Necroptosis first came into sharp focus in the late 2000s, when researchers showed that a kinase called RIPK3 could switch tumor necrosis factor signaling away from apoptosis and toward necrosis. The pathway was soon mapped in detail. When caspase-8, the enzyme that normally executes apoptosis, is inhibited, RIPK1 and RIPK3 phosphorylate one another and assemble into an amyloid-like signaling complex sometimes called the necrosome. RIPK3 then phosphorylates MLKL, a pseudokinase that translocates to the plasma membrane and disrupts it, killing the cell. The pathway can be triggered not only by TNF but also by Toll-like receptors, interferons, and the Z-nucleic acid sensor ZBP1, and it plays documented roles in viral defense, inflammatory disease, and neurodegeneration. Because every one of these steps depends on the precise assembly and disassembly of protein complexes, the pathway is exquisitely sensitive to post-translational modifications, and none is more pervasive than ubiquitination.

Ubiquitination is the cell’s universal labeling system. Ubiquitin, a small 76-amino-acid protein, is attached to lysine residues on target proteins through an enzymatic cascade: an E1 activating enzyme hands ubiquitin to an E2 conjugating enzyme, and an E3 ubiquitin ligase performs the final, decisive step of recognizing the substrate and catalyzing transfer. Because E3 ligases choose their substrates, they are the true arbiters of what gets tagged and what does not. The tags themselves come in varieties with very different meanings. A single ubiquitin or a K48-linked chain usually condemns a protein to destruction by the proteasome, whereas K63-linked and linear (M1-linked) chains act as scaffolds that assemble signaling complexes, particularly in the NF-kappaB pathway. E3 ligases fall into structurally distinct families, including the really-interesting-new-gene (RING) ligases that include the large cullin-RING assemblies, the HECT-domain ligases that pass ubiquitin through an intermediate, and the RBR ligases that combine features of both. Many of these enzymes are themselves dysregulated in cancer, which is precisely why their grip on necroptosis matters.

The clearest examples of E3-mediated control center on RIPK1, the gateway kinase of the pathway. The deubiquitinating enzyme CYLD must strip K63-linked chains from RIPK1 within the TNF-induced necrosome before the complex can become a competent necroptosis machine, a finding that established ubiquitin editing as a gatekeeper of programmed necrosis. On the writing side, the E3 ligase PELI1 (Pellino1) ubiquitinates RIPK1 and acts as a dual modulator, influencing both necroptosis and apoptosis while also controlling levels of the anti-apoptotic protein c-FLIP. TRAF6, another RING-type ligase best known for its immune signaling roles, regulates the abundance of RIPK1 and suppresses the RIPK1-RIPK3-MLKL cascade, and studies cited in the review show that this affects colorectal cancer progression. A20, a ligase-deubiquitinase hybrid that restrains NF-kappaB signaling, has been shown to suppress spontaneous necroptosis in acute myeloid leukemia, and that suppression mediates chemotherapy resistance, a striking example of ubiquitin control determining treatment outcome.

RIPK3 and MLKL, the downstream executors, are equally entangled in ubiquitin biology. TRIM25, a member of the tripartite-motif ligase family, ubiquitinates RIPK3 and thereby inhibits TNF-induced necrosis, positioning it as a potential tumor-sensitizing target. The U-box ligase CHIP controls necroptosis through ubiquitylation-dependent, lysosome-mediated degradation of RIPK3, and clinical data from non-small cell lung cancer suggest that CHIP and RIPK3 levels carry prognostic weight. More recently, opposing regulation of K63-linked polyubiquitination of RIPK3 by the ligase SMURF1 and the deubiquitinase USP5 has been shown to tune the pathway, while the cullin-RING substrate adaptor SPOP mediates ubiquitination of both RIPK1 and RIPK3, promoting apoptosis and protecting against necroptosis. Even MLKL itself is tagged: site-specific ubiquitination redirects it to endosomes, a modification that in infected cells helps route intracellular bacteria such as Listeria and Yersinia to lysosomes. The AMPK-Parkin axis adds another layer, with the Parkin ligase helping to inhibit the necrosome and thereby restraining both necroptosis and tumorigenesis.

The inhibitor-of-apoptosis (IAP) proteins occupy a special place in this story because they are both E3 ubiquitin ligases and established drug targets. cIAP1, cIAP2, and XIAP ubiquitinate components of TNF receptor signaling and keep necroptotic complexes in check. Pellino-1 has been shown to confer chemoresistance in lung cancer cells by upregulating cIAP2 through K63-linked polyubiquitination, and the TRIP-Br1 oncoprotein stabilizes XIAP to inhibit apoptosis, autophagy, and necroptosis under nutrient-deprived conditions, helping tumor cells survive starvation. The therapeutic payoff is already visible: SMAC mimetics, drugs that degrade IAPs, are in clinical development for cancer, with agents such as xevinapant being tested with radiation in head and neck cancer and tolinapant (ASTX660) evaluated in colorectal cancer. By removing the ubiquitin-ligase brake on death receptor signaling, these compounds can sensitize tumors to TNF-alpha, TRAIL, and radiotherapy, in part by liberating the necroptosis machinery.

What makes the review by Wei and Sun timely is its insistence that E3 ligase control of necroptosis is not a laboratory curiosity but a determinant of cancer behavior in both directions. Necroptosis can suppress tumors by killing malignant cells and, through the release of antigens and the involvement of RIPK1-dependent signaling in dying cells, by priming CD8-positive T cell responses, raising interest in engineering necroptotic tumor cell vaccines for immunotherapy. Yet it can also promote cancer. Tumor cells can induce necroptosis in endothelial cells through death receptor 6, opening gaps in the vasculature that facilitate metastasis, and in pancreatic cancer, necroptosis has been shown to enhance so-called don’t-eat-me signals and induce macrophage extracellular traps that promote liver metastasis. Chronic necroptotic inflammation can also feed tumor-promoting microenvironments. Which way the balance tips depends heavily on the ubiquitin-editing enzymes that decide when and where the pathway fires.

This duality explains why the E3 ligases themselves are attractive drug targets, and why targeting them is technically demanding. Cullin-RING ligases, HECT ligases, and RBR ligases have all yielded small-molecule modulators in drug discovery programs, and the success of molecular glue degraders and PROTAC degraders, which hijack E3 ligases to destroy disease proteins, has energized the field. In principle, one could inhibit a ligase such as TRAF6 or TRIM25 to unleash necroptosis in a tumor that has locked the pathway down, or boost a protective ligase to suppress the inflammatory necroptosis that fuels metastasis. The complication is context: the same enzyme can protect in one tissue and promote disease in another, and E3 ligases typically have dozens of substrates beyond the necroptosis machinery, raising the specter of on-target toxicity in normal tissues that rely on these enzymes for immune homeostasis.

Wei and Sun argue that the next phase of the field will require mapping which E3 ligases act on which necroptosis substrates in which tumor types, and identifying biomarkers, such as CHIP, RIPK3, or BIRC3 expression, that predict whether a patient’s tumor is primed for necroptotic death or defended against it. The convergence of ubiquitin biology and cell death research is producing a picture in which cancer is not simply a matter of genes gone bad, but of molecular tags gone wrong. If the ubiquitin code of necroptosis can be read and rewritten with the same precision now being applied to protein degradation, the explosive form of cell death may finally become a controllable weapon against cancer, rather than the unpredictable force it has so often appeared to be.

Subject of Research: Regulation of necroptotic cell death by E3 ubiquitin ligases and its implications for cancer therapy

Article Title: E3 ubiquitin ligase-mediated necroptosis: regulatory mechanisms and therapeutic implication in cancer

Article References: Wei, M., & Sun, A. (2026). E3 ubiquitin ligase-mediated necroptosis: regulatory mechanisms and therapeutic implication in cancer. Molecular Biology Reports, 53(1), Article 1698. https://doi.org/10.1007/s11033-026-12900-w

Image Credits: AI Generated

DOI: 10.1007/s11033-026-12900-w

Keywords: necroptosis, E3 ubiquitin ligases, ubiquitination, RIPK1, RIPK3, MLKL, cancer therapy, IAP antagonists, TRIM25, TRAF6, inflammation, tumor microenvironment