New TRAP1 and Hsp90 chaperone inhibitors with cationic components: Preliminary studies on mitochondrial targeting.

TRAP1 (Hsp75) is the mitochondrial paralog of the Hsp90 molecular chaperone family. Due to structural similarity among Hsp90 chaperones, a potential strategy to induce apoptosis through mitochondrial TRAP1 ATPase inhibition has been envisaged and a series of compounds has been developed by binding the simple pharmacophoric core of known Hsp90 inhibitors with various appendages bearing a permanent cationic head, or a basic group highly ionizable at physiologic pH. Cationic appendages were selected as vehicles to deliver drugs to mitochondria. Indeed, masses of new derivatives were evidenced to accumulate in the mitochondrial fraction from colon carcinoma cells and a compound in the series, with a guanidine appendage, demonstrated good activity in inhibiting recombinant TRAP1 ATPase and cell growth and in inducing apoptotic cell death in colon carcinoma cells.

[Paraneoplastic neurological syndromes : A current summary]. / Paraneoplastische neurologische Syndrome : Eine aktuelle Zusammenfassung.

BACKGROUND: Paraneoplastic neurological syndromes (PNNS) are remote effects of a tumor and mediated by an altered immune reaction. In the last ten years, the spectrum of PNNS has changed profoundly with the discovery of a new category of neurological diseases that are associated with antibodies against surface or synaptic antigens. In contrast to classical PNNS, patients with surface receptor autoimmunity are often highly responsive to immunotherapy. OBJECTIVES: This article provides an update on the most relevant PNNS, focusing on specific syndromes associated with antibodies against classical onconeuronal antigens as well as surface and synaptic proteins. RESULTS: Classical PNNS are associated with antibodies against intracellular antigens (onconeuronal antibodies). They usually precede the tumor diagnosis and lead to the detection of the neoplasm. Affected patients are often older and have an unfavorable prognosis. Patients with surface receptor autoimmunity can have a similar presentation as classical PNNS; however, the disease is not necessarily triggered by a tumor and patients usually show a good response to treatment. Some surface receptor antibodies might manifest in highly characteristic syndromes and the resulting disease is named after the antibody, such as in anti-N-methyl-D-aspartate receptor (NMDAR) encephalitis. Other antibodies have considerable overlap in their clinical presentation and may be difficult to distinguish, such as in limbic encephalitis associated with GABA(B)R and α­amino-3-hydroxy-5-hydroxy-5-methyl-4-isoxazolpropionsäure receptor (AMPAR) antibodies. The diagnosis of the PNNS is important for an early recognition of a tumor and prompt initiation of treatment, which is associated with a better outcome of patients.

Drug resistance and apoptosis in cancer treatment: development of new apoptosis-inducing agents active in drug resistant malignancies.

Modulation of multidrug resistance (MDR) has been extensively studied in vitro and in vivo. However, several clinical trials have failed to show any important benefits in terms of response to chemotherapy or the length of survival using MDR reversing agents. This may be due to the expression or co-expression of other drug resistance mechanisms in malignant cells. Several studies have shown that most, if not all, chemotherapeutic agents exert their anticancer activity by inducing apoptosis; therefore, resistance to apoptosis may be a major factor limiting the effectiveness of anticancer therapy. In the last few years, effort has been made to understand the biochemical alterations of apoptotic pathways in cancer. Many of these alterations confer a multidrug resistant phenotype to malignant cells. In this context, the new recently developed anticancer therapies based on drugs that modulate apoptosis may have importance for the treatment of tumors that are scarcely responsive to the conventional anticancer chemotherapy. In this review, we discuss the current knowledge about drug resistance, apoptosis and cancer and report the recently developed apoptosis modulating strategies that have potential therapeutic implications for the drug resistant tumors.

Retinoids, apoptosis and cancer.

Retinoids are a class of natural and synthetic vitamin A analogs structurally related to all-trans-retinoic acid (ATRA). Natural retinoids are involved in the physiology of vision and as morphogenic agents during embryonic development; they are also known to play a major role in regulating growth and differentiation of a wide variety of normal and malignant cell types, and, indeed, they can in various ways inhibit cell proliferation, induce differentiation and cell death by apoptosis. The development of new active retinoids and the identification of two distinct families of retinoid receptors has led to an increased understanding of the cellular effects of activation of these receptors and of mechanisms involved in the retinoid-induced apoptosis. In this review a brief summary of cellular pathways relevant to programmed cell death is given together with therapeutic potentialities of retinoids having apoptotic activity. Structure-activity relationship studies concerning the importance of different stereochemistry at the C9 double bond of retinoids in conferring apoptotic activity will be described. It will be also described the preparation and the potent cytotoxic and apoptotic activity of a novel class of heterocycle-bridged arotinoids.

Apoptotic effects of thiazolobenzimidazole derivatives on sensitive and multidrug resistant leukaemic cells.

We investigated the cytotoxic activity of eight thiazolobenzimidazole derivatives on sensitive HL60 and multidrug-resistant (MDR) (HL60R) leukaemia cell lines. The antitumour effects of these compounds were compared with those of RS-TBZ, a thiazolobenzimidazole derivative, previously described in our reports, that was able to induce apoptosis more markedly in MDR cells than in the parental sensitive cell lines. Only two compounds in this study proved to have interesting effects: (a) the S-enantiomer of TBZ, that was able to induce apoptosis in MDR cells in a slightly more selective manner than TBZ (racemic form); and (b) TBZ-4-OCH3 (TBZ-4-OCH3), that showed cytotoxic and apoptotic effects on sensitive and resistant leukaemia cells greater than TBZ, without cytotoxic effects on normal haemopoietic progenitor cells. Moreover, we observed that TBZ-4-OCH3 was also active in cells expressing Bcr-Abl, an oncogene that confers resistance to apoptosis induced by several stimuli, including cytotoxic agents. The inhibition of caspase-9 and caspase-3 by specific polypeptide inhibitors decreased the apoptotic effects of TBZ-4-OCH3 in HL60 cells indicating that apoptosis induced by this compound was, at least partly, caspase-mediated. On the contrary, the blocking of FL-associated cell surface antigen (Fas) using a specific Fas-blocking monoclonal antibody did not affect the level of apoptosis induced by TBZ-4-OCH3 suggesting that the Fas pathway was not involved. In addition, the caspase 8 inhibitor was unable to inhibit the apoptotic activity of TBZ-4-OCH3. The very low toxicity shown by TBZ-4-OCH3 in normal haemopoietic progenitor cells and its high activity in sensitive and MDR neoplastic cells suggest a possible clinical use for this new compound.

Geiparvarin analogues. 4. Synthesis and cytostatic activity of geiparvarin analogues bearing a carbamate moiety or a furocoumarin fragment on the alkenyl side chain.

As a continuation of previous studies on the synthesis and antitumor activity of geiparvarin analogues bearing a carbamate moiety in the alkyl side chain, a series of N-substituted [(E)-3-(4,5-dihydro-5,5-dimethyl-4-oxo-2-furanyl)-2- butenyl]carbamates (15a-f) were synthesized and tested with the objective to investigate the reason for the marked difference of cytostatic activity found between alkyl and phenyl derivatives. A series of compounds, characterized by different physicochemical properties, were designed in order to study this hypothesis. Moreover, to further investigate the modification of the alkenyl side chain, (E)- and (Z)-[2-(4,5-dihydro-5,5-dimethyl-4-oxo-2-furanyl)propenyl]-7H-furo[3,2- g][1]benzopyran-7-one (11a,b) were synthesized, the latter compounds being the combination of two units, namely, the 3(2H)-furanone ring system endowed with potent alkylating properties and the furocoumarin portion which binds to DNA resulting in potential DNA-targeted alkylating agents. The compounds were tested for their cytostatic activity against proliferation of murine (L1210) and human (Molt/4, CEM, or MT-4) tumor cells. The highest cytostatic activity found within both series of carbamic derivatives (15a-d,k and 15e,g-j) was associated with the highest global lipophilicity. With regard to compounds 11a,b, the cytostatic activity of (Z)-furocoumarin 11b might be related to a specific interaction with DNA (i.e., intercalation).

Geiparvarin analogues. 3. Synthesis and cytostatic activity of 3(2H)-furanone and 4,5-dihydro-3(2H)-furanone congeners of geiparvarin, containing a geraniol-like fragment in the side chain.

Continuing our study on the structural features of geiparvarin (1), responsible for cytostatic activity, a series of 4,5-dihydro-3(2H)-furanones 10a-f and of 3(2H)-furanones 11a-f as well as 2",3"-dihydrogeiparvarin (14) have been designed and synthesized. Their cytostatic activity was evaluated against proliferation of murine (L1210, FM3A) and human (Raji, Molt/4F, and MT4) tumor cells. Modifications in the region of the olefinic double bond by introduction of the characteristic alkenyl side chain of ascofuranone (compounds 10a-f and 11a-f) markedly decreased the cytostatic activity as compared to geiparvarin itself, but this effect does not seem to be correlated to the presence of the furanone moiety linked to the alkenyl chain or to the ability to afford Michael type adducts. Replacement of the coumarin portion by other aromatic rings did not alter the cytostatic activity. The essential inactivity of 2",3"-dihydrogeiparvarin (14) points to the importance of the 3(2H)-furanone ring system in the cytostatic activity; consequently, this moiety may be considered as the determinant pharmacophore for antitumor activity, while the side chain plays a rather modulatory role.

Synthesis and cytostatic activity of geiparvarin analogues.

In an attempt to determine some of the structural features of geiparvarin (1) that account for its cytostatic activity in vitro, a series of geiparvarin analogues (4a-g) modified in the 3(2H)-furanone moiety have been designed and synthesized. The preparation of 4a-g was achieved through a new approach to the 3(2H)-furanone ring based on the elaboration of isoxazole derivatives. Among these synthetic analogues, 4b, the 5-methyl-5-ethyl derivative, proved as active as 1 in inhibiting the proliferation of murine and human tumor cell lines in vitro. As a rule, substitutions at the C5 atom of the 3(2H)-furanone moiety of 1 slightly decreased the cytostatic activity of geiparvarin. Several geiparvarin analogues described in this study (i.e. the 5-methyl-5-ethyl derivative 4b, 3(2H)-furanimine 4c, 5-methyl derivative 4f, and 5-ethyl derivative 4g) showed such activity in vitro and deserve further investigation for their antitumor potentials in vivo.

Synthesis and cytotoxic activity of 6-vinyl- and 6-ethynyluridine and 8-vinyl-and 8-ethynyladenosine.

It is well-known that the introduction of vinyl and ethynyl moieties into nucleosides is of crucial importance for cytostatic, antiviral, or other biological activities. In this study 6- and 8-vinyl-and -ethynyluridine and -adenosine were prepared by a general procedure involving the palladium-catalyzed cross-coupling of trimethylsilylacetylene or vinyltributyltin. The introduction of a vinyl group at C-6 of uridine or an ethynyl group at C-8 of adenosine resulted in nucleoside derivatives showing cytostatic activity against several murine and/or human tumor cell lines. Interestingly, 8-vinyladenosine had pronounced selective inhibitory effects on human (Molt/4F and MT-4) versus murine (L1210 and FM3A) tumor cell lines.

Synthesis and interaction of 5-(substituted-phenyl)-3-methyl-6,7-dihydropyrazolo[4,3-e] [1,4]diazepin-8(7H)-ones with benzodiazepine receptors in rat cerebral cortex.

On the basis of the anxiolytic property of ripazepam, 1-ethyl-4,6-dihydro-3- methyl-8-phenylpyrazolo[4,3-e][1,4]diazepin-5(1H)-one (1), a series of isomeric 5-(phenyl-substituted)pyrazolo[4,3-e][1,4] diazepin-8-ones 3a-f were prepared and tested for their ability to bind to the benzodiazepine receptor. All compounds 3a-f display affinities for the benzodiazepine receptor in the microM range of concentration; in particular 5-phenyl-3-methyl-6,7-dihydropyrazolo[4,3-e][1,4] diazepin-8(7H)-one (3a) is 2 orders of magnitude less potent in inhibiting [3H]flunitrazepam binding than diazepam and displays an affinity for the benzodiazepine receptor practically comparable to that of its structural isomer, ripazepam, and to that of chloriazepoxide.

Synthesis and prostaglandin-like activity of 2-(trans-3-hydroxy-1-octenyl)-3-indoleheptanoic acid.

The synthesis of 2-(trans-3-hydroxy-1-octenyl)-3-indoleheptanoic acid (1) is described. The title compound appeared to show a weak prostaglandin-like activity in two different systems. It contracted rat stomach fundus strips and guinea-pig ileum preparations only at concentrations about 10(3)- and 10(2)-fold higher, respectively, than PGE1. Moreover, it stimulated adenylate cyclase from rat liver plasma membrane, but the relative potency was 4--5 X 10(2)-fold lower than the natural compound. The title compound showed also a certain degree of PGE1 antagonism.

Geiparvarin analogues. 2. Synthesis and cytostatic activity of 5-(4-arylbutadienyl)-3(2H)-furanones and of N-substituted 3-(4-oxo-2-furanyl)-2-buten-2-yl carbamates.

In an attempt to determine some of the structural features of geiparvarin (1) that account for its cytostatic activity in vitro, a series of geiparvarin analogues (10a-i, 1, 12, and 14-16) which contain novel modifications in the region of the olefinic double bond and of the coumarin moiety have been designed and synthesized. Among the derivatives containing a carbamate moiety, only the analogues containing a carbamate group linked to an alkyl moiety 10b-i were endowed with potent cytostatic activity, whereas the corresponding benzene derivative 10a was devoid of any antiproliferative activity. 6-Methoxygeiparvarin 101 proved equally effective as geiparvin (1), while compounds containing an additional double bond at the side chain (12 and 14-16) were invariably 5-100-fold less effective than geiparvarin. Diene derivative 15, bearing a coumarin moiety, was essentially inactive against murine (L1210, FM3A) tumor cells but exhibited good activity against human (Molt/4F, MT-4) tumor cells.

Cholinergic agents structurally related to furtrethonium. 2. Synthesis and antimuscarinic activity of a series of N-[5-[(1'-substituted-acetoxy) methyl]-2-furfuryl]dialkylamines.

In the first part of this study, devoted to the discovery of selective antimuscarinic agents, (+/-)- N-[5-[(1'-phenyl-1'-cyclohexylacetoxy)methyl]-2-furfuryl]dimeth yla mine (5a) proved to be at least 20 times more potent in the rat ileum and bladder than in guinea pig atria. Several (+/-)-N- [5-[(1'-substituted-acetoxy)methyl]-2-furfuryl]dialkylamine analogs of 5a were subsequently prepared. This involved exploration of the tertiary nitrogen substituents and modulation of the lipophilic side chain at position 5 of the furan ring, using the Hansch approach. A QSAR study was conducted to correlate activity with physicochemical properties of substituents. The possibility of describing all compounds in a single model indicates that variations of nitrogen and the lipophilic side chain contribute independently to activity. Compounds 5b, c,j, with bulky lipophilic substituents at the tertiary nitrogen, showed unprecedented selectivity between the two smooth muscle tissues, their antimuscarinic potency being from 10 to 90 times higher in the ileum than in the bladder. It is suggested that their interesting tissue selectivity is probably related to nonspecific phenomena involving the receptor environment, rather than real differences between the muscarinic receptors in the two tissues.

Synthesis and antitumor activity of a new class of pyrazolo[4,3-e]pyrrolo[1,2-a][1,4]diazepinone analogues of pyrrolo[1,4][2,1-c]benzodiazepines.

A new class of pyrrolo[1,4]benzodiazepine (PBD) analogues featuring a pyrazolo[4,3-e]pyrrolo[1,2-a][1,4]diazepinone ring system has been designed and synthesized. These compounds, 2a-o, are characterized by the substitution of the aromatic A ring, characteristic of the PBDs, with a disubstituted pyrazole ring bearing alkyl and benzyl substituents at N6 or N7 and alkyl or carbomethoxy substituents at C8. Biological evaluation revealed an appreciable in vitro cytotoxic activity for compounds 2a,b,f-i.

Pyrazole-related nucleosides. Synthesis and antiviral/antitumor activity of some substituted pyrazole and pyrazolo[4,3-d]-1,2,3-triazin-4-one nucleosides.

Several pyrazole and pyrazolo[4,3-d]-1,2,3-triazin-4-one ribonucleosides were prepared and tested for antiviral/antitumor activities. Appropriate heterocyclic bases were prepared by standard methodologies. Glycosylation of pyrazoles 6a-e,g,i and of pyrazolo[4,3-d]-1,2,3-triazin-4-ones 12f-1 mediated by silylation with hexamethyldisilazane, with 1-beta-O-acetyl-2,3,5-tri-O-benzoyl-D-ribofuranose, gave in good yields the corresponding glycosides 7a-e,g, 8g,i, 13f,h,k, and 14f, but could not be applied to compounds 12g,i,j,l. To overcome this occurrence, a different strategy involving the preparation, diazotization, and in situ cyclization of opportune pyrazole glycosides 9 and 10 was required. Moreover derivatives having the general formula 5 were considered not only as synthetic intermediates in the synthesis of 3 but also as carbon bioisosteres of ribavirin 4. All compounds were evaluated in vitro for cytostatic and antiviral activity. The pyrazolo[4,3-d]-1,2,3-triazin-4-one nucleosides that resulted were substantially devoid of any activity; only 15h,k showed a moderate cytostatic activity against T-cells. However, pyrazole nucleosides 9b,c,e were potent and selective cytotoxic agents against T-lymphocytes, whereas 9e showed a selective, although not very potent, activity against coxsackie B1.

Retinoic acid conjugates as potential antitumor agents: synthesis and biological activity of conjugates with Ara-A, Ara-C, 3(2H)-furanone, and aniline mustard moieties.

In a dual targeting approach, to explore the ability of tretinoin (all-trans-retinoic acid) to behave as a covalent carrier for cytotoxic entities, conjugates of retinoic acid with a few representative molecules, being important examples of antitumor pharmacophores (i.e., nucleoside analogues and alkylating agents), have been synthesized and tested for their cytostatic and differentiating activity. All compounds were stable to in vitro hydrolysis in human plasma and more lipophilic than the parent compounds, thus consenting enhanced uptake into the cells. Among the nucleoside analogues the Ara-C derivatives 3 and 6 and the Ara-A derivative 7 proved the most cytostatic (IC50 < 0.32 microgram/mL) resulting from 25- to > 144-fold more active (Ara-A derivatives) or at least as equally active (Ara-C derivatives) as compared to the parent nucleosides. Compound 3, endowed with a highly lipophilic silyl moiety at the 3' and 5' positions, showed the highest differentiating activity (54% and 44% differentiated HL-60 cells at 0.2 and 0.05 microgram/mL respectively). With regard to the retinoic acid conjugates of alkylating agents, compound 10 was the most cytostatic agent (IC50 < 0.32 microgram/mL) and the most potent differentiating agent (33-34% at 0.32 and 0.08 microgram/mL). These structures may also be regarded as analogs of either retinoic acid or the cytotoxic compound.

Pyrazolo[4,3-d]pyrimidine nucleosides. Synthesis and antiviral activity of 1-beta-D-ribofuranosyl-3-methyl-6-substituted-7H-pyrazolo[4,3-d]pyr imi din-7-ones.

N1 analogues of formycin B, with substituents at the 3 and 6 positions of the pyrazolo[4,3-d]pyrimidine moiety were synthesized by the direct SnCl4-catalyzed ribosylation method. The site of the glycosidic linkage and the anomeric configurations were established on the basis of X-ray crystallography, as well as 1H and 13C nuclear magnetic resonance spectroscopy. Preliminary results of the antiviral testing of these derivatives in vitro are described.

Structure-activity relationship studies of novel heteroretinoids: induction of apoptosis in the HL-60 cell line by a novel isoxazole-containing heteroretinoid.

In a search for retinoic acid receptor (RAR and RXR)-selective ligands, a series of isoxazole retinoids was synthesized and evaluated in vitro in transcriptional activation and competition binding assays for RARs and RXRs. In addition, these compounds were evaluated for their differentiating, cytotoxic, and apoptotic activities. In general, these derivatives showed scarcely any binding affinity and were not active in the transcriptional assay. However, among these isoxazole derivatives, the cis-isomer 14b was identified as a potent inducer of apoptosis, and its activity was found to be 6.5 and 4 times superior than that of 13-cis- and 9-cis-retinoic acids, respectively. On the other hand, compound 13b, which has the trans stereochemistry at the double bond, was found not to be active in the apoptotic assay, but it was endowed with appreciable differentiating activity. Therefore, it seems that the different stereochemistry of the double bond may be associated with a different biological activity: potent apoptotic activity for the cis-isomer but differentiating activity for the trans structure. This biological behavior was found, at least in part, for the 9-cis- and 13-cis-retinoic acids with respect to the all-trans-retinoic acid. Thus, structure 14b could offer an interesting model for the design of new compounds endowed with apoptotic activity.

Heterocycle-containing retinoids. Discovery of a novel isoxazole arotinoid possessing potent apoptotic activity in multidrug and drug-induced apoptosis-resistant cells.

In a search for retinoic acid (RA) receptor ligands endowed with potent apoptotic activity, a series of novel arotinoids were prepared. Because the stereochemistry of the C9-alkenyl portion of natural 9-cis-RA and the olefinic moiety of the previously synthesized isoxazole retinoid 4 seems to have particular importance for their apoptotic activity, novel retinoid analogues with a restricted or, vice versa, a larger flexibility in this region were designed and prepared. The new compounds were evaluated in vitro for their ability to activate natural retinoid receptors and for their differentiation-inducing activity. Cytotoxic and apoptotic activities were, in addition, evaluated. In general, these analogues showed low cytotoxicity, with the restricted structures being slightly more active than the more flexible ones. As an exception, however, the isoxazole retinoid 15b proved to be particularly able to induce apoptosis at concentrations <5 microM, showing a higher activity than the classical retinoids such as all-trans-RA, 13-cis-RA, and 9-cis-RA and the previously described synthetic retinoid 4. 15b also exhibited a good affinity for the retinoid receptors. Interestingly, another important property of 15b was its ability to induce apoptosis in the HL60R multidrug-resistant (MDR) cell line, at the same concentration as is effective in HL60. Therefore, 15b represents a new retinoid possessing high apoptotic activity in an MDR cell line. The ability of 15b to act on K562 and HL60R cells suggests that this compound may have important implications in the treatment of different leukemias, and its structure could offer an interesting model for the design of new compounds endowed with apoptotic activity on MDR- and retinoid-resistant malignancies.

Effects of chemically modified tetracyclines (CMTs) in sensitive, multidrug resistant and apoptosis resistant leukaemia cell lines.

Recently discovered chemically modified tetracyclines (CMTs) have shown in vitro and in vivo anti-proliferative and anti-tumour activities. Here, we evaluated in vitro the anti-proliferative and apoptotic activity of six different dedimethylamino chemically modified tetracyclines (CMT-1, CMT-3, CMT-5, CMT-6, CMT-7 and CMT-8) in sensitive and multidrug resistant myeloid leukaemia cells (HL60 and HL60R) in vitro. Three of these compounds (CMT-5, CMT-6, CMT-7) showed low cytotoxic activity both in sensitive and in resistant cells, CMT-3 was endowed with a high anti-proliferative activity only in sensitive cells and was moderately effective as apoptosis inducing agent, with an activity similar to that shown by doxycycline. On the contrary, CMT-1 and CMT-8 were very effective as programmed cell death inducing agents. The apoptotic pathway activated by these compounds involved the activation of caspases, especially caspase-9 and, for CMT-1, also the activation of FAS: Interestingly CMT-8, but not CMT-1, was able to induce apoptosis in multidrug resistant HL60R and in Fas-ligand resistant HUT78B1 cell lines. These properties, together with others previously described (e.g. anti-metastatic and anti-osteolytic activities), suggest that CMT-8 may have important applications in the clinical management of cancer. The comparative analysis of structure-activity relationship of CMT-8 and doxycycline suggests that the C-5 hydroxy moiety may play an important role in conferring activity in multidrug resistant cells. These findings appear to support the hypothesis that CMT-8 may represent an interesting lead for the development of a new class of potent apoptosis inducer agents active in multidrug resistant and Fas-ligand resistant malignancies.