Immunostaining XXXX paraffin-embedded sections for mismatch repair proteins.

@entity1 @entity6756 @entity124 @entity22694 @entity5 @entity4311 @entity14437 @entity982 @entity14
The loss of the function in any one of four @entity1 DNA mismatch repair genes, @entity4311 , @entity6756 , @entity22694 , and @entity14437 , is thought to lead to deficient mismatch repair (MMR) of DNA in the somatic cells leading to increased mutations and thereby @entity5 development. @entity124 ( @entity124 ) detected by PCR analysis has, to date, been the hallmark of loss of the function of these genes. Western and Northern blotting has confirmed the loss of MMR protein expression with @entity124 . However, this technique relies on fresh samples for DNA extraction and requires a normal tissue sample (see Chapter 41). Expression of MMR proteins can now be examined in both fresh and archival paraffin-embedded tissue samples by immunohistochemistry. This was first described for polyclonal @entity4311 antibody, in paraffin-embedded tissue, by Wilson et al. (1) and confirmed by Leach et al. (2), who showed that @entity4311 is highly expressed in the nuclei cells of the gastrointestinal epithelium that undergo rapid renewal in both the ileum, colon, and esophagus. Thibodeau et al. (3) examined @entity982 -embedded tissue from @entity14 for both @entity6756 and @entity4311 genes and function by DNA sequence analysis, @entity124 analysis by PCR, and immunohistochemistry. They showed that loss of immunohistochemical staining for these MMR proteins corresponded very closely with loss of function of these genes detected by microsatellite analysis. Of 19 @entity5 showing @entity124 , 14 had loss of either or both @entity6756 and @entity4311 immunostaining. Of @entity5 showing a germline mutation in either @entity6756 or @entity4311 , seven had a corresponding loss of immunostaining for the protein. Of 14 @entity5 showing a negative immunostain for one or both of @entity6756 and @entity4311 , all had @entity124 on PCR analysis and seven had a germline mutation in the DNA sequence of at least one of the MMR genes. Fink et al. (4) have performed immunohistochemistry for @entity6756 and @entity14437 on fresh frozen tissue sections. They confirmed a high nuclear expression in the epithelium of the digestive tract and in the testis and ovary. We describe here a method for immunohistochemistry for @entity4311 , @entity6756 , and @entity14437 in both fresh and paraffin-embedded material.
