Pharmacological Inhibition of Class IIA HDACs by LMK-235 in Pancreatic Neuroendocrine Tumor Cells

Abstract

Histone deacetylases (HDACs) play a key role in epigenetic mechanisms in health and disease and their dysfunction is implied in several cancer entities. Analysis of expression patterns in pancreatic neuroendocrine tumors (pNETs) indicated HDAC5 to be a potential target for future therapies. As a first step towards a possible treatment, the aim of this study was to evaluate the in vitro cellular and molecular effects of HDAC5 inhibition in pNET cells. Two pNET cell lines, BON-1 and QGP-1, were incubated with different concentrations of the selective class IIA HDAC inhibitor, LMK-235. Effects on cell viability were determined using the resazurin-assay, the caspase-assay, and Annexin-V staining. Western Blot and immunofluorescence microscopy were performed to assess the effects on HDAC5 functionality. LMK-235 lowered overall cell viability by inducing apoptosis in a dose- and time-dependent manner. Furthermore, acetylation of histone-H3 increased with higher LMK-235 concentrations, indicating functional inhibition of HDAC4/5. Immunocytochemical analysis showed that proliferative activity (phosphohistone H3 and Ki-67) decreased at highest concentrations of LMK-235 while chromogranin and somatostatin receptor 2 (SSTR2) expression increased in a dose-dependent manner. HDAC5 expression was found to be largely unaffected by LMK-235. These findings indicate LMK-235 to be a potential therapeutic approach for the development of an effective and selective pNET treatment.

Strategies Towards Improving Clinical Outcomes of Peptide Receptor Radionuclide Therapy

“…Limited data indicated an 1.06-to 9.2-fold increased uptake in liver metastases after intra-arterial administration of somatostatin analogues labelled with Indium-111, Gallium-68 or Lutetium-177 compared to intravenous administration [50]. In a recent pilotstudy, however, no increased tumour uptake after intraarterial 68 Ga-DOTATOC injection was observed [51]. The LUTIA trial is poised to investigate the absorbed tumour dose and response of intra-arterial 177 Lu-DOTATATE in progressive, liver-dominant, and unresectable NEN patients [52].…”

“…In the first small clinical study, in which metastatic NEN patients were given a single low dose of 177 Lu-DOTA-EB-TATE (n = 5) or 177 Lu-DOTATATE (n = 3), a 7.9-fold increase in tumour dose was observed in the patients receiving 177 Lu-DOTA-EB-TATE [74]. Hereafter, singe doses of 1.11 GBq, 1.85 GBq, and 3.7 GBq 177 Lu-DOTA-EB-TATE were compared with 3.7 GBq 177 Lu-DOTATATE in 33 metastatic NEN patients with high uptake on 68 Ga-DOTATATE PET/CT. Regarding the decrease in post-treatment maximum standardized uptake value (SUV) and response rates, the higher doses of 177 Lu-DOTA-EB-TATE were more effective than 177 Lu-DOTATATE [75].…”

“…One of the eligibility criteria for PRRT is sufficient tumour uptake on SSTR imaging, i.e. 68 Ga-DOTATATE/-TOC PET/ CT or 111 In-DTPA-octreotide scintigraphy, because the uptake reflects the presence of SSTRs. The uptake of the tumour related to the uptake of the liver, kidneys, and spleen on 111 In-DTPA-octreotide scintigraphy (also known as the Krenning scale) was found to correlate with OR following treatment with PRRT [98].…”

Improving TRAIL-induced apoptosis in cancers by interfering with histone modifications

“…HDAC4,5 Chemoresistant cancer cells [75] multiple myeloma [76] pancreatic neuroendocrine tumours [77] Tubastatin A HDAC6 cholangiocarcinoma [78] melanoma [79] Ricolinostat (ACY-1215) multiple myeloma [68][69][70]…”

Update on current pancreatic treatments: from molecular pathways to treatment

“…Chromogranin and somatostatin receptor 2 (SSTR2) expression increase on the other hand in a dose-dependent manner. Therefore lmk-235 is a potential therapeutic approach pancreatic neuroendocrine neoplasms 62, 63. Metarrestin is an effective therapeutic inhibitor and a candidate with a favorable pharmacokinetic profile achieving excellent intra-tumor tissue levels in pancreatic cancer.…”