Melissa and interested others:    k-ras (lower case letters) and h-ras (lower case letters) are genes that encode signal transduction proteins. The normal function of these genes produces products (proteins) that allow the cell to react appropriately to stimuli through G-protein coupled receptors. In some cancers, mutations have occurred in these genes that lead to (1) altered gene products (proteins) or (2) loss of functional proteins. These errors can (1) alter cell proliferation, (2) cell function or (3) repress expression of tumor suppressor genes. Any of these genetic alterations alone or in combination, are believed to contribute to the malignant transformation of cells and/or the promotion of malignant cell proliferation. That being said, one can look for either the gene or it's protein product in tissue but using completely different methods.

 

To look for a specific gene in tissue (in situ) you need to use either In Situ Hybridization or In Situ Polymerase Chain Reaction (PCR). The traditional method is to digest the tissue, isolate DNA, separate the DNA into recognizable segments, then either blot and probe for specific genes or use the purified isolated DNA as a template for solution PCR followed by blotting and probing. In situ PCR yields results in the context of surrounding tissue histology whereas the solution methods do not.

 

If antibodies to the normal and mutated gene products have been produced, IHC can be done on sections to reveal these proteins. If there are no antibodies, reverse transcriptase polymerase chain reaction (RT-PCR) can be done on mRNA isolated from the fresh tissue through a variation of the above solution methods mentioned. We have had some success with in situ RT-PCR for some protein products. You'll have to consult the literature to see if anyone has done this for k-ras oncoproteins.

 

In any event, sounds like your pathologist needs to do a little more homework before you can adequately answer the request.

Hope this helped,

 

-----Original Message-----
From: Melissa Jensen [mailto:melzy@indytel.com]
Sent: Monday, November 04, 2002 6:40 PM
To: histonet@pathology.swmed.edu
Subject: k-ras