Discovery of a key marker in breast cancer tumors

July 24, 2017

Stat5 protein is a DNA-binding factor that regulates expression of certain genes, many of which remain unknown.  During pregnancy, Stat5 is activated by the hormone prolactin, and stimulates milk production in the breast. Rui and colleagues have recently shown that Stat5 is also active at a lower level in healthy breast cells in non-pregnant women.  In the new study they discovered that active Stat5 was lost in many breast cancers, especially as the tumors became more aggressive and metastatic.

The team investigated whether the tumor levels of active Stat5 were related to how well the patients did over the next 5-10 years after initial treatment.  After analysis of over 1,000 patients?? tumor samples, the team found that loss of Stat5 activity correlated with higher risk of death. This increased risk was especially pronounced in patients with early stage breast cancer, whose tumors did not show detectable evidence of spread to the nearby lymph nodes.

Previous studies in mice have indicated that Stat5 promotes breast tumor development; surprisingly in this study presence of Stat5 in human tumors were linked with more positive outcomes. 

The work was done in international collaboration with Dr. Guido Sauter and Dr. Lukas Bubendorf and their research groups at the Institute of Pathology, University of Basel, Switzerland, and with Dr. Juha Kononen at the DioMeda Life Sciences. The collaborators have pioneered the tissue microarray technology, which was critical for rapid analysis of the large number of samples.