Gastroenterology

Gastroenterology

Volume 146, Issue 2, February 2014, Pages 453-460.e5
Gastroenterology

Original Research
Full Report: Clinical—Pancreas
Loss of DAXX and ATRX Are Associated With Chromosome Instability and Reduced Survival of Patients With Pancreatic Neuroendocrine Tumors

https://doi.org/10.1053/j.gastro.2013.10.020Get rights and content

Background & Aims

Sporadic pancreatic neuroendocrine tumors (pNETs) are rare and genetically heterogeneous. Chromosome instability (CIN) has been detected in pNETs from patients with poor outcomes, but no specific genetic factors have been associated with CIN. Mutations in death domain–associated protein gene (DAXX) or ATR-X gene (ATRX) (which both encode proteins involved in chromatin remodeling) have been detected in 40% of pNETs, in association with activation of alternative lengthening of telomeres. We investigated whether loss of DAXX or ATRX, and consequent alternative lengthening of telomeres, are related to CIN in pNETs. We also assessed whether loss of DAXX or ATRX is associated with specific phenotypes of pNETs.

Methods

We collected well-differentiated primary pNET samples from 142 patients at the University Hospital Zurich and from 101 patients at the University Hospital Bern (both located in Switzerland). Clinical follow-up data were obtained for 149 patients from general practitioners and tumor registries. The tumors were reclassified into 3 groups according to the 2010 World Health Organization classification. Samples were analyzed by immunohistochemistry and telomeric fluorescence in situ hybridization. We correlated loss of DAXX, or ATRX, expression, and activation of alternative lengthening of telomeres with data from comparative genomic hybridization array studies, as well as with clinical and pathological features of the tumors and relapse and survival data.

Results

Loss of DAXX or ATRX protein and alternative lengthening of telomeres were associated with CIN in pNETs. Furthermore, loss of DAXX or ATRX correlated with tumor stage and metastasis, reduced time of relapse-free survival, and decreased time of tumor-associated survival.

Conclusions

Loss of DAXX or ATRX is associated with CIN in pNETs and shorter survival times of patients. These results support the hypothesis that DAXX- and ATRX-negative tumors are a more aggressive subtype of pNET, and could lead to identification of strategies to target CIN in pancreatic tumors.

Section snippets

Tissues, Patient Characteristics, and Follow-Up Data

pNETs of 142 patients (collective I, University of Zurich) were formalin-fixed and paraffin-embedded. A subset of collected tissues additionally was snap-frozen. Clinical follow-up data of 113 patients were obtained by contacting the patients' general practitioners and Cancer Registry Zurich. The tumors were reclassified into 3 groups according to the 2010 World Health Organization classification.13 In addition, 101 patients with follow-up data were selected from the Department of Pathology of

DAXX and ATRX Protein Loss in pNETs

We performed IHC for DAXX and ATRX on a TMA with 142 pNETs (patient characteristics are shown in Table 1). Only nuclear labeling for DAXX and ATRX were scored as positive and only samples with positive internal control were considered negative (Figure 1).7 Results were obtained for 92 pNETs (24 tumors had no positive internal control and no tumor tissue was evaluable in another 26 samples). We observed a loss of DAXX in 23 samples (25%) and a loss of ATRX in 20 samples (18%). Altogether, 39

Discussion

We provide evidence that pNETs with loss of either DAXX or ATRX expression show ALT activation and CIN. No specific genetic background has been associated previously with CIN in pNETs. The significant association of loss of DAXX or ATRX protein with ALT and CIN provides strong evidence for a causal relationship between these factors. Several arguments support this interpretation. ALT activation has been linked to CIN in several tumor types and in glioblastoma with DAXX or ATRX loss.20, 21, 22,

Acknowledgments

The authors thank Cornelia Schlup and Caroline Hammer for technical assistance, Iria Gonzalez Vasconcellos for the fluorescence in situ hybridization protocol and scientific support, Prof. P. Komminoth for helpful discussions, and Inti Zlobec for careful reading of the manuscript. The tissues were provided with support of the Tissue Bank Bern.

References (30)

  • J.R. Strosberg et al.

    First-line chemotherapy with capecitabine and temozolomide in patients with metastatic pancreatic endocrine carcinomas

    Cancer

    (2011)
  • Y.M. Jonkers et al.

    Chromosomal instability predicts metastatic disease in patients with insulinomas

    Endocr Relat Cancer

    (2005)
  • Y. Jiao et al.

    DAXX/ATRX, MEN1, and mTOR pathway genes are frequently altered in pancreatic neuroendocrine tumors

    Science

    (2011)
  • S. Yachida et al.

    Small cell and large cell neuroendocrine carcinomas of the pancreas are genetically similar and distinct from well-differentiated pancreatic neuroendocrine tumors

    Am J Surg Pathol

    (2012)
  • C.M. Heaphy et al.

    Altered telomeres in tumors with ATRX and DAXX mutations

    Science

    (2011)
  • Cited by (329)

    View all citing articles on Scopus

    Conflicts of interest The authors disclose no conflicts.

    Funding The study was supported by a Swiss National Foundation grant (310030_144236 to A.P.); and supported in part by the Dutch Digestion Foundation (E.-J.S.).

    View full text