606P - Novel miRNA-based assay for GEP-NENs management

Background

Somatostatin receptors (SSTRs) fulfill a primary role in Gastro-Entero-Pancreatic-Neuroendocrine-Neoplasia (GEP-NENs) diagnosis, prognosis and ⁶⁸ Ga-based imaging techniques. Peptide Receptor Radionuclide Therapy (PRRT) targets SSTRs. Despite most of GEP-NENs show SSTRs overexpression, about 30% of patients do not respond to PRRT. ¹⁸FDG –PET represents a prognostic marker, especially in Pancreatic NEN (PanNENs). MiRNAs are involved in several of mechanisms, including cell metabolism and modulation of gene expression. MiRNAs-based assays may represent novel diagnostic, prognostic and predictive tool able to address decision making in NENs management.

Methods

NGS analysis was performed on small-RNAs fraction from plasma of 24 ¹⁸PET/FDG (+) and (-) GEP-NET patients. MiRNAs significantly associated with ¹⁸PET/FDG were validated by RT/qPCR on overall case series (n.66) and correlated with clinical outcome and parameters, including ⁶⁸Ga-PET SUV_max. Novel semi-automated combined IHC and miRNAs-ISH protocol was developed. Simoultaneus SSTR-2 and nuclear miRNA expression was assesed in n.36 GEP-NET FFPE samples. A novel software-based analysis provided a preliminary correlation between SSTR-2 and miRNA in PanNEN subset. MiRNA mimics were transfected into Pan NET cell lines to evaluate miRNA interference on SSTR2 expression.

Results

Mir-A,B,C signature (patent pending) predicts ¹⁸FDG/PET outcome with AUC: 0,8; 0,8 and 0,95, respectively in PanNETs (n.25). Mir-A,B,C result to be significantly increased in small intestine (SINETs) and in PanNETs patients when compared to healthy controls. Mir-B negatively correlates with ⁶⁸Ga-PET SUVmax (p< 0,03). Preliminary analysis of IHC-miRNA-ISH, revealed 67% of miR-B(+) nuclei in SSTR2(-) areas, in contrast with 45% in SSTR2(+) areas. Mir-b promoted SSTR2 modulation of 50% in NT-3 cell lines.

Conclusions

The 3 miRNAs signature correlates with GEP-NET disease and with¹⁸FDG/PET status and PFS, in PanNEN subset. The signature may represent an easy, quick and non-invasive tool to provide diagnostic and prognostic information. Mir-B inversly correlates with PFS,⁶⁸Ga-PET SUV_max and in vitro preclinical model together with IHC-miRNA-ISH evaluation suggest mirB interference with SSTR2 expression, affecting PRRT efficacy.

Clinical trial identification

Editorial acknowledgement

Legal entity responsible for the study

IRST, Meldola.

Funding

Has not received any funding.

Disclosure

All authors have declared no conflicts of interest.