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 = Intracellular
Reactivity = Human
Application = Immunohistochemistry
Dilution = 1:50 – 1:100
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.
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.
Compatibility of Antibodies
MTAP (MSVA-741R) publication summary
Relevant publication: Gorbokon et al. “Prevalence of S-methyl-5′-thioadenosine Phosphorylase (MTAP) Deficiency in Human Cancer: A Tissue Microarray Study on 13,067 Tumors From 149 Different Tumor Types” Published in Am J Surg Pathol. 2024 Aug 12. Epub ahead of print. PMID: 39132873.
A total of 13’067 tumors from 149 different tumor categories were successfully analyzed in a Dako Omnis automated stainer (Agilent Technologies) using the EnVision FLEX, high pH Kit (Agilent Technologies, #GV800). Slides were deparaffinized with clearify agent (Agilent Technologies, #GC810) and exposed to heat-induced antigen retrieval for 30 minutes at 97 °C in target retrieval solution, high pH reagent (part of Agilent kit #GV800). Primary antibody specific for MTAP (recombinant rabbit monoclonal, MSVA-741R, MS Validated Antibodies GmbH, #5293-741R) was applied at ambient temperature for 30 minutes at a dilution of 1:50. Visualization of bound antibody by the EnVision Kit (Dako, Agilent). This protocol was also used for all stainings depicted in our tumor and normal tissue galleries.
An MTAP loss was observed in 83 of 149 tumor categories. It was most common in neuroendocrine neoplasms (up to 80%), Hodgkin lymphoma (50.0%), mesothelioma (32.0% to 36.8%), gastro-intestinal adenocarcinoma (up to 40.5%), urothelial neoplasms (10.5% to 36.7%), squamous cell carcinomas (up to 38%), and various types of sarcomas (up to 20%) and non-Hodgkin lymphomas (up to 14%). The complete results are shown in an “organ-systematic” (Figure 1) and in a “ranking order” figure (Figure 2) below (images based on data from Gorbokon et al). Data on associations with histopathological and clinical parameters are also summarized below (Table 3; based on data described by Gorbokon et al).
Authors conclusions on diagnostic utility of MTAP IHC with respect to the distinction of benign versus malignant (Gorbokon et al.):
- MTAP expression loss is an indicator of neoplastic transformation in many tissue types, including mesothelium, urothelium, pancreas, lung, soft tissues, melanocytes, and various others.
Authors conclusions on diagnostic utility of MTAP IHC with respect to the distinction of different tumor entities (Gorbokon et al.):
- not applicable
Authors conclusions on the prognostic/predictive role of MTAP IHC results (Gorbokon et al.):
- MTAP deficiency was associated with BRE grade in breast cancer (p<0,05).
- MTAP deficiency may indicate a critical vulnerability of cells towards drugs targeting several different pathways.
Figure1. MTAP loss in tumors (“loss categories specific” ; according to Gorbokon et al.”) with antibody MSVA-741R
Figure2. MTAP loss in tumors (“loss ranking order ” ; according to Gorbokon et al.”) with antibody MSVA-741R
Table1. “Clinical data summary” based on the data obtained by Gorbokon et al.
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 1:75 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”).
