Re: FWD'ing a post for Ronnie Houston RE c-kit

From:Bryan Hewlett

Ronnie, Carrie and Lisa,

Anecdotal statements such as this should be completely disregarded.

Have these findings been published in a peer-reviewed Journal? If not, why

The original tissue samples used in the references listed below, were
stained with the Santa Cruz antibody.

Subsequently, additional sections of these samples were re-stained with the
Dako antibody. The immunoreactivity patterns were essentially identical.

We have since stained hundreds of samples with both of these antibodies. In
our hands, the reactivity patterns have remained concordant.

We have never seen staining of fibroblasts or myofibroblasts in any of our
stromal tumours. We have seen occasional cells staining positively in a
small number of cases of dermatofibrosarcoma. None of these cells showed the
intense membrane staining that is typical of true c-kit immunoreactivity.
Weak cytoplasmic staining has been reported in a variety of tumours. We
believe this is mainly due to the use of a non-optimized procedure.

Both antibodies are Immunoglobulin fractions of rabbit serum. They must be
carefully titered to obtain the optimum working dilution. In addition, the
Santa Cruz antibody requires absorption against human plasma proteins in
order to obtain a clean reaction(see reference #1). The Dako antibody is
inherently cleaner since it has been solid phase absorbed by the supplier.

If anyone is obtaining "widespread positivity of fibroblasts and
myofibroblasts, suggesting non-specific cross reactivity with this
particular(Dako) antibody", they must be doing something horribly wrong!!!

Many authors have published articles on c-kit(CD117) staining and to the
best of my knowledge no such non-specific immunoreactivity has been




Sircar, K., Hewlett, B.R., Huizinga, J., Chorneyko, K., Berezin, I., and
Riddell, R.H.  Interstitial cells of Cajal as precursors of gastrointestinal
stromal tumours.

 Am. J. Surg. Pathol. 1999; 23(4): 377-389.

Robinson, T.L., Sircar, K., Hewlett, B.R., Chorneyko, K., Riddell, R.H.,
Huizinger, J.D.

Gastrointestinal Stromal Tumors May Originate from a Subset of CD34-Positive
Interstitial Cells of Cajal. Am.J.Pathol 2000; 156(4): 1157-1163.

Huizinger, J.D.,  Berezin, I., Sircar, K., Hewlett, B.R., Donnelly, G.,
Bercik, P., Ross, C., Algoufi, T., Fitzgerald, P., Der, T., Riddell, R.H.,
Collins, S.M. and Jacobson, K.

Development of Interstitial Cells of Cajal in a Full-Term Infant Without an
Enteric Nervous System.

Gastroenterology. 2001;120:561-567

----- Original Message -----
From: "Carrie Kyle-Byrne" 
To: "''" 
Sent: Thursday, March 13, 2003 4:18 PM
Subject: FWD'ing a post for Ronnie Houston RE c-kit

> One of our pathologists has shared some information he was given by a
> at AFIP. I have never seen this before, but was wondering if anyone else
> has.
> They claim that the c-Kit antibody from Dako(A4502)gives "widespread
> positivty of fibroblasts and myofibroblasts, suggesting non-specific cross
> reactivity with this particular antibody". However, they did not
> this phenomenon with the c-kit from Santa Cruz Biotechnology (sc-168).
> are not aware of any issues with their antibody.
> Both of these are polyclonals.
> Appreciate your input
> Thanks
> Ronnie
> Ronnie Houston
> Regional Histology Operations Manager
> Bon Secours HealthPartners Laboratories
> 5801 Bremo Road
> Richmond, VA 23226
> (804) 287 7972

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