Cancer Immunotherapy: New Target Found on Tumor Cells

Cancer researchers have identified a protein, typically found inside cells, appearing on the surface of malignant cells – a discovery that could open new avenues for immunotherapy targeting solid tumors. The unexpected presence of this protein, called Src, offers a potential “target” for the immune system to recognize and attack cancer, a long-sought goal in oncology.

The finding, published in Science, stems from work at the University of California San Francisco, where biologist Jim Wells and his team observed Src on the exterior of cancer cells, but not on healthy tissue. “It was certainly provocative and exciting to see this cancer-associated Src kinase now presented on the cell surface,” said Kathleen Yates, a biologist at the Broad Institute of MIT and Harvard University, who was not involved in the study.

The Challenge of Solid Tumor Immunotherapy

Immunotherapy – harnessing the body’s own immune system to fight cancer – has revolutionized treatment for some blood cancers. But, solid tumors, like those found in the lungs, breast, or colon, have proven far more resistant. One major hurdle is identifying specific targets on the cancer cell surface that the immune system can reliably recognize as foreign. Many cancer cells lack unique surface markers, or they shed those markers, allowing them to evade immune detection.

Src is a kinase, a type of enzyme that plays a role in cell growth and signaling. Normally, it resides inside the cell, involved in processes like cell division and communication. Its presence on the cell surface is unusual, described by Wells as an “accident” – a serendipitous observation that could have significant implications.

How the Discovery Was Made

Wells’ team was systematically studying the proteins present on the surface of cancer cells when they detected Src. The researchers confirmed the finding across multiple cancer types, consistently observing Src on malignant cells but not on healthy donor tissue. This specificity is crucial; a successful immunotherapy target must distinguish between cancer cells and healthy cells to avoid damaging healthy tissue.

What This Means for Treatment

The discovery doesn’t immediately translate into a new therapy, but it provides a promising starting point. Researchers can now investigate ways to exploit the presence of Src on cancer cells. One approach could involve engineering immune cells, such as T cells, to specifically recognize and bind to Src, triggering an immune response against the cancer. Another possibility is developing antibodies that target Src, marking cancer cells for destruction by the immune system.

However, Yates cautioned that it’s too early to predict clinical benefit. “They’ve accomplished a great deal. It is an outstanding question as to whether this will be translationally impactful,” she said. Further research is needed to determine how effectively targeting Src can shrink tumors, improve survival rates, and whether it can be combined with existing therapies.

Understanding Kinases and Their Role in Cancer

Kinases, like Src, are essential for regulating many cellular processes. When kinases become abnormally activated or overexpressed, they can contribute to uncontrolled cell growth and cancer development. Many existing cancer drugs work by inhibiting kinases, blocking their activity and slowing tumor growth. The National Cancer Institute provides detailed information on kinase inhibitors and their use in cancer treatment.

The Next Steps in Research

The immediate next steps involve a deeper understanding of why Src appears on the surface of cancer cells. Is it a result of genetic mutations, changes in cellular processes, or some other mechanism? Identifying the underlying cause could reveal additional targets for therapy. Researchers will also need to investigate whether Src is present on all cancer cells within a tumor, or only a subset. If only some cells express Src, it could limit the effectiveness of immunotherapy.

Further studies will focus on pre-clinical models – laboratory experiments and animal studies – to test the efficacy and safety of targeting Src. If these studies are promising, clinical trials in humans will be necessary to determine whether Src-targeted immunotherapy is effective and safe for cancer patients. The National Institutes of Health’s ClinicalTrials.gov website provides information on ongoing cancer clinical trials.

The Broader Context of Cancer Immunotherapy

The search for effective immunotherapies for solid tumors is a major focus of cancer research. While checkpoint inhibitors – drugs that block proteins that prevent the immune system from attacking cancer cells – have shown success in some patients, many tumors remain resistant. Identifying new targets, like Src, is crucial for expanding the reach of immunotherapy and improving outcomes for patients with solid tumors. The Cancer Research UK website offers a comprehensive overview of immunotherapy and its applications.

The discovery of Src on the surface of cancer cells represents a potentially significant step forward in this ongoing effort. While much work remains to be done, it offers a new avenue for developing more effective and targeted cancer treatments.