KRT18 Antibody

What is KRT18 and why is it an important target for antibody-based detection?

KRT18 (Cytokeratin 18) is a type I intermediate filament protein found primarily in non-squamous epithelia. It forms heterodimers with KRT8, creating a stable cytoskeletal network that provides structural integrity and resilience to epithelial cells . KRT18 is widely expressed in various single-layered epithelial cells, including gastrointestinal tract epithelium, hepatocytes, and colorectal cancer cells . It serves as an important biomarker in cancer research and plays roles in:

• Maintaining cell shape and stability

• Cell migration and invasion processes

• Cancer progression, particularly in adenocarcinomas and ductal carcinomas

• Embryonic development, especially in trophoblast function

What tissue reactivity can I expect from KRT18 antibodies?

KRT18 antibodies typically react with tissues from:

KRT18 antibodies react with epithelial tumors of the gastrointestinal tract, lung, breast, pancreas, ovary, and thyroid, making them valuable diagnostic tools .

What are the common applications for KRT18 antibodies in research?

KRT18 antibodies can be utilized in multiple experimental applications:

The application should be optimized for each specific antibody and experimental system .

How should I optimize antigen retrieval for KRT18 immunohistochemistry?

For optimal KRT18 immunohistochemistry, antigen retrieval is critical:

• Primary recommendation: Use TE buffer pH 9.0 for heat-induced epitope retrieval

• Alternative approach: Citrate buffer pH 6.0 can also be effective

• Protocol specifics:

  • For formalin-fixed paraffin-embedded tissues, deparaffinize and rehydrate sections

  • Perform heat-induced epitope retrieval using a pressure cooker or microwave

  • For microwave retrieval, treat sections in buffer for approximately 20 minutes at moderate power

  • Allow sections to cool before proceeding with blocking and antibody incubation

For example, one validated protocol involves incubating sections in 10 mM sodium citrate buffer for 10 minutes and microwaving them for 20 minutes, followed by treatment with 0.3% H₂O₂ to inhibit endogenous peroxidase activity .

What controls should I include when using KRT18 antibodies?

For rigorous experimental design, include the following controls:

• Positive tissue controls:

  • Human liver tissue (consistently high KRT18 expression)

  • HepG2 cells for cell-based assays

  • A431, A549, or HCT116 cells for Western blotting

• Negative controls:

  • Stratified squamous epithelia (naturally KRT18 negative)

  • Use phosphate-buffered saline or isotype-matched IgG instead of primary antibody

• Validation controls:

  • For functional studies, include KRT18 knockdown/knockout models

  • For specificity verification, evaluate molecular weight on Western blots (expected at 48 kDa)

What are the recommended storage conditions for KRT18 antibodies?

To maintain antibody functionality:

• Store at -20°C for long-term storage

• Most KRT18 antibodies remain stable for one year after shipment when properly stored

• Aliquoting is generally unnecessary for -20°C storage, but may be recommended for frequently used antibodies

• Most KRT18 antibodies are supplied in PBS with 0.02% sodium azide and 50% glycerol at pH 7.3

How can KRT18 antibodies be used to distinguish between apoptosis and necrosis?

KRT18 antibodies can effectively distinguish between different modes of cell death through selective detection of full-length versus cleaved forms:

• M30 antibody: Detects caspase-cleaved KRT18 fragments (aKRT18) released during apoptosis

• M65 antibody: Binds both cleaved (aKRT18) and full-length KRT18 (nKRT18), measuring total KRT18 (tKRT18)

The ratio between these forms provides valuable information about the predominant cell death mechanism:

• High M30/M65 ratio suggests predominantly apoptotic cell death

• Low M30/M65 ratio with elevated M65 suggests necrotic cell death

This approach has been validated in clinical studies, particularly for assessing liver damage and cancer progression, where serum KRT18 levels reflect tumor necrosis and correlate with systemic inflammation .

What is the relationship between KRT18 expression and cancer progression?

KRT18 expression has significant implications for cancer biology:

• Expression correlation with clinical parameters:

  • High KRT18 expression is positively associated with advanced clinical stage, tumor invasion depth, lymph node metastasis, and distant metastasis in colorectal cancer

  • In colorectal cancer, KRT18 shows high expression in 57.4% of tumor tissues compared to only 27.8% of normal colorectal tissues (p=0.002)

• Functional roles in cancer progression:

  • Silencing KRT18 inhibits cancer cell viability, migration, and invasion in vitro

  • KRT18 may interact with signaling pathways including Notch1 and PI3K/Akt/NF-κB

• Potential as prognostic marker:

  • High KRT18/8 ratio predicts aggressive hepatocellular cancer behavior

  • KRT18 serves as an oncogenic factor in colorectal cancer and may be a therapeutic target

How can I use KRT18 antibodies in multiplexed immunofluorescence studies?

For advanced multiplexed immunofluorescence:

• Panel design considerations:

  • KRT18 antibodies work well with other epithelial markers (E-cadherin, pan-cytokeratin)

  • Can be combined with immune cell markers (CD3, CD8, CD68, FoxP3) for tumor microenvironment studies

  • Choose complementary fluorophores with minimal spectral overlap (e.g., CF®488A, CF®568, CF®640R)

• Methodology:

  • Sequential staining approach: Apply antibodies sequentially with intermediate stripping or quenching steps

  • Simultaneous staining: Use antibodies from different host species to avoid cross-reactivity

  • Analyze with spectral imaging to separate overlapping fluorescence signals

• Technical considerations:

  • Test each antibody individually before multiplexing

  • Include appropriate controls for each marker

  • Use automated image analysis for objective quantification of co-localization and expression patterns

Why am I seeing weak or absent KRT18 staining in my IHC experiments?

Several factors can contribute to suboptimal KRT18 staining:

• Inadequate antigen retrieval:

  • Solution: Try more aggressive antigen retrieval using TE buffer pH 9.0 rather than citrate buffer

  • For microwave retrieval, ensure sufficient heating time (20+ minutes)

• Suboptimal antibody concentration:

  • Solution: Perform a titration series (e.g., 1:50, 1:100, 1:200, 1:500) to determine optimal dilution

  • Different tissues may require different antibody concentrations

• Sample fixation issues:

  • Solution: Ensure consistent fixation protocol; overfixation can mask epitopes

  • For clinical samples with unknown fixation, consider testing multiple antigen retrieval methods

• Epitope masking by protein-protein interactions:

  • Solution: Add detergents (0.1-0.3% Triton X-100) to enhance antibody penetration

  • Consider pre-treatment with protein denaturants for highly cross-linked samples

How can I reduce background when using KRT18 antibodies in immunofluorescence?

To minimize background staining:

• Optimize blocking:

  • Use 5% nonfat dried milk or 3-5% BSA in PBS for effective blocking

  • Consider adding 0.1-0.3% Triton X-100 to reduce non-specific binding

• Antibody dilution and incubation:

  • Use higher dilutions of primary antibody (1:200-1:500 for IF)

  • Extend primary antibody incubation to overnight at 4°C

  • Perform extensive washing steps (3-5 times, 5-10 minutes each)

• Secondary antibody optimization:

  • Pre-absorb secondary antibodies against tissue powder

  • Use highly cross-adsorbed secondary antibodies to reduce species cross-reactivity

  • Include negative controls using secondary antibody alone

• Autofluorescence reduction:

  • Treat sections with 0.1% Sudan Black in 70% ethanol

  • Consider using commercial autofluorescence quenching reagents

How can KRT18 antibodies be utilized in embryonic development research?

Recent research has revealed important roles for KRT18 in embryo development:

• Expression pattern in embryos:

  • KRT18 is specifically expressed in trophoblasts at the blastocyst stage before implantation

  • It localizes in the cytoplasm of trophectoderm cells

  • No apparent expression during earlier embryonic stages

• Functional significance:

  • Knockdown of KRT18 in trophoblasts impairs mouse embryo adhesion (reduced from 61.41% to 23.17%) and implantation

  • KRT18 regulates trophoblast cell migration and invasion, critical processes for embryo implantation

• Experimental approaches:

  • Use immunofluorescence with phalloidin co-staining to visualize KRT18 and F-actin architecture

  • Employ trophoblast-specific knockdown models using lentiviral delivery of siRNAs

  • Assess cell adhesion, migration and invasion using in vitro assays

What is the relationship between KRT18 and E-cadherin in cellular functions?

KRT18 has important interactions with E-cadherin that affect cellular behavior:

• Direct binding interaction:

  • KRT18 directly binds to E-cadherin with a binding affinity (Kd) of 5.5979 μM

  • This interaction was confirmed using microscale thermophoresis (MST)

• Functional relationship:

  • Knockdown of KRT18 causes a significant decrease in E-cadherin expression

  • This may impair cell-cell adhesion and affect cellular mobility

  • The KRT18-E-cadherin interaction may be critical for maintaining epithelial integrity

• Experimental approaches:

  • Co-immunoprecipitation to verify protein-protein interactions

  • Proximity ligation assays to visualize interactions in situ

  • Targeted mutagenesis to identify specific binding domains

This relationship helps explain how KRT18 contributes to cell adhesion and migration, with implications for both development and cancer research.