Titles and Affiliations

Distinguished Professor
University of Colorado
Denver, Colorado

Research area

Discovering ways to improve treatment response in patients with estrogen receptor-positive breast cancer.


Breast cancers that are driven by estrogen—called estrogen receptor (ER)-positive, have the best five-year prognosis of any breast cancer. Despite effective therapies to treat ER-positive breast cancer, one-quarter to one-third of patients will experience a breast cancer recurrence. The goal of Drs. Horwitz’s and Sartorious’ BCRF research is to identify and test vulnerabilities in a common but understudied group of cells in ER-positive tumors that may be responsible for drug resistance and recurrence. By understanding how these cells drive tumor growth and identifying their weaknesses, they hope to identify strategies to turn them off and prevent recurrence.

Progress Thus Far

In the last year, Drs. Horwitz and Sartorius finished developing new models of ER-positive breast cancer that have several mutations prevalent in human breast cancer but not typically found in most laboratory models. They have made progress on their work to understand the function of a group of proteins that are prevalent in stem cell-like  cancer cells and are now extending this work to include triple-negative breast cancers. 

What's next

The team will use state-of-the-art technologies to identify factors that activate or repress the genes that give rise to cancer stem cell -like properties and/or that switch off the estrogen receptor, leading to resistance to anti-estrogen treatments. They hope to understand how stem cells affect tumors and how to prevent the switch to stem cell-like states.


Kathryn B. Horwitz, PhD joined the faculty at the University of Colorado after undergraduate studies at Barnard College, graduate studies at the UT Southwestern Medical School and postdoctoral work at UT San Antonio. Research in her laboratory is both basic and translational. It focuses on the role of women’s hormones – estradiol and progesterone – and their receptors, on luminal breast cancer cell heterogeneity, growth, treatment, metastasis and stem cells. Her lab has extensive expertise in molecular and tumor-cell biology, using in vitro and in vivo models and clinical samples. Long-term goals are to improve the strategies and outcomes of therapies for luminal disease. Research topics include: transcriptional mechanisms of progesterone receptors; epigenetic and post-transcriptional receptor modifications and signaling cross-talk; hormones in cancer growth; mechanisms of resistance to endocrine therapies; hormones and regulation of breast cancer stem cells; intratumoral cell heterogeneity in luminal disease; hormonal regulation of metastasis and the stromal microenvironment; development of new breast cancer models, and translation of laboratory findings into clinical practice. She has mentored numerous trainees who hold senior faculty posts at many US medical centers. She is a well-known national and international scholar, has served on multiple society boards, study sections and editorial boards, was elected President of the Endocrine Society, received its Fred Conrad Koch Award for exceptional contributions to endocrinology, and recently received the National Cancer Institute’s Rosalind E. Franklin Award for commitment to cancer research.

BCRF Investigator Since


Areas of Focus