MTAP Antibody Clones Used in Ovarian Carcinoma IHC Research
Based on the available evidence, the most commonly used MTAP antibody clones for immunohistochemistry in research are monoclonal antibodies EPR6893 (Abcam, ab126770) and 1813 (Novus Biologicals, NBP2-75730), though the evidence specifically addresses their use in other carcinomas rather than ovarian carcinoma directly 1.
Key Antibody Performance Data
Clone 1813 (Novus Biologicals, NBP2-75730) demonstrates superior performance characteristics compared to EPR6893 in comparative studies 1:
- Stronger immunoreactivity with more specific cytoplasmic staining
- No equivocal interpretations (0% vs 34% equivocal rate with EPR6893)
- 96% sensitivity and 86% specificity for detecting 9p21 homozygous deletion
- Better internal positive control visualization
- Less nonspecific background staining
EPR6893 (Abcam, ab126770) Limitations
This clone showed significant interpretive challenges 1:
- 34% of cases had equivocal staining patterns
- Weak or heterogeneous immunoreactivity
- Lack of definitive internal positive controls
- Problematic nonspecific background staining
Technical Considerations for MTAP IHC
Staining Pattern and Interpretation
- Cytoplasmic expression is the expected pattern for MTAP 1
- Loss of MTAP serves as a surrogate marker for 9p21 homozygous deletion involving MTAP/CDKN2A genes 1, 2
- Internal positive controls (stromal cells, inflammatory cells, endothelial cells) should retain MTAP expression 1
Tissue Requirements
- Formalin-fixed, paraffin-embedded (FFPE) tissue is standard 1
- MTAP IHC is particularly valuable for low tumor purity samples where molecular testing may be limited 1
Clinical Context for Ovarian Carcinoma
While the provided evidence does not specifically detail MTAP antibody use in ovarian carcinoma research, the general principles apply:
- MTAP loss indicates 9p21 deletion, which has prognostic implications across multiple cancer types 2, 3
- MTAP deficiency creates therapeutic vulnerabilities in the PRMT5/MAT2A pathway, potentially relevant for targeted therapy 2
- Near-perfect agreement (κ = 0.85) exists between MTAP IHC with clone 1813 and molecular 9p21 copy number assessment 1
Practical Recommendation
For ovarian carcinoma research requiring MTAP immunohistochemistry, clone 1813 (Novus Biologicals, NBP2-75730) should be the preferred antibody based on its superior performance characteristics, lack of equivocal interpretations, and high concordance with molecular testing 1. If using EPR6893, be prepared for a substantial rate of equivocal results requiring molecular confirmation.