By Gabriel Paijo 
Triple-negative breast cancer (TNBC) remains one of the most formidable challenges in modern oncology, accounting for approximately 10% to 15% of all breast cancer cases but a disproportionately high percentage of breast cancer deaths. Unlike other subtypes, TNBC is defined by the absence of estrogen receptors, progesterone receptors, and human epidermal growth factor receptor 2 (HER2) proteins. This "triple-negative" status means that common targeted therapies and hormone treatments are ineffective, leaving patients with limited options, primarily aggressive chemotherapy. While many patients initially respond to these treatments, the high rate of recurrence and the development of multi-drug resistance often lead to poor long-term outcomes. However, a landmark study published in the journal Breast Cancer Research offers a potential paradigm shift. Researchers at the MUSC Hollings Cancer Center have developed an experimental monoclonal antibody that targets a specific protein, secreted frizzled-related protein 2 (SFRP2), effectively slowing tumor growth, preventing metastasis, and "reprogramming" the immune system to recognize and attack cancer cells.
The study, led by Nancy Klauber-DeMore, M.D., a breast surgical oncologist and co-leader of the Developmental Cancer Therapeutics Research Program at Hollings, represents the culmination of nearly two decades of intensive investigation. By identifying SFRP2 as a master regulator of the tumor microenvironment, the research team has opened a new front in the battle against TNBC. The humanized monoclonal antibody developed by the team not only targets the cancer cells themselves but also addresses the surrounding "exhausted" immune system, providing a dual-action approach that could bypass the limitations of current standard-of-care treatments.
Understanding the Aggressive Nature of TNBC
To appreciate the significance of this breakthrough, one must understand the biological landscape of triple-negative breast cancer. TNBC is characterized by its high grade of malignancy, meaning the cells look significantly different from normal cells and divide rapidly. It is more prevalent in women under 40, African American women, and those with a BRCA1 genetic mutation. Because it lacks the three primary receptors used for targeting, oncologists have historically relied on "slash, burn, and poison" methods—surgery, radiation, and heavy chemotherapy.
The primary issue with chemotherapy in TNBC is the "selection pressure" it exerts. While the drugs kill a majority of the tumor, the surviving cells are often those that have mutated to resist the treatment. When the cancer returns, it is frequently more aggressive and resistant to the very drugs meant to stop it. Furthermore, TNBC is notorious for its early metastasis, often spreading to the lungs, brain, and bones before the primary tumor is even fully addressed.
The Role of SFRP2: A Key Cancer Enabler
The research at MUSC Hollings Cancer Center focused on SFRP2, a protein that the lab first linked to breast cancer in 2008. Over the years, Dr. Klauber-DeMore and her team discovered that SFRP2 is not just a byproduct of cancer but a primary driver of its survival. The protein facilitates "angiogenesis"—the formation of new blood vessels that feed the tumor—and inhibits "apoptosis," the natural process of programmed cell death that should, under normal circumstances, eliminate mutated cells.
Crucially, the study revealed that SFRP2 plays a devastating role in the immune microenvironment. It acts as a shield, preventing the body’s natural defenses from penetrating the tumor. By analyzing human tumor samples, the researchers found that SFRP2 was present in high concentrations not only on the cancer cells but also on the immune cells surrounding the tumor, such as tumor-infiltrating lymphocytes and tumor-associated macrophages.
Chronology of Discovery and Development
The journey toward this antibody began in 2008 when Dr. Klauber-DeMore’s lab first identified SFRP2’s involvement in breast cancer. The timeline of this research reflects the rigorous nature of translational medicine:
- 2008: Identification of SFRP2 as a potential biomarker and driver in breast cancer growth.
- 2009–2015: Investigations into the molecular pathways of SFRP2, revealing its role in Wnt signaling and its ability to stimulate the growth of endothelial cells (the lining of blood vessels).
- 2016–2020: Development of a humanized monoclonal antibody. Unlike mouse-derived antibodies, humanized antibodies are engineered to be compatible with the human immune system, reducing the risk of an adverse reaction and increasing the drug’s half-life in the body.
- 2021–2023: Preclinical testing in advanced models of TNBC, focusing on metastasis and chemotherapy resistance.
- 2024: Publication of findings in Breast Cancer Research, demonstrating the antibody’s ability to reprogram macrophages and kill chemo-resistant cells.
Reprogramming the Immune System: M1 vs. M2 Macrophages
One of the most significant findings of the study involves the "re-education" of macrophages. In a healthy body, M1 macrophages act as the "good" defenders, identifying and destroying pathogens or abnormal cells. However, tumors have the ability to hijack these cells, converting them into M2 macrophages. These "bad" macrophages actually suppress the immune system and promote tumor growth and tissue remodeling, effectively acting as collaborators with the cancer.
The SFRP2 antibody was found to reverse this process. Upon administration, the antibody triggered the release of interferon-gamma, a potent immune signaling molecule. This shifted the macrophage population back toward the M1 state. Unlike direct administration of interferon-gamma, which can be highly toxic to patients, the antibody-induced shift occurred locally within the tumor environment, minimizing systemic side effects.
Furthermore, the treatment addressed "T-cell exhaustion." In many TNBC cases, T-cells (the "soldiers" of the immune system) become overworked and enter a state of dysfunction where they no longer recognize the tumor as a threat. The research team, including surgical residents Lillian Hsu, M.D., and Julie Siegel, M.D., observed that the SFRP2 antibody restored the activity of these T-cells, suggesting that this therapy could be used in combination with existing immunotherapies, such as PD-1/PD-L1 inhibitors, to make them more effective.
Data Analysis: Precision and Efficacy Against Metastasis
The preclinical data provided by the MUSC team highlights the antibody’s potential for clinical success. In mouse models of advanced TNBC, those treated with the SFRP2 antibody showed a significant reduction in lung metastases compared to control groups. This is a vital metric, as lung involvement is a leading cause of mortality in breast cancer patients.
The study also tracked the "pharmacokinetics" of the antibody. Using specialized imaging, the researchers found that the antibody specifically accumulated in the tumor tissue. It did not linger in healthy organs or the bloodstream of non-cancerous models. This high level of precision is the "holy grail" of oncology, as it suggests that the drug can deliver a potent blow to the cancer without the debilitating side effects—such as hair loss, nausea, and organ damage—associated with traditional chemotherapy.
Perhaps most encouragingly, the antibody proved effective against doxorubicin-resistant cells. Doxorubicin, often referred to as the "Red Devil" due to its color and toxicity, is a mainstay of TNBC treatment. When the researchers tested the antibody on cancer cells that had evolved to survive doxorubicin, the SFRP2 antibody still induced significant cell death. This indicates that the antibody operates via a pathway entirely independent of traditional chemotherapeutic mechanisms.
Official Responses and Collaborative Efforts
The multidisciplinary nature of the project—involving MUSC’s departments of Surgery, Biochemistry, Molecular Biology, and Pathology—underscores the complexity of the research. Dr. Lillian Hsu expressed gratitude for the opportunity to contribute to a project with such high potential for patient impact, noting the meaningfulness of activating the immune system without adding new toxicities.
The antibody has been licensed to Innova Therapeutics, a biotechnology firm based in Charleston. The company, co-founded by Dr. Klauber-DeMore, is currently seeking the necessary funding to transition the research from the lab to the clinic. The goal is to initiate a Phase I "first-in-human" clinical trial to evaluate safety and dosage.
In a move that further validates the importance of SFRP2 as a target, the U.S. Food and Drug Administration (FDA) has already granted the antibody Rare Pediatric Disease and Orphan Disease designations for the treatment of osteosarcoma. Osteosarcoma is a rare bone cancer that also expresses high levels of SFRP2, suggesting that the implications of this research could extend far beyond breast cancer.
Broader Implications for the Future of Oncology
The discovery that SFRP2 is a central player linking tumor growth, immune suppression, and drug resistance represents a significant leap forward in precision medicine. If clinical trials prove successful, the SFRP2 antibody could become a cornerstone of TNBC treatment, either as a standalone therapy for chemo-resistant patients or as a sensitizing agent used alongside existing immunotherapies.
The ability to "re-engineer" the immune system’s ability to fight cancer from within marks a shift away from simply trying to kill cancer cells toward a more holistic strategy of fixing the broken biological environment that allows cancer to thrive. For the thousands of women diagnosed with triple-negative breast cancer each year, this research offers more than just a new drug; it offers the hope of a treatment that is as smart as it is effective.
While the transition from preclinical mouse models to human patients is a steep climb, the foundational data provided by Dr. Klauber-DeMore and her team at MUSC Hollings Cancer Center provides a robust roadmap. By targeting the very protein that helps cancer hide and grow, science is one step closer to turning a once-deadly diagnosis into a manageable, and perhaps curable, condition.
