Two recent studies have found that tumors don’t depend on blood vessels of the host alone. In fact, they are capable of making their own. Maybe this is the reason why some drugs which once proved very effective in treating cancer are proving less efficient now.

About 40 years ago, Judah Folkman of Harvard Medical School in Boston said tumors were dependent on the blood vessels surrounding them, and believed that stopping that blood supply might help kill cancer cells. Bevacizumab (Avastin), a drug approved in 2004 to restrict blood vessel growth, is now proving to be less effective.

Researchers studied tumor samples from patients with a type of brain cancer called glioblastoma, and found that these tumors had genetic markers, that suggested these blood vessels were originated from the tumors actually.

They injected these cells into the brains of mice, and noted that tumors developed with blood vessels of human origin.

Viviane Tabar, a neurosurgeon and stem-cell researcher at the Memorial Sloan-Kettering Cancer Center in New York City however is not clear if this ‘self-vascularizing’ capacity is widely present in other kinds of tumors too. “It would be very exciting if other tumor cells exhibit the same phenomenon,” she says. However, this is not the first time researchers have suggested this nature of cancer cells.

In 1999, Mary Hendrix, a cancer researcher now at Northwestern University in Chicago, Illinois, earlier noticed a similar effect in melanoma cells and called it “vascular mimicry.”

Hendrix even predicted Avastin could be less effective in future. She notes that there might be a lot of other ways to affect the vasculature.