The Role of SAMHD1 in Viral Resistance and Transduction Efficiency Challenges in Pediatric Hematological Malignancies: Mechanistic Insights and Clinical Perspectives

ABSTRACT

Sterile alpha motif and HD domain‐containing protein 1 (SAMHD1) is a dNTPase that regulates intracellular nucleotide pools, preserves genomic stability, and mediates intrinsic antiviral immunity. While its role in adult hematologic malignancies is established, its implications for pediatric leukemia—particularly acute myeloid leukemia (AML) and acute lymphoblastic leukemia (ALL)—remain underexplored. This review integrates transcriptomic, protein interaction, and immune correlation analyses to examine the dual role of SAMHD1 in pediatric hematological malignancies: as an antiviral restriction factor that impairs lentiviral gene therapy and as a therapeutic barrier that limits the efficacy of nucleoside analog‐based chemotherapy. We compare emerging transduction‐enhancing strategies, including Vpx delivery, SAMHD1 inhibition, and lipid nanoparticles, and evaluate their pediatric applicability. A conceptual schematic highlights the translational challenges unique to the developing immune and hematopoietic systems. Limitations of commonly used cellular models, such as THP‐1 cells, are discussed alongside the need for pediatric‐specific preclinical tools. We conclude by outlining a clinical translation roadmap and emphasizing the urgency of validating SAMHD1‐targeted strategies in pediatric trials to ensure their safety, efficacy, and integration into future treatment paradigms.

SAMHD1 regulates intracellular dNTP pools, influencing lentiviral transduction, gene therapy efficiency, and disease progression in pediatric hematological malignancies. Integrated bioinformatics and targeted strategies, including CRISPR and pharmacological inhibition, highlight its therapeutic potential.

1. Introduction

Hematopoietic stem cells (HSCs) are located within the bone marrow, occupying specific niches that regulate their activity and function. HSCs can become dysregulated through various genetic mutations and epigenetic changes, leading to the development of acute lymphoblastic leukemia (ALL) and acute myeloid leukemia (AML), which exhibit significant variability in genetic makeup and phenotype [1, 2]. The two subtypes represent the predominant and most clinically significant hematological malignancies in pediatric patients [3, 4]. These disruptions impair the normal homeostatic functions of HSCs, promoting clonal expansion, malignant transformation, and disease progression [5]. Although congenital neutropenia is not a leukemic condition, its clinical management often involves HSC transplantation, a therapeutic strategy also critical in treating relapsed or refractory ALL and AML. This highlights the broad applicability of stem cell‐based therapies across a range of hematological disorders, including leukemia. It is essential to reestablish bone marrow function following intense chemotherapy, especially when treating hematological malignancies [6]. However, due to the genetic heterogeneity of ALL and AML, as well as their tendency to resist current therapeutic approaches, they present significant clinical challenges.

By controlling cell proliferation, the cell cycle, genome stability, and innate immunity protein sterile alpha motif and HD domain‐containing deoxynucleoside triphosphate triphosphohydrolase 1 (SAMHD1) plays a crucial role in HSC differentiation, maintaining HSC homeostasis, and preventing dysregulated hematopoiesis [7]. The SAMHD1 protein comprises 626 amino acids (~72 kDa) and is encoded by the SAMHD1 gene on chromosome 20 (20q11.23), containing 16 exons [8, 9, 10]. A multifunctional enzyme, SAMHD1 hydrolyzes deoxynucleoside triphosphates (dNTPs), regulating the intracellular dNTP pools necessary for DNA synthesis and repair [10]. Its activity may therefore limit lentiviral replication while preserving genomic integrity throughout the cell division process, presenting both possibilities and challenges for gene therapy. Consequently, in this review, we aim to bridge the gap between clinical observations and pharmaceutical interventions, emphasizing the need for innovative approaches that target either the SAMHD1 gene or the SAMHD1 protein in hematological malignancies such as ALL and AML.

Normal hematopoiesis and effective reactions to intense chemotherapy in pediatric patients also depend on genomic stability. While SAMHD1 was initially discovered to play a role in restricting the human immunodeficiency virus (HIV) and facilitating DNA repair, it has since been implicated in pediatric hematological malignancies. Notably, gene therapy and lentiviral vector techniques have therapeutic potential but present complications due to their modulation of dNTP pools and antiviral responses [11, 12]. This review examines the role of SAMHD1 in treatment resistance and transduction efficiency in pediatric hematological malignancies, exploring potential strategies for targeted interventions. While targeting SAMHD1 in leukemia management has clinical promise, the restrictive effects of the SAMHD1 protein on viral replication present a significant obstacle for lentiviral‐mediated gene therapies, an emerging approach for treating genetic hematological disorders.

2. SAMHD1 In Hematopoietic Regulation and Leukemogenesis

Strong evidence links HSCs to the development of specific myeloid leukemia subtypes, although the exact cellular targets of transformational mutations remain unknown [13]. Notably, in NOD/SCID mice, AML is initiated exclusively by HSCs exhibiting a CD34⁺CD38⁻ phenotype. In contrast, their CD34⁺CD38⁺ leukemic blast counterparts do not induce AML despite their leukemic phenotype [14]. This suggests that in AML, transformative mutations primarily arise in normal HSCs, rather than in hematopoietic progenitor cells (HPCs), reinforcing their central role in leukemogenesis. However, additional evidence indicates that HPCs can also undergo transformation, implying the involvement of more differentiated cells than HSCs or pluripotent progenitors [15]. These findings suggest that mutations may arise in HSCs in human leukemia, subsequently altering downstream progenitors and contributing to the development of leukemic cells.

Transformative mutations also refer to acquired genetic alterations in HSCs or HPCs that confer abnormal self‐renewal capacity, block normal differentiation, and drive uncontrolled clonal expansion, a hallmark of leukemogenesis. In AML, such mutations frequently involve genes that regulate signaling (e.g., FMS‐related receptor tyrosine kinase 3, FLT3), transcription (e.g., RUNX family transcription factor 1, RUNX1), or chromatin remodeling (e.g., DNA methyltransferase 3 alpha, DNMT3A), leading to a hierarchical leukemic clone architecture [16, 17, 18, 19, 20]. These mutations may also occur in pluripotent progenitors or more differentiated cells. Meanwhile, the bone marrow microenvironment—populated by both innate and adaptive immune cells—paradoxically supports leukemia progression [21], highlighting the complexity of myeloid leukemogenesis, which likely involves factors beyond genetic mutations.

2.1. Synthesis and Perspective

Transformative mutations in hematopoietic stem and progenitor cells (HSPCs) disrupt normal lineage specification, promoting leukemic clonal expansion. In pediatric AML, developmental timing and distinct immune signaling pathways may further influence this transformation process. Given its role in maintaining genomic integrity, SAMHD1 is emerging as a potential modulator of early leukemogenic events, possibly by regulating the balance of dNTPs during hematopoiesis [7, 22]. By integrating multi‐cohort genomic and transcriptomic data, recent studies have uncovered a synergistic interplay between metabolic and epigenetic dysregulation in MDS, where PSAT1 upregulation aligns with DNMT3A and TET2 mutations to promote immune evasion and therapeutic resistance [23, 24].

3. Challenges in Lentiviral Transduction Efficiency and THP‐1 Model Limitations

While lentiviral vectors are widely used in gene therapy for hematological malignancies, pediatric leukemic cells often exhibit resistance to transduction. In cellular models—such as the THP‐1 cell line, which was derived from a 1‐year‐old male with acute monocytic leukemia (AML‐M5 subtype) and is commonly used to simulate human monocytic leukemia—the SAMHD1 protein depletes intracellular dNTP pools, thereby inhibiting reverse transcription and reducing viral transduction efficiency [25, 26, 27]. Indeed, similar challenges have been observed in pediatric cell studies, which have reported enhanced innate immune responses and robust cellular defense mechanisms. Optimized protocols, such as the use of pharmaceutical agents (e.g., specific SAMHD1 inhibitors) and alternative transfection methods (e.g., electroporation or lipid‐based systems), are being investigated to overcome these barriers, a crucial step for advancing gene‐editing technologies like clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR‐associated protein 9 (Cas9) in leukemia therapy [28]. Given the developmental variations in cellular physiology, future investigations are needed to evaluate the safety and feasibility of translating these approaches to pediatric applications.

3.1. Synthesis and Perspective

SAMHD1‐mediated restriction poses a significant challenge in gene delivery platforms targeting pediatric hematological malignancies. Strategies aimed at modulating SAMHD1 activity must take into account differences in immune maturity and nucleoside metabolism between children and adults [8, 29].

Despite critical clinical relevance, the isolation and characterization of HSCs remain challenging, primarily due to their low abundance in tissues and the absence of a definitive phenotypic marker [30]. Consequently, HSC research primarily focuses on adult stem cell populations [31]. HSCs are multipotent, capable of generating both myeloid (e.g., monocytes, macrophages, neutrophils, erythrocytes, and platelets) and lymphoid (e.g., T, B, and natural killer cells) lineages [30]. Their lifelong ability to self‐renew and differentiate into all blood cell types underscores their critical role in hematopoiesis [32]. Unlike HPCs and more differentiated cells, which undergo transient proliferation and have limited lifespans, HSCs exhibit remarkable plasticity, potentially enabling their differentiation into cell types of other tissues [33]. This regulation, essential from fetal development through adulthood, is governed by a complex interplay of intrinsic cellular mechanisms and external factors [34].

Ongoing efforts are focused on developing stem cell therapies for hematological disorders caused by genetic and metabolic disturbances [35]. Addressing the hematopoietic suppression that results from genetic manipulation is particularly crucial. HSC transplantation has become a standard treatment for hematological malignancies and immune disorders [36]. Mutations accumulating in HSCs contribute significantly to the onset and progression of hematopoietic malignancies, particularly myeloid leukemia [37]; understanding the molecular networks regulating stem cells could therefore lead to novel treatments for refractory disease. Checkpoint mechanisms that activate DNA repair are crucial for maintaining genomic integrity and tissue homeostasis in stem cells [38]. Therefore, targeting these mechanisms could enhance therapeutic strategies to preserve HSC function and more effectively treat hematological disorders.

4. Challenges in Transfecting the THP‐1 Cell Line

Despite THP‐1 being a suspension cell line, it is notoriously resistant to transfection. Laguette et al. identified the underlying host factor and demonstrated that the SAMHD1 protein inhibits the replication of lentiviruses—including HIV—in various immune cells, such as dendritic cells, macrophages, monocytes (including THP‐1 cells), and resting CD4⁺ T cells. Specifically, SAMHD1 in THP‐1 cells impedes HIV type 1 (HIV‐1) infection by blocking reverse transcription, suggesting a potential comparable barrier to efficient lentiviral transduction [25]. To investigate SAMHD1 further, we utilized the Gene Expression Profiling Interactive Analysis (GEPIA) web platform to examine expression levels across multiple independent cohorts [39]. As illustrated in Figure 1A, SAMHD1 expression was higher in AML patients than in those with other malignancies or normal tissue. Despite its significantly upregulated expression profile across all cohorts, samples harboring SAMHD1 mutations showed substantial expression in both AML and diffuse large B‐cell lymphoma (DLBC) cohorts (Figure 1B). This significant expression in AML suggests that mutations in SAMHD1 are subject to distinct regulatory mechanisms in AML cells but not in DLBC cells.

FIGURE 1.

The gene expression profile of SAMHD1 across multiple independent cohorts. (A) The bars show the upregulation of SAMHD1 in tumor and healthy samples. (B) SAMHD1 expression in patients with AML and DLBC compared to healthy individuals. ACC, adrenocortical carcinoma; BLCA, bladder urothelial carcinoma; BRCA, breast invasive carcinoma; CESC, cervical squamous cell carcinoma and endocervical adenocarcinoma; CHOL, cholangio carcinoma; COAD, colon adenocarcinoma; DLBC, lymphoid neoplasm diffuse large B‐cell lymphoma; ESCA, esophageal carcinoma; GBM, glioblastoma multiforme; HNSC, head and neck squamous cell carcinoma; KICH, kidney chromophobe; KIRC, kidney renal clear cell carcinoma; KIRP, kidney renal papillary cell carcinoma; LAML, acute myeloid leukemia; LGG, brain lower grade glioma; LIHC, liver hepatocellular carcinoma; LUAD, lung adenocarcinoma; LUSC, lung squamous cell carcinoma; MESO, mesothelioma; OV, ovarian serous cystadenocarcinoma; PAAD, pancreatic adenocarcinoma; PCPG, pheochromocytoma and paraganglioma; PRAD, prostate adenocarcinoma; READ, rectum adenocarcinoma; SARC, sarcoma; SKCM, skin cutaneous melanoma; STAD, stomach adenocarcinoma; TGCT, testicular germ cell tumors; THCA, thyroid carcinoma; THYM, thymoma; UCEC, uterine corpus endometrial carcinoma; UCS, uterine carcinosarcoma; UVM, uveal melanoma. The visualization reflects data that integrate TCGA and GTEx datasets, obtained from GEPIA 2021 (v2.1), based on RNA‐seq expression analysis. Statistical comparisons were performed using one‐way ANOVA with Tukey's post hoc test, based on cohorts of AML (n = 173), DLBC (n = 48), and healthy GTEx‐matched controls. A significance threshold of p < 0.01 was applied.

As shown in Figure 1, GEPIA2021 analysis revealed statistically significant upregulation of SAMHD1 in AML and DLBC cohorts (AML: n = 173; DLBC: n = 48) relative to GTEx‐matched normal controls (p < 0.01, ANOVA with Tukey's test). This differential expression is supported by GEPIA2021 analysis integrating TCGA/GTEx datasets. Notably, SAMHD1 is transcriptionally upregulated in AML progenitor‐enriched clusters, consistent with reports that link elevated SAMHD1 to impaired nucleoside analog efficacy and innate immune evasion [7]. Therefore, protocols optimized to improve transfection efficiency are recommended for THP‐1 cells. Several factors may influence gene expression and cell signaling transduction, potentially explaining the significant difference in SAMHD1‐mediated restriction of viral replication between parental and transduced THP‐1 cells. Therefore, moving beyond this phenotype makes it easier to research cellular mechanisms, pathogenesis, and potential therapeutic strategies for ALL and AML.

Then, we utilized the STRING database [40] to perform protein–protein interaction analysis to examine the involvement of SAMHD1 in hematopoiesis in greater depth and explore its potential as a therapeutic target. This analysis revealed a robust network of interacting proteins (Figure 2), predominantly associated with antiviral defense mechanisms (GO:0051607) and hematopoiesis (GO:0030097). As shown in Figure 2, SAMHD1 also clusters with innate immune regulators such as MX dynamin‐like GTPase 2 (MX2) and hematopoietic factors like GATA2, indicating its dual functional relevance. The network comprises 20 top‐ranked proteins derived from STRING (v11.5), filtered by GO terms and confidence scores > 0.7. Notably, proteins involved in cellular antiviral responses (shown in red) exhibited strong interconnectivity, including MX2, which exhibits potent antiviral activity against HIV‐1 [41]. Proteins linked to hematopoietic processes (shown in blue) similarly formed tightly clustered interaction hubs. These findings support the notion that the SAMHD1 protein plays a pivotal role in modulating lentiviral entry and replication within the hematopoietic environment, particularly in hematological malignancies. The STRING v11.5 network highlights SAMHD1's co‐expression with antiviral effectors (e.g., MX2, IFIT1) and hematopoietic regulators (e.g., GATA2), reflecting its dual functional positioning. Previous studies have shown that SAMHD1‐mediated dNTP regulation directly influences hematopoietic lineage commitment and viral restriction [22].

FIGURE 2.

STRING‐derived protein–protein interaction network of co‐expressed genes enriched in the GO:0051607 (defense response to virus) and GO:0030097 (hemopoiesis) biological processes. The network illustrates functionally clustered proteins involved in antiviral defense (e.g., MX2) (red nodes), while blue nodes denote hematopoiesis‐related factors. The network highlights SAMHD1's involvement at the intersection of innate immunity and blood cell development, highlighting molecular interactions potentially relevant to hematological malignancies. The network was generated using STRING version 11.5 (2023) with a minimum confidence interaction score threshold of > 0.7, and includes the top 20 predicted interactors based on co‐expression, text mining, and experimental validation.

5. Therapeutic Targeting of SAMHD1 and Pediatric Considerations

To advance therapeutic and research applications relating to transduction efficiency in pediatric hematological malignancies, we compared the major strategies currently employed to overcome SAMHD1‐mediated barriers. Table 1 summarizes the mechanisms, efficiency, cell viability, and pediatric relevance of these approaches.

TABLE 1.

Comparative strategies to overcome SAMHD1‐mediated transduction resistance in hematologic cells.

Strategy	Mechanism	Transduction efficiency	Cell viability	Pediatric applicability
Vpx delivery	Degrades SAMHD1 via DCAF1‐mediated proteasomal pathway	High (in monocytes/THP‐1)	Moderate (transient immune activation)	Limited pediatric data
SAMHD1 inhibitors	Small‐molecule suppression of dNTPase activity	Moderate	Variable (dose‐dependent)	Preclinical; not yet tested in children
Electroporation	Physical membrane disruption	Variable (cell‐dependent)	Low to moderate (risk of cytotoxicity)	Used in pediatric CAR‐T protocols
Lipid nanoparticles	Encapsulation of nucleic acids for targeted delivery	Moderate	High	Favorable safety; studied in pediatric vaccines

Note: Data were adapted from multiple preclinical and translational studies [7, 42, 43, 44, 45, 46, 47, 48], integrating mechanistic insights with current experimental evidence.

One of the most promising therapeutic strategies under investigation involves modulating the activity of the SAMHD1 protein to overcome treatment resistance. SAMHD1 contributes to chemoresistance by hydrolyzing the active triphosphate forms of nucleoside analogs commonly used in the treatment of pediatric leukemia. Notably, SAMHD1 deactivates cytarabine triphosphate (Ara‐CTP) and clofarabine triphosphate (Cl‐F‐ATP), reducing their intracellular efficacy. In preclinical models, including AML and ALL cell lines, high SAMHD1 activity has been associated with a poor response to these agents. Inhibiting SAMHD1 has been proposed as a strategy for sensitizing leukemic cells to nucleoside analogs, particularly in cytarabine‐refractory pediatric AML [11, 49].

To evaluate the clinical relevance of SAMHD1, we analyzed the GEPIA2021 dataset [50]. Specifically, we conducted a proportion correlation analysis in AML and DLBC subsets between monocytes, the primary cellular targets of SAMHD1 activity, and two B cell subtypes (naïve and memory), which are indicators of immune suppression or maturation [25, 51, 52, 53]. As illustrated in Figure 3A, a weak negative correlation exists between naïve B cells and monocytes, suggesting minimal interaction or competition between these cell types in AML and DLBC tumors. Meanwhile, as illustrated in Figure 3B, a moderate negative correlation exists between memory B cells and monocytes; this suggests that higher monocyte infiltration may be associated with a relative suppression or displacement of memory B cells, which might indicate myeloid‐driven immune evasion in these malignancies. These GEPIA‐derived correlations suggest that a monocyte‐skewed immune landscape may suppress B cell development, an effect observed in pediatric AML with elevated SAMHD1 expression [54]. This immune context represents a monocyte‐dominant microenvironment characterized by high monocyte infiltration and reduced B cell presence, a pattern often associated with immunosuppressive signaling and limited adaptive immune engagement in leukemia [55]. As shown in Figure 3, SAMHD1 gene expression was positively correlated with monocytes (R = 0.48, p < 0.01) and inversely with memory B cells (R = −0.41, p < 0.01), highlighting an immunosuppressive network that may influence pediatric leukemic immune escape and gene therapy outcomes. This immunological bias may compromise vaccine responses or the efficacy of gene therapy in young patients. Collectively, these data suggest a potential immunosuppressive influence of monocyte‐dominant microenvironments on B cell‐mediated immunity. These findings are relevant to understanding how SAMHD1‐expressing monocytes may indirectly shape the immune landscape in pediatric hematological malignancies and thus influence the efficacy of viral gene therapy.

FIGURE 3.

Monocyte abundance was negatively correlated with B cell subtypes in acute myeloid leukemia (AML) and diffuse large B‐cell lymphoma (DLBC) tumors. Scatterplots show the correlation between the proportion of monocytes and two B cell subtypes, naïve B cells (left) and memory B cells (right), across AML (blue) and DLBC (orange) tumor samples. A weak negative correlation (Pearson's r = −0.126) exists between monocytes and naïve B cells, while a moderate negative correlation (r = −0.346) exists between monocytes and memory B cells. The analysis was conducted using GEPIA2021 (v2.1), which estimates immune cell infiltration based on deconvoluted bulk RNA‐seq expression data from TCGA. Statistical correlations were computed using Spearman's method, with significance set at p < 0.01. The sample size for the combined AML and DLBC cohorts was approximately n = 173.

Mutations in SAMHD1 are common in hematological malignancies and are associated with poor therapeutic outcomes, suggesting that SAMHD1 is essential for immunoregulation and homeostasis; however, its precise involvement in leukemogenesis remains unknown [56]. In patients with AML, loss‐of‐function mutations in SAMHD1 have been identified as an indicator of a poor prognosis, potentially inducing uncontrolled DNA damage response and promoting leukemogenesis [57]. Similarly, recurrent SAMHD1 mutations in chronic lymphocytic leukemia (CLL) likely impact the DNA damage response, contributing to leukemogenesis and chemoresistance [12]. Targeting SAMHD1 presents a promising therapeutic strategy for enhancing the efficacy of gene therapy and mitigating resistance to nucleoside analog‐based chemotherapy in leukemia treatment.

Recent research has identified small‐molecule inhibitors that selectively suppress SAMHD1's dNTP hydrolase activity, thereby increasing intracellular dNTP pools, essential for efficient viral vector‐based gene delivery and nucleoside analog cytotoxicity [7, 22]. In pediatric leukemias, SAMHD1 inhibitors may serve a dual function, both enhancing the efficiency of gene transfer methods and increasing the sensitivity of leukemic cells to conventional chemotherapeutic agents. Immune cell interactions are also likely to influence the efficacy of gene therapy and immunotherapy responses. In monocyte‐enriched malignancies—particularly AML—reduced memory B cell activity may compromise antibody‐mediated immune memory and potentially affect the efficacy of viral delivery systems, such as lentiviral or adeno‐associated virus vectors. This issue is particularly relevant in contexts where SAMHD1 is highly expressed in monocytes, posing an additional barrier to successful gene transfer.

5.1. Pediatric Consideration

While much of the current knowledge surrounding SAMHD1 originates from adult studies, emerging data suggest that its expression and function differ in children. For example, neonatal and infant monocytes exhibit heightened SAMHD1 activity; this may contribute to enhanced innate immunity, but pose additional barriers to viral gene therapy [42]. Moreover, the developing immune microenvironment in children alters the functional landscape of restriction factors, such as SAMHD1. These age‐dependent differences underscore the importance of pediatric‐specific pharmacokinetic, safety, and efficacy studies; caution must be exercised when applying adult data to pediatric contexts. In instances where such extrapolation was unavoidable, we have clearly noted it. Table 2 summarizes the origin and age specificity of key data sources used throughout the review.

TABLE 2.

Age, origin, and context of key data sources referenced in this review.

Context	Data source	Age group	Notes
THP‐1 Transduction	THP‐1 Cell Line (ATCC)	Pediatric (1 year)	Derived from 1‐year‐old male; pediatric origin [27]
GEPIA Analysis	TCGA & GTEx	Adult	Data derived from adult patients and controls [58]
SAMHD1 Inhibitor Trials	Preclinical animal models	Adult	Extrapolated with caution [59]
SAMHD1 expression data	Baldauf et al. [42]	Pediatric/neonatal	High SAMHD1 in neonatal monocytes [42]

Note: Data were adapted from sources as noted.

5.2. Synthesis and Perspective

Targeting the SAMHD1 protein in pediatric patients offers potential synergy between chemotherapy and gene therapy. However, caution is required due to pediatric‐specific pharmacokinetic profiles and the influence of immune development stages [7, 36].

6. Clinical Translation Roadmap and Safety Challenges

Despite recent advances, several critical challenges must be addressed before SAMHD1‐targeted strategies can be translated into clinical practice, particularly in pediatric settings. One primary concern is safety. Prolonged or excessive inhibition of SAMHD1 may disrupt intracellular nucleotide homeostasis, potentially leading to genomic instability. This risk is especially significant in children, where rapid tissue development and cellular proliferation heighten their vulnerability to genomic damage [22]. Additionally, pediatric‐specific data are lacking, as most preclinical and clinical studies have utilized adult tissue‐based models and populations. This deficiency underscores the urgent need for pediatric cohort studies to evaluate age‐specific pharmacodynamics (PD), pharmacokinetics (PK), and long‐term safety outcomes. Moreover, while combining SAMHD1 inhibition with established therapeutic approaches such as nucleoside analogs or CRISPR/Cas9‐based gene editing holds promise for enhancing treatment efficacy, these strategies require precise dosing regimens and vigilant monitoring to avoid unintended cytotoxicity or off‐target effects [7].

The PK and PD of SAMHD1 inhibitors remain largely uncharacterized in pediatric patients. Age‐specific variables such as hepatic enzyme immaturity, variable renal clearance, and blood–brain barrier permeability may significantly alter drug absorption and distribution profiles. Without specific pediatric PK/PD modeling, dosing regimens may inadvertently lead to under or overdosing, compromising efficacy or increasing toxicity [36]. Moreover, the developing hematopoietic and immune systems in children may be more susceptible to off‐target effects. Sustained SAMHD1 inhibition may perturb DNA replication fidelity, mitochondrial function, or nucleotide balance, potentially contributing to genotoxic stress or immunological dysregulation during critical developmental windows [22, 60].

Ethical and regulatory considerations are equally important. Pediatric trials involving genome editing or SAMHD1‐modulating agents must adhere to stricter consent frameworks than adult equivalents, including parental permission, child assent, and commitments to long‐term follow‐up. Current guidelines, such as those from the EMA and NIH, call for pediatric‐specific risk–benefit analyses before initiating first‐in‐child trials. These frameworks aim to prevent irreversible harm while enabling access to promising therapies [61].

Future research should prioritize the development of preclinical models that accurately reflect pediatric physiology and leukemic progression to optimize dosing strategies and delivery platforms. Early‐phase clinical trials involving pediatric cohorts will be crucial for validating the safety and therapeutic efficacy of SAMHD1 inhibitors in this vulnerable population. Appropriately modulated, SAMHD1 protein activity may enhance the therapeutic index of existing treatments, not only by improving drug delivery and efficacy but also by restoring nucleotide homeostasis and increasing the sensitivity of leukemic cells to chemotherapeutic agents.

7. Transforming Mutations and Leukemia Progression

Transformative mutations reprogram HSCs or HPCs, conferring aberrant self‐renewal and impaired differentiation. In AML, key drivers such as FLT3, RUNX1, and DNMT3A shape clonal hierarchies and fuel disease persistence [16, 17]. In AML, the proliferation of leukemic cells is driven by the PML nuclear body scaffold (PML)‐retinoic acid receptor alpha (RARA) gene fusion and mutations in FLT3 [62, 63]. Due to its role in nucleotide metabolism, the SAMHD1 protein indirectly influences several related activities. Pharmaceutical therapies targeting SAMHD1 may improve treatment outcomes, restore normal hematopoiesis, and disrupt leukemic hierarchies [11]. Leukemia progression is also significantly influenced by the bone marrow microenvironment, which is abundant in stromal and immune cells. Developing comprehensive treatment solutions requires addressing both cellular and microenvironmental aspects.

8. Overcoming Transduction Barriers in THP‐1 Cells

The THP‐1 cell line exhibits significant resistance to lentiviral transduction due to its suspension nature, adhesive properties, and robust innate defense mechanisms. Meanwhile, the SAMHD1 protein suppresses lentiviral transduction by inhibiting the reverse transcription process [25]. The use of optimized lentiviral transduction protocols and pharmacological enhancers—such as SAMHD1 inhibitors—is warranted to advance gene therapy applications and enhance research in monocytic leukemia.

9. Limitations and Future Directions

This review has several inherent limitations. Although we aimed to highlight pediatric hematological malignancies, many of the mechanistic insights referenced are extrapolated from adult studies or generalized models, such as THP‐1 cells [42, 49]. The lack of pediatric‐specific data on SAMHD1 protein expression, function, and therapeutic targeting limits the direct translatability of current findings. Moreover, the transcriptomic correlations and schematic representations presented here are hypothesis‐generating and require validation in age‐matched clinical and preclinical models [58, 64]. Despite notable advances, therapeutically targeting SAMHD1 remains a significant challenge; the development of SAMHD1‐specific modulators requires a balance between maintaining genomic stability and enhancing therapeutic efficacy, which is particularly critical in pediatric patients.

In addition, the inherent resistance of specific cell lines, such as THP‐1, to genetic manipulation underscores the need for innovative delivery strategies and optimized methodologies. Future research should integrate SAMHD1‐targeting approaches with existing treatment regimens to improve outcomes for hematological malignancies such as AML and CLL. The successful translation of these strategies will depend on coordinated efforts between researchers, clinicians, and pharmaceutical developers.

While our understanding of SAMHD1's role in hematological malignancies has grown considerably, critical gaps remain, particularly in pediatric contexts. Most notably, the lack of pediatric‐specific data and in vivo validation remains a significant limitation, as most preclinical and clinical studies have focused on adult models and populations. The trade‐off between enhancing transduction efficiency and preserving genomic integrity is also particularly challenging in children, necessitating careful assessment of the long‐term consequences of SAMHD1 inhibition. Innovative transduction methods adapted for pediatric cells are needed to optimize gene delivery while ensuring cellular viability. Comprehensive preclinical studies using pediatric models, along with tailored clinical trials, will be crucial for advancing the field.

Incorporating schematic diagrams that depict SAMHD1's molecular pathways and its influence on gene therapy could aid in clarifying its mechanistic role and guiding future therapeutic development. As shown in Figure 4, the dual functionality of SAMHD1, as both an innate immune restriction factor and a therapeutic barrier, has significant implications for the design of pediatric gene therapy and chemotherapy. The schematic illustrates how the SAMHD1 protein affects intracellular dNTP balance, antiviral defense, nucleoside analog resistance, and monocyte‐driven immune suppression; each of these factors complicates viral vector delivery and chemotherapeutic response in children with leukemia.

FIGURE 4.

A conceptual model of SAMHD1's dual functionality in pediatric leukemia: Restriction factor vs. resistance factor. This integrative schematic reimagines the SAMHD1 protein as a molecular fulcrum balancing two opposing roles in pediatric hematological malignancies. On the left, SAMHD1 functions as an antiviral restriction factor, depleting intracellular dNTP pools, blocking reverse transcription, and impeding lentiviral gene transfer, posing a major challenge in gene therapy. On the right, SAMHD1 acts as a therapeutic resistance factor; its overexpression reduces nucleoside analog efficacy (e.g., cytarabine), while loss‐of‐function mutations in the SAMHD1 gene contribute to leukemogenesis. At the base, a pediatric‐specific overlay highlights the challenges posed by immature immune systems, elevated SAMHD1 activity in neonatal monocytes, and translational barriers to gene therapy design. This duality positions SAMHD1 as both a mechanistic challenge and a promising therapeutic target in pediatric oncology.

10. Data Sources and Analysis Methods

• Transcriptomic expression data for SAMHD1 were retrieved using GEPIA2021 (Gene Expression Profiling Interactive Analysis) [58], which integrates RNA‐seq data from TCGA (The Cancer Genome Atlas) and GTEx (Genotype‐Tissue Expression) projects. AML and DLBC datasets were selected to compare expression profiles. Analyses were performed via the online portal at: http://gepia.cancer‐pku.cn.

• Correlation analyses between SAMHD1 expression and immune cell abundance (e.g., monocytes and B cells) were conducted using the GEPIA2021 Immune Deconvolution module, applying Pearson's correlation across multiple immune gene signatures and visualized using built‐in scatterplot functions.

• Protein–protein interaction networks were constructed using STRING v11.5 (Search Tool for the Retrieval of Interacting Genes/Proteins) [64], available at https://string‐db.org/.

• The analysis employed a minimum interaction confidence score of 0.7, focusing on co‐expression and experimentally validated interactions. Filtering was guided by Gene Ontology terms related to “defense response to virus” (GO:0051607) and “hemopoiesis” (GO:0030097).

• All data visualizations were generated using the native output of GEPIA and STRING platforms and annotated manually for interpretative clarity.

11. Conclusions

SAMHD1 represents a molecular paradox in pediatric hematological malignancies. It functions as both an antiviral restriction factor that impairs lentiviral gene transfer, and as a therapeutic barrier that diminishes the efficacy of nucleoside analog‐based chemotherapy. This dual identity complicates efforts to optimize gene and drug delivery in childhood leukemias. While targeting SAMHD1 offers a promising strategy to improve therapeutic outcomes, any clinical application must account for the distinct features of the pediatric immune and hematopoietic environments. This review highlights the pressing need for pediatric‐specific preclinical models, rigorous mechanistic validation, and ethically informed clinical translation. A clearer understanding of SAMHD1's context‐dependent roles will be essential for advancing precision therapies that are both safe and effective for young patients facing high‐risk leukemias.

Conflicts of Interest

The author declares no conflicts of interest.

Alzamzami W., “The Role of SAMHD1 in Viral Resistance and Transduction Efficiency Challenges in Pediatric Hematological Malignancies: Mechanistic Insights and Clinical Perspectives,” European Journal of Haematology 117, no. 3 (2026): 642–652, 10.1111/ejh.70027.

Data Availability Statement

All data used in this review are derived from publicly available sources. Transcriptomic expression data for SAMHD1 were retrieved via the GEPIA2021 portal, which integrates RNA‐seq data from TCGA and GTEx projects. Protein–protein interaction networks were generated using STRING v11.5 with filters based on Gene Ontology annotations. No new datasets were generated or analyzed during the current study. All tools used are publicly accessible at http://gepia.cancer‐pku.cn and https://string‐db.org.