Gene Expression Profiling Using Nanostring™ Reveals Differences According to Location, Histology and MIPI Score in Mantle Cell Lymphoma

Background Mantle cell lymphoma (MCL) is an aggressive B cell neoplasm characterized the by t(11;14)(q13;q32)/CCND1-IGH resulting in overexpression of cyclin D1. Although indolent variants are recognized, MCL is generally aggressive and incurable. The MCL International Prognostic Index (MIPI), gene expression-based proliferation signatures, Ki-67 proliferation index, p53 expression, and aggressive histologic features are used for risk stratification, but the prognostic groups defined by each of these markers are clinically heterogeneous, demonstrating that each parameter alone does not fully account for the clinical behavior of these tumors. In this study, we investigated the gene expression profile of 60 cases of MCL and evaluated which genes had expression patterns that correlate with different clinical and histopathological parameters. Design A total of 60 excisional biopsy specimens of MCL were selected for gene expression profiling. Forty (66%) and 16 (26%) cases were untreated and relapse/persistent samples, respectively; in 4 this unknown was unknown. Biopsy sites included lymph nodes (n=38), spleen (n=10), tonsil (n=6) and various other extranodal tissue sites (n=6). The morphologic features were classic in 27 and aggressive (blastoid/pleomorphic) in 33 patients. MIPI was calculated in selected patients with nodal involvement and whose biopsy was an obtained prior to treatment. Each block contained tumor cells representing ≥ 80% of all cells in the biopsy specimen. RNA was extracted from formalin-fixed paraffin-embedded tissue using the Qiagen Allprep FFPE Kit after deparaffinization, according to the manufacturer's instructions. Gene expression was quantified in 200ng of RNA on the Nanostring™ platform. Normalization for RNA loading was performed using the geometric mean of 40 housekeeping genes with a cutoff value 20. Standard QC and data processing were performed using the nSolver™ Analysis Software. Adjusted p-values were used according to the Benjamini-Hochberg procedure. Results Gene expression profiling was different according to the site of involvement of MCL. Compared with nodal involvement, MCL involving spleen showed overexpression of VEGFA (p