KRT18 Antibody

What is KRT18 and in which tissues is it primarily expressed?

KRT18, also known as Cytokeratin 18, is a type I (acidic) intermediate filament protein with a molecular weight of approximately 48 kDa. It typically exists in combination with cytokeratin 8 and is primarily expressed in:

• Simple epithelia but not stratified squamous epithelia

• Gastrointestinal tract (positive for both KRT8 and KRT18, negative for KRT14)

• Respiratory tract

• Urogenital tract

• Endocrine and exocrine tissues

• Mesothelial cells

In pathological contexts, KRT18 is present in a majority of adenocarcinomas and ductal carcinomas but not in squamous cell carcinomas. Hepatocellular carcinomas specifically express only keratins 8 and 18 .

What are the major applications for KRT18 antibodies in research?

KRT18 antibodies are utilized across multiple research applications:

KRT18 antibodies are particularly valuable in differential diagnosis of tumors, cytopathology, and flow cytometric assays to distinguish different types of epithelial malignancies .

How should KRT18 antibodies be properly stored and handled?

Proper storage and handling are critical for maintaining antibody integrity:

• Store at -20°C for long-term storage (most preparations remain stable for at least one year when properly stored)

• For short-term storage (less than a month), 2-8°C is acceptable

• Avoid repeated freeze-thaw cycles

• Most KRT18 antibodies are supplied in PBS with either:

  • 0.02-0.09% sodium azide and 50% glycerol (pH 7.3-7.4)

  • Or with BSA as a stabilizer

• Do not freeze antibodies prepared in solutions without cryoprotectants

• Aliquot antibodies upon first thaw to minimize freeze-thaw cycles

What positive controls are recommended for validating KRT18 antibody specificity?

When validating KRT18 antibodies, the following positive controls have been successfully employed:

For negative controls, consider cells/tissues known to lack KRT18 expression such as lymphoid tissues or using isotype control antibodies matched to your primary antibody .

How can I optimize antigen retrieval for KRT18 immunohistochemistry in FFPE tissues?

Optimization of antigen retrieval is crucial for successful KRT18 staining in formalin-fixed paraffin-embedded (FFPE) tissues:

• Heat-induced epitope retrieval (HIER) methods:

  • Primary recommendation: 10mM Tris with 1mM EDTA, pH 9.0, for 45 min at 95°C followed by cooling at room temperature for 20 minutes

  • Alternative method: Citrate buffer (pH 6.0) may be effective for some antibody clones

• Protocol considerations:

  • Incubation time: Typically 30 minutes at room temperature for primary antibody

  • Detection systems: Both polymer and avidin-biotin systems have shown efficacy

  • Counterstaining: Hematoxylin provides good nuclear contrast against cytoplasmic KRT18 staining

• Optimization variables:

  • Antibody dilution (test range from 1:50-1:500)

  • Incubation time and temperature

  • Antigen retrieval duration

What are the key considerations when selecting between monoclonal and polyclonal KRT18 antibodies?

The choice between monoclonal and polyclonal KRT18 antibodies depends on specific research needs:

For critical quantitative applications where reproducibility is essential, monoclonal antibodies are generally preferred. For detection in fixed tissues where epitope availability might be compromised, polyclonal antibodies often provide better sensitivity .

How does KRT18 expression correlate with cancer progression and what methodological approaches are most informative?

KRT18 has significant correlations with cancer progression requiring specific methodological approaches:

These findings suggest KRT18 may serve as an oncogenic biomarker in CRC progression and potentially as a therapeutic target .

What are the optimal approaches for multi-color immunofluorescence using KRT18 antibodies?

Multi-color immunofluorescence with KRT18 requires careful planning:

• Fluorophore selection considerations:

  • CF® dyes offer exceptional brightness and photostability

  • Avoid blue fluorescent dyes (CF®405S, CF®405M) for detecting low-abundance targets due to lower fluorescence and higher non-specific background

  • Optimal fluorophore options:

    • CF®488A (Ex/Em: 490/515nm, detection through GFP/FITC channels)

    • CF®568 (Ex/Em: 562/583nm, detection through RFP/TRITC channels)

    • CF®594 (Ex/Em: 593/614nm, detection through Texas Red® channels)

    • CF®640R (Ex/Em: 642/662nm, detection through far-red channels)

• Co-staining marker recommendations:

  • KRT8 (pairs naturally with KRT18)

  • E-cadherin (documented direct binding partner of KRT18)

  • Epithelial markers (EpCAM, pan-cytokeratin)

  • Tumor markers specific to tissue of interest

• Multiplexing protocol optimization:

  • Sequential staining may be necessary to avoid cross-reactivity

  • Careful antibody selection from different host species

  • Appropriate controls including single-stained samples and fluorescence minus one (FMO) controls

How can KRT18 phosphorylation status impact antibody binding and experimental interpretation?

KRT18 phosphorylation significantly impacts its function and antibody detection:

• Functional implications of phosphorylation:

  • Phosphorylated KRT18 plays important roles in filament reorganization

  • Phosphorylation status changes during cell stress and apoptosis

  • May affect protein-protein interactions, including binding to E-cadherin

• Antibody binding considerations:

  • Standard KRT18 antibodies may have differential affinity for phosphorylated forms

  • Phospho-specific KRT18 antibodies are available for detecting specific modifications

  • Phosphatase treatments prior to immunostaining can help determine the impact of phosphorylation on antibody binding

• Experimental approaches:

  • Use phospho-specific antibodies for studying specific signaling events

  • Combine with western blotting to distinguish differently phosphorylated forms

  • Consider phosphatase inhibitors in lysate preparation for preserving modification state

  • Knockout/knockdown validation experiments to confirm specificity

What role does KRT18 play in trophoblast function and embryo implantation?

Recent research highlights KRT18's crucial role in reproductive biology:

• Expression pattern in embryo development:

  • KRT18 is highly expressed in trophoblast cells at the blastocyst stage

  • Localizes primarily in the cytoplasm

  • Not strongly expressed during earlier embryonic stages

• Functional significance:

  • Knockdown of KRT18 in mouse embryos significantly inhibits embryo adhesion and implantation

  • In vitro experiments show silencing KRT18 disturbs trophoblast migration and invasion

  • KRT18 directly binds to and stabilizes cell surface E-cadherin in trophoblast cells (confirmed through microscale thermophoresis analysis)

• Experimental evidence of KRT18 impact on embryo implantation:

These findings suggest that KRT18 may be a critical factor in regulating trophoblast invasion and adhesion during embryo implantation .

What methodological approaches are optimal for studying KRT18 in embryo and developmental research?

When investigating KRT18 in developmental contexts, specialized techniques are required:

• Embryo-specific techniques:

  • Trophoblast-specific knockdown models using lentiviral delivery

  • Immunofluorescence analysis of preimplantation embryos at different stages

  • F-actin architecture visualization with phalloidin staining alongside KRT18

  • In vitro embryo adhesion assays to functional impact

• Protein interaction studies:

  • Microscale thermophoresis (MST) analysis for direct binding studies

  • Co-immunoprecipitation to confirm protein-protein interactions

  • Proximity ligation assays for in situ interaction detection

  • Stability assays to assess the impact on partner proteins (e.g., E-cadherin)

• Embryo transfer and implantation studies:

  • Lentiviral modification of embryos followed by transfer to pseudopregnant recipients

  • Quantification of implantation sites

  • Histological analysis of implantation sites

How can KRT18 antibodies be utilized for circulating tumor cell detection and liquid biopsy applications?

KRT18 antibodies offer promising applications in liquid biopsy approaches:

• Circulating tumor cell (CTC) detection:

  • KRT18 is a characteristic marker of epithelial-derived CTCs

  • Can be used in multi-marker panels alongside other epithelial markers

  • Flow cytometry and immunomagnetic separation techniques have employed KRT18 antibodies

• Methodological considerations:

  • Cell surface accessibility is limited (KRT18 is intracellular)

  • Requires permeabilization protocols for detection

  • Best used in combination with other markers for improved specificity

  • Flow cytometry offers quantitative assessment of KRT18-positive cells

• Experimental approach recommendations:

  • Combined surface marker (EpCAM) and intracellular KRT18 staining

  • Multi-parameter flow cytometry with appropriate gating strategies

  • Confirmation of epithelial origin through multiple marker characterization

What are the latest findings regarding post-translational modifications of KRT18 and their detection using specialized antibodies?

Post-translational modifications (PTMs) of KRT18 provide important insights into cellular processes:

• Key KRT18 post-translational modifications:

  • Phosphorylation: Occurs during cell stress, mitosis, and apoptosis

  • Glycosylation: O-GlcNAcylation affects filament organization

  • Acetylation: Influences protein stability and interactions

  • Caspase cleavage: Generates specific fragments during apoptosis

• Specialized antibody approaches:

  • Phospho-specific antibodies targeting known modification sites

  • M30 antibody: Specifically recognizes caspase-cleaved KRT18 fragment

  • Antibodies against other PTM forms are emerging research tools

• Applications in research:

  • Measuring apoptosis in epithelial cells and tissues

  • Monitoring stress responses in experimental models

  • Assessing drug efficacy in inducing apoptosis in epithelial tumors

  • Biomarker development for disease progression