Evading Pgp activity in drug-resistant cancer cells: a structural and functional study of antitubulin furan metotica compounds

Current scenario of indole derivatives with potential anti-drug-resistant cancer activity

Cancer chemotherapy is frequently hampered by drug resistance, so the resistance to anticancer agents represents one of the major obstacles for the effective cancer treatment. Indole derivatives have the potential to act on diverse targets in cancer cells and exhibit promising activity against drug-resistant cancers. Moreover, some indole-containing compounds such as Semaxanib, Sunitinib, Vinorelbine, and Vinblastine have already been applied in clinics for various kinds of cancer even drug-resistant cancer therapy. Thus, indole derivatives are one of significant resources for the development of novel anti-drug-resistant cancer agents. This review focuses on the recent development of indole derivatives with potential therapeutic application for drug-resistant cancers, and the mechanisms of action, the critical aspects of design as well as structure-activity relationships, covering articles published from 2010 to 2020.

Modified carbazoles destabilize microtubules and kill glioblastoma multiform cells

Small molecules that target microtubules (MTs) represent promising therapeutics to treat certain types of cancer, including glioblastoma multiform (GBM). We synthesized modified carbazoles and evaluated their antitumor activity in GBM cells in culture. Modified carbazoles with an ethyl moiety linked to the nitrogen of the carbazole and a carbonyl moiety linked to distinct biaromatic rings exhibited remarkably different killing activities in human GBM cell lines and patient-derived GBM cells, with IC₅₀ values from 67 to >10,000 nM. Measures of the activity of modified carbazoles with tubulin and microtubules coupled to molecular docking studies show that these compounds bind to the colchicine site of tubulin in a unique low interaction space that inhibits tubulin assembly. The modified carbazoles reported here represent novel chemical tools to better understand how small molecules disrupt MT functions and kill devastating cancers such as GBM.

SQ1274, a novel microtubule inhibitor, inhibits ovarian and uterine cancer cell growth

OBJECTIVE

Paclitaxel, a microtubule inhibitor, is subject to tumor resistance while treating high-grade serous ovarian and uterine cancer. This study aims to directly compare the effects of SQ1274, a novel microtubule inhibitor that binds to the colchicine-binding site on tubulin, and paclitaxel in high-grade serous ovarian and uterine cancer cell lines both in vitro and in vivo.

METHODS

We assessed the sensitivity of ovarian (OVCAR8) and uterine (ARK1) cancer cell lines to SQ1274 and paclitaxel using XTT assays. We used western blot and quantitative real-time PCR to analyze changes in AXL RNA and protein expression by SQ1274 and paclitaxel. Differences in cell-cycle arrest and apoptosis were investigated using flow cytometry. Finally, we treated ovarian and uterine xenograft models with vehicle, paclitaxel, or SQ1274.

RESULTS

First, we demonstrate that SQ1274 has a much lower IC₅₀ than paclitaxel in both ARK1 (1.26 nM vs. 15.34 nM, respectively) and OVCAR8 (1.34 nM vs. 10.29 nM, respectively) cancer cell lines. Second, we show SQ1274 decreases both RNA and protein expression of AXL. Third, we show that SQ1274 causes increased cell-cycle arrest and apoptosis compared to paclitaxel. Finally, we report that SQ1274 more effectively inhibits tumor growth in vivo compared to paclitaxel.

CONCLUSIONS

SQ1274 presents as a viable alternative to paclitaxel for treating ovarian and uterine cancer. This study supports the development of SQ1274 as a chemotherapeutic to treat ovarian and uterine cancer.

An Indole-Chalcone Inhibits Multidrug-Resistant Cancer Cell Growth by Targeting Microtubules

Multidrug resistance and toxic side effects are the major challenges in cancer treatment with microtubule-targeting agents (MTAs), and thus, there is an urgent clinical need for new therapies. Chalcone, a common simple scaffold found in many natural products, is widely used as a privileged structure in medicinal chemistry. We have previously validated tubulin as the anticancer target for chalcone derivatives. In this study, an α-methyl-substituted indole-chalcone (FC77) was synthesized and found to exhibit an excellent cytotoxicity against the NCI-60 cell lines (average concentration causing 50% growth inhibition = 6 nM). More importantly, several multidrug-resistant cancer cell lines showed no resistance to FC77, and the compound demonstrated good selective toxicity against cancer cells versus normal CD34⁺ blood progenitor cells. A further mechanistic study demonstrated that FC77 could arrest cells that relate to the binding to tubulin and inhibit the microtubule dynamics. The National Cancer Institute COMPARE analysis and molecular modeling indicated that FC77 had a mechanism of action similar to that of colchicine. Overall, our data demonstrate that this indole-chalcone represents a novel MTA template for further development of potential drug candidates for the treatment of multidrug-resistant cancers.

The novel compound STK405759 is a microtubule-targeting agent with potent and selective cytotoxicity against multiple myeloma in vitro and in vivo

Despite advances in treatment, multiple myeloma (MM) remains incurable. Here we propose the use of STK405759, a novel microtubule targeting agent (MTA) and member of the furan metotica family for MM therapy.

STK405759 inhibited tubulin polymerization in a cell-free system and in myeloma cells. This molecule had potent cytotoxic activity against several MM cell lines and patient-derived MM cells. Moreover, STK405759 demonstrated cytotoxicity against drug-resistant myeloma cells that overexpressed the P-glycoprotein drug-efflux pump. STK405759 was not cytotoxic to peripheral blood mononuclear cells, including activated B and T lymphocytes. This compound caused mitotic arrest and apoptosis of myeloma cells characterized by cleavage of poly (ADP-ribose) polymerase-1 and caspase-8, as well as decreased protein expression of mcl-1. The combination of STK405759 with bortezomib, lenalidomide or dexamethasone had synergistic cytotoxic activity. In in vivo studies, STK405759-treated mice had significantly decreased MM tumor burden and prolonged survival compared to vehicle treated- mice.

These results provide a rationale for further evaluation of STK405759 as monotherapy or part of combination therapy for treating patients with MM.

Pharmacological, Physiochemical, and Drug-Relevant Biological Properties of Short Chain Fatty Acid Hexosamine Analogues Used in Metabolic Glycoengineering

In this study, we catalog structure activity relationships (SAR) of several short chain fatty acid (SCFA)-modified hexosamine analogues used in metabolic glycoengineering (MGE) by comparing in silico and experimental measurements of physiochemical properties important in drug design. We then describe the impact of these compounds on selected biological parameters that influence the pharmacological properties and safety of drug candidates by monitoring P-glycoprotein (Pgp) efflux, inhibition of cytochrome P450 3A4 (CYP3A4), hERG channel inhibition, and cardiomyocyte cytotoxicity. These parameters are influenced by length of the SCFAs (e.g., acetate vs n-butyrate), which are added to MGE analogues to increase the efficiency of cellular uptake, the regioisomeric arrangement of the SCFAs on the core sugar, the structure of the core sugar itself, and by the type of N-acyl modification (e.g., N-acetyl vs N-azido). By cataloging the influence of these SAR on pharmacological properties of MGE analogues, this study outlines design considerations for tuning the pharmacological, physiochemical, and the toxicological parameters of this emerging class of small molecule drug candidates.

The Mechanism of the Interactions of Pironetin Analog/Combretastatin A-4 Hybrids with Tubulin

We here report an investigation of the interactions with tubulin of two types of molecules of a hybrid structural type consisting in a combretastatin A-4 moiety and a simplified pironetin fragment. The cytotoxicities of the molecules on two reference tumoral cell lines were measured. In addition, the effects of the compounds on the cell cycle and on microtubule assembly were observed. The dynamics of microtubule polymerization was investigated by means of immunofluorescence assays. It was thus established that at least some of the compounds under study exert their cytotoxic action by means of interaction with tubulin.

A highly tumor-targeted nanoparticle of podophyllotoxin penetrated tumor core and regressed multidrug resistant tumors

Podophyllotoxin (PPT) exhibited significant activity against P-glycoprotein mediated multidrug resistant (MDR) tumor cell lines; however, due to its poor solubility and high toxicity, PPT cannot be dosed systemically, preventing its clinical use for MDR cancer. We developed a nanoparticle dosage form of PPT by covalently conjugating PPT and polyethylene glycol (PEG) with acetylated carboxymethyl cellulose (CMC-Ac) using one-pot esterification chemistry. The polymer conjugates self-assembled into nanoparticles (NPs) of variable sizes (20-120 nm) depending on the PPT-to-PEG molar ratio (2-20). The conjugate with a low PPT/PEG molar ratio of 2 yielded NPs with a mean diameter of 20 nm and released PPT at ∼5%/day in serum, while conjugates with increased PPT/PEG ratios (5 and 20) produced bigger particles (30 nm and 120 nm respectively) that displayed slower drug release (∼2.5%/day and ∼1%/day respectively). The 20 nm particles exhibited 2- to 5-fold enhanced cell killing potency and 5- to 20-fold increased tumor delivery compared to the larger NPs. The biodistribution of the 20 nm PPT-NPs was highly selective to the tumor with 8-fold higher accumulation than all other examined tissues, while the larger PPT-NPs (30 and 120 nm) exhibited increased liver uptake. Within the tumor, >90% of the 20 nm PPT-NPs penetrated to the hypovascular core, while the larger particles were largely restricted in the hypervascular periphery. The 20 nm PPT-NPs displayed significantly improved efficacy against MDR tumors in mice compared to the larger PPT-NPs, native PPT and the standard taxane chemotherapies, with minimal toxicity.

Novel isatin derivatives of podophyllotoxin: synthesis and cytotoxic evaluation against human leukaemia cancer cells as potent anti-MDR agents

Compound8cexhibited cytotoxicity at nanomolar range; induced G2/M cell cycle arrest accompanied by apoptosis and down-regulated the levels of Pgp, MRP-1 and GST-π.

Synthesis and biological evaluation of truncated α-tubulin-binding pironetin analogues lacking alkyl pendants in the side chain or the dihydropyrone ring

The preparation of several new truncated analogues of the natural dihydropyrone pironetin is described. They differ from the natural product mainly in the suppression of some of the alkyl pendants in either the side chain or the dihydropyrone ring. Their cytotoxic activity and their interactions with tubulin have been investigated. It has been found that all analogues are cytotoxic towards two either sensitive or resistant tumoral cell lines with similar IC50 values in each case, thus strongly suggesting that, like natural pironetin, they also display a covalent mechanism of action. Their cytotoxicity is, however, lower than that of the parent compound. This indicates that all alkyl pendants are necessary for the full biological activity, with the ethyl group at C-4 seemingly being particularly relevant. Most likely, the alkyl groups cause a restriction in the conformational mobility of the molecule and reduce the number of available conformations. This makes it more probable that the molecule preferentially adopts a shape which fits better into the binding point in α-tubulin.