A suppressor role for soluble endoglin in cancer

Elevated levels of a circulating form of the transforming growth factor-β (TGF-β) coreceptor endoglin correlate with poor clinical outcome in different types of cancer. Soluble endoglin (Sol-Eng) is primarily produced by cleavage of cell-surface endoglin by the transmembrane metalloprotease MMP14 that releases most of its extracellular domain. Sol-Eng has been found to contribute to different cardiovascular pathologies, including preeclampsia, a severe hypertensive syndrome of pregnancy. While the anti-angiogenic and pro-hypertensive functions of Sol-Eng appear well established, its role in cancer has not been fully investigated. Recently, we reported that Sol-Eng strongly inhibits signaling through the hepatocyte growth factor (HGF) tyrosine kinase receptor Met in mouse skin spindle carcinoma cells. Sol-Eng also blocked basal and HGF-mediated stimulation of carcinoma cell proliferation, migration and invasion. Taken together, the above results and the anti-angiogenic function exerted by Sol-Eng suggest a suppressor role for Sol-Eng in cancer. This conclusion is discussed in the paradoxical context of Sol-Eng as a marker of poor prognosis and as a potential contributor to the decreased risk of preeclamptic mothers to develop breast cancer later in life.