Back to the embryonic stage: Nodal as a biomarker for breast cancer progression.

The embryonic morphogen Nodal, a member of the transforming growth factor-β superfamily, is not expressed in the majority of normal adult tissues. However, a growing body of evidence indicates that Nodal expression re-emerges in a number of human cancers, including melanoma, glioma, endometrial, and prostate cancers. Reactivation of Nodal signaling in these tumors contributes to their aggressiveness. Strizzi and colleagues, in a paper published in this issue of Breast Cancer Research, investigate the clinical significance of Nodal expression in breast cancer. They report that Nodal expression is significantly greater in malignant versus benign breast disease. More importantly, Nodal levels correlated with grading, staging, and lymph node involvement, independent of the estrogen receptor/progesterone receptor or HER2 status. Collectively, these data suggest that Nodal could serve as a potential biomarker for invasive disease and a potential therapeutic target in breast cancer.