Ana Zamora

Dual Antitumor and Antiangiogenic Activity of Organoplatinum(II) Complexes

A library of over 20 cycloplatinated compounds of the type [Pt(dmba-R)LCl] (dmba-R = C,N-dimethylbenzylamine-like ligand; R being MeO, Me, H, Br, F, CF3, and NO2 substituents in the R5 or R4 position of the phenyl ring; L = DMSO and P(C6H4CF3-p)3) has been prepared. All compounds are active in both human ovarian carcinoma A2780 cells and cisplatin-resistant A2780cisR cells, with most of the DMSO platinum complexes exhibiting IC50 values in the submicromolar range in the A2780 cell line. Interestingly, DMSO platinum complexes show low cytotoxicity in the nontumorigenic kidney cell line BGM and therefore high selectivity factors SF. In addition, some of the DMSO platinum complexes effectively inhibit angiogenesis in the human umbilical vein endothelial cell line EA.hy926. These are the first platinum(II) complexes reported to inhibit angiogenesis at a close concentration to their IC50 in A2780 cells, turning them into dual cytotoxic and antiangiogenic compounds.

Anticancer C,N-Cycloplatinated(II) Complexes Containing Fluorinated Phosphine Ligands: Synthesis, Structural Characterization, and Biological Activity

A series of potent C,N-cycloplatinated(II) phosphine antitumor complexes containing fluorous substituents in the cyclometalated or the ancillary phosphine ligands [Pt(C-N)(PR3)Cl] or both have been synthesized and characterized. The crystal structure of [Pt(dmba){P(C6H4CF3-p)3}Cl]·2CH2Cl2 (dmba = dimethylaminomethyl)phenyl) has been established by X-ray diffraction. Values of IC50 of the new platinum complexes were calculated toward a panel of human tumor cell lines representative of ovarian (A2780 and A2780cisR) and breast cancers (T47D). Complexes containing P(C6H4CF3-p)3 as ancillary ligand (with a bulky and electronegative CF3 substituent in para position) were the most cytotoxic compounds in all the tested cancer cell lines. In some cases, the IC50 values were 16-fold smaller than that of cisplatin and 11-fold smaller than the non-fluorous analogue [Pt(dmba)(PPh3)Cl]. On the other hand, very low resistance factors (RF) in A2780cisR (cisplatin-resistant ovarian carcinoma) at 48 h were observed (RF ≈ 1) for most of the new compounds. Analysis of cell cycle was done for the three more active compounds in A2780. They arrest cell growth in G0/G1 phase in contrast to cisplatin (S phase) with a high incidence of late-stage apoptosis. They are also good cathepsin B inhibitors (an enzyme implicated in a number of cancer related events).

New steroidal 7-azaindole platinum(II) antitumor complexes ☆

Two new steroidal 7-azaindole-based N-donor ligands 17-α-[7-azaindole-5-ethynyl]-17-β-testosterone (ET-Haza) (1) and 17-α-[7-azaindole-5-ethynyl]-19-nortestosterone (LEV-Haza) (2), and two new DNA damaging warheads with an enhanced lipophilicity [Pt(dmba)Cl(L)] (dmba=N,N-dimethylbenzylamine-κN,κC; L=ET-Haza (3) and LEV-Haza (4)) have been prepared and characterized. Values of IC50 were calculated for complexes 3 and 4 against a panel of human tumor cell lines representative of ovarian (A2780 and A2780cis) and breast cancers (T47D). At 48 h of incubation time 3 and 4 showed very low resistance factors (RF of 1) against an A2780 cell line which has acquired resistance to cisplatin, IC50 values of the new complexes towards normal human LLC-PK1 renal cells at 48 h being about double than that of cisplatin. 3 and 4 are able to react with 9-ethylguanine (9-EtG) yielding the corresponding monoadduct [Pt(dmba)(L)(9-EtG)](+) derivatives as followed by ESI-MS. Compound 3 interacts mainly with double-stranded (DS) oligonucleotides as shown by analysis with ESI-TOF-MS, being also able to displace ethidium bromide (EB) from DNA, as observed by an electrophoretic mobility study. 3 and 4 are good cathepsin B inhibitors. Theoretical calculations at the COSMO(CHCl3)/B3LYP-D/def2-TZVPPecp//B3LYP-D/def2-TZVPecp level and energy evaluations at the COSMO(CHCl3)/PWPB95-D3/def2-TZVPPecp level of theory on compound 4 and model systems have been done.

New Acridine Thiourea Gold(I) Anticancer Agents: Targeting the Nucleus and Inhibiting Vasculogenic Mimicry

Two new 1-acridin-9-yl-3-methylthiourea Au(I) DNA intercalators [Au(ACRTU)2]Cl (2) and [Au(ACRTU) (PPh3)]PF6 (3) have been prepared. Both complexes were highly active in the human ovarian carcinoma cisplatin-sensitive A2780 cell line, exhibiting IC50 values in the submicromolar range. Compounds 2 and 3 are also cytotoxic toward different phenotypes of breast cancer cell lines MDA-MB-231 (triple negative), SK-BR-3 (HER2+, ERα-, and ERβ-), and MCF-7 (ER+). Both complexes induce apoptosis through activation of caspase-3 in vitro. While inhibition of some proteins (thiol-containing enzymes) seems to be the main mechanism of action for cytotoxic gold complexes, 2 and 3 present a DNA-dependent mechanism of action. They locate in the cell nucleus according to confocal microscopy and transmission electronic microscopy. The binding to DNA resulted to be via intercalation as shown by spectroscopic methods and viscometry, exhibiting a dose-dependent response on topoisomerase I mediated DNA unwinding. In addition, 2 and 3 exhibit potent antiangiogenic effects and are also able to inhibit vasculogenic mimicry of highly invasive MDA-MB-231 cells.

Exploring the Influence of the Aromaticity on the Anticancer and Antivascular Activities of Organoplatinum(II) Complexes

A series of new organometallic PtII complexes of the type [Pt(C^N)Cl(DMSO)] (C^N=N,N-dimethyl-1-(2-aryl)methanamine-κ2 C2,N; aryl=phenyl 2 a, biphenyl 2 b, p-terphenyl 2 c, naphthyl 2 d, anthracenyl 2 e, or pyrenyl 2 f) have been synthesized to explore the influence of the aromaticity on their anticancer activity. The best performers, 2 b and d, are more active than cisplatin (CDDP) in epithelial ovarian carcinoma cells A2780, with 2 d having a higher selectivity factor than CDDP in all the tested cell lines. In addition, all the new compounds overcome the acquired resistance in A2780cisR cells and interestingly, show low micromolar IC50 values towards the triple negative breast cancer cell line MDA-MB-231 and the highly metastatic 518A2 melanoma cells. This study shows that the hydrophobicity, accumulation into cells, and metal levels on nuclear DNA for the complexes are consistent with their cytotoxicity. Complexes 2 b and d induce apoptosis in a caspase-independent manner and suppress the intracellular ROS generation without modifying the mitochondria membrane potential. In addition, 2 a-f effectively inhibit angiogenesis in the endothelial cell line EA.hy926 at sub-cytotoxic concentrations and 2 b and d show in vivo antivascular effects on the chorioallantoic membrane (CAM) of fertilized SPF-eggs (SPF=specific-pathogen-free). Inhibition of tubulin polymerization and degeneration of cytoskeleton organization in 518A2 melanoma cells are presented as a preliminary mechanism of its antimetastatic activity.

Understanding the interaction of an antitumoral platinum(II) 7-azaindolate complex with proteins and DNA

AbstractThe reactivity of the [Pt(dmba)(aza-N1)(dmso)] complex 1, (a potential antitumoral drug with lower IC50 than cisplatin in several tumoral cell lines) with different proteins and oligonucleotides is investigated by means of mass spectrometry (ESI-TOF MS). The results obtained show a particular binding behaviour of this platinum(II) complex. The interaction of 1 with the assayed proteins apparently takes place by Pt-binding to the most accessible coordinating amino acids, presumably at the surface of the protein -this avoiding protein denaturation or degradation- with the subsequent release of one or two ligands of 1. The specific reactivity of 1 with distinct proteins allows to conclude that the substituted initial ligand (dmso or azaindolate) is indicative of the nature of the protein donor atom finally bound to the platinum(II) centre, i.e. N- or S-donor amino acid. Molecular modeling calculations suggest that the release of the azaindolate ligand is promoted by a proton transfer to the non-coordinating N present in the azaindolate ring, while the release of the dmso ligand is mainly favoured by the binding of a deprotonated Cys. The interaction of complex 1 with DNA takes always place through the release of the azaindolate ligand. Interestingly, the interaction of 1 with DNA only proceeds when the oligonucleotides are annealed forming a double strand. Complex 1 is also capable to displace ethidium bromide from DNA and it also weakly binds to DNA at the minor groove, as shown by Hoechst 33258 displacement experiments. Furthermore, complex 1 is also a good inhibitor of cathepsin B (an enzyme implicated in a number of cancer related events). Therefore, although compound 1 is definitely able to bind proteins that can hamper its arrival to the nuclear target, it should be taken into consideration as a putative anticancer drug due to its strong interaction with oligonucleotides and its effective inhibition of cat B. Graphical AbstractReactivity of a Pt complex: The interaction of a potential antitumoral drug, [Pt(dmba)(aza-N1)(dmso)], with distinct proteins and oligonucleotides has been studied by means of ESI-TOF MS. The particular reactivity of this complex in front of the assayed biomolecules required the use of spectroscopic techniques and theoretical calculations to elucidate its mechanism. This information will contribute to its consideration as a putative anticancer drug.

Toward angiogenesis inhibitors based on the conjugation of organometallic platinum(II) complexes to RGD peptides

A novel conjugate between a cyclometalated platinum(II) complex with dual antiangiogenic and antitumor activity and a cyclic peptide containing the RGD sequence (‐Arg‐Gly‐Asp‐) has been synthesized by combining solid‐ and solution‐phase methodologies. Although peptide conjugation rendered a non‐cytotoxic compound in all tested tumor cell lines (± αVβ3 and αVβ5 integrin receptors), the antiangiogenic activity of the Pt‐c(RGDfK) conjugate in human umbilical vein endothelial cells at sub‐cytotoxic concentrations opens the way to the design of a novel class of angiogenesis inhibitors through conjugation of metallodrugs with high antiangiogenic activity to cyclic RGD‐containing peptides or peptidomimetic analogues.