Evaluating the potential of Vacuolar ATPase inhibitors as anticancer agents and multigram synthesis of the potent salicylihalamide analog saliphenylhalamide

Abstract

The natural product salicylihalamide is a potent inhibitor of the Vacuolar ATPase (V-ATPase), a potential target for antitumor chemotherapy. We generated salicylihalamide-resistant tumor cell lines typified by an overexpansion of lysosomal organelles. We also found that many tumor cell lines upregulate tissue-specific plasmalemmal V-ATPases, and hypothesize that tumors that derive their energy from glycolysis rely on these isoforms to maintain a neutral cytosolic pH. To further validate the potential of V-ATPase inhibitors as leads for cancer chemotherapy, we developed a multigram synthesis of the potent salicylihalamide analog saliphenylhalamide.As products of evolution, natural products are selected for interaction with living systems. As such, an unbiased quest to study their function will inevitably lead to discoveries in biology, potentially with therapeutic implications. 1 By accessing congeners for mode-of-action studies, optimization of potency and pharmacokinetic, toxicological, and metabolic properties, synthesis takes center stage as an enabling tool to execute a natural product-based discovery and development program. 2 Herein, we report our efforts to validate inhibition of the Vacuolar ATPase (V-ATPase), the target of salicylihalamide, as a strategy for cancer chemotherapeutic intervention. This program led to the selection and multigram synthesis of a salicylihalamide analog saliphenylhalamide (2, SaliPhe).The marine metabolite salicylihalamide A (1), 3 the first member of a family of marine and terrestrial metabolites characterized by a signature N-acyl-enamine appended macrocyclic salicylate, has elicited a great deal of interest from the synthetic community 4 -certainly due in part because of their growth-inhibitory activities against cultured human tumor cells and oncogene-transformed cell lines through mechanisms distinct from standard clinical antitumor agents. 5 The cellular target of SaliA remained elusive until after our first total synthesis, 3b when Boyd and coworkers reported that SaliA and other related benzolactone enamides inhibit V-ATPase activity in membrane preparations of mammalian cells, but not V-ATPases from Publisher's Disclaimer: This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. NIH Public Access NIH-PA Author ManuscriptNIH-PA Author Manuscript NIH-PA Author Manuscript yeast and other fungi -an observation that distinguishes them from previously identified VATPase inhibitors. 6 Our biochemical studies utilizing a reconstituted, fully purified bovine brain V-ATPase confirmed this activity and demonstrated that SaliA binds irreversibly to the trans-mem...

Mode of Cell Death Induction by Pharmacological Vacuolar H+-ATPase (V-ATPase) Inhibition

“…There are reports showing that the long known V-ATPase inhibitors bafilomycin and concanamycin induce growth arrest and cell death in a variety of tumor cells (30), and more recently VATPase inhibitors like salicylihalamide (31) or NIK-12192 (32) have also been reported to possess antitumor activity. However, detailed information on the signaling pathways and molecular nodules used by these compounds is rather limited but crucial to understand the impact of pharmacological V-ATPase inhibition in cancer treatment.…”

V-ATPase Inhibition Regulates Anoikis Resistance and Metastasis of Cancer Cells

“…Several well-known V-ATPase inhibitors like concanamycin and bafilomycin were shown to lead to growth arrest and cell death induction in a variety of tumor cells (6,31,32). Also, the newly developed V-ATPase inhibitors salicylihalamide (33) and NIK-12192 (34) have demonstrated antitumor activity although the exact molecular mechanisms of V-ATPase inhibitors leading to inhibition of tumor cell invasion remain to be elucidated. Cell surface located VATPase is hypothesized to create a proton efflux leading to an acidic pericellular microenvironment that promotes the activity of proinvasive proteases (35).…”

Akt Inhibitor MK2206 Prevents Influenza pH1N1 Virus Infection In Vitro

“…CT-G0068) was from ChemieTek. Saliphenylhalamide (SaliPhe) was synthetized by Jef De Brabander (15). All compounds were dissolved in 100% dimethyl sulfoxide (DMSO) (Sigma-Aldrich) to 10 mM stock solutions and stored at Ϫ80°C until use.…”