Immune Cells Caught on Video Eating Live Skin Cancer Cells : ScienceAlert
For roughly 15 years, medical professionals have utilized immune checkpoint inhibitors to treat melanoma, the most dangerous form of skin cancer. While these drugs produce remarkable results for many, they remain ineffective for others.
Researchers are now investigating why these therapies fail. New research published in the Journal of Experimental Medicine suggests that a specific type of immune cell may hold the key to improving patient outcomes.
The Challenge of “Cold” Tumors
Oncologists categorize certain cancers as “cold” tumors. In these environments, the cancer actively prevents T cells—a critical type of immune cell—from attacking the malignancy.
A primary goal for researchers at the Garvan Institute in Sydney is determining how to make these tumors “hot.” This transition would allow T cells to penetrate and destroy cancer cells more effectively.
The Role of the “Biological Boundary”
Macrophages have long been viewed as the body’s silent housekeepers, tasked with clearing debris from tissue damage and cell death. Because they are tissue-resident and stay in one place, their role in cancer has often been overlooked.
Researchers identified a specific kind of macrophage, recognised by a protein called CD169, located in the hypodermis—a deeper layer of the skin. These cells arrange themselves around the edges of melanoma tumors, effectively attempting to wall them off.
Evidence suggests these cells constrain tumor growth. When these macrophages were depleted, the melanomas grew larger, indicating a protective role.
Observing Live Cancer Attacks
Using intravital two-photon microscopy, researchers observed biological processes in living tissue in real time. They discovered that CD169-positive macrophages were actively “nibbling” and engulfing live melanoma cells.
This attack occurred independently of T cells or antibodies produced by B cells, which are the immune players typically credited with fighting cancer. This finding was further supported by the Melanoma Institute Australia, which found similar macrophage populations on the edges of tumors in human patients.
Implications for Future Therapy
Beyond clearing debris, macrophages can act as biological “red flags.” After digesting debris, they can alert the immune system and direct T cells to locate and kill cancer cells.
Because macrophages are widespread in various solid tumors, including breast cancer and glioblastoma, they represent a potential target for mobilization.
Potential Next Steps
Future research may focus on the precise mechanisms macrophages use to consume live cancer cells. Understanding how these cells communicate danger to T cells could lead to the development of new treatments.
If scientists can harness this population, it may be possible to create therapies that work for a wider range of patients, regardless of whether their tumors are initially “hot” or “cold.”
Frequently Asked Questions
What are CD169-positive macrophages?
They are a specific type of tissue-resident immune cell found in the hypodermis (deep skin) that can form a boundary around melanoma tumors and engulf live cancer cells.
How does this differ from traditional cancer-fighting immune responses?
While most cancer-fighting responses rely on T cells and B cells, these macrophages were observed attacking live melanoma cells without the need for those specific immune players.
Could this research help other types of cancer?
Since macrophages are present in most solid tumors—including glioblastoma and breast cancer—this research could potentially be applied to various other malignancies.
Do you believe that focusing on the body’s “resident” immune cells could change the way we approach cancer treatment?