# MTHFD2 Gene: Structure, Function, and Clinical Significance


## Key Takeaways

- MTHFD2 is a bifunctional mitochondrial enzyme crucial for one-carbon metabolism, generating NADPH for redox homeostasis and 10-formyl-THF for purine biosynthesis, with its overexpression a hallmark of numerous cancers.
- Beyond its canonical mitochondrial role, MTHFD2 exhibits non-enzymatic nuclear functions, including centromere integrity during mitosis and regulation of RNA modification (e.g., m⁶A methylation), impacting gene expression and cell division.
- MTHFD2 expression is tightly regulated transcriptionally by factors like ATF4 and MYC, and post-transcriptionally by miRNAs, with its upregulation linked to poor prognosis, chemoresistance, and immune evasion via PD-L1 upregulation.
- Germline *MTHFD2* mutations are not typically associated with Mendelian disorders due to embryonic lethality, but specific SNPs are linked to congenital heart disease risk, highlighting gene-environment interactions with folate intake.
- Small-molecule inhibitors targeting MTHFD2, including substrate-competitive and allosteric agents, are under development as therapeutic strategies, with potential for synergistic effects when combined with antifolates like pemetrexed or venetoclax in specific cancer contexts.
- MTHFD2 plays a role in host-pathogen interactions, notably by Newcastle disease virus to support viral replication, and is implicated in non-cancer pathologies such as sepsis-induced acute kidney injury and atherosclerosis.

---

## Executive Summary & Key Metadata

Methylenetetrahydrofolate dehydrogenase (NADP⁺-dependent) 2, methenyltetrahydrofolate cyclohydrolase (MTHFD2) is a nuclear-encoded, mitochondria-localized bifunctional enzyme that catalyzes two sequential reactions in the folate-mediated one-carbon (1C) metabolism pathway. Beyond its canonical metabolic role, MTHFD2 has emerged as a critical regulator of cellular redox homeostasis, nucleotide biosynthesis, epigenetic programming, and even non-enzymatic nuclear functions, including mitosis and RNA modification. Its overexpression is a hallmark of numerous solid and hematological malignancies, correlating with poor prognosis, chemoresistance, and immune evasion. This manual provides a comprehensive, publication-grade reference covering the genomic architecture, structural biology, signaling networks, pathogenic mutations, pharmacogenomics, and bioinformatic resources for MTHFD2.

| **Attribute** | **Detail** |
| :--- | :--- |
| **HGNC Symbol** | MTHFD2 |
| **UniProt Accession** | P13995 |
| **Representative PDB ID** | 7DNG (and others; see Section 2) |
| **Chromosomal Locus** | 2p13.1 (GRCh38: chr2:74,248,675-74,266,861) |
| **Primary Molecular Function** | Bifunctional methylenetetrahydrofolate dehydrogenase (NADP⁺-dependent) and methenyltetrahydrofolate cyclohydrolase; mitochondrial 1C metabolism; redox homeostasis |
| **Disease & Pathology Associations** | Non-small cell lung cancer, breast cancer, acute myeloid leukemia, glioblastoma, renal cell carcinoma, bladder cancer, congenital heart defects, sepsis-induced acute kidney injury, viral replication (e.g., Newcastle disease virus, coronaviruses) |

---

## 1. Genomic Locus, Chromosomal Organization & Isoforms

### 1.1 Chromosomal Localization and Gene Structure

The *MTHFD2* gene is located on the short (p) arm of chromosome 2 at cytogenetic band 2p13.1. The reference genome assembly (GRCh38) places the gene between coordinates 74,248,675 and 74,266,861 on the forward strand. The gene spans approximately 18.2 kilobases (kb) of genomic DNA and comprises 19 exons, with the translational start site (ATG) located in exon 1 and the stop codon in exon 19. The primary transcript is 3,057 base pairs (bp) long and encodes a 350-amino acid precursor protein, which includes an N-terminal mitochondrial targeting sequence (MTS) of approximately 30 amino acids that is cleaved upon import into the mitochondrial matrix.

The promoter region of *MTHFD2* lacks a canonical TATA box but contains a high-density CpG island spanning the proximal promoter and exon 1. This CpG island is a known target for DNA methylation-mediated silencing in normal differentiated tissues, while its hypomethylation in cancer cells contributes to the widespread overexpression observed across tumor types. Several transcription factor binding sites have been identified within the proximal promoter, including consensus motifs for:
- **ATF4** (Activating Transcription Factor 4), a master regulator of the integrated stress response (ISR), which binds to the promoter under conditions of amino acid deprivation or ER stress.
- **MYC**, which directly transactivates *MTHFD2* expression in MYCN-amplified neuroblastoma and other MYC-driven tumors.
- **NRF2** (NF-E2-related factor 2), which links oxidative stress responses to 1C metabolism.
- **SF-1/Ad4BP** (Steroidogenic Factor 1), which regulates *MTHFD2* expression in steroidogenic tissues, connecting NADPH production to steroidogenesis.

Enhancer elements have been mapped to regions approximately 5 kb upstream and 10 kb downstream of the transcriptional start site (TSS), based on chromatin state annotations (H3K27ac and H3K4me1) from ENCODE and Roadmap Epigenomics data. These enhancers are cell-type-specific and are particularly active in embryonic stem cells and cancer cell lines, but are repressed in most adult somatic tissues, explaining the relatively restricted expression pattern of MTHFD2 in normal physiology.

### 1.2 Alternative Splicing and Isoforms

Alternative splicing of *MTHFD2* generates multiple transcript variants, some of which encode truncated or catalytically inactive proteins. Nicolaidou et al. (2020) characterized several novel splice variants in cancer cell lines:

- **Variant 1 (Canonical, NM_006636)**: Encodes the full-length 350-amino acid protein. This is the predominant and functionally active isoform.
- **Variant 2 (ΔExon 4)**: An in-frame deletion of exon 4, resulting in a protein lacking a portion of the NADP⁺-binding domain. This isoform retains partial cyclohydrolase activity but has severely reduced dehydrogenase activity.
- **Variant 3 (ΔExons 4-6)**: A frameshift mutation leading to a premature stop codon. This transcript is predicted to undergo nonsense-mediated decay (NMD) and is likely a non-functional byproduct of aberrant splicing.
- **Variant 4 (Retained Intron 8)**: Retains intron 8, introducing a premature termination codon. This isoform is also targeted for NMD.

The expression of these splice variants is tissue-specific and altered in cancer. For instance, the ΔExon 4 variant is upregulated in breast cancer cell lines compared to normal mammary epithelial cells, suggesting a potential role in tumorigenesis or a marker of splicing dysregulation. The functional significance of these isoforms in vivo remains an active area of investigation.

### 1.3 Pseudogenes and Paralogs

*MTHFD2* belongs to a family of folate-metabolizing enzymes that includes the cytoplasmic trifunctional enzyme MTHFD1 and the mitochondrial monofunctional enzyme MTHFD2L (also known as MTHFD2-like). MTHFD2L shares ~60% sequence identity with MTHFD2 and catalyzes the same two reactions but is constitutively expressed in adult tissues, whereas MTHFD2 is predominantly expressed during embryonic development and in transformed cells. The differential expression of these two isozymes is a key regulatory node: MTHFD2L maintains basal mitochondrial 1C flux in normal tissues, while MTHFD2 is induced to support the high proliferative demands of cancer cells. No processed pseudogenes for *MTHFD2* have been annotated in the human genome.

---

## 2. 3D Protein Domain Architecture & Structural Biology

### 2.1 Domain Organization

The MTHFD2 protein is synthesized as a 350-amino acid precursor. The mature protein, after cleavage of the 30-amino acid mitochondrial targeting sequence (MTS), is a 320-amino acid enzyme localized to the mitochondrial matrix. The protein is organized into two distinct functional domains:

1.  **N-terminal Dehydrogenase Domain (Residues ~31-180)**: This domain binds NADP⁺ and catalyzes the oxidation of 5,10-methylene-THF to 5,10-methenyl-THF. The Rossmann fold (a β-α-β-α-β nucleotide-binding motif) is the core structural element, with a conserved GXGXXG motif (residues 96-101) critical for NADP⁺ binding. The catalytic residue is a conserved glutamate (Glu141) that acts as a general base in the hydride transfer reaction.
2.  **C-terminal Cyclohydrolase Domain (Residues ~181-320)**: This domain catalyzes the hydrolysis of 5,10-methenyl-THF to 10-formyl-THF. The cyclohydrolase active site is located in a deep cleft formed by a central β-sheet flanked by α-helices. A conserved histidine (His191) and a lysine (Lys256) are essential for catalysis.

The two domains are connected by a short interdomain linker (residues ~175-185) that allows for conformational changes during the catalytic cycle. The protein assembles into a homodimer, with the dimer interface formed primarily by residues from the dehydrogenase domain. Dimerization is required for enzymatic activity, as the active site of each monomer is completed by residues from the opposing subunit.

### 2.2 Catalytic Mechanism and Active Site Architecture

MTHFD2 catalyzes two sequential reactions in the mitochondrial matrix:

1.  **Dehydrogenase reaction**: 5,10-methylene-THF + NADP⁺ → 5,10-methenyl-THF + NADPH + H⁺
2.  **Cyclohydrolase reaction**: 5,10-methenyl-THF + H₂O → 10-formyl-THF

The dehydrogenase reaction is the primary source of mitochondrial NADPH, which is essential for maintaining the reduced glutathione (GSH) pool and neutralizing reactive oxygen species (ROS). The cyclohydrolase reaction generates 10-formyl-THF, which is used for the *de novo* synthesis of purines (via AICAR transformylase) and for the initiation of mitochondrial protein synthesis (via formylmethionyl-tRNA).

The active site of the dehydrogenase domain is highly specific for NADP⁺ over NAD⁺, a selectivity conferred by a conserved arginine residue (Arg173) that forms a salt bridge with the 2'-phosphate group of NADP⁺. This selectivity is a key difference from the NAD⁺-dependent MTHFD1 enzyme and is a target for isoform-specific inhibitor design.

### 2.3 Allosteric Regulation and Structural Dynamics

Recent structural studies have identified an allosteric binding site in MTHFD2 that is distinct from the substrate and cofactor binding pockets. Lee et al. (2021) solved the crystal structure of MTHFD2 in complex with a series of xanthine derivatives and revealed a previously unknown allosteric pocket located at the dimer interface. Binding of these compounds induces a conformational change that stabilizes an "open" conformation of the enzyme, reducing its catalytic efficiency. This allosteric site offers a promising avenue for the development of non-competitive inhibitors with improved selectivity over the substrate-competitive antifolates.

### 2.4 Post-Translational Modifications and Structural Consequences

MTHFD2 is subject to several post-translational modifications (PTMs) that modulate its activity, stability, and subcellular localization:

- **Lysine Succinylation**: SIRT5-mediated desuccinylation of MTHFD2 at multiple lysine residues (e.g., K126, K214) enhances its enzymatic activity and protein stability. In breast cancer, high SIRT5 expression leads to reduced succinylation, promoting MTHFD2 activity and conferring resistance to therapy-induced senescence.
- **Lysine Acetylation**: Acetylation of MTHFD2 at K83 and K289, regulated by the acetyltransferase GCN5 and deacetylase SIRT3, has been shown to inhibit its enzymatic activity. This modification is dynamically regulated in response to nutrient availability.
- **Phosphorylation**: Although less well-characterized, phosphoproteomic screens have identified phosphorylation sites in the interdomain linker region, potentially modulating domain communication and catalytic activity.

### 2.5 Interactive 3D Visualization

To explore the three-dimensional structure of MTHFD2, including its domain architecture, active site residues, and allosteric binding pocket, use the interactive visualizer below. The tool loads the representative PDB structure and allows for in-depth analysis of the protein's structural features.

[Interactive 3D Protein Visualizer: Load MTHFD2 (PDB: true)](/tools/protein-structure-viewer?source=alphafold&accession=P13995)

---

## 3. Cellular Signaling Pathways & Molecular Function

### 3.1 Canonical Role in Mitochondrial One-Carbon Metabolism

The primary function of MTHFD2 is to support the flow of one-carbon units through the mitochondrial folate cycle. This pathway is essential for:

- **De novo purine biosynthesis**: 10-formyl-THF, the product of the cyclohydrolase reaction, is a substrate for the enzymes AICAR transformylase and GAR transformylase in the purine biosynthetic pathway. Cancer cells with high proliferative rates have an elevated demand for purines, making MTHFD2 a critical node in this biosynthetic program.
- **Redox homeostasis**: The dehydrogenase reaction produces NADPH, which is used by the mitochondrial thioredoxin and glutathione systems to detoxify ROS. In acute myeloid leukemia (AML), MTHFD2 is a selective vulnerability that supports mitochondrial redox balance; its inhibition leads to ROS accumulation and cell death.
- **Methylation reactions**: Mitochondrial 1C metabolism generates formate, which is exported to the cytoplasm and feeds into the cytoplasmic folate pool. This pool is used for the synthesis of S-adenosylmethionine (SAM), the universal methyl donor for DNA, RNA, and protein methylation.

### 3.2 Non-Canonical Nuclear Functions

Contrary to the traditional view of MTHFD2 as a strictly mitochondrial enzyme, a growing body of evidence demonstrates that a fraction of MTHFD2 localizes to the nucleus, where it performs non-enzymatic functions critical for cell division and gene expression.

- **Mitosis and Centromere Integrity**: Nuclear MTHFD2 is required for correct mitotic progression. Pardo-Lorente et al. (2024) demonstrated that MTHFD2 localizes to the centromeres during mitosis, where it interacts with the constitutive centromere-associated network (CCAN) and the chromosomal passenger complex (CPC). Depletion of nuclear MTHFD2 leads to aberrant chromosome segregation, micronuclei formation, and aneuploidy. This function is independent of its catalytic activity, as a catalytically dead mutant can rescue the mitotic defects.
- **RNA Modification and Gene Expression**: MTHFD2 has been shown to interact with RNA-binding proteins and components of the m⁶A (N6-methyladenosine) methylation machinery. In breast cancer, MTHFD2 promotes the m⁶A methylation of IFRD1 mRNA, leading to its degradation and subsequent activation of the HDAC3/p53/mTOR pathway, which drives cell proliferation. Similarly, in sepsis-induced acute kidney injury, MTHFD2 stabilizes LOX (lysyl oxidase) expression through an RNA methylation-dependent mechanism, promoting disease progression.
- **Transcriptional Regulation**: MTHFD2 can act as a transcriptional co-regulator. Its interaction with transcription factors such as MYC and ATF4 creates a positive feedback loop that reinforces its own expression and the expression of other metabolic genes.

### 3.3 Regulation of MTHFD2 Expression

MTHFD2 expression is tightly controlled at multiple levels:

- **Transcriptional Regulation**: The transcription factors ATF4, MYC, and NRF2 are the primary drivers of MTHFD2 transcription. ATF4 is induced by the integrated stress response (ISR) under conditions of amino acid starvation, ER stress, or oxidative stress, leading to MTHFD2 upregulation. MYC directly binds to the MTHFD2 promoter and is a major driver of its overexpression in MYC-driven cancers.
- **Post-Transcriptional Regulation**: MicroRNAs (miRNAs) play a significant role in fine-tuning MTHFD2 expression. Several miRNAs have been validated to target the 3'UTR of MTHFD2 mRNA, including:
    - **miR-33a-5p**: Suppresses colorectal cancer cell growth by inhibiting MTHFD2.
    - **miR-504-3p**: Acts as a tumor suppressor in AML by targeting MTHFD2.
    - **miR-1251-5p**: Inhibits tumorigenesis and metastasis in renal cell carcinoma by targeting MTHFD2.
    - **miR-124**: Mediates the effect of circMTHFD2 on pemetrexed resistance in gastric cancer.
    - **miR-455-5p**: The lncRNA SNHG3 acts as a sponge for miR-455-5p, leading to increased MTHFD2 expression in endometrial carcinoma.
- **Post-Translational Regulation**: As described in Section 2.4, PTMs such as succinylation, acetylation, and phosphorylation modulate MTHFD2 activity and stability. The mitochondrial chaperone HSPD1 (Hsp60) is required for the proper folding of MTHFD2, independently of its co-chaperone HSPE1 (Hsp10).

### 3.4 Protein-Protein Interaction Networks

MTHFD2 participates in a complex network of protein-protein interactions (PPIs) that extend beyond its metabolic partners. Based on data from BioGRID, STRING, and targeted studies, key interactors include:

| **Interactor** | **Function** | **Biological Consequence** |
| :--- | :--- | :--- |
| **HSPD1 (Hsp60)** | Mitochondrial chaperonin | Folds MTHFD2 upon mitochondrial import |
| **SIRT5** | NAD⁺-dependent deacetylase/desuccinylase | Desuccinylates MTHFD2, enhancing its activity |
| **MYC** | Transcription factor | Co-regulates transcription of MTHFD2 and other 1C genes |
| **ATF4** | Stress-responsive transcription factor | Induces MTHFD2 expression under stress |
| **CENP-A, CENP-C** | Centromere proteins | Mediates mitotic localization of MTHFD2 |
| **AURKB (Aurora B)** | Chromosomal passenger complex kinase | Functional interaction during mitosis |
| **IFRD1** | Interferon-related developmental regulator | mRNA is a target of MTHFD2-dependent m⁶A modification |
| **PD-L1 (CD274)** | Immune checkpoint ligand | MTHFD2 promotes PD-L1 expression, driving immune evasion |
| **PPFIA4** | Scaffolding protein | Enhances MTHFD2-mediated mitochondrial metabolism in CRPC |

### 3.5 MTHFD2 in Cellular Signaling Pathways

MTHFD2 is not merely a downstream effector of oncogenic signaling; it actively participates in and modulates several key signaling cascades:

- **PI3K/AKT Pathway**: MTHFD2 expression is positively correlated with PI3K/AKT pathway activation. In hepatocellular carcinoma and bladder cancer, knockdown of MTHFD2 leads to decreased phosphorylation of AKT, inhibiting cell proliferation and enhancing chemosensitivity.
- **ERK/MAPK Pathway**: In nasopharyngeal carcinoma and lung adenocarcinoma, MTHFD2 promotes cell proliferation and migration through activation of the ERK signaling pathway.
- **mTOR Pathway**: MTHFD2 is a downstream target of the ATF4-MTHFD2 axis, which is inhibited by mTOR blockade. Combining mTOR inhibitors with pan-RAF-MEK inhibitors synergistically suppresses tumor growth by targeting this pathway.
- **Notch Signaling**: In retinoblastoma, MTHFD2 drives tumor progression via activation of the Notch signaling pathway, suggesting a novel role in developmental and oncogenic signaling crosstalk.
- **p53 Pathway**: MTHFD2-mediated m⁶A modification of IFRD1 leads to HDAC3 activation, which in turn deacetylates and stabilizes p53. However, this also activates mTOR, creating a complex regulatory loop that ultimately promotes cell proliferation.

### 3.6 MTHFD2 in Immune Evasion and the Tumor Microenvironment

MTHFD2 plays a critical role in sculpting the tumor immune microenvironment. Shang et al. (2021) demonstrated that MTHFD2 upregulates the expression of PD-L1 (CD274) on cancer cells, enabling them to evade T-cell-mediated killing. This effect is mediated through the metabolic activity of MTHFD2, which alters the cellular pool of metabolites that serve as co-factors for epigenetic enzymes, leading to changes in the methylation status of the PD-L1 promoter. High MTHFD2 expression is associated with an "inflamed" tumor microenvironment, characterized by increased infiltration of CD8⁺ T cells but also higher expression of immune checkpoints, predicting a better response to immunotherapy in some cancers (e.g., bladder cancer). In head and neck squamous cell carcinoma (HNSCC), MTHFD2 expression correlates with immune infiltration and is a prognostic biomarker.

```mermaid
flowchart TD
    subgraph "Metabolic Functions"
        A["Serine"] --> B["SHMT2"]
        B --> C["5,10-methylene-THF"]
        C --> D["MTHFD2 Dehydrogenase"]
        D --> E["5,10-methenyl-THF"]
        E --> F["MTHFD2 Cyclohydrolase"]
        F --> G["10-formyl-THF"]
        G --> H["Purine Biosynthesis"]
        D --> I["NADPH"]
        I --> J["Redox Homeostasis"]
    end

    subgraph "Non-Metabolic Functions"
        K["Nuclear MTHFD2"] --> L["Centromere Integrity"]
        L --> M["Accurate Mitosis"]
        K --> N["m6A RNA Methylation"]
        N --> O["IFRD1 mRNA degradation"]
        O --> P["HDAC3/p53/mTOR pathway"]
        K --> Q["PD-L1 upregulation"]
        Q --> R["Immune Evasion"]
    end

    subgraph "Regulation"
        S["ATF4"] --> T["MTHFD2 Transcription"]
        U["MYC"] --> T
        V["miRNAs"] --> W["MTHFD2 mRNA"]
        W --> X["MTHFD2 Protein"]
        Y["SIRT5"] --> X
        Z["HSPD1"] --> X
    end

    X --> D
    X --> K
```

---

## 4. Pathogenic Hotspot Mutations & Clinical Differentials

### 4.1 Germline Mutations and Congenital Disorders

Unlike some metabolic genes, germline loss-of-function mutations in *MTHFD2* are not commonly associated with a classic Mendelian disorder in humans. This is likely due to the critical role of MTHFD2 during embryonic development. Studies in mice have shown that *Mthfd2* knockout is embryonic lethal, with embryos failing to develop past mid-gestation due to neural tube defects and impaired hematopoiesis. This suggests that complete loss of MTHFD2 function is incompatible with life, and only hypomorphic or tissue-specific mutations may be tolerated.

However, single nucleotide polymorphisms (SNPs) in *MTHFD2* have been associated with complex disease risk:

- **Congenital Heart Disease (CHD)**: Several studies have investigated the association between maternal and offspring *MTHFD2* gene polymorphisms and the risk of CHD. Chen et al. (2022) and Liu et al. (2023) identified specific SNPs (e.g., rs1127714, rs2281603) in *MTHFD2* that, when combined with maternal folic acid supplementation status, modulate the risk of CHD in offspring. These findings highlight the gene-environment interaction between folate metabolism and dietary intake in congenital malformations.
- **Neural Tube Defects (NTDs)**: Given the role of folate metabolism in neural tube closure, polymorphisms in *MTHFD2* have been investigated as risk factors for NTDs, although conclusive evidence is still lacking.

### 4.2 Somatic Mutations in Cancer

While *MTHFD2* is not a classic oncogene with recurrent activating mutations, somatic alterations, including copy number amplifications and overexpression, are common in cancer. The Cancer Genome Atlas (TCGA) data reveals that *MTHFD2* is amplified in a subset of tumors, particularly in lung adenocarcinoma, breast cancer, and ovarian cancer. These amplifications drive high levels of MTHFD2 expression, contributing to the metabolic and non-metabolic phenotypes described earlier.

Specific somatic mutations in the coding region of *MTHFD2* are rare but have been cataloged in COSMIC. Most are missense mutations of unknown functional significance. However, some mutations have been shown to affect enzyme activity or protein stability:

- **R175C**: A recurrent mutation in the NADP⁺-binding domain. Structural modeling suggests that this mutation disrupts cofactor binding, reducing dehydrogenase activity. Tumors with this mutation may be more reliant on MTHFD2L for mitochondrial 1C metabolism.
- **D284N**: Located in the cyclohydrolase domain. This mutation is predicted to be deleterious, potentially abrogating the cyclohydrolase activity.

The clinical significance of these rare somatic mutations is an area of ongoing research. It is hypothesized that they may represent "passenger" mutations that do not drive tumorigenesis but rather reflect genomic instability.

### 4.3 MTHFD2 as a Prognostic and Predictive Biomarker

Across multiple cancer types, high MTHFD2 expression is consistently associated with poor prognosis, including reduced overall survival (OS) and disease-free survival (DFS). This has been demonstrated in:

- **Non-Small Cell Lung Cancer (NSCLC)**: High MTHFD2 expression is an independent predictor of poor prognosis.
- **Breast Cancer**: MTHFD2 is overexpressed and promotes proliferation via AKT signaling. It is also a prognostic biomarker and regulator of ferroptosis in triple-negative breast cancer (TNBC).
- **Acute Myeloid Leukemia (AML)**: MTHFD2 is a selective metabolic vulnerability, and its high expression is associated with resistance to venetoclax.
- **Glioblastoma (GBM)**: MTHFD2 is associated with mitochondrial dysregulation and macrophage heterogeneity, and its expression correlates with poor survival.
- **Renal Cell Carcinoma (RCC)**: MTHFD2 expression correlates with tumor aggressiveness and may serve as a prognostic biomarker.
- **Head and Neck Squamous Cell Carcinoma (HNSCC)**: MTHFD2 is overexpressed and correlated with poor prognosis.
- **Bladder Cancer**: MTHFD2 is a potential oncogene, associated with poor prognosis and high levels of immune infiltrates.
- **Colorectal Cancer (CRC)**: MTHFD2 promotes proliferation and migration.
- **Hepatocellular Carcinoma (HCC)**: MTHFD2 knockdown inhibits proliferation and enhances chemosensitivity.
- **Prostate Cancer**: MTHFD2 is involved in the progression to castration-resistant prostate cancer (CRPC).
- **Endometrial Carcinoma**: MTHFD2 is upregulated and associated with tumor immune infiltration.
- **Esophageal Carcinoma**: MTHFD2 is a novel prognosis biomarker.

### 4.4 MTHFD2 in Non-Cancer Pathologies

Beyond oncology, MTHFD2 has been implicated in several other disease states:

- **Sepsis-Induced Acute Kidney Injury (AKI)**: MTHFD2 stabilizes LOX expression through RNA methylation, promoting AKI progression. Multi-omics analysis suggests that targeting MTHFD2 could improve sepsis prognosis.
- **Heart Failure with Preserved Ejection Fraction (HFpEF)**: Mitochondrial-related gene biomarkers, including MTHFD2, have been identified as potential diagnostic and therapeutic targets.
- **Atherosclerosis**: Oxidized phospholipids (oxPAPC) regulate amino acid metabolism through MTHFD2 to facilitate nucleotide release in endothelial cells, linking MTHFD2 to endothelial dysfunction and atherosclerosis.
- **Tuberculosis (TB)**: Host circulating immunometabolism-associated biomarkers, including MTHFD2, have been identified for the early diagnosis of active TB.
- **Abdominal Aortic Aneurysm (AAA)**: MTHFD2 is part of a NETosis-mediated gene signature associated with AAA.

---

## 5. Host-Pathogen & Viral Interactions

### 5.1 Newcastle Disease Virus (NDV)

Newcastle disease virus (NDV), a paramyxovirus, is a promising oncolytic vector for cancer therapy. However, its replication is restricted in normal mammalian cells. Tang et al. (2023) demonstrated that NDV manipulates mitochondrial MTHFD2-mediated nucleotide metabolism to support its replication. The virus induces MTHFD2 expression in infected cells, which provides the necessary nucleotide pool for viral RNA synthesis. This finding reveals a host-pathogen interaction where the virus hijacks the host's 1C metabolism to fuel its own replication. It also suggests that MTHFD2 inhibitors could potentially be used to enhance the safety and efficacy of NDV-based oncolytic virotherapy.

### 5.2 Coronaviruses

Transcriptomic analyses have identified MTHFD2 as a differentially expressed gene in models of coronavirus infection, including SARS-CoV-2. The induction of MTHFD2 may support the high metabolic demand of viral replication and the inflammatory response. While the precise mechanism remains to be fully elucidated, this suggests a potential role for MTHFD2 in the host response to coronaviruses.

### 5.3 Mycobacterium tuberculosis

In the context of *Mycobacterium tuberculosis* (Mtb) infection, host metabolic reprogramming is a hallmark. A multi-omics screening study identified MTHFD2 as part of a circulating immunometabolism-associated biomarker panel for the early diagnosis of active tuberculosis. This suggests that MTHFD2 expression in peripheral blood may reflect the host's metabolic response to Mtb infection and could serve as a diagnostic biomarker.

### 5.4 Human Papillomavirus (HPV)

While not directly studied for MTHFD2, the link between HPV and alterations in host cell metabolism is well-established. Given that MTHFD2 is a target of the MYC transcription factor, which is activated by the HPV E6/E7 oncoproteins, it is plausible that MTHFD2 is upregulated in HPV-positive cancers. This remains an area for future investigation.

---

## 6. Pharmacogenomics, Drug Targets & Small-Molecule Inhibitors

### 6.1 MTHFD2 as a Therapeutic Target

The selective overexpression of MTHFD2 in cancer cells, combined with its low expression in normal adult tissues, makes it an attractive target for cancer therapy. Inhibiting MTHFD2 is expected to:

- Deprive cancer cells of the NADPH required for redox homeostasis, leading to ROS-induced cell death.
- Reduce the availability of 10-formyl-THF for purine biosynthesis, impairing DNA replication and cell division.
- Disrupt the non-canonical nuclear functions of MTHFD2, such as mitosis and RNA modification.

### 6.2 Small-Molecule Inhibitors

Several classes of small-molecule inhibitors targeting MTHFD2 have been developed:

- **Substrate-Competitive Inhibitors**: These compounds mimic the folate substrate and compete for binding at the active site. Examples include:
    - **LY345899**: A potent inhibitor of MTHFD2 with an IC₅₀ in the nanomolar range. It has shown anti-tumor activity in preclinical models of AML and lung cancer.
    - **DS44960156**: Another substrate-competitive inhibitor with good selectivity for MTHFD2 over MTHFD1.
- **Allosteric Inhibitors**: As described in Section 2.3, xanthine derivatives bind to an allosteric site at the dimer interface, offering a new mode of inhibition. These compounds have the advantage of not competing with the high intracellular concentrations of folate cofactors.
- **NADP⁺-Competitive Inhibitors**: Compounds that compete with the NADP⁺ cofactor. These are less common due to the difficulty in achieving selectivity over other NADP⁺-dependent enzymes.

### 6.3 Drug Repurposing and Combinatorial Strategies

- **Pemetrexed**: Pemetrexed is an antifolate chemotherapy drug that inhibits thymidylate synthase (TS), dihydrofolate reductase (DHFR), and glycinamide ribonucleotide formyltransferase (GARFT). MTHFD2 expression has been identified as a marker of pemetrexed resistance in pulmonary adenocarcinoma. Combining pemetrexed with an MTHFD2 inhibitor has shown synergistic therapeutic advantages in lung adenocarcinoma. Similarly, circMTHFD2 mediates pemetrexed resistance in gastric cancer.
- **Venetoclax**: In AML, MTHFD2 supports mitochondrial redox homeostasis and confers resistance to venetoclax, a BCL-2 inhibitor. Targeting MTHFD2 in combination with venetoclax may overcome this resistance.
- **mTOR Inhibitors**: Inhibition of mTOR enhances the antitumor efficacy of pan-RAF-MEK blockade by inhibiting the ATF4-MTHFD2 pathway.
- **Combinatorial Targeting of MTHFD2 and PAICS**: In MYCN-amplified neuroblastoma, combinatorial targeting of MTHFD2 and PAICS (a purine biosynthesis enzyme) has been proposed as a novel therapeutic strategy.

### 6.4 Pharmacogenomics

The pharmacogenomics of MTHFD2 is primarily related to its role in folate metabolism and the response to antifolate drugs. Genetic variants in MTHFD2 may influence the efficacy and toxicity of drugs like methotrexate and pemetrexed. For example, SNPs that reduce MTHFD2 activity might increase the sensitivity of cancer cells to antifolates, while high-expression variants might confer resistance. Studies are ongoing to validate these associations in clinical cohorts.

### 6.5 Gene Therapy and Other Approaches

While no gene therapy vectors targeting MTHFD2 are currently in clinical trials, the use of RNA interference (RNAi) and antisense oligonucleotides (ASOs) to knockdown MTHFD2 expression has been extensively validated in preclinical models. High-throughput RNAi screening has identified MTHFD2 as a regulator of breast cancer cell migration and invasion. These approaches may be developed as therapeutic modalities in the future.

---

## 7. Bioinformatic Resources & Database Accessions

The following table provides key database accessions and resources for MTHFD2.

| **Database** | **Identifier / Accession** | **Resource Link** |
| :--- | :--- | :--- |
| **HGNC** | HGNC:7434 | [https://www.genenames.org/data/gene-symbol-report/#!/hgnc_id/HGNC:7434](https://www.genenames.org/data/gene-symbol-report/#!/hgnc_id/HGNC:7434) |
| **NCBI Gene** | 10797 | [https://www.ncbi.nlm.nih.gov/gene/10797](https://www.ncbi.nlm.nih.gov/gene/10797) |
| **Ensembl** | ENSG00000119865 | [https://www.ensembl.org/Homo_sapiens/Gene/Summary?db=core;g=ENSG00000119865](https://www.ensembl.org/Homo_sapiens/Gene/Summary?db=core;g=ENSG00000119865) |
| **UniProt** | P13995 | [https://www.uniprot.org/uniprotkb/P13995/entry](https://www.uniprot.org/uniprotkb/P13995/entry) |
| **RCSB PDB** | 7DNG (and others) | [https://www.rcsb.org/structure/7DNG](https://www.rcsb.org/structure/7DNG) |
| **OMIM** | 604887 | [https://www.omim.org/entry/604887](https://www.omim.org/entry/604887) |
| **ClinVar** | Gene: MTHFD2 | [https://www.ncbi.nlm.nih.gov/clinvar/?term=MTHFD2%5Bgene%5D](https://www.ncbi.nlm.nih.gov/clinvar/?term=MTHFD2%5Bgene%5D) |
| **COSMIC** | Gene: MTHFD2 | [https://cancer.sanger.ac.uk/cosmic/gene/analysis?ln=MTHFD2](https://cancer.sanger.ac.uk/cosmic/gene/analysis?ln=MTHFD2) |
| **STRING** | P13995 | [https://string-db.org/network/9606.ENSP00000239263](https://string-db.org/network/9606.ENSP00000239263) |
| **BioGRID** | 112630 | [https://thebiogrid.org/112630](https://thebiogrid.org/112630) |
| **Gene Ontology (GO)** | GO:0004486 (methylenetetrahydrofolate dehydrogenase (

## Related Clinical & Scientific Guides

* [SYNGR1 Gene: Structure, Function, and Clinical Significance](/knowledge/bioinformatics/genes/neuroscience-genetics/syngr1-gene-structure-function-pathway)
* [RGS12 Gene: Structure, Function, and Clinical Significance](/knowledge/bioinformatics/genes/neuroscience-genetics/rgs12-gene-structure-function-pathway)
* [CHRNB1 Gene: Structure, Function, and Clinical Significance](/knowledge/bioinformatics/genes/neuroscience-genetics/chrnb1-gene-structure-function-pathway)