A single protein may determine whether cancer cell death alerts the immune system

Not all cancer cell deaths are equal. Some cells die quietly, broken apart and swept away without the immune system ever noticing. Others die loudly, releasing molecular distress signals that recruit and activate immune cells against the tumor. This second kind, known as immunogenic cell death (ICD), has become one of the most sought-after mechanisms in cancer therapy. But the molecular switches that determine whether a dying cancer cell triggers an immune response have remained frustratingly unclear.

A team led by Professor Ang Wee Han at the National University of Singapore has now identified one such switch: an enzyme called tyrosine phosphatase 1B (PTP1B). Their study, published January 21, 2026, in the Journal of the American Chemical Society, demonstrates that two platinum-containing compounds directly bind to and inhibit PTP1B, triggering ICD in cancer cells. The discovery opens a new avenue for designing drugs that kill tumors and prime the immune system simultaneously.

Two platinum compounds, one shared target

The researchers had previously developed two platinum-based compounds, Pt-NHC and PlatinER (Pt-ER), that could induce ICD. But the question remained: what were these drugs actually hitting inside the cell?

To find out, the team designed light-activated molecular probes based on Pt-ER. When exposed to light inside cancer cells, these probes tagged every protein the drug physically attached to. Using advanced proteomics and statistical analysis, the researchers winnowed a large pool of candidate targets down to one standout: PTP1B.

Both Pt-ER and Pt-NHC bound directly to PTP1B and blocked its enzymatic activity. The consequence was clear: ICD induction in treated cancer cells. When the researchers tested tumour cells treated with these compounds in a colorectal cancer model, the dying cells effectively vaccinated the system, helping develop protective immunity against subsequent tumor challenge.

Silencing the gene produces the same effect

The platinum compounds were not the only way to flip this switch. When the research team silenced the PTP1B gene entirely, or used other known PTP1B-blocking compounds unrelated to platinum, they observed a similar increase in ICD markers. This convergence of evidence from different experimental approaches strengthened the case that PTP1B itself, rather than some off-target effect of the platinum drugs, was the critical regulator.

Analysis of publicly available cancer datasets further supported this conclusion, indicating that PTP1B expression correlates with tumor growth patterns and immune regulation in colorectal cancer. The enzyme appears to sit at an intersection of cancer cell survival and immune evasion.

Why this matters for combination therapy

Cancer chemoimmunotherapy aims to combine direct tumor killing with immune system activation. The challenge has been finding molecular targets that serve both purposes. PTP1B may be one such target. By inhibiting it, a drug could simultaneously promote cancer cell death in a form that the immune system recognizes and responds to.

PTP1B is not an unknown quantity in drug development. It has been studied extensively as a target for diabetes and obesity treatments, meaning there is already a body of knowledge about its structure, function, and druggability. Several PTP1B inhibitors have entered clinical trials for metabolic diseases. Whether any of these could be repurposed or refined for cancer immunotherapy remains an open question, but the existing pharmacological toolkit provides a head start.

Colorectal cancer models, not patients

The work was conducted entirely in cell lines and mouse models of colorectal cancer. While the vaccination-style experiments, where treated tumor cells protected mice from subsequent tumor challenge, are a well-established method for demonstrating ICD, they do not directly predict clinical outcomes in human patients. The jump from mouse immunology to human cancer treatment is notoriously difficult, and PTP1B inhibition may behave differently across cancer types and in the more complex immune environment of a human body.

The researchers also note that while they have identified PTP1B as a target, the precise structural details of how the platinum compounds interact with the enzyme remain to be worked out. Professor Ang indicated that detailed structural and molecular dynamics studies of PlatinER with PTP1B are the next priority.

The broader search for ICD triggers

The field of immunogenic cell death research has expanded rapidly over the past decade. Several chemotherapy drugs, including certain anthracyclines and oxaliplatin, are known to induce ICD, but the molecular mechanisms vary and are often incompletely understood. What makes this study notable is the identification of a specific, druggable protein target that directly governs whether cell death becomes immunogenic.

Most previous work in the field has focused on the downstream signals of ICD, the calreticulin exposure, ATP release, and HMGB1 secretion that alert immune cells. This study works upstream, identifying a regulatory enzyme whose inhibition promotes the entire cascade. If PTP1B proves to be a generalizable ICD regulator across cancer types, it could inform the design of a new class of chemoimmunotherapy agents.

The collaboration between the NUS team and Associate Professor Maria Babak at the City University of Hong Kong combined expertise in medicinal chemistry and chemical proteomics. The work was supported by the Ministry of Education, Singapore.