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Carol Sartorius, PhD

Associate Professor, Department of Pathology,
University of Colorado Anschutz Medical Campus
Denver, Colorado

Current Research

Goal: To discover ways to improve treatment response in patients with estrogen receptor (ER)-positive breast cancer.

Impact: Drs. Sartorius and Horwitz focus on a rare population of cells found in ER-positive breast tumors, called luminal breast cancer stem cells, that may play a role in some recurrences of cancer. Targeting these cells could improve patients’ response to endocrine therapy and prevent recurrence.

What’s next: The team will continue to conduct laboratory tests of luminal breast cancer cells that exploit the cells’ weaknesses as a means of targeted therapy.

While there are several effective therapies available for estrogen receptor (ER)-positive breast cancer, one-quarter of patients will experience a recurrence of their disease. New drugs are now used in combination with endocrine therapy (such as tamoxifen or aromatase inhibitors) to treat patients with recurrent breast cancer. These prolong survival, but do not save lives. Drs. Sartorius and Horwitz are studying ER-negative cells—which often co-exist with the ER-positive cells—and may be the cells driving recurrence in ER-positive breast cancer.

Full Research Summary

Research area: Identifying the underlying causes of drug resistance and breast cancer recurrence and strategies to improve outcomes.

Impact: Breast cancers that are driven by estrogen—called estrogen receptor (ER)-positive breast cancers, have the best five-year prognosis of any breast cancer. In spite of 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 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.

Current research: Drs. Sartorius and Horwitz are studying the role of ER-negative breast cancer stem cells in drug resistance and recurrence of ER-positive breast cancers. 

What they’ve learned so far: The research team identified a small group of ER-negative cells that co-exist with ER-positive cells in breast cancer. These cells are resistant to anti-hormone (endocrine) therapies and have stem cell-like qualities that make them resistant to other drugs used in combination with endocrine therapies in patients with advanced breast cancer. They have discovered that these ER-negative cells have unique proteins that regulate cell shape and movement, which might explain why they lead to disease progression, and could be potential therapeutic targets.

What’s next: They will build on recent findings to target vulnerabilities in these ER-negative cells with the goal of developing unconventional strategies to improve response to endocrine therapy by targeting these cancer stem cells.


Dr. Sartorius 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 an Associate Professor 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+ 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+PR+ 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.

Grid Researcher Headshot -  Sartorius Carol

BCRF Investigator Since


Donor Recognition

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

Area(s) of Focus