Endocrine Abstracts

Background: Pancreatic neuroendocrine tumours (PNETs), including insulinomas, are rare but clinically important neoplasms for which surgery remains the only curative treatment. Development of effective non-surgical therapies is hindered by the lack of representative pre-clinical models, particularly of complex biological pathways including epigenetic gene regulation. Dogs spontaneously develop insulinomas that closely mimic human insulinomas, providing a unique opportunity for comparative studies.

Aim: Compare the epigenetic landscape and response to epigenetic-targeting drugs, of canine insulinoma cell line canINS with existing models to assess its translational relevance to human insulinomas.

Methods: We performed single-cell RNA-sequencing (scRNA-seq) of canINS and MIN6 (mouse) and examined the expression of known human PNET driver genes in canINS, BON1 (human) and MIN6 using quantitative real-time PCR (qPCR) and western blotting. The efficacy of various epigenetic-targeting drugs was tested using CellTiter-Blue assays.

Results: scRNA-seq analysis demonstrated high ATRX and YY1, intermediate DAXX and low MEN1 expression in canINS and MIN6. qPCR confirmed canINS expressed high ATRX and YY1, however showed low DAXX and intermediate MEN1 expression. Compared with BON1 and MIN6, canINS showed the highest relative YY1 (>5-fold) and ATRX (>12-fold) expression. DAXX expression was similar across all cell lines. MEN1 expression was highest in MIN6 (>21-fold) and intermediate in canINS, confirmed by western blotting. Five-day treatments with 1µM DNA methyltransferase (DNMT), histone deacetylase (HDAC) and histone methyltransferase (KDM) inhibitors all significantly (P<0.05) reduced canINS and MIN6 viability. In BON1 only HDAC and bromodomain and extra-terminal inhibitors significantly reduced viability.

Conclusion: High expression of MEN1 and ATRX observed in canINS indicated it may represent an improved epigenetic insulinoma model compared to BON1 and MIN6, as DAXX/ATRX and MEN1 mutations are not typically observed in insulinoma patients. Multispecies drug screening revealed conserved sensitivity to epigenetic-targeting drugs in insulinoma cell lines, particularly HDAC inhibitors, supporting their potential therapeutic utility.