The objective is to develop methods and procedures to make in situ assays (immunocytochemistry and in situ hybridization), assays which are innately more accurate than biochemical assays for this purpose, sensitive and reliable enough to routinely measure receptors, oncogenes and other clinically relevant low-abundance regulatory markers in clinical pathology. A new method (Freeze-Transfer) for in situ assay of receptor/c-onc mRNA and protein in breast cancer has been validated. Assay for Her-2 mRNA and receptor were 1-2 orders of magnitude more sensitive when performed on frozen thin sections of tissue thaw-mounted on thin microporous nitrocellulose films than on glass slides. Enhanced sensitivity was due to the quantitative retention of target molecules normally lost from thin sections mounted on glass during extensive washing and other assay procedures. The control of target loss by Freeze-Transfer resulted in more consistent data from assays in which the diagnostic resolving power of light microscopy was fully utilized. The enhanced cytochemical signal associated with Freeze-Transfer also suggests a long-term tissue storage mechanism superior to paraffin and frozen block. In Phase II, it is proposed to develop the knowledge base to make the Freeze-Transfer method, a routine procedure that can be carried out in a commercial setting. The engineering and scientific basis will be developed for a) the fabrication of the optimum membrane for use in the method; and b) the larger claim that the method provides a reference procedure to cytometrically assay clinically relevant low-abundance markers.
