Novel approach to gene expression profiling in Sézary syndrome

Microarray hybridization studies in Sézary syndrome (SS) have compared T lymphocytes from patients with cutaneous T-cell lymphoma with those of normal controls; a major limitation of this design is that significant inherent genetic variability of lymphocyte populations between individuals may produce differences in gene expression unrelated to disease state.

The objective of this study was to minimize the heterogeneity of information derived from whole-genome expression analysis and to identify specific genetic differences between highly purified malignant and nonmalignant (control) T cells from the same patient with SS.

Peripheral blood mononuclear cells were obtained from a patient with SS, stained with anti-T-cell receptor Vb (TCR-Vb) antibodies, and sorted by multiparameter flow cytometry. Malignant cells expressed the dominant TCR-Vb; control T cells lacked the dominant TCR-Vb but were otherwise phenotypically identical (CD3+CD4+CD45RO+). These cell populations were compared using the Illumina Inc. Sentrix Human-6 expression BeadChip system.

Transcriptome analysis using the J5 test, which was selected for data analysis based on an efficiency analysis of competing statistical methods, showed differential expression of 44 genes between the malignant and nonmalignant cell subsets. Promyelocytic leukaemia zinc finger protein (ZBTB16) was the most profoundly upregulated gene in the malignant cell population, while interferon regulatory factor 3 (IRF3) and interferon-induced protein 35 (IFI35), which are important elements of the cellular response to viral infection, were significantly downregulated.

The results of this study suggest the feasibility of this novel comparative approach to genomic profiling in SS. Using this method, we identified several differentially expressed genes and pathways not previously described in SS. While these findings require validation in larger studies, they may be important in SS pathogenesis.