Lab Study Slows Breast Cancer Spread to Bone in Mice

THURSDAY, Nov. 12 (HealthDay News) -- An experimental drug reduced the spread of breast cancer into bone in mice, researchers say.

The drug -- Y27632 -- inhibits a protein called Rho-associated kinase (ROCK), which is over-produced in metastatic breast cancer. Inhibiting ROCK in the earliest stages of breast cancer reduced overall frequency of cancer spread (metastasis) by 36% and decreased metastatic tumor mass in bone by 77%, the researchers found.

The findings suggest that ROCK may prove to be a good target for new drug treatments to reduce the spread of breast cancer.

"While the primary tumor causes significant illness and requires treatment, metastasis accounts for over 90% of breast cancer-related deaths. There are no treatments to eradicate metastasis. Establishing ROCK's role in the spread of breast cancer and identifying agents to inhibit ROCK brings us one step closer to an approach that might reduce metastasis in the future," study senior author Dr. Michael Rosenblatt, professor of physiology and medicine at Tufts University School of Medicine, said in a university news release.

"We also found that using shRNA -- short hairpin RNA -- to knock down ROCK expression slowed metastasis. In order for cancer cells to migrate, an extensive transportation apparatus is required. ROCK directs the formation of this apparatus, but use of the ROCK inhibitor as well as shRNA rendered the cells' transportation mechanism ineffective, significantly reducing breast cancer metastasis to bone," study first author Sijin Liu, research instructor and member of the Rosenblatt Laboratory at Tufts, said in the news release.

"This study also revealed that a specific microRNA cluster, 17 through 92, is associated with ROCK expression and breast cancer metastasis. The microRNA cluster responded to ROCK inhibition, which provides insight into the mechanism driving metastasis and is a finding that will be of particular interest to researchers focused on the role of microRNAs in gene expression," Liu said.

The study was released online in advance of publication in the Nov. 15 print issue of the journal Cancer Research.

-- Robert Preidt

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SOURCE: Tufts University, news release, Nov. 3, 2009