Breast cancer gene expression analysis--the case for dynamic profiling.

Abstract

Cancer is a complicated disease with each individual tumor exhibiting to a variable degree a set of overlapping phenotypes that include abnormal proliferation and cell survival, genetic instability, tissue invasion, metastasis and angiogenesis. Each of these pathophysiological functions requires abnormal signaling that fails to respect the normal restraints imposed on healthy cells through homeostatic regulation. Understanding of deregulated gene expression is therefore an essential goal for cancer research because unraveling this problem will provide insights into the fundamental nature of cancer as well as provide opportunities for therapeutic intervention. Gene expression profiling is a remarkable technique that addresses this complexity by documenting the expression of thousands of genes at the level of mRNA abundance. From the standpoint of clinical investigation, the initial focus of gene profiling experiments has been on screening primary tumors for markers of poor prognosis. However this is only a first step in demonstrating the utility of this technique. Future advances will focus on understanding the evolution of an organ confined primary cancer to a treatment resistant lethal systemic disease through repeated tumor sampling and analysis, an approach termed in this paper "dynamic profiling". Using breast cancer endocrine therapy as an example our initial approaches to dynamic profiling will be described.