Breast Cancer Cell (IMAGE) University of California - San Diego Caption Mammary cells found during pregnancy that express integrin beta3 (CD61) act as stem cells, capable of reconstituting a new mammary gland in mice. This property may be to blame for the more aggressive nature of beta3-expressing breast cancer cells. Shown is a section from a mammary 'outgrowth' harvested at lactation and immuno-stained for the epithelial markers E-cadherin (brown) and alpha-SMA (red). Credit UC San Diego School of Medicine Usage Restrictions None License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.