Gene expression analysis of single neoplastic cells and the pathogenesis of Hodgkin's lymphoma.

The origin of the Reed-Sternberg cell of Hodgkin's disease remained clouded in mystery for almost a century after its discovery in 1898. The major obstacle to its understanding is that, unlike other cancers, the malignant cell of Hodgkin's disease is vastly outnumbered by surrounding non-neoplastic cells at approximately 1000:1. We have devised several strategies to isolate Reed-Sternberg T-cells to determine their origin, global gene expression and, ultimately, their pathogenesis. This has increased the number of genes known to be expressed in Reed-Sternberg cells by >100-fold to over 12,000. Approaches such as density gradients, microdissection, and cell sorting help to enrich Reed-Sternberg cells for genomic DNA analysis. However, single-cell micromanipulation of living Reed-Sternberg cells was required to determine the genome-wide gene expression profile of these cells. Combined analysis of single cells and cell lines revealed the expression of 2666 named genes. Further analysis with high-density gene expression microarrays has demonstrated the expression of approximately 12,000 genes by Reed-Sternberg cells. The gene expression profile is that of an aberrant germinal center B-lymphocyte that resists apoptosis through CD40 signaling and NFkappaB activation. Gene expression analysis of Hodgkin's disease is an extreme test case demonstrating the application of high-throughput gene expression studies even to individual cells from clinical samples.