Peroxisomal Lipid Metabolism as a Therapeutic Target in Leukemia

ABSTRACT

Lipid delivery and metabolism profoundly shape cancer cell fate, energy balance, redox control, and therapy resistance. Peroxisomes regulate fatty acid oxidation (FAO) and oxidative homeostasis with growing relevance in hematologic malignancies. Recent studies show peroxisomal FAO (pFAO) is selectively elevated in acute myeloid leukemia (AML) and chronic lymphocytic leukemia (CLL), sustaining cancer cell survival under metabolic and therapeutic stress. Elevated ACOX1, ABCD1/2, CROT, and PEX5 expression underscores leukemia‐specific peroxisomal vulnerability; their pharmacologic or genetic inhibition disrupts lipid homeostasis, induces very‐long‐chain fatty acid accumulation, and drives oxidative stress and lipotoxicity. This selectively kills leukemia cells while sparing normal progenitors. pFAO blockade synergizes with chemotherapy drugs such as venetoclax and cytarabine, enabling exploitation of metabolic vulnerabilities to improve therapeutic outcomes. Upstream, PPAR isoforms transcriptionally link lipid ligand sensing to peroxisomal gene expression, though their precise role in governing pFAO in leukemia remains undefined. Integrating solid tumor and leukemia insights, peroxisomes emerge as dynamic lipid‐processing organelles coupling FAO, redox buffering, and inter‐organelle exchange to cancer persistence. Targeting peroxisome‐mediated lipid delivery offers a frontier for overcoming metabolic resilience and therapeutic resistance in leukemia.

Peroxisomes are emerging as key regulators of lipid metabolism in leukemia. Enhanced metabolism of very‐long‐chain fatty acids (VLCFAs) supports leukemia cell survival, redox homeostasis, and therapeutic resistance. Pharmacologic disruption of peroxisomal fatty acid oxidation causes VLCFA accumulation, oxidative stress, and mitochondrial dysfunction that selectively eliminate leukemia cells while sparing normal cells. Targeting peroxisome‐mediated lipid processing represents a promising strategy to overcome metabolic resilience in blood cancers.

1. Introduction

Lipid metabolism is a critical regulator of cancer initiation and progression. Fatty acid oxidation (FAO) is upregulated across diverse malignancies, conferring chemotherapy resistance and enabling disease relapse. In normal cells, FAO catabolizes fatty acids to produce TCA‐bound acetyl‐CoA, fueling ATP production. In cancer cells, this pathway undergoes metabolic rewiring to support anabolic and cell growth activities. Thus, this FAO elevation in cancer relative to normal cells offers a therapeutic strategy to target fatty acid uptake and metabolism. Mitochondria and peroxisomes both execute FAO, with fatty acid chain length and saturation dictating the site of catabolism. While mitochondria have been the focus of drug‐targeting efforts, inhibition of peroxisomal FAO (pFAO) is emerging as a novel and promising anti‐cancer approach [1, 2, 3, 4].

Fatty acids fuel cancer cell proliferation and survival by generating ATP, NADH/FADH₂ and NADPH, modulating cell signaling (e.g., via peroxisome proliferator‐activated receptors (PPAR), CD36/FABP4), and promoting therapy resistance [5, 6]. They maintain membrane structures, serve as key energy substrates, support redox homeostasis under stress, and influence the bone marrow niche through adipocyte interactions and lipolysis [7, 8]. Peroxisomes function as metabolic hubs central to lipid processing, including β‐oxidation of very‐long‐chain fatty acids (VLCFAs) and α‐oxidation of branched‐chain or polyunsaturated fatty acids, alongside ether phospholipid and bile acid synthesis. They also regulate reactive oxygen species (ROS) homeostasis via catalase [9] and contribute to signaling through PPAR activation by lipid ligands [10].

In leukemia, including acute myeloid leukemia (AML) and chronic lymphocytic leukemia (CLL), pFAO supports cancer cell proliferation and survival under stress via elevated acyl‐CoA oxidase (ACOX) 1, carnitine O‐octanoyltransferase (CROT), ATP‐binding cassette subfamily D (ABCD) 1, and ABCD2 expression and activity [11, 12]. Additionally, disruption of peroxisomal PPAR‐mediated FAO impairs lipid metabolism [10], potentiating responses to inhibitors in AML models [13]. Together, peroxisomes as emerging therapeutic vulnerabilities in leukemia lipid dependency. Below, the current literature on the role of peroxisomal lipid metabolism in human leukemias is reviewed. We discuss how disrupting peroxisomal function has anti‐leukemia properties and the implications of these findings for chemotherapy.

2. Cancer Metabolism: Fatty Acid Oxidation (FAO)

FAO is the catabolic process by which fatty acids are sequentially broken down (two carbons per cycle) via β‐oxidation to generate acetyl‐CoA, NADH, and FADH₂. These products fuel the tricarboxylic acid (TCA) cycle and oxidative phosphorylation (OXPHOS) for ATP production. In fact, FAO generates 2.5 times more ATP per mole of substrate than glycolysis (106 ATP from palmitate vs. 36 ATP from glucose), offering superior thermodynamic efficiency through complete β‐oxidation of acyl‐CoAs, with acetyl‐CoA feeding tricarboxylic acid (TCA) cycle and OXPHOS [14]. Therefore, under normal physiological conditions, FAO primarily serves as a source of ATP production, especially in energy‐demanding tissues like the heart, skeletal muscles, and liver.

In cancer cells, FAO is repurposed to support anabolic processes and survival under metabolic stress [15]. While ATP production is still important in certain conditions (e.g., hypoxia), FAO in cancer cells is often utilized to generate metabolic intermediates like acetyl‐CoA and NADPH, which are essential for biosynthesis and redox balance. FAO is upregulated across diverse malignancies, conferring chemotherapy resistance and fostering disease relapse. Given its selective elevation in malignant cells relative to normal counterparts, therapeutic strategies targeting lipid uptake and metabolism have been pursued [8].

FAO inhibition triggers selective leukemia cell death, while hematopoietic stem cells (HSCs) are spared due to their metabolic flexibility, primarily quiescence, low OXPHOS demand, and rapid glycolysis compensation without FAO reliance [16]. FAO inhibition using etomoxir, a carnitine palmitoyltransferase 1A (CPT1A) inhibitor, results in ATP depletion and decreased antioxidant capabilities, increasing ROS levels and mitochondria‐mediated apoptosis and cell death [16, 17, 18]. These findings are based on preclinical models, and no FAO inhibitors have entered clinical trials due to severe hepatotoxicity associated with etomoxir, along with its detrimental effects on mitochondrial function in healthy cells. Unlike etomoxir, very long‐chain acyl‐CoA dehydrogenase (VLCAD) inhibition with avocadyne, a 17‐carbon fatty alcohol derived from avocado, selectively targets mitochondrial FAO in relapse‐initiating leukemia stem cells, demonstrates excellent in vivo tolerability, and spares normal hematopoietic cell function [17, 18]; avocadyne represents a new class of anti‐AMLcompounds.

In normal hematopoietic cells, FAO supports basal energy demands, redox balance, and differentiation, but it is not the dominant bioenergetic pathway under steady‐state conditions. HSCs and progenitors flexibly switch between glycolysis and FAO, using FAO‐derived acetyl‐CoA to fuel the TCA cycle and OXPHOS during stress or increased proliferative demand, while maintaining low ROS levels through tightly coupled mitochondrial and peroxisomal antioxidant systems [19]. By contrast, AML cells are metabolically rewired to rely disproportionately on FAO to sustain high OXPHOS, regenerate NADPH for redox homeostasis, and support leukemia stem cell maintenance and chemoresistance [16]. This shift transforms FAO from a facultative, supportive pathway in normal hematopoiesis into an obligate survival mechanism in AML, creating a therapeutic window in which FAO inhibition is selectively cytotoxic to leukemic cells yet largely tolerated by metabolically flexible normal HSCs.

3. Peroxisomes: Metabolic Hubs With Unique Substrate Specificity

FAO takes place in mitochondria and peroxisomes. Multiple reviews discuss the role of mitochondrial FAO in leukemia [8, 20, 21], but none highlight the role of peroxisomes in this pathway. Peroxisomes are single‐membrane‐bound organelles with a granular matrix. They contain over 60 known oxidative enzymes, transporters, and biogenesis factors [22] and function to catabolize VLCFAs and branched‐chain fatty acids, synthesize ether lipids (i.e., plasmalogens) and bile acids, and are the site of catalase‐mediated ROS detoxification. Before entering peroxisomes, fatty acids are activated (i.e., in the cytosol or ER) by very long‐chain acyl‐CoA synthetases (ACSVL/FATP family members) [23]. ABCD transporters import fatty acyl‐CoAs into the peroxisomal lumen where they are broken down by rate‐limiting ACOX enzymes [24, 25, 26, 27]. The shortened‐chain products, such as hexanoylcarnitine (C6), are almost exclusively generated by pFAO and exported as carnitine esters by carnitine acyltransferases (i.e., CROT and CRAT), and transported to mitochondria via carnitine‐acylcarnitine translocase (CACT) to further fuel FAO, TCA cycle, OXPHOS and ATP production [9]. Alternatively, these carnitine esters are diverted to lipid biosynthesis as needed [28]. These peroxisomal pathways are illustrated in Figure 1.

FIGURE 1.

Overview of peroxisomal fatty acid β‐oxidation and VLCFA metabolism. Schematic illustrating the major pathways of very long‐chain fatty acid (VLCFA) metabolism within the peroxisome. Activation of VLCFA by acyl‐CoA synthetases (e.g., FATP2/4) produces VLCFA‐CoA, which is imported via ABCD1/2 into the peroxisomal matrix for successive rounds of β‐oxidation. The process involves: (1) dehydrogenation by acyl‐CoA oxidase (ACOX1/3) generates H₂O₂ and trans‐2‐enoyl‐CoA; (2,3) hydrolysis and second dehydrogenation by D‐bifunctional protein (HSD17B4); and (4) thiolysis by 3‐ketoacyl‐CoA thiolase (ACAA1) yieldis acetyl‐CoA and shortened acyl‐CoA, which re‐enters the cycle or exits via carnitine O‐octanoyltransferase (CROT) for mitochondrial β‐oxidation. Acetyl‐CoA exits via carnitine acetyltransferase and is directed to mitochondrial TCA cycle. Branched‐chain pristanic acid and bile acid intermediates are imported via ABCD3 to undergo α‐oxidation followed by β‐oxidation. Catalase detoxifies H₂O₂ in the antioxidant pathway, as well as acyl‐CoA binding domain containing 5 (ACBD5) enabling bidirectional H₂O₂ shuttling for enhanced ROS buffering efficiency.

Peroxisomes form through de novo biogenesis from ER‐derived vesicles or fission of preexisting organelles [29]. De novo assembly involves peroxin (PEX) proteins, such as PEX3, PEX14, and PEX16 for membrane formation and peroxisomal membrane protein (PMP) insertion including ABCD transporters [30, 31]. Peroxisomal fission relies on PEX11β, DRP1, FIS1, and MFF, some of which are shared with mitochondrial fission [32]. Matrix enzymes like ACOX1 and catalase are imported into the peroxisomal matrix via PEX5 [33, 34, 35]. Peroxisomes form membrane contact sites with other organelles like mitochondria via PTPIP51 and ACBD5 (mitochondrial and peroxisomal tether, respectively) enabling bidirectional H₂O₂ shuttling for enhanced ROS buffering efficiency [9]. A summary of peroxisomal genes and their primary function can be found in Table 1.

TABLE 1.

Peroxisomal genes and their primary function.

Gene/Protein groups	Examples	Primary functions	Role in peroxisome biogenesis/metabolism
PEX biogenesis (matrix import)	PEX1, PEX2, PEX5, PEX6, PEX7, PEX10, PEX12, PEX13, PEX14, and PEX26	PTS1/PTS2 receptors, AAA ATPases, ubiquitin ligases, and docking factors	Import peroxisomal matrix proteins via PTS1/PTS2 signals
PEX biogenesis (membrane assembly/fission)	PEX3, PEX11β, PEX16, and PEX19	Membrane anchors, fission factors, and chaperones	Peroxisome membrane formation, division, and protein targeting
Fatty acid transporters/Activators	ABCD1, ABCD2, ABCD3 (PMP70), and FATP2 (SLC27A2)	ATP‐binding cassette transporters; long‐chain fatty acid transport proteins	VLCFA/LCFA import and activation for peroxisomal β‐oxidation
Acyl‐CoA oxidases	ACOX1, ACOX2, and ACOX3	Flavin‐dependent oxidases	Initial dehydrogenation of Straight‐, branched‐, or short‐chain fatty acids
β‐Oxidation enzymes	HSD17B4 (D‐bifunctional), DECR2, and SCPx (thiolase)	Hydratase, dehydrogenase, reductase, and thiolase	Complete VLCFA β‐oxidation chain shortening
ROS detoxification	CAT (catalase)	H2O2‐decomposing peroxidase	Neutralizes peroxisome‐generated hydrogen peroxide
Ether lipid/Plasmalogen synthesis	AGPS, FAR1, and GNPAT	Initiates ether phospholipid biosynthesis	Contributes to plasmalogen‐mediated ROS buffering and membrane remodeling

Peroxisomes are involved in plasmalogen production by initiating ether phospholipid biosynthesis through enzymes like alkylglycerophosphate synthase (AGPS), fatty acyl‐CoA reductase 1 (FAR1), and glyceronephosphate O‐acyltransferase (GNPAT). These vinyl‐ether lipids comprise ∼20% of human phospholipids and are enriched in brain (20%–50%), heart (32%–50%), and immune cells [36]. Plasmalogens stabilize lipid rafts, which are the nanoscale, cholesterol‐ and sphingolipid‐enriched microdomains that form ordered platforms in the plasma membrane for signaling and protein sorting. These domains facilitate essential processes like membrane fusion and ion transport. Plasmalogens serve as endogenous antioxidants: the sn‐1 vinyl‐ether bond scavenges peroxyl radicals and singlet oxygen, terminating lipid peroxidation and shielding polyunsaturated fatty acids at sn‐2 (e.g., arachidonic acid; DHA). Aside from maintaining membrane integrity and acting as antioxidants in normal physiology, plasmalogens are also critical for the function of cancer cells [37, 38]. These lipids, enriched in lymphoma and solid tumors, confer ROS resistance and metastatic potential independent of pFAO, expanding the role of peroxisomes beyond FAO to include membrane remodeling and therapy resistance. The role of plasmalogens is thoroughly reviewed elsewhere [37].

Emerging evidence shows that AML and CLL cells upregulate ABCD1/2 expression compared to normal hematopoietic cells, highlighting an increased reliance on VLCFA metabolism [11, 12]. CLL cells also upregulate ACOX1 and CROT, whereas AML cells overexpress ABCD1, catalase, and PEX5 [11]. Together, these peroxisomal adaptations position pFAO as a leukemia‐specific metabolic dependency that could be exploited therapeutically.

4. Role of Peroxisomes in Dietary Lipid Processing

Peroxisomes play a specialized role in the metabolism of dietary fatty acids that cannot be efficiently processed by mitochondria, particularly VLCFAs, branched‐chain fatty acids (e.g., phytanic and pristanic acids), and monomethyl branched‐chain fatty acids derived from dietary sources [22]. VLCFAs originate from fish oils rich in ω‐3 polyunsaturated fatty acids (PUFAs) such as DHA and eicosapentaenoic (EPA) acid, while branched‐chain fatty acids arise from chlorophyll degradation products in green vegetables and ruminant fats (dairy, beef). These lipids are imported via ABCD1/2/3 transporters and broken down by pFAO. This pathway accounts for approximately 20% of total dietary fatty acid catabolism and is critical for preventing toxic lipid accumulation in non‐adipose tissues.

The importance of peroxisomes in VLCFA breakdown is illustrated in X‐linked adrenoleukodystrophy (X‐ALD) patients with ABCD1 mutations impairing VLCFA import causing their accumulation in plasma, tissues, fibroblasts, and complex lipids like cholesterol esters, phosphatidylcholine, and myelin gangliosides [39]. This manifests pathologically as myelin destabilization (membrane rupture in oligodendrocytes), oxidative stress (VLCFA‐induced ROS/GSH depletion), neuroinflammation (microglial activation), and adrenal atrophy. In X‐ALD patients, dietary management includes strict VLCFA restriction (<3 mg/day C26:0 intake vs. 12–40 mg/day in typical Western diets), avoiding high‐VLCFA foods like whole‐fat dairy, coconut/palm oils, and chocolate while prioritizing low‐fat alternatives. This approach, often combined with Lorenzo's O which inhibits de novo synthesis of VLCFAs, normalizes plasma VLCFA levels biochemically but requires careful monitoring to prevent malnutrition and essential fatty acid deficiencies [40].

Under normal physiological conditions, dietary induction of pFAO is mediated by PPARα/δ, which respond to high intakes of ω‐3‐rich fish oils, branched‐chain amino acid‐containing proteins, or ruminant lipids by upregulating key enzymes (ACOX1/2, DECR2) and catalase for H₂O₂ detoxification. Functional foods delivering these lipids, such as salmon, whey protein isolates, or jojoba oil, directly engage peroxisomal processing [41]. In the context of lipid delivery, selective pFAO modulators like eicosenol (from plant wax esters) exploit cancer‐specific vulnerabilities, as FAO‐addicted leukemia cells are eliminated due to VLCFA overload and lipotoxicity, whereas normal cells maintain metabolic flexibility [11]. This positions peroxisomal metabolism as a novel target for precision nutrition strategies in oncology and metabolic disease prevention.

5. Peroxisome–Mitochondria Crosstalk

Mitochondria and peroxisomes coordinate cellular FAO and share key enzymes and co‐factors [42]. Peroxisomes consume up to 20% of cellular oxygen under basal conditions. Unlike mitochondrial respiration, peroxisomal activity yields no ATP and instead dissipates energy as heat, though its acetyl‐CoA and medium‐chain fatty acid (MCFA) products indirectly support mitochondrial ATP synthesis [43].

The functionality of the two organelles is complementary to their unique roles in lipid metabolism. Mitochondrial FAO (mFAO) is the primary pathway for catabolism of saturated fatty acids below 18 carbons in length, while peroxisomes process lipids exceeding 20 carbons [29] and unsaturated fatty acids with 18 carbons [25]. Mitochondria are equipped with a series of enzymes that catabolize medium and long‐chain fatty acids (LCFA) through a four‐step β‐oxidation process. For example, Tcheng et al. identified VLCAD as an upregulated mFAO enzyme in AML patients [17]. VLCAD is responsible for catalyzing the first of four steps of the intramitochondrial long‐chain FAO pathway, and its genetic and pharmacological inhibition with avocadyne leads to selective AML cell death and reduced AML engraftment in vivo [17].

Beta‐oxidation of VLCFA in peroxisomes is similar to that in mitochondria except for the initial dehydrogenation step [22]. In peroxisomes, the reaction is catalyzed by FAD‐linked ACOX, an enzyme that transfers two hydrogens from the CoA‐thioester substrate to reduce O₂ into H₂O₂. Next, the fatty acyl‐CoA is broken down by peroxisomes using an NAD⁺‐dependent reaction where peroxisomes produce MCFAs (mainly C6) that are transported to mitochondria for further degradation by mFAO enzymes. In addition, pFAO produces a two‐carbon lipid acetyl‐CoA that is also utilized by mitochondria to fuel the TCA cycle. The direct byproduct of mFAO is acetyl‐CoA, which enters the TCA cycle. The TCA‐produced coenzymes NADH and FADH₂ are bound for OXPHOS. Interestingly, pFAO also contributes to the pool of NADH and FADH₂ redox cofactors, which can be transferred to mitochondria through a redox shuttle [44]. Finally, peroxisomes form membrane contact sites with mitochondria via protein tyrosine phosphatase‐interacting protein 51 (PTPIP51) and acyl‐CoA binding domain containing 5 (ACBD5) (mitochondrial and peroxisomal tether, respectively) enabling bidirectional H₂O₂ shuttling for enhanced ROS buffering efficiency [9].

6. Evidence of pFAO Dependency in Leukemia

In CLL cells, ACOX1, CROT, and ABCD2 are upregulated (independent of karyotype complexity) relative to normal B cells. Serum levels of short‐chain acylcarnitines (C2 and C6) are elevated in CLL patients compared to healthy donors [45] underscoring the critical role of pFAO in sustaining CLL metabolism and progression. Partial genetic ACOX1 knockdown shifts metabolism toward a carbon‐based (glucose) and amino acid (glutamine) phenotype with C2‐C6 acylcarnitine reduction (indicating pFAO suppression). This “glutamine phenotype” reflects heightened reliance on glutamine metabolism for ATP generation and biosynthesis via glutaminolysis (glutamine conversion to glutamate, then α‐ketoglutarate to fuel the TCA cycle and OXPHOS) while preserving cell viability. Increased glucose uptake compensates alongside glutamine, enabling survival despite pFAO impairment. This compensatory mechanism is eliminated with complete pharmacological inhibition of ACOX1 using 10,12‐tricosadiynoic acid (TDYA). Acute pharmacological ACOX1 inhibition reduces H₂O₂ by 30% indicating a modest effect on pFAO flux. Notably, pFAO inhibition elicits a significant linear reduction in cellular ATP levels in CLL cells while sparing healthy B‐lymphocytes that predominantly utilize glucose metabolism [12]; this ATP depletion is consistently observed across primary CLL samples, demonstrating that a substantial fraction of ATP production is pFAO‐dependent.

In AML cells, there is an even greater ATP reduction (i.e., >40%) when cells are treated with the ABCD1 inhibitor, eicosenol; normal peripheral blood mononuclear cells (PBMCs) show no change, as they upregulate glycolysis for sustained ATP production [11]. AML cells upregulate ABCD1 relative to HSCs, driving elevated VLCFA pFAO. Genetic or small‐molecule ABCD1 inhibition causes unprocessed VLCFA accumulation alongside essential MCFA/LCFA depletion. AML cells, unlike PBMCs, maintain consistent glucose uptake during pFAO inhibition; they exhibit specific metabolic changes, including lower basal and maximal respiration rates and reduced spare reserve capacity (SRC). Interestingly, TDYA showed limited anti‐AML activity, suggesting leukemia subtype‐specific pFAO targets: ACOX1 vulnerability in CLL versus ABCD1 dependence in AML [11, 12].

7. Mechanisms of pFAO Inhibition‐Induced Leukemia Cell Death

In preclinical models, disrupting peroxisomal function alters lipid homeostasis, causing rapid lipid peroxidation and systemic lipotoxicity. This metabolic stress disrupts cellular redox balance, selectively killing leukemia cells while sparing healthy cells. Lipotoxicity arises from the buildup of toxic lipid species (e.g., VLCFAs, diacylglycerols, and ceramides) in non‐adipose tissues, driving cellular dysfunction and death through ER stress, oxidative damage from lipid peroxidation, organelle dysfunction, and inflammatory pathways [46, 47, 48, 49].

Lipid peroxidation is a chain reaction where ROS initiate oxidative breakdown of PUFAs in cell membranes, amplifying cellular damage. In AML, pFAO inhibition causes VLCFA buildup, depletes MCFA/LCFA, and dysregulates lipid droplets (storage organelles), together triggering selective lipid peroxidation and lipotoxicity in leukemia cells [11].

Mechanistic evidence links ABCD1 inhibition, and subsequent block in pFAO in AML, to cytotoxic VLCFA overload and elevated ratios of oxidized phosphatidylserine OxPS(18:0_20:4(10)) versus reduced phosphatidylserine PS(18:0_20:4). Elevated OxPS(18:0_20:4(10)):PS(18:0_20:4) ratios signify selective peroxidation of arachidonoyl‐phosphatidylserine driven by ROS, which shifts the balance in reduced versus oxidized PS accumulating peroxidized products. The C11‐BODIPY 581/591 probe confirms increased peroxidation induced by eicosenol treatment in AML cells. In contrast, normal cells resist uncontrolled lipid peroxidation during pFAO inhibition due to absent adaptive redox homeostasis in AML cells. Healthy cells are equipped with robust peroxisomal antioxidant defenses, such as catalase and plasmalogens that quench ROS to prevent peroxidation, preserving membrane integrity and escaping cell death.

Peroxidized lipids and lipotoxic stress activate NADPH oxidases, further fueling ROS production and disrupting mitochondrial redox balance [50]. Peroxisomes play a critical role in mitigating this by maintaining interorganellar homeostasis. Defects within peroxisomes are well‐documented to impair mitochondrial function [51, 52], with oxidative stress emerging as a hallmark of peroxisomal biogenesis disorders. Mitochondrial dysfunction often accompanies loss of catalase expression, activity, or peroxisomal targeting [53, 54, 55]. A recent study highlights ROS transfer from mitochondria to the peroxisomal lumen via ACBD5‐PTPIP51 contacts, the number of which increases under mitochondrial oxidative stress ultimately enabling peroxisomes to absorb excess ROS [9]. Unlike the NADPH‐consuming glutathione system, peroxisomal H₂O₂ reduction by catalase is NADPH‐independent; this renders peroxisomes resilient during metabolic strain, effectively preventing propagation of lipid peroxidation in lipotoxic contexts.

In leukemias like AML and CLL, pharmacologic inhibition of ABCD1 or ACOX1 impairs this peroxisomal ROS sink, preventing absorption of excess mitochondrial ROS and driving oxidative stress as a shared mechanism of cell death [11, 12]. In CLL, peroxisomal targeting with TDYA not only elevates mitochondrial ROS but also converges on apoptotic pathways, activating BAX/BAK‐dependent mitochondrial outer membrane permeabilization and cytochrome C release. This triggers caspase‐9 and ‐3 cascades leading to apoptosis, in contrast to AML's lipotoxic cell death driven by unchecked peroxidation. Figure 2 illustrates the differential response of leukemia and normal cells to pFAO inhibition, and available peroxisomal inhibitors and their targets are summarized in Table 2.

FIGURE 2.

Overview of peroxisomal fatty acid β‐oxidation (pFAO) in cancer and normal cells. Schematic summarizing differences in pFAO inhibition via ABCD1 and ACOX1 targeting in leukemia and normal cells.

TABLE 2.

Peroxisomal targets in leukemia and cancer with available inhibitors.

Enzymes/Transporters	Evidence in leukemia (cancer)	Compounds	Mechanisms of action	Efficacy/Study stages
ABCD1	Upregulated in AML; VLCFA accumulation drives lipotoxicity in AML [11]	Eicosenol [11]	Inhibits VLCFA transport, causing lipid peroxidation [11]	Synergistic with AraC/venetoclax/avocadyne; preclinical [11]
ACOX1	Upregulated in CLL (HER2+ breast cancer, lymphoma) [12]	TDYA [12]	Blocks acyl‐CoA oxidase, elevates ROS [12]	Additive with fludarabine; synergistic with BTK inhibitors; preclinical [12]
DECR2	Promotes resistance (in CRPC); lipid metabolism regulator [1]	Thioridazine	Inhibits pFAO, suppresses growth [1]	Reduces proliferation and migration; preclinical [1]

8. Therapeutic Synergies of pFAO Inhibition

The bulk of studies exploring pFAO and carcinogenesis involve solid tumors, where pFAO contributes to chemotherapy resistance. For instance, pFAO sustains metabolism in “persistent” melanoma cells [4], whereas DECR2, a peroxisomal enzyme that reduces (2E,4E)‐dienoyl‐CoA intermediates to (3E)‐enoyl‐CoA in the β‐oxidation pathway of unsaturated fatty acids, promotes treatment resistance in advanced prostate cancer; depletion of DECR2 suppresses proliferation, migration, and tumor growth in vitro and in vivo [1]. Loss of ACOX1 is prominent in human peroxisomal disorders [29] and is upregulated in HER‐2 positive breast cancer, where it positively correlates with worse overall patient survival [56]. In lymphoma models, ACOX1 drives proliferation and blunts responsiveness to doxorubicin; meanwhile, the HDAC inhibitor vorinostat elevates peroxisome numbers and proteins (PEX3, PEX11b, and PMP70) [3]. PEX3 knockdown sensitizes cells to vorinostat‐induced ROS apoptosis, highlighting peroxisomes as a protective rheostat, with resistant lymphoma cells upregulating catalase and plasmalogens to buffer excess ROS.

In AML, patient cells resistant to venetoclax/azacitidine (Ven/Aza) therapy have upregulated pFAO gene signatures (alongside mitochondrial FAO) [5]. Another study revealed that cytarabine (AraC) resistant AML cells in PDX models exhibit high OXPHOS and elevated FAO (including a dysregulated pFAO signature contained in supplementary transcriptomics data) driving chemoresistance [6]. Both studies showed that targeting FAO with etomoxir, a molecule that inhibits mitochondrial fatty acid import, shifts metabolism to sensitize resistant cells to Ven/Aza and AraC. However, neither of these studies pursued functional validation of pFAO inhibition. Nonetheless, recent work on CLL and AML is beginning to fill this gap, demonstrating that pFAO blockade heightens sensitivity to chemotherapy agents like Ven and AraC [11], laying groundwork for peroxisome‐targeted combinations.

Inhibiting mFAO or pFAO selectively kills leukemia cells, but the effects of combined inhibition remain underexplored, particularly as post‐induction therapy survivors upregulate both mFAO and pFAO signatures, rendering them more sensitive to FAO blockade [5, 6]. AML cells with reduced mFAO, achieved via mitochondrial VLCAD knockdown, upregulate pFAO as an adaptive rewiring; these cells are hypersensitive to pFAO inhibition (manuscript under revision). Combining eicosenol (ABCD1/pFAO inhibitor) with avocadyne (VLCAD/mFAO inhibitor) synergistically reduces viability in AML cells, inhibits colony formation of patient‐derived AML cells, and spares normal PBMCs, exploiting AML's metabolic vulnerability by comprehensively inhibiting the entire cellular FAO.

9. Eicosenol: Novel Peroxisomal Inhibitor

Plant wax esters are a concentrated source of VLCFA esterified to alcohols that release during digestion [57, 58, 59]. These hydrolyzed compounds are absorbed by endothelial gastrointestinal cells reaching the systemic circulation and organs, where they exert biological activity [60, 61]. The chain length of wax ester‐derived fatty molecules varies from 18 to 36 carbons [57], which makes them ideal candidates for peroxisomal processing. Most wax esters are from agricultural waste since they are found in plant leaves and stems [62], of which several contain policosanols, classified as nutraceuticals, due to health benefits including an antioxidant effect and reducing low‐density lipoprotein [63, 64]. Additionally, plant‐derived waxes are part of a whole food diet and extensively used in cosmetics with established long‐term safety [65]. Overall, there is substantial evidence that these compounds are safe with several reported health benefits, and given their role in peroxisomal biology, they offer enticing potential for cancer metabolic therapy.

Eicosenol (C20:1, specifically (Z)‐11‐eicosen‐1‐ol) is a monounsaturated fatty alcohol derived from the reduction of 11‐eicosenoic acid (gondoic acid, cis‐20:1n‐9), a dietary lipid abundant in several edible sources. Eicosenol serves as a selective inhibitor of the peroxisomal ABCD1 transporter, blocking the entry and β‐oxidation of VLCFAs; thereby reducing pFAO and leading to VLCFA accumulation, lipid peroxidation, and lipotoxicity in FAO‐dependent leukemia cells [11]. Key dietary origins of gondoic acid include macadamia nuts (15%–25%), canola/rapeseed oil (45%–60%), sunflower seeds, and peanut oil, where precursor fatty acids are metabolized to eicosenol equivalents.

Jojoba oil (Simmondsia chinensis seed wax) stands out as the richest source, containing 22%–44% eicosenol within wax esters like eicosenyl eicosenoate, making it a prime candidate for lipid delivery applications. Already utilized in functional foods, supplements, and cosmetics for its emollient properties, jojoba‐derived eicosenol exemplifies how common plant lipids can be repurposed to target cancer metabolism, exploiting peroxisomal vulnerabilities in leukemias while sparing normal cells with robust redox defenses.

10. Upstream Regulators of pFAO: Emerging Links and Gaps

Peroxisome proliferator‐activated receptors (PPARs) are ligand‐activated nuclear receptors that function as transcription factors, regulating genes involved in lipid metabolism, inflammation, and cellular differentiation. The role of PPARs in carcinogenesis has been reviewed elsewhere [10, 66, 67, 68]. Here, we focus on the potential link between PPARs and the regulation ofperoxisomal gene expression in leukemia.

In AML, PPARδ promotes FAO and leukemic survival, and its pharmacologic inhibition with an antagonist suppresses FAO in vitro [13]. High‐fat diet (HFD)‐induced obesity accelerates acute promyelocytic leukemia (APL, an AML subtype) in PML‐RARα mouse models by increasing disease penetrance, or the proportion of susceptible mice developing leukemia, and shortening latency, the time from genetic predisposition to tumor onset. HFD boosts preleukemic progenitor self‐renewal via PPARδ activation, which drives FAO and metabolic reprogramming. Although peroxisomes were not studied, PPARδ antagonism blocks this effect, linking dietary lipids and PPARδ to APL initiation [69]. PPARδ is also upregulated in CLL versus normal lymphocytes, and its genetic knockout or pharmacological inhibition with DG172 reverses the survival benefits via cholesterol‐driven membrane effects [70, 71].

Interestingly, PPARα pan‐agonist (chiglitazar) treatment alone [72] or in combination with histone deacetylase (HDAC) inhibitor synergistically targets AML leukemia stem cells (LSCs) by inducing ferroptosis while sparing normal progenitors. This combination shows efficacy in cell lines, patient samples, and xenograft models [73]. PPARγ agonist (pioglitazone) also induces anti‐leukemic effects in non‐M3 AML via apoptosis and the PTEN pathway [74]. This highlights isoform‐specific, context‐dependent effects in AML (pro‐tumor δ vs. antitumor α, γ).

However, current data indicate that PPAR‐associated anti‐leukemic effects are largely independent of pFAO and fail to explore the link to modulating peroxisomal activity. It is critical to note that in solid tumors, PPARs regulate a number of genes involved in lipid metabolism, including peroxisomal ACOX1 [10, 75]. In glioma stem cells (GSCs), PPARα transcriptionally drives key FAO enzymes, including mitochondrial CPT1A and peroxisomal ACOX1 [10]. PPARα knockdown reduces CPT1A and ACOX1 expression, impairing proliferation and clonogenicity [10]. These findings highlight PPAR as a potential regulator of peroxisomal ACOX1, which has been unexplored in leukemia, offering a mechanistic link to investigate PPAR‐targeted therapies that enhance pFAO vulnerability.

11. Future Directions and Clinical Translation

Future directions center on rigorously validating the PPAR‐pFAO axis through targeted approaches like ChIP‐seq to map PPARδ binding at ACOX1/ABCD1 promoters, alongside CRISPR‐based co‐knockdown experiments to dissect their functional interplay in leukemia models. In vivo studies expanding CLL and AML xenografts with TDYA or eicosenol, coupled with combination trials, such as pFAO inhibitors plus venetoclax/BCL2 antagonists for CLL or Ven for AML, will be pivotal to translate these synergies into clinically meaningful outcomes. Biomarker development offers a clear path forward, leveraging ABCD1/ACOX1 expression levels, VLCFA accumulation profiles, and lipid droplet dynamics to stratify responsive patients and monitor therapeutic response. Key challenges remain, including optimizing TDYA and eicosenol for better potency and pharmacokinetics, which may necessitate novel small‐molecule screens to achieve drug‐like properties suitable for clinical advancement.

12. Conclusion

Peroxisomes and pFAO emerge as overlooked metabolic hubs in leukemia, fueling survival, resistance, and lipotoxic vulnerabilities distinct from normal hematopoiesis. From lipid peroxidation cascades and ROS shuttling to synergistic FAO dual‐targeting, findings in AML and CLL illuminate peroxisome‐centric mechanisms, selective VLCFA overload, adaptive rewiring, and chemotherapy sensitization, that position pFAO inhibitors like eicosenol and TDYA as high‐potential combination partners. While solid tumor precedents underscore broader relevance, leukemia‐specific transcriptomic hints in resistant subsets await functional pursuit; future in vivo validation, biomarker refinement, and drug optimization will propel this axis toward clinical trials, offering a fresh therapeutic frontier to dismantle metabolic resilience in blood cancers.

Author Contributions

Ekaterina N. Parfenova and Paul A. Spagnuolo wrote and edited the manuscript.

Funding

The authors have nothing to report.

Conflicts of Interest

The authors declare no conflicts of interest.

Data Availability Statement

Data sharing not applicable to this article as no datasets were generated or analyzed during the current study.