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CHEK2 / Serine/threonine-protein kinase Chk2 · IHC design guide
Design Immunohistochemistry for CHEK2
Plan CHEK2 IHC-P around nuclear staining in most tissues (HPA tissue IHC) and a 0.5–1 μg/mL catalog antibody working range (datasheet: PB9692). This guide covers fixation, antigen retrieval, chromogenic detection and cell-type scoring.
Evidence assembled Oct 2026 · For research use; verify linked source records and product datasheet before use
CHEK2 Immunohistochemistry Experimental Design Guide
Expected localisation, validated protocols, controls and antibodies — the at-a-glance facts below, then the full design guide.
Must know before staining
| Expected localisation | Nuclear staining in most tissues (HPA tissue IHC) | |
| Staining pattern | Nuclear signal in most tissues, including colon glands (HPA tissue IHC) | |
| Antigen retrieval | EDTA pH 8.0 HIER, heat-mediated (datasheet PB9692) | |
| Positive control | Adrenal gland+4 more · see all | |
| Negative control | Adipose tissue+4 more · see all |
Important caveats
Reasons your staining may differ from the expected pattern.
| Fixation | Keep formalin fixation consistent across sections (standard IHC practice; not target-specific); Matched tissue-IHC evidence does not establish the fixation claim. Validate the specimen-specific method before use. (selected-SKU IHC image PB9692) | |
| Caveat | Staining varies by cell type; adipocytes may lack signal (HPA tissue IHC) | |
| Regulation | DNA damage activates CHEK2 via Thr-68 (UniProt) | |
| Isoform / epitope | 13 isoforms; epitope coverage needs checking (UniProt) |
Section 1
Recommended CHEK2 IHC & IF Protocols
The catalog antibody’s IHC-P protocol (datasheet: PB9692) is followed by one published gastric cancer CHEK2 IHC protocol (PMC7967923).
| Sample | Paraffin-embedded human lung cancer tissue; fixative not specified (datasheet PB9692) |
| Fixation | Image fixative and duration unreported (datasheet PB9692); verify before use. |
| Sectioning | 4–5 µm sections on charged slides (standard) |
| Deparaffinisation | Xylene, graded ethanol series to water (standard) |
| Antigen retrieval | Heat retrieval: EDTA pH 8.0 (datasheet PB9692); 20 min, 95–100 °C (standard) |
| Peroxidase block | 3% H2O2, 10 min, room temperature (standard) |
| Blocking | 10% goat serum (datasheet PB9692) |
| Primary antibody | Rabbit anti-CHEK2, 0.5-1μg/ml (datasheet PB9692) |
| Primary incubation | Overnight at 4 °C (datasheet PB9692) |
| Detection | Streptavidin-biotin complex (SABC), DAB chromogen (datasheet PB9692) |
| Counterstain | Hematoxylin, blue, dehydrate and mount (standard) |
| Expected result | CHEK2-positive staining in glandular cells of adrenal gland (HPA tissue IHC: High). HPA tissue profile: Nuclear expression in most tissues. No signal in the no-primary control. |
💡Decision noteStart with heat-mediated EDTA pH 8.0 for the catalog antibody (datasheet: PB9692); the published protocol reports retrieval at pH 6.0 or 9.0 (PMC7967923).
Section 2
What Is the Expected CHEK2 Staining Pattern?
CHEK2 is principally nuclear, with nucleoplasmic and PML-body localization (UniProt O96017). In paraffin-section IHC, expect nuclear staining in many tissues, including glandular epithelium and bronchial basal cells (HPA tissue IHC: nuclear expression in most tissues; High in listed cells). HPA rates the tissue profile Enhanced, with medium consistency between staining and RNA data (HPA tissue IHC). CHEK2 has no transmembrane segment (UniProt O96017 topology).
| Distinct nuclear chromogen in colon or appendix glandular cells, or bronchial basal cells. | This fits the reported compartment and examples of High staining (HPA tissue IHC). Judge the specified cells against surrounding tissue and the negative control; the label “High” does not prescribe an absolute intensity for every run. |
| Predominantly cytoplasmic or membranous staining in a tissue expected to show nuclear CHEK2. | Recheck specificity and detection background before calling this CHEK2: the tissue IHC profile is nuclear (HPA tissue IHC). UniProt lists isoform 10 throughout the cell, so an extranuclear pattern alone cannot prove an artefact (UniProt O96017). |
| Strong staining in prostate glandular cells, skeletal myocytes, or adipose adipocytes. | These cells are listed as Not detected (HPA tissue IHC). Compare a positive tissue and a negative control in the same run; unexpected staining may reflect cross-reactivity or endogenous detection activity (standard IHC practice), but needs investigation before assignment. |
| Widespread pale chromogen across nuclei, cytoplasm, and tissue spaces. | A diffuse deposit does not match the reported mainly nuclear tissue pattern (HPA tissue IHC). Check the negative control and review blocking, wash, and detection conditions for background (standard IHC practice); do not score diffuse haze as nuclear positivity. |
| No nuclear signal in a colon glandular-cell control. | Colon glandular cells are listed as High (HPA tissue IHC), so an absent signal calls for a run review. Confirm tissue identity and preservation, then check primary-antibody and detection steps (standard IHC practice); one failed section does not establish CHEK2 absence. |
💡Expected CHEK2 appearanceCall a convincing positive when chromogen is clearly nuclear in expected cells, such as High-staining colon glandular cells (HPA tissue IHC); diffuse nonnuclear deposit or staining confined to a negative control is suspect (standard IHC interpretation).
| Cell and tissue context | HPA reports High staining in several glandular epithelia, bronchial basal cells, and esophageal squamous cells, while specified adipocytes, myocytes, and prostate glandular cells are Not detected (HPA tissue IHC). Match the scored cell type, not merely the organ name. |
| Isoforms and antibody recognition | UniProt lists 13 CHEK2 isoforms, with isoform 10 present throughout the cell (UniProt O96017). The supplied record gives no epitope for the catalog antibody; do not infer which isoforms it detects or treat every extranuclear signal as confirmed CHEK2. |
| Phosphorylation and interpretation | CHEK2 has reported modified residues, including Thr-68 and autophosphorylation sites (UniProt O96017). The supplied antibody data do not establish phosphosite specificity. Routine CHEK2 staining therefore cannot by itself be scored as activated CHEK2 or as a direct measure of DNA damage response. |
| Antibody and tissue validation | CAB002030 is IHC Enhanced; HPA001878 is IHC Approved (HPA antibodies). The tissue-level Enhanced rating carries a medium RNA–staining consistency description (HPA tissue IHC). Keep these validation statements distinct when weighing an unexpected pattern. |
| What should IF/ICC show? | Predominantly nucleoplasmic signal is supported; additional Golgi localization is uncertain (HPA subcellular ICC-IF). UniProt also lists nuclear PML bodies and isoform 10 throughout the cell (UniProt O96017). These IF observations do not establish an alternate paraffin-IHC scoring pattern. |
| Situation | Likely cause | Next action |
|---|---|---|
| Known-positive colon glandular cells show no nuclear chromogen. | A failed primary-antibody or detection step is possible (standard IHC practice); the expected cell is High (HPA tissue IHC). | Check tissue identity, section preservation, reagent sequence, and detection controls; repeat with a verified positive section (standard IHC practice). |
| Nuclei are faint, while the negative control is clean. | Signal may be below the chosen scoring threshold (standard IHC practice); intensity can vary by cell and tissue (HPA tissue IHC). | Compare matched positive and negative tissues, then optimize antigen retrieval and primary-antibody conditions using ordinary IHC controls (standard IHC practice). No CHEK2-specific retrieval sensitivity is established here. |
| Cytoplasm dominates staining in a High-listed glandular tissue. | Background or cross-reactivity is possible (standard IHC practice); isoform 10 is reported throughout the cell (UniProt O96017). | Review the negative control and nuclear pattern in a positive tissue before assigning the signal. Do not infer isoform identity from compartment alone (UniProt O96017). |
| Prostate glandular cells stain as strongly as the positive tissue. | This conflicts with Not detected prostate glandular cells (HPA tissue IHC); cross-reactivity or endogenous detection activity is possible (standard IHC practice). | Check a no-primary control, blocking, and detection conditions; repeat the tissue comparison before reporting CHEK2 positivity (standard IHC practice). |
| Every compartment has a weak brown haze. | Nonspecific chromogen or detection background can obscure nuclear scoring (standard IHC practice). | Inspect negative controls and review blocking, washing, and development conditions (standard IHC practice). Score only distinguishable cellular staining, using the nuclear HPA pattern as context (HPA tissue IHC). |
| An IF/ICC image shows a Golgi-like signal alongside nuclear staining. | HPA supports nucleoplasmic localization but labels the additional Golgi localization uncertain (HPA subcellular ICC-IF). | Treat the Golgi-like signal as provisional and assess it with IF controls on the separate IF/ICC guide page; keep paraffin-IHC interpretation anchored to the tissue nuclear profile (HPA tissue IHC). |
Experiment evidence
IHC & IF images showing CHEK2 staining
PB9692 · IHCIHC analysis of Chk2 using anti-Chk2 antibody (PB9692). Chk2 was detected in a paraffin-embedded section of human lung cancer tissue. Heat m
A00277-1 · IHCCHEK2 Antibody (N-term) IHC analysis in formalin fixed and paraffin embedded colon carcinoma followed by peroxidase conjugation of the secon
A00277-1 · IFConfocal immunofluorescent analysis of CHEK2 Antibody (N-term) with HepG2 cell followed by Alexa Fluor 488-conjugated goat anti-rabbit lgG (
M00277 · IHCImmunohistochemical analysis of paraffin-embedded human testis, using Chk2 Antibody.
M00277 · IFImmunofluorescent analysis of Hela cells, using Chk2 Antibody.
M00277-3 · IHCHuman colon was stained with anti-Chk2 rabbit antibody
M00277-4 · IHCMouse spleen was stained with anti-Chk2 rabbit antibody
A00277 · IFImmunocytochemistry of Chk2 in Jurkat cells with Chk2 antibody at 1 μg/mL.
A00277-2 · IFIF analysis of CHEK2 using anti-CHEK2 antibody (A00277-2) and anti-Beta Tubulin antibody (M01857-3). CHEK2 was detected in immunocytochemica
HPA · Cerebral cortexHuman Protein Atlas IHC, Cerebral cortex. Source: https://www.proteinatlas.org/ENSG00000183765-CHEK2/tissue/cerebral+cortex#imid_909776
HPA · ColonHuman Protein Atlas IHC, Colon. Source: https://www.proteinatlas.org/ENSG00000183765-CHEK2/tissue/colon#imid_909694
HPA · LiverHuman Protein Atlas IHC, Liver. Source: https://www.proteinatlas.org/ENSG00000183765-CHEK2/tissue/liver#imid_909711
HPA · KidneyHuman Protein Atlas IHC, Kidney. Source: https://www.proteinatlas.org/ENSG00000183765-CHEK2/tissue/kidney#imid_909704
HPA · ICC-IF A-431Human Protein Atlas immunofluorescence, A-431, antibody HPA001878; green = CHEK2, blue = nucleus, red = microtubules.
HPA · ICC-IF A-431Human Protein Atlas immunofluorescence, A-431, antibody HPA001878; green = CHEK2, blue = nucleus, red = microtubules.
← swipe / scroll for more images →
Real IHC / IF data behind the staining-pattern expectations in this section.
Sample controls for CHEK2 IHC & IF
🧪Run colon first; glandular cells should stain (HPA: High in colon glandular cells). Use parathyroid gland as the negative tissue (HPA: Not detected in parathyroid glandular cells); on the colon slide, assess unstained neighboring cells as internal negatives only after confirming their identity and background with the omission control.
Positive control tissue: Adrenal gland (Glandular cells, HPA High)
Negative control tissue: Adipose tissue (HPA Not detected)
ICC-IF cell lines (HPA subcellular resource): HPA ICC-IF images show CHEK2 in A-431, Hep-G2, NIH 3T3, with annotated localisation: Nucleoplasm (supported) (HPA subcellular).
Technical controls: Include no-primary (secondary-only) and isotype controls, using rabbit IgG matched to the primary antibody’s clonality and concentration where possible (PB9692 caption: rabbit primary antibody). Confirm specificity with CHEK2 knockout tissue or a validated peptide block; for colon DAB staining, suppress endogenous peroxidase and check endogenous biotin background because the reported detection uses a streptavidin–biotin complex (PB9692 caption: SABC with DAB).
⚠️Feasibility: A target-specific fixation window or fixation effect is unreported, and the selected PB9692 tissue-IHC caption does not state the fixative (PB9692 caption: fixative not stated). The reported paraffin-section staining used heat retrieval in EDTA, pH 8.0, but retrieval dependence across conditions is unreported (PB9692 caption: EDTA heat retrieval). Frozen sections are not established as easier by the supplied evidence; ICC-IF images support a mainly nucleoplasmic readout, while colon sections require attention to biotin and peroxidase background with the reported DAB method (HPA: supported nucleoplasm; PB9692 caption: SABC with DAB).
HPA tissue IHC evidence for CHEK2
Comprehensive Human Protein Atlas IHC scoring per tissue (reliability: Enhanced — Medium consistency between antibody staining and RNA expression data.). Rows are taken directly from the HPA tissue chart — click any row's HPA link to view the source.
Positive expression · recommended positive controls
| Tissue | Cell type | Level | Evidence | Source |
|---|---|---|---|---|
| Adrenal gland | Glandular cells | High | Protein (IHC) | HPA → |
| Appendix | Glandular cells | High | Protein (IHC) | HPA → |
| Bronchus | Basal cells | High | Protein (IHC) | HPA → |
| Colon | Glandular cells | High | Protein (IHC) | HPA → |
| Duodenum | Glandular cells | High | Protein (IHC) | HPA → |
Undetected expression · recommended negative controls
| Tissue | Cell type | Level | Evidence | Source |
|---|---|---|---|---|
| Adipose tissue | Adipocytes | Not detected | Protein (IHC) | HPA → |
| Bone marrow | Hematopoietic cells | Not detected | Protein (IHC) | HPA → |
| Parathyroid gland | Glandular cells | Not detected | Protein (IHC) | HPA → |
| Prostate | Glandular cells | Not detected | Protein (IHC) | HPA → |
| Seminal vesicle | Glandular cells | Not detected | Protein (IHC) | HPA → |
Section 3
Advanced CHEK2 IHC Tips
Troubleshoot CHEK2 staining in paraffin sections by checking retrieval, nuclear localisation, controls and scoring before interpreting chromogenic signal (datasheet PB9692; HPA tissue IHC).
How should I retrieve CHEK2 in paraffin sections when nuclear staining is weak?
Start with heat-mediated retrieval in EDTA at pH 8.0 for the IHC-validated antibody (datasheet PB9692). The documented paraffin-section example used this retrieval before an overnight incubation at 4°C with 1 μg/ml primary antibody (datasheet PB9692). If nuclear staining remains weak, compare a shorter and longer heating interval on adjacent sections while holding antibody concentration and DAB development constant (standard IHC practice; HPA tissue IHC: nuclear expression in most tissues). Include a positive control with documented nuclear staining, such as colon glandular cells, and inspect morphology because excessive heating can damage sections (HPA tissue IHC: high in colon glandular cells; standard IHC practice).
Could fixation explain weak or patchy CHEK2 staining?
Target-specific fixation sensitivity is unknown: the selected paraffin-section caption does not report its fixative (datasheet PB9692). Record the fixative, fixation duration and section age for each specimen, then compare sections processed alike before changing retrieval or antibody concentration (standard IHC practice). If signal differs between specimens, assess nuclear morphology and run a control section through the same staining batch; neither a fixation effect nor its direction can be assigned from these data (standard IHC practice; datasheet PB9692: fixative unreported). Keep EDTA at pH 8.0 and the documented 1 μg/ml primary concentration constant while investigating processing differences (datasheet PB9692).
How should I troubleshoot strong cytoplasmic staining with little nuclear signal?
Expect predominantly nuclear staining in tissue: CHEK2 is reported in the nucleus, nucleoplasm and PML bodies, and the tissue IHC profile is nuclear in most tissues (UniProt O96017; HPA tissue IHC). Check whether the DAB deposit aligns with counterstained nuclei at high magnification, using a no-primary control to assess nonspecific detection (standard IHC practice). Diffuse cytoplasmic colour alone is insufficient to establish CHEK2 expression, although isoform 10 is reported throughout the cell (UniProt O96017). Repeat staining with the documented EDTA pH 8.0 retrieval and compare a documented nuclear-positive cell population before assigning unusual localisation (datasheet PB9692; HPA tissue IHC: high in colon glandular cells).
Could isoforms or phosphorylation explain different staining patterns between antibodies?
CHEK2 has 13 reported isoforms, and isoform 10 is present throughout the cell, so epitope coverage matters when comparing antibodies (UniProt O96017). The record lists an FHA domain at residues 113–175, a kinase domain at 220–486, and phosphorylation sites including Thr-68 (UniProt O96017). Check each antibody’s stated immunogen or epitope and whether it detects total CHEK2 or a specified phosphosite before comparing staining intensity (standard IHC practice; UniProt O96017: CHEK2 is phosphorylated). An epitope-specific explanation remains tentative without epitope mapping or orthogonal validation; use matched controls and the same retrieval conditions for the comparison (standard IHC practice; datasheet PB9692: EDTA pH 8.0).
How can I check CHEK2 localisation by multiplex IF?
For a separate IF assay, pair CHEK2 with a marker identifying the cell population under study and a nuclear counterstain, then assess colocalisation at the single-cell level (standard IF practice; HPA subcellular: nucleoplasm supported). Select fluorophores after inspecting unstained tissue autofluorescence, favouring a cleaner spectral channel for the weaker signal and including single-stain controls (standard IF practice). CHEK2 has no transmembrane segment and is mainly nucleoplasmic, so use controlled permeabilisation to make the intracellular epitope accessible while preserving nuclear structure (UniProt O96017; HPA subcellular; standard IF practice). Interpret extra-nuclear signal cautiously because isoform 10 is reported throughout the cell and the additional Golgi location is uncertain (UniProt O96017; HPA subcellular).
What should I change when DAB background obscures CHEK2-positive nuclei?
First inspect a no-primary section and check whether colour follows tissue edges, damaged areas or the secondary detection system (standard IHC practice). The documented example used 10% goat serum blocking, biotinylated goat anti-rabbit secondary antibody and a streptavidin–biotin DAB system, so review each of those steps when troubleshooting (datasheet PB9692). Include an endogenous peroxidase block and assess possible endogenous biotin signal with appropriate controls for this detection chemistry (standard IHC practice; datasheet PB9692: biotin-based detection). If background persists, titrate the 1 μg/ml primary or shorten DAB development while retaining a documented nuclear-positive control (datasheet PB9692; HPA tissue IHC: nuclear expression in most tissues; standard IHC practice).
How should I quantify heterogeneous nuclear CHEK2 staining across sections? ⚠ ANSWER MARKED FOR VERIFICATION
Define the cell population and regions before scoring, then record the percentage of nuclei in each intensity category and calculate a nuclear H-score (standard IHC practice; HPA tissue IHC: nuclear expression in most tissues). For sparse populations, report positive nuclei per mm² alongside the number of evaluable nuclei and sampled area (standard IHC practice). Normalise comparisons to the same cell type, section area, retrieval, antibody concentration and DAB development, since staining varies across tissue compartments (standard IHC practice; HPA tissue IHC: high in colon glandular cells and undetected in adipocytes). Exclude necrotic or detached regions using predefined criteria, and report cytoplasmic staining separately rather than adding it to the nuclear score (standard IHC practice; UniProt O96017: predominantly nuclear).
When does a CHEK2-positive DAB signal support a biological conclusion?
A credible pattern places signal in intact nuclei of the expected cell population and reproduces across controls; CHEK2 is mainly nuclear, while tissue IHC shows nuclear expression in most tissues (UniProt O96017; HPA tissue IHC; standard IHC practice). Compare a documented high-staining population, such as colon glandular cells, with a reported undetected population, such as adipocytes, within an appropriately matched experiment (HPA tissue IHC). Treat edge staining, necrotic deposits, diffuse staining in the wrong compartment and colour in a no-primary section as possible artefacts, including endogenous enzyme activity (standard IHC practice). Total CHEK2 staining alone does not establish kinase activation or DNA-damage signalling; a site-specific assay and suitable controls are needed for that inference (UniProt O96017: phosphorylation and checkpoint function; standard IHC practice).
Boster reagents
Best CHEK2 / Serine/threonine-protein kinase Chk2 IHC Antibodies
Catalog images show CHEK2 staining in human lung cancer, colon carcinoma, testis and colon, mouse spleen, and Jurkat cells (catalog image captions).
Real IHC data
Anti-Chk2/CHEK2 Antibody ®
Cat # PB9692
Real IHC data
Anti-CHEK2 Antibody (N-term)
Cat # A00277-1
Real IHC data
Anti-Chk2 CHEK2 Rabbit Monoclonal Antibody
Cat # M00277
Real IHC data
Anti-Chk2 Rabbit Monoclonal Antibody
Cat # M00277-3
Real IHC data
Anti-Chk2 Rabbit Monoclonal Antibody
Cat # M00277-4
Real IF data
Anti-Chk2 CHEK2 Antibody
Cat # A00277
PB9692 shows paraffin-embedded human lung cancer (PB9692 image caption); A00277-1 shows formalin-fixed, paraffin-embedded colon carcinoma (A00277-1 image caption); M00277 shows paraffin-embedded human testis (M00277 image caption); M00277-3 shows human colon (M00277-3 image caption); and M00277-4 shows mouse spleen (M00277-4 image caption). A00277 shows ICC staining in Jurkat cells (A00277 image caption).
Which to pick: For tissue IHC with documented fixation, choose A00277-1 for paraffin-section, paraffin-embedded tissue (A00277-1 image caption); PB9692 and M00277 show paraffin sections, but their captions do not report the fixative (PB9692 and M00277 image captions). For IF/ICC, A00277 lists both applications and shows Jurkat ICC staining (A00277 catalog and image caption). For work across species, M00277-3 lists IHC and Human, Mouse and Rat reactivity, while its image documents human colon only (M00277-3 catalog and image caption). The selected PB9692 tissue-IHC caption documents paraffin sections, but does not specify the fixative (selected-SKU IHC image PB9692).
Each figure is that product's own IHC / IF validation image from its datasheet.
References
- UniProt Consortium. UniProt entry O96017 (CHK2_HUMAN, Serine/threonine-protein kinase Chk2).
- Human Protein Atlas. CHEK2 tissue IHC expression (reliability: Enhanced).
- Human Protein Atlas. CHEK2 subcellular location (ICC-IF): Mainly localized to the nucleoplasm. In addition localized to the Golgi apparatus..
- Human Protein Atlas. CHEK2 antibody validation summary (2 antibodies).
- Status of CHEK2 and p53 in patients with early-onset and conventional gastric cancer. Oncology letters 2021 — PMC7967923.
- Recurrent Germline Mutations of CHEK2 as a New Susceptibility Gene in Patients with Pheochromocytomas and Paragangliomas. International journal of endocrinology 2021 — PMC8497153.
- Relationship between the Expression of CHK2 and p53 in Tumor Tissue and the Course of Papillary Thyroid Cancer in Patients with CHEK2 Germline Mutations. Cancers 2024 — PMC10886656.
- Expression of DNA doublestrand repair proteins in oral leukoplakia and the risk of malignant transformation. Oncology letters 2018 — PMC6004653.
- PubMed PMID:9836640 — UniProt-cited evidence.
- PubMed PMID:9889122 — UniProt-cited evidence.
- PubMed PMID:10097108 — UniProt-cited evidence.
Immunohistochemistry protocol sheet for CHEK2 (Serine/threonine-protein kinase Chk2). Expected localisation Nuclear staining in most tissues (HPA tissue IHC). Antigen retrieval: EDTA pH 8.0 HIER, heat-mediated (datasheet PB9692). Validated IHC antibody: PB9692 at 0.5-1μg/ml (the product's own IHC validation image is shown). Controls (HPA): positive Adrenal gland (Glandular cells); negative Adipose tissue. IHC-P workflow on paraffin sections; fixative unspecified. Protocol steps: 1. Sample: Paraffin-embedded human lung cancer tissue; fixative not specified (datasheet PB9692); 2. Fixation: Image fixative and duration unreported (datasheet PB9692); verify before use.; 3. Sectioning: 4–5 µm sections on charged slides (standard); 4. Deparaffinisation: Xylene, graded ethanol series to water (standard); 5. Antigen retrieval: Heat retrieval: EDTA pH 8.0 (datasheet PB9692); 20 min, 95–100 °C (standard); 6. Peroxidase block: 3% H2O2, 10 min , room temperature (standard); 7. Blocking: 10% goat serum (datasheet PB9692); 8. Primary antibody: Rabbit anti-CHEK2, 0.5-1μg/ml (datasheet PB9692); 9. Primary incubation: Overnight at 4 °C (datasheet PB9692). Watch for: Fixation: Keep formalin fixation consistent across sections (standard IHC practice; not target-specific); Matched tissue-IHC evidence does not establish the fixation claim. Validate the specimen-specific method before use. (selected-SKU IHC image PB9692); Caveat: Staining varies by cell type; adipocytes may lack signal (HPA tissue IHC); Isoform / epitope: 13 isoforms; epitope coverage needs checking (UniProt); Regulation: DNA damage activates CHEK2 via Thr-68 (UniProt). Evidence: UniProt O96017, HPA tissue IHC · Enhanced, HPA ICC-IF · Mainly localized to the nucleoplasm. In addition localized to the…, Datasheet PB9692, PMC7967923. QR code links to https://www.bosterbio.com/bosterbio-gene-info-cards/CHEK2/immunohistochemistry-ihc-guide.