Altered PTEN, ATRX, CHGA, CHGB, and TP53 Expression Are Associated with Aggressive VHL-associated Pancreatic Neuroendocrine Tumors

Von Hippel-Lindau (VHL) syndrome is an inherited cancer syndrome in which 8-17 % of germline mutation carriers develop pancreatic neuroendocrine tumors (PNETs). There is limited data on prognostic markers for PNETs other than Ki-67, which is included in the World Health Organization classification system. Recently, specific genes and pathways have been identified by whole exome sequencing which may be involved in the tumorigenesis of PNETs and may be markers of disease aggressiveness. The objective of this study was to identify molecular markers of aggressive disease in VHL-associated PNETs. The protein expression of eight genes (PTEN, CHGA, CHGB, ATRX, DAXX, CC-3, VEGF, and TP53) was analyzed in PNETs by immunohistochemistry and compared to clinical data, VHL genotype, functional imaging results, and pathologic findings. Subcellular distribution of phosphatase and tensin (PTEN), chromogranin A (CHGA), and alpha thalassemia/mental retardation syndrome X-linked (ATRX) were significantly different by WHO classifications (p ≤ 0.05). There was decreased PTEN nuclear to cytoplasmic ratio (p < 0.01) and decreased CHGA nuclear expression (p = 0.03) in malignant samples as compared to benign. Lower cytoplasmic chromogranin B (CHGB) expression (p = 0.03) was associated with malignant tumors and metastasis. Higher nuclear expression of PTEN was associated with VHL mutations in exon 3 (p = 0.04). Higher PTEN and CHGB expression was associated with higher FDG-PET avidity (p < 0.05). Cytoplasmic expression of CC-3 was associated with higher serum chromogranin A levels (ρ = 0.72, p = 0.02). Lastly, greater cytoplasmic expression of p53 was associated with metastasis. Our findings suggest that altered PTEN, ATRX, CHGA, and CHGB expression are associated with aggressive PNET phenotype in VHL and may serve as useful adjunct prognostic markers to Ki-67 in PNETs.