Researchers at Wake Forest Univ. School of Medicine discovered a treatment effective in mice at blocking the growth and shrinking the size of lung cancer tumors, one of the leading causes of cancer death in the world.
The study is the first to show that treatment with a specific peptide, angiotensin-(1-7), reduces lung tumor growth by inhibiting blood vessel formation.
“If you’re diagnosed with lung cancer today, you’ve got a 15% chance of surviving five years – and that’s just devastating,” says co-lead investigator Patricia Gallagher.
The lung cancer survival rate has changed little in the past 30 years, says E. Ann Tallant.
Peptides, found in all animals, are compounds formed by linking one or more amino acids together through the sharing of electrons. They are among the building blocks of life. Peptides can perform a wide range of functions in the body, depending on which amino acids are involved. Some can regulate hormones, for example, while others can have an antibiotic function.
Angiotensin-(1-7) is a small peptide that binds to proteins on the surface of cells and prevents cell growth – but only if the cell is actively growing when the binding occurs. That property is what led Tallant and Gallagher to explore the peptide’s uses for treating cancer by blocking tumor growth.
Angiotensin-(1-7) works by inhibiting the production of signals sent out by a cancer tumor for food. For tumors to grow, they need nutrients delivered by blood vessels. The signals they send prompt blood vessels to grow and invade the tumor to feed it.
Every day during the six-week study, researchers injected either saline or the angiotensin (1-7) peptide into mice growing human lung cancer tumors. Over the course of the study, the tumors treated with angiotensin-(1-7) shrunk, while the saline-treated tumors grew and, at the end of the study, the tumors treated with angiotensin-(1-7) weighed about 60% less than the tumors treated with saline. Analysis also showed that the tumors from mice treated with the peptide had significantly fewer blood vessels compared to the tumors from the saline-treated animals.
The researchers further tested angiotensin (1-7)’s affect on blood vessel formation, or angiogenesis, by treating chick embryos with the peptide – a procedure considered the gold standard for determining anti-angiogenic ability. They found that blood vessels continued to grow in a saline-injected control group, while blood vessel formation decreased by more than 50% in the embryos treated with angiotensin-(1-7).
Tallant and Gallagher says the treatment likely has applications beyond lung cancer – they have collected data showing it is effective on breast, colon and brain tumors, as well. The treatment also presents an attractive possibility for future human cancer therapy from a cost perspective. “Because it’s a peptide, it’s very small and can be made very easily,” Gallagher said. “We sometimes like to say we’re the aspirin of cancer therapy.”
Source: Wake Forest Univ. School of Medicine