Discovery and characterization of Isofistularin-3, a marine brominated alkaloid, as a new DNA demethylating agent inducing cell cycle arrest and sensitization to TRAIL in cancer cells

Abstract

We characterized the brominated alkaloid Isofistularin-3 (Iso-3), from the marine sponge Aplysina aerophoba, as a new DNA methyltransferase (DNMT)1 inhibitor. Docking analysis confirmed our in vitro DNMT inhibition data and revealed binding of Iso-3 within the DNA binding site of DNMT1. Subsequent increased expression of tumor suppressor gene aryl hydrocarbon receptor (AHR) could be correlated to decreased methylation of CpG sites within the essential Sp1 regulatory region of its promoter. Iso-3 induced growth arrest of cancer cells in G0/G1 concomitant with increased p21 and p27 expression and reduced cyclin E1, PCNA and c-myc levels. Reduced proliferation was accompanied by morphological changes typical of autophagy revealed by fluorescent and transmission electron microscopy and validated by LC3I-II conversion. Furthermore, Iso-3 strongly synergized with tumor-necrosis-factor related apoptosis inducing ligand (TRAIL) in RAJI [combination index (CI) = 0.22] and U-937 cells (CI = 0.21) and increased TRAIL-induced apoptosis via a mechanism involving reduction of survivin expression but not of Bcl-2 family proteins nor X-linked inhibitor of apoptosis protein (XIAP). Iso-3 treatment decreased FLIPL expression and triggered activation of endoplasmatic reticulum (ER) stress with increased GRP78 expression, eventually inducing TRAIL receptor death receptor (DR)5 surface expression. Importantly, as a potential candidate for further anticancer drug development, Iso-3 reduced the viability, colony and in vivo tumor forming potential without affecting the viability of PBMCs from healthy donors or zebrafish development.

Marine natural products

“…489 Isostularin-3 (Aplysina aerophoba) 490 was found to induce apoptosis, with a novel mode of action via inhibition of DNA methyltransferase 1, making it a new anticancer lead. 491 Internet-based tools for scientic research continue to grow in scope and availability. Submission of 71 MNP structures to the Eli Lilly Open Innovation Drug Discovery 492 platform identied several potential leads as inhibitors of VEGF, including araguspongine C 493 and puupehenone, 494 hence both these could be attractive targets for further investigation as angiogenesis inhibitors.…”

Novel Anticancer Fused Pyrazole Derivatives as EGFR and VEGFR-2 Dual TK Inhibitors

“…Pyrazole and fused pyrazole systems, such as pyranopyrazole and pyrazolpyrimidines, are promising scaffolds for many anticancer agents (Chauhan and Kumar, 2013;Ansari et al, 2017;Shukla et al, 2019). Moreover, many brominated marine natural products, such as eudistomin alkaloid, exhibited anticancer activity (Rajesh and Annappan, 2015;Florean et al, 2016). In addition to many synthetic brominated compounds (Ökten et al, 2017).…”

Anti-Tumorigenic and Anti-Metastatic Activity of the Sponge-Derived Marine Drugs Aeroplysinin-1 and Isofistularin-3 against Pheochromocytoma In Vitro

“…Cytotoxic activity of Isofistularin-3 against HeLa cells has been reported (IC 50 = 8.5 ± 0.2 µM) [ 14 ]. Recently, Florean et al [ 15 ] described Isofistularin-3 as a new DNA methyltransferase (DNMT) 1 inhibitor. The agent reduces viability, colony formation as well as in vivo tumor growth in two lymphoma cell lines without affecting the viability of peripheral blood mononuclear cells or zebrafish development.…”