Synthesis of short retinoidal amides related to fenretinide: antioxidant activities and differentiation-inducing ability.

PURPOSE: By a scaffold shortening strategy, a small series of retinoidal amides fenretinide (4-HPR) analogs have been synthesized from α, ß-ionones and tested for their antiproliferative and differentiating activities, and antioxidant effect. METHODS: The antiproliferative activity and triggering of apoptosis of our short retinoids were evaluated by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay and 4'-6-diamidino-2-phenylindole staining and microscope evaluation after 3- or 6-day exposure, while their differentiating activity was established by the analysis of the expression of the CD11b marker of differentiation in treated HL60 target cells and by the superoxide production assayed colorimetrically by the nitro blue tetrazolium-reducing activity assay. Finally, the antioxidant activity was determined by the 2,2'-azino-bis-(3-ethylbenzthiazoline-6-sulphonic acid) diammonium salt radical cation decolourisation assay utilizing the antioxidant Trolox (6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid) as reference (Trolox equivalent antioxidant capacity, or TEAC). Docking analysis was performed to study the binding features to the Retinoic Acid Receptor alpha (RARα). RESULTS: While no pharmacologically relevant antiproliferative activity was evidenced, some of our short retinoids showed a differentiating and antioxidant activity similar to that of 4-HPR. In particular, compound 2b6 displayed a scavenging activity two times more efficient than 4-HPR itself. Finally, the docking analysis showed that these short retinoids, like 4-HPR, bind to the RARα protein with good fitness scores. CONCLUSION: Our data could pave the way for the design of new potent and less toxic antioxidant and differentiating compounds related to 4-HPR.

Evaluation of the anti-proliferative activity of three new pyrazole compounds in sensitive and resistant tumor cell lines.

BACKGROUND: In previous papers we demonstrated that the activity of short heteroretinoids as anti-proliferative and pro-apoptotic compounds was deeply linked to their heterocyclic moiety and that ionone-derived 1,5-pyrazoles had the highest anti-proliferative activity in our preliminary experiments. We then demonstrated the high and pharmacologically significant anti-proliferative and apoptotic activities of the pyrazole compounds 2-(1-(4-chlorophenyl)-1H-pyrazol-5-yl)-5-methoxyphenol (EN12-4), 5-methoxy-2-(1-(pyridin-2-yl)-1H-pyrazol-5-yl)phenol (EN12-2A) and 2-(5-(4-methoxyphenyl)-1H-pyrazol-1-yl)pyridine (EN7-2) establishing, especially for EN12-2A, a possible mechanism of action involving the cell microtubular system. METHODS: Here, the anti-proliferative activity of these pyrazole compounds was analyzed in vitro by the MTT assay in six drug-resistant cell lines, five of which were selected after exposure to increasing concentrations of cisplatin (L1210/DDP), doxorubicin (A2780/DX3), 5-fluorouracil (HCT-8/5FU), taxol (A549/T24) and etoposide (MCF-7/VP), and one was obtained by transfection of the ABCG2 membrane transporter (HEK-293/R2). RESULTS: Our data show that these compounds have a similar anti-proliferative activity in nearly all resistant and sensitive cell lines, demonstrating their ability to overcome the most common mechanisms of drug resistance with two exceptions regarding the MCF-7/VP cell line over-expressing the ABCC1 (MRP1) transporter, and the MDR1 over-expressing A2780/DX3 cells, with a calculated RI = 3.2 for EN12-2A, relative to their sensitive cellular counterpart. On the other hand, the taxol-resistant A549/T24 cell line showed a significantly increased sensitivity to our compounds. CONCLUSIONS: Our data suggest that our pyrazole compounds are able to overcome in vitro the most common drug-resistance mechanisms demonstrating a significant anti-proliferative activity and confirming a mechanism of action involving the depolymerization of microtubules.

Synthesis and biological evaluation of novel pyrazole derivatives with anticancer activity.

We synthesized thirty-six novel pyrazole derivatives and studied their antiproliferative activity in human ovarian adenocarcinoma A2780 cells, human lung carcinoma A549 cells, and murine P388 leukemia cells. Four of these substances were selected because of their higher antiproliferative activity and further analyses showed that they were all able to induce apoptosis, although to a different extent. The expression of p53 and p21(waf1), which induce apoptosis and cell cycle arrest, was evaluated by western blot analysis in cells treated with compound 12d. The analysis of the cell cycle showed that all the selected compounds cause a partial G2/M block and the formation of polyploid cells. Furthermore, the four selected compounds were tested for their interaction with the microtubular cytoskeletal system by docking analysis, tubulin polymerization assay and immunofluorescence staining, demonstrating that the compound 12d, unlike the other active derivatives, was able to significantly bind dimers of α- and ß-tubulin, probably causing a molecular distortion resulting in the disassembly of microtubules.

Antiproliferative and proapoptotic activities of a new class of pyrazole derivatives in HL-60 cells.

A series of N-substituted pyrazole derivatives have been synthesized and tested for their anticancer effect on the HL-60 leukaemia cell line. Four were active both in cell-growth inhibition and in inducing apoptosis. The inhibition of cell growth mainly reflects a compound-induced reduction in the number of cells in phases from S to M, whereas the induction of apoptosis involves inhibition of expression of Bcl-2 and enhanced expression of Bax with consequent reduced activation of the proapoptotic caspase 3. Finally, preliminary experiments carried out with tumor cells from myelogenous leukaemic patients showed that the compounds 4c, 4l, 4m, and 4n are indeed capable of inducing apoptosis.

Antiviral activity of indole derivatives.

Unsymmetrical methylene derivatives 5 were prepared following a known method, by reaction of the Mannich bases of 2-naphthols 4 with indoles. All synthesized compounds were tested against a wide panel of viruses, since previous work showed that Mannich bases on 7-hydroxycoumarin 1 and unsymmetrical methylene derivatives 2 were endowed with some antiviral activities. The symmetrical Mannich bases 4 were completely inactive, whereas the unsymmetrical methylene derivatives 5, although possessing a certain degree of toxicity, showed a significant activity against RSV. Some of compounds 5 showed a moderate antiviral activity against HIV-1, BVDV, YFV and CVB-2. The lack of activity of Mannich bases 4 demonstrates the crucial importance for antiviral activity of coumarin moiety present in Mannich bases 1.

Taxanes from Shells and Leaves of Corylus avellana.

Paclitaxel is an effective antineoplastic agent originally extracted in low yield from the bark of Taxus brevifolia. Although it was generally considered a particular metabolite of Taxus sp., paclitaxel was recently found in hazel cell cultures. The aim of the present work was to verify whether hazel differentiated tissues could be used as a commercial source of paclitaxel and other taxanes. Thus, shells and leaves of hazel plants were analyzed by ELISA and HPLC-MS. Both shell and leaf extracts contained taxanes. Among these, paclitaxel, 10-deacetylbaccatin III, baccatin III, paclitaxel C, and 7-epipaclitaxel were identified and quantified. Hazel extracts also showed biological activity, inhibiting metaphase to anaphase transition in a human tumor cell line. The level of total taxanes in leaves was higher than in shells collected in the same period from the same plants. However, the finding of these compounds in shells, which are considered discarded material and are mass produced by many food industries, is of interest for the future availability of paclitaxel and other antineoplastic compounds.

Activity of Mannich bases of 7-hydroxycoumarin against Flaviviridae.

Some Mannich bases of 7-hydroxycoumarin (2) and their simple derivatives (3 and 4) were prepared and tested against viruses containing single-stranded, positive-sense RNA genomes (ssRNA(+)). This study was directed toward Flaviviridae and, in particular, HCV surrogate viruses (BVDV, YFV). The 7-hydroxy derivatives 2 were generally devoid of activity, but when position 7 was propylated, the resulting 7-propyloxy derivatives 3 were in some cases endowed with an interesting activity against BVDV. The formation of 7-benzoyl derivatives 4 gave compounds generally lacking in activity against Flaviviridae, whereas the appearance of activity against RSV has been observed. Also some unsymmetrical methylene derivatives 5-7 (namely coumarins bridged to chromones or indoles) were found moderately active in antiviral tests. Derivatives 3 were submitted to a molecular modeling study using DNA polymerase of HCV as a target. The good correlation between calculated molecular modeling IC(50) and experimental EC(50) indicates that DNA polymerase is potentially involved in the inhibition of surrogate HCV viruses.

In vitro cell cultures obtained from different explants of Corylus avellana produce Taxol and taxanes.

BACKGROUND: Taxol is an effective antineoplastic agent, originally extracted from the bark of Taxus brevifolia with a low yield. Many attempts have been made to produce Taxol by chemical synthesis, semi-synthesis and plant tissue cultures. However, to date, the availability of this compound is not sufficient to satisfy the commercial requirements. The aim of the present work was to produce suspension cell cultures from plants not belonging to Taxus genus and to verify whether they produced Taxol and taxanes. For this purpose different explants of hazel (Corylus avellana species) were used to optimize the protocol for inducing in vitro callus, an undifferentiated tissue from which suspension cell cultures were established. RESULTS: Calli were successfully induced from stems, leaves and seeds grown in various hormone concentrations and combinations. The most suitable callus to establish suspension cell cultures was obtained from seeds. Media recovered from suspension cell cultures contained taxanes, and showed antiproliferative activity on human tumour cells. Taxol, 10-deacetyltaxol and 10-deacetylbaccatin III were the main taxanes identified. The level of Taxol recovered from the media of hazel cultures was similar to that found in yew cultures. Moreover, the production of taxanes in hazel cell cultures increased when elicitors were used. CONCLUSION: Here we show that hazel cell cultures produce Taxol and taxanes under controlled conditions. This result suggests that hazel possesses the enzymes for Taxol production, which until now was considered to be a pathway particular to Taxus genus. The main benefit of producing taxanes through hazel cell cultures is that hazel is widely available, grows at a much faster rate in vivo, and is easier to cultivate in vitro than yew. In addition, the production of callus directly from hazel seeds shortens the culture time and minimizes the probability of contamination. Therefore, hazel could become a commercial source of Taxol and taxanes, both to be used as new therapeutic agents or as new precursors for Taxol semi-synthesis.

Synthesis and biological evaluation of novel heterocyclic ionone-like derivatives as anti-inflammatory agents.

Five- and six-membered heterocyclic ionone-like derivatives 4-6 have been synthesised in one step and with good yield from the key intermediate 3a and appropriate bifunctional reagents. Four were active as inhibitors of the respiratory burst of human neutrophils without affecting cell viability. The two most active compounds (5a,d) tested in neutrophil migration assays, were also found to be potent inhibitors of neutrophil chemotactic responsiveness. These two molecules could be considered as lead compounds of new drugs which can be an effective tool to treat psoriasis and related neutrophilic dermatoses.

Synthesis and hybridization properties of the conjugates of oligonucleotides and stabilization agents. Part 3.

New compounds having tri- or pentamethylenamine linker functions were synthesized. These derivatives were covalently attached through the 5'-phosphoramide linkage to heptanucleotide pd(CCAAACA). Complementary complexes of the octanucleotide pd(TGTTTGGC) and above oligonucleotide conjugates were tested for their thermodynamic response. The T(m) data and thermodynamic parameters for complex formation confirmed the ability of chromone (gamma-pyrone) derivatives to stabilize strongly the 7-mer/8-mer complementary complex. Moreover, benzochromone (naphthopyrane) and, surprisingly, tetrahydropyrimidinethanone derivatives showed the capacity of stabilizing this 7-mer/8-mer complementary complex. The effect of all these compounds on the stability of the oligonucleotide complexes (DeltaDeltaG at 37 degrees C ranged from -1.2 to -2.0 kcal/mol) was shown to be comparable to the effect of one nucleotide base pair and similar to the effect (DeltaDeltaG at 37 degrees C ranged from -1.5 to -2.0 kcal/mol) found for acridine-oligonucleotide conjugates, which served as a reference in this study.

Dynamic, thermodynamic, and kinetic basis for recognition and transformation of DNA by human immunodeficiency virus type 1 integrase.

Specific interactions between retroviral integrase (IN) and long terminal repeats are required for insertion of viral DNA into the host genome. To characterize quantitatively the determinants of substrate specificity, we used a method based on a stepwise increase in ligand complexity. This allowed an estimation of the relative contributions of each nucleotide from oligonucleotides to the total affinity for IN. The interaction of HIV-1 integrase with specific (containing sequences from the LTR) or nonspecific oligonucleotides was analyzed using a thermodynamic model. Integrase interacted with oligonucleotides through a superposition of weak contacts with their bases, and more importantly, with the internucleotide phosphate groups. All these structural components contributed in a combined way to the free energy of binding with the major contribution made by the conserved 3'-terminal GT, and after its removal, by the CA dinucleotide. In contrast to nonspecific oligonucleotides that inhibited the reaction catalyzed by IN, specific oligonucleotides enhanced the activity, probably owing to the effect of sequence-specific ligands on the dynamic equilibrium between the oligomeric forms of IN. However, after preactivation of IN by incubation with Mn(2+), the specific oligonucleotides were also able to inhibit the processing reaction. We found that nonspecific interactions of IN with DNA provide approximately 8 orders of magnitude in the affinity (Delta G degrees approximately equal to -10.3 kcal/mol), while the relative contribution of specific nucleotides of the substrate corresponds to approximately 1.5 orders of magnitude (Delta G degrees approximately equal to - 2.0 kcal/mol). Formation of the Michaelis complex between IN and specific DNA cannot by itself account for the major contribution of enzyme specificity, which lies in the k(cat) term; the rate is increased by more than 5 orders of magnitude upon transition from nonspecific to specific oligonucleotides.