Design, synthesis and biological evaluation of novel dimeric and tetrameric cRGD-paclitaxel conjugates for integrin-assisted drug delivery.

Integrins are associated with tumour cell survival and progression, and their expression has been shown to be increased in tumours. Thus, four novel conjugates of the tripeptide integrin ligand Arg-Gly-Asp (RGD) and the cytotoxic agent paclitaxel (cRGD-PTX) were prepared to investigate the potential of the multivalent presentation of the RGD moiety in improving the antitumor efficacy of PTX by tumour targeting. PTX was conjugated to two or four integrin recognizing ligands. The influence of multivalent presentation on in vitro αvß3-receptor affinity was confirmed. For all the conjugates compared to the previously synthesized monovalent counterparts, an enhancement of the binding strength was observed; this behaviour was more pronounced when considering the tetravalent presented RGD-conjugate. Cell growth inhibition assays on a panel of human tumour cell lines showed remarkable cytotoxic activity for all conjugates with IC50 values in a nanomolar range. Among the four conjugates, the bivalent derivative 3b was selected for in vivo studies in an ovarian carcinoma cell model xenografted in immunodeficient mice. A marked antitumor activity was observed, similar to that of PTX, but with a much more favourable toxicity profile. Overall, the novel cRGD-PTX conjugates disclosed here represent promising candidates for further advancement in the domain of targeted anti-tumour therapy.

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.

Doxorubicin disaccharide analogue: apoptosis-related improvement of efficacy in vivo.

BACKGROUND: Although doxorubicin remains one of the most effective agents for the treatment of solid tumors, there is an intensive effort to synthesize doxorubicin analogues (compounds with similar chemical structures) that may have improved antitumor properties. We have synthesized a novel doxorubicin disaccharide analogue (MEN 10755) and have characterized some of its relevant biochemical, biologic, and pharmacologic properties. METHODS: The antitumor activity of this compound (MEN 10755) was studied in a panel of human tumor xenografts, including xenografts of A2780 ovarian tumor cells, MX-1 breast carcinoma cells, and POVD small-cell lung cancer cells. MEN 10755 was compared with doxorubicin according to the optimal dose and schedule for each drug. The drug's cytotoxic effects, induction of DNA damage, and intracellular accumulation were studied in A2780 cells. DNA cleavage mediated by the enzyme topoisomerase II was investigated in vitro by incubating fragments of simian virus 40 DNA with the purified enzyme at various drug concentrations and analyzing the DNA cleavage-intensity patterns. Drug-induced apoptosis (programmed cell death) in tumors was determined with the use of MX-1 and POVD tumor-bearing athymic Swiss nude mice. RESULTS: MEN 10755 was more effective than doxorubicin as a topoisomerase II poison and stimulated DNA fragmentation at lower intracellular concentrations. In addition, MEN 10755 exhibited striking antitumor activity in the treatment of human tumor xenografts, including those of the doxorubicin-resistant breast carcinoma cell line MX-1. CONCLUSIONS: The high antitumor activity of MEN 10755 in human tumor xenografts, including doxorubicin-resistant xenografts, and its unique pharmacologic and biologic properties make this disaccharide analogue a promising candidate for clinical evaluation.

A novel 7-modified camptothecin analog overcomes breast cancer resistance protein-associated resistance in a mitoxantrone-selected colon carcinoma cell line.

We selected a mitoxantrone-resistant HT29 colon carcinoma cell line (HT29/MIT) that exhibited a very high degree of resistance to the selecting agent and marked resistance to topotecan and SN38, but limited resistance to doxorubicin. The development of drug resistance was independent of expression of P-glycoprotein or multidrug resistance-associated protein but was associated with high up-regulation of the breast carcinoma resistance protein (BCRP) as shown by Western blot analysis. BCRP overexpression was associated with a reduced intracellular accumulation of topotecan, a known substrate for BCRP. Conversely, a lipophilic 7-modified camptothecin analogue (ST1481) displayed a complete lack of cross-resistance in HT29/MIT cells, suggesting that the drug was not a substrate for BCRP because no defects in intracellular accumulation were found. This conclusion is consistent with the antitumor efficacy of ST1481 against a BCRP-expressing tumor. These results may have therapeutic implications because the antitumor efficacy of ST1481 is in part related to a good bioavailability after oral administration, and the drug is currently under Phase I clinical evaluation.

Potent antitumor activity and improved pharmacological profile of ST1481, a novel 7-substituted camptothecin.

Relevant drawbacks of the molecular structure and mechanism of the action of camptothecins are the instability of the E ring lactone and the reversibility of drug-target interaction. Such features are expected to limit the clinical efficacy of conventional camptothecins. In an attempt to overcome these limitations and to improve the pharmacological profile of camptothecins, a novel series of seven modified lipophilic analogues was synthesized based on the hypothesis that lipophilicity could promote a rapid cellular accumulation and stabilization of drug-target interaction. A novel analogue (ST1481) of the series, characterized by a potent antitopoisomerase and cytotoxic activity, was selected for preclinical development. A detailed preclinical study of ST1481 was performed in the H460 non-small cell lung tumor model using oral administration and various treatment schedules. Under all of the conditions, ST1481 exhibited an impressive efficacy in terms of tumor growth inhibition (tumor volume inhibition percentage > 99%), log(10) cell kill, rate of complete responses (including "cures"), and an improvement of the therapeutic index compared with topotecan (used as the reference drug). The cytotoxic potency was also reflected by the in vivo potency, because the drug activity was observed at doses as low as 0.25 mg/kg with the daily schedule. In contrast to topotecan, no cross-resistance to ST1481 was found in ovarian carcinoma cells overexpressing P-glycoprotein (A2780/DX). A similar trend in the improvement of activity was also observed in the same tumor model growing in vivo with a 100% rate of complete tumor regressions. A rapid intestinal absorption and good oral bioavailability were supported by in vivo distribution studies, because the peak values of drug accumulation were found from 1 to 2 h after administration. The relevant liver accumulation may account for a marked effect of ST1481 against liver metastases induced by the ovarian carcinoma IGROV-1. In conclusion, the results support the hypothesis that a potent lipophilic camptothecin with a proper substituent at the position 7 may have therapeutic advantages likely related to a rapid intracellular uptake and tissue distribution, stabilization of the drug-target complex, and good oral bioavailability. Overall, the results support the preclinical interest of ST1481 in terms of efficacy, potency, toxicity profile, and ability to overcome multidrug resistance.

(236)U and (239,)(240)Pu ratios from soils around an Australian nuclear weapons test site.

The isotopes (236)U, (239)Pu and (240)Pu are present in surface soils as a result of global fallout from nuclear weapons tests carried out in the 1950's and 1960's. These isotopes potentially constitute artificial tracers of recent soil erosion and sediment movement. Only Accelerator Mass Spectrometry has the requisite sensitivity to measure all three isotopes at these environmental levels. Coupled with its relatively high throughput capabilities, this makes it feasible to conduct studies of erosion across the geographical extent of the Australian continent. In the Australian context, however, global fallout is not the only source of these isotopes. As part of its weapons development program the United Kingdom carried out a series of atmospheric and surface nuclear weapons tests at Maralinga, South Australia in 1956 and 1957. The tests have made a significant contribution to the Pu isotopic abundances present in the region around Maralinga and out to distances ∼1000 km, and impact on the assessment techniques used in the soil and sediment tracer studies. Quantification of the relative fallout contribution derived from detonations at Maralinga is complicated owing to significant contamination around the test site from numerous nuclear weapons safety trials that were also carried out around the site. We show that (236)U can provide new information on the component of the fallout that is derived from the local nuclear weapons tests, and highlight the potential of (236)U as a new fallout tracer.

Improved efficacy and enlarged spectrum of activity of a novel anthracycline disaccharide analogue of doxorubicin against human tumor xenografts.

On the basis of a structure-activity study of a new series of anthracycline disaccharides, we recently identified a doxorubicin analogue (MEN 10755) with a promising antitumor activity. In the present study, to better support the pharmacological interest of MEN 10755, we extended the preclinical evaluation of antitumor efficacy to a large panel of 16 human tumor xenografts, which originated from different clinicopathological types. Tumors with typical multidrug-resistant phenotype were excluded because MEN 10755 was found unable to overcome resistance mediated by transport systems. In the doxorubicin-responsive series, MEN 10755 exhibited a higher activity in three of five tumors, as documented by a more marked tumor growth inhibition and an increased value of log-cell kill. In the series of doxorubicin-resistant tumors, MEN 10755 was found effective in 6 of 11 tumors (1 breast, 3 lung, and 2 prostate carcinomas). The overall response rates were 31% and 69% for doxorubicin and MEN 10755, respectively. The improvement in drug efficacy was also supported by a substantial increase in the long-term survivor rate of animals implanted with responsive tumors. Most of the tumors refractory to doxorubicin and responsive to MEN 10755 were characterized by overexpression of the antiapoptotic protein Bcl-2. In one of these tumors (MX-1 breast carcinoma), we examined the ability of MEN 10755 to induce phosphorylation of Bcl-2 after a single treatment with therapeutic doses. The results indicated that, unlike doxorubicin, MEN 10755 induced protein phosphorylation. A similar modification was produced by Taxol, which is known to be very effective against the tumor. The correlation between drug efficacy and Bcl-2 phosphorylation may underly a peculiar feature related to improvement of efficacy of the disaccharide analogue. In conclusion, the present study supports some favorable features of the novel doxorubicin analogue in terms of both efficacy and tolerability with comparison to doxorubicin, although the improvement is somewhat tumor- and schedule-dependent.

On the possibility of tree-level leptogenesis from Kalb-Ramond torsion background.

In this work we consider a phenomenological model for leptogenesis in the context of a Standard Model Extension with an axial-like background coupling to fermions that violates both Lorentz and CPT symmetries. The latter is motivated by a background geometry of the early Universe involving a particular kind of torsion, arising from the Kalb-Ramond antisymmetric tensor field which appears in the gravitational multiplet of string theory, although we do not restrict ourselves to this framework. It is shown that leptogenesis can occur even at tree level and with only one generation of right-handed heavy Majorana neutrinos, due to [Formula: see text] and CPT violation introduced by the background geometry. Important issues for the model, including (a) its compatibility with a conventional-like cosmology and (b) current-era phenomenology (characterised by very stringent bounds on the allowed amount of torsion) are pointed out, and potential ways of resolving them, within the framework of string-theory models, are discussed.

Uranium beam characterization at CIRCE for background and contamination determinations.

The Accelerator Mass Spectrometry (AMS) is the most sensitive technique, compared either to the Inductively Coupled Plasma (ICP-MS) or Thermal Ionization (TI-MS) mass spectrometer, for the actinide (e.g. (236)U, (x)Pu isotopes) measurements. They are present in environmental samples at the ultra trace level since atmospheric tests of Nuclear Weapons (NWs) performed in the past, deliberate dumping of nuclear waste, nuclear fuel reprocessing, on a large scale, and operation of Nuclear Power Plants (NPPs), on a small scale, have led to the release of a wide range of radioactive nuclides in the environment. At the Center for Isotopic Research on Cultural and Environmental heritage (CIRCE) in Caserta, Italy, an upgraded actinide AMS system, based on a 3-MV pelletron tandem accelerator, has been developed and routinely operated. At CIRCE a charge state distribution as a function of terminal voltage, the beam emittance, measured in the 20° actinides dedicated beam line, as well as the energy and position validation of the U ions were performed in order to determine the best measurement conditions. A (236)U/(238)U isotopic ratio background level of about 5×10(-12) or 3×10(-13), depending on the Time of Flight-Energy (TOF-E) configurations, as well as the spatial distribution of the (235)U, (238)U interferences ions and a (236)U contamination mass of about 0.5 fg have been determined.

Role of apoptosis and apoptosis-related genes in cellular response and antitumor efficacy of anthracyclines.

Cellular resistance to anthracyclines is a major limitation of their clinical use in the treatment of human tumors. Resistance to doxorubicin is described as a multifactorial phenomenon involving the overexpression of defense factors and alterations in drug-target interactions. Such changes do not account for all manifestations of drug resistance, in particular intrinsic resistance of solid tumors. Since anthracyclines can induce apoptotic cell death, an alternative promising approach to drug resistance has focused on the study of cellular response to drug-induced DNA damage, with particular reference to the relationship between cytotoxicity/antitumor efficacy and apoptotic response. The evidence that a novel disaccharide analog (MEN 10755), endowed with an improved preclinical activity over doxorubicin, was also more effective as an inducer of apoptosis provided additional insights to better understand the cellular processes that confer sensitivity to anthracyclines. Although the presence or alteration of a single apoptosis-related factor (e.g., p53, bcl-2) is not predictive of the sensitivity/resistance status, the complex interplay among DNA damage-activated pathways is likely an important determinant of tumor cell sensitivity to anthracyclines

Efficacy and toxicity profile of oral topotecan in a panel of human tumour xenografts.

On the basis of their mechanism of action (cell killing during DNA replication) and the potential reversibility of the drug effects, protracted therapy with camptothecins is reported to provide optimal antitumour effects. Furthermore, oral administration may be a useful modality for optimisation of treatment. The aim of this study was to compare the therapeutic profile of topotecan given orally or intravenously in human tumours xenografted into athymic nude mice. The drug topotecan was given according to an intermittent (every fourth day, four times) or daily (qdx5/weeklyx5-10 weeks; only orally) schedule. Tumour growth inhibition and persistence of drug effects were assessed and compared with untreated mice. In a panel of seven tumour xenografts, oral topotecan was at least as effective on three and significantly more effective on four tumours. Using the intermittent schedule, the maximum tolerated dose (MTD) was comparable for the two routes (15 mg/kg), but the toxicity profile suggested a better tolerability in terms of lethal effects after oral administration. The daily oral treatment of low drug doses allowed a higher cumulative dose to be delivered with improved antitumour efficacy (2/10 cured in a large cell lung cancer) and no evidence of toxicity. In spite of the low bioavailability of oral topotecan (23.5%), the persistent plasma levels of the drug suggest that the time of exposure to the drug is more critical than the plasma concentrations for antitumour efficacy. This interpretation is consistent with the increased efficacy of prolonged daily treatment with low-dose levels. The results may have implications for the future design of clinical studies.

Tissue distribution, antitumour activity and in vivo apoptosis induction by MEN10755 in nude mice.

MEN10755 is a disaccharide analogue of doxorubicin (DXR) endowed with a broader spectrum of activity compared with DXR in a panel of human tumour xenografts. In an attempt to investigate the pharmacological basis of the improvement of therapeutic efficacy of the analogue, a comparative pharmacokinetic (tissue and tumour distribution) and pharmacodynamic (antitumoral activity and ability to induce apoptosis) study of MEN10755 and DXR was performed in athymic nude mice bearing a human ovarian carcinoma xenograft (A2780). Drug level was quantified by high performance liquid chromatography (HPLC) with fluorimetric detection after a single intravenous (i.v.) injection of 7 mg/kg of MEN10755 or DXR. The results indicated a reduced accumulation of MEN10755 compared with DXR in all tissues investigated (tumour, heart, kidney and liver). The reduction was more marked in normal than tumour tissues. Moreover, in spite of the reduced drug uptake by tumour tissues, the new disaccharide anthracycline given in its optimal regimen showed an enhanced antitumour efficacy, compared with DXR. The drug effects on tumour growth paralleled a marked activation of apoptosis. In conclusion, the pattern of tissue distribution and the pharmacokinetic behaviour were consistent with a better tolerability of the novel analogue which allowed a higher cumulative dose to be delivered. The superior therapeutic efficacy of the analogue over DXR, in spite of a reduced tumour accumulation, supports an increased tumour selectivity.

Novel 7-substituted camptothecins with potent antitumor activity.

The natural alkaloid camptothecin is the lead compound of a new class of antitumor agents with a unique mechanism of action (i.e. inhibition of DNA topoisomerase I). The pharmacological interest of these agents has generated a large number of derivatives and analogues endowed with potent cytotoxic activity, two of them being in clinical use as antitumor drugs. We have synthesized a new series of camptothecins substituted in position 7 with an alkyl or alkenyl chain bearing cyano and/or carbethoxy groups. These compounds showed potent cytotoxic activity in vitro against the human non-small-cell lung carcinoma H460 cell line, most of them exhibiting IC(50) values in the 0.05-1 microM range, more active than topotecan used as a reference compound. In particular 7-cyano-20S-camptothecin (5a) showed high in vitro cytotoxicity against a topotecan-resistant H460 cell subline (H460/TPT) and a cisplatin-resistant ovarian carcinoma subline (IGROV-1/Pt 1). In an in vivo evaluation of the antitumor activity, 5a appeared significantly more effective than topotecan in the H460 tumor model and comparable with topotecan in a small-cell lung carcinoma model and a colon carcinoma model. The efficacy and good tolerability of this compound increase interest for further preclinical development.

8,11-dihydroxy-6-[(aminoalkyl)amino]-7H-benzo[e]perimidin-7-ones with activity in multidrug-resistant cell lines: synthesis and antitumor evaluation.

The synthesis of dihydroxybenzoperimidine derivatives, which are chromophore-modified dihydroxyanthracenediones with an additional pyrimidine ring incorporated into the chromophore, is reported. These derivatives are structurally related to the antitumor agent mitoxantrone. Their synthesis was carried out by the reaction of 6-amino-8,11-dihydroxy-7H-benzo[e]perimidin-7-one (5) or 6,8, 11-trihydroxy-7H-benzo[e]perimidin-7-one (10) with a number of respective (alkylamino)alkylamines. The dihydroxybenzoperimidine derivatives exhibited in vitro cytotoxic activity against murine leukemia L1210 and human leukemia HL60 cell lines comparable to that of mitoxantrone. These compounds also exhibited a range of in vitro activity against the human MDR-type resistant leukemia K562R cell line with the MDR phenotype. The most active compound of this series, namely 6a, exhibited potent in vitro cytotoxic activity against a panel of human cell lines. Furthermore, in contrast to both mitoxantrone and doxorubicin, it displayed little cross-resistance in cell lines characterized by a MDR phenotype. Cell cycle analysis in the sensitive HT-29 and mitoxantrone-resistant HT-29/Mx (not identified resistance mechanism) cell lines has revealed that both mitoxantrone and 6a induce a G2/M block. However, while the proportion of apoptotic cells after mitoxantrone treatment is similar for both sensitive and resistant cell lines, it is much lower for 6a. Compound 6a tested against P388 murine leukemia in vivo displayed a significant antitumor effect (%T/C 196 at an optimal dose of 10 mg/kg). The property of overcoming the cross-resistance was maintained also in in vivo efficacy studies, where no difference was observed in the antitumor activity of compound 6a against the A2780 human tumor xenograft and its MDR A2780/Dx subline. We conclude that benzoperimidines, if properly substituted, constitute a novel class of compounds that can overcome multidrug resistance.

Novel 7-oxyiminomethyl derivatives of camptothecin with potent in vitro and in vivo antitumor activity.

In an attempt to synthesize potential anticancer agents acting by inhibition of topoisomerase I (Topo I) a new series of oxyiminomethyl derivatives in position 7 of camptothecin (CPT) was prepared. The synthesis relied on the condensation of 20S-CPT-7-aldehyde or 20S-CPT-7-ketones with alkyl, aryl, heteroaryl, arylalkyl, and heteroarylalkyl O-substituted hydroxylamines. The compounds were tested for their cytotoxic activity in vitro against H460 non-small lung carcinoma cell line, the activity being for 24 out of 37 compounds in the 0.01-0.3 microM range. A QSAR analysis indicated that lipophilicity is the main parameter correlated with cytotoxicity. Investigation of the DNA-Topo I-drug cleavable complex showed a rough parallelism between cytotoxicity and inhibition of Topo I. Persistence of the DNA cleavage after NaCl-mediated disruption of the ternary complex suggests that for the most potent compounds, e.g., 15, the cytotoxicity was at least in part related to stabilization of the complex, as also supported by the persistence of the DNA-enzyme complex in drug-treated cells. The in vivo antitumor efficacy of the most potent analogue (15) was evaluated in direct comparison with topotecan using human lung tumor xenograft models. In the range of optimal doses (2-3 mg/kg), the improved efficacy of 15 was documented in terms of inhibition of tumor growth and rate of complete response.

Biodistribution of haematoporphyrin analogues in a lung carcinoma model.

In an attempt to identify novel compounds useful for the optimization of Photodynamic Therapy (PDT), the tissue localization of new synthetic porphyrins was compared with Photofrin II in nude mice xenografted with a human small cell lung cancer (POVD). Three haematoporphyrin analogues were selected for this study based on prior in vitro photosensitivity screening of a series of 15 such derivatives, as well as on the basis of improved localization in C6 gliomas in mice. Two of the porphyrins yielded better tumour:normal lung ratios than Photofrin II and, of these two, one (P13) is known to exhibit good photosensitization properties both in vitro and in vivo, and is therefore a good candidate as a lead compound for the development of porphyrins suitable for the photodynamic treatment of lung tumours.

Configurational requirements of the sugar moiety for the pharmacological activity of anthracycline disaccharides.

The amino sugar is recognized to be a critical determinant of the activity of anthracycline monosaccharides related to doxorubicin and daunorubicin. In an attempt to improve the pharmacological properties of such agents, novel anthracycline disaccharides have been designed in which the amino sugar, daunosamine, is separated from the aglycone by another carbohydrate moiety. In the present study, we examined the influence of the orientation of the second sugar residue on drug biochemical and biological properties in a series of closely related analogs. This structure-activity relationship study showed that the substitution of the daunosamine for the disaccharide moiety dramatically reduced the cytotoxic potency of the drug in the 4-methoxy series (daunorubicin analogs). In contrast, in the 4-demethoxy series (idarubicin analogs), the C-4 axial, but not the equatorial, configuration conferred a cytotoxic potency and antitumor activity comparable to that of doxorubicin. The configuration also influenced the drug's ability to stimulate topoisomerase II alpha-mediated DNA cleavage. Indeed, the glycosides with the equatorial orientation were ineffective as topoisomerase II poisons, whereas the compounds with axial orientation were active, although the daunorubicin analog exhibited a lower activity than the idarubicin analog. It is conceivable that the axial orientation allows an optimal interaction of the drug with the DNA-enzyme complex only in the absence of the methoxy group. Our results are consistent with a critical role of the sugar moiety in drug interaction with the target enzyme in the ternary complex.

Characterization of an established human, malignant, glioblastoma cell line (GBM) and its response to conventional drugs.

A cell line, GBM, was established from a human malignant glioblastoma and was characterized with particular reference to its response to conventional drugs. The GBM cell line exhibited a 73 +/- 7 h doubling time in monolayer cultures. Expression of glial fibrillary acidic and S-100 proteins was observed. Karyotype analysis of GBM cells at early passages revealed the presence of two near-triploid clones (A and B) with multiple chromosome rearrangements; a 100% frequency for clone B was observed in the established cell line. GBM cells had tumorigenic properties, since the s.c. injection of cultured cells into nude mice gave rise to slowly growing tumors. The morphology of GBM cells was retained during in vitro and in vivo passages, as judged by light microscopy. GBM cells were relatively resistant to most conventional drugs; among the tested drugs, only taxol exhibited a marked cytotoxic effect comparable to that found in cells of a different tumor type. GBM cells were found positive for the epidermal growth factor receptor, HER2-neu and P-glycoprotein by flow cytometry of cells labelled with monoclonal antibodies. In spite of the expression of relatively high gamma-glutamyltransferase activity, the intracellular glutathione level was comparable to that of other chemosensitive tumor cells. This glioblastoma cell line is a suitable model for the identification and preclinical studies of new agents and provides an additional system to explore the molecular basis of the intrinsic drug resistance of glioblastoma.

Efficacy of lonidamine combined with different DNA-damaging agents in the treatment of the MX-1 tumor xenograft.

Lonidamine is an antitumor agent with a peculiar mechanism of action, since it differentially impairs the energy metabolism of normal and neoplastic cells. We investigated the effects of lonidamine on the activity of DNA-damaging antitumor agents against the MX-1 human breast carcinoma xenograft. Athymic mice bearing measurable s.c. tumors were treated by a single injection of doxorubicin (i.v.), cyclophosphamide (i.v.), or cisplatin (i.p.) followed by repeated daily injections of lonidamine (i.p. or p.o.). A potentiation of the activity of all these DNA-damaging drugs was achieved when each was given in combination with lonidamine, but for doxorubicin and cyclophosphamide the increase in antitumor activity paralleled the increase in lethal toxicity. In contrast, a therapeutic advantage of the combination was achieved for cisplatin and lonidamine as compared with cisplatin alone. Indeed, 6 mg/kg of cisplatin plus lonidamine cured all tumors, whereas the maximum tolerated dose of cisplatin alone (12 mg/kg) cured only six of eight tumors. In addition, the study indicated that the duration of lonidamine administration after injection of the cytotoxic drug influenced the tumor response and that prolonged treatment resulted in greater efficacy. These results document the ability of lonidamine to modulate the pharmacological activity of DNA-damaging drugs, thus suggesting that lonidamine may be a clinically useful cisplatin modulator.

Remarkable antitumor activity of 5'-deoxy-5-fluorouridine in human colorectal tumor xenografts.

5'-Deoxy-5-fluorouridine (doxifluridine) is a prodrug of 5-fluorouracil (5FU) selectively activated by tumor cells. Since in clinical studies the side effects of doxifluridine differed after intravenous (i.v.) or oral administration, and oral route was the most promising in preclinical studies with murine models, in this study the drug was tested orally against a panel of human colorectal tumor xenografts with varying degrees of sensitivity to 5FU. Doxifluridine efficacy was comparable to that of 5FU when it was delivered according to a weekly schedule, but it was statistically higher when it was delivered more frequently. Impressive tumor inhibition (between 90 and 97%) was achieved in 4 out of 5 tumor lines after treatments delivered twice a week or daily 5 times a week. No difference in 5FU activity was observed between weekly and biweekly treatments, or between oral and i.v. injections. Moreover, in one tumor line in which different dosages of doxifluridine were investigated, a marked antitumor effect was obtained with a wide range of tolerated doses (4000-8000 mg/kg). Overall, these data indicated that doxifluridine is well tolerated when given orally and frequently. Using an adequate schedule, the prodrug has a better therapeutic efficacy against a variety of human colon cancer models than 5FU.