Cyclin E1 (MSVA-898R)

Cyclin E1 is a 47 kDa protein coded by the CCNE1 gene at 19q12. It has 47% homology and largely overlapping functions with Cyclin E2. Similar to all cyclin family members, cyclin E1 binds to cyclin-dependent kinases, in particular CDK2. The cyclin E/CDK2 complex regulates various downstream proteins by phosphorylation and plays a critical role in the G1 phase and in the G1-S phase transition of the cell cycle. For example, cyclin E/CDK2 phosphorylates retinoblastoma protein (Rb) to promote G1 progression. As a result, hyper-phosphorylated Rb will no longer interact with E2F transcriptional factor and release it to promote expression of further genes needed for entering S phase. Other important cell cycle regulatory proteins phosphorylated by cyclin E/CDK2 include p27, p21, CBP/p300, p220(NPAT), and E2F-5. Independent of its role in cell cycle progression, cyclin E/CDK2 plays a role in the centrosome cycle. Cyclin E1 has been described to be overexpressed in cancers of various types. Cyclin E1 amplification, one of the mechanisms for overexpression, has been suspected to lead to synthetic lethality in combination with PKMYT1 kinase inhibition.

Images describing the MCM2 staining pattern in normal tissues obtained by the antibody MSVA-898R 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 Cyclin E1). The particularly high RNA expression levels in the placenta, the bone marrow, the testis, and the adrenal gland are consistent with IHC data obtained by MSVA-898R.

Positive control = Placenta: A strong Cyclin E1 staining should be seen in most cytotrophoblast cells.

Negative control = Normal kidney: Cyclin E1 staining should be largely absent in tubular and glomerular 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 MSVA-898R 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.

• The diagnostic and prognostic relevance of Cyclin E1 expression in tumors and in preneoplastic disease needs to be further investigated.
• The prevalence of Cyclin E1 overexpression in different tumor entities needs to be determined.
• The role of Cyclin E1 overexpression as a trigger for synthetic lethality in combination with PKMYT1 kinase inhibition must be further 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-898R 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 Cyclin E1). The particularly high RNA expression levels in the placenta, the bone marrow, the testis, and the adrenal gland are consistent with IHC data obtained by MSVA-898R as these tissues either contained cells with a very strong Cyclin E1 staining or a high density of cells with a weak to moderate Cyclin E1 staining. Orthogonal validation is, however, not optimal for validating antibodies for proteins that are ubiquitously expressed cell-cycle related proteins such as Cyclin E1.

Comparison of antibodies: True expression of Cyclin E1 in all cell types found Cyclin E1 positive by MSVA-898R is corroborated by identical stainings obtained by another commercially available independent antibody (termed “validation antibody”). The significant additional cytoplasmic staining obtained by the validation antibody in numerous cell types in various tissues demonstrates “independence” of the validation antibody.

Normal tissue gallery