Elucidation of chemosensitization effect of acridones in cancer cell lines: Combined pharmacophore modeling, 3D QSAR, and molecular dynamics studies.

Overexpression of P-glycoprotein (P-gp) leads to the emergence of multidrug resistance (MDR) in cancer treatment. Acridones have the potential to reverse MDR and sensitize cells. In the present study, we aimed to elucidate the chemosensitization potential of acridones by employing various molecular modelling techniques. Pharmacophore modeling was performed for the dataset of chemosensitizing acridones earlier proved for cytotoxic activity against MCF7 breast cancer cell line. Gaussian-based QSAR studies also performed to predict the favored and disfavored region of the acridone molecules. Molecular dynamics simulations were performed for compound 10 and human P-glycoprotein (obtained from Homology modeling). An efficient pharmacophore containing 2 hydrogen bond acceptors and 3 aromatic rings (AARRR.14) was identified. NCI 2012 chemical database was screened against AARRR.14 CPH and identified 25 best-fit molecules. Potential regions of the compound were identified through Field (Gaussian) based QSAR. Regression analysis of atom-based QSAR resulted in r2 of 0.95 and q2 of 0.72, whereas, regression analysis of field-based QSAR resulted in r2 of 0.92 and q2 of 0.87 along with r2cv as 0.71. The fate of the acridone molecule (compound 10) in the P-glycoprotein environment is analyzed through analyzing the conformational changes occurring during the molecular dynamics simulations. Combined data of different in silico techniques provided basis for deeper understanding of structural and mechanistic insights of interaction phenomenon of acridones with P-glycoprotein and also as strategic basis for designing more potent molecules for anti-cancer and multidrug resistance reversal activities.

Nitric oxide releasing acridone carboxamide derivatives as reverters of doxorubicin resistance in MCF7/Dx cancer cells.

A series of nitric oxide donating acridone derivatives are synthesized and evaluated for in vitro cytotoxic activity against different sensitive and resistant cancer cell lines MCF7/Wt, MCF7/Mr (BCRP overexpression) and MCF7/Dx (P-gp expression). The results showed that NO-donating acridones are potent against both the sensitive and resistant cells. Structure activity relationship indicate that the nitric oxide donating moiety connected through a butyl chain at N(10) position as well as morpholino moiety linkage through an amide bridge on the acridone ring system at C-2 position, are required to exert a good cytotoxic effect. Further, good correlations were observed when cytotoxic properties were compared with in vitro nitric oxide release rate, nitric oxide donating group potentiated the cytotoxic effect of the acridone derivatives. Exogenous release of nitric oxide by NO donating acridones enhanced the accumulation of doxorubicin in MCF7/Dx cell lines when it was coadministered with doxorubicin, which inhibited the efflux process of doxorubicin. In summary, a nitric oxide donating group can potentiate the anti-MDR property of acridones.

Chemosensitizing acridones: in vitro calmodulin dependent cAMP phosphodiesterase inhibition, docking, pharmacophore modeling and 3D QSAR studies.

Calmodulin inhibitors have proved to play a significant role in sensitizing MDR cancer cells by interfering with cellular drug accumulation. The present investigation focuses on the evaluation of in vitro inhibitory efficacy of chloro acridones against calmodulin dependent cAMP phosphodiesterase (PDE1c). Moreover, molecular docking of acridones was performed with PDE1c in order to identify the possible protein ligand interactions and results thus obtained were compared with in vitro data. In addition an efficient pharmacophore model was developed from a set of 38 chemosensitizing acridones effective against doxorubicin resistant (HL-60/DX) cancer cell lines. Pharmacophoric features such as one hydrogen bond acceptor, one hydrophobic region, a positive ion group and three aromatic rings i.e., AHPRRR have been identified. Ligand based 3D-QSAR was also performed by employing partial least square regression analysis.

Cytotoxicity studies of some novel fluoro acridone derivatives against sensitive and resistant cancer cell lines and their mechanistic studies.

A series of novel N(10)-substituted acridone derivatives bearing alkyl side-chain with tertiary amine groups at the terminal position were evaluated for their in vitro cytotoxic effects against drug sensitive and resistant cancer cell lines. All the molecules were designed on the basis of hydrogen bond acceptors, carbonyl, fluoro groups with precise spatial separation and structural features of lipophilicity, positive charge at neutral pH and presence of aromatic rings. The in vitro cytotoxic effects in comparison with reference drugs doxorubicin (DX) and C(1311) against cancer cell lines SW 1573, SW 1573 2R 160 (Pg-P expressing) which are non-small cell lung cancer cells, human embryo kidney cells HEK 293, HEK 293 MRP4, HEK 293 MRP5i, human promyelocytic leukemia sensitive cell line HL-60, including its multidrug cross-resistant of two main (P-gp and MRP) phenotype sublines vincristine resistant HL-60/VINC and doxorubicin resistant HL-60/DX cancer cell lines are presented. Compounds 14, 15 and 16 exhibited highest cytotoxicity among the derivatives. On the other hand, the in vitro cytotoxic activity of compound 14 (with butyl side-chain and tertiary amino group ß-hydroxy ethyl piperizine) against resistant cancer cell lines indicate that it might be a promising new hit for further development as an anti-MDR agent. The non-covalent interaction of these molecules with DNA duplexes have been investigated by ESI-MS technique. The results indicate, these acridone derivatives interact with duplex DNA by intercalation, possesses higher affinity to GC than AT base pairs of the DNA and they could not interact non-covalently with the minor grooves of the DNA. The ability of acridones to inhibit calmodulin dependent cAMP phosphodiesterase has been determined. The results suggest that acridones inhibit the Ca(2+)/calmodulin stimulated cAMP-phosphodiesterase activity and have no direct effects on the enzyme itself and a strong correlation between calmodulin inhibition and cytotoxicity against HL-60/VINC and HL-60/DX MDR cancer cell lines.

Chloro acridone derivatives as cytotoxic agents active on multidrug-resistant cell lines and their duplex DNA complex studies by electrospray ionization mass spectrometry.

We report herein in vitro anti-proliferative activity and duplex DNA complex studies of a series of N10-substituted acridone derivatives. All the molecules have been designed on the basis of the presence of specific recognition patterns consisting of hydrogen bond acceptors (or electron donors), carbonyl, chloro groups with precise spatial separation and structural features (lipophilicity, positive charge at neutral pH and presence of aromatic rings). The in vitro cytotoxic effects have been demonstrated against human promyelocytic leukemia sensitive cell line (HL-60), including its multidrug cross-resistance of two main (P-gp and MRP) phenotype sublines vincristine-resistant (HL-60/VINC) and doxorubicin-resistant (HL-60/DX) cancer cell lines. Compound 4 showed very good activity against sensitive and resistant cell lines. The noncovalent complexes of these molecules with DNA duplex has been investigated in gas phase by using a fast, robust and sensitive electrospray ionization mass spectrometry (ESI-MS) technique. Equilibrium association constants (K1) and percentage of intact complexes were determined. The combined results show that these acridone derivatives interact with DNA duplex by intercalation between the base pairs, possess higher affinity to GC than AT base pairs of the DNA and they could not interact noncovalently with the minor grooves of the DNA in solution-free gas phase. Examination of the relationship between lipophilicity and cytotoxic properties of acridone derivatives showed a poor correlation. The in vitro cytotoxic studies in resistant cancer cell lines of compound 4 showed that it might be a promising new hit for further development of anti-MDR agent.