Fli-1

Fli-1 protein, a member of the ETS family of DNA binding transcription factors, is involved in cellular proliferation and tumorigenesis. Approximately 90% of Ewing’s Sarcoma/Primitive Neuroectodermal Tumors (ES/PNET) have a specific translocation, t(11;22)(q24;q12), which results in fusion of EWS to Fli-1, and production of an EWS-Fli-1 fusion protein, which can be detected by this antibody. Among normal tissues only endothelial cells and small lymphocytes express Fli-1. Fli-1 has been found to be expressed in the great majority of vascular tumors including Angiosarcomas, Hemangioendotheliomas, Hemangiomas, and Kaposi’s Sarcomas.

It has been reported that the high sensitivity and specificity of Fli-1 is equal to or exceeds that of the established vascular markers, CD31, CD34, and Factor VIII. As the first nuclear marker of endothelium (rather than cytoplasmic or membranous), Fli-1 immunostaining also generally lacks cytoplasmic staining artifacts that are the result of endogenous peroxidases or biotin.

Fli-1 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.

1. Folpe AL, et al. Am J Surg Pathol. 2001;25(8):1061-6
2. Mhawech-Fauceglia P, et al. Histopathology. 2006;Dec;49(6):569-75
3. Folpe AL, et al. Am J Surg Pathol. 2000;Dec;24(12):1657-62

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.