Improved apoptotic cell death in drug-resistant non-small-cell lung cancer cells by tumor necrosis factor-related apoptosis-inducing ligand-based treatment.

Since response to platinum-based therapy in non-small-cell lung cancer (NSCLC) is poor, the present study was designed to rationally identify novel drug combinations in cell models including the A549 cell line and the cisplatin-resistant subline A549/Pt, characterized by reduced sensitivity to cisplatin-induced apoptosis and by upregulation of efflux transporters of the ATP binding cassette (ABC) superfamily. Given the molecular features of these cells, we focused on compounds triggering apoptosis through different mechanisms, such as the mitochondria-targeting drug arsenic trioxide and the phenanthridine analog sanguinarine, which induce apoptosis through the extrinsic pathway. Sanguinarine, not recognized by ABC transporters, could overcome cisplatin resistance and, when used in combination with arsenic trioxide, was synergistic in A549 and A549/Pt cells. The arsenic trioxide/sanguinarine cotreatment upregulated genes implicated in apoptosis activation through the extrinsic pathway. Drug combination experiments indicated that tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) treatment improved arsenic trioxide/sanguinarine efficacy, a feature associated with a striking apoptosis induction, particularly in the cisplatin-resistant variant. Thus, a synergistic interaction between sanguinarine and arsenic trioxide could be obtained independent of relative cell sensitivity to arsenic trioxide, and an enhanced apoptosis induction could be achieved in combination with TRAIL through modulation of the extrinsic apoptotic pathway. Antitumor activity studies supported the interest of drug combinations including TRAIL in NSCLC, indicating that drug-resistant NSCLC cells can efficiently be killed by the combination of proapoptotic agents. Our results suggest that the molecular changes occurring in treated cells may be exploited to rationally hit surviving cells.

Antitumor efficacy of the heparanase inhibitor SST0001 alone and in combination with antiangiogenic agents in the treatment of human pediatric sarcoma models.

The activity of heparanase is responsible for heparan sulfate cleavage, thus resulting in the release of heparan sulfate-bound growth factors. Since heparanase activity is upregulated in several tumor types and is implicated in the malignant behavior, the enzyme is regarded as a promising target for antitumor therapy. Based on previous evidence that the heparanase inhibitor SST0001, a non-anticoagulant N-acetylated glycol split heparin, is effective against an Ewing's sarcoma model, the present study was performed to extend the preclinical evaluation of SST0001 to a panel of pediatric sarcoma models, representative of various tumor histotypes (soft tissue and bone sarcomas) and to further elucidate its mode of action. SST0001 treatment downregulated several angiogenic factors in the conditioned media of sarcoma cells, inhibited the pro-invasive effect of heparin-binding factors (VEGF, bFGF, HGF, PDGF), and abrogated PDGF receptor tyrosine phosphorylation. Subcutaneous administration of SST0001 was very effective, resulting in a significant growth inhibition (range, 64-95%) of all tested tumor xenografts. The efficacy of SST0001 was enhanced in combination with antiangiogenic agents (bevacizumab, sunitinib) as documented by the high rate of complete response. The synergistic effect of SST0001 in combination with antiangiogenic agents is consistent with the heparanase mode of action and with the relevant role of heparin-binding proangiogenic/growth factors in the malignant behavior of sarcoma cells.

Comparación de la estabilización precoz versus tardía en el trauma raquimedular / Comparison of early versus delayed stabilization in spinal cord injury

El Trauma Raquimedular (TRM) es el resultado del daño18, 19 producido por lesiones traumáticas vertebrales a cualquier nivel y que comprometen a las diferentes estructuras que componen la columna vertebral, particularmente la médula espinal o sus raíces. Su incidencia14, 16 varía entre 11.5 y 53.4 por cada millón de habitantes y la causa más frecuente en nuestro país son las caídas. La región cervical es la más afectada seguida de la unión toracolumbar. Los segmentos torácicos y lumbares se comprometen con menor frecuencia, siendo similar en ambos niveles. Es una patología catastrófica para los pacientes y sus familias, ya que habitualmente los afectados son personas jóvenes en edad productiva17. Conjuntamente con el inmenso problema social, esta patología constituye un gran problema económico15 para los sistemas de salud debido al alto costo que implica su tratamiento tanto en la fase aguda como su posterior rehabilitación. El tratamiento del TRM se debe iniciar desde el momento en que se sospecha una lesión medular. Con el fin de evitar el daño medular secundario, además de la inmovilización precoz1,2,3,4,5,6,9, 20 se han probado distintos protocolos de tratamientos farmacológicos7,8,10,12,13, sin resultados que avalen su uso. Los protocolos basados en los estudios NASCIS21,22,23,24 utilizados en la actualidad emplean metilprednisolona en dosis de 30 mg/kg en bolo infundido en 15 minutos, seguido de una infusión en dosis de 5.4 mg/kg/hora. Dependiendo si el tiempo transcurrido desde la lesión es menor a 3 horas la infusión se mantiene por 23 horas y si la lesión se encuentra entre 3 y 8 horas se mantiene por 47 horas. Del mismo modo se han utilizado TRH26, Gaciclidina, Naloxona22, Tirilizad24, Nimodipino25 y más recientemente se ha propuesto el tratamiento de células madres27,28. Por otra parte una serie de trabajos11 sugieren que la descompresión y estabilización precoz en TRM disminuye el daño medular así como las complicaciones médicas...

Spinal Cord Injury (SCI) is due to traumatic lesions involving spine, specially spinal cord and its roots. This is a catastrophic neurological disorder for the patients which are usually young people in productive age. The incidente range is from 11.5 to 53.4 per million people. Besides the great social problem it brings another important issue for health systems due to high costs involved. Different pharmacologic protocols have been proposed to avoid a possible further damage, without results supporting their use. Otherwise multiple studies suggest that early spine decompression and stabilization diminish secondary spinal cord damage as well as medical complications and period of hospitalization. Our study retrospectively evaluated a group of patients who received a late decompression and stabilization and one that received an early within the first 72 hours focusing in pre and post surgical stay and associated medical complications. The data were obtained of the Neurosurgical Department of The Rancagua Regional Hospital database and includes 233 patients with spinal cord injury between May 1997 and October 2009. Cervical Spinal Cord Injury is more prevalent and more common in middle age men. Patients who underwent early decompression were hospitalized less time and suffer less medical complications.

Tyrosyl-DNA phosphodiesterase 1 targeting for modulation of camptothecin-based treatment.

The targeting of specific DNA repair mechanisms may be a promising strategy to improve the efficacy of antitumor therapy. The cytotoxic effects of the clinically relevant topoisomerase 1 (Top1) poison camptothecins are related to the generation of DNA lesions and tumor cells may be resistant to DNA damaging agents due to increased repair. Tyrosyl- DNA phosphodiesterase 1 (TDP1) is implicated in the repair of strand breaks by removing abortive Top1/DNA complexes. Thus, a role for TDP1 in counteracting DNA damage induced by camptothecins has been proposed. Here, we review the role of TDP1 in DNA repair with particular reference to TDP1 function, its cooperation with other pathways and the development of pharmacological inhibitors.

ABC transporters as potential targets for modulation of drug resistance.

ATP binding cassette transporters are implicated in multidrug resistant phenotypes of tumor cells and may be cancer stem cell markers. Inhibitors of drug efflux pumps represent an emerging group of potentially useful agents for the improvement of antitumor therapy. Here we provide an overview of drug transporter functions and modulation.

Small molecules targeting p53 to improve antitumor therapy.

Small molecules targeting p53 represent an emerging group of potentially useful agents for the improvement of antitumor therapy. These modulators include agents that activate wild-type p53 or reactivate mutant p53 and inhibitors of p53 functions. Preclinical evidences support the interest of combination strategies with conventional antitumor agents.

Antitumor activity of the combination of synthetic retinoid ST1926 and cisplatin in ovarian carcinoma models.

BACKGROUND: The novel adamantyl retinoid ST1926 is a potent inducer of apoptosis in ovarian carcinoma cells. Since the pro-apoptotic effect is associated with activation of p53, in this study we have investigated the efficacy of combination of ST1926 with cisplatin, a DNA-damaging agent that is known to induce p53-dependent apoptosis. MATERIALS AND METHODS: The efficacy of ST1926 and its combination with cisplatin was evaluated in human ovarian carcinoma models, including resistant tumors. RESULTS: Oral treatment with ST1926 alone caused a marginal tumor growth inhibition (<50%), but the combination with cisplatin resulted in an improved efficacy, most evident in terms of tumor growth delay without a substantial increase of toxicity. The combination therapy achieved the best effects against the HOC18 ovarian carcinoma tumor, resulting in an appreciable number of animals without evidence of disease at the end of the experiment. In contrast to the marginal effect of ST1926 alone against the subcutaneous-growing tumors, loco-regional (intraperitoneal) treatment achieved a marked increase of survival of animals with ascitic IGROV-1 tumor. CONCLUSIONS: The present results document the efficacy of the combination of cisplatin with ST1926 and provide a rational basis for the design of novel, well-tolerated platinum-based treatment approaches in human ovarian carcinoma.

Mechanisms of cellular resistance to camptothecins.

The camptothecins are among the most promising antitumor agents endowed with a unique mechanism of action, because they act through inhibition of DNA topoisomerase I, an enzyme involved in regulating critical cellular functions including DNA replication, transcription and recombination. On the basis of the pharmacological interest of camptothecins in cancer chemotherapy, medicinal chemistry has played a crucial role in the development of novel analogs, and recently some compounds have emerged as promising agents for clinical evaluation. A major limitation to the clinical efficacy of camptothecin-containing therapies is represented by drug resistance. As with other cytotoxic drugs, clinical resistance to camptothecins may be a multifactorial phenomenon likely involving pharmacological and tumor-related factors. An additional problem in understanding clinically relevant resistance mechanisms is the observation that preclinical cell/tumor models may be not adequately predictive of clinical resistance. Here, we review the mechanisms of cell sensitivity/resistance to camptothecins and current approaches to overcome specific mechanisms, either by chemical modifications or by combination with modulating agents. In particular, the realization that most camptothecins are substrates for ATP binding cassette transporters has stimulated efforts in molecular design of novel non-cross-resistant analogs. Finally, a better understanding of the mechanism of cell response at a cellular level could help in defining new strategies to overcome resistance as well as chemical features required for efficacy.

Cellular sensitivity to beta-diketonato complexes of ruthenium(III), chromium(III) and rhodium(III).

The aim of this study was to investigate cellular response to several ruthenium(III), chromium(III) and rhodium(III) compounds carrying bidentate beta-diketonato ligands: [(acac)--acetylacetonate ligand, (tfac)--trifluoroacetylacetonate ligand]. Cell sensitivity studies were performed on several cell lines (A2780, cisplatin-sensitive and -resistant U2-OS and U2-OS/Pt, HeLa, B16) using growth-inhibition assay. Effect of intracellular GSH depletion on cell sensitivity to the agents was analyzed in A2780 cells. Flow cytometry was used to assess apoptosis by Annexin-V-FITC/PI staining, and to analyze induction of caspase-3 activity. Possible DNA binding/damaging affinity was investigated, by inductively coupled mass spectrometry, and by 14C-thymidine / 3H-uridine incorporation assay. Cell sensitivity studies showed that the pattern of sensitivity to Ru(tfac)3 complex of the two cisplatin-sensitive/-resistant osteosarcoma cell lines, U2-OS and U2-OS/Pt, was similar to that of A2780 cells (72 h exposure), with the IC50 being around 40 microM. The growth-inhibitory effect of Ru(acac)3 ranged over 100 microM, while Cr(III) and Rh(III) complexes were completely devoid of antitumor action in vitro. Ru(tfac)3 exhibited strong potential for apoptosis induction on A2780 cells (up to 40%) and caused cell cycle arrest in the S phase as well as decrease of the percent of G1 and G2 cells. Ru(acac)3-induced apoptosis was slightly higher than 10%, whereas activation of caspase-3 in HeLa cells was moderate. DNA binding study revealed that only Cr(acac)3 was capable of binding DNA, while Cr(III) and Ru(III) compounds possess potential to inhibit DNA/RNA synthesis. In conclusion, only Ru(III) complexes showed potential for antitumor action.

Expression of gamma-glutamyltransferase in cancer cells and its significance in drug resistance.

The expression of gamma-glutamyltransferase (GGT), a cell surface enzyme involved in cellular glutathione homeostasis, is often significantly increased in human tumors, and its role in tumor progression, invasion and drug resistance has been repeatedly suggested. As GGT participates in the metabolism of cellular glutathione, its activity has been mostly regarded as a factor in reconsitution of cellular antioxidant/antitoxic defences. On this basis, an involvement of GGT expression in resistance of cancer cells to cytotoxic drugs (in particular, cisplatin and other electrophilic agents) has been envisaged. Mechanistic aspects of GGT involvement in antitumor pharmacology deserve however further investigations. Recent evidence points to a more complex role of GGT in modulation of redox equilibria, with effects acting both intracellularly and in the extracellular microenvironment. Indications exist that the protective effects of GGT may be independent of intracellular glutathione, and derive rather from processes taking place at extracellular level and involving reactions of electrophilic drugs with thiol metabolites originating from GGT-mediated cleavage of extracellular glutathione. Although expression of GGT cannot be regarded as a general mechanism of resistance, the involvement of this enzyme in modulation of redox metabolism is expected to have impact in cellular response to several cytotoxic agents. The present commentary is a survey of data concerning the role of GGT in tumor cell biology and the mechanisms of its potential involvement in tumor drug resistance.

p53 Gene status and response to topotecan-containing chemotherapy in advanced ovarian carcinoma.

OBJECTIVE: Since the p53 gene has been identified as a determinant of response to chemotherapy in ovarian carcinoma in previous studies, we investigated the significance of the p53 status in response to topotecan as second-line therapy. METHODS: Twenty-eight patients with advanced ovarian carcinoma, pretreated with standard platinum/paclitaxel chemotherapy, received topotecan as single-agent second-line therapy. Tumors were investigated by molecular analysis for p53 mutations in tumor samples obtained at primary surgery (i.e. before first-line therapy). RESULTS: Wild-type p53 tumors responsive to first-line therapy maintained substantial responsiveness to topotecan. In contrast, p53 mutation was associated with a low responsiveness to second-line therapy. CONCLUSIONS: The better outcome in relapsed patients with wild-type p53 suggests that the presence of a functional wild-type p53 confers stability of the drug-sensitive phenotype. This outcome is consistent with the clinical observation that the efficacy of topotecan in the treatment of relapsed ovarian carcinoma patients is dependent on platinum sensitivity, because platinum-sensitive tumors are expected to carry wild-type p53. Although untreated mutant p53 tumors may be responsive to first-line paclitaxel-containing therapy, it is likely that loss of p53 leads to genomic instability resulting in rapid progression to drug resistance.

Global gene expression of fission yeast in response to cisplatin.

The cellular response to the antitumor drug cisplatin is complex, and resistance is widespread. To gain insights into the global transcriptional response and mechanisms of resistance, we used microarrays to examine the fission yeast cell response to cisplatin. In two isogenic strains with differing drug sensitivity, cisplatin activated a stress response involving glutathione-S-transferase, heat shock, and recombinational repair genes. Genes required for proteasome-mediated protein degradation were up-regulated in the sensitive strain, whereas genes for DNA damage recognition/repair and for mitotic progression were induced in the resistant strain. The response to cisplatin overlaps in part with the responses to cadmium and the DNA-damaging agent methylmethane sulfonate. The different gene groups involved in the cellular response to cisplatin help the cells to tolerate and repair DNA damage and to overcome cell cycle blocks. These findings are discussed with respect to known cisplatin response pathways in human cells.

Antitumour and antiangiogenic effects of IDN 5390, a novel C-seco taxane, in a paclitaxel-resistant human ovarian tumour xenograft.

IDN 5390 is a novel C-seco taxane analogue selected for preclinical development on the basis of its antimotility activity on endothelial cells, antitumour efficacy in a large panel of human tumour xenografts and high tolerability in mouse. On the basis of oral availability, IDN 5390 is suitable for protracted administration schedules. Such a treatment schedule has been reported as the most appropriate to exploit the antiangiogenic effects of cytotoxic drugs. An ability to downregulate angiogenesis-related growth factors in tumour cells has been described for IDN 5390. The aim of the study was to investigate the antitumour and antiangiogenic potential of oral IDN 5390 on a human ovarian carcinoma xenograft, the INT.ACP/PTX, resistant to paclitaxel (PTX). Such tumour line was derived in vivo from a cisplatin-resistant tumour line, the A2780/DDP, which is sensitive to PTX. Compared to the parental cells, INT.ACP/PTX cells exhibited a high level of Pgp expression, resulting in a reduced in vitro sensitivity to both PTX and IDN 5390. The INT.ACP/PTX tumour xenograft was still resistant to PTX, but responsive to IDN 5390, when delivered per os, by a daily prolonged schedule. A direct effect on tumour cells, allowed by the high tolerability of the compound in mouse, cannot be excluded in vivo. Immunohistochemical analysis indicated a significant reduction of microvessel density in IDN 5390-treated tumours, lasting till 7 days after the last drug administration. Thus, a prolonged inhibitory effect on tumour angiogenesis is consistent with the persistent growth control of INT.ACP/PTX tumour achieved by IDN 5390. On the contrary, the low tolerability and the limited oral availability of conventional taxanes do not allow an easy feasibility of such treatment regimen. Thus, the tolerability profile of IDN 5390 in preclinical systems and its efficacy in PTX-resistant tumours support the therapeutic interest for its clinical development, with particular attention to oral daily prolonged schedules.

Gene expression profiles in the cellular response to a multinuclear platinum complex.

We used cDNA arrays to monitor modulation of mRNA expression after exposure to a multinuclear platinum complex (BBR3464) in a human cervix squamous cell carcinoma cell line (A431) and in a cisplatin-resistant subline (A431/Pt) exhibiting collateral sensitivity to BBR3464. In parental A431cells, the drug induced at least twofold up-regulation of 15 genes including cell cycle and growth regulators, tumor suppressors and signal transduction genes. In cisplatin-resistant A431/Pt cells, BBR3464increased the expression of 15 genes such as apoptosis regulators and genes involved in the DNA damage response. Interestingly, BBR3464induced up-regulation of anti-metastatic factors together with down-regulation of several pro-metastatic factors. Cell cycle analysis indicated a marked G2arrest in treated A431cells, whereas an apoptotic response was documented in A431/Pt cells. These differential patterns of transcriptional profile in sensitive and resistant cells are consistent with a role for cell cycle regulation in the response to BBR3464.

Induction of apoptosis and stress response in ovarian carcinoma cell lines treated with ST1926, an atypical retinoid.

To understand the molecular mechanisms mediating apoptosis induction by a novel atypical retinoid, ST1926, the cellular response to drug treatment was investigated in IGROV-1 ovarian carcinoma cells carrying wild-type p53 and a cisplatin-resistant p53 mutant subline (IGROV-1/Pt1). Despite a similar extent of drug-induced DNA strand breaks, the level of apoptosis was substantially higher in p53 wild-type cells. p53 activation and early upregulation of p53-target genes were consistent with p53-dependent apoptosis in IGROV-1 cells. Stress-activated protein kinases were activated in both cell lines in response to ST1926. This event and activation of AP-1 were more pronounced in IGROV-1/Pt1 cells, in which the modulation of DNA repair-associated genes suggests an increased ability to repair DNA damage. Inhibition of JNK or p38 stimulated ST1926-induced apoptosis only in IGROV-1 cells, whereas inhibition of ERKs enhanced apoptosis in both the cell lines. Such a pattern of cellular response and modulation of genes implicated in DNA damage response supports that the genotoxic stress is a critical event mediating drug-induced apoptosis. The results are consistent with apoptosis induction through p53-dependent and -independent pathways, regulated by MAP kinases, which likely play a protective role.

Endogenous oxidative stress induces distinct redox forms of tumor necrosis factor receptor-1 in melanoma cells.

Receptors of the TNFR superfamily possess abundant thiols in their extracellular domains, which makes them susceptible to redox modulation by prooxidant agents and processes. Previous studies from our laboratory have documented that membrane gamma-glutamyltransferase (GGT) activity can originate reactive oxygen species in the extracellular milieu, during the GGT-mediated metabolism of extracellular glutathione. The present study was aimed thus to verify a possible redox-modulating effect of GGT activity on TNFR1 receptors. The thiol-specific probe maleimide-polyethylene glycol was used to selectively label the reduced thiol groups in proteins of cell lysates; fractions corresponding to TNFR1 were then identified by immunoblot. In human melanoma Me665/2 cells, expressing varying GGT levels, at least five distinct forms of TNFR1 have been thus identified. The more oxidized forms appear to be prevalent in the 2/60 clone, expressing higher GGT levels, as compared to clone 2/21. Stimulation of GGT activity in the latter induced an increase of the oxidized TNFR1 forms. It is conceivable that different redox states of TNFR1 may correspond to different binding affinity and/or changes in the transducing function of the receptor. As GGT is frequently expressed by malignant tumors, the described phenomena might concur to alter the sensitivity of cancer cells to agents targeted on activation of TNF-alpha-dependent signaling pathways.

Cellular and pharmacological bases of the antitumor activity of a novel adamantyl retinoid, ST1926.

ST1926 is a novel related adamantyl retinoid endowed with potent antiproliferative and apoptogenic activity. The drug induced an early G1/S cell cycle arrest which was associated with a typical DNA damage response including modulation of genes involved in cell cycle regulation and DNA repair. The evidence of the drug ability to induce a significant extent of DNA strand breaks after short-term exposure is consistent with the cellular response. ST1926 is active by oral administration both on hematological and on solid tumors. The more marked antitumor effect showed by ST1926 in immuno-competent mice rather than in tumor xenografts suggests a contribution of indirect host-mediated antitumor effects in addition to a direct antiproliferative activity against tumor cells.

Inactivation of Ret/Ptc1 oncoprotein and inhibition of papillary thyroid carcinoma cell proliferation by indolinone RPI-1.

Genetic alterations causing oncogenic activation of the RET gene are recognized as pathogenic events in papillary and medullary thyroid carcinomas. Inhibition of Ret oncoprotein functions could thereby represent a specific therapeutic approach. We previously described the inhibitory activity of the 2-indolinone derivative RPI-1 (formerly Cpdl) on the tyrosine kinase activity and transforming ability of the products of the RET/PTC1 oncogene exogenously expressed in murine cells. In the present study, we investigated the effects of RPI-1 in the human papillary thyroid carcinoma cell line TPC-1 spontaneously harboring the RET/PTC1 rearrangement. Treatment with RPI-1 inhibited cell proliferation and induced accumulation of cells at the G2 cell cycle phase. In treated cells, Ret/Ptc1 tyrosine phosphorylation was abolished along with its binding to Shc and phospholipase C(gamma), thereby indicating abrogation of constitutive signaling mediated by the oncoprotein. Activation of JNK2 and AKT was abolished, thus supporting the drug inhibitory efficacy on downstream pathways. In addition, cell growth inhibition was associated with a reduction in telomerase activity by nearly 85%. These findings in a cellular context relevant to the pathological function of RET oncogenes support the role of Ret oncoproteins as useful targets for therapeutic intervention, and suggest RPI-1 as a promising candidate for preclinical development in the treatment of thyroid tumors expressing RET oncogenes.

gamma-Glutamyl transpeptidase catalyses the extracellular detoxification of cisplatin in a human cell line derived from the proximal convoluted tubule of the kidney.

Nephrotoxicity is a side-effect and the main factor limiting the clinical use of cisplatin. In vivo, the administration of the cysteine-containing tripeptide glutathione (GSH) has been found to reduce nephrotoxicity, but the biochemical mechanism of this protective action is not fully understood. The present study was designed to gain insights into the mechanism by which GSH prevents cisplatin nephrotoxicity. We also wanted to verify the hypothesis of whether the protective action of GSH is mediated by products of the extracellular breakdown of GSH catalysed by gamma-glutamyl transpeptidase (GGT), an enzyme that is highly expressed in kidney tubular cells. The study was performed in HK-2 cells, derived from the immortalisation of human kidney proximal tubule cells. We investigated the influence of modulators of GGT activity and/or thiols on the antiproliferative activity of cisplatin and on the intracellular GSH content. We determined the antiproliferative activity of cisplatin, platinum cellular accumulation and DNA platination following precomplexing of the drug with thiols. The antiproliferative effect of cisplatin was minimally affected by the addition of GSH. However, when the antiproliferative assay was performed in the presence of glycyl-glycine (GlyGly), to serve as a transpeptidation acceptor and thus to stimulate GGT-mediated GSH catabolism, cisplatin-induced growth inhibition was largely prevented. This effect was not mediated through an increase of intracellular GSH levels, which were not affected by the GlyGly supplementation. The thiol dipeptide cysteinyl-glycine, i.e. the GSH catabolite generated by GGT activity, showed a higher reactivity against cisplatin in vitro than GSH, as was shown by the more rapid oxidation of its -SH groups. The cisplatin/GSH or cisplatin/cysteinyl-glycine adducts did not display an antiproliferative effect. However, 2 h precomplexing with GSH in the presence of GGT, or directly with the GSH catabolite cysteinyl-glycine, decreased the antiproliferative effect of cisplatin and drug-induced DNA platination to a greater extent than precomplexing with GSH alone. The results of the present study show that, in HK-2 cells, extracellular GSH decreases the antiproliferative effects of cisplatin only upon its hydrolysis by GGT, thereby supporting the hypothesis that the extracellular metabolism of GSH by GGT plays a role in modulating cisplatin nephrotoxicity. A primary role in the protection of HK-2 cells appears to be played by cysteinyl-glycine, the proximal product of the GGT-mediated hydrolysis of GSH, which shows a high reactivity against CDDP resulting in the rapid inactivation of the drug.

IDN 5390: an oral taxane candidate for protracted treatment schedules.

The recognition of the antiangiogenic properties of taxanes provides a basis for novel therapeutic approaches. A prolonged exposure to low drug concentrations has been proposed to be the most suitable approach to exploit the antiangiogenic potential of cytotoxic agents. Such schedule is required to target preferentially slowly dividing endothelial cells. The protracted use of taxanes could benefit from the availability of a taxane endowed with a favourable tolerability profile. Among compounds of a novel series of C-seco taxanes, IDN 5390 was originally selected on the basis of its potent antimotility activity and poor cytotoxicity on endothelial cells. The aim of the study was to investigate the preclinical pharmacologic profile of IDN 5390 in a variety of human tumour xenografts, including ovarian and colon carcinoma and a glioblastoma. IDN 5390, delivered by s.c. injection, daily for 5 days per week, exhibited a high activity against all tumours investigated (tumour growth inhibition was always >85%) in the range of well-tolerated doses. The maximum tolerated dose/injection (MTD), with no signs of systemic or local vesicant toxicity, was 120 mg kg(-1). In contrast, paclitaxel, delivered according to the same schedule, exhibited a variable antitumour efficacy associated with a substantial local toxicity (MTD=10 mg kg(-1)). Considering the remarkable efficacy of IDN 5390 delivered s.c. by protracted treatment schedule, the oral route of administration was further investigated, as the most suitable for daily treatment. Indeed, a good bioavailability of oral IDN 5390 was found. Oral IDN 5390 maintained a substantial efficacy against human tumour xenografts, including paclitaxel-resistant tumours, without loss of potency with respect to s.c. administration. In conclusion, the therapeutic advantages of IDN 5390, over paclitaxel, in protracted daily treatment schedules are represented by the oral efficacy and the high tolerability, which are favourable features to exploit the antiangiogenic potential and to design combinations with other effective agents.