Biomedicine · canada
Stripping Away Colorectal Cancer’s Immune Disguise, the NOTUM Gene Program Emerges as a New Target
A University of Calgary team reports in mouse models that a tumor-intrinsic program driven by NOTUM may allow the most common form of colorectal cancer, and the one least responsive to immunotherapy, to evade attack; this remains preclinical research, but it shifts the focus of drug resistance from immune cells themselves back to how cancer cells hide.
Immunotherapy has reshaped expectations for treating many cancers, but in colorectal cancer, its impact has been uneven. The tumors that clearly benefit are mostly the minority with high microsatellite instability; the more common microsatellite-stable colorectal cancers often seem to remove themselves from the immune system’s field of view. A University of Calgary research team has now published a study in *Cell Reports Medicine* pointing to a gene program that may be involved in this kind of “disappearing act.”
The study was led by Arshad Ayyaz, an assistant professor in the University of Calgary’s Department of Biological Sciences and a member of the Arnie Charbonneau Cancer Institute. Comparing colon cancers that responded to immunotherapy with those that did not, the team found that treatment-resistant tumor cells activate a NOTUM-related, WNT-suppressing tumor-intrinsic program. According to the university, these resistant tumors secrete a protein that makes it harder for the immune system to recognize cancer cells as targets that need to be eliminated.
The key experiment did not directly strengthen immune cells, but instead removed the cancer cells’ cover. After the team used gene editing to knock out the gene encoding that protein, colorectal cancer cells became easier for the immune system to see in mouse models; when combined with immunotherapy, the university news release described complete tumor clearance. Even without adding immunotherapy, tumors shrank, suggesting that this program itself may suppress the effectiveness of the natural immune response.
The clinical significance here lies in the direction of the work, not in an immediately available therapy. Microsatellite-stable colorectal cancer accounts for the majority of clinical cases and has long been a setting where immune checkpoint therapy has struggled to break through. If the NOTUM-related program is indeed a node through which some tumors evade immune surveillance, future drug development may seek not only to make immune cells stronger, but also to make cancer cells lose their ability to hide.
But these results remain at the level of cell and mouse experiments. Mouse tumor models can show mechanism and feasibility, but they are not equivalent to efficacy in humans; gene knockout also does not mean the same pathway can be directly and safely shut down in the clinic. Further studies still need to clarify which patients’ tumors truly depend on the NOTUM program, whether there is a druggable way to intervene, and whether inhibiting this pathway would affect WNT-related physiological functions in normal tissues.
Ayyaz’s team also proposed that similar immune-disguise mechanisms may exist in other solid tumors where immunotherapy has limited effects, such as pancreatic cancer or lung cancer; for now, this is closer to a testable hypothesis than a proven general rule. The study’s most solid contribution is to define the problem of colorectal cancer immune resistance as a traceable and targetable set of tumor-cell programs, leaving a clear entry point for the next stage of translational research.