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Carol Sartorius, PhD

University of Colorado Anschutz Medical Campus
Denver, Colorado

Titles and Affiliations

Professor, Department of Pathology

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. Sartorius and Horwitz’s BCRF research is to identify and test vulnerabilities in a common but understudied group of cells in ER-positive tumors that are ER-negative. This population of cells may be responsible for drug resistance and recurrence and behaves like cancer stem cells, which can initiate and drive cancer progression. By understanding how these cells promote tumor growth and identifying their weaknesses, she hopes to identify strategies to turn them off and prevent recurrence.

Progress Thus Far

In the last year, Drs. Sartorius and Horwitz finished developing endocrine and drug-resistant variants of ER-positive breast cancer from her new breast cancer model system. Her team has identified prospective mechanisms for expansion of ER-negative “stem cell” populations that may drive tumor progression and have found that these cells often increase in number during the course of hormonal therapies and can interact with other cells that enable their travel through the bloodstream to form sites of metastasis. The team have also pinpointed changes in tumor DNA that confer therapeutic resistance in ER-positive breast cancer.

What’s next

The team will use their ER-positive breast cancer model system to analyze the features and metastatic potential of circulating tumor cells and how long-term hormonal therapy affects them. In addition, Drs. Sartorius and Horwitz are analyzing changes in tumor cell DNA caused by a combination of long-term treatment with endocrine therapies and being in the bone environment, a common site of breast cancer metastasis. Understanding how hormone and drug environments impact ER-positive and metastatic breast cancer cells is imperative to stop disease progression.


Carol Sartorius, PhD earned her bachelor’s degree from the University of Michigan and PhD from the University of Colorado Health Sciences Center, both in Molecular Biology. She did her postdoctoral work at the University of Colorado Boulder and is currently a Professor of Pathology at the University of Colorado Anschutz Medical Campus (UC-AMC).

Dr. Sartorius’s research studies the biology, progression, and endocrine resistance of hormone receptor positive breast cancer. Her laboratory seeks to understand the molecular basis of transcriptional regulation by progesterone receptors (PR) and how this impacts estrogen receptors (ER) and tumor cell phenotype. Current research topics include hormone regulation of cancer stem cells and tumor heterogeneity, hormone regulation of metastasis, hormone control of translation and protein synthesis, and how host obesity and metabolic syndrome specifically affect ER-positive breast cancer and endocrine resistance. Dr. Sartorius’s team also specializes in developing hormone-dependent breast cancer models. She is the co-founder and co-director (with Dr. Peter Kabos) of the breast cancer patient-derived xenograft (PDX) bank at UC-AMC. Their collection emphasizes ER and PR-positive tumors. These tumor models are being characterized by genomic and proteomic techniques to discover novel hormone receptor interactions that can be leveraged for treatment. The goal is to improve hormone-directed therapies for breast cancer.

She is an active member of the Cancer Biology Training Program at UC-AMC with an interest in training the next generation of scientists in the field of hormones and cancer. Her laboratory trains predoctoral students, and postdoctoral and clinical fellows.

BCRF Investigator Since


Areas of Focus

Tumor Biology


Kathryn B. Horwitz, PhD

University of Colorado
Denver, Colorado