Exploring the Monoterpene Indole Alkaloid Scaffold for Reversing P-Glycoprotein-Mediated Multidrug Resistance in Cancer

Exploring the Anticancer Properties of 1,2,3-Triazole-Substituted Andrographolide Derivatives

Background/Objectives: The search for new anticancer agents from natural sources remains a key strategy in drug discovery. This study aimed to synthesize and evaluate novel triazole derivatives of the diterpenic lactone andrographolide for their antiproliferative activity against various cancer cell lines. Methods: Twenty-two new triazole derivatives (5-26), of the triacetyl derivative (2) of the diterpenic lactone andrographolide (1), were synthesized via the azide-alkyne "click reaction". The antiproliferative effects of compounds 1-26 were evaluated using the sulforhodamine B assay against a panel of cancer cell lines and a non-tumorigenic colon cell line. A representative compound, triazole derivative 12, was further evaluated in human pancreatic ductal adenocarcinoma (PANC-1) cells for its effects on the cell cycle, apoptosis, migration, and drug synergy with 5-fluorouracil. Results: Several compounds, specifically, 9, 14, 16, and 17, bearing a phenyl moiety, exhibited improved antiproliferative activity compared to the parental compound 1. Derivative 12, selected for further investigation, induced G2/M cell cycle arrest and apoptosis in a concentration-dependent manner. Additionally, this compound significantly reduced cell migration and demonstrated synergistic effects with 5-fluorouracil in PANC-1 cells. Conclusions: The synthesized andrographolide-based triazole derivatives, particularly compound 12, showed promising antiproliferative activity and mechanisms relevant to cancer therapy. These findings support their potential as lead compounds for further development in anticancer research.

Impact of V9302, a Competitive Antagonist of Transmembrane Glutamine Flux on Reversal of Resistance in Breast Cancer Cell Lines

Chemotherapy is a known treatment modality that improves the long-term survival of breast cancer patients. However, due to the resistance to numerous anticancer drugs, alternative chemotherapeutic strategies are required. Regarding antimetabolic drugs, several compounds have proven anticancer properties, such as statins. The present study aimed to investigate the in vitro effects of V9302, a competitive antagonist of glutamine flux, on different subtypes of breast cancers (estrogen, progesterone, and HER2 receptor-positive or negative, and Pgp-negative and Pgp-overexpressing). The interactions of V9302 with standard chemotherapeutic drugs (doxorubicin and cisplatin) were also determined by MTT staining on breast cancer cell lines. Furthermore, the influence of V9302 on the cell cycle of MCF-7 and its Pgp-overexpressing counterpart KCR was monitored by flow cytometry. It was shown that V9302 exerted synergistic interactions with doxorubicin in all breast cancer cell lines. In cell cycle analysis, the KCR cell line was more sensitive to V9302. After 48 h, cell proliferation was completely blocked, and elevated G1, suppressed S, and decreased G2/M could be detected. Inhibition of glutamate transport can be assumed to block resistance related to Pgp.

Nitrogen-containing andrographolide derivatives with multidrug resistance reversal effects in cancer cells

Multidrug resistance (MDR) remains a challenging issue in cancer treatment. Aiming at finding anticancer agents to overcome MDR, the triacetyl derivative (2) of the labdane diterpenoid lactone andrographolide (1) underwent the Michael-type addition reaction followed by elimination, yielding twenty-three new derivatives, bearing nitrogen-containing substituents (3-25). Their structures were assigned, mainly, by 1D and 2D NMR experiments. The MDR reversal potential of compounds 1-25 was assessed, by functional and chemosensitivity assays, using resistant human ABCB1-gene transfected L5178Y mouse lymphoma cells as a model. Several derivatives exhibited remarkable P-glycoprotein (P-gp) inhibitory ability. Compounds 13 and 20, bearing thiosemicarbazide moieties, were the most active exhibiting a strong MDR reversal effect at 2 μM. Some compounds showed selectivity towards the resistant cells, with compound 5 exhibiting a collateral sensitivity effect associated with significant antiproliferative activity (IC50 = 5.47 ± 0.22 μM). Moreover, all selected compounds displayed synergistic interaction with doxorubicin, with compound 3 being the most active. In the ATPase assay, selected compounds exhibited characteristics of P-gp inhibitors.

Lycorine and homolycorine derivatives for chemo-sensitizing resistant human ovarian adenocarcinoma cells

BACKGROUND

Multidrug resistance is the major obstacle to cancer chemotherapy. Modulation of P-glycoprotein and drug combination approaches have been considered important strategies to overcome drug resistance.

PURPOSE

Aiming at generating a small library of Amaryllidaceae-type alkaloids to overcome drug resistance, two major alkaloids, isolated from Pancratium maritimum, lycorine (1), and 2α-10bα-dihydroxy-9-O-demethylhomolycorine (2), were derivatized, giving rise to nineteen derivatives (3 - 21).

METHODS

The main chemical transformation of lycorine resulted from the cleavage of ring E of the diacetylated lycorine derivative (3) to obtain compounds that have carbamate and amine functions (5 - 16), while acylation of compound 2 provided derivatives 17 - 21. Compounds 1 - 21 were evaluated for their effects on cytotoxicity, and drug resistance reversal, using resistant human ovarian carcinoma cells (HOC/ADR), overexpressing P-glycoprotein (P-gp/ABCB1), as model.

RESULTS

Excluding lycorine (1) (IC50 values of 1.2- 2.5 µM), the compounds were not cytotoxic or showed moderate/weak cytotoxicity. Chemo-sensitization assays were performed by studying the in vitro interaction between the compounds and the anticancer drug doxorubicin. Most of the compounds have shown synergistic interactions with doxorubicin. Compounds 5, 6, 9 - 14, bearing both carbamate and aromatic amine moieties, were found to have the highest sensitization rate, reducing the dose of doxorubicin 5-35 times, highlighting their potential to reverse drug resistance in combination chemotherapy. Selected compounds (4 - 6, 9 - 14, and 21), able of re-sensitizing resistant cancer cells, were further evaluated as P-gp inhibitors. Compound 11, which has a para‑methoxy-N-methylbenzylamine moiety, was the strongest inhibitor. In the ATPase assay, compounds 9-11 and 13 behaved as verapamil, suggesting competitive inhibition of P-gp. At the same time, none of these compounds affected P-gp expression at the mRNA or protein level.

CONCLUSIONS

This study provided evidence of the potential of Amaryllidaceae alkaloids as lead candidates for the development of MDR reversal agents.

Lycorine Carbamate Derivatives for Reversing P-glycoprotein-Mediated Multidrug Resistance in Human Colon Adenocarcinoma Cells

Multidrug resistance (MDR) is a major challenge in cancer chemotherapy. Aiming at generating a small library of anticancer compounds for overcoming MDR, lycorine (1), a major Amaryllidaceae alkaloid isolated from Pancratium maritimum, was derivatized. Thirty-one new compounds (2-32) were obtained by chemical transformation of the hydroxyl groups of lycorine into mono- and di-carbamates. Compounds 1-32 were evaluated as MDR reversers, through the rhodamine-123 accumulation assay by flow cytometry and chemosensitivity assays, in resistant human colon adenocarcinoma cancer cells (Colo 320), overexpressing P-glycoprotein (P-gp, ABCB1). Significant inhibition of P-gp efflux activity was observed for the di-carbamate derivatives, mainly those containing aromatic substituents, at non-cytotoxic concentrations. Compound 5, bearing a benzyl substituent, and compounds 9 and 25, with phenethyl moieties, were among the most active, exhibiting strong inhibition at 2 µM, being more active than verapamil at 10-fold higher concentration. In drug combination assays, most compounds were able to synergize doxorubicin. Moreover, some derivatives showed a selective antiproliferative effect toward resistant cells, having a collateral sensitivity effect. In the ATPase assay, selected compounds (2, 5, 9, 19, 25, and 26) were shown to behave as inhibitors.

Interaction of a Homologous Series of Amphiphiles with P-glycoprotein in a Membrane Environment-Contributions of Polar and Non-Polar Interactions

The transport of drugs by efflux transporters in biomembranes limits their bioavailability and is a major determinant of drug resistance development by cancer cells and pathogens. A large number of chemically dissimilar drugs are transported, and despite extensive studies, the molecular determinants of substrate specificity are still not well understood. In this work, we explore the role of polar and non-polar interactions on the interaction of a homologous series of fluorescent amphiphiles with the efflux transporter P-glycoprotein. The interaction of the amphiphiles with P-glycoprotein is evaluated through effects on ATPase activity, efficiency in inhibition of [¹²⁵I]-IAAP binding, and partition to the whole native membranes containing the transporter. The results were complemented with partition to model membranes with a representative lipid composition, and details on the interactions established were obtained from MD simulations. We show that when the total concentration of amphiphile is considered, the binding parameters obtained are apparent and do not reflect the affinity for P-gp. A new formalism is proposed that includes sequestration of the amphiphiles in the lipid bilayer and the possible binding of several molecules in P-gp's substrate-binding pocket. The intrinsic binding affinity thus obtained is essentially independent of amphiphile hydrophobicity, highlighting the importance of polar interactions. An increase in the lipophilicity and amphiphilicity led to a more efficient association with the lipid bilayer, which maintains the non-polar groups of the amphiphiles in the bilayer, while the polar groups interact with P-gp's binding pocket. The presence of several amphiphiles in this orientation is proposed as a mechanism for inhibition of P-pg function.

Triterpenes from Momordica balsamina (African pumpkin): ABCB1 inhibition and synergistic interaction with doxorubicin in resistant cancer cells

Aiming at overcoming multidrug resistance (MDR) in cancer, we have been studying Momordica balsamina, a vegetable known as African pumpkin. Five undescribed cucurbitane-type triterpenoids (balsaminaepoxide, balsaminatriol, balsaminoic acid, balsaminal, and balsaminol G) along with five known cucurbitacins were isolated from the methanol extract of Momordica balsamina aerial parts, whose structures were elucidated by spectroscopic data, mainly 1D and 2D NMR experiments. Compounds were evaluated for their ability as P-glycoprotein (P-gp/ABCB1) inhibitors in multidrug resistant human ABCB1-transfected mouse lymphoma cells (L5178Y, MDR) and resistant human colon adenocarcinoma cells (COLO 320), using the rhodamine-123 exclusion test, by flow cytometry. Several compounds, which were found to be non-cytotoxic, strongly inhibited P-gp efflux activity in a dose-dependent manner in both cell models. In MRD mouse lymphoma cells, balsaminol G and karavilagenin B were the most active, while in resistant colon adenocarcinoma cells, the strongest inhibitory activity was found for balsaminaepoxide, balsaminatriol and karavilagenin C, being several-fold more active than the positive control verapamil. In chemosensitivity assays, in a model of combination chemotherapy, selected compounds showed to interact synergistically with doxorubicin, thus substantiating their potential as MDR reversers. The strongest synergistic interaction was found for balsaminal and balsaminol G.

5-Arylidenerhodanines as P-gp Modulators: An Interesting Effect of the Carboxyl Group on ABCB1 Function in Multidrug-Resistant Cancer Cells

Multidrug resistance (MDR) is considered one of the major mechanisms responsible for the failure of numerous anticancer and antiviral chemotherapies. Various strategies to overcome the MDR phenomenon have been developed, and one of the most attractive research directions is focused on the inhibition of MDR transporters, membrane proteins that extrude cytotoxic drugs from living cells. Here, we report the results of our studies on a series newly synthesized of 5-arylidenerhodanines and their ability to inhibit the ABCB1 efflux pump in mouse T-lymphoma cancer cells. In the series, compounds possessing a triphenylamine moiety and the carboxyl group in their structure were of particular interest. These amphiphilic compounds showed over 17-fold stronger efflux pump inhibitory effects than verapamil. The cytotoxic and antiproliferative effects of target rhodanines on T-lymphoma cells were also investigated. A putative binding mode for 11, one of the most potent P-gp inhibitors tested here, was predicted by molecular docking studies and discussed with regard to the binding mode of verapamil.

Amaryllidaceae-Type Alkaloids from Pancratium maritimum: Apoptosis-Inducing Effect and Cell Cycle Arrest on Triple-Negative Breast Cancer Cells

Aiming to find Amaryllidaceae alkaloids against breast cancer, including the highly aggressive triple-negative breast cancer, the phytochemical study of Pancratium maritimum was carried out. Several Amaryllidaceae-type alkaloids, bearing scaffolds of the haemanthamine-, homolycorine-, lycorine-, galanthamine-, and tazettine-type were isolated (3–11), along with one alkamide (2) and a phenolic compound (1). The antiproliferative effect of compounds (1–11) was evaluated by the sulforhodamine B assay against triple-negative breast cancer cell lines MDA-MB-231 and MDA-MB-468, breast cancer cells MCF-7, and the non-malignant fibroblast (HFF-1) and breast (MCF12A) cell lines. The alkaloids 3, 5, 7, and 11 showed significant growth inhibitory effects against all breast cancer cell lines, with IC₅₀ (half-maximal inhibitory concentration) values ranging from 0.73 to 16.3 µM. The homolycorine-type alkaloid 7 was selected for further investigation in MDA-MB-231 cells. In the annexin-V assay, compound 7 increased cell death by apoptosis, which was substantiated, in western blot analyses, by the increased expression of the pro-apoptotic protein Bax, and the decreased expression of the anti-apoptotic protein Bcl-xL. Consistently, it further stimulated mitochondrial reactive oxygen species (ROS) generation. The antiproliferative effect of compound 7 was also associated with G2/M cell cycle arrest, which was supported by an increase in the p21 protein expression levels. In MDA-MB-231 cells, compound 7 also exhibited synergistic effects with conventional chemotherapeutic drugs such as etoposide.

Molecular Modeling Strategies of Cancer Multidrug Resistance

Cancer remains a leading cause of morbidity and mortality worldwide. Hence, the increase in cancer cases observed in the elderly population, as well as in children and adolescents, makes human malignancies a prime target for anticancer drug development. Although highly effective chemotherapeutic agents are continuously developed and approved for clinical treatment, the major impediment towards curative cancer therapy remains multidrug resistance (MDR). In recent years, intensive studies have been carried out on the identification of new therapeutic molecules to reverse MDR efflux transporters of the ATP-binding cassette (ABC) superfamily. Although a great deal of progress has been made in the development of specific inhibitors for certain MDR efflux pumps in experimental studies, advanced computational studies can accelerate this drug development process. In the literature, there are many experimental studies on the impact of natural products and synthetic small molecules on the reversal of cancer MDR. Molecular modeling methods provide an opportunity to explain the activity of these molecules on the ABC-transporter family with non-covalent interactions as well as it is possible to carry out studies for the discovery of new anticancer drugs specific to MDR with these methods. The coordinate file of the 3-dimensional (3D) structure of the target protein is indispensable for molecular modeling studies. In some cases where a 3D structure cannot be obtained by experimental methods, the homology modeling method can be applied to obtain the file containing the target protein's information including atomic coordinates, secondary structure assignments, and atomic connectivity. Homology modeling studies are of great importance for efflux transporter proteins that still lack 3D structures due to crystallization problems with multiple hydrophobic transmembrane domains. Quantum mechanics, molecular docking and molecular dynamics simulation applications are the most frequently used molecular modeling methods in the literature to investigate non-covalent interactions between the drug-ABC transporter superfamily. The quantitative structure-activity relationship (QSAR) model provides a relationship between the chemical properties of a compound and its biological activity. Determining the pharmacophore region for a new drug molecule by superpositioning a series of molecules according to their physicochemical properties using QSAR models is another method in which molecular modeling is used in computational drug development studies with ABC transporter proteins. There are also in silico absorption, distribution, metabolism, excretion, and toxicity (ADME/Tox) studies conducted to make a prediction about the pharmacokinetic properties, and drug-likeness of new molecules. Drug repurposing studies, which have become a trending topic in recent years, involve identifying possible new targets for an already approved drug molecule. There are few studies in the literature in which drug repurposing performed by molecular modelling methods has been applied on ABC transporter proteins. The aim of the current paper is to create a complete review of drug development studies including aforementioned molecular modeling methods carried out between the years 2019-2021. Furthermore, an intensive investigation is also conducted on licensed applications and free web servers used in in silico studies. The current review is an up-to-date guide for researchers who plan to conduct computational studies with MDR transporter proteins.