Glioblastoma is a devastating brain cancer, and standard treatment has not produced lasting survival gains. This review asks whether the body’s natural killer cells can be directed toward the tumor in several different ways. Glioblastoma multiforme is the most common type of primary malignant brain tumor and has a dismal overall survival rate.

To date, no therapy has yielded successful survival results beyond surgery, radiation, and chemotherapy. Natural killer cell-based immunotherapies are a rising candidate because they can approach glioblastoma from multiple therapeutic angles, including antibodies, checkpoint blockers, and specially modified killer cells.

Natural killer cells help identify cells that have become cancerous. Unlike some other immune cells, they do not require prior exposure to a specific target before they can respond. Their response depends on a balance: signals telling them to attack must outweigh signals telling them to hold back.

That lets them identify and eliminate abnormal cells without prior exposure or a matching signal from the body. A useful way to picture this is a security guard checking several clues at once. One warning alone may not be enough, but several separate warnings together can trigger action.

Natural killer cell activation appears to require different receptors to be engaged at the same time, often producing added or even stronger effects together. That gives treatment several possible routes: some approaches change the tumor’s interaction with natural killer cells, while others directly modify the killer cells.

Treatments can also be delivered in different ways. Checkpoint blockers are designed to interrupt molecular interactions that suppress immune activity. When those inhibitory checkpoints are blocked, the natural killer cell is pushed toward activation.

A key target, CD155, is overexpressed in glioblastoma and has a diverse range of functions that favor tumor growth and proliferation. It also mediates interactions between glioblastoma cells and natural killer cells through several receptors, including activating receptors and the inhibitory receptor TIGIT.

When CD155 on glioblastoma cells binds the inhibitory receptor TIGIT, it inhibits natural killer cell antitumor activity and benefits tumor-cell survival and proliferation. The picture maps several ways to redirect natural killer cells toward brain-tumor cells: recognize markers on the tumor, or release brakes that normally suppress attack.

The intended result is both direct tumor-cell killing and stronger immune signaling. Another possible brake is HLA-E. When it appears on cancer cells, it sends inhibitory signals to natural killer cells through a receptor called NKG2A, helping the cancer avoid immune attack.

Blocking this interaction is being discussed as a treatment strategy, but work in glioblastoma has so far remained in early laboratory studies. Animal studies and clinical patient studies have not yet been conducted.

The review’s overall conclusion is cautious: glioblastoma remains a deadly disease, and efforts to bring immunotherapy into its treatment have had minimal success so far. Natural killer cell immunotherapies are promising but have had minimal success so far, offering several strategic angles: monoclonal antibodies targeting tumor-associated antigens, checkpoint approaches, CAR NK cells, other adoptive therapies, and antibody dependent cellular cytotoxicity.

The central idea is to make the tumor easier for natural killer cells to recognize while removing the signals that hold those cells back. Several targets look promising, but the evidence is still mostly preclinical, so patients need research—not promises.