Direct comparison of microarray gene expression profiles between non-amplification and a modified cDNA amplification procedure applicable for needle biopsy tissues.

Global gene expression profiling by cDNA microarray analysis has been used to discover the biomarkers for early diagnosis of various cancers, subclassing cancer type, and prediction of patient's treatment outcome. The information provided by gene expression profiling may contribute to the design of molecular mechanism-based strategies for cancer prevention and/or treatment. However, the standard procedure for cDNA microarray analysis requires 5mug of good quality total RNA as starting material for each target preparation reaction. Thus, there is a limit for needle biopsy samples, laser capture microdissected tissues, or flow-sorted cells to successfully utilize the microarray technology. In order to profile the gene expression of needle biopsy tissue, we have modified the standard protocol by carrying out cDNA amplification after cDNA synthesis. We compared percentage present calls, absent calls, reproducibility, and concordance in needle biopsy samples processed by standard microarray protocol (cDNA non-amplification method) and our modified protocol (cDNA amplification method). The results showed that cDNA amplification method provided high reproducibility, representation, and concordance with the standard cDNA non-amplification method. We have successfully analyzed the gene expression profiles of needle biopsy tissues using the modified method without significantly changing the expression profiles. These results suggest that the global gene expression profiles of small biopsy samples can be achieved by our modified method to facilitate the analysis of gene expression profiles for clinical application.