GPX2 (HMV301)

The Glutathione peroxidase 2 (GPX2) is a selenium-dependent glutathione peroxidase coded by the GPX2 gene on 14q24.1. GPX2 is one out of eight known glutathione peroxidases (Gpx1-8) in humans. GPX2 has a major role in removing potentially harming reactive oxygen species (ROS) from cells by catalyzing the reduction process of hydrogen peroxide to water. GPX2 expression is restricted to few tissues and it is preferentially expressed in the gut where it makes up for about 50% of the total GPx activity. Studies in mice indicate that GPX2 mRNA levels respond to changes in the luminal microflora, suggesting a role of the ileal glutathione peroxidases in preventing inflammation in the GI tract. Mice that lack both GPX1 and GPX2 develop ileocolitis. GPX2 may also be involved in the control of apoptosis. GPX2 has a yet insufficiently understood role in cancer. Its level of expression was described to be prognostic in several cancer types including bladder, nasopharyngeal and prostate cancer. In hepatocellular carcinomas, GPX2 levels markedly affected the lenvatinib-induced ROS levels and apoptosis in HCC cells and also predicted response to lenvatinib therapy in clinical patients (36725188).

Images describing the GPX2 staining pattern in normal tissues obtained by the antibody HMV301 are shown in our “Normal Tissue Gallery”.

Cyclin E1 staining was always nuclear. A particularly strong Cyclin E1 positivity in a large fraction of cells occurred in chorion cells, cytotrophoblast cells, and decidua cells of the placenta, epithelial cells of proliferating endometrium, superficial cell layers of the urothelium and squamous epithelium (especially skin and tonsil). A weak to moderate staining was also seen in epithelial cells of the adrenal cortex and of the parathyroid gland. A faint to weak to moderate Cyclin E1 staining could further be observed in virtually every tissue in cell types/tissue areas with proliferative activity. These for example included tissues with inflammation or reparation, crypt cells in the intestine, neck cells of the stomach mucosa, lymphocytic cells in germinal centres or the thymus, spermatocytes of the testis, amnion cells, and hematopetic cells of the bone marrow. A particular strong Cyclin E1 occurred in chorion cells, cytotrophoblast cells, and decidua cells of the placenta, epithelial cells of proliferating endometrium, superficial cell layers of the urothelium and squamous epithelium (especially skin and tonsil). Tissues with particularly low or absent Cyclin E1 expression included, skeletal and heart muscle, the brain, pituitary gland, thyroid, prostate, seminal vesicle, epididymis, kidney, breast, endocervix, fallopian tube, lung, respiratory epithelium.

The findings described above are thus consistent with the RNA data described in the Human Protein Atlas (Tissue expression GPX2). GPX2 staining by HMV301 is most prominent in tissues from the gastrointestinal tract but also occurs – at lower levels – in various other tissues.

Positive control = Colon: A strong GPX2 staining should be seen in epithelial cells (predominantly in the crypt base).

Negative control = Colon: Stroma cells, inflammatory cells, and smooth muscle cells must be GPX2 negative.

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 HMV301 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 and prognostic relevance of GPX2 expression in tumors and in preneoplastic disease needs to be investigated.
• GPX2 may serve as a therapeutic target. 

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 HMV301 specificity is suggested by the strong 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 in the Human Protein Atlas (Tissue expression GPX2)

GPX2 positivity by HMV301 is strongest in the tissues with highest documented GPX2 RNA expression (stomach, duodenum, small intestine, appendix, colon, rectum, gallbladder, urinary bladder). That GPX2 staining is less intense in the liver where high RNA expression levels are also seen is explained by the fact that – in contrast to the intestine – nearly all liver cells (hepatocytes) express some GPX2 which may cause a high average level of GPX2 RNA in liver tissue. GPX2 positivity by HMV301 is also detectable in the tissues with lower level GPX2 RNA expression (skin, ectocervix, esophagus, salivary glands, pancreas, prostate, seminal vesicles). Moreover, GPX2 staining by HMV301 is lacking in most tissues not showing RNA expression (spleen, lymph node, bone marrow, thymus, tonsil, skeletal muscle, heart muscle, placenta, breast, fallopian tube, ovary, endometrium, testis, endocrine organs, brain). The few tissues without previously documented GPX2 RNA expression but GPX2 positivity by HMV301 had either very few positive cells that were probably not detected in RNA studies (basal cells of the cauda epididymis) or were previously not analyzed on the RNA level (respiratory epithelium).

Comparison of antibodies: True expression of GPX2 in all cell types found GPX2 positive by HMV301 (including basal cells of the cauda epididymis and respiratory epithelium) is corroborated by identical stainings obtained by another commercially available independent antibody (termed “validation antibody”). The additional staining of nuclei of various tissues (for example: pneumocytes, chorion cells and trophoblastic cells of the placenta, pituicytes of the neurohypophysis) by the “validation antibody” demonstrates the independence of the validation antibody. 

Normal tissue gallery