Сationic carboxamide derivatives of tricyclic heteroaromatic compounds: synthesis and preliminary evaluation of antiproliferative activity

This research was aimed at the synthesis and study of biological activity of the carboxamides of tricyclic heteroaromatic systems, acridone, phenazine and thioxanthone, containing the aliphatic and aromatic cationic substituents at amide fragment. These heterocyclic cores are DNA intercalating agents, whereas the introduction of cationic groups provides additional ionic interactions of the ligands with their biological targets, such as DNA and enzymatic complexes of the system of nucleic acids biosynthesis. A convenient way of the introduction of such groups is a modification of heterocyclic carboxamides. A small library of new cationic amide derivatives of acridone-4-, phenazine-1- and thioxanthone-4-carboxylic acids was obtained. They were synthesized in 37-81% yield by mild and selective quaternization of the nitrogen atoms at N,N-dimethylaminoalkyl (alkyl = ethyl, propyl) and pyridylmethyl fragments of the neutral N-functionalized carboxamides with methyl iodide. Tricyclic heteroaromatic cores were not affected. Convenient protocol for the synthesis of thioxanthone-4-carboxylic acid (TCA) based on the reaction of 2-mercaptobenzoic and 2-iodobenzoic acids followed by cyclization of the intermediate was developed (yield 79%). A series of new N-functionalized neutral amides of TCA, the precursors of corresponding cationic carboxamide, were also obtained via the reaction of acyl chloride with amines. Preliminary in vitro testing of four compounds as potential antitumor agents in U87MG tumor cell culture (human malignant glioma) demonstrated their significant antiproliferative activity at low micromolar concentrations, with growth inhibition values GI50 in the range 1.7-11 µM. These results suggest that cationic carboxamides of tricyclic heteroaromatic systems are promising scaffolds for the design of new antitumor drugs.

Metabolic Switching of Tumor Cells under Hypoxic Conditions in a Tumor-on-a-chip Model

Hypoxia switches the metabolism of tumor cells and induces drug resistance. Currently, no therapeutic exists that effectively and specifically targets hypoxic cells in tumors. Development of such therapeutics critically depends on the availability of in vitro models that accurately recapitulate hypoxia as found in the tumor microenvironment. Here, we report on the design and validation of an easy-to-fabricate tumor-on-a-chip microfluidic platform that robustly emulates the hypoxic tumor microenvironment. The tumor-on-a-chip model consists of a central chamber for 3D tumor cell culture and two side channels for medium perfusion. The microfluidic device is fabricated from polydimethylsiloxane (PDMS), and oxygen diffusion in the device is blocked by an embedded sheet of polymethyl methacrylate (PMMA). Hypoxia was confirmed using oxygen-sensitive probes and the effect on the 3D tumor cell culture investigated by a pH-sensitive dual-labeled fluorescent dextran and a fluorescently labeled glucose analogue. In contrast to control devices without PMMA, PMMA-containing devices gave rise to decreases in oxygen and pH levels as well as an increased consumption of glucose after two days of culture, indicating a rapid metabolic switch of the tumor cells under hypoxic conditions towards increased glycolysis. This platform will open new avenues for testing anti-cancer therapies targeting hypoxic areas.

Optimization of Triterpene Saponins Mixture with Antiproliferative Activity

In this study, three of the saponins present in leaves of Hedera helix L., α-hederin, hederagenin, and hederacoside C were studied for their antiproliferative activity. The three saponins were analyzed in different concentrations by in vitro tests on normal fibroblasts cells and cervix ephitelial tumor cells. Determination of cytotoxicity and antitumor effects was performed using the MTT method. From the tested saponins, α-hederin was biocompatible in normal fibroblasts cells at concentrations between 2–10 μg/mL. Its antiproliferative activity was exerted in the concentration range of 10–400 μg/mL in cervix ephitelial tumor cells. Similarly, hederagenin presented antiproliferative activity at concentrations between 25–400 μg/mL. In turn, hederacoside C was shown to be noncytotoxic in normal fibroblasts and cervix ephitelial tumor cell culture at all the tested concentrations. The obtained experimental results were analyzed by “Mixture design”, a specialized form of the response surface method (RSM) provided by the Design Expert 11 software, and the optimal composition of obtained saponins mixture was selected and verified in vitro for antiproliferative activity. The results showed that an optimal saponins mixture has the potential to be used in pharmacological applications.