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CST1 / Cystatin-SN · IHC design guide
Design Immunohistochemistry for CST1
Plan CST1 IHC on paraffin sections using salivary gland glandular cells as a medium positive reference (HPA tissue IHC). Expect cytoplasmic staining in a subset of cells (HPA tissue IHC), and start with the catalog antibody’s 1:100–1:300 IHC dilution (datasheet).
Evidence assembled Oct 2026 · For research use; verify linked source records and product datasheet before use
CST1 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 | Cytoplasm in a subset of salivary gland cells (HPA tissue IHC) | |
| Staining pattern | Cytoplasmic staining in some glandular cells (HPA tissue IHC) | |
| Antigen retrieval | Citrate pH 6.0 HIER, 95–98 °C, 20 min (rule: cytoplasmic / membrane antigen) | |
| Positive control | Salivary gland | |
| Negative control | Adipose tissue+4 more · see all |
Important caveats
Reasons your staining may differ from the expected pattern.
| Fixation | Keep fixation consistent across sections (standard IHC practice; not target-specific) | |
| Caveat | Secretion may separate protein staining from RNA location (HPA tissue IHC) | |
| Regulation | Salivary gland-enriched RNA (HPA tissue RNA) | |
| Isoform / epitope | No isoforms; mature chain 21–141 has no TM epitope split (UniProt) |
Section 1
Recommended CST1 IHC & IF Protocols
The catalog antibody’s IHC-P protocol is accompanied by published CST1 staining protocols for colorectal cancer (PMC5777761) and human liver tumors (PMC6767558).
| Sample | Paraffin-embedded human colon carcinoma tissue; fixative not specified (datasheet A30630) |
| Fixation | Image fixative and duration unreported (datasheet A30630); verify before use. |
| Sectioning | 4–5 µm sections on charged slides (standard) |
| Deparaffinisation | Xylene, graded ethanol series to water (standard) |
| Antigen retrieval | Heat-induced epitope retrieval in citrate buffer, pH 6.0, 20 min at 95–98 °C (standard rule: cytoplasmic / membrane antigen) |
| Peroxidase block | 3% H2O2, 10 min, room temperature (standard) |
| Blocking | 10% normal serum of the secondary host, 30 min, room temperature (standard) |
| Primary antibody | Rabbit anti-CST1, 1:100 - 1:300 (datasheet A30630) |
| Primary incubation | Overnight at 4 °C (standard) |
| Detection | HRP-polymer secondary, DAB chromogen 5–10 min (standard) |
| Counterstain | Hematoxylin, blue, dehydrate and mount (standard) |
| Expected result | CST1-positive staining in glandular cells of salivary gland (HPA tissue IHC: Medium). HPA tissue profile: Cytoplasmic expression in a subset of cells in salivary gland. No signal in the no-primary control. |
💡Decision noteStart with citrate pH 6.0 HIER at 95–98 °C for 20 min (page retrieval rule); the colorectal study used microwave citrate retrieval for 30 min (PMC5777761).
Section 2
What Is the Expected CST1 Staining Pattern?
CST1 is a secreted protein with a signal peptide and no transmembrane segment (UniProt P01037). In paraffin section IHC, expect cytoplasmic staining in a subset of salivary gland glandular cells, with medium staining reported by HPA (HPA tissue IHC). HPA rates the tissue pattern Enhanced, while cautioning that its staining may include protein from more than one gene (HPA tissue IHC).
| Cytoplasmic staining in some salivary gland glandular cells, with nearby cells unstained (HPA tissue IHC). | This matches the reported subset pattern; uniform staining of every glandular cell is not required for a positive result (HPA tissue IHC). Score the stained cell population as well as intensity (general IHC practice). |
| Predominantly nuclear or membrane outlined staining in salivary gland cells. | This departs from HPA’s cytoplasmic IHC pattern and CST1’s secreted, nontransmembrane annotation (HPA tissue IHC; UniProt P01037). Review localisation before interpreting it as CST1. |
| Staining of adipocytes in adipose tissue or respiratory epithelial cells in bronchus. | HPA reports CST1 as not detected in those cells (HPA tissue IHC). Such staining raises concern for antibody cross-reactivity or endogenous chromogenic detection activity; the image alone cannot distinguish them (general IHC practice). |
| Diffuse colour across cells and tissue spaces, obscuring cell boundaries. | This cannot establish the reported glandular cytoplasmic pattern (HPA tissue IHC). Nonspecific reagent binding, endogenous detection activity, or excess chromogen development can produce background (general IHC practice). |
| No staining in salivary gland glandular cells. | That conflicts with HPA’s medium positive tissue result, though its pattern involves only a subset of cells (HPA tissue IHC). Check that representative glandular cells are present before judging the run negative (general IHC practice). |
💡Expected CST1 appearanceCall a section positive when a subset of salivary gland glandular cells shows medium cytoplasmic staining (HPA tissue IHC); widespread nuclear, membrane outlined, or cell independent colour does not match that pattern (HPA tissue IHC; UniProt P01037; general IHC practice).
| Tissue and cell selection | Salivary gland glandular cells are the supplied positive reference; HPA reports Medium staining in a subset (HPA tissue IHC). Adipose adipocytes and bronchial respiratory epithelial cells are listed as not detected (HPA tissue IHC). |
| Secretion and topology | CST1 has a signal peptide, lacks a transmembrane segment, and is secreted (UniProt P01037). Interpret the observed intracellular signal against HPA’s cytoplasmic subset pattern; UniProt alone does not define an IHC compartment (HPA tissue IHC). |
| Protein processing | UniProt annotates signal residues 1–20 and a mature chain at 21–141, with no propeptide (UniProt P01037). The payload gives no antibody epitope, so it cannot predict which form the stain detects. |
| HPA interpretation limit | The tissue profile has Enhanced reliability through staining and RNA consistency, but HPA cautions that staining may include protein from more than one gene (HPA tissue IHC). Secreted protein may also appear away from cells expressing its RNA (HPA tissue IHC). |
| Antibody evidence | HPA lists IHC Supported for HPA043706 and HPA044763 and IHC Enhanced for CAB026769 (HPA antibodies). These ratings describe the listed antibodies; they do not establish the specificity of another antibody. |
| IF/ICC: what pattern is established? | HPA labels CST1 secreted but supplies no main ICC IF location or cell line images (HPA subcellular). An IF localisation cannot be confirmed from this payload; the observed salivary gland cytoplasmic pattern comes from tissue IHC (HPA tissue IHC). |
| Situation | Likely cause | Next action |
|---|---|---|
| Salivary gland section appears entirely negative. | The evaluated field may miss HPA’s positive glandular cell subset, or the IHC run may have failed (HPA tissue IHC; general IHC practice). | Examine additional glandular fields and verify a positive control and detection reagents before assigning a negative score (general IHC practice). |
| Colour is strongest in nuclei or forms crisp cell surface outlines. | That localisation differs from HPA’s cytoplasmic pattern and CST1’s nontransmembrane topology (HPA tissue IHC; UniProt P01037). | Compare the compartment with a salivary gland reference and review primary antibody dependent staining using a primary omitted control (general IHC practice). |
| Listed negative cells stain alongside the salivary gland positive cells. | Cross-reactivity or endogenous detection activity is possible; HPA also warns that its tissue stain may detect protein from more than one gene (HPA tissue IHC; general IHC practice). | Check a primary omitted section for detection activity, then compare the antibody’s validation evidence before assigning the signal to CST1 (general IHC practice; HPA antibodies). |
| The entire section has diffuse chromogenic background. | Background can arise from nonspecific binding, endogenous detection activity, or chromogen overdevelopment (general IHC practice). | Inspect a primary omitted control; review blocking, washes, primary antibody dilution, and development time using the validated IHC workflow (general IHC practice). |
| Only secretions or extracellular spaces show colour. | A secreted protein can appear away from its RNA expressing cells, but HPA’s documented tissue IHC pattern is cytoplasmic in glandular cells (HPA tissue IHC; UniProt P01037). | Record the extracellular signal separately and seek the reported glandular cell pattern before calling the section a matched IHC positive (HPA tissue IHC; general IHC practice). |
| A different antibody gives a broader staining pattern. | HPA’s validation ratings apply to its listed antibodies, and its Enhanced tissue profile retains a multi gene staining caution (HPA antibodies; HPA tissue IHC). | Compare the same salivary gland and listed negative cell types, and assess each antibody’s validation independently (HPA tissue IHC; general IHC practice). |
Experiment evidence
IHC & IF images showing CST1 staining
A30630 · IHCImmunohistochemistry analysis of paraffin-embedded human colon carcinoma tissue, using CST1 Antibody. The picture on the right is blocked wi
A30630 · IFImmunofluorescence analysis of MCF7 cells, using CST1 Antibody. The picture on the right is blocked with the synthesized peptide.
HPA · Cerebral cortexHuman Protein Atlas IHC, Cerebral cortex. Source: https://www.proteinatlas.org/ENSG00000170373-CST1/tissue/cerebral+cortex#imid_7193008
HPA · Salivary glandHuman Protein Atlas IHC, Salivary gland. Source: https://www.proteinatlas.org/ENSG00000170373-CST1/tissue/salivary+gland#imid_12572521
HPA · ColonHuman Protein Atlas IHC, Colon. Source: https://www.proteinatlas.org/ENSG00000170373-CST1/tissue/colon#imid_13117553
HPA · LiverHuman Protein Atlas IHC, Liver. Source: https://www.proteinatlas.org/ENSG00000170373-CST1/tissue/liver#imid_13117562
← swipe / scroll for more images →
Real IHC / IF data behind the staining-pattern expectations in this section.
Sample controls for CST1 IHC & IF
🧪Run salivary gland first; its glandular cells should stain (HPA: Medium in salivary gland glandular cells). Run adipose tissue as the negative (HPA: Not detected in adipocytes); on the salivary gland slide, assess any cells outside the glandular compartment for background staining rather than assuming they are validated negatives.
Positive control tissue: Salivary gland (Glandular cells, HPA Medium)
Negative control tissue: Adipose tissue (HPA Not detected)
ICC-IF cell lines (HPA subcellular resource): HPA carries no ICC-IF cell line for CST1; derive a cell-line control from the positive tissue's cell type (Glandular cells) and confirm it by RNA or western blot first.
Technical controls: Include a no-primary, secondary-only control and a primary-antibody host species and immunoglobulin class–matched isotype control; a peptide-block control is supported for the catalog antibody (A30630 tissue-IHC caption: peptide-blocked image). Quench endogenous peroxidase for chromogenic IHC and assess glandular autofluorescence if using IF; the tissue-IHC caption does not report a fixative (A30630 tissue-IHC caption: fixative not stated).
⚠️Feasibility: A target-specific fixation window and retrieval dependency are unreported in the supplied evidence; the paraffin-section caption does not identify the fixative (A30630 tissue-IHC caption: paraffin-embedded colon carcinoma; fixative not stated). The evidence does not establish whether frozen sections or IF would be easier (HPA: no cell lines with ICC-IF images). Secreted protein in glandular lumina could complicate cell-level scoring, so distinguish luminal signal from glandular cell staining (UniProt P01037: secreted; HPA: Medium in salivary gland glandular cells).
HPA tissue IHC evidence for CST1
Comprehensive Human Protein Atlas IHC scoring per tissue (reliability: Enhanced — High consistency between antibody staining and RNA expression data. Caution, targets protein from more than one gene. Secreted protein, tissue location of RNA and protein is expected to differ.). 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 |
|---|---|---|---|---|
| Salivary gland | Glandular cells | Medium | Protein (IHC) | HPA → |
Undetected expression · recommended negative controls
| Tissue | Cell type | Level | Evidence | Source |
|---|---|---|---|---|
| Adipose tissue | Adipocytes | Not detected | Protein (IHC) | HPA → |
| Adrenal gland | Glandular cells | Not detected | Protein (IHC) | HPA → |
| Appendix | Glandular cells | Not detected | Protein (IHC) | HPA → |
| Bone marrow | Hematopoietic cells | Not detected | Protein (IHC) | HPA → |
| Breast | Adipocytes | Not detected | Protein (IHC) | HPA → |
Section 3
Advanced CST1 IHC Tips
Troubleshoot CST1 staining in paraffin sections by checking retrieval, compartment, controls and scoring before comparing results across tissues.
What retrieval should I use if CST1 staining is weak in paraffin sections?
Use citrate buffer at pH 6.0 for heat induced epitope retrieval at 95–98 °C for 20 min (page retrieval setting). After cooling, compare the test section with a matched section that omits primary antibody, and keep detection and counterstaining conditions identical (standard IHC practice). Examine glandular cells in salivary gland as a positive reference, while allowing for staining of only a subset of cells (HPA: medium staining in salivary gland glandular cells; cytoplasmic expression in a subset). If staining remains weak, check section adhesion and antibody handling before testing another retrieval condition; no alternative buffer has CST1 specific support in the supplied evidence (standard IHC practice; supplied evidence).
Could fixation explain weak or uneven CST1 staining?
The supplied evidence does not establish how CST1 staining responds to any particular fixative or fixation duration, so target specific fixation sensitivity is unknown (supplied evidence). The catalog image shows paraffin embedded human colon carcinoma, but its caption does not report the fixative (A30630 caption). When comparing sections, document the actual fixative and processing history, then keep section thickness, citrate retrieval at pH 6.0, and detection conditions consistent (standard IHC practice; page retrieval setting). If staining varies between blocks, compare controls processed alongside each block before attributing the difference to fixation; neither the HPA staining pattern nor CST1 topology establishes a fixation effect (standard IHC practice; HPA tissue IHC; UniProt P01037 topology).
Should I score cytoplasmic and extracellular CST1 staining together?
Score cellular and extracellular staining separately because CST1 is secreted and has no transmembrane segment (UniProt P01037 subcellular location and topology). Cytoplasmic staining in a subset of salivary gland cells is an observed tissue pattern, while the secreting cell and deposited protein can occupy different locations (HPA tissue IHC: cytoplasmic subset; HPA reliability description: secreted protein). Record which glandular cells stain, the intensity within those cells, and any luminal or extracellular signal as distinct observations (HPA tissue IHC; standard IHC practice). For an unexpected compartment, inspect morphology and the primary antibody omission control before calling the staining CST1 specific (standard IHC practice).
How can I assess whether the antibody detects mature CST1 specifically?
CST1 is annotated as a 141 amino acid precursor with a signal peptide at residues 1–20 and a mature chain at 21–141; no isoforms or glycosylation sites are annotated (UniProt P01037 processing, isoforms and glycosylation). Establish where the catalog antibody binds before assuming its epitope remains present after secretion or paraffin processing (UniProt P01037 processing; standard IHC practice). The paired peptide blocked colon carcinoma image supports competition by that peptide under the imaged conditions, but does not by itself distinguish CST1 from related proteins (A30630 caption; HPA reliability description: antibody stains protein from more than one gene). Interpret unexpected staining with that cross recognition caveat and, where available, an independent antibody recognizing a different epitope (HPA reliability description; standard IHC practice).
How should I extend a CST1 IHC finding to multiplex immunofluorescence?
Treat IF as a separate assay: the supplied tissue image documents paraffin section IHC, and the HPA subcellular record lists no cell lines with ICC/IF images (A30630 caption; HPA subcellular record). Multiplex CST1 with an independently validated glandular cell marker when testing salivary gland sections, because HPA reports staining in a subset of glandular cells (HPA tissue IHC). Choose a fluorophore channel with low tissue autofluorescence, include single stain and primary omission controls, and compare channels before assigning colocalisation (standard IF practice). CST1 has a signal peptide and no transmembrane segment; use permeabilisation only when assessing an intracellular epitope, and validate its effect empirically for IF (UniProt P01037 processing and topology; standard IF practice).
What should I check when chromogenic CST1 staining is diffuse?
Start with a primary antibody omission control and examine whether the chromogen appears in tissue compartments without convincing cellular morphology (standard IHC practice). Block endogenous peroxidase for a peroxidase based detection system, then check secondary reagent background and wash conditions under the same DAB development time (standard IHC practice). A secreted protein may appear beyond its producing cells, so extracellular signal alone does not prove nonspecific staining (UniProt P01037 subcellular location; HPA reliability description). Compare the distribution with the expected salivary gland subset and inspect adipocytes or other HPA reported negative cells as contextual controls, while accounting for possible recognition of proteins from more than one gene (HPA tissue IHC and reliability description).
How should I quantify CST1 across paraffin sections? ⚠ ANSWER MARKED FOR VERIFICATION
Define the region and eligible cell population before scoring, and keep staining, imaging and threshold settings constant across sections (standard IHC practice). For cellular staining, report the percentage of positive glandular cells and an H score based on intensity categories 0–3, stating the scoring rule and normalising to the number of evaluable cells (standard IHC practice). If the question concerns extracellular deposits, measure positive area or signal density per mm² of viable tissue separately from the cellular score (standard IHC practice; UniProt P01037 subcellular location: secreted). Report tissue identity and sampling because HPA describes cytoplasmic staining in only a subset of salivary gland cells (HPA tissue IHC).
When is a positive CST1 IHC result credible?
A credible cellular result has interpretable morphology, signal above matched controls, and a distribution assessed against the expected glandular cell subset in salivary gland (standard IHC practice; HPA tissue IHC). CST1 is secreted, so extracellular staining can be biologically plausible, but a nuclear or membrane only pattern needs further validation because neither location is annotated for this protein (UniProt P01037 subcellular location and topology). Discount staining confined to section edges, necrotic areas or sites with signal in the primary omission control; check endogenous peroxidase when using DAB (standard IHC practice). The peptide blocked colon carcinoma image offers an assay control, while HPA warns that its tissue staining can reflect protein from more than one gene; neither observation establishes molecular specificity alone (A30630 caption; HPA reliability description).
Boster reagents
Best CST1 / Cystatin-SN IHC Antibodies
The catalog antibody A30630 has IHC data from human colon carcinoma paraffin sections and IF data from MCF7 cells (image captions); its listed reactivity is human, mouse and rat (catalog).
Real IHC data
Anti-CST1/Cystatin Sn Antibody
Cat # A30630
A30630 will render with an IHC image of human colon carcinoma paraffin sections, including a peptide-blocked comparison (IHC image caption). The catalog lists IHC, IF and ICC applications and human, mouse and rat reactivity; its IF image shows MCF7 cells with a peptide-blocked comparison (catalog; IF image caption).
Which to pick: Choose A30630 for paraffin-section IHC because its own IHC image shows human colon carcinoma paraffin sections; the fixative is unreported (IHC image caption). Choose A30630 for IF/ICC because both applications are listed and its IF image shows MCF7 cells (catalog; IF image caption). For mouse or rat samples, A30630 has listed reactivity, although the supplied IHC and IF images show human samples (catalog; image captions).
Each figure is that product's own IHC / IF validation image from its datasheet.
References
- UniProt Consortium. UniProt entry P01037 (CYTN_HUMAN, Cystatin-SN).
- Human Protein Atlas. CST1 tissue IHC expression (reliability: Enhanced).
- Human Protein Atlas. CST1 subcellular location (ICC-IF): Secreted.
- Human Protein Atlas. CST1 antibody validation summary (3 antibodies).
- Prognostic significance of cystatin SN associated nomograms in patients with colorectal cancer. Oncotarget 2017 — PMC5777761.
- Combination of serum CST1 and HE4 for early diagnosis of endometrial cancer. PeerJ 2023 — PMC10704982.
- Cystatin SN upregulation in patients with seasonal allergic rhinitis. PloS one 2013 — PMC3741298.
- Upregulation of cystatin SN promotes hepatocellular carcinoma progression and predicts a poor prognosis. Journal of cellular physiology 2019 — PMC6767558.
- PubMed PMID:3446578 — UniProt-cited evidence.
- PubMed PMID:2837486 — UniProt-cited evidence.
- PubMed PMID:11780052 — UniProt-cited evidence.
Immunohistochemistry protocol sheet for CST1 (Cystatin-SN). Expected localisation Cytoplasm in a subset of salivary gland cells (HPA tissue IHC). Antigen retrieval: Citrate pH 6.0 HIER, 95–98 °C, 20 min (rule: cytoplasmic / membrane antigen). Validated IHC antibody: A30630 at 1:100 - 1:300 (the product's own IHC validation image is shown). Controls (HPA): positive Salivary gland (Glandular cells); negative Adipose tissue. IHC-P workflow on paraffin sections; fixative unspecified. Protocol steps: 1. Sample: Paraffin-embedded human colon carcinoma tissue; fixative not specified (datasheet A30630); 2. Fixation: Image fixative and duration unreported (datasheet A30630); 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-induced epitope retrieval in citrate buffer, pH 6.0 , 20 min at 95–98 °C…; 6. Peroxidase block: 3% H2O2, 10 min , room temperature (standard); 7. Blocking: 10% normal serum of the secondary host, 30 min , room temperature (standard); 8. Primary antibody: Rabbit anti-CST1, 1:100 - 1:300 (datasheet A30630); 9. Primary incubation: Overnight at 4 °C (standard). Watch for: Fixation: Keep fixation consistent across sections (standard IHC practice; not target-specific); Caveat: Secretion may separate protein staining from RNA location (HPA tissue IHC); Isoform / epitope: No isoforms; mature chain 21–141 has no TM epitope split (UniProt); Regulation: Salivary gland-enriched RNA (HPA tissue RNA). Evidence: UniProt P01037, HPA tissue IHC · Enhanced, HPA ICC-IF · Secreted, Datasheet A30630, PMC5777761, PMC6767558. QR code links to https://www.bosterbio.com/bosterbio-gene-info-cards/CST1/immunohistochemistry-ihc-guide.