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Product details

Synonyms = BDMF; DMSFH; DMSMFH; Epididymis luminal protein 249; HEL249; LGMBF; MeSAdo phosphorylase; Methylthioadenosine phosphorylase; MSAP; MTA phosphorylase; MTAPase; S- methyl-5”-thioadenosine phosphorylase

Antibody type = Recombinant Rabbit monoclonal / IgG

Clone = MSVA-741R

Positive control = Ovary: At least a moderate, nuclear and/or cytoplasmic MTAP staining should be seen in ovarian stroma cells.

Negative control = Bladder cancer with homozygous 9p deletion: MTAP staining should be absent in cells from urothelial tumors with homozygous 9p deletion.

Cellular localization = Nuclear

Reactivity = Cytoplasmic

 

 

Application = Immunohistochemistry
Dilution = 1:50
Intended Use = Research Use Only

Relevance of Antibody

MTAP is a Sensitive and specific marker for homozygous 9p21 deletions.

Biology Behind

S-methyl-5′-thioadenosine phosphorylase (MTAP) is an enzyme with a major role in polyamine metabolism. It supports the recovery of both adenine and methionine by catalyzing the phosphorylation of methylthioadenosine (MTA) to adenine and 5-methylthioribose-1-phosphate. Adenine is one of the purine bases required for both DNA and RNA. As an essential protein for the adenine synthesis in human cells, MTAP plays a critical indirect role for the synthesis of DNA and RNA. The MTAP gene is located at 9p21.3. This is in the immediate vicinity of the CDKN2A gene which is homozygously deleted in about 15% of all human cancers. Homozygous co-deletion of MTAP occurs in 80%–90% of tumors with CDKN2A deletion. MTAP deletion have a significant impact on purine biosynthesis because the MTAP substrate MTA accumulates in affected cells and inhibits PRMT5. As a result critical vulnerabilities of affected cells to targeting of the MAT2A/PRMT5/RIOK1 axis develop. Inhibitors of these enzymes are now being tested in clinical trials recruiting patients with homozygously 9p21 deleted and MTAP inactivated tumors.

Staining Pattern in Normal Tissues

Images describing the MTAP staining pattern in normal tissues obtained by the antibody MSVA-741R are shown in our “Normal Tissue Gallery”.

Brain Cerebrum Faint to moderate staining in small blood vessels and in some glia cells.
Cerebellum Faint to moderate staining in small blood vessels and in some glia cells.
Endocrine Tissues Thyroid Moderate to strong nuclear and cytoplasmic MTAP positivity of epithelial cells.
Parathyroid Weak to moderate, predominantly cytoplasmic MTAP positivity of epithelial cells.
Adrenal gland Moderate to strong nuclear and cytoplasmic MTAP positivity of epithelial cells.
Pituitary gland Weak to strong, predominantly cytoplasmic MTAP positivity of a subset of epithelial cells. Weak, predominantly cytoplasmic MTAP staining of pituicytes of the neurohypophysis.
Respiratory system Respiratory epithelium Variable, weak to strong nuclear and cytoplasmic MTAP positivity of respiratory epithelial cells and of bronchial gland cells.
Lung Weak to moderate, predominantly nuclear MTAP positivity of alveolar cells.
Gastrointestinal Tract Salivary glands Variable, weak to strong nuclear and cytoplasmic MTAP positivity of epithelial cell types.
Esophagus Cytoplasmic and nuclear MTAP positivity of variable intensity in squamous epithelium. Staining intensity is highest in the basal cell layers and decreases towards the surface cell layers.
Stomach Weak to moderate, predominantly cytoplasmic MTAP positivity of gastric epithelium.
Duodenum Weak, predominantly cytoplasmic MTAP positivity of epithelial cells. Staining is best visible at the base of crypts. Moderate to strong nuclear MTAP positivity of mucin producing cells in Brunner glands.
Small intestine Weak, predominantly cytoplasmic MTAP positivity of epithelial cells. Staining is best visible at the base of crypts.
Appendix Weak, predominantly cytoplasmic MTAP positivity of epithelial cells. Moderate to strong, predominantly cytoplasmic MTAP positivity of the majority of lymphocytes, mostly in the interfollicular area.
Colon Weak to moderate, predominantly cytoplasmic MTAP positivity of epithelial cells, especially seen at the base of crypts.
Rectum Weak to moderate, predominantly cytoplasmic MTAP positivity of epithelial cells, especially seen at the base of crypts.
Liver Weak to moderate, cytoplasmic and nuclear MTAP positivity of intrahepatic bile ducts. Staining is weak or absent in hepatocytes.
Gallbladder Weak to moderate, predominantly nuclear MTAP positivity of epithelial cells, especially seen in crypts.
Pancreas Weak to moderate, nuclear and cytoplasmic MTAP positivity of epithelial cells. Staining is stronger in acinar cells than in islet cells.
Genitourinary Kidney Weak to strong, nuclear and cytoplasmic MTAP positivity of tubular and collecting duct cells.
Urothelium Weak to strong, nuclear and cytoplasmic MTAP positivity of all urothelial cells.
Male genital Prostate Weak to moderate, predominantly cytoplasmic MTAP positivity of epithelial cells.
Seminal vesicles Moderate, predominantly cytoplasmic MTAP positivity of epithelial cells.
Testis Strong, nuclear and cytoplasmic MTAP positivity of spermatogonia. Weak MTAP staining of other intratubular cells. Moderate positivity of Leydig cells.
Epididymis Strong, predominantly cytoplasmic MTAP positivity of epithelial cells in the corpus. Staining is less intense (but still moderate) in the cauda.
Female genital Breast Moderate to strong, nuclear and cytoplasmic MTAP positivity of luminal epithelial cells. Staining is somewhat less intensive in basal/myoepithelial cells.
Uterus, myometrium Weak, nuclear and cytoplasmic MTAP positivity of muscle cells.
Uterus, ectocervix Cytoplasmic and nuclear MTAP positivity of variable intensity. Staining intensity is highest in the basal cell layers and decreases towards the surface cell layers.
Uterus endocervix Weak, predominantly nuclear MTAP positivity of epithelial cells.
Uterus, endometrium Weak to moderate, predominantly cytoplasmic MTAP positivity of epithelial cells while staining is only faint in the stroma.
Fallopian Tube Moderate to strong, nuclear and cytoplasmic MTAP positivity of a subset of epithelial cells.
Ovary Moderate to strong, nuclear and cytoplasmic MTAP positivity of stromal, theca interna, and granulosa cells.
Placenta early Moderate to strong, nuclear and cytoplasmic MTAP positivity of cytotrophoblast cells. Staining is markedly less intense in the syncytiotrophoblast and in the stroma.
Placenta mature Moderate to strong, nuclear and cytoplasmic MTAP positivity of cytotrophoblast cells. Staining is markedly less intense in the syncytiotrophoblast and in the stroma.
Amnion Weak, nuclear and cytoplasmic MTAP positivity of amnion cells.
Chorion Moderate to strong, nuclear and cytoplasmic MTAP positivity of amnion cells.
Skin Epidermis Predominantly nuclear MTAP positivity of variable intensity. Staining intensity is highest in the basal cell layers and decreases towards the surface cell layers.
Sebaceous glands Weak to moderate, nuclear MTAP positivity of cells.
Muscle/connective tissue Heart muscle Faint nuclear MTAP positivity of some muscle cells.
Skeletal muscle Weak to moderate, nuclear MTAP positivity of some muscle cells.
Smooth muscle Weak to moderate, nuclear and cytoplasmic MTAP positivity of muscle cells.
Vessel walls Moderate MTAP positivity in muscle cells of the media.
Fat Faint nuclear MTAP positivity of some fat cells.
Stroma Weak to moderate, nuclear and cytoplasmic MTAP positivity of many cells.
Endothelium Weak to moderate (sometimes also strong), nuclear and cytoplasmic MTAP positivity of some muscle cells.
Bone marrow/ lymphoid tissue Bone marrow Weak to moderate, nuclear and cytoplasmic MTAP positivity of some cells.
Lymph node Moderate to strong, predominantly cytoplasmic MTAP positivity of the majority of lymphocytes, mostly in the interfollicular area.
Spleen Moderate to strong, predominantly cytoplasmic MTAP positivity of inflammatory cells, especially in the white pulp.
Thymus Moderate, predominantly cytoplasmic MTAP positivity of the majority of lymphocytes.
Tonsil In the squamous epithelium, a variable, predominantly nuclear MTAP is strongest in the basal cell layers and decreases towards the surface. Moderate to strong, predominantly cytoplasmic MTAP positivity of the majority of lymphocytes, mostly in the interfollicular area.
Remarks

 

The ubiquitous staining of MTAP across all tissue types is largely consistent with the RNA data described in the Human Protein Atlas (Tissue expression MTAP).

 

Positive control = Ovary: At least a moderate, nuclear and/or cytoplasmic MTAP staining should be seen in ovarian stroma cells.

Negative control = Bladder cancer with homozygous 9p deletion: MTAP staining should be absent in cells from urothelial tumors with homozygous 9p deletion.

 

 

Normal tissue gallery

Staining Pattern in Relevant Tumor Types

Complete loss of MTAP expression occurs in a fraction of cases in urothelial dysplasia, urothelial cancer, malignant mesotheliomas, as well as – less commonly – in various other tumor entities.

The TCGA findings on MTAP RNA expression in different tumor categories have been summarized in the Human Protein Atlas.

 

 

Cancer tissue gallery

Compatibility of Antibodies

No data available at the moment

Protocol Recommendations

IHC users have different preferences on how the stains should look like. Some prefer high staining intensity of the target stain and even accept some background. Others favor absolute specificity and lighter target stains. Factors that invariably lead to more intense staining include higher concentration of the antibody and visualization tools, longer incubation time, higher temperature during incubation, higher temperature and longer duration of the heat induced epitope retrieval (slide pretreatment). The impact of the pH during slide pretreatment has variable effects and depends on the antibody and the target protein.

 

All images and data shown here and in our image galleries are obtained by the manual protocol described below. Other protocols resulting in equivalent staining are described as well.

 

Manual protocol

Freshly cut sections should be used (less than 10 days between cutting and staining). Heat-induced antigen retrieval for 5 minutes in an autoclave at 121°C in pH 7,8 Target Retrieval Solution buffer. Apply MSVA-741R at a dilution of 1:50 at 37°C for 60 minutes. Visualization of bound antibody by the EnVision Kit (Dako, Agilent) according to the manufacturer’s directions.

Potential Research Applications

  • The diagnostic utility of MTAP immunohistochemistry in tumors and in preneoplastic disease needs to be investigated. 
  • The prognostic relevance of MTAP expression in tumors should be explored. 
  • The predictive role of homozygous and heterozygous MTAP deletions for cancer treatment by drugs targeting the MAT2A/PRMT5/RIOK1 axis needs to be evaluated.

Evidence for Antibody Specificity in IHC

There are two ways how the specificity of antibodies can be documented for immunohistochemistry on formalin fixed tissues. These are: 1. Comparison with a second independent method for target expression measurement across a large number of different tissue types (orthogonal strategy), and 2. Comparison with one or several independent antibodies for the same target and showing that all positive staining results are also seen with other antibodies for the same target (independent antibody strategy). 

 

Orthogonal validation: For the antibody MSVA-741R orthogonal validation is not suited due to the ubiquitous expression of the protein. Ubiquitous MTAP protein expression is consistent, however, with data from three independent RNA screening studies, including the Human Protein Atlas (HPA) RNA-seq tissue dataset, the FANTOM5 project, and the Genotype-Tissue Expression (GTEx) project, which are all summarized in the Human Protein Atlas (Tissue expression MTAP)

Comparison of antibodies: True MTAP protein expression in all cell types found by MSVA-741R is corroborated by identical stainings obtained by another commercially available independent antibody (termed “validation antibody”).  – Images coming soon

 

Normal tissue gallery