Alternative Lengthening of Telomeres in Primary Pancreatic Neuroendocrine Tumors Is Associated with Aggressive Clinical Behavior and Poor Survival

Abstract

Purpose Alternative lengthening of telomeres (ALT), a telomerase-independent telomere maintenance mechanism, is strongly associated with ATRX and DAXX alterations and occurs frequently in pancreatic neuroendocrine tumors (PanNETs). Experimental design In a Korean cohort of 269 surgically resected primary PanNETs and 19 sporadic microadenomas, ALT status and nuclear ATRX and DAXX protein expression were assessed and compared with clinicopathologic factors. Results In PanNETs, ALT or loss of ATRX/DAXX nuclear expression was observed in 20.8% and 19.3%, respectively, while microadenomas were not altered. ALT-positive PanNETs displayed a significantly higher grade, size, and pT classification (all, p<0.001). ALT also strongly correlated with lymphovascular (p<0.001) and perineural invasion (p=0.001), and the presence of lymph node (p<0.001) and distant metastases (p=0.002). Furthermore, patients with ALT-positive primary PanNETs had a shorter recurrence-free survival (HR=3.38, 95% CI=1.83–6.27; p<0.001). Interestingly, when limiting to patients with distant metastases, those with ALT-positive primary tumors had significantly better overall survival (HR=0.23, 95% CI=0.08–0.68; p=0.008). Similarly, tumors with loss of ATRX/DAXX expression were significantly associated with ALT (p<0.001), aggressive clinical behavior, and reduced recurrence-free survival (p<0.001). However, similar to ALT, when limiting to patients with distant metastases, loss of ATRX/DAXX expression was associated with better overall survival (p=0.003). Conclusions Both primary ALT-positive and ATRX/DAXX-negative PanNETs are independently associated with aggressive clinicopathologic behavior and displayed reduced recurrence-free survival. In contrast, ALT activation and loss of ATRX/DAXX are both associated with better overall survival in patients with metastases. Therefore, these biomarkers may be used as prognostic markers depending on the context of the disease.

Alternative lengthening of telomeres and ATRX/DAXX loss can be reliably detected in FNAs of pancreatic neuroendocrine tumors

“…Therefore, cases were visually assessed and classified as ALT‐positive if ultrabright nuclear foci of telomere FISH signals were present in the cancer cells. The total intensities of individual ALT‐associated, ultrabright nuclear foci have been previously measured as >10‐fold higher than the mean integrated signal intensities for individual nonneoplastic cells in the same cases …”

“…Recent studies have demonstrated that, compared with ALT‐negative and ATRX/DAXX‐intact tumors, ALT‐positive and ATRX/DAXX‐negative primary PanNETs tend to be larger in size, have a higher World Health Organization grade, and are more likely to develop lymph node and distant metastases . ALT is a critical mechanism of carcinogenesis in PanNETs; and, as such, our ability to evaluate the status of these biomarkers will aid in the design of future clinical trials.…”

“…9,10 Recent studies have demonstrated that, compared with ALT-negative and ATRX/DAXX-intact tumors, ALT-positive and ATRX/DAXX-negative primary Pan-NETs tend to be larger in size, have a higher World Health Organization grade, and are more likely to develop lymph node and distant metastases. [11][12][13] ALT is a critical mechanism of carcinogenesis in PanNETs; and, as such, our ability to evaluate the status of these biomarkers will aid in the design of future clinical trials. For example, emerging data in other tumor types have demonstrated that ALT positivity and/or ATRX loss confers in vitro sensitivity to radiation as well as inhibition of topoisomerase and the DNAdamage mediator ATR (a serine/threonine protein kinase).…”

Gastroenteropancreatic Neuroendocrine Tumors

“…Available evidence suggests that mutations of MEN1 play a key role in tumor initiation, whereas late alterations of DAXX/ATRX seem to be implicated in tumor progression . Loss of DAXX/ATRX expression has been associated with activation of the alternative lengthening of telomeres (ALT) pathway and chromosomal instability, and poor outcomes have been reported for patients with ALT‐positive tumors . Three distinct molecular subtypes of pNETs recently have been identified: 1) the islet/insulinoma tumor subtype is characterized by low grade and limited metastatic potential; 2) the metastasis‐like primary subtype is characterized by high proliferative activity and aggressive behavior; and 3) the MEN1‐like/intermediate subtype shows moderate metastatic potential …”

Assessment of ARX expression, a novel biomarker for metastatic risk in pancreatic neuroendocrine tumors, in endoscopic ultrasound fine‐needle aspiration

“…Several markers have the potential to identify high and low risk subgroups. PanNET tumorigenesis is commonly driven by mutations in the tumor suppressor genes MEN1 , ATRX , or DAXX , of which the latter two are associated with the alternative lengthening of telomeres phenotype (ALT) and correlate with worse prognosis and liver metastases . Protein loss, detected by immunohistochemistry (IHC), can be used as a surrogate for somatic inactivating mutations in ATRX and DAXX .…”