DECR2 Human

What is DECR2 and what is its primary cellular function?

DECR2 is a peroxisomal NADPH-dependent auxiliary enzyme that plays a critical role in the β-oxidation of polyunsaturated fatty acids. Located specifically in peroxisomes, DECR2 functions analogously to its mitochondrial counterpart DECR1, but operates in a different cellular compartment. Its primary function is to assist in the degradation of polyunsaturated fatty acids (PUFAs), particularly very long chain fatty acids (VLCFAs, C≥22) .

Unlike mitochondrial β-oxidation, peroxisomal β-oxidation (perFAO) does not directly produce ATP. Instead, peroxisomes function primarily to shorten VLCFAs prior to their transport into mitochondria for complete degradation and energy production. DECR2 specifically catalyzes the reduction of 2,4-dienoyl-CoA intermediates that form during the degradation of unsaturated fatty acids with double bonds at even-numbered positions .

How does DECR2 differ from other fatty acid oxidation enzymes, particularly DECR1?

While DECR1 and DECR2 share functional similarities as NADPH-dependent enzymes involved in unsaturated fatty acid oxidation, they have distinct cellular localizations and substrate preferences:

While examination of DECR2's crystal structure suggests selectivity for VLCFAs like docosahexaenoic acid (DHA), some studies indicate DECR2 may also participate in the degradation of short and medium chain substrates, demonstrating its versatility in fatty acid metabolism .

What metabolic pathways depend on proper DECR2 function?

DECR2 is integral to several lipid metabolism pathways beyond its direct role in perFAO:

• Polyunsaturated fatty acid metabolism: DECR2 is crucial for the degradation of PUFAs such as arachidonic acid and docosahexaenoic acid in peroxisomes .

• Branched-chain amino acid pathways: Transcriptomic analysis of DECR2 knockdown cells reveals significant enrichment in branched-chain amino acid pathways, suggesting DECR2's metabolic influence extends beyond fatty acid oxidation .

• Isoprenoid metabolic processes: DECR2 appears to influence isoprenoid metabolism, which is essential for the synthesis of various biomolecules including cholesterol and steroid hormones .

• Cell cycle regulation: Notably, DECR2 function appears tightly linked to cell cycle progression through mechanisms involving lipid metabolism and phosphorylation of the retinoblastoma (Rb) tumor suppressor protein .

These pathways highlight DECR2's position at the intersection of lipid metabolism and cellular proliferation, explaining its importance in both normal cellular function and disease states.

How is DECR2 expression altered in prostate cancer progression?

DECR2 exhibits a notable expression pattern across prostate cancer progression, with significant implications for disease monitoring and therapeutic targeting:

Analysis of multiple clinical prostate cancer datasets (Taylor, Grasso, Tomlin, and Beltran cohorts) reveals that DECR2 is consistently upregulated in malignant prostate tissues compared to benign tissues. Most notably, DECR2 expression is significantly higher in metastatic prostate cancer tissues compared to primary tumors .

Key findings include:

• DECR2 gene copy number gain is evident across several clinical prostate cancer datasets

• Higher DECR2 levels significantly correlate with biochemical recurrence in metastatic castrate-resistant prostate cancer (CRPC) patients

• DECR2 protein expression is particularly elevated in castrate-resistant and enzalutamide-resistant prostate cancer cell lines

• Immunohistochemistry analysis confirms increased DECR2 expression in malignant prostate cancer tissues compared to benign tissues

This expression pattern makes DECR2 a potential biomarker for disease progression and treatment resistance in prostate cancer. The selective upregulation in advanced disease stages suggests DECR2 may be particularly relevant for understanding and targeting treatment-resistant disease states .

What functional role does DECR2 play in cancer cell proliferation and treatment resistance?

DECR2 exerts multi-faceted effects on cancer cell behavior, particularly in advanced prostate cancer:

Cell Proliferation and Cell Cycle Control:

• DECR2 knockdown significantly arrests the cell cycle at the G1 phase

• Transcriptomic analysis of DECR2-depleted cells shows downregulation of cell cycle-related pathways

• DECR2 knockdown decreases phosphorylated retinoblastoma (pRb) tumor suppressor protein levels

• High DECR2 expression accelerates cell cycle progression

Treatment Resistance Mechanisms:

These findings establish DECR2 as a critical mediator linking peroxisomal lipid metabolism to cell cycle progression and treatment resistance in prostate cancer, suggesting its potential as a therapeutic target, particularly for advanced, treatment-resistant disease.

What are the therapeutic implications of targeting DECR2 in cancer treatment?

Emerging research highlights DECR2 as a promising therapeutic target, particularly for treatment-resistant cancers:

Preclinical Evidence:

• Depletion of DECR2 significantly suppresses proliferation, migration, and 3D growth of a range of castrate-resistant and enzalutamide-resistant prostate cancer cell lines

• DECR2 inhibition reduces tumor growth and proliferation in vivo

• Targeting peroxisomal fatty acid oxidation through either DECR2 knockdown or pharmacological means (like thioridazine) further attenuates viability and colony formation in combination with enzalutamide compared to either approach alone

Therapeutic Strategies:

• Combination Therapy: DECR2 inhibition shows particular promise in combination with standard androgen receptor pathway inhibitors, potentially overcoming treatment resistance.

• Metabolic Targeting: Unlike approaches targeting mitochondrial β-oxidation, peroxisomal β-oxidation inhibition through DECR2 represents a novel metabolic vulnerability in cancer cells.

• Patient Stratification: High DECR2 expression correlates with biochemical recurrence and poorer survival, suggesting potential utility as a biomarker for patient selection.

Currently, no specific inhibitors of peroxisomal β-oxidation or DECR2 exist for clinical use, representing an important gap for future drug development efforts. The development of such inhibitors could provide new therapeutic options for patients with treatment-resistant prostate cancer .

What are the recommended approaches for studying DECR2 expression and localization?

Multiple complementary techniques are recommended for comprehensive analysis of DECR2 expression and localization:

For Gene Expression Analysis:

• RT-qPCR for quantitative assessment of DECR2 mRNA levels

• Analysis of public transcriptomic databases (such as TCGA, SU2C, and other clinical cohorts)

• RNA sequencing for broader transcriptomic context of DECR2 expression

For Protein Detection:

• Western blotting with validated DECR2-specific antibodies

• Quantitative immunohistochemistry for tissue samples

• Immunocytochemistry for cellular localization studies

For Subcellular Localization:

• Co-immunostaining with peroxisomal markers (such as PEX proteins)

• Subcellular fractionation followed by Western blot analysis

• Live-cell imaging with fluorescently tagged DECR2 constructs

When studying DECR2 localization, it is critical to confirm its peroxisomal localization, as this distinguishes it from its mitochondrial counterpart DECR1. Researchers have successfully employed immunocytochemistry to confirm DECR2's peroxisomal localization, which is essential for validating its functional context .

What genetic manipulation techniques are most effective for DECR2 functional studies?

Several genetic approaches have proven effective for investigating DECR2 function:

For DECR2 Knockdown/Silencing:

• siRNA pools for transient knockdown studies (utilized successfully in prostate cancer cell lines)

• shRNA for stable knockdown models

• CRISPR-Cas9 genome editing for complete knockout models

For DECR2 Overexpression:

• Stable overexpression systems using lentiviral or retroviral vectors

• Inducible expression systems to control timing and level of expression

• Tagged expression constructs (e.g., with FLAG or GFP) for tracking protein localization and interaction studies

Validation Approaches:

• Western blotting to confirm successful knockdown or overexpression

• Functional assays to verify altered peroxisomal β-oxidation activity

• Rescue experiments to confirm phenotype specificity

In published studies, researchers have successfully employed pooled siRNA-mediated knockdown of DECR2 to identify over 8,000 genes that were significantly differentially expressed, highlighting the broad impact of DECR2 on cellular transcriptional programs. Similarly, stable overexpression of DECR2 has been established in LNCaP cells to study its effects on treatment resistance .

How can researchers effectively measure peroxisomal β-oxidation activity in the context of DECR2 studies?

Assessing peroxisomal β-oxidation (perFAO) activity, particularly in relation to DECR2 function, requires specialized techniques:

Direct Enzymatic Activity Assays:

• Spectrophotometric assays measuring NADPH consumption during DECR2-catalyzed reactions

• Radio-labeled substrate utilization assays using specific DECR2 substrates like labeled polyunsaturated fatty acids

• Peroxisomal isolation followed by oxidation rate measurements with specific substrates

Indirect Activity Assessment:

• Pharmacological Approach: Treatment with peroxisomal β-oxidation inhibitors like thioridazine (TDZ), with activity validation by:

  • Comparing effects in DECR2 overexpressing vs. knockdown cells

  • Measuring cellular consequences like viability and proliferation

• Metabolic Profiling:

  • Lipidomics analysis to assess changes in lipid composition and abundance

  • Targeted analysis of peroxisomal β-oxidation products

  • Changes in levels of very long chain fatty acids and polyunsaturated fatty acids

• Functional Readouts:

  • Changes in peroxisome morphology and abundance

  • Cell viability under conditions requiring peroxisomal function

  • Resistance to treatment with agents like enzalutamide

Research shows that overexpression of DECR2 markedly increases susceptibility of cells to perFAO inhibitors like TDZ, while TDZ has minimal effect on DECR2 knockdown cells, providing a useful functional validation approach .

How does DECR2 influence the cellular lipidome, and what are the implications for cancer metabolism?

DECR2 exerts profound effects on cellular lipid composition with significant implications for cancer metabolism:

Lipidomic Alterations in DECR2 Manipulation:

Functional Implications:

• Membrane Structure and Function: LION enrichment analysis shows DECR2 manipulation affects lipids associated with plasma membrane, endosomes/lysosomes, mitochondria, and endoplasmic reticulum, potentially altering membrane properties and function.

• Signaling Pathways: Changes in lipid-mediated signaling molecules, especially those derived from polyunsaturated fatty acids like arachidonic acid.

• Energy Storage: Altered triacylglyceride levels suggest changes in cellular energy storage capacity.

• Cell Cycle Regulation: Koberlin et al. demonstrated that different lipid states can predict functional phenotypes in membrane-dependent processes like cell division and proliferation, linking DECR2's effect on the lipidome to its impact on cell cycle progression .

These findings suggest DECR2's role in cancer extends beyond simple fatty acid oxidation to include comprehensive reprogramming of cellular lipid metabolism, which may be exploited for both diagnostic and therapeutic purposes.

What is the relationship between DECR2 and androgen receptor signaling in prostate cancer?

The relationship between DECR2 and androgen receptor (AR) signaling represents a critical area for advanced prostate cancer research:

Clinical Observations:

• DECR2 is markedly upregulated in castrate-resistant prostate cancer (CRPC) and enzalutamide-resistant prostate cancer

• High DECR2 levels are significantly associated with biochemical recurrence and poorer survival in CRPC patients

• Proteomic analysis shows that peroxisomal genes, including DECR2, are strongly associated with acquired resistance to AR inhibitors like enzalutamide and apalutamide

Mechanistic Relationships:

• Resistance Mechanisms:

  • DECR2 overexpression significantly increases viability of prostate cancer cells under androgen-depleted conditions

  • DECR2 overexpression confers resistance to AR inhibitors enzalutamide and apalutamide

  • Combination of DECR2 inhibition with AR inhibitors shows enhanced efficacy compared to either approach alone

• Potential Cross-talk:

  • Peroxisomes are involved in the synthesis of certain lipid molecules that may influence AR signaling

  • DECR2's effect on the lipidome may alter membrane properties and AR localization or function

  • Altered lipid-mediated signaling pathways might interact with AR-dependent transcriptional programs

• Therapeutic Implications:

  • DECR2 inhibition may re-sensitize resistant cells to AR-targeted therapies

  • Combination of peroxisomal β-oxidation inhibitors with AR inhibitors represents a promising therapeutic strategy

  • Monitoring DECR2 expression may help predict response to AR-targeted therapies

These findings position DECR2 as an important mediator of treatment resistance in advanced prostate cancer and suggest that targeting DECR2/perFAO may be particularly effective in combination with standard-of-care AR pathway inhibition.

What are the emerging research questions regarding DECR2's role in other cancer types and diseases?

While DECR2 has been primarily studied in prostate cancer, several emerging questions highlight its potential broader significance:

DECR2 in Other Cancer Types:

• Comparative Expression Analysis: Does DECR2 show similar upregulation patterns in other hormone-dependent cancers like breast and ovarian cancer?

• Metabolic Dependencies: Do cancer types with distinct metabolic profiles (e.g., glycolytic vs. oxidative) show different dependencies on DECR2 function?

• Tumor Microenvironment Interactions: How does DECR2 function in cancer cells influence the metabolic crosstalk with surrounding stromal and immune cells?

DECR2 in Non-Cancer Diseases:

• Metabolic Disorders: Given its role in fatty acid metabolism, what is DECR2's contribution to conditions like non-alcoholic fatty liver disease or metabolic syndrome?

• Inflammatory Conditions: Since peroxisomal function affects the synthesis of inflammatory mediators, how might DECR2 influence inflammatory diseases?

• Neurodegenerative Diseases: Considering the importance of peroxisomal function in brain health, could DECR2 dysfunction contribute to neurodegenerative conditions?

Methodological Frontiers:

• Development of Specific Inhibitors: Currently, no specific inhibitors of perFAO or DECR2 exist. How can we develop highly specific pharmacological tools to target DECR2?

• In Vivo Models: What are the systemic effects of DECR2 modulation in complex organismal models?

• Biomarker Potential: Can DECR2 expression or associated lipid profiles serve as biomarkers for disease stratification or treatment response prediction?

Recent research in colon cancer cells has begun to characterize lipidomic changes associated with DECR2 knockout, suggesting the enzyme's relevance beyond prostate cancer . These emerging questions highlight the need for expanded investigation of DECR2's roles across diverse physiological and pathological contexts.

How can researchers effectively integrate transcriptomic and lipidomic analyses in DECR2 studies?

Integrated multi-omics approaches provide powerful insights into DECR2 function and can be implemented through the following methodological framework:

Experimental Design for Multi-omics Integration:

• Paired Sample Collection: Ensure transcriptomic and lipidomic analyses are performed on the same biological samples to enable direct correlation.

• Time-course Experiments: Consider temporal dynamics by collecting samples at multiple timepoints after DECR2 manipulation.

• Inclusion of Key Controls:

  • Wild-type/untreated controls

  • Scrambled siRNA/empty vector controls for genetic manipulation

  • Rescue experiments (re-expression of DECR2 in knockdown cells)

Analytical Approaches:

• Correlation Analysis: Direct correlation between differentially expressed genes and altered lipid species.

• Pathway Enrichment: Tools like Gene Set Enrichment Analysis (GSEA) for transcriptomics paired with Lipid Ontology (LION) enrichment analysis for lipidomics.

• Network Analysis: Construction of integrated gene-lipid networks to identify key regulatory nodes.

• Machine Learning Approaches: Supervised and unsupervised learning methods to identify patterns across datasets.

Validation Strategies:

• Functional validation of identified pathways using specific inhibitors or genetic manipulation

• Targeted lipidomic analysis of specific lipid species identified through global profiling

• Orthogonal techniques (e.g., immunoblotting, enzymatic assays) to validate key findings

Previous research has successfully employed this integrative approach, revealing that DECR2 knockdown significantly alters both the transcriptome (>8,000 differentially expressed genes) and the lipidome, with enrichment in pathways related to cell cycle regulation and lipid metabolism .

What considerations are important when developing models to study DECR2 in treatment resistance?

Developing robust models to study DECR2's role in treatment resistance requires careful attention to several key experimental factors:

Model Selection and Development:

• Cell Line Models:

  • Use of paired sensitive/resistant cell lines (e.g., LNCaP vs. enzalutamide-resistant MR49F)

  • Development of isogenic resistant models through long-term drug exposure

  • DECR2 overexpression in sensitive lines to test sufficiency for resistance induction

• Three-dimensional Models:

  • Spheroid cultures that better recapitulate in vivo conditions

  • Organoid models derived from patient samples

  • Co-culture systems incorporating tumor microenvironment components

• In Vivo Models:

  • Xenograft models with modulated DECR2 expression

  • Treatment regimens that mimic clinical protocols

  • Patient-derived xenografts from treatment-resistant tumors

Key Experimental Controls and Parameters:

• Resistance Verification:

  • Dose-response curves to confirm resistance phenotype

  • Multiple resistance metrics (viability, proliferation, apoptosis)

  • Molecular markers of resistance mechanisms

• DECR2 Manipulation Timing:

  • Manipulation before resistance development (preventive approach)

  • Manipulation after resistance establishment (therapeutic approach)

  • Temporal monitoring of DECR2 expression during resistance development

• Combination Approaches:

  • Testing DECR2 targeting in combination with standard therapies

  • Varied sequence of treatments (concurrent vs. sequential)

  • Dose optimization for combination strategies

Published research has demonstrated the value of these considerations, showing that DECR2 depletion or pharmacological targeting of peroxisomal β-oxidation can increase sensitivity of CRPC and enzalutamide-resistant PCa cells to enzalutamide, suggesting re-sensitization to treatment .

What are the current technical challenges in targeting DECR2 for therapeutic purposes?

Several technical challenges must be addressed to advance DECR2-targeted therapies toward clinical application:

Inhibitor Development Challenges:

• Specificity Concerns:

  • Distinguishing between DECR2 and its mitochondrial counterpart DECR1

  • Avoiding off-target effects on other peroxisomal enzymes

  • Maintaining selectivity across diverse tissue types

• Structural Considerations:

  • Limited structural information about human DECR2 in physiological conditions

  • Understanding substrate binding dynamics for rational drug design

  • Identifying allosteric sites for potential regulation

• Delivery Challenges:

  • Ensuring drug access to peroxisomes across cellular membranes

  • Developing targeted delivery systems for cancer-specific action

  • Achieving sufficient exposure in relevant tissues

Biomarker Development Needs:

• Patient Selection Markers:

  • Validation of DECR2 expression as a predictive biomarker for response

  • Development of companion diagnostics for DECR2-targeted therapies

  • Identification of additional markers for combination therapies

• Response Monitoring:

  • Methods to assess peroxisomal β-oxidation inhibition in vivo

  • Non-invasive approaches to monitor treatment efficacy

  • Lipid biomarkers that reflect DECR2 inhibition

Resistance Mechanisms:

• Pathway Redundancy:

  • Alternative fatty acid oxidation pathways that might compensate for DECR2 inhibition

  • Metabolic flexibility allowing cancer cells to utilize other energy sources

  • Potential for acquired resistance through upregulation of compensatory mechanisms

Currently, no specific inhibitors of peroxisomal β-oxidation or DECR2 exist for clinical use. The development of such inhibitors represents an important frontier for translational research in this field, particularly given the promising preclinical results of targeting peroxisomal β-oxidation in treatment-resistant prostate cancer .

How might DECR2 function intersect with emerging concepts in cancer metabolism?

DECR2 research intersects with several cutting-edge areas in cancer metabolism research:

Metabolic Flexibility and Plasticity:

• Investigating how DECR2 contributes to cancer cells' ability to adapt their metabolism in response to treatment pressures

• Exploring how peroxisomal metabolism complements or compensates for changes in mitochondrial function

• Understanding the role of DECR2 in metabolic symbiosis within the tumor microenvironment

Lipid Metabolism Beyond Energy Production:

• Examining how DECR2-mediated changes in the lipidome influence signaling lipids and membrane composition

• Investigating connections between peroxisomal metabolism and lipid droplet dynamics in cancer cells

• Exploring how altered fatty acid composition affects cancer cell membrane properties and drug uptake

Integrative Metabolic Networks:

• Mapping the interactions between peroxisomal β-oxidation and other metabolic pathways like glycolysis and glutaminolysis

• Investigating potential metabolic vulnerabilities created by DECR2 inhibition that could be exploited in combination therapies

• Understanding how DECR2 function intersects with cellular redox balance through NADPH utilization

Therapeutic Implications:

• Developing more precise metabolic targeting strategies that account for peroxisomal functions

• Exploring synthetic lethality approaches combining DECR2 inhibition with other metabolic interventions

• Investigating how peroxisomal metabolism might influence response to emerging therapies like immunotherapy

These research directions highlight the need to consider peroxisomal metabolism, and specifically DECR2 function, within the broader context of cancer cell metabolic networks rather than as an isolated pathway .

What novel experimental approaches could advance our understanding of DECR2 biology?

Several innovative experimental approaches could significantly advance DECR2 research:

Advanced Genetic Engineering Approaches:

• CRISPR-based Screening: Genome-wide or metabolic pathway-focused CRISPR screens to identify synthetic lethal interactions with DECR2 inhibition.

• Inducible Systems: Development of temporally controlled DECR2 expression/inhibition models to study acute versus chronic effects.

• Domain-specific Mutations: Creation of mutant DECR2 proteins with altered catalytic activity or substrate specificity to dissect specific functions.

Single-cell Technologies:

• Single-cell Transcriptomics and Proteomics: Analysis of cell-to-cell variability in DECR2 expression and its correlation with metabolic states.

• Spatial Transcriptomics: Investigation of DECR2 expression patterns within the tumor microenvironment and in relation to specific tumor regions.

• Live-cell Imaging: Development of biosensors for peroxisomal activity to monitor real-time changes in peroxisomal metabolism.

Translational Approaches:

• Patient-derived Models: Expansion of research using patient-derived organoids and xenografts with varied DECR2 expression levels.

• Clinical Sample Analysis: Comprehensive multi-omics analysis of clinical samples stratified by DECR2 expression and treatment response.

• Pharmacological Tool Development: Design of specific small molecule inhibitors or activity-based probes for DECR2 to facilitate detailed functional studies.

Computational Methods:

• Metabolic Flux Analysis: Application of isotope-resolved metabolomics to track carbon flux through peroxisomal pathways.

• Systems Biology Models: Development of computational models integrating peroxisomal metabolism with broader cellular metabolic networks.

• AI-assisted Drug Design: Application of machine learning approaches to identify novel DECR2 inhibitors based on structural and functional data.

These innovative approaches would help address existing knowledge gaps and accelerate the translation of DECR2 research into clinical applications .

What are the key controversies and unresolved questions in DECR2 research?

Several important controversies and unresolved questions persist in the DECR2 research field:

Contradictory Roles in Different Cancer Types:

• While DECR2 appears to promote tumor growth in prostate cancer, its role in other cancer types remains unclear.

• Some studies suggest decreased peroxisomal activity in certain tumor types, while others indicate tumor-promoting functions.

• The tumor-promoting or tumor-suppressing functions of peroxisomes may be dependent on tumor type and disease stage .

Substrate Specificity Debates:

• Although crystal structure analysis suggests DECR2 preferentially acts on very long chain fatty acids like docosahexaenoic acid (DHA), some studies report DECR2 involvement in the degradation of short and medium chain substrates.

• The full range of physiological substrates for DECR2 remains incompletely characterized .

Mechanistic Uncertainties:

• Cell Cycle Regulation: While DECR2 clearly influences cell cycle progression, the precise molecular mechanisms linking peroxisomal metabolism to cell cycle control remain to be fully elucidated.

• Treatment Resistance: The exact pathways by which DECR2 contributes to treatment resistance in prostate cancer require further investigation.

• Transcriptional Control: The factors regulating DECR2 expression, particularly its upregulation in advanced cancer, are not well understood.

Therapeutic Potential Questions:

• Targeting Specificity: Can DECR2 be specifically targeted without affecting other essential peroxisomal functions?

• Resistance Mechanisms: Will cancer cells develop resistance to DECR2 inhibition, and through what mechanisms?

• Patient Selection: What biomarkers beyond DECR2 expression might predict response to peroxisomal β-oxidation targeting?

Physiological Role Uncertainties:

• The normal physiological role of DECR2 in different human tissues remains incompletely characterized.

• The consequences of DECR2 inhibition for normal cells and potential toxicity concerns need further investigation.

• The role of DECR2 in non-cancer contexts, such as metabolic or inflammatory conditions, requires additional research.

Addressing these controversies and unresolved questions will be essential for advancing DECR2 research and realizing its potential as a therapeutic target .