Search

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.

It was previously shown that [Pt(O,O'-acac)(γ-acac)(DMS)] induces apoptosis in various cancer cells and exerts antimetastatic responses in vitro. In rats, [Pt(O,O'-acac)(γ-acac)(DMS)] reaches the central nervous system in quantities higher than cisplatin causing less excitotoxicity. The aim of the present paper was to investigate whether [Pt(O,O'-acac)(γ-acac)(DMS)] is able to exert cytotoxic effects on SH-SY5Y human neuroblastoma cell line, and to study the intracellular transduction mechanisms underlying these effects. Here we have demonstrated that [Pt(O,O'-acac)(γ-acac)(DMS)] was more effective than cisplatin in provoking apoptosis characterized by: (a) mitochondria depolarization, (b) decrease of Bcl-2 expression and increase of BAX expressions with cytosol-to-mitochondria translocation, (c) activation of caspase-7 and -9 and (d) generation of reactive oxygen species (ROS). [Pt(O,O'-acac)(γ-acac)(DMS)] provoked the activation of the following signalling kinases that were interacting with each other: PKC-δ and -ɛ, ERK1/2, p38MAPK, JNK1/2, NF-κB, c-src and FAK. We found that ROS generated by NADPH oxidase was responsible for the [Pt(O,O'-acac)(γ-acac)(DMS)]-mediated PKC-δ and -ɛ activation and consequential phosphorylation of all MAPKs. [Pt(O,O'-acac)(γ-acac)(DMS)]-induced mitochondrial apoptosis was blocked when p38MAPK and JNK1/2 were inhibited, whilst the effects on Bax/Bcl-2 mRNA and protein levels were blocked inhibiting NF-κB. NF-κB nuclear translocation was blocked inhibiting MEK1/2 activity. In addition to the induction of apoptosis [Pt(O,O'-acac)(γ-acac)(DMS)] downregulated pro-survival pathway. Survival inhibition started from mitochondrial ROS generation which induced c-src, FAK and Akt activation. In conclusion, our results suggest that [Pt(O,O'-acac)(γ-acac)(DMS)] may be considered a promising compound for the treatment of neuroblastoma. Further studies are warranted to explore in detail the therapeutic potential of this compound., (Copyright © 2011 Elsevier Inc. All rights reserved.)

Background and Purpose: We showed previously that cisplatin inititates a signalling pathway mediated by PKC-delta/extracellular signal-regulated kinase (ERK), important for maintaining viability in PC Cl3 thyroid cells. The studies described herein examined whether c-fos was associated with cisplatin resistance and the signalling link between c-fos and PKC-delta/ERK., Experimental Approach: Cells were treated with various pharmacological inhibitors of PKCs and ERK, or were depleted of c-fos, PKC-delta, PKC-epsilon and caspase-3 by small interfering RNA (siRNA), then incubated with cisplatin and cytotoxicity assessed., Key Results: Cisplatin provokes the induction of c-fos and the activation of conventional PKC-beta, and novel PKC-delta and -epsilon. The cisplatin-provoked c-fos induction was decreased by Gö6976, a PKC-beta inhibitor; by siRNA for PKC-delta- but not that for PKC-epsilon or by PD98059, a mitogen-activated protein kinase/ERK kinase inhibitor. Expression of c-fos was abolished by GF109203X, an inhibitor of all PKC isoforms, or by PD98059 plus Gö6976 or by PKC-delta-siRNA plus Gö6976. When c-fos expression was blocked by siRNA, cisplatin cytotoxicity was strongly enhanced with increased caspase-3 activation. In PKC-delta-depleted cells treated with cisplatin, caspase-3 activation was increased and cell viability decreased. In these PKC-delta-depleted cells, PD98059 did not affect caspase-3 activation., Conclusions and Implications: In PC Cl3 cells, in the cell signalling pathways that lead to cisplatin resistance, PKC-delta controls ERK activity and, together with PKC-beta, also the induction of c-fos. Hence, the protective role of c-fos in thyroid cells has the potential to provide new opportunities for therapeutic intervention.

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. [ABSTRACT FROM AUTHOR]

Cisplatin is commonly employed in therapy of mesothelioma but its efficacy is limited and the mechanisms by which induces its effects are not clearly understood. PKCs can regulate cisplatin sensitivity. PKCs effects on cellular sensitivity/resistance depend on the pattern of active PKC isozymes as well as on cellular context. The present study was undertaken to determine if specific PKC isoforms regulate cisplatin-induced apoptosis in the human mesothelioma ZL55 cells. Cells were treated with cisplatin at various concentrations and for different incubation periods. Cytotoxicity assays and Western blottings of various proteins involved in apoptosis and survival were then performed. Exposure of ZL55 cells to cisplatin at concentrations ranging from 1 to 200 μM resulted in a dose-dependent inhibition of cell survival and the activation of the mitochondrial apoptotic pathway. Cisplatin activated full-length PKC-δ and generated a PKC-δ fragment. PKC-δ inhibition (by PKC-δ–siRNA) decreased ZL55 cell apoptosis. Full-length PKC-δ translocated to the nucleus and activated caspase-3 expression, whereas PKC-δ fragment preferentially localized to mitochondria. Cisplatin also provoked the generation of reactive oxygen species (ROS) by NADPH oxidase. ROS increment was responsible for the PKC-α activation that provoked EGFR transactivation and consequential phosphorylation of ERK1/2. The inhibition of this pathway at various level (PKC-α, EGFR or ERK1/2) increased cisplatin-induced cytotoxicity. The results suggest that PKC-δ is an essential part of the apoptotic program in mesothelioma cells, whereas PKC-α mediates a pro-survival response to cisplatin. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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, inhibites 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. [ABSTRACT FROM AUTHOR]

Background and Purpose: We showed previously that a new Pt(II) complex ([Pt(O,O'-acac)(gamma-acac)(DMS)]) exerted high and fast apoptotic processes in MCF-7 cells. The objective of this study was to investigate the hypothesis that [Pt(O,O'-acac)(gamma-acac)(DMS)] is also able to exert anoikis and alter the migration ability of MCF-7 cells, and to show some of the signalling events leading to these alterations.Experimental Approach: Cells were treated with sublethal doses of [Pt(O,O'-acac)(gamma-acac)(DMS)], and the efficiency of colony initiation and anchorage-independent growth was assayed; cell migration was examined by in vitro culture wounding assay. Gelatin zymography for MMP-2 and -9 activities, Western blottings of MMPs, MAPKs, Src, PKC-epsilon and FAK, after [Pt(O,O'-acac)(gamma-acac)(DMS)] treatment, were also performed.Key Results: Sub-cytotoxic drug concentrations decreased the: (i) anchorage-dependent and -independent growth; (ii) migration ability; and (iii) expression and activity of MMP-2 and MMP-9. [Pt(O,O'-acac)(gamma-acac)(DMS)] provoked the generation of reactive oxygen species (ROS), and the activation of p38MAPK, Src and PKC-epsilon. p38MAPK phosphorylation, cell anoikis and migration due to [Pt(O,O'-acac)(gamma-acac)(DMS)] were blocked by PKC-epsilon inhibition. Furthermore, Src inhibition blocked the [Pt(O,O'-acac)(gamma-acac)(DMS)]-provoked activation of PKC-epsilon, while ROS generation blockage inhibited the activation of Src, and also the decrement of phosphorylated FAK observed in detached [Pt(O,O'-acac)(gamma-acac)(DMS)]-treated cells.Conclusions and Implications: Sublethal concentrations of [Pt(O,O'-acac)(gamma-acac)(DMS)] induced anoikis and prevented events leading to metastasis via alterations in cell migration, anchorage independency, stromal interactions and MMP activity. Hence, [Pt(O,O'-acac)(gamma-acac)(DMS)] may be a promising therapeutic agent for preventing growth and metastasis of breast cancer. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]