Modulation of cell growth and cisplatin sensitivity by membrane gamma-glutamyltransferase in melanoma cells.

The plasma membrane enzyme c-glutamyltransferase (GGT) is regarded as critical for the maintenance of intracellular levels of glutathione (GSH). GGT expression has been implicated in drug resistance through elevation of intracellular GSH. The dependence of intracellular GSH on GGT expression was not conclusively ascertained. The present study was designed to investigate the role of GGT and of intracellular GSH levels in modulating proliferation and sensitivity to cisplatin of melanoma cells. GGT transfection resulted in increased growth, both in vitro and in tumour xenografts. In addition, GGT-transfected cells exhibited reduced sensitivity to cisplatin associated with lower DNA platination. A decrease in intracellular GSH levels, rather than an increase, was observed in GGT-transfected cells; moreover, in cysteine-deficient conditions, the expression of GGT did not provide transfected cells with the ability of utilising extracellular GSH. In conclusion, these results indicate that GGTactivity confers a growth advantage unrelated with intracellular glutathione supply, and are consistent with the interpretation that cisplatin resistance is the consequence of modifications of cellular pharmacokinetics as a result of extracellular drug inactivation by thiol metabolites originated by GGT-mediated GSH cleavage

Inhibition of proteasome deubiquitinating activity as a novel cancer therapy

Ubiquitin-tagged substrates are degraded by the 26S proteasome, which is a multisubunit complex comprising a proteolytic 20S core particle capped by 19S regulatory particles. The approval of bortezomib for the treatment of multiple myeloma validated the 20S core particle as an anticancer drug target. Here we describe the small molecule b-AP15 as a previously unidentified class of proteasome inhibitor that abrogates the deubiquitinating activity of the 19S regulatory particle. b-AP15 inhibited the activity of two 19S regulatory-particle-associated deubiquitinases, ubiquitin C-terminal hydrolase 5 (UCHL5) and ubiquitin-specific peptidase 14 (USP14), resulting in accumulation of polyubiquitin. b-AP15 induced tumor cell apoptosis that was insensitive to TP53 status and overexpression of the apoptosis inhibitor BCL2. We show that treatment with b-AP15 inhibited tumor progression in four different in vivo solid tumor models and inhibited organ infiltration in an acute myeloid leukemia model. Our results show that the deubiquitinating activity of the 19S regulatory particle is a new anticancer drug target.CancerfondenRadiumhemmets forskningsfonderVetenskapsrådetStrategiska forskningsstiftelsenVinnovaEuropean Union CHEMORES, Frame program 6 (LSHC-CT-2007-037665)Swedish Children Cancer SocietyAccepte

Synthesis and Superpotent Anticancer Activity of Tubulysins Carrying Non-hydrolysable N-Substituents on Tubuvaline

We thank Regione Autonoma della Sardegna RAS (Italy) for economic support by covering in part the costs of this research. I.U. acknowledges RAS for his fellowship (for grant numbers see the Supporting Information)Peer reviewedPostprin

Sulfonates-PMMA nanoparticles conjugates: A versatile system for multimodal application

a b s t r a c t We report herein the viability of a novel nanoparticles (NPs) conjugated system, namely the attachment, based on ionic and hydrophobic interactions, of different sulfonated organic salts to positively charged poly(methylmethacrylate) (PMMA)-based core-shell nanoparticles (EA0) having an high density of ammonium groups on their shells. In this context three different applications of the sulfonates@EA0 systems have been described. In detail, their ability as cytotoxic drugs and pro-drugs carriers was evaluated in vitro on NCI-H460 cell line and in vivo against human ovarian carcinoma IGROV-1 cells. Besides, 8-hydroxypyrene-1,3,6-trisulfonic acid, trisodium salt (HPTS) was chosen for NPs loading, and its internalization as bioimaging probe was evaluated on Hep G2 cells. Overall, the available data support the interest for these PMMA NPs@sulfonates systems as a promising formulation for theranostic applications. In vivo biological data strongly support the potential value of these core-shell NPs as delivery system for negatively charged drugs or biologically active molecules. Additionally, we have demonstrated the ability of these PMMA core-shell nanoparticles to act as efficient carriers of fluorophores. In principle, thanks to the high PMMA NPs external charge density, sequential and very easy post-loading of different sulfonates is achievable, thus allowing the preparation of nanocarriers either with bi-modal drug delivery behaviour or as theranostic systems

Synergistic Antitumor Effects of Novel HDAC Inhibitors and Paclitaxel In Vitro and In Vivo

Preclinical studies support the therapeutic potential of histone deacetylases inhibitors (HDACi) in combination with taxanes. The efficacy of combination has been mainly ascribed to a cooperative effect on microtubule stabilization following tubulin acetylation. In the present study we investigated the effect of paclitaxel in combination with two novel HDACi, ST2782 or ST3595, able to induce p53 and tubulin hyperacetylation. A synergistic effect of the paclitaxel/ST2782 (or ST3595) combination was found in wild-type p53 ovarian carcinoma cells, but not in a p53 mutant subline, in spite of a marked tubulin acetylation. Such a synergistic interaction was confirmed in additional human solid tumor cell lines harboring wild-type p53 but not in those expressing mutant or null p53. In addition, a synergistic cytotoxic effect was found when ST2782 was combined with the depolymerising agent vinorelbine. In contrast to SAHA, which was substantially less effective in sensitizing cells to paclitaxel-induced apoptosis, ST2782 prevented up-regulation of p21WAF1/Cip1 by paclitaxel, which has a protective role in response to taxanes, and caused p53 down-regulation, acetylation and mitochondrial localization of acetylated p53. The synergistic antitumor effects of the paclitaxel/ST3595 combination were confirmed in two tumor xenograft models. Our results support the relevance of p53 modulation as a major determinant of the synergistic interaction observed between paclitaxel and novel HDACi and emphasize the therapeutic interest of this combination

Effects of MnDPDP andICRF-187 on Doxorubicin-Induced Cardiotoxicityand Anticancer Activity1

Oxidative stress participates in doxorubicin (Dx)–induced cardiotoxicity. The metal complex MnDPDP and its metaboliteMnPLED possess SOD-mimetic activity, DPDP and PLED have, in addition, high affinity for iron. Mice wereinjected intravenously with MnDPDP, DPDP, or dexrazoxane (ICRF-187). Thirty minutes later, mice were killed, theleft atria were hung in organ baths and electrically stimulated, saline or Dx was added, and the contractility wasmeasured for 60 minutes. In parallel experiments, 10 μM MnDPDP or MnPLED was added directly into the organbath. The effect of MnDPDP on antitumor activity of Dx against two human tumor xenografts (MX-1 and A2780)was investigated. The in vitro cytotoxic activity was studied by co-incubating A2780 cells with MnDPDP, DPDP,and/or Dx. Dx caused a marked reduction in contractile force. In vivo treatment with MnDPDP and ICRF-187 attenuatedthe negative effect of Dx. When added directly into the bath, MnDPDP did not protect, whereas MnPLEDattenuated the Dx effect by approximately 50%. MnDPDP or ICRF-187 did not interfere negatively with the antitumoractivity of Dx, either in vivo or in vitro. Micromolar concentrations of DPDP but not MnDPDP displayed anin vitro cytotoxic activity against A2780 cells. The present results show that MnDPDP, after being metabolized toMnPLED, protects against acute Dx cardiotoxicity. Both in vivo and in vitro experiments show that cardioprotectiontakes place without interfering negatively with the anticancer activity of Dx. Furthermore, the results suggest thatthe previously described cytotoxic in vivo activity of MnDPDP is an inherent property of DPDP. Translational Oncology (2012) 5, 252–259funding agencies|Medical Research Council of Southeast Sweden|FORSS-85191|PledPharma AB||</p