divide, when they die. In cancer, the cells grow uncontrolled and abnormally in the body.

Researchers believed that the only way to switch a cancerous cell into a less malignant state is by using different combinations of cancer drugs. They tested different combinations of 10 DNA-damaging drugs and a dozen drugs that inhibit different cancerous pathways, using different timing schedules. 

Of all combinations they tried, they saw the best results with pretreatment using erlotinib followed by doxorubicin, a common chemotherapy agent.

To prove that erlotinib and doxorubicin could kill cancer cells, the researchers conducted an experiment on mice that had tumours. A group of mice was given erlotinib and doxorubicin in different durations. Another group was given only chemotherapy or the erlotinib and doxorubicin drugs at the same time.  

The study found that the tumours shrank and did not grow back in those mice which were given erlotinib and doxorubicin in different durations. In the case of mice given only chemotherapy or the erlotinib and doxorubicin drugs at the same time, the tumours initially shrank but then grew back.

Researchers found that giving erlotinib between four and 48 hours before doxorubicin dramatically increased cancer-cell death. Staggered doses killed up to 50 per cent of triple-negative cells while simultaneous administration killed about 20 per cent. About 2,000 genes were affected by pretreatment with erlotinib, the researchers found, resulting in the shutdown of pathways involved in uncontrolled growth.

"Instead of looking like this classic triple-negative type of tumour, which is very aggressive and fast-growing and metastatic, they lose their tumorigenic quality and become a different type of tumour that is actually quite unaggressive, and very easy to kill," said Michael Lee, researcher at the MIT, in a statement.

If the drugs were given in the reverse order, doxorubicin became less effective than if given alone. 

"The research is groundbreaking in its demonstration that the principles of order and time are essential to the development of effective therapies against complex diseases," said Rune Linding, researcher at the Technical University of Denmark, in a statement. "As disease researchers, we must consider network states, and this and other studies serve as a model for a new generation of cancer biologists."

"Our findings illustrate how systems engineering approaches to cell signaling can have large potential impact on disease treatment," said Michael Yaffe, researcher at the MIT, in a statement.