Multicellular tumor spheroid model to evaluate spatio-temporal dynamics effect of chemotherapeutics: application to the gemcitabine/CHK1 inhibitor combination in pancreatic cancer

International audienceUNLABELLED: ABSTRACT: BACKGROUND: The multicellular tumor spheroid (MCTS) is an in vitro model associating malignant-cell microenvironment and 3D organization as currently observed in avascular tumors. METHODS: In order to evaluate the relevance of this model for pre-clinical studies of drug combinations, we analyzed the effect of gemcitabine alone and in combination with the CHIR-124 CHK1 inhibitor in a Capan-2 pancreatic cell MCTS model. RESULTS: Compared to monolayer cultures, Capan-2 MCTS exhibited resistance to gemcitabine cytotoxic effect. This resistance was amplified in EGF-deprived quiescent spheroid suggesting that quiescent cells are playing a role in gemcitabine multicellular resistance. After a prolonged incubation with gemcitabine, DNA damages and massive apoptosis were observed throughout the spheroid while cell cycle arrest was restricted to the outer cell layer, indicating that gemcitabine-induced apoptosis is directly correlated to DNA damages. The combination of gemcitabine and CHIR-124 in this MCTS model, enhanced the sensitivity to the gemcitabine antiproliferative effect in correlation with an increase in DNA damage and apoptosis. CONCLUSIONS: These results demonstrate that our pancreatic MCTS model, suitable for both screening and imaging analysis, is a valuable advanced tool for evaluating the spatio-temporal effect of drugs and drug combinations in a chemoresistant and microenvironment-depending tumor model

New insights on the mechanism of quinoline-based DNA methyltransferase inhibitors

Among the epigenetic marks, DNA methylation is one of the most studied. It is highly deregulated in numerous diseases, including cancer. Indeed, it has been shown that hypermethylation of tumor suppressor genes promoters is a common feature of cancer cells. Because DNA methylation is reversible, the DNA methyltransferases (DNMTs), responsible for this epigenetic mark, are considered promising therapeutic targets. Several molecules have been identified as DNMT inhibitors and, among the non-nucleoside inhibitors, 4-aminoquinoline-based inhibitors, such as SGI-1027 and its analogs, showed potent inhibitory activity. Here we characterized the in vitro mechanism of action of SGI-1027 and two analogs. Enzymatic competition studies with the DNA substrate and the methyl donor cofactor, S-adenosyl-L-methionine (AdoMet), displayed AdoMet non-competitive and DNA competitive behavior. In addition, deviations from the Michaelis-Menten model in DNA competition experiments suggested an interaction with DNA. Thus their ability to interact with DNA was established; although SGI-1027 was a weak DNA ligand, analog 5, the most potent inhibitor, strongly interacted with DNA. Finally, as 5 interacted with DNMT only when the DNA duplex was present, we hypothesize that this class of chemical compounds inhibit DNMTs by interacting with the DNA substrate

Identification of a novel quinoline-based DNA demethylating compound highly potent in cancer cells

Background DNA methyltransferases (DNMTs) are epigenetic enzymes involved in embryonic development, cell differentiation, epithelial to mesenchymal transition, and control of gene expression, whose overexpression or enhanced catalytic activity has been widely reported in cancer initiation and progression. To date, two DNMT inhibitors (DNMTi), 5-azacytidine (5-AZA) and 5-aza-2′-deoxycytidine (DAC), are approved for the treatment of myelodysplastic syndromes and acute myeloid leukemia. Nevertheless, they are chemically instable and quite toxic for healthy cells; thus, the discovery of novel DNMTi is urgent. Results Here, we report the identification of a new quinoline-based molecule, MC3353, as a non-nucleoside inhibitor and downregulator of DNMT. This compound was able, in promoter demethylating assays, to induce enhanced green fluorescence protein (EGFP) gene expression in HCT116 cells and transcription in a cytomegalovirus (CMV) promoter-driven luciferase reporter system in KG-1 cells. Moreover, MC3353 displayed a strong antiproliferative activity when tested on HCT116 colon cancer cells after 48 h of treatment at 0.5 μM. At higher doses, this compound provided a cytotoxic effect in double DNMT knockout HCT116 cells. MC3353 was also screened on a different panel of cancer cells (KG-1 and U-937 acute myeloid leukemia, RAJI Burkitts lymphoma, PC-3 prostate cancer, and MDA-MB-231 breast cancer), where it arrested cell proliferation and reduced viability after 48 h of treatment with IC50 values ranging from 0.3 to 0.9 μM. Compared to healthy cell models, MC3353 induced apoptosis (e.g., U-937 and KG-1 cells) or necrosis (e.g., RAJI cells) at lower concentrations. Importantly, together with the main DNMT3A enzyme inhibition, MC3353 was also able to downregulate the DNMT3A protein level in selected HCT116 and PC-3 cell lines. Additionally, this compound provided impairment of the epithelial-to-mesenchymal transition (EMT) by inducing E-cadherin while reducing matrix metalloproteinase (MMP2) mRNA and protein levels in PC-3 and HCT116 cells. Last, tested on a panel of primary osteosarcoma cell lines, MC3353 markedly inhibited cell growth with low single-digit micromolar IC50 ranging from 1.1 to 2.4 μM. Interestingly, in Saos-2 osteosarcoma cells, MC3353 induced both expression of genes and mineralized the matrix as evidence of osteosarcoma to osteoblast differentiation. Conclusions The present work describes MC3353 as a novel DNMTi displaying a stronger in cell demethylating ability than both 5-AZA and DAC, providing re-activation of the silenced ubiquitin C-terminal hydrolase L1 (UCHL1) gene. MC3353 displayed dose- and time-dependent antiproliferative activity in several cancer cell types, inducing cell death and affecting EMT through E-cadherin and MMP2 modulation. In addition, this compound proved efficacy even in primary osteosarcoma cell models, through the modulation of genes involved in osteoblast differentiation.This work was supported by COST Action CM1406 (PBA, LA, AM, SV); by Ricerca Finalizzata 2013 PE-2013-02355271 (AM); by PRIN 2016 (prot. 20152TE5PK) (AM, LA); by AIRC grants n. 19162 (AM), 17217 (LA), and 18843 (MT); by NIH funds n. R01GM114306 (AM) and BLUEPRINT n. 282510 (AM, LA); by Programma VALERE: Vanvitelli per la Ricerca (LA) and the Italian-Flag Project-EPIGEN (LA); and by Pasteur Institute-Cenci Bolognetti Foundation (MT). MS was supported by a Waxweiler grant for cancer prevention research from the Action Lions Vaincre le Cancer. CF is a recipient of a Télévie Luxembourg fellowship. The work at LBMCC was supported by the Recherche Cancer et Sang foundation, by the Recherches Scientifiques Luxembourg association, by the Een Häerz fir kriibskrank Kanner association, by the Action LIONS Vaincre le Cancer association, and by Télévie Luxembourg. MD was supported by the Research Institute of Pharmaceutical Sciences, College of Pharmacy, Seoul National University, Korea; the Tumor Microenvironment GCRC (2011-0030001) from the National Research Foundation funded by the Ministry of Science and ICT of Korea; the Creative-Pioneering Researchers Program through Seoul National University (SNU) [Funding number: 370C-20160062]; and Brain Korea (BK) 21 Plus program, Korea

Drug Discovery Methods

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Development of a CERT START Domain–Ceramide HTRF Binding Assay and Application to Pharmacological Studies and Screening

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Asymmetric Synthesis and Binding Study of New Long-Chain HPA-12 Analogues as Potent Ligands of the Ceramide Transfer Protein CERT

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Bioactive flavonoids of Tanacetum parthenium revisited

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The CERT antagonist HPA-12: First practical synthesis and individual binding evaluation of the four stereoisomers

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