University of Colorado School of Medicine

Denver, Colorado
Distinguished Professor, Endocrinology and Molecular Biology, University of Colorado School of Medicine


Approximately 75% 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, some also contain cancer cells that do not need estrogen and are resistant to these therapies. Dr. Kathryn Horwitz’s laboratory focuses on the hormones estradiol and progesterone and their role in breast cancer.

Since physicians identify different cell populations in breast cancers to prescribe combination treatments, Dr. Horwitz has been studying some of these cell populations. Her research showed how combination anti-hormone and anti-growth factor therapies can efficiently suppress multiple cell populations.

Dr. Horwitz is also studying the problem of tumor dormancy as luminal cancers often recur many years after initial diagnosis and treatment.  Her research has shown that dormant or “sleeping” tumors can be “awakened” by hormones. Thus, her team is continuing their studies to better 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 estradiol and progesterone in tumor arousal and recurrence. This work may also have a strong influence on the understanding and treatment of other hormone-related cancers, such as uterine and prostate cancer.


Dr. Kathryn B. Horwitz, Ph.D., is a Distinguished Professor at the University of Colorado Medical School. She attended Barnard College for her undergraduate studies and UT Southwestern Medical School for her graduate studies. After completing her postdoctoral work at UT San Antonio, Dr. Horwitz joined the faculty at the University of Colorado.

She has received many awards and honors throughout her career, including the National Cancer Institute’s Rosalind E. Franklin Award for commitment to cancer research. Dr. Horwitz was elected President of the Endocrine Society and received its Fred Conrad Koch Award for exceptional contributions to endocrinology. Additionally, as a well-known national and international scholar, she has served on multiple society boards, study sections and editorial boards, and she has mentored numerous trainees who hold senior faculty posts at many U.S. medical centers.

Dr. Horwitz’s lab has been supported by grants and fellowships from the National Foundation for Cancer Research, the Avon Foundation, the Breast Cancer Research Foundation, the National Cancer Institute of the National Institutes of Health, the Komen Foundation and the Department of Defense.

Related Content

What is Genomic Sequencing, and Who Can Benefit?

There’s a paradigm shift taking place in the world of cancer treatment. Experts are moving away from an organ-focused approach to treatment, like using radiation to treat the specific area affected by cancer. Instead, they’re looking at genomic sequencing.  Genomics is the branch of molecular biology concerned with the structure, function, evolution, and mapping of an individual’s genes. Regarding cancer, genomics allows experts to examine DNA to determine an individual’s risk of cancer through genomic sequencing. This means that oncologists can provide more individualized treatment options for patients using precision medicine.  How can cancer risk be determined through genomic sequencing? Parents pass along many traits to their children, such as hair and eye color. Unfortunately, the risk of developing certain types of cancer can also pass along. By examining DNA, experts can identify certain changes in a person’s DNA known for increasing their risk of developing various types of cancer. However, not all cancers pass genetically. In fact, only five to ten percent of all cancers are believed to have an inherited gene mutation. It is important to note that no test can provide exact answers about a person’s inherited cancer risk. Genetic testing can tell whether a specific genetic mutation exists in the DNA. However, it cannot tell whether an individual will develop the disease associated with that mutation later in life or not. What is the benefit of genomic sequencing? Genomic sequencing cannot prevent a cancer diagnosis but can help identify cancer-related DNA mutations. This means an individual can implement precautionary measures. These measures could include making healthy lifestyle changes, such as exercising regularly, ceasing smoking, or reducing alcohol consumption. Depending on the type of mutation, medications may be available to reduce one’s risk of developing cancer. Similarly, genomic sequencing may highlight the option of surgery to remove an organ or gland to prevent cancer from forming or promote undergoing more health screenings regularly.  Who should utilize genomic sequencing? Experts typically only recommend genetic sequencing for patients whose families have a history of certain cancers or patterns of cancer. Doctors may order genetic testing for people that have: Multiple first-degree relatives with cancer diagnoses; Numerous relatives who have been diagnosed with the same cancer on one side of the family; A family history of cancers linked to a single gene mutation, such as breast cancer, ovarian cancer, or pancreatic cancer; Family member(s) who has been diagnosed with more than one type of cancer; Family member(s) who has been diagnosed with cancer at a younger age than typically seen for that cancer, such as colon cancer; Close relatives who have been diagnosed with cancers linked to rare hereditary cancer syndromes, such as Hereditary Breast & Ovarian Cancer Syndrome (HBOC), Cowden Syndrome, or Lynch Syndrome; or Family member(s) who has been diagnosed with rare cancer, such as breast cancer in a male. Can we expect more research in genomic sequencing?  National Foundation for Cancer Research (NFCR) is committed to advancing genomic research and its potential to be the future of developing treatment plans for cancer patients. As such, NFCR funds a dozen world-renowned researchers paving the way in genomic research. […]

Breast Cancer Survivors Need to Take Actions to Reduce Their Increased Risk of Cardiovascular Disease

New Treatment & Renewed Hope for Triple-negative Breast Cancer Patients