Cancer cells are hard to get rid of because they continually find ways to evade treatment and survive. That's what a new study in Cancer Cell makes clear, says Tim Barribeau at the IO9 blog. The researchers studied anti-angiogenic therapies, which shrink tumors by going after pericytes — the cells that help tumors make blood vessels to feed themselves. They found that while tumors in pericyte-knockdown mice with actually shrank, that result was accompanied by "a threefold increase in the formation of secondary tumors," Barribeau says. "By cutting back on their size, the tumors metastasized far more readily."
So even though the treatment seemed to control the tumor's growth, says the study's senior author Raghu Kalluri, it actually enabled the cancer to spread. "When the blood supply is reduced to the cancer, it goes into survival mode, transitioning to having more mobile cells," Barribeau adds. "Without the pericytes, the blood vessels around the tumor become leaky, which the cancer cells are able to infiltrate far more readily, and spread to other region." When the researchers analyzed human breast cancer tumor samples, they found that, as in the mice, low pericyte levels were associated with metastasis and low survival rates.
But it's not all bad news, Barribeau says. The study shows that such metastases are also associated with an increased expression of Met, which is associated with cell migration and growth. Using Met-inhibitors could help prevent such metastases, Barribeau adds.