Fraisinib: a calixpyrrole derivative reducing A549 cell-derived NSCLC tumor in vivo acts as a ligand of the glycine-tRNA synthase, a new molecular target in oncology
Abstract
Background and purpose: Lung cancer is the leading cause of death in both men and women, constituting a major public health problem worldwide. Non-small-cell lung cancer accounts for 85%-90% of all lung cancers. We propose a compound that successfully fights tumor growth in vivo by targeting the enzyme GARS1. Experimental approach: We present an in-depth investigation of the mechanism through which Fraisinib [meso-(p-acetamidophenyl)-calix(4)pyrrole] affects the human lung adenocarcinoma A549 cell line. In a xenografted model of non-small-cell lung cancer, Fraisinib was found to reduce tumor mass volume without affecting the vital parameters or body weight of mice. Through a computational approach, we uncovered that glycyl-tRNA synthetase is its molecular target. Differential proteomics analysis further confirmed that pathways regulated by Fraisinib are consistent with glycyl-tRNA synthetase inhibition. Key results: Fraisinib displays a strong anti-tumoral potential coupled with limited toxicity in mice. Glycyl-tRNA synthetase has been identified and validated as a protein target of this compound. By inhibiting GARS1, Fraisinib modulates different key biological processes involved in tumoral growth, aggressiveness, and invasiveness. Conclusion and implications: The overall results indicate that Fraisinib is a powerful inhibitor of non-small-cell lung cancer growth by exerting its action on the enzyme GARS1 while displaying marginal toxicity in animal models. Together with the proven ability of this compound to cross the blood-brain barrier, we can assess that Fraisinib can kill two birds with one stone: targeting the primary tumor and its metastases "in one shot." Taken together, we suggest that inhibiting GARS1 expression and/or GARS1 enzymatic activity may be innovative molecular targets for cancer treatment.
Keywords: calix[4]pyrroles; cancer; drug discovery; non-small-cell lung cancer; proteomics; target discovery.
Two calix[4]pyrroles as potential therapeutics for castration-resistant prostate cancer
Abstract
Macrocyclic compounds meso-(p-acetamidophenyl)-calix[4]pyrrole and meso-(m-acetamidophenyl)-calix[4]pyrrole have previously been reported to exhibit cytotoxic properties towards lung cancer cells. Here, we report pre-clinical in vitro and in vivo studies showing that these calixpyrrole derivatives can inhibit cell growth in both PC3 and DU145 prostatic cancer cell lines. We explored the impact of these compounds on programmed cell death, as well as their ability to inhibit cellular invasion. In this study we have demonstrated the safety of these macrocyclic compounds by cytotoxicity tests on ex-vivo human peripheral blood mononuclear cells (PBMCs), and by in vivo subcutaneous administration. Preliminary in vivo tests demonstrated no hepato-, no nephro- and no genotoxicity in Balb/c mice compared to controls treated with cisplatin. These findings suggest these calixpyrroles might be novel therapeutic tools for the treatment of prostate cancer and of particular interest for the treatment of androgen-independent castration-resistant prostate cancer.
Keywords: Cancer; Chemoresistance; Drug development; New anticancer drugs; Prostate cancer; Tumour drug resistance; calix[4]pyrroles.
A novel calix[4]pyrrole derivative as a potential anticancer agent that forms genotoxic adducts with DNA
Abstract
meso-(p-acetamidophenyl)-calix[4]pyrrole 3 was found to exhibit remarkable cytotoxicity towards A549 cancer cells. A comparative study including the isomer of 3 meso-(m-acetamidophenyl)-calix[4]pyrrole 5, as well as molecules containing ‘fragments’ of these structures, demonstrated that both the calix[4]pyrrole and the acetamidophenyl units are essential for high cytotoxicity. Although calix[4]pyrroles and other anion-complexing ionophores have recently been reported to induce apoptosis by perturbing cellular chloride concentrations, in our study an alternative mechanism has emerged, as proven by the isolation of covalent DNA adducts revealed by the 32P postlabelling technique. Preliminary pharmacokinetic studies indicate that 3 is able to cross the Blood-Brain-Barrier, therefore being a potential drug that could kill primary and brain metastatic cancer cells simultaneously.
Introduction
Calix[n]pyrroles are macrocyclic compounds made up of pyrrole units linked at their 2,5-positions by quaternary carbon atoms1. meso-Octamethyl-calix[4]pyrrole 1 (Fig. 1) has been known for over a century2, but interest in this compound (and its congeners) rapidly developed only following the discovery of its ability to form complexes with anions3 and neutral molecules4 that can accept hydrogen bonds from the pyrrole NH units. Since these seminal papers, a vast number of calixpyrrole derivatives have been synthesised and investigated as selective ligands for different anions1,5, for sensing applications6, in the assembly of novel materials7,8 and devices9,10. When developing our early work on heterocyclophanes11 and calixarenes12 that can bind biologically relevant species, we reported the ability of meso-p-aminophenylcalix[4]pyrrole 2 to form a cytotoxic trans-Pt(II) complex in which the calix unit appears to assist the delivery of the toxic metal to DNA via the preliminary binding of the phosphate residues13. In this work, we propose a mechanism by which ‘free’ non-Pt(II) coordinated calixpyrrole 2 is released within the cell when the metal leaves the aminophenyl coordination site of 2 to form new bonds with nitrogen atoms of the nucleobases. Since tests conducted with ‘free’ 2 did not reveal any significant cytotoxicity when this was used at concentrations analogous to that of its Pt(II) complex, it was evident that 2 acted merely as a vector capable of delivering the toxic metal to DNA. To the best of our knowledge, this is the first report on the use of a calixpyrrole derivative for potential biomedical applications as a drug-delivery system.