Synthesis, characterization and biological activity of trans-platinum(II) and trans-platinum(IV) complexes with 4-hydroxymethylpyridine

Palladium and platinum complexes based on pyridine bases induced anticancer effectiveness via apoptosis protein signaling in cancer cells

Palladium and platinum complexes, especially those that include cisplatin, can be useful chemotherapeutic drugs. Alternatives that have less adverse effects and require lower dosages of treatment could be provided by complexes containing pyridine bases. The complexes [Pd(SCN)2(4-Acpy)2] (1), [Pd(N3)2(4-Acpy)2] (2) [Pd(paOH)2].2Cl (3) and [Pt(SCN)2(paO)2] (4) were prepared by self-assembly method at ambient temperature; (4-Acpy = 4-acetylpyridine and paOH = pyridine-2-carbaldehyde-oxime). The structure of complexes 1-4 was confirmed using spectroscopic and X-ray crystallography methods. Complexes 1-4 have similar features in isomerism that include the trans coordination geometry of pyridine ligands with Pd or Pt ion. The 3D network structure of complexes 1-4 was constructed by an infinite number of discrete mononuclear molecules extending via H-bonds. The Pd and Pt complexes 1-4 with pyridine ligands were assessed on MCF-7, T47D breast cancer cells and HCT116 colon cancer cells. The study evaluated cell death through apoptosis and cell cycle phases in MCF-7 cells treated with palladium or platinum conjugated with pyridine base. Upon treatment of MCF-7 with these complexes, the expression of apoptotic signals (Bcl2, p53, Bax and c-Myc) and cell cycle signals (p16, CDK1A, CDK1B) were evaluated. Compared to other complexes and cisplatin, IC50 of complex 1 was lowest in MCF-7 cells and complex 2 in T47D cells. Complex 4 has the highest effectiveness on HCT116. The selective index (SI) of complexes 1-4 has a value of more than two for all cancer cell lines, indicating that the complexes were less toxic to normal cells when given the same dose. MCF-7 cells treated with complex 2 and platinum complex 4 exhibited the highest level of early apoptosis. p16 may be signal arrest cells in Sub G, which was observed in cells treated with palladium complexes that suppress excessive cell proliferation. High c-Myc expression of treated cells with four complexes 1-4 and cisplatin could induce p53. All complexes 1-4 elevated the expression of Bax and triggered by the tumor suppressor gene p53. p53 was downregulating the expression of Bcl2.

Novel Phthalazin-1(2H)-One Derivatives Displaying a Dithiocarbamate Moiety as Potential Anticancer Agents

Nowadays, cancer disease seems to be the second most common cause of death worldwide. Molecular hybridization is a drug design strategy that has provided promising results against multifactorial diseases, including cancer. In this work, two series of phthalazinone-dithiocarbamate hybrids were described, compounds 6-8, which display the dithiocarbamate scaffold at N2, and compounds 9, in which this moiety was placed at C4. The proposed compounds were successfully synthesized via the corresponding aminoalkyl phthalazinone derivatives and using a one-pot reaction with carbon disulfide, anhydrous H₃PO₄, and different benzyl or propargyl bromides. The antiproliferative effects of the titled compounds were explored against three human cancer cell lines (A2780, NCI-H460, and MCF-7). The preliminary results revealed significant differences in activity and selectivity depending on the dithiocarbamate moiety location. Thus, in general terms, compounds 6-8 displayed better activity against the A-2780 and MCF-7 cell lines, while most of the analogues of the 9 group were selective toward the NCI-H460 cell line. Compounds 6e, 8e, 6g, 9a-b, 9d, and 9g with IC₅₀ values less than 10 µM were the most promising. The drug-likeness and toxicity properties of the novel phthalazinone-dithiocarbamate hybrids were predicted using Swiss-ADME and ProTox web servers, respectively.

Guanidine platinum(II) complexes: synthesis, in vitro antitumor activity, and DNA interactions

The novel guanidine compounds trans-[Pt(NH₂Me)₂{NH=C(NHMe)NR}₂](Cl)₂ (R = NEt₂ [7], NC₅H₁₀ [8]) (trans-7,8) were synthesized by the nucleophilic addition of methylamine to dialkylcyanamide ligands of the push–pull nitrile complexes trans-[PtCl₂(RCN)₂] (R = NEt₂, NC₅H₁₀). In vitro cytotoxicity tests conducted for the entire series of the guanidine complexes, i.e. trans-7,8, the neutral cis- or trans-[PtCl₂{NH=C(NH₂)R}₂] (cis-1–3 and trans-1–3) and the cationic cis- or trans-[Pt(NH₃)₂{NH=C(NH₂)R}₂](Cl)₂ (cis-4–6 and trans-4–6) (R = NMe₂ [1,4], NEt₂ [2,5], NC₅H₁₀ [3,6]) in two human cancer cell lines, CH1 (ovarian carcinoma) and SW480 (colon cancer), confirmed that the cytotoxicity of several trans-configured (trans-3,6) complexes is higher than that of cis-congeners (cis-3,6). Cellular platinum levels were analyzed by inductively coupled plasma mass spectrometry upon treatment of SW480 cells, revealing a dependence of cellular accumulation on the geometrical isomerism and the steric hindrance of the variable substituent R on the guanidine ligand. DNA interactions of selected guanidine complexes were studied in order to find hints for the possible reasons for their different activities. Changes induced to the electrophoretic mobility of a dsDNA plasmid confirmed the potency of the guanidine complexes (e.g. trans-1,3,5,6 and cis-1,3,4) to significantly alter DNA secondary structure, indicating DNA as a possible critical target of these compounds.

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A series of guanidine–Pt(II) complexes was extended with two new compounds.

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Structure–activity relationships were inferred from cell culture studies.

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New examples of active platinum complexes with trans geometry were identified.

Novel cis- and trans-configured bis(oxime)platinum(II) complexes: synthesis, characterization, and cytotoxic activity

Novel cis- and trans-configured bis(oxime)platinum(II) complexes have been synthesized and characterized by elemental analyses, IR, electrospray ionization mass spectrometry, multinuclear ((1)H, (13)C, and (195)Pt) NMR spectroscopy, and, in five cases, by X-ray diffraction. Their cytotoxicity was studied in the cisplatin-sensitive CH1 cell line as well as in inherently cisplatin-resistant SW480 cancer cells. Remarkably, every single dihalidobis(oxime)platinum(II) complex (with either a cis or trans configuration) shows a comparable cytotoxic potency in both cell lines, indicating a capacity of overcoming cisplatin resistance. Particularly strong cytotoxicities were observed in the case of trans-[PtCl(2)(R(2)C=NOH)(2)] (R = Me, n-Pr, i-Pr) with IC(50) values in the high nanomolar concentration range in both CH1 and SW480 cancer cells. These complexes are as potent as cisplatin in CH1 cells and up to 20 times more potent than cisplatin in SW480 cells. In comparison to transplatin, the novel compounds are up to 90 (CH1) and 120 times (SW480) more cytotoxic. The previously reported observation that the trans geometry yields a more active complex in the case of [PtCl(2)(Me(2)C=NOH)(2)] could be confirmed for at least two structural analogues.

Arene-Ru(II)-chloroquine complexes interact with DNA, induce apoptosis on human lymphoid cell lines and display low toxicity to normal mammalian cells

The complexes [Ru(eta(6)-p-cymene)(CQ)Cl(2)] (1), [Ru(eta(6)-benzene)(CQ)Cl(2)] (2), [Ru(eta(6)-p-cymene)(CQ)(H(2)O)(2)][BF(4)](2) (3), [Ru(eta(6)-p-cymene)(en)(CQ)][PF(6)](2) (4), [Ru(eta(6)-p-cymene)(eta(6)-CQDP)][BF(4)](2) (5) (CQ = chloroquine base; CQDP = chloroquine diphosphate; en = ethylenediamine) interact with DNA to a comparable extent to that of CQ and in analogous intercalative manner with no evidence for any direct contribution of the metal, as shown by spectrophotometric and fluorimetric titrations, thermal denaturation measurements, circular dichroism spectroscopy and electrophoresis mobility shift assays. Complexes 1-5 induced cytotoxicity in Jurkat and SUP-T1 cancer cells primarily via apoptosis. Despite the similarities in the DNA binding behavior of complexes 1-5 with those of CQ the antitumor properties of the metal drugs do not correlate with those of CQ, indicating that DNA is not the principal target in the mechanism of cytotoxicity of these compounds. Importantly, the Ru-CQ complexes are generally less toxic toward normal mouse splenocytes and human foreskin fibroblast cells than the standard antimalarial drug CQDP and therefore this type of compound shows promise for drug development.

Study by HPLC-MS of the interaction of platinum antitumor complexes with potato carboxypeptidase inhibitor (PCI)

The interaction of the well-known antitumor drug cisplatin cis-[PtCl(2)(NH(3))(2)] and the compound trans-[PtCl(2)NH(3)(4-hydroxymethylpyridine)] with the small protein potato carboxypeptidase inhibitor (PCI) and a PCI mutant in which glycine-39 was substituted by methionine has been followed by HPLC/mass spectrometry. Our results showed that both Pt drugs were able to bind PCI through Met-39 and histidines in mutated PCI, whereas only the trans complex interacted significantly with wild PCI. In the cytotoxic studies, the monofunctional adduct PCI-Met-cisplatin was neither more active nor more selective than cisplatin itself when tested against three tumor cell lines with different number of EGF receptors. Those results suggested that the poor activity of the adduct could be just due to the small fraction of cisplatin which was decoordinated from the adduct and able to penetrate the tumor cells, as well as to the changes in the structure of the platinum drug after the loss of NH(3) groups upon binding PCI-Met.

Synthesis, DNA interaction and cytotoxicity studies of cis-{[1, 2-bis(aminomethyl)cyclohexane]dihalo}platinum(II) complexes

A series of platinum compounds with an analogue structure to cisplatin have been synthesized and their biological activity against HL-60 cancer cell line has been studied. The interaction with DNA was evaluated by circular dichroism (CD), electrophoresis and atomic force microscopy (AFM) techniques showing slight but significant structure-dependent differences among the evaluated complexes. The cytotoxicity assays afforded interesting relationships between the structure and the biological activity, thus, a better antiproliferative activity was observed for the complexes with higher hydrophobicity: the methoxylated complexes showed better activity than the hydroxylated ones (17versus20 and 19versus21). Especially compound 22 having a fatty acid subunit presented a promising cytotoxic activity. On the other hand, dichloro complexes 12 and 13 had better activities than the diiodo complexes, probably due to their better metabolic stability. Between both dichloro complexes the aromatic one showed much higher activity, which could be rationalized on the basis of the intercalating ability of the benzene ring. The flow cytometry assays indicated that most of the complexes induced the cell death by apoptosis except for aromatic compound 12 and the lipophilic compound 22 that induced preferably a mechanism of necrosis.

Influence of the position of substituents in the cytotoxic activity of trans platinum complexes with hydroxymethyl pyridines

The synthesis and chemical characterization of two trans platinum complexes, (1) trans-[PtCl(2)NH(3)(2-hydroxymethylpyridine)] and (2) trans-[PtCl(2)NH(3)(3-hydroxymethylpyridine)], are described. The structures and chemical behaviour of these compounds have been compared to those of their isomer (3) trans-[PtCl(2)NH(3)(4-hydroxymethylpyridine)] previously studied. X-ray structures of all of them were solved and some interesting differences were found. The values of the dihedral angle (85 degrees , 57 degrees and 42 degrees for 1, 2 and 3, respectively) demonstrate how important is the position of substituent from a structural point of view. Studies of circular dichroism (CD), electrophoretic mobility (EM) in agarose gel and atomic force microscopy (AFM) showed differences in the modifications caused by the three complexes on DNA. Studies of antiproliferative activity of complexes 1 and 2 against cell tumour lines (HL-60) and apoptosis assays have also been carried out, showing that 1 as well as 2 are far less active than the previously described complex 3 (IC(50)=19; 19 and 3 microM, respectively). This fact probes that slight modifications on the drug's design may generate significant differences in the final antitumour activity by modifying the DNA-drug adducts, performance of resistance mechanisms and all the factors that play a fundamental role in Pt complexes' cytotoxicity.

Recognition of DNA modified by trans-[PtClNH(4-hydroxymethylpyridine)] by tumor suppressor protein p53 and character of DNA adducts of this cytotoxic complex

trans-[PtCl(2)NH(3)(4-Hydroxymethylpyridine)] (trans-PtHMP) is an analogue of clinically ineffective transplatin, which is cytotoxic in the human leukemia cancer cell line. As DNA is a major pharmacological target of antitumor platinum compounds, modifications of DNA by trans-PtHMP and recognition of these modifications by active tumor suppressor protein p53 were studied in cell-free media using the methods of molecular biology and biophysics. Our results demonstrate that the replacement of the NH(3) group in transplatin by the 4-hydroxymethylpyridine ligand affects the character of DNA adducts of parent transplatin. The binding of trans-PtHMP is slower, although equally sequence-specific. This platinum complex also forms on double-stranded DNA stable intrastrand and interstrand cross-links, which distort DNA conformation in a unique way. The most pronounced conformational alterations are associated with a local DNA unwinding, which was considerably higher than those produced by other bifunctional platinum compounds. DNA adducts of trans-PtHMP also reduce the affinity of the p53 protein to its consensus DNA sequence. Thus, downstream effects modulated by recognition and binding of p53 protein to DNA distorted by trans-PtHMP and transplatin are not likely to be the same. It has been suggested that these different effects may contribute to different antitumor effects of these two transplatinum compounds.