57531

HACE1

-;HECT domain and ankyrin repeat containing E3 ubiquitin protein ligase 1;HACE1;HECT domain and ankyrin repeat containing E3 ubiquitin protein ligase 1

E3 ubiquitin-protein ligase HACE1

6q16.3

protein-coding

Transformation and cancer growth are regulated by the coordinate actions of oncogenes and tumor suppressors. Here, we show that the novel E3 ubiquitin ligase HACE1 is frequently downregulated in human tumors and maps to a region of chromosome 6q21 implicated in multiple human cancers. genetic inactivation of HACE1 in mice results in the development of spontaneous, late-onset cancer. A second hit from either environmental triggers or genetic heterozygosity of another tumor suppressor, p53, markedly increased tumor incidence in a Hace1-deficient background. Re-expression of HACE1 in human tumor cells directly abrogates in vitro and in vivo tumor growth, whereas downregulation of HACE1 via siRNA allows non-tumorigenic human cells to form tumors in vivo. Mechanistically, the tumor-suppressor function of HACE1 is dependent on its E3 ligase activity and HACE1 controls adhesion-dependent growth and cell cycle progression during cell stress through degradation of cyclin D1. Thus, HACE1 is a candidate chromosome 6q21 tumor-suppressor gene involved in multiple cancers.

Biopsies and cell lines of natural killer/T-cell lymphoma, nasal type (NKTCL) were subject to combined gene expression profiling and array-based comparative genomic hybridization analyses. Compared with peripheral T-cell lymphoma, not otherwise specified, NKTCL had greater transcript levels for NK-cell and cytotoxic molecules, especially granzyme H. Compared with normal NKcells, tumors were closer to activated than resting cells and overexpressed several genes related to vascular biology, Epstein-Barr Virus-induced genes, and PDGFRA. Notably, platelet-derived growth factor receptor alpha and its phosphorylated form were confirmed at the protein level, and in vitro the MEC04 NKTCL cell line was sensitive to imatinib. Deregulation of the AKT, Janus kinase-signal transducers and activators of transcription, and nuclear factor-kappaB pathways was corroborated by nuclear expression of phosphorylated AKT, signal transducers and activators of transcription 3, and RelA in NKTCL, and several deregulated genes in these pathways mapped to regions of recurrent copy number aberrations (AKT3 [1q44], IL6R [1q21.3], CCL2 [17q12], TNFRSF21 [6p12.3]). Several features of NKTCL uncovered by this analysis suggest perturbation of angiogenic pathways. Integrative analysis also evidenced deregulation of the tumor suppressor HACE1 in the frequently deleted 6q21 region. This study highlights emerging oncogenic pathways in NKTCL and identifies novel diagnostic and therapeutic targets.