Background: Pietras said that although prognosis for breast cancer is relatively good when detected in its early stages, metastatic disease is the cause of 90 percent of all cancer-related deaths. Therefore, learning more about the metastatic process and finding new cures to inhibit disease spread is at the center of clinical attention.
He explained that in order for a tumor to spread, a cancer cell must detach and traverse the vascular wall to escape into the blood stream, exit the vasculature to enter the metastatic site, and colonize the new tissue. The fact that the process of escape into and from the vasculature is regulated implies that it is possible to use drugs to block this process, he said.
How the Study Was Conducted: Pietras and colleagues used multiple mouse models of breast cancer; tumor samples from 768 patients in a population-based, nested case-control study; and breast cancer gene-expression data from The Cancer Genome Atlas, to understand the role of ALK1 in breast cancer metastasis and test an ALK1 inhibitor.
Results: Using multiple mouse models of breast cancer, Pietras and colleagues found that a mouse version of the ALK1 inhibitor dalantercept prevented metastatic dissemination and that combination therapy with dalantercept and the chemotherapy docetaxel was effective in preventing the spread of the primary breast tumor to the lungs.
Next, the researchers analyzed gene-expression patterns in tumors from 768 patients in a population-based, nested case-control study. This analysis showed that expression of ALK1 was significantly associated with the incidence of metastatic disease. In order to further validate their findings, Pietras and colleagues analyzed breast cancer gene-expression data from The Cancer Genome Atlas and found that ALK1 expression correlated with the expression of well-known endothelial markers and that higher levels of ALK1 expression were an independent prognostic factor for poor survival in breast cancer patients.
Author Comment: In an interview, Pietras said, "We are investigating the role of ALK1 protein expressed by endothelial cells in promoting metastatic dissemination from primary breast tumors. Our results suggest that the presence of high levels of ALK1 in the breast tumor vasculature is a prognostic biomarker for metastatic disease. Moreover, our work encourages clinical testing of drugs blocking ALK1 in breast cancer with prevention of metastatic dissemination as the primary outcome. We are currently performing therapeutic studies with dalantercept in models of breast cancer in order to pinpoint the precise therapeutic regimen and disease stage at which the treatment is the most effective."
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Main Finding(s): Breast cancer patients with high levels of the protein activin-like receptor kinase (ALK1) in the blood vessels of their tumors were more likely to develop metastatic disease. This makes inhibition of the ALK1 pathway a possible new target for the treatment of metastatic breast cancer.
Journal in Which the Study was Published: Cancer Research, a journal of the American Association for Cancer Research
Author: Kristian Pietras, PhD, the Goran and Birgitta Grosskopf professor of molecular medicine at Lund University
Funding & Disclosures: This study was funded by the European Research Council; the Swedish Research Council; the Swedish Cancer Society; the STARGET Consortium; BioCARE; Lund University; BRECT; the Karolinska Institutet and Stockholm County Council; and the Radiumhemmet, Karolinska Institutet, and Karolinska University Hospital. Pietras is an inventor on a patent pertaining to ALK1 antagonism held by the Ludwig Institute for Cancer Research Ltd., and licensed to Acceleron Pharma, a company that develops dalantercept for commercial purposes.
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Founded in 1907, the American Association for Cancer Research (AACR) is the world's oldest and largest professional organization dedicated to advancing cancer research and its mission to prevent and cure cancer. AACR membership includes more than 35,000 laboratory, translational, and clinical researchers; population scientists; other health care professionals; and cancer advocates residing in 101 countries. The AACR marshals the full spectrum of expertise of the cancer community to accelerate progress in the prevention, biology, diagnosis, and treatment of cancer by annually convening more than 25 conferences and educational workshops, the largest of which is the AACR Annual Meeting with almost 19,300 attendees. In addition, the AACR publishes eight prestigious, peer-reviewed scientific journals and a magazine for cancer survivors, patients, and their caregivers. The AACR funds meritorious research directly as well as in cooperation with numerous cancer organizations. As the Scientific Partner of Stand Up To Cancer, the AACR provides expert peer review, grants administration, and scientific oversight of team science and individual investigator grants in cancer research that have the potential for near-term patient benefit. The AACR actively communicates with legislators and other policymakers about the value of cancer research and related biomedical science in saving lives from cancer. For more information about the AACR, visit http://www.