The signalling axis mediating neuronal apoptosis in response to [Pt(O,O′-acac)(γ-acac)(DMS)]

Synthesis and Investigations of the Antitumor Effects of First-Row Transition Metal(II) Complexes Supported by Two Fluorinated and Non-Fluorinated β-Diketonates

The 3d transition metal (Mn(II), Fe(II), Co(II), Ni(II), Cu(II) and Zn(II)) complexes, supported by anions of sterically demanding β-diketones, 1,3-dimesitylpropane-1,3-dione (HLMes) and 1,3-bis(3,5-bis(trifluoromethyl)phenyl)-3-hydroxyprop-2-en-1-one (HLCF3), were synthesized and evaluated for their antitumor activity. To assess the biological effects of substituents on phenyl moieties, we also synthesized and investigated the analogous metal(II) complexes of the anion of the less bulky 1,3-diphenylpropane-1,3-dione (HLPh) ligand. The compounds [Cu(LCF3)2], [Cu(LMes)2] and ([Zn(LMes)2]) were characterized by X-ray crystallography. The [Cu(LCF3)2] crystallizes with an apical molecule of solvent (THF) and features a rare square pyramidal geometry at the Cu(II) center. The copper(II) and zinc(II) complexes of diketonate ligands, derived from the deprotonated 1,3-dimesitylpropane-1,3-dione (HLMes), adopt a square planar or a tetrahedral geometry at the metal, respectively. We evaluated the antitumor properties of the newly synthesized (Mn(II), Fe(II), Co(II), Ni(II), Cu(II) and Zn(II)) complexes against a series of human tumor cell lines derived from different solid tumors. Except for iron derivatives, cellular studies revealed noteworthy antitumor properties, even towards cancer cells endowed with poor sensitivity to the reference drug cisplatin.

Synthesis and cytotoxicity studies of Cu(I) and Ag(I) complexes based on sterically hindered β-diketonates with different degrees of fluorination

Design, synthesis, and in vitro antitumor properties of Cu(I) and Ag(I) phosphane complexes supported by the anions of sterically hindered β-diketone ligands, 1,3-dimesitylpropane-1,3-dione (HLMes) and 1,3-bis(3,5-bis(trifluoromethyl)phenyl)-3-hydroxyprop-2-en-1-one (HLCF3) featuring trifluoromethyl or methyl groups on the phenyl moieties have been reported. In order to compare the biological effects of substituents on the phenyl moieties, the analogous copper(I) and silver(I) complexes of the anion of the parent 1,3-diphenylpropane-1,3-dione (HLPh) ligand were also synthesized and included in the study. In the syntheses of the Cu(I) and Ag(I) complexes, the phosphane coligands triphenylphosphine (PPh3) and 1,3,5-triaza-7-phosphaadamantane (PTA) were used to stabilize silver and copper in the +1 oxidation state, preventing the metal ion reduction to Ag(0) or oxidation to Cu(II), respectively. X-ray crystal structures of HLCF3 and the metal adducts [Cu(LCF3)(PPh3)2] and [Ag(LPh)(PPh3)2] are also presented. The antitumor properties of both classes of metal complexes were evaluated against a series of human tumor cell lines derived from different solid tumors, by means of both 2D and 3D cell viability studies. They display noteworthy antitumor properties and are more potent than cisplatin in inhibiting cancer cell growth.

Antitumor and antimigration effects of a new Pt compound on neuroblastoma cells

Among the new Pt complexes with anticancer properties, phenanthroline derivatives have aroused great interest due to their different mode of action compared to cisplatin. We previously examined cytotoxic effects of a new Pt(II)-complex containing 1,10-phenantroline (phen), [Pt(η¹-C₂H₄OMe)(DMSO)(phen)]Cl, in a panel of eight human cancer cell lines, and showed that it exerted the greatest cytotoxic effect in the neuroblastoma SH-SY5Y cell line. In this study, the antiproliferative and antimetastatic potential of [Pt(η¹-C₂H₄OMe)(DMSO)(phen)]⁺ (in short Pt-EtOMeSOphen) was investigated in neuroblastoma SH-SY5Y, SK-N-SH and SK-N-BE(2) cells. Pt-EtOMeSOphen provoked the early signs of apoptosis induction (cleavage of PARP and activation of caspases-9 and -7); it also increased the level of proapoptotic Bax protein whereas it decreased the level of the antiapoptotic Bcl-2 protein. The effects of Pt-EtOMeSOphen on migration and invasion processes were also evaluated. A decrease of cell migration/invasion by Pt-EtOMeSOphen was observed through 2D and 3D in vitro assays. Pt-EtOMeSOphen was found to exert its actions by decreasing MMP-9 and MMP-2 expressions and activities. Pt-EtOMeSOphen provoked the phosphorylation of both ERK1/2 and p38 MAPKs. All the effects of Pt-EtOMeSOphen on SH-SY5Y cell vitality, migration and metalloproteases activities described here were due to the activation of p38 MAPK since pharmacological p38 MAPK inhibition or small interfering RNAs to p38 MAPK mRNA blocked such effects. Results suggest that Pt-EtOMeSOphen inhibits neuroblastoma cancer cells survival, motility, and invasion. This could lead to the reduction of neuroblastoma metastatic potential.

Role of epidermal growth factor receptor signaling in a Pt(II)-resistant human breast cancer cell line

Platinum complexes are currently used for breast cancer therapy, but, as with other drug classes, a series of intrinsic and acquired resistance mechanisms hinder their efficacy. To better understand the mechanisms underlying platinum complexes resistance in breast cancer, we generated a [Pt(O,O'-acac)(γ-acac)(DMS)]-resistant MCF-7, denoted as [Pt(acac)₂]R. [Pt(O,O'-acac)(γ-acac)(DMS)] was chosen as previous works showed that it has distinct mechanisms of action from cisplatin, especially with regard to cellular targets. [Pt(acac)₂]R cells are characterized by increased proliferation rates and aggressiveness with higher PKC-δ, BCL-2, MMP-9 and EGFR protein expressions and also by increased expression of various genes covering cell cycle regulation, invasion, survival, and hormone receptors. These [Pt(acac)₂]R cells also displayed high levels of activated signaling kinases Src, AKT and ERK/2. [Pt(acac)₂]R cells incubated with [Pt(O,O'-acac)(γ-acac)(DMS)], showed a relevant EGFR activation due to PKC-δ and Src phosphorylation that provoked proliferation and survival through MERK1/2/ERK1/2 and PI3K/Akt pathways. In addition, EGFR shuttled from the plasma membrane to the nucleus maybe acting as co-transcriptional factor. The data suggest that growth and survival of resistant cells rely upon a remarkable increase in EGFR level which, in collaboration with an enhanced role of PKC-δ and Src kinases support [Pt(acac)₂]R cell. It could therefore be assumed that combination treatments targeting both EGFR and PKC-δ/Src can improve therapy for breast cancer patients.

Bradykinin stimulates prostaglandin E2 release in human skeletal muscular fibroblasts

Local mediator prostaglandins and bradykinin are involved in inflammation and pain. We explored bradykinin effects on prostaglandin E2 (PGE2) release from fibroblasts derived from human skeletal muscular biopsies. Bradykinin induced PGE₂ release through bradykinin B2 receptors, since PGE₂ release was blocked by the bradykinin B2 receptor selective antagonist FR173657 and B2 receptor agonist (Hyp³)-bradykinin showed effects comparable to bradykinin. Consistently, bradykinin induced both mRNA cyclooxygenase 2 (COX-2) and protein. Bradykinin also induced ERK1/2 and p38 phosphorylation and provoked the translocation from the cytosol to the nucleus of p65/NF-kB. The release of PGE₂ by bradykinin could be blocked inhibiting COX-2 and p65/NF-kB, ERK1/2 or p38 activation. Both ERK1/2 and p38 were upstream to NF-kB inasmuch siRNAs significantly blocked the p65/NF-kB activation induced by bradykinin. Thus, bradykinin, acting via B2 receptors, induced PGE₂ release through ERK1/2 and p38-dependent pathways and consequent p65/NF-kB translocation to nucleus. p65/NF-kB induced COX-2 transcription. The release of PGE₂ provide a possible explanation for the role of bradykinin in inflammatory diseases.

TGF-β1 activates RSC96 Schwann cells migration and invasion through MMP-2 and MMP-9 activities

Following peripheral nerve injury, remnant Schwann cells adopt a migratory phenotype and remodel the extracellular matrix allowing axonal regrowth. Although much evidence has demonstrated that TGF-β1 promotes glioma cell motility and induces the expression of extracellular matrix proteins, the effects of TGF-β1 on Schwann cell migration has not yet been studied. We therefore investigated the cellular effects and the signal transduction pathways evoked by TGF-β1 in rattus norvegicus neuronal Schwann RSC96 cell. TGF-β1 significantly increased migration and invasion of Schwann cells assessed by the wound-healing assay and by cell invasion assay. TGF-β1-enhanced migration/invasion was blocked by inhibition of MMP-2 and MMP-9. Consistently, by real-time and western blot analyses, we demonstrated that TGF-β1 increased MMP-2 and MMP-9 mRNA and protein levels. TGF-β1 also increased MMPs activities in cell growth medium, as shown by gelatin zymography. The selective TGF-β Type I receptor inhibitor SB431542 completely abrogated any effects by TGF-β1. Indeed, TGF-β1 Type I receptor activation provoked the cytosol-to-nucleus translocation of SMAD2 and SMAD3. SMAD2 knockdown by siRNA blocked MMP-2 induction and cell migration/invasion due to TGF-β1. TGF-β1 also provoked phosphorylation of MAPKs extracellular regulated kinase 1/2 and JNK1/2. Both MAPKs were upstream to p65/NF-kB inasmuch as both MAPKs' inhibitors PD98059 and SP600125 or their down-regulation by siRNA significantly blocked the TGF-β1-induced nuclear translocation of p65/NF-kB. In addition, p65/NF-κB siRNA knockdown inhibited the effects of TGF-β1 on both MMP-9 and cell migration/invasion. We conclude that TGF-β1 controls RSC96 Schwann cell migration and invasion through MMP-2 and MMP-9 activities. MMP-2 is controlled by SMAD2 whilst MMP-9 is controlled via an ERK1/2-JNK1/2-NF-κB dependent pathway.

Synthesis, characterization, DNA/BSA interactions and in vitro cytotoxicity study of palladium(II) complexes of hispolon derivatives

Thirteen novel palladium(II) complexes of the general formula [Pd(bipy)(O,O'-dkt)](PF₆), (where bipy is 2,2'-bipyridine and O,O'-dkt is β-diketonate ligand hispolon or its derivative) have been prepared through a metal-ligand coordination method that involves spontaneous formation of the corresponding diketonate scaffold. The obtained palladium(II) complexes have been characterized by NMR spectroscopy, ESI-mass spectrometry as well as elemental analysis. The cytotoxicity analysis indicates that most of the obtained palladium(II) complexes show promising growth inhibition in three human cancer cell lines. Flow cytometry analysis shows complex 3e could promote intracellular reactive oxygen species (ROS) accumulation and lead cancer cell death. And the suppression of ROS accumulation and the rescue of cell viability in HeLa cells by N-acetyl-L-cysteine (NAC) suggest the possible link between the increase in ROS generation and cytotoxicity of complex 3e. Flow cytometry analysis also reveal that complex 3e cause cell cycle arrest in the G2/M phase and collapse of the mitochondrial membrane potential, promote the generation of ROS and lead to tumor cell apoptosis. The interactions of complex 3e with calf thymus DNA (CT-DNA) have been evaluated by UV-Vis spectroscopy, fluorescence quenching experiments and viscosity measurements, which reveal that the complex interact with CT-DNA through minor groove binding and/or electrostatic interactions. Further, the results of fluorescence titration and site marker competitive experiment on bovine serum albumin (BSA) suggest that complex 3e can quench the fluorescence of BSA via a static quenching process and bind to BSA in Sudlow's site II.

[Pt(O,O'-acac)(γ-acac)(DMS)] Induces Autophagy in Caki-1 Renal Cancer Cells

We have demonstrated the cytotoxic effects of [Pt(O,O′-acac)(γ-acac)(dimethyl sulfide (DMS))] on various immortalized cell lines, in primary cultures, and in murine xenograft models in vivo. Recently, we also showed that [Pt(O,O′-acac)(γ-acac)(DMS)] is able to kill Caki-1 renal cells both in vivo and in vitro. In the present paper, apoptotic and autophagic effects of [Pt(O,O′-acac)(γ-acac)(DMS)] and cisplatin were studied and compared using Caki-1 cancerous renal cells. The effects of cisplatin include activation of caspases, proteolysis of enzyme poly ADP ribose polymerase (PARP), control of apoptosis modulators B-cell lymphoma 2 (Bcl-2), Bcl-2-associated X protein (Bax), and BH3-interacting domain death agonist (Bid), and cell cycle arrest in G2/M phase. Conversely, [Pt(O,O′-acac)(γ-acac)(DMS)] did not induce caspase activation, nor chromatin condensation or DNA fragmentation. The effects of [Pt(O,O′-acac)(γ-acac)(DMS)] include microtubule-associated proteins 1A/1B light chain 3B (LC3)-I to LC3-II conversion, Beclin-1 and Atg-3, -4, and -5 increase, Bcl-2 decrease, and monodansylcadaverine accumulation in autophagic vacuoles. [Pt(O,O′-acac)(γ-acac)(DMS)] also modulated various kinases involved in intracellular transduction regulating cell fate. [Pt(O,O′-acac)(γ-acac)(DMS)] inhibited the phosphorylation of mammalian target of rapmycin (mTOR), p70S6K, and AKT, and increased the phosphorylation of c-Jun N-terminal kinase (JNK1/2), a kinase activity pattern consistent with autophagy induction. In conclusion, while in past reports the high cytotoxicity of [Pt(O,O′-acac)(γ-acac)(DMS)] was always attributed to its ability to trigger an apoptotic process, in this paper we show that Caki-1 cells die as a result of the induction of a strong autophagic process.

ADP sensitizes ZL55 cells to the activity of cisplatin

Malignant pleural mesothelioma (MPM) is an aggressive malignant tumor in which cisplatin therapy is commonly used, although its effectiveness is limited. It follows that research efforts dedicated to identify promising combinations that can synergistically kill cancer cells are needed. Because we recently demonstrated that ADP inhibits the proliferation of ZL55 cells, an MPM-derived cell line obtained from bioptic samples of asbestos-exposed patients. Our objective in this study was to investigate the hypothesis that ADP also potentiates the cytotoxic activity of cisplatin. Results show that in ZL55 cells ADP enhanced (a) the cytotoxicity of cisplatin by 12-fold, (b) the restraint of cell clonogenic potential cisplatin-mediated, and (c) the number of apoptotic cells. Cisplatin, but not ADP, caused caspases activation; nevertheless, poly(ADP-ribose) polymerase-1 was not only cleaved in cisplatin-treated cells but also in cells treated with ADP alone. Furthermore, ADP, but not cisplatin, decreased mTOR and 6SK phosphorylations. Both ADP and cisplatin increased p53 protein, but ADP was also able to enhance p53 messenger RNA. P53 silencing resulted in a very large decrement of cell death induced by ADP or by cisplatin and reverted ADP effects on mTOR/S6K phosphorylation, suggesting that activated p53 may act as a negative regulator of mTOR. Consistently, the inhibition of mTOR by rapamycin also sensitized cells to cisplatin, and the effects of cisplatin plus rapamycin were identical to those obtained with cisplatin plus ADP. These findings suggest that the combination of ADP and cisplatin may be a promising strategy for the clinical treatment of cisplatin-resistant MPM.

Adenosine diphosphate regulates MMP2 and MMP9 activity in malignant mesothelioma cells

Although an association between cancer progression and matrix metalloproteinase (MMP) 2 and MPP9 expression has been known, the expression, nuclear localization, and physiologically controlled activation of these two MMPs have not been investigated in malignant mesothelioma cells. We examined the expression and intracellular localization of MMP2/9 in ZL55 malignant mesothelioma cells, as well as their regulation by ADP. Using real-time PCR, we showed that activation of the P2Y1 receptor by ADP increased the expression of MMP2/9 mRNAs; MMP2/9 collected from conditioned media also showed an increase in activity; and ADP induced the nuclear localization of MMP2/9. The effects of ADP on transcription of the MMPs were due to activation of c-Src, Akt, and NF-κB, while ERK1/2 phosphorylation was needed for the increase in enzymatic activity and the regulation of nuclear import. We also showed that the nuclear localization of MMP2/9 induced by ADP causes the cleavage and inactivation of poly-ADP-ribose polymerase-1. These findings may help to elucidate the mechanisms regulating MMP2/9 activation in ZL55 human epithelioid mesothelioma cells, and perhaps other cells. Therapeutic approaches that promote ADP accumulation in a tumor environment may constitute an effective means to induce anticancer activity.

Inhibition of ZL55 cell proliferation by ADP via PKC-dependent signalling pathway

Extracellular nucleotides can regulate cell proliferation in both normal and tumorigenic tissues. Here, we studied how extracellular nucleotides regulate the proliferation of ZL55 cells, a mesothelioma-derived cell line obtained from bioptic samples of asbestos-exposed patients. ADP and 2-MeS-ADP inhibited ZL55 cell proliferation, whereas ATP, UTP, and UDP were inactive. The nucleotide potency profile and the blockade of the ADP-mediated inhibitory effect by the phospholipase C inhibitor U-73122 suggest that P2Y1 receptor controls ZL55 cell proliferation. The activation of P2Y1 receptor by ADP leads to activation of intracellular transduction pathways involving [Ca²⁺ ]_i , PKC-δ/PKC-α, and MAPKs, ERK1/2 and JNK1/2. Cell treatment with ADP or 2-MeS-ADP also provokes the activation of p53, causing an accumulation of the G1 cyclin-dependent kinase inhibitors p21^WAF1 and p27^Kip . Inhibition of ZL55 cell proliferation by ADP was completely reversed by inhibiting MEK1/2, or JNK1/2, or PKC-δ, and PKC-α. Through the inhibition of ADP-activated transductional kinases it was found that PKC-δ was responsible for JNK1/2 activation. JNK1/2 has a role in transcriptional up-regulation of p53, p21^WAF1/CIP1 , and p27^kip1 . Conversely, the ADP-activated PKC-α provoked ERK1/2 phosphorylation. ERK1/2 increased p53 stabilization, required to G1 arrest of ZL55 cells. Concluding, the importance of the study is twofold: first, results shed light on the mechanism of cell cycle inhibition by ADP; second, results suggest that extracellular ADP may inhibit mesothelioma progression.

Apoptosis by [Pt(O,O'-acac)(γ-acac)(DMS)] requires PKC-δ mediated p53 activation in malignant pleural mesothelioma

Mesothelioma cancer cells have epithelioid or sarcomatoid morphology. The worst prognosis is associated with sarcomatoid phenotype and resistance to therapy is affected by cells heterogeneity. We recently showed that in ZL55 mesothelioma cell line of epithelioid origin [Pt(O,O'-acac)(γ-acac)(DMS)] (Ptac2S) has an antiproliferative effect in vitro and in vivo. Aim of this work was to extend the study on the effects of Ptac2S on ZL34 cell line, representative of sarcomatoid mesothelioma. ZL34 cells were used to assay the antitumor activity of Ptac2S in a mouse xenograft model in vivo. Then, both ZL34 and ZL55 cells were used in order to assess the involvement of p53 protein in (a) the processes underlying the sensitivity to chemotherapy and (b) the activation of various transduction proteins involved in apoptosis/survival processes. Ptac2S increases ZL34 cell death in vivo compared with cisplatin and, in vitro, Ptac2S was more efficacious than cisplatin in inducing apoptosis. In Ptac2S-treated ZL34 and ZL55 cells, p53 regulated gene products of apoptotic BAX and anti-apoptotic Bcl-2 proteins via transcriptional activation. Ptac2S activated PKC-δ and PKC-ε; their inhibition by PKC-siRNA decreased the apoptotic death of cells. PKC-δ was responsible for JNK1/2 activation that has a role in p53 activation. In addition, PKC-ε activation provoked phosphorylation of p38MAPK, concurring to apoptosis. In ZL34 cells, Ptac2S also activated PKC-α thus provoking ERK1/2 activation; inhibition of PKC-α, or ERK1/2, increased Ptac2S cytotoxicity. Results confirm that Ptac2S is a promising therapeutic agent for malignant mesothelioma, giving a substantial starting point for its further validation.

CCL20 promotes migration and invasiveness of human cancerous breast epithelial cells in primary culture

The relation between the tumor and its microenvironment is one of the most interesting and less understood issues. Recently, we showed a role of CCL20 chemokine in proning the healthy tissue neighboring the tumor to carcinogenesis. Besides, tumor-secreted CCL20 induced proliferation, migration, and EMT of healthy cells. In this context, we have studied here if CCL20 had effects on the migration of cancer cells and the intracellular pathways used in breast epithelial cells in primary culture. Using molecular (siRNA) and pharmacological (inhibitors) techniques, we found multiple signaling kinases to be activated and involved in CCL20-induced tumor breast cell migration. CCL20 provoked a 2.5-fold increase of cell migration and invasion; CCL20 also enhanced MMP- 2 and MMP-9 mRNAs/protein expression and activities. Cell migration and invasiveness due to CCL20 significantly decreased when MMP-2 and MMP-9 were inhibited in CCL20-stimulated cells. CCL20 controlled MMP-2 expression through the JAK2/STAT3 pathway, while the expression of MMP-9 occurred by PKC-α that activated, consequently, c-Src, Akt, and finally NF-kB. These results reveal a role for CCL20 also in tumor breast cell and point to CCL20 as a novel therapeutic target in cancer.

In Vitro and In Vivo Antitumor Activity of [Pt(O,O'-acac)(γ-acac)(DMS)] in Malignant Pleural Mesothelioma

Malignant pleural mesothelioma (MPM) is an aggressive malignancy highly resistant to chemotherapy. There is an urgent need for effective therapy inasmuch as resistance, intrinsic and acquired, to conventional therapies is common. Among Pt(II) antitumor drugs, [Pt(O,O′-acac)(γ-acac)(DMS)] (Ptac2S) has recently attracted considerable attention due to its strong in vitro and in vivo antiproliferative activity and reduced toxicity. The purpose of this study was to examine the efficacy of Ptac2S treatment in MPM. We employed the ZL55 human mesothelioma cell line in vitro and in a murine xenograft model in vivo, to test the antitumor activity of Ptac2S. Cytotoxicity assays and Western blottings of different apoptosis and survival proteins were thus performed. Ptac2S increases MPM cell death in vitro and in vivo compared with cisplatin. Ptac2S was more efficacious than cisplatin also in inducing apoptosis characterized by: (a) mitochondria depolarization, (b) increase of bax expression and its cytosol-to-mitochondria translocation and decrease of Bcl-2 expression, (c) activation of caspase-7 and -9. Ptac2S activated full-length PKC-δ and generated a PKC-δ fragment. Full-length PKC-δ translocated to the nucleus and membrane, whilst PKC-δ fragment concentrated to mitochondria. Ptac2S was also responsible for the PKC-ε activation that provoked phosphorylation of p38. Both PKC-δ and PKC-ε inhibition (by PKC–siRNA) reduced the apoptotic death of ZL55 cells. Altogether, our results confirm that Ptac2S is a promising therapeutic agent for malignant mesothelioma, providing a solid starting point for its validation as a suitable candidate for further pharmacological testing.

Antitumour and antiangiogenic activities of [Pt(O,O'-acac)(γ-acac)(DMS)] in a xenograft model of human renal cell carcinoma

BACKGROUND AND PURPOSE

It is thought that the mechanism of action of anticancer chemotherapeutic agents is mainly due to a direct inhibition of tumour cell proliferation. In tumour specimens, the endothelial cell proliferation rate increases, suggesting that the therapeutic effects of anticancer agents could also be attributed to inhibition of tumour angiogenesis. Hence, we investigated the potential effects of [Pt(O,O'-acac)(γ-acac)(DMS)] ([Pt(DMS)]), a new platinum drug for non-genomic targets, on human renal carcinoma and compared them with those of the well-established anticancer drug, cisplatin.

EXPERIMENTAL APPROACH

Tumour growth, tumour cell proliferation and microvessel density were investigated in a xenograft model of renal cell carcinoma, developed by injecting Caki-1 cells into BALB/c nude mice. The antiangiogenic potential of compounds was also investigated using HUVECs.

KEY RESULTS

Treatment of the Caki-1 cells with cisplatin or [Pt(DMS)] resulted in a dose-dependent inhibition of cell survival, but the cytotoxicity of [Pt(DMS)] was approximately fivefold greater than that of cisplatin. [Pt(DMS)] was much more effective than cisplatin at inhibiting tumour growth, proliferation and angiogenesis in vivo, as well as migration, tube formation and MMP1, MMP2 and MMP9 secretion of endothelial cells in vitro. Whereas, cisplatin exerted a greater cytotoxic effect on HUVECs, but did not affect tube formation or the migration of endothelial cells. In addition, treatment of the xenograft mice with [Pt(DMS)] decreased VEGF, MMP1 and MMP2 expressions in tumours.

CONCLUSIONS AND IMPLICATIONS

The antiangiogenic and antitumour activities of [Pt(DMS)] provide a solid starting point for its validation as a suitable candidate for further pharmacological testing.

Novel Platinum(II) compounds modulate insulin-degrading enzyme activity and induce cell death in neuroblastoma cells

The properties of three novel Platinum(II) compounds toward the insulin-degrading enzyme (IDE) enzymatic activity have been investigated under physiological conditions. The rationale of this study resides on previous observations that these compounds, specifically designed and synthesized by some of us, induce apoptosis in various cancer cell lines, whereas IDE has been proposed as a putative oncogene involved in neuroblastoma onset and progression. Two of these compounds, namely [PtCl(O,O'-acac)(DMSO)] and [Pt(O,O'-acac)(γ-acac)(DMS)], display a modulatory behavior, wherefore activation or inhibition of IDE activity occurs over different concentration ranges (suggesting the existence of two binding sites on the enzyme). On the other hand, [Pt(O,O'-acac)(γ-acac)(DMSO)] shows a typical competitive inhibitory pattern, characterized by a meaningful affinity constant (K i  = 0.95 ± 0.21 μM). Although all three compounds induce cell death in neuroblastoma SHSY5Y cells at concentrations exceeding 2 μM, the two modulators facilitate cells' proliferation at concentrations ≤ 1.5 μM, whereas the competitive inhibitor [Pt(O,O'-acac)(γ-acac)(DMSO)] only shows a pro-apoptotic activity at all investigated concentrations. These features render the [Pt(O,O'-acac)(γ-acac)(DMSO)] a promising "lead compound" for the synthesis of IDE-specific inhibitors (not characterized yet) with therapeutic potentiality.

[Pt(O,O'-acac)(γ-acac)(DMS)] alters SH-SY5Y cell migration and invasion by the inhibition of Na+/H+ exchanger isoform 1 occurring through a PKC-ε/ERK/mTOR Pathway

We previously showed that [Pt(O,O'-acac)(γ-acac)(DMS)] ([Pt(acac)2(DMS)]) exerted substantial cytotoxic effects in SH-SY5Y neuroblastoma cells, and decreased metalloproteases (MMPs) production and cells migration in MCF-7 breast cancer cells. The ubiquitously distributed sodium-hydrogen antiporter 1 (NHE1) is involved in motility and invasion of many solid tumours. The present study focuses on the effects of [Pt(acac)2(DMS)] in SH-SY5Y cell migration and also on the possibility that NHE1 may be involved in such effect. After sublethal [Pt(acac)2(DMS)] treatment cell migration was examined by wounding assay and cell invasion by transwell assay. NHE1 activity was measured in BCECF-loaded SH-SY5Y as the rate of Na+-dependent intracellular pH recovery in response to an acute acid pulse. Gelatin zymography for MMP-2/9 activities, Western blottings of MMPs, MAPKs, mTOR, S6 and PKCs and small interfering RNAs to PKC-ε/-δ mRNA were performed. Sublethal concentrations of [Pt(acac)2(DMS)] decreases NHE1 activity, inhibits cell migration and invasion and decreases expression and activity of MMP-2 and -9. [Pt(acac)2(DMS)] administered to SH-SY5Y cells provokes the increment of ROS, generated by NADPH oxidase, responsible for the PKC-ε and PKC-δ activation. Whilst PKC-δ activates p38/MAPK, responsible for the inhibition of MMP-2 and -9 secretion, PKC-ε activates a pathway made of ERK1/2, mTOR and S6K responsible for the inhibition of NHE1 activity and cell migration. In conclusion, we have shown a drastic impairment in tumour cell metastatization in response to inhibition of NHE1 and MMPs activities by [Pt(acac)2(DMS)] occurring through a novel mechanism mediated by PKC-δ/-ε activation.

Different apoptotic effects of [Pt(O,O'-acac)(γ-acac)(DMS)] and cisplatin on normal and cancerous human epithelial breast cells in primary culture

BACKGROUND AND PURPOSE

The aim of this study was to determine whether [platinum (Pt)(O,O'-acetylacetonate (acac))(γ-acac)(dimethylsulphide (DMS))] is differentially cytotoxic in normal and cancer cells, and to measure comparative levels of cytotoxicity compared with cisplatin in the same cells.

EXPERIMENTAL APPROACH

We performed experiments on cancerous and normal epithelial breast cells in primary culture obtained from the same patients. The apoptotic effects [Pt(O,O'-acac)(γ-acac)(DMS)] and cisplatin in cancerous and normal breast cells were compared.

KEY RESULTS

Cancer cells were more sensitive to [Pt(O,O'-acac)(γ-acac)(DMS)] (IC50 = 5.22 ± 1.2 μmol·L(-1)) than normal cells (IC50 = 116.9 ± 8.8 μmol·L(-1)). However, the difference was less strong when cisplatin was used (IC50 = 96.0 ± 6.9 and 61.9 ± 6.1 μmol·L(-1) for cancer and normal cells respectively). Both compounds caused reactive oxygen species (ROS) production with different mechanisms: [Pt(O,O'-acac)(γ-acac)(DMS)] quickly activated NAD(P)H oxidase while cisplatin caused a slower formation of mitochondrial ROS. Cisplatin and [Pt(O,O'-acac)(γ-acac)(DMS)] caused activation of caspases, proteolysis of PARP and modulation of Bcl-2, Bax and Bid. [Pt(O,O'-acac)(γ-acac)(DMS)] also caused leakage of cytochrome c from the mitochondria. Overall, these processes proceeded more quickly in cells treated with [Pt(O,O'-acac)(γ-acac)(DMS)] compared with cisplatin. [Pt(O,O'-acac)(γ-acac)(DMS)] effects were faster and quantitatively greater in cancer than in normal cells. [Pt(O,O'-acac)(γ-acac)(DMS)] caused a fast decrease of mitochondrial membrane potential, especially in cancer cells.

CONCLUSIONS AND IMPLICATIONS

[Pt(O,O'-acac)(γ-acac)(DMS)] was specific to breast cancer cells in primary culture, and this observation makes this compound potentially more interesting than cisplatin.

Antitumor activity of [Pt(O,O'-acac)(γ-acac)(DMS)] in mouse xenograft model of breast cancer

The higher and selective cytotoxicity of [Pt(O,O′-acac)(γ-acac)(DMS)] toward cancer cell in both immortalized cell lines and in breast cancer cells in primary cultures, stimulated a pre-clinical study so as to evaluate its therapeutic potential in vivo. The efficacy of [Pt(O,O′-acac)(γ-acac)(DMS)] was assessed using a xenograft model of breast cancer developed by injection of MCF-7 cells in the flank of BALB/c nude mice. Treatment of solid tumor-bearing mice with [Pt(O,O′-acac)(γ-acac)(DMS)] induced up to 50% reduction of tumor mass compared with an average 10% inhibition recorded in cisplatin-treated animals. Thus, chemotherapy with [Pt(O,O′-acac)(γ-acac)(DMS)] was much more effective than cisplatin. We also demonstrated enhanced in vivo pharmacokinetics, biodistribution and tolerability of [Pt(O,O′-acac)(γ-acac)(DMS)] when compared with cisplatin administered in Wistar rats. Pharmacokinetics studies with [Pt(O,O′-acac)(γ-acac)(DMS)] revealed prolonged Pt persistence in systemic blood circulation and decreased nefrotoxicity and hepatotoxicity, major target sites of cisplatin toxicity. Overall, [Pt(O,O′-acac)(γ-acac)(DMS)] turned out to be extremely promising in terms of greater in vivo anticancer activity, reduced nephrotoxicity and acute toxicity compared with cisplatin.

PFHxS induces apoptosis of neuronal cells via ERK1/2-mediated pathway

Perfluorohexanesulfonate (PFHxS) is one of the most widely distributed perfluoroalkyl compounds (PFCs) and its possible neurotoxicity has been suggested. However, the effects of PFHxS on neuronal function remain to be elucidated. In this study, the effects of PFHxS on neuronal cell death and the underlying mechanisms were examined. Cerebellar granule cells (CGCs) were isolated from 7-day old rat pups and maintained in culture for additional 7d. The apoptotic effects of PFHxS were determined by caspase-3 activity and TUNEL staining. PFHxS increased the apoptotic death of CGC in concentration-dependent manner. It also increased the activation of ERK1/2, JNK and p38 MAPK with different temporal activation. PD98059, an inhibitor of ERK1/2 pathway, completely blocked PFHxS-induced apoptosis whereas SP600125, a JNK inhibitor, significantly increased the apoptosis, showing their opposite roles in the apoptosis of CGCs. Treatment of antioxidants, Trolox or N-acetylcysteine (NAC), completely blocked ROS generation by PFHxS but neither of these antioxidants prevented PFHxS-induced apoptosis, suggesting that ROS may not play a key role in the process of apoptosis. PD98059 prevented ROS accumulation by PFHxS but the ERK1/2 activation was not affected by Trolox or NAC. These results indicate that ROS is one of downstream targets of ERK1/2, not vice versa. Taken together, PFHxS increased apoptosis of CGC in ERK1/2-dependent manner, where downstream pathway other than ROS may play a major role. This is a first report that PFHxS induces apoptosis of CGC isolated from the developing brain and its possible mode of action is associated with ERK1/2 pathway.

A new platinum(II) compound anticancer drug candidate with selective cytotoxicity for breast cancer cells

[Pt(O,O′-acac)(γ-acac)(DMS)] (PtAcD) is able to induce apoptosis in various human cancer cells, including the cisplatin-resistant human breast carcinoma MCF-7 cells. Here, to confirm that PtAcD has the potentiality for therapeutic intervention, we studied its effects in primary cultured epithelial breast cells obtained from cancers and also from the corresponding histologically proven non-malignant tissue adjacent to the tumor. We demonstrated that PtAcD (1) is more cytotoxic in cancer than in normal breast cells; (2) activated NAD(P)H oxidase, leading to PKC-ζ and PKC-α tanslocations; (3) activated antiapoptotic pathways based on the PKC-α, ERK1/2 and Akt kinases; (4) activated PKC-ζ and, only in cancer cell PKC-δ, responsible for the sustained phosphorylation of p38 and JNK1/2, kinases both of which are involved in the mitochondrial apoptotic process. Moreover, crosstalk between ERK/Akt and JNK/p38 pathways affected cell death and survival in PtAcD-treated breast cell. In conclusion, this study adds and extends data that highlight the pharmacological potential of PtAcD as an anti breast cancer drug.

CCL20 induces migration and proliferation on breast epithelial cells

The communication between the tumor cells and the surrounding cells helps drive the process of tumor progression. Since the microenvironment of breast cancer includes CCL20 chemokine, the purpose of this study was to determine whether CCL20 modulates the physiology of healthy breast epithelial cells in areas adjacent to the tumor. Therefore, primary cultures of mammary cells taken from normal peritumoral areas were used. We assessed that breast cells expressed CCR6 CCL20 receptor. Using molecular (siRNA) and pharmacological (inhibitors) techniques, we found multiple signaling kinases to be activated by CCR6 and involved in CCL20-induced breast cell proliferation and migration. The binding of 10 ng/ml CCL20 to CCR6 induced cell migration whilst higher concentrations (from 15 to 25 ng/ml) led to cell proliferation. CCL20 controlled cell migration and MMP-9 expression by PKC-alpha that activated Src, which caused the activation of downstream Akt, JNK, and NF-kB pathways. Furthermore, higher CCL20 concentrations increased cycE and decreased p27Kip expression ending in enhanced cell proliferation. Cell proliferation occurred through PKC-epsilon activation that transactivated EGFR and ERK1/2/MAPK pathway. Although activated by different CCL20 concentrations, these pathways function in parallel and crosstalk to some extent, inasmuch as Akt activation was responsible for ERK1/2 nuclear translocation and enhanced the transcription of of c-fos and c-myc, involved in cell proliferation. In summary, tumor cells exchange signals with the surrounding healthy cells modifying the extracellular matrix through enzyme secretion; thus, CCL20 might be a factor involved in the ontogeny of breast carcinoma.

Cisplatin-related drugs for nongenomic targets: Forcing the reactivity with nucleobases

The products obtained by forcing the reaction with nucleosides (guanosine, Guo, and adenosine, Ado) of potential anticancer drugs for nongenomic targets [PtCl(O,O'-acac)(L)] (L = dimethyl sulfoxide, DMSO; dimethyl sulfide, DMS), closely related to their very powerful organometallic analogues [Pt(O,O'-acac)(γ-acac)(L)], have been studied. [PtCl(O,O'-acac)(L)] and [Pt(O,O'-acac)(γ-acac)(L)] complexes were reported unreactive toward nucleobases. Aquo species [Pt(O,O'-acac)H2O(L)]+, obtained from [PtCl(O,O'-acac)(L)] by Ag+ driven coordinated Cl– removal, gave access to [Pt(O,O'-acac)(L)(nucleoside)]+ ([Pt(O,O'-acac)(DMSO)(Guo)]+, [Pt(O,O'-acac)(DMS)(Guo)]+, [Pt(O,O'-acac)(DMSO)(Ado)]+). The effect of the chelate oxygen donor acac (with respect to a chelate diammine), the role of the sulfur ligand (DMSO, DMS), and the influence of the purinic nucleoside itself on the coordinated Guo or Ado dynamic motions in [Pt(O,O'-acac)(L)(nucleoside)]+ complexes have been investigated by NMR spectroscopy. Interestingly, a slow rotation of nucleobase around the Pt–N(7) bond with formation of two rotamers was observed already at room temperature only in the case of [Pt(O,O'-acac)(DMSO)(Guo)]+. On the other hand, no hindered rotation at room temperature was detected in the analogous [Pt(O,O'-acac)(DMS)(Guo)]+ and [Pt(O,O'-acac)(DMSO)(Ado)]+ complexes. Data suggest that rotation of the nucleoside in [Pt(O,O'-acac)(L)(nucleoside)]+ is very different with respect to the analogous [Pt(diammine)(L)(nucleoside)]2+ systems, due to specific interactions between the acac chelate ligand, the DMSO, and the nucleobase.

In vitro anticancer activity of cis-diammineplatinum(II) complexes with β-diketonate leaving group ligands

Five cationic platinum(II) complexes of general formula, [Pt(NH(3))(2)(β-diketonate)]X are reported, where X is a noncoordinating anion and β-diketonate = acetylacetonate (acac), 1,1,1,-trifluoroacetylacetonate (tfac), benzoylacetonate (bzac), 4,4,4-trifluorobenzoylacetonate (tfbz), or dibenzoylmethide (dbm), corresponding, respectively, to complexes 1-5. The log P values and the stabilities of 1-5 in aqueous solution were evaluated. The phenyl ring substituents of 3-5 increase the lipophilicity of the resulting complexes, whereas the trifluoromethyl groups of 2 and 4 decrease the stability of the complexes in aqueous solution. The uptake of 1-5 in HeLa cells increases as the lipophilicity of the investigated complex increases. Cancer cell cytotoxicity studies indicate that 1 and 3 are the least active complexes whereas 2, 4, and 5 are comparable in activity to cisplatin.