The blood option: transcriptional profiling in clinical trials

Transcriptional profiling of peripheral blood shows considerable promise, with the number of clinical studies increasing rapidly over the past 2-3 years. Peripheral blood is in contact with almost every tissue of the body, is the most readily accessible source of RNA in the clinical setting, and allows for repeated measurements. Studies have already been performed across multiple clinical disciplines and before and after therapeutic intervention. However, blood transcriptional profiling is not yet ready to be applied in clinical practice. A number of methodological issues and hurdles need to be overcome, with issues of standardizing blood sample collection and processing of paramount importance. The specificity of gene expression signatures for individual disease states also needs to be established. Large-scale, well-planned and integrated approaches across multiple medical disciplines could accelerate the pace of research, by resolving these methodological issues and by determining the clinical applications of blood transcriptional profiling, particularly in relation to clinical trials.