Gene Expression Profiling Reveals Activation of Multiple Oncogenic Pathways and Over-Expression of Survivin in the Pathogenesis of Extranodal Nasal-Type NK/T Cell Lymphoma.

Abstract 3931

Poster Board III-867

Extranodal nasal-type Natural Killer/T-cell lymphoma (NKTCL) is a distinct clinicopathologic entity most commonly affecting Asians and Central and South Americans, and characterized by a clonal proliferation of NK or T cells with a cytotoxic phenotype. There is a strong association with Epstein-Barr Virus. The tumor is aggressive with patient usually surviving short duration even with chemotherapy. We performed the first comprehensive genome-wide gene expression profiling (GEP) of extranodal nasal-type Natural Killer/T-cell lymphoma (NKTCL) using formalin-fixed paraffin embedded (FFPE) tissue (n=25) and NK cell lines (n=5) and compared the results to the GEP of normal NK cells using the Illumina DASL whole genome array, with the objective of understanding the oncogenic pathways involved in the pathogenesis of NKTCL and to identify potential therapeutic targets. Quantitative-PCR validation of the GEP findings revealed over-expression of candidate genes BIRC5 (survivin), EZH2 and STMN1 in NK cell lines compared to normal NK cells, consistent with the GEP data. We then extracted a list of genes that are differentially expressed between NKTCL and normal NK cells and tissue controls. We than subjected this list of genes to pathway and network analysis using Metacore. This revealed a significant enrichment for cell cycle related genes and pathways. Furthermore, the network analysis results demonstrated a pro-proliferative and anti-apoptotic phenotype in NKTCL characterized by activation of Myc and nuclear factor kappa B (NF-KB), and deregulation of p53. This was further corroborated using immunohistochemistry on tissue microarray of NKTCL (n=33, including all cases with GEP performed). We observed a significant percentage of NKTCL showing overexpression for c-Myc (45.4%), p53 (87.9%) and NF-KB p50 (67.7%) on immunohistochemistry. Notably, overexpression of survivin was observed in 97% of the cases. Based on our findings, we propose a model of NKTCL pathogenesis where deregulation of p53 together with activation of MYC and NF-KB, possibly driven by EBV LMP-1, result in the cumulative upregulation of survivin. When KHYG and NKYS cell lines were treated with a compound IDR E804 which inhibited survivin, there is significant inhibition of cell growth as assess by MTS assay and induction of apoptosis as measured using Annexin V staining by flow cytometry. This suggests that compounds inhibiting survivin may be a potentially useful novel therapeutic approach in NKTCL.