You are here

Kathryn B. Horwitz, PhD

Distinguished Professor
University of Colorado Denver
Denver, Colorado

Current Research

  • Seeking to identify the tumor cells responsible for drug resistance and breast cancer recurrence.

  • Laboratory studies are conducted to understand the significance of cancer cell subtypes in the initiation, growth and metastasis of luminal breast cancers.

  • This research will shed new light on the biology of luminal breast cancer that will inform new therapeutic strategies.

Approximately 75 percent of all breast cancers fall into the luminal classification and require estrogen to grow. While most of these cancers are treatable with anti-estrogen therapies, luminal cancers also contain cancer cells that do not need estrogen and are resistant to this therapy.

Therefore, when luminal cancers are treated, the hormone-responsive cells die but the rogue cells are not affected. These resistant cells are thought to be the cells responsible for tumor dormancy and later recurrence. 

Dr. Horwitz and BCRF collaborator Carol Sartorius and her team of basic and clinical investigators will utilize unique experimental and patient-derived luminal breast cancer models to understand the significance of cell subtypes in luminal cancers, their role in initiating tumors and in spawning dormant mini-tumors at metastatic sites, and the roles of the hormones estradiol and progesterone in awakening dormant tumor cells and breast cancer recurrence.

They will compare gene expression in tumor cells from metastatic or primary tumors to identify the genes that are necessary for survival in different organs. They believe that luminal tumors have different kinds of stem cells that direct tumor cells to different organs, and they will work to identify strategies to prevent this.


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


Donor Recognition

The Play for P.I.N.K. Award

Area(s) of Focus