Gastrointestinal transit and 5-ASA release from a new mesalazine extended-release formulation

BACKGROUND

Mesalazine (5-aminosalicylic acid, 5-ASA)-containing formulations represent a cornerstone in the treatment of inflammatory bowel diseases. Recently, a new formulation has been developed to provide selective and more homogeneous release of 5-ASA compared to traditional systems.

METHODS

In a first study, gastrointestinal transit was followed by gamma-scintigraphy after single-dose application of tablets containing 1200 mg mesalazine to 12 healthy male volunteers. 5-ASA release was verified by the assessment of plasma pharmacokinetics. In a second, 7-day, multiple-dose study, the steady state plasma pharmacokinetics, urinary excretion and safety profile were characterized after twice-daily tablet administration to 12 healthy volunteers.

RESULTS

Tablet erosion started after 6.9 +/- 1.1 h in the ascending or transverse colon. Radioactivity spread homogeneously throughout the colon, indicating the sustained release of active 5-ASA. Plasma kinetics indicated an earlier initial absorption of 5-ASA, i.e. during transit of the small intestine and ileum. Mean Cmax values (350.6 +/- 322.6 ng/mL) were observed during location in the ileo-caecal region. The mean relative absorption of 5-ASA was 19.9 +/- 18.2% in the small intestine and ileum and 80.1 +/- 18.2% in the colon.

CONCLUSIONS

The administration of the new mesalazine formulation was well tolerated, and 5-ASA was continuously released along the whole colon, a favourable prerequisite for the therapy of distally located inflammatory bowel disease.

Approaches for the inhibition of human telomerase based on the use of peptide nucleic acids and hammerhead ribozymes

The ability of peptide nucleic acids and hammerhead ribozymes, which target different subunits of human telomerase, to efficiently inhibit the enzyme's catalytic activity has been clearly demonstrated in several in vitro studies carried out in human immortalized and cancer cell lines. However, the actual efficacy of these molecules still needs to be validated in in vivo human tumor models, and such validation appears to be largely dependent on the development of reliable systems for their intracellular delivery.

Isomer-specific activity of dichlorodyphenyltrichloroethane with estrogen receptor in adult and suckling estrogen reporter mice

We investigated the tissue-specific effects of dichlorodyphenyltrichloroethane (DDT) isomers in adult and suckling newborn mice, using a novel mouse line engineered to express a reporter of estrogen receptor transcriptional activity (ERE-tkLUC mouse). The DDT isomers p,p'-DDT [1,1,1-trichloro2,2-bis(p-chlorophenyl) ethane] and o,p'-DDT [1,1,1-trichloro-2(p-chlorophenyl)-2-(o-chlorophenyl) ethane] were specifically selected as a weak and a strong estrogen, respectively. In adult male mice, p,p'-DDT induced luciferase activity in liver, brain, thymus, and prostate but not in heart and lung. The effect of p,p'-DDT was dose-dependent, maximal at 16 h after sc treatment, and completely blocked by the estrogen receptor antagonist ICI-182,780. In all the organs analyzed, except the liver, administration of o,p'-DDT showed a pattern of luciferase induction superimposable to that of its isomer p,p'-DDT. In liver, o,p'-DDT significantly decreased basal luciferase activity and blocked the reporter induction by 17beta-estradiol. These data lead us to hypothesize that a modulation of ER activity may be involved in the toxic effects of DDT demonstrated by epidemiological and experimental studies. Luciferase activity was also studied in 4-d-old mice lactating from a mother injected with either p,p'-DDT or o,p'-DDT. Both isomers induced a 2-fold increase in the newborn brain. An opposite effect was observed in liver, where p,p'-DDT increased and o,p'-DDT decreased luciferase, thus indicating that these compounds modulate ER activity in adult and newborn tissues by use of a similar mechanism. The ERE-tkLUC mouse proves to be a suitable tool to functionally assess the tissue specificity of estrogenic/antiestrogenic compounds in adult (as well as in suckling) mice.

Inhibition of telomerase activity by a distamycin derivative: effects on cell proliferation and induction of apoptosis in human cancer cells

In this study, we evaluated the potential of the distamycin derivative MEN 10716 as a telomerase inhibitor. Exposure of human melanoma cell extracts to MEN 10716 induced a dose-dependent inhibition of telomerase activity, with an IC50 of 24+/-3 microM. When intact JR8 melanoma cells were chronically exposed to the drug (200 microM every other day for 50 days), a marked inhibition (>80%) of the enzyme's catalytic activity was consistently observed starting from day 1. At later points in time, MEN 10716 inhibited melanoma cell proliferation and induced apoptosis. Cells surviving MEN 10716 exposure were characterised by a higher melanin content and a greater expression of p16(INK4A) protein than control cells. The effects of MEN 10716 were subsequently evaluated in different tumour cell systems. In particular, even in the H460 non-small cell lung cancer cell line, chronic exposure of the cells to the drug (100 microM every other day for 50 days) induced a consistent inhibition (>85%) of telomerase activity, a reduction of cell proliferation potential, and apoptosis. Conversely, MEN 10716 treatment did not appreciably inhibit cell proliferation in the U2-OS telomerase-negative human osteogenic sarcoma cell line. Interestingly, no variation in the mean telomere length was observed in MEN 10716-treated JR8 melanoma cells, whereas an appreciable increase in the mean telomere length was found in H460 lung cancer cells after drug exposure. Overall, the results of the study indicate that MEN 10716 is a possible telomerase inhibitor and suggest that abrogation of telomerase activity can affect cell proliferation even through pathways that are not dependent on telomere erosion.

Treatment of winery wastewater in a sequencing batch biofilm reactor

Pilot-scale experiments were carried out applying the SBBR process (Sequencing Batch Biofilm Reactor) for the treatment of winery wastewater. The aim was the evaluation of the SBBR performance and the development of a control strategy based on dissolved oxygen (DO) for the optimisation of the SBBR treatment cycle and the minimisation of the energy supply. The results of the experimentation have confirmed the applicability of the SBBR process pointing out high COD removal efficiencies between 86% and 99%, with applied loads up to 29 gCOD m-2d-1, corresponding to 8.8 kgCOD m-3d-1. The on-line monitoring of DO concentration appeared as a good indicator of the progress in the COD biodegradation. The control strategy for the ending of the SBBR cycles was based on the time derivative of the DO concentration. The optimised control strategy makes it possible to obtain a steady quality of the effluent wastewater with an average daily applied load of 6.3 kgCOD m-3d-1 rather than 3.5 kgCOD m-3d-1 for the non-optimised SBBR cycle. The possibility of optimising the SBBR cycle through a simple control of the DO in the mixed liquor could be an interesting solution for the biological pre-treatment of winery wastewater to be discharged into sewerage or as a single-stage of a combined treatment plant for the discharge into surface water.

Dairy wastewater treatment in a moving bed biofilm reactor

Dairy raw wastewater is characterised by high concentrations and fluctuations of organic matter and nutrient loads related to the discontinuity in the cheese production cycle and machinery washing. The applicability of a Moving Bed Biofilm Reactor (MBBR) filled with FLOCOR-RMP plastic media to the treatment of dairy wastewater was evaluated in a pilot-plant. COD fractionation of influent wastewater, MBBR performance on COD and nutrient removal were investigated. A removal efficiency of total COD over 80% was obtained with an applied load up to 52.7 gCOD m-2 d-1 (corresponding to 5 kgCOD m-3d-1). The COD removal kinetics for the MBBR system was assessed. The order of the kinetics resulted very close to half-order in the case of a biofilm partially penetrated by the substrate. The nitrogen removal efficiency varied widely between 13.3 and 96.2% due to the bacterial synthesis requirement. The application of a MBBR system to dairy wastewater treatment may be appropriate when upgrading overloaded activated sludge plants or in order to minimise reactor volumes in a pre-treatment.

Cell growth inhibition, G2M cell cycle arrest and apoptosis induced by the imidazoacridinone C1311 in human tumour cell lines

The cytotoxic activity of the imidazoacridinone C1311 was assessed on two ovarian cancer cell lines (A2780, OAW42) and one osteogenic sarcoma cell line (U2-OS) and their sublines (A2780Cp8, OAW42-MER and U2-OS-R) with experimentally induced resistance to cisplatin. A 1-h exposure to C1311 significantly inhibited the growth of all cell lines, with IC50 values ranging from 0.50 +/-0.11 to 4.10+/-0.36 microM. No or only partial cross-resistance was found between C1311 and cisplatin in the different cell lines. Treatment with equitoxic (IC50) C1311 concentrations consistently induced accumulation of cells in the G2M phase. The cyclin B1-associated p34(cdc2) kinase activity in cells arrested in G2M was superimposable to that of control cells in the OAW42-MER and U2-OS cell lines, whereas a reduction of cdc2 catalytic activity was observed in OAW42 and U2-OS-R cells. Exposure to C1311 (IC50) induced apoptosis in the U2-OS and U2-OS-R cell lines, whereas in the OAW42 and OAW42-MER cell lines there was a negligible percentage of apoptotic cells. In U2-OS, U2-OS-R and OAW42 cells, C1311 induced an increase in p53 expression and an increase in p21waf1 protein, whereas p53 failed to transactivate p21waf1 in OAW42-MER cells. An almost complete abrogation of bcl-2 was observed in U2-OS-R cells in correspondence with the peak of apoptosis induction. Our results indicate that C1311 is active against human ovarian cancer and osteogenic sarcoma cells and is not cross-resistant with CDDP. Moreover, C1311 blocks cells in the G2M phase and induces apoptosis in a small percentage of osteogenic sarcoma cells.

Possible regulation of telomerase activity by transcription and alternative splicing of telomerase reverse transcriptase in human melanoma

To investigate the regulatory mechanisms of telomerase activity in human melanoma cells, we assessed the enzyme's catalytic activity and the expression of the telomerase subunits, the human telomerase RNA, the human telomerase-associated protein, and the human telomerase reverse transcriptase, in 52 melanoma lesions. Eight normal skin specimens were also studied. Telomerase activity was detected in 84.6% of melanomas, whereas all skin specimens were telomerase negative. Human telomerase-associated protein mRNA and human telomerase RNA were constitutively expressed in all melanoma and skin specimens. Although at a variable level of expression, human telomerase reverse transcriptase mRNA was detected in all but one melanomas, whereas it was never present in skin samples. Reverse transcriptase-polymerase chain reaction experiments were performed using primers within the reverse transcriptase domain of human telomerase reverse transcriptase and revealed the presence of multiple alternatively spliced transcripts in melanoma specimens. Among the 44 telomerase-positive melanomas, one showed the full-length transcript alone whereas in all other specimens a full-length message was present with different combinations of alternatively spliced variants. In these tumors the expression of the full-length transcript was generally equal to or higher than that of the alternatively spliced variants. The ratio full-length transcript to alternatively spliced species ranged from 0.6 to 5.26, with a median value of 1.18. Among the seven telomerase-negative melanomas, one displayed the beta deletion transcript alone, whereas in the remaining six tumors weak expression of the full-length transcript and a more abundant level of alternatively spliced transcripts were found. In these cases human telomerase reverse transcriptase ratio ranged from 0.09 to 1.1, with a median value of 0.40. The results suggest that transcription and alternative splicing of human telomerase reverse transcriptase are regulatory mechanisms controlling telomerase activity in melanoma.

Evaluation of mechanical and corrosion biocompatibility of TiTa alloys

As-received and heat-treated Ti40Ta and Ti50Ta alloys were evaluated to determine their corrosion as well as mechanical performances and compared to Ti6A14V, a common material utilized for orthopedic (surgical) implants. Anodic potentiodynamic tests performed in Plasmalyte showed that all samples, except for the Ti50Ta specimen aged at 400 degrees C for 3 h gave a curve similar to that of Ti6A14V. Optical and TEM microscopy was performed to determine as-received and heat-treated microstructures. As-received materials showed an alpha precipitate in an alpha+beta and martensite matrix. Samples that were aged at 400 degrees C increased in the density and the length of the alpha precipitate. Vickers hardness measurements were performed to get an approximation of the tensile strengths. Aged Ti40Ta and Ti50Ta specimens produced the highest tensile values when compared to the Ti6A14V material, representing a 31% and 56% increase for the 3 h samples and an 18% and 58% increase for the 10 h samples. Of all the materials studied the Ti50Ta specimen aged for 10 h exhibited the best biocompatibility showing excellent corrosion resistance combined with the highest tensile strength (1089 MPa and 58% harder/stronger than Ti6A14V).

Inhibition of telomerase activity by a cell-penetrating peptide nucleic acid construct in human melanoma cells

We investigated the effect of two peptide nucleic acids (PNAs), which are complementary to the RNA component of human telomerase, on the catalytic activity of the enzyme. PNAs induced a dose-dependent reduction of telomerase activity in cell extracts from human melanoma cell lines and surgical specimens. To down-regulate telomerase in intact cells, we generated a chimeric molecule synthesized by coupling the 13-mer PNA to the Antennapedia peptide. The PNA construct induced a dose- and time-dependent inhibition of telomerase activity. However, a 20-day exposure to the PNA construct only caused a slight increase in melanoma cell doubling time and failed to induce any telomere shortening.

Telomerase activity and telomere length in human ovarian cancer and melanoma cell lines: correlation with sensitivity to DNA damaging agents

Since telomerase plays a role in cellular resistance to apoptosis, which is the primary mode of cell death induced by several drugs, telomerase could be involved in determining the chemosensitivity profile of tumor cells. Thus, we investigated the relationship between telomerase activity, telomere length and chemosensitivity to effective antitumor agents in a panel of human melanoma and ovarian cancer cell lines. Telomerase activity, as detected by the telomeric repeat amplification protocol, ranged from 0.58 to 1.10 arbitrary units in individual cell lines, with similar median values for melanoma and ovarian carcinoma cell lines (0.80 vs. 0.90). Telomeres were generally longer in melanoma than in ovarian carcinoma cell lines, with a more than 2-fold median telomere restriction fragment length (7.74 vs. 3.82 kb). No significant correlation was evidenced between the two telomere-related parameters and cell population doubling time, DNA index or TP53 gene status. No precise relation was found between telomerase activity and cellular sensitivity to different DNA damaging agents including doxorubicin, cisplatin and the multinuclear platinum compound BBR 3464. In contrast, longer telomeres were associated to resistance to the drugs, even though the association reached statistical significance only for cisplatin. Since platinum compounds may have affinity for telomere sequences, it is conceivable that the interaction is relevant for drug sensitivity/resistance status depending on telomere length.

Inhibition of telomerase activity by a hammerhead ribozyme targeting the RNA component of telomerase in human melanoma cells

Reactivation of telomerase, an RNA-dependent DNA polymerase that synthesizes new telomeric repeats at the end of chromosomes, is a very common feature in human cancers. Telomerase is thought to be essential in maintaining the proliferative capacity of tumor cells and, as a consequence, it could represent an attractive target for new anti-cancer therapies. In this study, we generated a hammerhead ribozyme composed of a catalytic domain with flanking sequences complementary to the RNA component of human telomerase and designed to cleave specifically a site located at the end of the telomerase template sequence. In vitro the ribozyme induced cleavage of a synthetic RNA substrate obtained by cloning a portion of the RNA component of human telomerase. The extent of cleavage was dependent on the ribozyme/substrate ratio as well as the Mg2+ concentration. Moreover, when added to cell extracts from two human melanoma cell lines (JR8 and M14), or three melanoma surgical specimens, the ribozyme inhibited telomerase activity in a concentration- and time-dependent manner. When the ribozyme was delivered to growing JR8 melanoma cells by (N-(1-(2,3 dioleoxyloxy)propil)-N,N,N trimethylammonium methylsulfate-mediated transfer, a marked inhibition of telomerase activity was observed. Next, the ribozyme sequence was cloned in an expression vector and JR8 cells were transfected with it. The cell clones obtained showed a reduced telomerase activity and telomerase RNA levels and expressed the ribozyme. Moreover, ribozyme transfectants had significantly longer doubling times than control cells and showed a dendritic appearance in monolayer culture. No telomere shortening, however, was observed in these clones. Overall, our results indicate that the hammerhead ribozyme is a potentially useful tool for the inactivation of telomerase in human tumors.

The Gly571Arg mutation, associated with the autonomic and sensory disorder congenital insensitivity to pain with anhidrosis, causes the inactivation of the NTRK1/nerve growth factor receptor

Point mutations affecting the NTRK1/TRKA gene, encoding one of the receptors for the nerve growth factor (NGF), have been detected in congenital insensitivity to pain with anhidrosis (CIPA), a human hereditary sensory neuropathy characterized by absence of reaction to noxious stimuli and anhidrosis. To define the defect of NTRK1 in CIPA patients, we have introduced one of the previously reported mutations (Gly571Arg) into both the NTRK1 and the TRK-T3 oncogene cDNAs. The expression of the mutated constructs into COS1 cells revealed that the introduced mutation, while not affecting its correct membrane localization, rendered the NTRK1 protein unable to undergo activation upon stimulation with NGF. Similarly, the mutation abolished the constitutive activation of the TRK-T3 oncogene. Transfection into NIH3T3 and PC12 cells showed the loss of transforming and differentiating activity by the mutated constructs. Our results demonstrate clearly that the CIPA mutations cause the inactivation of the NTRK1 receptor, thus exerting a loss of function effect, and provide an experimental approach to distinguish functional mutations from genetic polymorphisms.

Absorption kinetics and bioavailability of cephalexin in the dog after oral and intramuscular administration

The pharmacokinetics of cephalexin, a first generation cephalosporin, were investigated in dogs using two formulations marketed for humans, but also often employed by practitioners for pet therapy. Cephalexin was administered to five dogs intravenously and intramuscularly as a sodium salt and by the oral route as a monohydrate. The dosage was always 20 mg/kg of active ingredient. A microbiological assay with Sarcina lutea as the test organism was adopted to measure cephalexin concentrations in serum. The mean residence time (MRT) median values after intravenous (i.v.), intramuscular (i.m.) and oral administration (p.o.) were 86 min, 200 min, and 279 min, respectively. After i.m. and oral dosing the peak serum concentrations (24.2 +/- 1.8 micrograms/mL and 20.3 +/- 1.7 micrograms/mL, respectively) were attained at 90 min in all dogs and bioavailabilities were 63 +/- 10% and 57 +/- 5%, respectively. The time course of the cephalexin serum concentrations after oral administration was best described by a model incorporating saturable absorption kinetics of the Michaelis-Menten type: thus in the gastrointestinal tract of dogs a carrier mediated transport for cephalexin similar to that reported in humans, may exist. The predicted average serum concentrations of cephalexin after repeated i.m. and oral administration indicated that, in order to maintain the therapeutic concentrations, the 20 mg/kg b.w. dosage should be administered every 6-8 h.

Hydrocortisone levels in the urine and blood of horses treated with ACTH

An investigation was undertaken to demonstrate whether therapeutic treatment with ACTH raises hydrocortisone (cortisol) levels in horse urine above the limit (1000 ng/ml) established by the International Conference of Racing Authorities with the aim of controlling the abuse of cortisol and ACTH in equine sports. ACTH (200 iu) was administered i.m. to 3 Thoroughbred horses; urine and blood samples were collected at intervals afterwards and analysed by an immunoenzymatic system (ELISA) and HPLC-MS. To ascertain post exercise cortisol levels in untreated horses, 101 urine and 103 serum samples were taken from horses immediately after racing and analysed by ELISA. The peak urine level of cortisol, detected 8 h after ACTH administration, was around 600 ng/ml using either ELISA or HPLC-MS. The peak serum cortisol concentration was found to be around 250 ng/ml by ELISA, but consistently less by HPLC-MS. Mean cortisol levels in post race horses were 135.1+/-72.1 ng/ml in urine and 90.1+/-41.7 ng/ml in serum. High levels of the metabolite 20beta-dihydrocortisol in urine and the cortisol precursor 11beta-desoxycortisol in serum were found. The latter showed high cross-reactivity with cortisol on ELISA. In our experiment, treatment with ACTH 200 iu i.m. did not raise urinary cortisol levels above the 1000 ng/ml threshold proposed by the ICRA.

Modulation of cytotoxic drug activity by mitotane and lonidamine in human adrenocortical carcinoma cells

The ability of mitotane, a DDT derivative with adrenotoxic activity, and lonidamine, an energolytic derivative of indazole-carboxylic acid, to modulate the cytotoxic activity of doxorubicin, epidoxorubicin, cisplatin and VP16 was investigated in a human adrenocortical carcinoma cell line (SW13). A marked variability in cellular response to a 1-h treatment with the individual anticancer agents was observed. The concentrations able to inhibit SW13 cell proliferation by 50% (IC50) were 0.45 microg/ml and 0.4 microg/ml for doxorubicin and epidoxorubicin, respectively, thus indicating a relative sensitivity to anthracyclines. Conversely, the SW13 cell line displayed a marked resistance to cisplatin (IC50, 13.9 microg/ml) and VP16 (IC50, 15 microg/ml). When cells were exposed to anticancer drugs and mitotane simultaneously or in sequence, a positive modulation of anthracycline cytotoxic effects was observed. Although to a lesser extent, mitotane also increased cisplatin activity. Conversely, no potentiation was observed when mitotane was combined with VP16. Lonidamine slightly increased the cytotoxicity of epirubicin and cisplatin as individual agents. Moreover, a supra-additive effect of the three-drug (epidoxorubicin-cisplatin-lonidamine) combination was observed.

Lonidamine as a modulator of taxol activity in human ovarian cancer cells: effects on cell cycle and induction of apoptosis

The ability of lonidamine (LND), an energolytic derivative of indazole-carboxylic acid, to modulate the cytotoxicity of Taxol (TX) was investigated in the A2780 human ovarian cancer cell line. Different cytotoxicity results were obtained as a function of treatment schedule. Specifically, TX followed by LND produced synergistic effects. Conversely, antagonistic effects were recorded when drugs were given simultaneously or according to the opposite sequence. TX induced an oligonucleosomal DNA fragmentation typical of the apoptotic process. The extent and the kinetics of DNA cleavage in samples treated with the taxane alone were similar to those of samples treated with the TX-LND sequence. Activation of Yama protease and degradation of poly (ADP-ribose) polymerase were not observed after individual or combined treatment. LND did not appreciably modify the effect exerted by TX on proteins involved in cell cycle progression (i.e., inhibition of p34cdc2 expression) and apoptosis (i.e., upregulation of wt p53 and transactivation of p21waf1), and only caused a slight induction of the Bax protein. LND alone did not affect tubulin polymerization in A2780 cells and, when administered after a 24 hr TX exposure, did not appreciably alter the extent of tubulin polymerization induced by the taxane. Although additional studies are needed to define the molecular basis of the TX-LND interaction, our results suggest that LND can positively modulate the antitumor activity of TX in ovarian cancer cells and indicate that the energolytic is potentially useful in combination therapy including the taxane in ovarian cancer patients.

Transforming activity of the chimeric sequence formed by the fusion of collagen gene COL1A1 and the platelet derived growth factor b-chain gene in dermatofibrosarcoma protuberans

As a consequence of a reciprocal translocation t(17;22)(q22;q13) and of supernumerary ring chromosomes derived from the t(17;22), a fusion between the platelet-derived growth factor b-chain (PDGF, c-sis proto-oncogene) and the collagen type 1A1 (COL1A1) genes has been recently described in dermatofibrosarcoma protuberans (DP), an infiltrating skin tumor (Simon et al., 1997). Although PDGFB has been implicated in transforming processes via autocrine and paracrine pathways, by the activation of the cognate receptor, no direct evidence of its involvement in neoplastic transformation of human tumours has been so far provided. In this report, we have tested the DNA from four DPs in the classical DNA transfection assay onto NIH3T3 fibroblast cell line. All the DNAs induced the formation of transformed foci in the transfected cultures whose derived cell lines were shown to contain a fused sequence comprising the human COL1A1 and PDGF genes. The relative breakpoint regions have been sequenced revealing that this gene fusion deleted exon 1 of PDGF and released the growth factor from its normal regulation. All the biochemical and biological assays were consistent with the model of an autocrine mechanism for NIH3T3 transformation by the human rearranged PDGFB gene involving the activation of the endogenous PDGF receptor.

Induction of apoptosis by taxol and cisplatin and effect on cell cycle-related proteins in cisplatin-sensitive and -resistant human ovarian cells

The effect of taxol (TX) and cisplatin (CDDP), singly or in association, was assessed on two human ovarian cancer cell lines, one sensitive (A2780) and one resistant (A2780 cp8) to CDDP. Cell lines showed a similar sensitivity to TX, whereas different cytotoxicity results were obtained in the two cell lines as a function of TX and CDDP sequence. Specifically, TX followed by CDDP induced simply additive effects in both cell lines, whereas the opposite sequence produced antagonistic effects in A2780 cells and synergistic effects in A2780 cp8 cells. TX, with or without CDDP, induced oligonucleosomal DNA fragmentation typical of the apoptotic process, but the biochemical mechanisms undergoing apoptosis were different in the two cell lines. In fact, in A2780 cells, TX (with or without CDDP) treatment markedly increased p53 as well as p21waf1 protein expression. In A2780 cp8 cells, drug treatment enhanced p53 levels, whereas the expression of p21waf1 was always undetectable at mRNA and protein levels. In the latter cell line, a premature activation of p34cdc2 kinase was observed in correspondence with the drug-induced increase in the S-phase cell fraction. Such an activation was not ascribable to an increase in the overall expression of p34cdc2 or cyclin B1 proteins, but to a dephosphorylation of p34cdc2 kinase. Overall, our results indicate that TX-induced apoptosis in human ovarian cancer cells may be sustained by different events at the cell cycle-control level.