PTGR1 Antibody

What is PTGR1 and why is it important in biological research?

PTGR1 (Prostaglandin Reductase 1) is an NAD(P)H-dependent oxidoreductase involved in the metabolic inactivation of pro- and anti-inflammatory eicosanoids including prostaglandins, leukotrienes, and lipoxins. It catalyzes with high efficiency the reduction of the 13,14 double bond of 15-oxoPGs and with lower efficiency the oxidation of the hydroxyl group at C12 of LTB4 derivatives . PTGR1 has emerged as a significant biomarker in several cancer types and plays a crucial role in activating certain anticancer compounds, particularly acylfulvens .

What approaches are available for detecting PTGR1 expression in experimental systems?

PTGR1 expression can be assessed through multiple complementary techniques:

For clinical applications, IHC has been established as the most practical, reproducible, and cost-effective approach using commercially available antibodies .

Which antibody has demonstrated optimal performance for PTGR1 detection in research settings?

The Abcam AB181131 antibody (rabbit recombinant monoclonal) has been rigorously validated and shown to be the most reliable for PTGR1 detection, particularly in IHC applications. In comparative studies, this antibody demonstrated clear, specific staining patterns in validation tissues with known PTGR1 expression patterns (liver and small intestine as positive controls; pancreas, tonsils, and smooth muscle as negative controls) . For western blot applications, AB181131 successfully detects PTGR1 at the predicted band size of 35 kDa, though observed bands typically appear at 36-38 kDa .

How should researchers validate PTGR1 antibody specificity for their experimental systems?

Comprehensive antibody validation requires a multi-tiered approach:

• Tissue expression control panel: Include tissues with established PTGR1 expression patterns:

  • High expression: Liver, small intestine

  • Low/negative expression: Pancreas, tonsils, smooth muscle

• Cellular models: The A498 kidney cancer cell line shows moderate PTGR1 expression and sensitivity to PTGR1-activated compounds

• Genetic controls: Use PTGR1 knockout cell lines (e.g., PTGR1 knockout HeLa cells) alongside wild-type counterparts to confirm antibody specificity

• Multiple detection methods: Correlate results between IHC, western blot, and RNA expression data to ensure consistency

• Dilution optimization: For AB181131, optimal dilutions are typically 1:1000 for IHC and 1:1000-1:2000 for western blot applications

What is the optimal protocol for PTGR1 immunohistochemistry in tissue samples?

Based on validation studies, the following protocol has demonstrated reliable PTGR1 detection:

• Antibody selection: Use Abcam AB181131 at 1:1000 dilution

• Staining assessment: Score cytoplasmic PTGR1 staining intensity semi-quantitatively:

  • 0: Negative cytoplasmic immunoreactivity

  • 1: Weak positive cytoplasmic immunoreactivity

  • 2: Moderate positive cytoplasmic immunoreactivity

  • 3: Strong positive cytoplasmic immunoreactivity

• Evaluation standards: Have multiple independent assessors score samples in a blinded fashion

• Statistical validation: Calculate inter-rater reliability using Fleiss's kappa coefficient and intra-rater reliability using Cohen's kappa between matched cores

A positive score is typically defined as a mean score of one or above, indicating the presence of PTGR1 protein in the tissue .

How can researchers establish meaningful correlations between PTGR1 RNA and protein expression?

To establish clinically relevant RNA expression cutoffs that correlate with protein expression:

In urothelial carcinoma research, a normalized PTGR1 RNA cutoff at 2,550 normalized counts achieved an AUC of 0.9, with 96% sensitivity and 85% specificity in relation to IHC positivity .

PTGR1 in Cancer Research Applications

PTGR1 influences therapeutic responses in two critical ways:

• Drug resistance mechanism: In prostate cancer models, increased PTGR1 expression significantly attenuates metformin efficacy in both DU145 and 22RV1 cells. Conversely, downregulation of PTGR1 in metformin-resistant cells enhances drug effectiveness .

• Drug activation role: PTGR1 is essential for activating acylfulvens (including LP-184), a promising class of compounds for treating specific cancer subtypes. The cytotoxicity of LP-184 is solely dependent on PTGR1, with PTGR1-null cells showing complete resistance to the compound even at high concentrations .

This dual role makes PTGR1 both a potential resistance biomarker and a predictive biomarker for specific therapeutic approaches.

What experimental approaches effectively study PTGR1 function in cancer cell models?

Research on PTGR1 function has employed several robust methodological approaches:

• Genetic modulation systems:

  • RNA interference: shRNA or siRNA-mediated PTGR1 knockdown to assess loss-of-function effects

  • Lentiviral transduction: Establishing stable PTGR1-overexpressing cell lines to study gain-of-function effects

• Drug resistance models:

  • Generate resistant cell lines through chronic exposure to increasing drug concentrations (e.g., DU145-MetR cells)

  • Compare PTGR1 expression between wild-type and resistant cells at mRNA and protein levels

• Functional assays:

  • Cell proliferation: MTT, CCK-8 assays to measure growth inhibition

  • Colony formation: Assess clonogenic capacity

  • Cell cycle analysis: Flow cytometry with PI staining to detect G0/G1 arrest

  • Apoptosis assessment: Annexin V/PI staining, caspase activation assays

• DNA damage assessment:

  • Measurement of pH2AX expression to confirm PTGR1-dependent activation of DNA-damaging compounds

How can PTGR1 expression be utilized as a biomarker for patient stratification in clinical trials?

PTGR1 expression has significant clinical applications for patient selection, particularly for acylfulven-class compounds:

• Biomarker approach: A dual biomarker strategy combining PTGR1 positivity with nucleotide excision repair (NER) pathway defects has been established for identifying patients likely to respond to acylfulvens .

• Patient identification workflow:

  • Perform PTGR1 IHC staining using validated AB181131 antibody

  • Assess NER pathway defects through targeted sequencing (focusing on mutations in ERCC1, ERCC2, ERCC3, ERCC4)

  • Select patients who are both PTGR1-positive and NER-deficient

• Population estimates: In metastatic urothelial carcinoma cohorts, approximately 40% of tumors score positive for PTGR1 by IHC staining, and the combined PTGR1-positive/NER-deficient phenotype occurs in approximately 13% of patients .

For clinical implementation, a standardized approach for PTGR1 assessment has been validated:

• IHC protocol standardization:

  • Antibody: Abcam AB181131 at 1:1000 dilution

  • Scoring system: 0-3 scale for cytoplasmic staining intensity

  • Positive threshold: Mean score ≥1

  • Quality control: Multiple independent assessors with calculated inter-rater reliability

• RNA expression correlation:

  • For centers using RNA-based methods, a normalized PTGR1 RNA cutoff at 2,550 counts has been validated with high sensitivity (96%) and specificity (85%)

• Technical validation:

  • Tissue microarrays (TMAs) with matched cores from each patient sample

  • Cohen's kappa calculations to ensure consistency between cores

  • Integration with targeted genomic panels for comprehensive assessment of NER pathway status

This multi-modal approach provides a robust framework for clinical PTGR1 assessment across different laboratory settings.

What are the current knowledge gaps in understanding PTGR1's role in disease biology?

Despite progress, significant knowledge gaps remain in PTGR1 research:

• Mechanistic understanding: The precise mechanisms by which PTGR1 influences cancer progression remain incompletely understood, particularly the seemingly contradictory findings that PTGR1 knockdown inhibits proliferation in some cancer models despite its role in inactivating pro-tumorigenic eicosanoids .

• Cancer-type specificity: The basis for the differential prognostic impact of PTGR1 across cancer types requires further investigation to understand context-dependent functions .

• Metabolite profiling: Identification of specific PTGR1 metabolites that may have pro-tumorigenic roles and their mechanisms of action remains an important research frontier .

• Regulatory mechanisms: Recent findings suggest Z-DNA forming sequences (ZFS), including transposable element-derived ZFS, regulate PTGR1 gene expression, and miR-6867-5p can suppress PTGR1 by interacting with ZFS . The implications of these regulatory mechanisms in disease contexts require further study.

What emerging technologies could advance PTGR1 research?

Cutting-edge approaches likely to advance PTGR1 research include:

• Single-cell multi-omics: Integration of single-cell transcriptomics and proteomics to understand cellular heterogeneity in PTGR1 expression and function within tumors

• CRISPR/Cas9 genome editing: Generation of precise PTGR1 knockout and knock-in models to study function in isogenic backgrounds

• Patient-derived organoids: Development of three-dimensional culture systems that better recapitulate tumor physiology for testing PTGR1-targeted therapeutics

• Computational drug design: Structure-based design of specific PTGR1 inhibitors or activators based on detailed understanding of protein function

• Spatial transcriptomics: Analysis of PTGR1 expression in the spatial context of the tumor microenvironment to understand its role in tumor-stroma interactions

How might PTGR1-related research impact precision medicine approaches?

PTGR1 research has several potential implications for precision medicine:

• Therapy selection biomarker: The established role of PTGR1 in acylfulven activation provides a direct application for therapy selection, with ongoing clinical trials implementing PTGR1 testing .

• Resistance mechanism targeting: Understanding PTGR1's role in drug resistance could inform combination strategies to overcome resistance to existing therapies like metformin .

• Cancer subtyping: PTGR1 expression patterns may contribute to molecular classification of tumors, potentially identifying biological subtypes with distinct therapeutic vulnerabilities.

• Novel therapeutic development: The enzymatic activity of PTGR1 makes it an attractive target for small molecule inhibitors, with emerging evidence suggesting PTGR1 inhibition could have therapeutic potential in certain cancer contexts .