Increased basal protein synthesis activity is a hallmark feature that distinguishes many types of malignant cells from their normal counterparts. The survival and proliferation of cancer cells are tightly linked to functional unfolded protein response (UPR) and endoplasmic reticulum (ER)-associated degradation (ERAD) pathways due to their high rates of protein synthesis. The evolutionarily conserved AAA+ ATPase valosin-containing protein (VCP)/p97 facilitates the extraction of proteins from organelles, chromatin, and protein complexes to target them for ubiquitin–proteasome system (UPS)-mediated degradation. p97 plays a key role in protein quality control and in the maintenance of protein homeostasis through its regulation of ERAD. The disruption of p97 activity leads to an accumulation of undegraded proteins, triggers the UPR, and can culminate in proteotoxic cell death. Given this, p97 inhibition offers an opportunity to selectively kill cancer cells that exhibit high basal protein synthesis rates. This review explores p97’s molecular structure, diverse cellular roles, and clinical potential with a particular focus on CB-5083 and CB-5339, the only p97 inhibitors to date that have advanced into clinical trials. We discuss their mechanisms of action, clinical trial outcomes, and the transformative potential of rational combination strategies to maximize their therapeutic potential. By integrating foundational biological insights with translational perspectives, we highlight p97 as a precision target for cancer treatment.

The NADPH oxidase 2 (NOX2) complex is a critical regulator of immune homeostasis. It is utilized by phagocytic leukocytes including neutrophils, monocytes, and macrophages to generate reactive oxygen species (ROS) that drive microbe clearance and modulate inflammatory responses. Within NOX2, the essential scaffold protein p47phox plays a pivotal role in orchestrating enzyme activation and facilitating the assembly and membrane translocation of cytosolic components of the complex. Tight regulation of p47phox activity is crucial, and its disruption is linked to a number of pathological conditions. Conversely, its hyperactivity contributes to oxidative stress, tissue damage, the progression of cardiovascular diseases, neurodegenerative disorders, inflammatory conditions, metabolic syndromes, and cancer. In this review, we detail the structural and functional roles of p47phox, mechanisms of its regulation, and its multifaceted contributions to disease pathogenesis. We explore the latest advances in p47phox-targeted therapeutic strategies, discuss current challenges in the field, highlight p47phox’s potential as a transformative target in redox biology and propose future directions to unlock its clinical utility.

Acute myeloid leukemia (AML) remains defined by therapeutic resistance, adverse genetic heterogeneity, and poor long-term survival, underscoring the need for mechanistically informed regimens that exploit core stress-adaptation liabilities. Polo-like kinase 1 (PLK1) is a central regulator of replication recovery and mitotic progression, yet direct PLK1 inhibitors have been limited by tolerability and incomplete target suppression. Here, we define a clinically actionable strategy that functionally targets PLK1 by combining inhibition of the AAA+ ATPase p97/valosin-containing protein with the hypomethylating agent decitabine (DAC). Using AML cell lines, primary patient specimens, and an orthotopic in vivo model, we show that the clinically relevant p97 inhibitor CB-5339 induces proteotoxic and replication stress, activates the unfolded protein response, and triggers apoptosis. Formal synergy analyses demonstrate that CB-5339 and DAC cooperate across molecular subtypes, including FLT3-ITD+, KMT2A-rearranged, and TP53-mutant AML, to reduce cell viability at pharmacologically relevant concentrations. Transcriptomic, biochemical, and genetic studies identify synergistic suppression of PLK1 as a central consequence of combination treatment, converting stress-dependent PLK1 reliance into a therapeutic vulnerability. Consistent with this mechanism, PLK1 knockdown phenocopies the antileukemic effects of the combination and enhances sensitivity to both agents. In vivo, CB-5339/DAC is well tolerated, significantly prolongs survival, reduces leukemic burden, and suppresses PLK1 in bone marrow blasts. Together, these data establish p97 inhibition as a rational means to exploit replication and proteotoxic stress in AML and provide strong rationale for clinical evaluation of CB-5339 plus DAC in high-risk disease. Significance: This study defines a clinically actionable strategy to overcome therapeutic resistance in AML by functionally suppressing PLK1 through combined p97 inhibition and hypomethylating therapy. By exploiting convergent proteotoxic and replication stress, the regimen produces robust, well-tolerated antileukemic activity across high-risk genetic subtypes, supporting near-term clinical evaluation.

Figure S4. Gene modulation overlap between MOLM-13 and MV4-11 cells.

Figure S2. CB-5339 and DAC synergize to trigger apoptosis.

PLK1 is a key pharmacodynamic target of the CB-5339/DAC combination. A, Targeted PLK1 knockdown impairs AML cell proliferation. MOLM-13 cells were transduced with nontargeted control of PLK1-targeted lentiviral shRNA. Knockdown efficiency was determined by immunoblotting. Cell numbers were quantified for both conditions at 48 hours after lentiviral transduction. N = 3 ± SD; * indicates a significant difference from control shRNA, P < 0.005. B and C, Effects of targeted PLK1 knockdown on sensitivity to CB-5339 and DAC. MOLM-13 cells were infected with lentiviral nontargeted control or PLK1-targeted shRNA. Cells were treated with the indicated concentrations of CB-5339 and DAC. Cell viability was determined by MTT assay. N = 3 ± SD; * indicates a significant difference from control shRNA, P < 0.05. D, High PLK1 expression is associated with resistance to hypomethylating therapy. Within the ELN2022 adverse-risk group, patients with AML were stratified based on PLK1 levels comparing PLK1-low expression (bottom 25%) and PLK1-high expression (top 25%). Hypomethylating therapy response (azacitidine) is shown as an AUC in which higher values indicate greater resistance. Each dot represents an individual patient. Statistical significance was determined using a two-sided Wilcoxon rank-sum test (*, P = 0.05). E, PLK1 is a determinant of sensitivity to the CB-5339/DAC combination. MOLM-13 cells transduced with nontargeted control shRNA or PLK1-targeted shRNA lentiviral vectors were treated with 250 nmol/L CB-5339, 500 nmol/L DAC, or both drugs for 72 hours. The impact of drug treatment on cell viability was determined by MTT assay. N = 3 ± SD; * indicates a significant difference from control shRNA, P < 0.005. F, Overexpression of PLK1 promotes resistance to CB-5339 and DAC. PLK1 was overexpressed in MOLM-13 cells using PLK1-Myc-DDK lentiviral particles. Overexpression efficiency was assessed by immunoblotting. Vector control and PLK1-overexpressing cells were treated with 200 nmol/L CB-5339, 300 nmol/L DAC, and the combination for 72 hours. The effects of drug treatment on cell viability were quantified for each experimental condition by MTT assay. Mean ± SD, n = 3. * indicates a significant difference from vector control cells, P < 0.05.