Aneurysmal bone cyst (ABC) is a locally aggressive osseous lesion that typically occurs during the first two decades of life. ABC was regarded historically as a nonneoplastic process, but recent cytogenetic data have shown clonal rearrangements of chromosomal bands 16q22 and 17p13, indicating a neoplastic basis in at least some ABCs. Herein we show that a recurring ABC chromosomal translocation t(16;17)(q22;p13) creates a fusion gene in which the osteoblast cadherin 11 gene (CDH11) promoter region on 16q22 is juxtaposed to the entire ubiquitin-specific protease USP6 (Tre2) coding sequence on 17p13. CDH11-USP6 fusion transcripts were demonstrated only in ABC with t(16;17) but other ABCs had CDH11 or USP6 rearrangements resulting from alternate cytogenetic mechanisms. CDH11 is expressed strongly in bone, and our findings implicate a novel oncogenic mechanism in which deregulated USP6 transcription results from juxtaposition to the highly active CDH11 promoter.

14-3-3 proteins are ubiquitously expressed regulators of various cellular functions, including proliferation, metabolism, and differentiation, and altered 14-3-3 expression is associated with development and progression of cancer. We report a transforming 14-3-3 oncoprotein, which we identified through conventional cytogenetics and whole-transcriptome sequencing analysis as a highly recurrent genetic mechanism in a clinically aggressive form of uterine sarcoma: high-grade endometrial stromal sarcoma (ESS). The 14-3-3 oncoprotein results from a t (10;17) genomic rearrangement, leading to fusion between 14-3-3ε (YWHAE) and either of two nearly identical FAM22 family members (FAM22A or FAM22B). Expression of YWHAE–FAM22 fusion oncoproteins was demonstrated by immunoblot in t (10;17)-bearing frozen tumor and cell line samples. YWHAE–FAM22 fusion gene knockdowns were performed with shRNAs and siRNAs targeting various FAM22A exons in an t (10;17)-bearing ESS cell line (ESS1): Fusion protein expression was inhibited, with corresponding reduction in cell growth and migration. YWHAE–FAM22 maintains a structurally and functionally intact 14-3-3ε (YWHAE) protein-binding domain, which is directed to the nucleus by a FAM22 nuclear localization sequence. In contrast to classic ESS, harboring JAZF1 genetic fusions, YWHAE–FAM22 ESS display high-grade histologic features, a distinct gene-expression profile, and a more aggressive clinical course. Fluorescence in situ hybridization analysis demonstrated absolute specificity of YWHAE–FAM22A/B genetic rearrangement for high-grade ESS, with no fusions detected in other uterine and nonuterine mesenchymal tumors (55 tumor types, n = 827). These discoveries reveal diagnostically and therapeutically relevant models for characterizing aberrant 14-3-3 oncogenic functions.

Aneurysmal bone cysts (ABC) are locally aggressive bone tumors that often feature chromosome 17p13 rearrangements. One of the ABC 17p13 rearrangements – t(16;17)(q22;p13) – was recently shown to create a CDH11-USP6 fusion in which the USP6/TRE17 oncogene is overexpressed through juxtaposition with the CDH11 promoter. Herein, we characterize four different ABC translocations involving 17p13, and we show that each is associated with a novel USP6 fusion oncogene. Specifically, we demonstrate that t(1;17), t(3;17), t(9;17), and t(17;17) result in USP6 fusions with TRAP150 (thyroid receptor-associated protein 150), ZNF9 (ZiNc Finger 9), Osteomodulin, and COL1A1 (Collagen 1A1), respectively. The oncogenic mechanism in these fusion genes is akin to CDH11-USP6, with the USP6 coding sequences juxtaposed to the promoter regions in each of the four novel translocation partners. The novel fusion partners appear well suited to drive USP6 transcription in the bone/mesenchymal context: osteomodulin is expressed strongly in osteoblastic lineages, and the COL1A1 promoter has an oncogenic role in the mesenchymal cancer dermatofibrosarcoma protuberans. In summary, these studies show that USP6 oncogenic activation results from heterogeneous genomic mechanisms involving USP6 transcriptional upregulation by juxtaposition with ectopic promoters.