VARIATION IN CELLULAR EGF RECEPTOR MESSENGER-RNA EXPRESSION DEMONSTRATED BY IN-SITU REVERSE-TRANSCRIPTASE POLYMERASE CHAIN-REACTION

Cell to cell variation of epidermal growth factor (EGF) receptor mRNA levels in heterogeneous tissues has been demonstrated with an in situ assay that couples reverse transcriptase with the polymerase chain rea ction (in situ RT - PCR). EGF receptor mRNA is consistently more highl y expressed in regions where cell division occurs; EGF receptor mRNA i s markedly reduced if not absent in areas of squamous cell differentia tion. Both human and mouse tumors overexpress EGF receptor mRNA when c ompared to normal tissue. In situ RT-PCR performed on thin sections ob tained from cell pellets of cultured cells with known levels of EGF re ceptor mRNA expression demonstrated that the mRNA detected is consiste nt with that observed by Northern analysis and quantitative PCR on iso lated RNA and by protein levels detected by antibody binding assays. I n situ RT - PCR is significantly more sensitive than in situ hybridiza tion (ISH). The method avoids background associated with hybridization reactions as in ISH or ISH following in situ PCR. In situ RT - PCR ap pears to be applicable to any gene as long as the oligonucleotide prim ers used have been proven to be specific and effective in a standard R T - PCR assay.