Trans-platinum Compounds Research Articles

Interactions between anticancer trans-platinum compounds and proteins: crystal structures and ESI-MS spectra of two protein adducts of trans-(dimethylamino)(methylamino)dichloridoplatinum(II).

The adducts formed between trans-(dimethylamino)(methylamino)dichloridoplatinum(II), [t-PtCl2(dma)(ma)], and two model proteins, i.e., hen egg white lysozyme and bovine pancreatic ribonuclease, were independently characterized by X-ray crystallography and electrospray ionization mass spectrometry. In these adducts, the Pt(II) center, upon chloride release, coordinates either to histidine or aspartic acid residues while both alkylamino ligands remain bound to the metal. Comparison with the cisplatin derivatives of the same proteins highlights for [t-PtCl2(dma)(ma)] a kind of biomolecular metalation remarkably different from that of cisplatin.

Recent Advances in Multinuclear Complexes as Potential Anticancer and DNA Binding Agents

In the search for new metal-based anticancer agents as effective candidates for cisplatin, a lot of strategies such as synthesis of cisplatin analogs, trans-platinum compounds and non-platinum metal complexes have been put forward in the last forty years. The concept of multinuclearity for improving the chemotherapeutic activity has been proven in multinuclear platinum complexes such as BBR3464, recently, the effective approach has been successfully transferred to ruthenium complexes. In this review, we highlighted the recent progress in multinuclear platinum complexes and ruthenium complexes as anticancer agents, and their novel DNA binding properties such as phosphate clamps, long range DNA cross links, bisintercalation, interduplex cross links and DNA-protein cross-links were summarized to shed light on the rational design of polynuclear complexes as anticancer agents.

Carboplatin and oxaliplatin in sequenced combination with bortezomib in ovarian tumour models

BackgroundOvarian cancer remains an on-going challenge mainly due to the development of drug resistance and also because the cancer is likely to have metastasized at the time of diagnosis. Currently, chemotherapy based on platinum drugs such as cisplatin is the primary treatment for the disease. Copper transporter 1 is involved in the transport of cisplatin into the cell, but is also down-regulated by the drug. Bortezomib, a proteasome inhibitor, has been reported to block this platinum-induced down-regulation of CTR1, so that in the presence of bortezomib, the cellular uptake of platinum drugs may be increased. Increased platinum accumulation may result in increased platinum − DNA binding so that the platinum drug in combination with bortezomib may produce enhanced cell kill.MethodsIn this study the efficacy of the sequential combinations of carboplatin, oxaliplatin and a trans-platinum compound coded as CH1 with BORT on the human ovarian A2780, A2780cisR, A2780ZD0473R and SKOV-3 cancer cell lines was evaluated. The levels of cellular platinum accumulation and platinum-DNA binding were determined following the treatment with these combinations. In order to investigate the effect of the combinations of the formation of ROS, the total and oxidized glutathione levels were also determined.ResultsPrevention of copper transporter 1 degradation by bortezomib is found to enhance the cellular accumulation of platinum, the level of Platinum − DNA binding and increases oxidative stress especially in the resistant cell lines.ConclusionsThe results suggest that the prevention of CTR1 degradation by bortezomib may be playing a major role in increasing the cellular uptake of platinum drugs and platinum-DNA binding level. Furthermore, the generation of oxidative stress appears to be a major contributor to the enhanced cell kill.

Effect of PARP inhibitors on sensitivity of lung and breast cancer cells to trans-platinum as compared to cis-platinum.

e22115 Background: Poly(ADP-ribose) polymerase inhibitors (PARP-i) represent promising strategy in treatment of cisplatin resistant lung cancer and triple-negative breast cancer. We compared PARP inhibition by 3-aminobenzamide (3-AB) or NU1025, on activity of cis- and trans-platinum on NSCLC cells (A549) and breast cancer cells (MDA-MB-361), and correlated with p53 and ERCC1 status. Methods: Cell cycle distribution was determined by FACS-flow and PI-staining, while morphological changes were followed by light microscopy. ERCC1 siRNA transfection was performed by HiperFect reagent, and mRNA was analyzed by qRT-PCR. Protein expression levels were determined by Western blot. PARP-inhibition was quantified as NAD(P)H depletion using colorimetric XTT assay. Results: Trans-platinum compound with planar ammine ligands, trans-[PtCl2(4-acetylpyridine)2] showed cytotoxic activity comparable to cis-platin and exhibited enhanced action in combination with PARP-i. 3-AB enhanced the activity of trans more efficient comparing to cis-platinum in MDA-MB-361 cells. At equitoxic concentrations corresponding to IC50 values in A549 cells, cis-platin and trans-platinum compound differently affected cell survival in combination with PARP-i. XTT assay confirmed efficient inhibition of PARP activity at 200 μM NU1025 and 2 mM 3-AB in both cell lines. ERCC1 silencing in p53 proficient A549 cells, alone or in combination with NU1025, almost completely diminished resistance to trans-[PtCl2(4-acetylpyridine)2], decreasing cell survival to 50 % following 24 h action and more than 85 % following 48 h treatment, comparing to siRNA/NU1025 treated control. By contrast, sensitivity to cisplatin was much less altered. Simultaneous alteration of ERCC1 and PARP itself did not affect cell cycle progression, but prolonged sub-G1 fraction by trans-platinum as well as G2-M fraction by cis-platin. Conclusions: PARP-inhibition enhanced tumor cell sensitivity to trans-platinum drug, stronger than cis-platinum. Knockdown of ERCC1 further increases sensitivity to platinum drugs, irrelevant to p53 status. Trans-platinum complexes should be further explored as good candidates for combining with PARP-i.

Retained platinum uptake and indifference to p53 status make novel transplatinum agents active in platinum-resistant cells compared to cisplatin and oxaliplatin

Despite the clinical success of platinum-containing drugs in the treatment of solid tumors, acquired resistance remains a major obstacle. We previously identified a group of novel transplanaramine or transplatinum compounds based on distinct activity profiles in the NCI-60 panel. In the present study, parental KB-3.1 cells with wild-type p53 and its cisplatin- and oxaliplatin-resistant sublines harboring mutant p53 proteins were used to contrast several transplatinum compounds with cisplatin and oxaliplatin. The transplatinum compounds retained cytotoxic activity in the resistant cell lines. While intracellular accumulation and DNA platination of cisplatin and oxaliplatin was decreased in the resistant cells, the transplatinum compounds both accumulated intracellularly and platinated DNA at comparable levels in all cell lines. Cytoflow analysis confirmed that cisplatin and oxaliplatin alter the cell cycle distribution and result in apoptosis; however, at comparably toxic concentrations, the transplatinum compounds did not alter the cell cycle distribution. Analysis of the cytoplasmic fraction treated with acetone showed that cisplatin and oxaliplatin readily bound to macromolecules in the pellet, whereas a larger percentage of the transplatinum compounds remained in the supernatant. We concluded that, distinct from platinum compounds currently in use, transplatinum compounds accumulate intracellularly in resistant cells at levels comparable to those in drug-sensitive cells, do not affect the cell cycle and thus retain cytotoxicity independent of p53 status and likely have cytoplasmic targets that are important in their activity.

Preparation and characterization of a new trans-platinum glycocholate complex

The synthesis and characterization of a new water-soluble cytotoxic transplatinum compound are described. The new compounds, trans-[PtII(GC)2(NH3)2], is a transplatinum derivative containing an N2O2 donor set, using glycocholate (GC, a bile acid) ligands. The new compound has been characterized by infrared and NMR spectroscopies, as well as mass spectrometry. The FTIR spectra show a separation between νCOOas and νCOOs stretching bands in agreement with a monodentate binding mode of carboxylate group attached to platinum. The new compound is compared with cis-[PtIICl(GC)(NH3)2] in their cytotoxic properties against three cell lines (HELA229, A2780 and A2780cisR). Both compounds showed a poor inhibition on the growth of these cell lines in comparison with cis-platin (cis-DDP). Bile acids are involved in the enterohepatic cycle. This cycle can be useful for directing vectorially certain drugs for the treatment of diseases of the organs linked to this cycle. The next step of cytotoxicity assays will be performed in our laboratory, using cell lines related to these organs.

The role of p53 in the cellular toxicity by active trans-platinum complexes containing isopropylamine and hydroxymethylpyridine

Despite some initial research that reported a lack of activity of trans geometry, complexes with general formula trans-[PtCl 2(L)(L′)] exhibit an important cytotoxic activity in cisplatin-sensitive and resistant cell lines. Based on the proposed mechanism of action for the trans-platinum compounds, they might form DNA adducts initiating a DNA-damage response and ultimately ending in the activation of the p53 protein. In the present work, we have studied the biochemical properties of the trans-[PtCl 2(isopropylamine)(L)] complexes (where L is 3- or 4-(hydroxymethyl)-pyridine) against several cell lines and the relationship between cytotoxicity and the protein p53. Both complexes showed different antitumoral properties depending on the presence or absence of protein p53 in isogenic colon carcinoma HCT116 cell lines. Cell cycle studies with the complexes in these cell lines were performed to investigate their antitumoral activity. Apoptosis was observed to be launched from G1 or G2/M accumulations. Confocal microscopy showed the different behaviour of isogenic tumoral cell lines treated with the trans-platinum complexes. Our data suggest that small differences in the carrier ligands could play an important role in the overall biological effects. The body of the research regarding structure–activity relationships such as the different position of groups in the carrier ligands will provide new rational basis for the design of new platinum antitumor drugs.

Density Functional Theory Characterization and Descriptive Analysis of Cisplatin and Related Compounds

Quantum and nonquantum descriptors clearly related to physicochemical features and predictors of the trends to evolve along different stages of a known mechanism of action were determined for a set of square-planar compounds of general formula [M(II)A(1)A(2)L(1)L(2)] (M(II) = Pt(II)/Pd(II); A(i)/L(i) = carrier/labile ligands), structurally related to the anticancer agent Cisplatin. Selected compounds have been sorted and classified by Ward's Cluster Analysis and Principal Components Analysis data-mining techniques using seventeen 1D and two 3D of such theoretical descriptors calculated at the DFT level (PCM-B3LYP/LANL2DZ/6-31G*). A rationale emerging from the study is that whereas most significant differences come from substitution of Cisplatin ligands, cis/trans isomerism, and exchange of M(II) introduce minor alterations in the electronic/geometrical structure. This provides theoretical support to the assay of transplatinum compounds as potential anticancer drugs, a fact already pointed out by empirical evidence. Similarly, the little geometrical/electronic differences triggered by switching M(II) from Pt to Pd enable us to devise a rational path to propose new compounds with expected good anticancer profiles, tuning alterations introduced by simultaneously changing both metal and ligands. Current results serve thus to enlarge the Cleare-Hoeschele guides for Pt(II) square-planar anticancer potential drugs to Pd(II) compounds, both using cis/trans scaffolds.

Towards Antitumor Active trans‐Platinum Compounds

Substitution of NH(3) by a range of amines in trans-[PtCl(2)(NH(3))(2)] produces compounds with cytotoxicity significantly improved over the parent transplatin and in many cases equivalent to that of cisplatin. This microreview summarizes the chemistry and biology of trans-platinum compounds containing principally planar amines and succinctly reviews the current status of anticancer relevance of the trans-platinum geometry. The nature of bifunctional DNA adducts (intrastrand, interstrand) is remarkably dependent on the nature of the amine. Further, the stability of monofunctional adducts allows for competitive production of DNA-protein crosslinks and overall the results suggest that the trans-platinum chemotype may offer significant potential for design of selective DNA-protein crosslinking agents. A subset of proteins known to bind to DNA modified by trans-platinum is that comprised of zinc fingers - model studies show the potential for formation of heteronuclear thiolate-bridged species as precedent for zinc displacement from the biomolecule.

Metallothioneins and Platinum(II) Anti-Tumor Compounds

The classical square planar transition metal complex cis-diamminodichlorido platinum(II) (cisplatin) ranks among the most successful and widely applied antitumor drugs for the treatment of a number of cancers. However, the risk of unforeseen resistance formation and the appearance of severe side effects in cancer patients constitutes a considerable need for the development of novel platinum based antitumor compounds. Since the introduction of cisplatin into the clinic, a few similar compounds, like cis-diammine(1,1-cyclobutanedicarboxylato)platinum(II) (carboplatin), were developed, which can partly overcome the problems. The ubiquitously occurring small zinc and copper binding proteins metallothioneins (MTs) constitute the most potent cytosolic sink for platinum drugs. It appeared that, besides the formation of the very strong platinum(II)-sulfur bond involving the twenty cysteine residues of MT, the incorporation of platinum(II) into the MT structure contributes effectively to the scavenging of the drug. However, recently it became evident that the extent, to which MT sequesters platinum drugs, depends not only on the type of cancer, but also on the interaction of MT with the ligand sphere of the platinum center. For example, in contrast to cis-platinum(II) compounds, trans-platinum(II) compounds retain their N-donor ligands upon reaction with MT. From these studies, guidelines may be derived for the development of N-donor carrier ligands leading to novel platinum(II) drugs. This review describes the role of metallothioneins for the platinum(II) drug sequestration in vivo. Furthermore, it summarizes the recent developments toward the understanding of the reaction between platinum(II) and MT thiols and the structural aspects of the platinum(II) incorporation into the MT domains, and comments about future perspectives are given.

Cytotoxicity, mutagenicity, cellular uptake, DNA and glutathione interactions of lipophilic trans-platinum complexes tethered to 1-adamantylamine

Cytotoxicity and mutagenicity of trans,trans,trans-[PtCl2(CH3COO)2(NH3)(1-adamantylamine)] [trans-adamplatin(IV)] and its reduced analog trans-[PtCl2(NH3)(1-adamantylamine)] [trans-adamplatin(II)] were examined. In addition, the several factors underlying biological effects of these trans-platinum compounds using various biochemical methods were investigated. A notable feature of the growth inhibition studies was the remarkable circumvention of both acquired and intrinsic cisplatin resistance by the two lipophilic trans-compounds. Interestingly, trans-adamplatin(IV) was considerably less mutagenic than cisplatin. Consistent with the lipophilic character of trans-adamplatin complexes, their total accumulation in A2780 cells was considerably greater than that of cisplatin. The results also demonstrate that trans-adamplatin(II) exhibits DNA binding mode markedly different from that of ineffective transplatin. In addition, the reduced deactivation of trans-adamplatin(II) by glutathione seems to be an important determinant of the cytotoxic effects of the complexes tested in the present work. The factors associated with cytotoxic and mutagenic effects of trans-adamplatin complexes in tumor cell lines examined in the present work are likely to play a significant role in the overall antitumor activity of these complexes.

Trans-platinum(II) complexes with cyclohexylamine as expectator ligand induce necrosis in tumour cells by inhibiting DNA synthesis and RNA transcription

Enhanced removal of cisplatin-DNA adducts has been reported as one of main causes of cell resistance to cisplatin. This particular resistance mechanism may be circumvented by platinum complexes that bind differently to DNA. One line of work is focussed on trans platinum complexes, some of which exhibit antitumour activity similar to or even higher than that of their cis counterparts. We synthesised new trans platinum complexes, trans-[PtCl2(cyclohexylamine)(dimethylamine)] and trans-[PtCl2(OH)2(cyclohexylamine)(dimethylamine)], previously evaluated as cytotoxic agents towards different cancer and normal cell lines. These trans platinum compounds were highly effective against a panel of tumoral cell lines either sensitive to or with acquired resistance to cisplatin. In the present work we examined the mechanisms induced by these compounds to cause tumour cells toxicity. We have found that these compounds induced a complete blockade at the S phase of the cell cycle inhibiting total mRNA transcription and precluding p53 activation. In contrast to other DNA-damaging agents, these compounds do not induce senescence-associated permanent arrest. Furthermore, only a small percentage of these cells enter into apoptosis, with most of the population dying by a necrosis-like mechanism.

Promotion of DNA strand breaks, interstrand cross-links and apoptotic cell death in A2780 human ovarian cancer cells by transplatinum planar amine complexes

Cisplatin is one of the primary drugs utilized in the treatment of ovarian cancer. However, despite the initial effectiveness of chemotherapy in suppressing this disease, drug resistance almost invariably develops and cures are relatively rare. While it is generally thought that only compounds of the cis geometry express antitumor activity, a number of transplatinum derivates have shown preclinical promise. The current work investigates the influence of transplanaramine (TPA) compounds of structure trans-[Pt (O 2CR) 2 (L) (L′)], (L = NH 3, L′ = pyridine, quinoline, isoquinoline; L = L′ = pyridine; R = H, CH 3, CH 2OH, etc.) (with a focus on the contribution of the carboxylate leaving group to drug action) on growth and viability of A2780 human ovarian carcinoma cells as well as their putative mechanism(s) of cytotoxicity. The compounds, as a class, induce cell death through caspase-dependent apoptosis, with activation of both caspase 3 and caspase 9 and concomitant PARP cleavage. The trans-platinum compounds tested show induction of p53 as well as time dependent γH2AX induction, consistent with the promotion of DNA lesions. trans-[Pt(O 2CH) 2(NH 3)(4-pic)] can be shown to promote significant DNA strand breaks and DNA interstrand cross-linking. The enhanced cytotoxicity of trans-[Pt(O 2CH) 2(NH 3)(4-pic)] compared to its isostructural –O 2CCH 3 and –O 2CCH 2OH analogs may be a consequence of its accelerated cellular accumulation, increased hydrolytic activation, interstrand cross-linking and abortive efforts by the cell to repair the cross linked DNA.

Trans-Platinum Complexes in Cancer Therapy

The research of new platinum drugs active towards cisplatin refractory/resistant tumors has been mostly focussed on compounds with cis geometry because transplatin, the trans-isomer of cisplatin, is inactive. It is widely accepted that transplatin inactivity stems from two major factors: i) the kinetic instability promoting its deactivation and ii) the formation of DNA adducts characterized by a regioselectivity and a stereochemistry different from those of cisplatin. However, several exceptions to the general rule that the presence of two leaving groups in cis positions is necessary for antitumor activity of platinum complexes, have been reported. Substitution of transplatin ammine ligands by aromatic N-donor heterocycles, branched aliphatic amines, or imino ligands has lead to compounds with relevant in vitro tumor cell growth inhibitory potency, often active towards cisplatin refractory/resistant tumor cells, and in some cases endowed with significant activity also in vivo. From a mechanistic point of view, substitution of bulky ligands for ammines can retard substitution of the two chloride ligands, thus reducing the kinetic instability of the trans-platinum compounds. On the other hand, the formation of DNA adducts qualitatively and quantitatively different from those of cisplatin strongly supports the hypothesis that antitumor-active trans-platinum complexes can have a different spectrum of activity. It is hoped that the increasing knowledge of the biochemical and cellular processes underlying the antitumor-activity of trans-platinum complexes will foster their clinical development.

Recognition of DNA modified by trans‐[PtCl2NH3(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.

Trans-Platinum Complexes with Promising Antitumor Properties

Wide range of dose-limiting toxicities and tumor resistance to drug are significant limitations of the successful use of cis-diamminedichloroplatinum (cisplatin). For a long time it was believed that generally trans-isomers of platinum containing complexes are devoid of biological activity. Data accumulated by the structure-activity relationship studies up to date, confirm that trans-platinum(II) and trans-platinum(IV) complexes often exhibit enhanced activity in cisplatin resistant cell lines in comparison to their cis-analogs, indicating that trans-platinum compounds follow some different pattern of antitumor activity in comparison to their cis-isomers. Trans-platinum complexes that have been tested to date and have shown to possess attractive antitumor properties represent diverse group of compounds, and can be classified according to the structure and the nature of nonleaving (amine) ligand as following: trans-ammine(amine) platinum(IV) complexes, trans-platinum(II) complexes with planar ligands, trans-platinum(II) complexes with heterocyclic amine ligands, trans-platinum(II) complexes with iminoether ligands, trans-platinum(II) complexes with asymmetric aliphatic amine ligands, bifunctional binuclear and trinuclear trans-platinum(II) complexes. Potential of trans-platinum complexes to follow some different mechanisms of cell killing in comparison to cis-DDP and thus circumvent cis-DDP resistance, raises interest for their further preclinical evaluation. Keywords: trans-platinum, anticancer drugs, cytotoxicity

Enhancement of Aqueous Solubility and Stability Employing a Trans Acetate Axis in Trans Planar Amine Platinum Compounds while Maintaining the Biological Profile

A general approach to solubilization and possible in vivo activation of the transplatinum geometry is presented. The synthesis and characterization of new water-soluble cytotoxic transplatinum compounds are described. Use of acetate ligands (and carboxylate ligands in general) in trans-[Pt(OAc)(2)(L)(L')] results in significantly enhanced aqueous solubility and chemical stability in comparison to the parent dichlorides. The new compounds are the first cytotoxic transplatinum compounds containing an N(2)O(2) donor set, similar to carboplatin and oxaliplatin.

Cytotoxicity, DNA strand breakage and DNA–protein crosslinking by a novel transplatinum compound in human A2780 ovarian and MCF-7 breast carcinoma cells

Cisplatin, cis-[PtCl 2(NH 3) 2], is commonly utilized in various combination chemotherapy protocols for the treatment of both ovarian and breast cancer while the corresponding trans isomer is therapeutically inactive. This work describes efforts to elucidate the cellular mechanism of action of a novel trans-platinum compound, trans-(dichloroamminethiazole)platinum(II) (ATZ), which demonstrates antiproliferative and cytotoxic effects against both MCF-7 human breast and A2780 human ovarian carcinoma cells in culture. A2780 cells were approximately twofold more sensitive to ATZ than MCF-7 cells in both cell growth and clonogenic survival assays. Dye exclusion studies revealed a 50–70% loss in cell viability within the first 12 h of drug treatment in both cell lines. This initial wave of cell death was succeeded by a prolonged interval of growth arrest during which a small fraction of apoptotic cells was detected. Binding of ATZ to DNA, as estimated by atomic absorption spectroscopy, was similar for the two cell lines and was almost completely reversed 24 h after drug removal. ATZ also induced DNA strand breakage as well as DNA–protein crosslinking during the initial 12 h period when the bulk of cell death was evident. However, neither the extent of DNA strand breakage nor that of DNA protein crosslinking was sufficient to explain the different drug sensitivity in the two cell lines. At 24 and 48 h after exposure of MCF-7 cells to high concentrations of ATZ, the formation of DNA-topoisomerase I complexes is detected, coincident with a high degree of apoptosis. These studies suggest that ATZ has the capacity to interfere with topoisomerase I in the tumor cell, a function not evident in cis-platinum-based drugs.

Might telomerase enzyme be a possible target for trans-Pt(II) complexes?

Telomerase is a ribonucleoprotein polymerase that synthesizes telomeric DNA (TTAGGG) repeats. Previously, we have studied the effect on telomerase enzyme of several cis-platinum(II) complexes bearing aromatic amines as bulky carrier groups. All these complexes possess cis-geometry, according to the Cleare and Hoschele’s rule. Since recent reports have dealt with the anti-cancer activity of trans-platinum compounds, in this study we have investigated the Farrell’s prototypical trans-[Pt(Cl)2(pyridine)2], hereafter called trans-PtPy, in order to understand whether it may possess any anti-telomerase activity. The trans-PtPy has low water solubility and requires dimethyl sulfoxide (DMSO) as co-solvent, thus making the biological tests problematic. The effect of trans-PtPy on MCF-7 cell line concerning log-term telomerase inhibition, telomerase-related gene expression, viability, and apoptosis was evaluated. In a cell-free biochemical assay, trans-PtPy showed significant and dose-dependent inhibition of semi-purified telomerase. The bulk of data indicate that trans-PtPy acts as a non-properly selective anti-proliferative agent, although it shows an initial telomerase inhibitory effect. Telomere length reduction seems not to be the main mechanism causing the observed cell apoptosis. For comparison purpose, results on cis-[Pt(Cl)2(pyridine)2], hereafter cis-PtPy, are reported.

Preparation, characterization and cytotoxic activity of new compounds trans-[PtCl 2NH 3(3-(hydroxymethyl)-pyridine)] and trans-[PtCl 2NH 3(4-(hydroxymethyl)-pyridine)

We report the synthesis, characterization and cytotoxic assays of new trans-platinum compounds, trans-[PtCl 2NH 3(3-(hydroxymethyl)-pyridine)] and trans-[PtCl 2NH 3(4-(hydroxymethyl)-pyridine)]. In the present work, we found that the replacement of the ammine ligand in “classical” transplatinum with the two new ligands does not increase the cytotoxic activity, maybe because these complexes do not produce a stability of the intrastrand cross-links in DNA.