Prostein (MSVA-460R)

Prostein (P501S), also termed solute carrier family 45 member 3 (SLC45A3) is a 553 amino acid protein encoded by the SLC45A3 gene located at chromosome 1q32-q42. Prostein is predominantly expressed in the prostate. Its expression is androgen regulated but its function is unknown. In prostate cancer, prostein acts as the second most common 5′ partner gene in ERG rearrangements. In the brain, prostein is involved in the regulation of the lipid metabolism of oligodendrocytes and myelin.

Prostein staining is always granular, cytoplasmic and predominantly perinuclear (endoplasmatic reticulum pattern). It is particularly strong in acinar cells of the prostate and occurs at lesser intensity in other cell types (shown below).
Images describing the Prostein staining pattern in normal tissues obtained by the antibody MSVA-460R are shown in our “Normal Tissue Gallery”.

RNA and protein expression data of prostein findings are also described in the Human Protein Atlas (Tissue expression Prostein).

Positive control = Stomach mucosa: At least a moderate, granular, cytoplasmic prostein positivity should be seen in surface epithelial cells.

Negative control = Stomach mucosa: Prostein immunostaining should be absent in gastric glands.

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 MSVA-460R 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 utility of prostein for assuring a prostatic origin of cancer should be evaluated as compared to other prostate markers such as PSA and PSMA.
• The prognostic role of different levels of prostein expression in prostate cancer should be investigated.
• Given the expression of prostein in few non-prostatic tissues, its expression in corresponding tumors would be of interest.
• The function of prostein is unclear.
• The utility of prostein as a therapeutic target should be evaluated.

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-460R 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 Prostein). The strongest immunostaining by MSVA-460R is seen in the prostate, the organ, with the highest documented RNA expression level. Immunostaining by MSVA-460R was also observed in distinct cell populations of other organs with documented low level RNA expression such as the stomach, respiratory epithelium, hypophysis, spleen, and the brain. Only RNA expression in the liver could not be corroborated by MSVA-460R.

Comparison of antibodies: Specific prostein staining by MSVA-460R in a fraction of islet cells of the pancreas, respiratory epithelium (a tissue for which published RNA data are lacking), epithelial cells of the adenohypophysis, surface epithelial cells of the stomach, some glia cells in the brain, and some (probably monocytic) cells in the spleen and (less frequently) in lymph nodes was corroborated by comparison with a commercially available independent second antibody (termed “validation antibody”) showing identical stainings. 

Normal tissue gallery