RF19 | PSUN349 Histone Eraser and Reader Targeting Epigenetic Inhibitors Are Effective in Pancreatic Neuroendocrine Tumours
Authors: Carmichael James , Escoubet Laure , Lines Kate , Mavrommatis Konstantinos , Mortensen Deborah , Thakker Rajesh V , Thakurta Anjan 
Published: November 2022

Abstract

Background
The 5-year survival for metastatic pancreatic neuroendocrine tumours (PNETs) is &lt;50%, and current therapies are not effective. Thus, there is an unmet clinical need for new therapies for patients with PNETs. PNETs frequently have mutations in chromatin remodelling genes, including in Multiple Endocrine Neoplasia type 1 (MEN1), encoding menin, which is mutated in up to 40% of sporadic PNETs, and is part of multiple histone modifying complexes including the SET1/MLL methyltransferases.

Aim
To examine multiple classes of epigenetic inhibitors and determine which may be effective in treating PNETs.

Methods
BON1 and QGP1 PNET cell lines, the bronchial NET cell line H727, and the non-NET cell line HEK293T were utilised to assess &gt;150 small molecule inhibitors targeting: histone deacetylases (HDACs); histone acetyltransferases; histone demethylases (KDMs); histone methyltransferases; bromodomain-containing proteins; menin; and DNA methyltransferases (DNMTs). MTOR inhibitors, already used clinically for PNET patients, as well as drugs targeting other tumorigenic pathways e.g. the proto-oncogene SRC, were used as comparators. Efficacy of compounds was evaluated using the Cell Titer Blue cell viability assay, and the Caspase Glo 3/7 apoptosis assay.

Results
At a dose of 1mM for 7 days, 26 compounds (including HDAC, KDM, bromodomain and mTOR inhibitors) significantly decreased the viability of both the BON1 and QGP1 cell lines by &gt;50%, compared to DMSO control treated cells. Upon increasing the dose to 10mM for 7 days, 34 additional compounds, making a total of 60 compounds (including inhibitors of menin and DNMTs), decreased viability of both BON1 and QGP1 cells by &gt;50%; and 56 and 46 compounds also reduced viability of H727 and HEK293 cells by &gt;50%, respectively. Apoptosis assays utilising the 60 above compounds, at 10mM for 7 days, revealed that 25, 18, 14, and 9 of them could increase apoptosis by &gt;4-fold of BON1, QGP1, H727 and HEK293 cells, respectively. Ten compounds (2 KDM, 5 HDAC and 3 bromodomain inhibitors) that were effective in reducing viability by &gt;50% as well as increasing apoptosis by &gt;4-fold of NET cells, were selected for further dosing (0.1-10mM) and time course investigations (3-7 days). All 10 compounds significantly reduced viability of BON1 and QGP1 cells (p&lt;0.01) after 3 days of treatment. The KDM and HDAC inhibitors showed the greatest efficacy, by significantly (p&lt;0.05) reducing BON1 and QGP1 cell viability at as low as 25nM treatment for 3 days. The efficacy of bromodomain inhibitors was not attained until 1000nM treatment, however these inhibitors had very little effect on the non-NET HEK293 cells.

Conclusions
Compounds targeting HDACs, KDMs or bromodomain-containing proteins are effective in reducing viability by &gt;50% and increasing apoptosis by &gt;4-fold of NET cells, and thus provide novel agents for studying anti-cancer mechanisms and potential therapeutic options for PNETs.
Presentation: Sunday, June 12, 2022 12:30 p.m. - 2:30 p.m., Sunday, June 12, 2022 1:12 p.m. - 1:17 p.m.