Mariangela Miele

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 β-tubulin, probably causing a molecular distortion resulting in the disassembly of microtubules.

The presence of amplified regions affects the stability of chromosomes in drug-resistant Chinese hamster cells.

The stability of chromosomes carrying amplified CAD (carbamyl phosphate synthetase-aspartate transcarbamylase-dihydroorotase) or DHFR (dihydrofolate reductase) genes was studied in V79 Chinese hamster cell derivatives resistant to PALA (N-phosphonacetyl-L-aspartate) and MTX (methotrexate), respectively. Cells were maintained in the presence of the selective drugs during the study. In both metaphase chromosomes and interphase nuclei, amplified regions were localized by in situ hybridization. In MTX-resistant cells, the amplification-bearing chromosome moved sluggishly at anaphase and gave rise to bud-shaped formations in interphase nuclei. It is suggested that these buds could eventually separate as micronuclei. In both MTX- and PALA-resistant cells, amplified DNA was observed in micronuclei in interphase and in displaced chromosomes in metaphase. Finally, amplification-bearing dicentric chromosomes were found in both drug-resistant cell lines. Cumulatively, these observations indicate that the presence of the amplified region in a chromosome renders it unstable: chromosomes bearing an amplified region tended to be excluded from cells, and rearrangements were more frequent than in normal chromosomes.

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

BackgroundTaxol 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.ResultsCalli 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.ConclusionHere 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.

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.

Aflatoxin exposure and cytogenetic alterations in individuals from The Gambia, West Africa

Aflatoxin-albumin adducts in peripheral blood provide a measure of exposure to aflatoxin over the previous 2-3 months. In the present study, the levels of these adducts were determined in a group of individuals from The Gambia, West Africa and were compared in a cross-sectional study to the levels of various cytogenetic alterations (chromosomal aberrations, micronuclei, sister chromatid exchanges) in the same individuals to test whether an increase in genetic damage is associated with an increased exposure in this population. Of 35 subjects tested for aflatoxin-albumin adducts, all but 3 were positive. There were no correlations between the adduct level and the number of cytogenetic abnormalities at the individual level. A comparison of the cytogenetic alterations was made between Gambian individuals and a group of 22 healthy people from Italy where aflatoxin exposure is expected to be low. The levels of structural chromosomal aberrations, sister chromatid exchanges and micronuclei were all higher in the former group. Overall, these data are indicative of a higher exposure to genotoxins in Gambian subjects, one of which are aflatoxins, but suggest that more specific genetic markers of aflatoxin exposure are required to further examine the link between aflatoxin exposure and genetic alterations.

Chromosome aberrations associated with CAD gene amplification in Chinese hamster cultured cells

Eleven sublines with increasing resistance to N-phosphonacetyl-L-aspartate (PALA) were isolated from the V79,B7 Chinese hamster cell line. Aspartate transcarbamylase activity and CAD gene copy number increased with increasing resistance of sublines. In situ hybridization with a DNA probe for the CAD gene showed that the amplified sequences resided in the terminal region of a marker chromosome with elongated q arms. This region stained homogeneously after G-banding. A high incidence of both numerical and structural chromosome aberrations was found in PALA-resistant cells. In hyperdiploid and polyploid cells, containing 2 copies of the marker chromosome, dicentrics were found at a very high frequency. As indicated by in situ hybridization and G-banding, they originated from a rearrangement involving 2 homologous marker chromosomes.

Structural Comparison of the Interaction of Tubulin with Various Ligands Affecting Microtubule Dynamics

Microtubules (MTs), which are highly dynamic assemblies of the protein tubulin, play important and diverse roles in eukaryotic cells. MT dynamics are regulated during the cell cycle by interacting with a large number of endogenous cellular regulators. In addition, many anti-tumour drugs and natural ligands that interact directly with tubulin are able to either stabilise or destabilise MTs and to disrupt the normal dynamics. Herein, we compare the structures of tubulin when complexed with different ligands in order to analyse: (i) various binding-sites of the protein and different positions of ligands within the microtubule (ii) the diverse effect on the microtubule dynamics. The structures and data given are essential for understanding tubulin-ligand interactions and their influence on the regulation of the microtubule system.

Localization of amplified CAD genes on rearranged chromosomes of Chinese hamster cells

Chinese hamster cell lines carrying an amplified CAD region were selected from V79,B7 cells by their resistance to N-phosphonacetyl-L-aspartate (PALA). In one of the selected cell lines, SP PALAinf1supRL, an acrocentric chromosome with abnormally elongated q arms was identified as a marker for the PALA-resistant phenotype. The marker chromosome carried a homogeneously staining region close to a telomeric nucleolar organizer region. In the same region, localization of amplified CAD sequences was demonstrated by in situ hybridization. The marker chromosome was found to undergo extensive rearrangements. In particular, dicentric chromosomes, occurring with an unusually high incidence, were found to originate from end-fusion of two homologous marker chromosomes.

Etoposide-resistance in a neuroblastoma model cell line is associated with 13q14.3 mono-allelic deletion and miRNA-15a/16-1 down-regulation

Drug resistance is the major obstacle in successfully treating high-risk neuroblastoma. The aim of this study was to investigate the basis of etoposide-resistance in neuroblastoma. To this end, a MYCN-amplified neuroblastoma cell line (HTLA-230) was treated with increasing etoposide concentrations and an etoposide-resistant cell line (HTLA-ER) was obtained. HTLA-ER cells, following etoposide exposure, evaded apoptosis by altering Bax/Bcl2 ratio. While both cell populations shared a homozygous TP53 mutation encoding a partially-functioning protein, a mono-allelic deletion of 13q14.3 locus, where the P53 inducible miRNAs 15a/16-1 are located, and the consequent miRNA down-regulation were detected only in HTLA-ER cells. This event correlated with BMI-1 oncoprotein up-regulation which caused a decrease in p16 tumor suppressor content and a metabolic adaptation of HTLA-ER cells. These results, taken collectively, highlight the role of miRNAs 15a/16-1 as markers of chemoresistance.

Research paperChromosome aberrations associated with CAD gene amplification in Chinese hamster cultured cells

Eleven sublines with increasing resistance to N-phosphonacetyl-l-aspartate (PALA) were isolated from the V79,B7 Chinese hamster cell line. Aspartate transcarbamylase activity and CAD gene copy number increased with increasing resistance of sublines. In situ hybridization with a DNA probe for the CAD gene showed that the amplified sequences resided in the terminal region of a marker chromosome with elongated q arms. This region stained homogeneously after G-banding. A high incidence of both numerical and structural chromosome aberrations was found in PALA-resistant cells. In hyperdiploid and polyploid cells, containing 2 copies of the marker chromosome, dicentrics were found at a very high frequency. As indicated by in situ hybridization and G-banding, they originated from a rearrangement involving 2 homologous marker chromosomes.