Systemic Cancer Hallmarks as Novel Markers Associated with Progression-free Survival in Gastroenteropancreatic Neuroendocrine Tumor Patients Undergoing PRRT

INTRODUCTION: Gastroenteropancreatic neuroendocrine tumors (GEP-NETs) are a heterogeneous group of tumors often detected at the metastatic stage. The aim of this study was to profile the peripheral blood transcriptome through RNA-Seq and investigate the association of the systemic cancer hallmarks with progression-free survival, in peptide receptor radionuclide therapy (PRRT)-treated GEP-NET patients. METHODS: The cohorts were discovery cohort [PRRT-naïve well-differentiated GEP-NETs, n = 59; age- and sex-matched healthy individuals, n = 38], and independent evaluation cohort [GEP-NETs, n = 66]. Peripheral blood transcriptomes were profiled through RNA sequencing and cancer hallmarks were identified via Gene Set Enrichment Analysis (GSEA). Activities of cancer hallmarks in each sample were calculated using Gene Set Variation Analysis. Differentially expressed genes were identified with DESeq2. Progression-free survival was used as a primary endpoint and prognostic association was evaluated using univariate and multivariate Cox proportional hazard (COXPH) analyses. RESULTS: RNA-Seq captured global changes in the peripheral blood transcriptome of GEP-NET patients. Peripheral blood transcriptome of NET patients showed differential enrichment of 30 systemic cancer hallmarks viz., TNF-α signaling via NF-κB, IL2/STAT5 signaling, TNF-α response, TNF-γ response, IL6/JAK/STAT signaling, TGF-β signaling, heme metabolism, etc. In the univariate analyses, two cancer hallmarks were prognostically significant (p < 0.05) in GEP-NETs. Heme metabolism and IL2/STAT5 signaling were statistically significant in the discovery cohort (n = 58) and independent evaluation cohort (n = 66). In multivariate COXPH analyses, heme metabolism and IL2/STAT5 signaling were independently associated with PFS in GEP-NET patients undergoing PRRT. CONCLUSIONS: This study provides comprehensive coverage of the peripheral blood transcriptome of GEP-NET patients via RNA-Seq and identifies systemic cancer hallmarks as independent prognostic factors in NETs.