TYMS (HMV305)

Thymidylate synthase (TS, TYMS) is a 32-35kD enzyme which is coded by the TYMS gene at 18p11.32. TYMS catalyzes the conversion of deoxyuridine monophosphate (dUMP) to deoxythymidine monophosphate (dTMP) which is one of the nucleotides forming the DNA. TYMS is essential for DNA synthesis because it represents the only de novo pathway for production of thymidine and it also is the only enzyme in folate metabolism that can oxidize the 5,10-methylenetetrahydrofolate during one-carbon transfer. Therefore, TYMS is critical for regulating the supply of all 4 DNA precursors for DNA replication. In-vitro studies have shown that upregulation of TYMS is sufficient to transform immortalized mammalian cells to a malignant phenotype. TYMS is an important target for several chemotherapeutic drugs including 5-fluorouracil (5-FU). It has been suggested that tumors with low-levels of TYMS may show to a better response to 5-FU than those with high-level expression. In normal tissues, TYMS expression is ubiquitous but too low for detection by immunohistochemistry in most tissues. TYMS expression is highest in thymus, bone marrow, tonsil, lymph nodes and the testis. Among cancers, TYMS expression is highly variable between individual tumors. At least in a fraction of tumors, high TYMS expression occurs in a broad range of different tumor entities.

Images describing the TYMS staining pattern in normal tissues obtained by the antibody HMV305 are shown in our “Normal Tissue Gallery”.

In normal tissues, TYMS expression is ubiquitous but too low for detection by immunohistochemistry in most tissues. TYMS expression is highest in thymus, bone marrow, tonsil, lymph nodes and the testis. These findings are largely consistent with the RNA data described in the Human Protein Atlas (Tissue expression TYMS). 

Positive control = Lymph node: A strong TYMS staining should be seen in a fraction of lymphocytic cells, especially in germinal centres.

Negative control = Prostate: TYMS staining should be absent in normal epithelial cells.

Normal tissue gallery

Cancer tissue gallery

No data available at the moment

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 HMV305 at a dilution of 1:150 at 37°C for 60 minutes. Visualization of bound antibody by the EnVision Kit (Dako, Agilent) according to the manufacturer’s directions.

The diagnostic, prognostic, and predictive role of TYMS expression in tumors and in preneoplastic disease needs to be investigated.

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 HMV305 specificity is supported by the good concordance of the immunostaining data 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 the  Human Protein Atlas (Tissue expression TYMS). TYMS positivity by HMV305 is detectable at highest levels in these tissues with highest TYMS RNA expression (lymphatic and hematopoetic  tissues) and is also regularly seen in all tissues with low to intermediate TYMS RNA levels (gastrointestinal epithelium, placenta, testis, esophagus). Other tissues with low TYMS RNA levels (liver, kidney, urinary bladder) are often not found to show TYMS IHC positivity by HMV305 by using the described protocol. 

Comparison of antibodies: True expression of TYMS in all cell types found to be TYMS positive by HMV305 is eventually proven by identical staining’s obtained by another commercially available antibody (termed “validation antibody”). That this validation antibody additionally stained prostatic epithelium demonstrates independence of the validation antibody. Prostate staining of the reference antibody reflects an antibody specific cross-reactivity of the reference antibody.

Normal tissue gallery