DNA methylation at an enhancer of the three prime repair exonuclease 2 gene (TREX2) is linked to gene expression and survival in laryngeal cancer.

BACKGROUND: Genetic aberrations in DNA repair genes are linked to cancer, but less is reported about epigenetic regulation of DNA repair and functional consequences. We investigated the intragenic methylation loss at the three prime repair exonuclease 2 (TREX2) locus in laryngeal (n = 256) and colorectal cancer cases (n = 95) and in pan-cancer data from The Cancer Genome Atlas (TCGA). RESULTS: Significant methylation loss at an intragenic site of TREX2 was a frequent trait in both patient cohorts (p = 0.016 and < 0.001, respectively) and in 15 out of 22 TCGA studies. Methylation loss correlated with immunohistochemically staining for TREX2 (p < 0.0001) in laryngeal tumors and improved overall survival of laryngeal cancer patients (p = 0.045). Chromatin immunoprecipitation, demethylation experiments, and reporter gene assays revealed that the region of methylation loss can function as a CCAAT/enhancer binding protein alpha (CEBPA)-responsive enhancer element regulating TREX2 expression. CONCLUSIONS: The data highlight a regulatory role of TREX2 DNA methylation for gene expression which might affect incidence and survival of laryngeal cancer. Altered TREX2 protein levels in tumors may affect drug-induced DNA damage repair and provide new tailored therapies.

Factors predicting survival after diagnosis of laryngeal cancer.

Survival in patients with laryngeal cancer has not increased remarkably within the last years. It is presumed that a variety of factors act jointly in predicting survival after diagnosis: tumour stage, tumour site, treatment approaches, age and comorbidities. The aim of this German clinical multi-centre study is to present results from multivariate analysis. A retrospective cohort study was conducted in four hospitals in South-West Germany. Incident cases with laryngeal squamous cell carcinoma were included for the years 1998 to 2004, resulting in a population sample of 594 patients. Multivariate regression analysis was performed using the Cox proportional hazards model. Patients were followed up for 64.1months on average. Overall 5-year survival was 66% (95% confidence interval (CI): 62-70%). The strongest risk factors in multivariate analysis were age at first diagnosis (hazard ratio (HR): 1.5; 95% CI: 1.5-1.7 per each additional 10years), tumour stage, and the development of recurrences (HR 3.1; 95% CI: 2.3-4.2) or second primary carcinomas (HR 2.1; 95% CI: 1.4-3.1). A somewhat weaker effect was shown for patients with comorbidities (using Charlson's comorbidity index). The choice of treatment did not strongly affect survival when adjusting for other factors, possibly because the optimal treatment approach was applied for the specific constitution and requirements of each patient. For future research it would be desirable to study the effect of treatment on quality of life in multivariate analysis as well as other modifiable risk factors as smoking and drinking reduction or cessation after diagnosis.

Dynamic survivin in head and neck cancer: molecular mechanism and therapeutic potential.

Although disease management of head and neck squamous cell carcinomas (HNSCC) has improved significantly, therapy resistance leading to tumor recurrence still counteracts improvement of long-term survival. Consequently, identification of molecular markers that signal increased risk of treatment failure or, which can be exploited by targeted therapy, is urgently needed. Survivin is strongly expressed in HNSCC, and its proposed dual role as an apoptosis inhibitor and a mitotic effector positioned survivin in the front line of cancer research. Notably, survivin is detected as a cytoplasmic and as a nuclear protein in HNSCC patients, which stimulated numerous studies to investigate and to speculate on the functional and prognostic significance of its dynamic localization. This review focuses on our current understanding of the molecular mechanisms regulating survivin's intracellular localization and discusses its potential prognostic and therapeutic relevance for head and neck cancer.

The survivin isoform survivin-3B is cytoprotective and can function as a chromosomal passenger complex protein.

Survivin is described as a bifunctional protein inhibiting apoptosis and regulating mitosis. However, the biological functions and contributions to cancer progression of survivin splice variants are controversially discussed. We here show that the intracellular localization of these splice variants depends on a Crm1-dependent nuclear export signal (NES) present in survivin, surviving(-2B) and survivin(-3B), but absent in survivin(-deltaEx3) and survivin(-2alpha). Survivin isoforms lack an active nuclear import signal and are able to enter the nucleus by passive diffusion. Only survivin(-3B) but none of the other splice variants is cytoprotective and able to efficiently interact with chromosomal passenger complex (CPC) proteins. The NES together with efficient CPC formation is required for the cytoprotective activity of survivin isoforms, as well as for their correct localization and function during cell division. In the tumours from breast, colorectal, head and neck cancer, lymphoma and leukemia patients, survivin and survivin(-2B) were found overexpressed. However, survivin was the predominant form detected, and the other survivin isoforms were only expressed at low levels in tumours. Our data provide a molecular rationale for the localization and activity of survivin variants, and conclude that survivin isoforms are unlikely to modulate survivin in trans in cancer patients.