Cytokeratin 20

Cytokeratin 20 (CK20) is a 46 kDa intermediate filament protein whose expression is restricted primarily to gastric and intestinal epithelium, urothelium, and Merkel cells. Cytokeratin 20 is a Type I cytokeratin. It is a major cellular protein of mature enterocytes and goblet cells found in the gastric and intestinal mucosa.

CK 20 is expressed in Adenocarcinomas of the colon, stomach, pancreas and biliary system. It is also expressed in Mucinous Ovarian Tumors, Transitional-cell Carcinomas of the urinary tract, and Merkel-cell Carcinomas. Cytokeratin 20 is useful in the differentiation of specific types of simple epithelial cells of the urinary tract and normal and malignantly-transformed epithelia. This antibody is essentially non-reactive in Squamous Cell Carcinomas and Adenocarcinomas of the Breast, Lung, and Endometrium, Non-mucinous Tumors of the Ovary, and Small-cell Carcinomas. This antibody is often used in conjunction with CK7 and other antibodies to distinguish Colon Carcinomas (CK20+) from Ovarian, Pulmonary, and Breast Carcinomas.

Cytokeratin 20 is a mouse monoclonal antibody derived from cell culture supernatant that is concentrated, dialyzed, filter sterilized and diluted in buffer pH 7.5, containing BSA and sodium azide as a preservative.

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1. Cut and mount 3-4 micron formalin-fixed paraffin-embedded tissues on positive charged slides.
2. Air dry for 2 hours at 58° C.
3. Deparaffinize, dehydrate and rehydrate tissues.
4. Subject tissues to heat epitope retrieval using a suitable retrieval solution such as ImmunoDNA Retriever with Citrate (BSB 0020-BSB 0023) or EDTA (BSB 0030-BSB 0033).
5. Any of three heating methods may be used:
   • Electric Pressure Cooker
     Place standoff rack at base of pressure cooker. Add 1-2 inches of distilled water to the pressure cooker and turn heat to high, and incubate for 15 minutes. Open and immediately transfer slides to room temperature.
   • Water Bath Method
     Place tissues/slides in a pre-warmed staining dish or coplin jar containing the ImmunoDNA Retriever with Citrate or EDTA in a water bath set at 95°-99° C. Incubate for 30-60 minutes.
   • Conventional Steamer Method
     Place tissues/slides in a pre-warmed staining dish or coplin jar containing the ImmunoDNA Retriever with Citrate or EDTA in a Steamer, cover and steam for 30-60 minutes.
6. After heat treatment, transfer slides in ImmunoDNA Retriever with Citrate or EDTA to room temperature and let stand for 15-20 minutes.
7. Wash slides with IHC wash buffer or DI water.
8. Continue IHC staining protocol.