Rapid competitive PCR determination of relative gene expression in limiting tissue samples

Reverse transcriptase (RT)-PCR is widely used to study gene transcription in many biological systems. Despite the development of a variety of procedures, quantification of RT-PCR products remains difficult, particularly when processing a large number of samples. Therefore, we developed a novel alternative PCR technique that we term "rapid competitive PCR" (RC-PCR), designed to study the relative expression of specific genes in a large number of small tissue biopsies. RC-PCR is characterized by measuring relative gene expression at the mRNA level of two or more samples with a nonradioactive assay based on competitive PCR amplification between identical sequences of internal standard and target cDNA. Only a single reaction tube per sample is used in this technique, and it was validated by comparing RC-PCR of protein kinase C zeta and alpha expression in rat colonic mucosa samples with competitive RT-PCR analysis (requiring 6-8 reaction tubes per sample). We conclude that RC-PCR is a simple, rapid, highly sensitive technique that is capable of detecting less than twofold differences in mRNA expression.