PSMA

PSMA, prostate specific membrane antigen, is a Type 2 integral membrane glycoprotein found in prostate and a few other tissues. Three functionally-distinct proteins are encoded, including folylpoly-gamma-glutamate carboxypeptidase in the intestine, N-acetylated alpha-linked acidic dipeptidase 1 in the brain and prostatespecific membrane antigen in the prostate. A mutation in the intestinal form may be associated with impaired intestinal absorption of dietary folates, resulting in low blood folate levels and consequent hyperhomocysteinemia. The form expressed in the brain may be involved in a number of pathological conditions associated with glutamate cytotoxicity. The prostate form is up-regulated in cancerous cells and is used as an e ective diagnostic and prognostic indicator of prostate cancer. This gene likely arose from a duplication event of a nearby chromosomal region. Alternative splicing gives rise to multiple transcript variants.

Although PSMA expression is highest in the prostate, detectable levels of protein are also found in the small intestine and the brain. PSMA is expressed in prostate cancer cells as a noncovalently associated homodimer. Using a secreted form of the protein, it has been demonstrated that the extracellular domain is sufficient for dimerization and that dimerization is required for enzymatic activity. When used as an immunogen, dimeric (but not monomeric) PSMA is capable of efficiently eliciting antibodies that recognize PSMA-expressing tumor cells. It is a possible therapeutic target for prostate cancer and it is being used (with radioactive antibodies) to image prostate tissue.

PSMA is a rabbit 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. Schülke N, et al. PNAS. 2003;100(22):12590-12595
2. Elsasser-Beile U, et al. JNM. 2009;50:606-611
3. Henry MD, et al. Cancer Res. 2004;64:7995-8001

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.