CD56 (MSVA-056R)

Neural cell adhesion molecule (NCAM; CD56), is a glycoprotein of the Immunoglobulin (Ig) superfamily coded by the NCAM gene on chromosome 11q23. At least 27 NCAM isoforms exist. CD56 appears on early embryonic cells where it contributes to cell-cell adhesion and cell-matrix adhesion and supports the formation of cell aggregates at several sites of morphogenesis. Later in development, CD56 expression is found on various differentiated tissues. In nerves, CD56 regulates neurite outgrowth and interactions between neurons and between neurons and muscle in collaboration with fibroblast growth factor receptor (FGFR). During hematopoiesis, CD56 is the prototypic marker of NK cells, also present on a subset of CD4+ T cells and CD8+ cells. NCAM has also been used as a target molecule for experimental antibody-based immunotherapy. Successful radio-immunolocalization of metastases was demonstrated by using NCAM-binding 123J-UJ13a and 131J-UJ13a radio-immunoconjugates in neuroblastoma patients. Patients with small cell lung cancer were treated with the anti-NCAM immunotoxin huN901-DM1 in two different clinical studies, revealing acceptable toxicity and signs of clinical response.

Images describing the CD56 staining pattern in normal tissues obtained by the antibody MSVA-056R are shown in our “Normal Tissue Gallery”.

These findings are largely consistent with the RNA data described in the Human Protein Atlas (Tissue expression CD56)

In particular, CD56 immunostaining was absent in all organs lacking RNA expression such as parathyroid gland, placenta, fat, and the skin. 

Positive control = Tonsil: A small subset of (mainly interfollicular) lymphocytes should show a moderate to strong CD56 immunostaining. A weak to moderate staining can also be seen in fibroblastic reticular cells.

Negative control = Tonsil: Epithelial cells and the vast majority of lymphocytes should not show any CD56 immunostaining.

Normal tissue gallery

Tumors that have been reported as CD56-positive for example include neuroendocrine tumors, neuroblastoma, osteosarcoma, chondrosarcoma, NK/T-cell lymphoma, pheochromocytoma, paraganglioma, small cell lung carcinoma, and the Ewing’s sarcoma family of tumors.

The TCGA findings on CD56 RNA expression in different tumor categories have been summarized in the Human Protein Atlas. These data suggest the occurrence of CD56 expression in head and neck, urothelial, lung, cervical, stomach, and renal cancer.

Cancer tissue gallery

It is important to understand that the data on CD56 provided in this product information are specific to the antibody MSVA-056R.

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-056R 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 clinical and biological significance of CD56(bright) NK cells requires further investigation.
• The role of CD56 as a therapeutic target is under investigation.
• The role of endometrial (CD56 positive) natural killer cells is unclear.

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-056R 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 in the Human Protein Atlas (Tissue expression CD56). Immunostaining by using MSVA-056R was detected in all organs and cell types with documented RNA expression. In contrast, CD56 immunostaining was absent in all organs lacking RNA expression such as parathyroid gland, placenta, breast gland, fat, and the skin. However, because CD56 staining is often limited to specific cell types of organs, orthogonal validation is not sufficient for CD56 antibody validation.

Comparison of antibodies: True expression of CD56 in cell types with documented CD56 immunostaining by MSVA-056R is validated by identical staining obtained by a second, independent commercially available CD56 antibody, termed “validation antibody” for the vast majority of tissues. The only exceptions were the membranous staining along heart muscle cells and a focal cytoplasmic staining of skeletal muscle which was not seen by the validation antibody. Heart muscle staining is thus considered a (tolerable) cross-reactivity of MSVA-056R. The respective images are shown below.

Normal tissue gallery