Copy number variant (CNV) analysis was performed on renal cell carcinoma (RCC) specimens (chromophobe, clear cell, oncocytoma, papillary type 1, papillary type 2) using high resolution arrays (1.85 million probes). RCC samples exhibited diverse genomic changes within and across tumor types ranging from 106 CNV segments in a clear cell specimen to 2238 CNV segments in a papillary type 2 specimen. Despite the genomic heterogeneity, distinct CNV segments were common within each of 4 tumor classifications: chromophobe (7 segments), clear cell (3 segments), oncocytoma (9 segments), and papillary type 2 (2 segments). Shared segments ranged from a 6.1 Kb deletion among oncocytomas to a 208.3 Kb deletion common to chromophobes. Among common tumor type-specific variations, chromophobe, clear cell and oncocytomas comprised exclusively non-coding DNA. No CNV regions were common to papillary type 1 specimens although there were 12 amplifications and 12 deletions in 5 of 6 samples. Three microRNAs and 12 mRNA genes had ≥ 98% of their coding region contained within CNV regions including multiple gene families (chromophobe: amylase 1A, 1B, 1C; oncocytoma: general transcription factor 2H2, 2B, 2C, 2D). Gene deletions involved in histone modification and chromatin remodeling affected individual subtypes (clear cell: SFMBT, SETD2; papillary type 2: BAZ1A) as well as the collective RCC group (KDM4C). The genomic amplifications/deletions identified in each renal tumor type represent potential diagnostic and/or prognostic biomarkers.
Overall design
Tissue samples were obtained from the University of Pittsburgh Health Sciences Tissue Bank (HSTB) using an honest broker system and according to IRB approved protocol #970480. Samples were acquired as surgical specimens, flash-frozen in a 1.8 ml cryotube (NalgeNunc, Inc., Rochester, NY) followed by immediate storage at -80C. Each tumor sample (n=27) was classified into one of 5 renal cancer subtypes (chromophobe: n=5, clear cell: n=5, oncocytoma: n=5, papillary type 1: n=6, papillary type 2: n=6) by consensus evaluation of correlative hematoxylin and eosin stained slides performed independently by 3 anatomical pathologists. The three pathologists also confirmed the absence of pathological features in adjacent normal renal samples (n=9) and this normal reference group was expanded by inclusion of 14 normal thyroid samples and 8 normal lung specimens. DNA from each of these specimens was analyzed using genotyping microarrays (SNP 6.0, Affymetrix, Sunnyvale, CA).
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