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Antibiotics as Cancer Treatments?

Commonly used drugs eradicate cancer stem cells

A way to eradicate cancer stem cells, using the side effects of commonly used antibiotics, has been discovered by a researcher at the University of Manchester in the U.K.

A new paper by Professor Michael P. Lisanti, published in Oncotarget, opens up the possibility of a treatment for cancer that repurposes drugs that have been safely used for decades.

Mitochondria are the source of energy for cancer stem cells as they mutate and divide to cause tumors. Cancer stem cells are strongly associated with the growth and recurrence of all cancers and are especially difficult to eradicate with normal treatment, which also leads to tumors developing resistance to other types of therapy.

Professor Lisanti worked with colleagues at the Albert Einstein College of Medicine in New York and at the Kimmel Cancer Center in Philadelphia. The team used five types of antibiotics –– including one used to treat acne (doxycycline) –– on cell lines of eight different types of tumor and found that four of them eradicated cancer stem cells in every test. This included glioblastomas, the most aggressive brain tumors, as well as lung, prostate, ovarian, breast, pancreatic, and skin cancer.

Mitochondria are believed to be descended from bacteria that joined with cells early in the evolution of life. This is why some of the antibiotics that are used to kill bacteria also affect mitochondria, although not to an extent that is dangerous to people. When mitochondria are present in stem cells, they provide energy for growth and, crucially, for division, and it is this process going wrong that leads to cancer.

In the laboratory, the antibiotics had no harmful effect on normal cells, and since they are already approved for use in humans, trials of new treatments should be simpler than with new drugs, saving time and money, according to the investigators.

 “This research makes a strong case for opening new trials in humans for using antibiotics to fight cancer,” Lisanti said. “Many of the drugs we used were extremely effective; there was little or no damage to normal cells; and these antibiotics have been in use for decades and are already approved by the FDA for use in humans. However, of course, further studies are needed to validate their efficacy, especially in combination with more conventional therapies.”

Importantly, previous clinical trials with antibiotics –– intended to treat cancer-associated infections, but not cancer cells –– have already shown positive therapeutic effects in cancer patients with advanced or treatment-resistant tumors.

In patients with lung cancer, azithromycin, the antibiotic used, increased 1-year survival from 45% to 75%. Even lymphoma patients who were “bacteria-free” benefited from a 3-week course of doxycycline therapy and showed complete remission of the disease. These results suggest that the antibiotic’s therapeutic effects were actually infection-independent, the authors say.

Source: University of Manchester; January 28, 2015.

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