Combining the platinum(ii) drug candidate kiteplatin with 1,10-phenanthroline analogues

Platinum complexes of the type [Pt(PL)(AL)]2+ where PL is a derivative of 1,10-phenanthroline and AL is cis-1,4-diaminocyclohexane (1,4-dach), have been synthesised and characterised by ultraviolet spectroscopy, elemental microanalysis, nuclear magnetic resonance and X-ray crystallography. The calf-thymus DNA binding affinity of these complexes was determined by isothermal titration calorimetry, revealing higher DNA affinity than their 1S,2S-diaminocyclohexane analogues. In vitro cytotoxicity was assessed in eleven human cell lines, revealing unexpectedly low activity for the 1,4-dach complexes

Cyclooxygenase-inhibiting platinum(IV) prodrugs with potent anticancer activity

Platinum(IV) prodrugs of the [Pt(PL)(AL)(COXi)(OH)]2+ type scaffold (where PL is 1,10-phenanthroline or 5,6-dimethyl-1,10-phenanthroline, AL is 1S,2S-diaminocyclohexane, and COXi is a COX inhibitor, either indomethacin or aspirin) were synthesised and characterised, and their biological activity was explored. MTT assays showed that these complexes exhibit outstanding activity against a range of cancer cell lines, and nanomolar activities were observed. The most potent complex, 4, exhibited a GI50 of 3 nM in the Du145 prostate cancer cell line and was observed to display a 1614-fold increased activity against the HT29 colon cancer cell line relative to cisplatin. ICP-MS studies showed a linear correlation between increased cellular accumulation of the complexes and increased cytotoxicity, while an enzyme immunoassay showed that 1 and 2 inhibited COX-2 at 14 and 1.4 µM, respectively, which is comparable to the inhibition exhibited by indomethacin. These results suggest that while the cytotoxicity of prodrugs 1–4 was influenced by cellular uptake, it was not entirely dependent on either COX inhibition or lipophilicity

o-Vanillin derived Schiff Bases and their Organotin(IV) Compounds: Synthesis, structural characterisation, in-Silico studies and cytotoxicity

Six new organotin(IV) compounds of Schiff bases derived from S-R-dithiocarbazate [R = benzyl (B), 2- or 4-methylbenzyl (2M and 4M, respectively)] condensed with 2-hydroxy-3- methoxybenzaldehyde (oVa) were synthesised and characterised by elemental analysis, various spectroscopic techniques including infrared, UV-vis, multinuclear (1H, 13C, 119Sn) NMR and mass spectrometry, and single crystal X-ray diffraction. The organotin(IV) compounds were synthesised from the reaction of Ph2SnCl2 or Me2SnCl2 with the Schiff bases (S2MoVaH/S4MoVaH/SBoVaH) to form a total of six new organotin(IV) compounds that had a general formula of [R2Sn(L)] (where L = Schiff base; R = Ph or Me). The molecular geometries of Me2Sn(S2MoVa), Me2Sn(S4MoVa) and Me2Sn(SBoVa) were established by X-ray crystallography and verified using density functional theory calculations. Interestingly, each experimental structure contained two independent but chemically similar molecules in the crystallographic asymmetric unit. The coordination geometry for each molecule was defined by thiolate-sulphur, phenoxide-oxygen and imine-nitrogen atoms derived from a dinegative, tridentate dithiocarbazate ligand with the remaining positions occupied by the methyl-carbon atoms of the organo groups. In each case, the resulting five-coordinate C2NOS geometry was almost exactly intermediate between ideal trigonal-bipyramidal and squarepyramidal geometries. The cytotoxic activities of the Schiff bases and organotin(IV) compounds were investigated against EJ-28 and RT-112 (bladder), HT29 (colon), U87 and SJ-G2 (glioblastoma), MCF-7 (breast) A2780 (ovarian), H460 (lung), A431 (skin), DU145 (prostate), BE2-C (neuroblastoma) Int. J. Mol. Sci. 2019, 20, 854 2 of 34 and MIA (pancreatic) cancer cell lines and one normal breast cell line (MCF-10A). Diphenyltin(IV) compounds exhibited greater potency than either the Schiff bases or the respective dimethyltin(IV) compounds. Mechanistic studies on the action of these compounds against bladder cancer cells revealed that they induced the production of reactive oxygen species (ROS). The bladder cancer cells were apoptotic after 24 h post-treatment with the diphenyltin(IV) compounds. The interactions of the organotin(IV) compounds with calf thymus DNA (CT-DNA) were experimentally explored using UV-vis absorption spectroscopy. This study revealed that the organotin(IV) compounds have strong DNA binding affinity, verified via molecular docking simulations, which suggests that these organotin(IV) compounds interact with DNA via groove-binding interactions

Tin(IV) compounds of tridentate thiosemicarbazone Schiff bases: synthesis, characterization, in-silico analysis and in vitro cytotoxicity

Twelve tin(IV) compounds ( 5 - 16 ) derived from four tridentate thiosemicarbazone Schiff bases of 4-methyl-3-thiosemicarbazide with 2-hydroxy-3-methoxybenzaldehyde ( 1, 2 ) and 4-phenyl-3-thiosemicarbazide with 2,3-dihydroxybenzaldehyde ( 3, 4 ) of general formulae of [R 2 Sn(L n )] and [Sn(L n ) 2 ] (where R = Ph or Me; L n = 1 , 2 , 3 and 4 ) were synthesized and characterized by elemental analysis, IR, UVvis, mass spectrometry and multinuclear NMR ( 1 H, 13 C and 119 Sn) spectroscopy. X-ray crystallographic data was obtained for 11′ , a 2:1 co-crystal between Ph 2 Sn(L 2 ) ( 11 ) and 3-methoxysalicylaldehyde azine, and Me 2 Sn(L 2 ) ( 12 ); L 2 H 2 is 2-(2-hydroxy-3-methoxybenzylidene)-Nphenylhydrazinecarbothioamide. The analysis revealed distinct coordination geometries with 11 and 12 approaching trigonal-bipyramidal. In the crystal of 11′ , supramolecular dimers arising from amine-N–H … S(thiolate) hydrogen bonding and {… HNCS} 2 synthons are evident; π(chelate ring) … π(oxidobenzylidene) stacking is also apparent. In the crystal of 12 , supramolecular, helical chains are generated by a combination of amine-N–H … O(phenoxide) hydrogen bonding and Sn … S secondary bonding. The cytotoxic activity of the compounds against a panel of ten cancer cell lines, [HT29 (colon), U87 and SJ-G2 (glioblastoma), MCF-7 (breast), A2780 (ovarian), H460 (lung), A431 (skin), DU145 (prostate), BE2-C (neuroblastoma), and MIA (pancreas) and one normal cell line, MCF-10A (normal breast)] were investigated. The thiosemicarbazone Schiff bases 1 and 4 as well as the diphenyltin(IV) compounds showed a strong ability to inhibit the growth of cancer cells, with particular selectivity against HT29, MCF-7, A2780, A431, BE2-C, SJ-G2, and MIA cell lines. The structure-activity relationship of all these compounds were studied by evaluating the effect of alkyl and aryl groups attached at the thiosemicarbazone backbone, the methoxy/hydroxyl groups present at the meta -position of the phenyl ring and alkyl or aryl groups bound to the tin center

Homoleptic tin(IV) compounds containing tridentate ONS dithiocarbazate Schiff bases: Synthesis, X-ray crystallography, DFT and cytotoxicity studies

Six new tin(IV) compounds derived from tridentate dinegatively charged ONS dithiocarbazate Schiff bases derived from 2-hydroxy-3-methoxybenzaldehyde (H2L1, H2L2 and H2L3) and 2,3-dihydroxybenzaldehyde (H2L4, H2L5 and H2L6) (where H2Ln = di-acids of Schiff base) are reported. The compounds were characterised by elemental analysis, FT-IR and multinuclear NMR (1H, 13C and 119Sn) spectroscopy. The crystal structures of tin(IV) [S-4-methybenzyl-β-N-(2-hydroxy-3-methoxybenzylmethylene)dithiocarbazate] (2) and tin(IV) [S-benzyl-β-N-(2-hydroxy-3-methoxy benzylmethylene)dithiocarbazate] (3) were determined by X-ray single crystal diffraction analysis. X-ray crystallography showed the molecular geometries in homoleptic 2 and 3 to be quite similar in which the dinegative tridentate ligand coordinated the tin atoms via thiolate-S, phenoxide-O and imine-N atoms. The coordination geometries are based on an octahedron with like-atoms mutually trans. The experimental findings were validated by density functional theory (DFT) calculations at the B3LYP/LanL2DZ/6-311G(d,p) level of theory. All the tin(IV) compounds, except the insoluble compound 2 were screened for their in vitro cytotoxicity against a panel ten of cancer cell lines and one normal breast cell line (MCF-10 A) by MTT assay. Interestingly, the cytotoxicity of five tin(IV) compounds against HT29, MCF7 and MIA was higher than the reference drug, cisplatin

Synergistic Apoptosis Induction in Leukemic Cells by the Phosphatase Inhibitor Salubrinal and Proteasome Inhibitors

Cells adapt to endoplasmic reticulum (ER)-stress by arresting global protein synthesis while simultaneously activating specific transcription factors and their downstream targets. These processes are mediated in part by the phosphorylation-dependent inactivation of the translation initiation factor eIF2alpha. Following restoration of homeostasis protein synthesis is resumed when the serine/threonine-protein phosphatase PP1 dephosphorylates and reactivates eIF2alpha. Proteasome inhibitors, used to treat multiple myeloma patients evoke ER-stress and apoptosis by blocking the ER-associated degradation of misfolded proteins (ERAD), however, the role of eIF2alpha phosphorylation in leukemic cells under conditions of proteasome inhibitor-mediated ER stress is currently unclear.Bcr-Abl-positive and negative leukemic cell lines were used to investigate the functional implications of PP1-related phosphatase activities on eIF2alpha phosphorylation in proteasome inhibitor-mediated ER stress and apoptosis. Rather unexpectedly, salubrinal, a recently identified PP1 inhibitor capable to protect against ER stress in various model systems, strongly synergized with proteasome inhibitors to augment apoptotic death of different leukemic cell lines. Salubrinal treatment did not affect the phosphorlyation status of eIF2alpha. Furthermore, the proapoptotic effect of salubrinal occurred independently from the chemical nature of the proteasome inhibitor, was recapitulated by a second unrelated phosphatase inhibitor and was unaffected by overexpression of a dominant negative eIF2alpha S51A variant that can not be phosphorylated. Salubrinal further aggravated ER-stress and proteotoxicity inflicted by the proteasome inhibitors on the leukemic cells since characteristic ER stress responses, such as ATF4 and CHOP synthesis, XBP1 splicing, activation of MAP kinases and eventually apoptosis were efficiently abrogated by the translational inhibitor cycloheximide.Although PP1 activity does not play a major role in regulating the ER stress response in leukemic cells, phosphatase signaling nevertheless significantly limits proteasome inhibitor-mediated ER-stress and apoptosis. Inclusion of specific phosphatase inhibitors might therefore represent an option to improve current proteasome inhibitor-based treatment modalities for hematological cancers

A Systems Biology Approach Reveals the Role of a Novel Methyltransferase in Response to Chemical Stress and Lipid Homeostasis

Using small molecule probes to understand gene function is an attractive approach that allows functional characterization of genes that are dispensable in standard laboratory conditions and provides insight into the mode of action of these compounds. Using chemogenomic assays we previously identified yeast Crg1, an uncharacterized SAM-dependent methyltransferase, as a novel interactor of the protein phosphatase inhibitor cantharidin. In this study we used a combinatorial approach that exploits contemporary high-throughput techniques available in Saccharomyces cerevisiae combined with rigorous biological follow-up to characterize the interaction of Crg1 with cantharidin. Biochemical analysis of this enzyme followed by a systematic analysis of the interactome and lipidome of CRG1 mutants revealed that Crg1, a stress-responsive SAM-dependent methyltransferase, methylates cantharidin in vitro. Chemogenomic assays uncovered that lipid-related processes are essential for cantharidin resistance in cells sensitized by deletion of the CRG1 gene. Lipidome-wide analysis of mutants further showed that cantharidin induces alterations in glycerophospholipid and sphingolipid abundance in a Crg1-dependent manner. We propose that Crg1 is a small molecule methyltransferase important for maintaining lipid homeostasis in response to drug perturbation. This approach demonstrates the value of combining chemical genomics with other systems-based methods for characterizing proteins and elucidating previously unknown mechanisms of action of small molecule inhibitors

Physicochemical Properties, Antioxidant and Cytotoxic Activities of Crude Extracts and Fractions from Phyllanthus amarus

Background: Phyllanthus amarus (P. amarus) has been used as a medicinal plant for the prevention and treatment of chronic ailments such as diabetes, hepatitis, and cancer. Methods: The physicochemical properties, antioxidant and cytotoxic activities of crude extracts and fractions from P. amarus were determined using spectrophotometric method. Results: The P. amarus methanol (PAM) extract had lower levels of residual moisture (7.40%) and water activity (0.24) and higher contents of saponins, phenolics, flavonoids, and proanthocyanidins (1657.86 mg escin equivalents, 250.45 mg gallic acid equivalents, 274.73 mg rutin equivalents and 61.22 mg catechin equivalents per g dried extract, respectively) than those of the P. amarus water (PAW) extract. The antioxidant activity of PAM extract was significantly higher (p < 0.05) than that of the PAW extract, PAM fractions, and phyllanthin (known as a major compound in the P. amarus). Higher cytotoxic activity of PAM extract based on MTT assay on different cell lines including MiaPaCa-2 (pancreas), HT29 (colon), A2780 (ovarian), H460 (lung), A431 (skin), Du145 (prostate), BE2-C (neuroblastoma), MCF-7 (breast), MCF-10A (normal breast), and U87, SJ-G2, SMA (glioblastoma) was observed in comparison to the PAW extract and PAM fractions. The cytotoxic potential of the PAW extract (200 μg/mL), based on the CCK-8 assay on a pancreatic cancer cell line (MiaCaPa2) was significantly lower (p < 0.05) than those of gemcitabine (50 nM) and a saponin-enriched extract from quillajia bark at 200 μg/mL (a commercial product), but was significantly higher than that of phyllanthin at 2 μg/mL. Conclusions: The results achieved from this study reveal that the PA extracts are a potential source for the development of natural antioxidant products and/or novel anticancer drugs