Evaluation of selected circulating cytokines from the IL-6 family - interleukin 6, oncostatin M, and cardiotrophin-1 - in gastro-entero-pancreatic and bronchial neuroendocrine tumours.

Introduction: The incidence of neuroendocrine tumours (NETs) increased over the last years. Most of them are non-functioning, and the course of the disease is asymptomatic for a long time. This results in late diagnosis at an advanced stage. The aim of our study was the evaluation of selected circulating cytokines of interleukin-6 family - interleukin 6 (IL-6), oncostatin M (OSM), and cardiotrophin-1 (CT1) - in NETs.

Material and methods: The study group comprised 80 patients (56%) in several subgroups, including gastroenteropancreatic (GEPNETs, n = 64, 80%) and bronchopulmonary neuroendocrine tumours (BPNETs, n = 16; 20%). Serum IL-6, OSM, and CT1 concentrations were tested using ELISA.

Results: The median concentration of IL-6 was 41.5 pg/ml in the study group and 32.6 pg/ml in the control group, and the difference was statistically significant (p < 0.001). The concentration of OSM was significantly lower in the study group than in the control group (p < 0.001), at 105.6 pg/ml and 115.5 pg/ml, respectively. There was a significant difference (p < 0.01) in concentration of CT1 in the study group (222.0 pg/ml) and controls (267.2 pg/ml). Our investigation into selected IL-6 family cytokines revealed differential modulation of signal transduction pathways.

Conclusions: These findings suggest that despite utilising a common signalling transducer, individual IL-6 family cytokines exert distinct biological effects on neuroendocrine tumour development. Notably, IL-6 appears to promote tumourigenesis, while OSM and CT1 exhibit inhibitory effects on gastro-entero-pancreatic and bronchial neuroendocrine tumour development. Further studies are necessary to validate the diagnostic utility of IL-6 family cytokines in NETs.