Cell cycle perturbations of platinum derivatives on two ovarian cancer cell lines

Multi-Chemotherapeutic Schedules Containing the pan-FGFR Inhibitor ARQ 087 are Safe and Show Antitumor Activity in Different Xenograft Models

ARQ 087 is a multi-tyrosine kinase inhibitor with potent activity against the FGFR receptor family, currently in Phase I clinical studies for the treatment of advanced solid tumors. The compound has a very safe profile and induces tumor regressions in FGFR-driven models. The feasibility of combining ARQ 087 with chemotherapy was investigated in FGFR deregulated human xenografts. Nude mice were transplanted subcutaneously with H1581, and when tumor masses reached 150 mg, were randomized to receive vehicle, ARQ 087, paclitaxel, carboplatin as single agents or in combination. Similar experimental conditions were applied in nude mice bearing SNU16 and MFE296 xenografts, with the inclusion of capecitabine in the former xenograft model. In the different xenograft models, the drugs given as single agents ranged from very active to partially active. The double combinations were more active than the single ones, but the triple combinations were the most active. In particular, the combination of ARQ 087 + paclitaxel + carboplatin in H1581 bearing mice was able to induce tumor regression in all the mice, with 6/8 mice tumor free at day 140 after tumor transplant. Of note, no toxic deaths nor premature stopping or delaying of drug administration were observed. The data herein reported demonstrated the feasibility of using xenografts models for poli-chemotherapeutic trials mimicking the best standard of care in treatment of specific tumor type and that ARQ 087, a new pan-FGFR inhibitor, can be safely combined with standard cytotoxic chemotherapeutic drugs with apparently no sign of cumulative toxicity and an associated increased antitumor effect.

Mirvetuximab Soravtansine (IMGN853), a Folate Receptor Alpha-Targeting Antibody-Drug Conjugate, Potentiates the Activity of Standard of Care Therapeutics in Ovarian Cancer Models

Elevated folate receptor alpha (FRα) expression is characteristic of epithelial ovarian cancer (EOC), thus establishing this receptor as a candidate target for the development of novel therapeutics to treat this disease. Mirvetuximab soravtansine (IMGN853) is an antibody-drug conjugate (ADC) that targets FRα for tumor-directed delivery of the maytansinoid DM4, a potent agent that induces mitotic arrest by suppressing microtubule dynamics. Here, combinations of IMGN853 with approved therapeutics were evaluated in preclinical models of EOC. Combinations of IMGN853 with carboplatin or doxorubicin resulted in synergistic antiproliferative effects in the IGROV-1 ovarian cancer cell line in vitro. IMGN853 potentiated the cytotoxic activity of carboplatin via growth arrest and augmented DNA damage; cell cycle perturbations were also observed in cells treated with the IMGN853/doxorubicin combination. These benefits translated into improved antitumor activity in patient-derived xenograft models in vivo in both the platinum-sensitive (IMGN853/carboplatin) and platinum-resistant (IMGN853/pegylated liposomal doxorubicin) settings. IMGN853 co-treatment also improved the in vivo efficacy of bevacizumab in platinum-resistant EOC models, with combination regimens causing significant regressions and complete responses in the majority of tumor-bearing mice. Histological analysis of OV-90 ovarian xenograft tumors revealed that concurrent administration of IMGN853 and bevacizumab caused rapid disruption of tumor microvasculature and extensive necrosis, underscoring the superior bioactivity profile of the combination regimen. Overall, these demonstrations of combinatorial benefit conferred by the addition of the first FRα-targeting ADC to established therapies provide a compelling framework for the potential application of IMGN853 in the treatment of patients with advanced ovarian cancer.

Purine Nucleoside Phosphorylase mediated molecular chemotherapy and conventional chemotherapy: a tangible union against chemoresistant cancer

BACKGROUND

Late stage Ovarian Cancer is essentially incurable primarily due to late diagnosis and its inherent heterogeneity. Single agent treatments are inadequate and generally lead to severe side effects at therapeutic doses. It is crucial to develop clinically relevant novel combination regimens involving synergistic modalities that target a wider repertoire of cells and lead to lowered individual doses. Stemming from this premise, this is the first report of two- and three-way synergies between Adenovirus-mediated Purine Nucleoside Phosphorylase based gene directed enzyme prodrug therapy (PNP-GDEPT), docetaxel and/or carboplatin in multidrug-resistant ovarian cancer cells.

METHODS

The effects of PNP-GDEPT on different cellular processes were determined using Shotgun Proteomics analyses. The in vitro cell growth inhibition in differentially treated drug resistant human ovarian cancer cell lines was established using a cell-viability assay. The extent of synergy, additivity, or antagonism between treatments was evaluated using CalcuSyn statistical analyses. The involvement of apoptosis and implicated proteins in effects of different treatments was established using flow cytometry based detection of M30 (an early marker of apoptosis), cell cycle analyses and finally western blot based analyses.

RESULTS

Efficacy of the trimodal treatment was significantly greater than that achieved with bimodal- or individual treatments with potential for 10-50 fold dose reduction compared to that required for individual treatments. Of note was the marked enhancement in apoptosis that specifically accompanied the combinations that included PNP-GDEPT and accordingly correlated with a shift in the expression of anti- and pro-apoptotic proteins. PNP-GDEPT mediated enhancement of apoptosis was reinforced by cell cycle analyses. Proteomic analyses of PNP-GDEPT treated cells indicated a dowregulation of proteins involved in oncogenesis or cancer drug resistance in treated cells with accompanying upregulation of apoptotic- and tumour- suppressor proteins.

CONCLUSION

Inclusion of PNP-GDEPT in regular chemotherapy regimens can lead to significant enhancement of the cancer cell susceptibility to the combined treatment. Overall, these data will underpin the development of regimens that can benefit patients with late stage ovarian cancer leading to significantly improved efficacy and increased quality of life.

Novel irreversible small molecule inhibitors of replication protein A display single-agent activity and synergize with cisplatin

Replication protein A (RPA) is a single-strand DNA-binding protein with essential roles in DNA replication, recombination, and repair. It is necessary for the formation of the preincision complex that is required for proper incision of damaged DNA nucleotides during DNA repair. We have previously identified small molecule inhibitors (SMI) with the ability to disrupt RPA-binding activity to ssDNA. Further characterization of these RPA inhibitors was done using both lung and ovarian cancer cell lines. Lung cancer cell lines showed increased apoptotic cell death following treatment with the SMI MCI13E, with IC(50) values of approximately 5 μmol/L. The ovarian cancer cell line A2780 and the p53-null lung cancer cell line H1299 were particularly sensitive to MCI13E treatment, with IC(50) values less than 3 μmol/L. Furthermore, a cell-cycle effect was observed in lung cancer cell lines that resulted in a lengthening of either G(1) or S-phases of the cell cycle following single-agent treatment. Sequential treatment with MCI13E and cisplatin resulted in synergism. Overall, these data suggest that decreasing DNA-binding activity of RPA via a SMI may disrupt the role of RPA in cell-cycle regulation. Thus, SMIs of RPA hold the potential to be used as single-agent chemotherapeutics or in combination with current chemotherapeutic regimens to increase efficacy.

The molecular basis of synergism between carboplatin and ABT-737 therapy targeting ovarian carcinomas

Resistance to standard chemotherapy (carboplatin + paclitaxel) is one of the leading causes of therapeutic failure in ovarian carcinomas. Emergence of chemoresistance has been shown to be mediated in part by members of the Bcl family of proteins including the antiapoptotic protein Bcl-x(L), whose expression is correlated with shorter disease-free intervals in recurrent disease. ABT-737 is an example of one of the first small-molecule inhibitors of Bcl-2/Bcl-x(L) that has been shown to increase the sensitivity of ovarian cancer cells to carboplatin. To exploit the therapeutic potential of these two drugs and predict optimal doses and dose scheduling, it is essential to understand the molecular basis of their synergistic action. Here, we build and calibrate a mathematical model of ABT-737 and carboplatin action on an ovarian cancer cell line (IGROV-1). The model suggests that carboplatin treatment primes cells for ABT-737 therapy because of an increased dependence of cells with DNA damage on Bcl-x(L) for survival. Numerical simulations predict the existence of a threshold of Bcl-x(L) below which these cells are unable to recover. Furthermore, co- plus posttreatment of ABT-737 with carboplatin is predicted to be the best strategy to maximize synergism between these two drugs. A critical challenge in chemotherapy is to strike a balance between maximizing cell-kill while minimizing patient drug load. We show that the model can be used to compute minimal doses required for any desired fraction of cell kill. These results underscore the potential of the modeling work presented here as a valuable quantitative tool to aid in the translation of novel drugs such as ABT-737 from the experimental to clinical setting and highlight the need for close collaboration between modelers and experimental scientists.

Increase the cisplatin cytotoxicity and cisplatin-induced DNA damage in HepG2 cells by XRCC1 abrogation related mechanisms

Cisplatin is one of the most potent chemotherapeutic anticancer drugs for the treatment of various cancers. The cytotoxic action of the drug is often thought to be associated with its ability to bind DNA to form cisplatin-DNA adducts. Impaired DNA repair processes including base excision repair (BER) play important roles on its cytotoxicity. XRCC1 is a key protein known to play a central role at an early stage in the BER pathway. However, whether XRCC1 contributes to decrease the cisplatin cytotoxicity and cisplatin-induced DNA damage in HepG2 still remains unknown. Hence, the purpose of this study was to explore whether abrogation of XRCC1 gene expression by short hairpin RNAs (shRNA) could reduce DNA repair and thus sensitize liver cancer cells to cisplatin. We abrogated the XRCC1 gene in HepG2 cell using shRNA transfection. Cell viability was measured by MTT assay and clonogenicity assay. Comet assay was used to detect the DNA damage induced by cisplatin. The host cell reactivation was employed to assess the DNA repair capacity of cisplatin-damaged luciferase reporter plasmid. Flow cytometry analysis was used to determine cisplatin-induced apoptosis, cell cycle and reactive oxygen species (ROS). The results showed that abrogation of XRCC1 could sensitize HepG2 cells to cisplatin. This enhanced cytotoxicity could be attributed to the increased DNA damage and reduced DNA repair capacity. Increasing cell cycle arrest and intracellular ROS production lead to more tumor cell apoptosis and then enhanced the cisplatin cytotoxicity. Our results suggested that the cisplatin cytotoxicity may increase by targeting inhibition of XRCC1.

The herb medicine formula "Yang Wei Kang Liu" improves the survival of late stage gastric cancer patients and induces the apoptosis of human gastric cancer cell line through Fas/Fas ligand and Bax/Bcl-2 pathways

The herb medicine formula "Yang Wei Kang Liu" (YWKLF) has been used to inhibit the metastasis of human gastric cancer to prolong patient survival. In this study, we evaluated the effect of combination of chemotherapy with YWKLF on the survival of stage IV gastric cancer patients and the potential mechanisms of YWKLF by focusing on its capacity to activate apoptotic pathways in human gastric cancer cell line MGC-803. We found that combination of chemotherapy with oral administration of YWKLF significantly increased the survival of stage IV gastric cancer patients. In an approach of "serum pharmacology" in which sera were collected from rabbits orally administered with YWKLF and examined for their anti-tumor cell activity in vitro, we observed that sera from rabbits administered with YWKLF induced the apoptosis of MGC-803 cells by causing the loss of mitochondrial membrane potential, increasing the expression of Fas protein and Bax mRNA, as well as down-regulating Fas-L mRNA. Our results suggest that activation of major pro-apoptotic pathways may account for the anti-gastric cancer activity of YWKLF, which may provide a basis for isolation and identification of more highly effective anti-cancer components.

Trans-platinum(II) complexes with cyclohexylamine as expectator ligand induce necrosis in tumour cells by inhibiting DNA synthesis and RNA transcription

BACKGROUND

Enhanced removal of cisplatin-DNA adducts has been reported as one of main causes of cell resistance to cisplatin. This particular resistance mechanism may be circumvented by platinum complexes that bind differently to DNA. One line of work is focussed on trans platinum complexes, some of which exhibit antitumour activity similar to or even higher than that of their cis counterparts.

METHODS

We synthesised new trans platinum complexes, trans-[PtCl2(cyclohexylamine)(dimethylamine)] and trans-[PtCl2(OH)2(cyclohexylamine)(dimethylamine)], previously evaluated as cytotoxic agents towards different cancer and normal cell lines. These trans platinum compounds were highly effective against a panel of tumoral cell lines either sensitive to or with acquired resistance to cisplatin.

RESULTS

In the present work we examined the mechanisms induced by these compounds to cause tumour cells toxicity. We have found that these compounds induced a complete blockade at the S phase of the cell cycle inhibiting total mRNA transcription and precluding p53 activation.

CONCLUSION

In contrast to other DNA-damaging agents, these compounds do not induce senescence-associated permanent arrest. Furthermore, only a small percentage of these cells enter into apoptosis, with most of the population dying by a necrosis-like mechanism.

The role of AtMUS81 in interference-insensitive crossovers in A. thaliana

MUS81 is conserved among plants, animals, and fungi and is known to be involved in mitotic DNA damage repair and meiotic recombination. Here we present a functional characterization of the Arabidopsis thaliana homolog AtMUS81, which has a role in both mitotic and meiotic cells. The AtMUS81 transcript is produced in all tissues, but is elevated greater than 9-fold in the anthers and its levels are increased in response to gamma radiation and methyl methanesulfonate treatment. An Atmus81 transfer-DNA insertion mutant shows increased sensitivity to a wide range of DNA-damaging agents, confirming its role in mitotically proliferating cells. To examine its role in meiosis, we employed a pollen tetrad–based visual assay. Data from genetic intervals on Chromosomes 1 and 3 show that Atmus81 mutants have a moderate decrease in meiotic recombination. Importantly, measurements of recombination in a pair of adjacent intervals on Chromosome 5 demonstrate that the remaining crossovers in Atmus81 are interference sensitive, and that interference levels in the Atmus81 mutant are significantly greater than those in wild type. These data are consistent with the hypothesis that AtMUS81 is involved in a secondary subset of meiotic crossovers that are interference insensitive.

Meiosis is a specialized type of cell division in which one diploid progenitor cell divides into four haploid cells that are subsequently used for fertilization during sexual reproduction. During meiosis, chromosomes pair, synapse, and exchange genetic information, all of which are required for proper chromosome segregation during subsequent stages. Failure to properly segregate meiotic chromosomes often leads to genetic defects such as aneuploidy. Using the model plant A. thaliana, we have developed a powerful system for the visual analysis of meiotic recombination directly in the pollen, in which the four products of individual meioses are fused together in a tetrad. We have used this system to characterize the gene AtMUS81 and show that Atmus81 mutants have a moderate reduction in meiotic crossovers and are sensitive to a wide range of DNA-damaging agents. Importantly, the remaining crossovers in Atmus81still exhibit crossover interference, a phenomenon whereby one crossover inhibits the occurrence of other nearby crossovers. Our results suggest that AtMUS81 mediates a subset of meiotic recombination events in Arabidopsis that are insensitive to crossover interference.

Synergistic effect of combining paeonol and cisplatin on apoptotic induction of human hepatoma cell lines

AIM

To investigate whether paeonol (Pae) has synergistic effects with cisplatin (CDDP) on the growth-inhibition and apoptosis-induction of human hepatoma cell lines HepG2 and SMMC-7721.

METHODS

The cytotoxic effect of drugs was measured by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-tetrazolium bromide assay. The coefficient of drug interaction was used to analyze the nature of drug interactions. Morphological changes were observed by acridine orange fluorescence staining. Cell cycle and the apoptosis rate were detected by flow cytometry. Bcl-2 and Bax expression were assayed by immunohistochemical staining.

RESULTS

Pae or CDDP had antiproliferative effect on the 2 cell lines in a dose-dependent manner, with different sensitivities to drugs. More interestingly, a synergistic inhibitory effect on the viability of the 2 cell lines was observed after treatment with a combination of Pae (15.63, 31.25, and 62.5 mg/L) with various concentrations of CDDP. Further study showed typical morphological changes of apoptosis if the cells were exposed to the two agents for 24 h. The apoptotic rate of the cells with combination treatment was significantly higher than that of cells treated with Pae or CDDP alone. The expression of Bcl-2 decreased and that of Bax increased in the treated groups, especially in the combination group, with the ratio of Bcl-2/Bax decreasing correspondingly. Additionally, a combination of Pae with CDDP resulted in a stronger S phase arrest, compared with Pae or CDDP alone.

CONCLUSION

Pae, in combination with CDDP, had a significantly synergistic growth-inhibitory and apoptosis-inducing effect on the 2 human hepatoma cell lines, which may be useful in hepatoma treatment.

Different cell cycle modulation following treatment of human ovarian carcinoma cells with a new platinum(IV) complex vs cisplatin

Platinum (IV) derivative with adamantylamine-LA-12-represents a new generation of highly efficient anti-cancer drug derived from cisplatin and is currently in the final stage of phase I clinical trials. Understanding the specific mechanisms of its effects on cell cycle is necessary for defining the mode of action of LA-12. In this study, we characterized the ability of LA-12 to induce cell cycle perturbations in ovarian cancer cell line A2780 as compared to equitoxic cisplatin treatment. LA-12 induced a permanent accumulation of A2780 cells in S phase while cisplatin caused G2/M arrest at 24-h time point, where we also detected an increased expression of Gadd45alpha protein. Although both derivatives induced a rapid increase of p53 expression, this was not associated with a down-regulation of Mdm2 protein. Increased expression of p21(Cip1/WAF1) protein and its association with cyclins A and B1 suggested that this cyclin-dependent kinase inhibitor might contribute significantly to the observed perturbations of cell cycle. The results of this study provide insight into the mechanism of action of platinum-based derivative with adamantylamine on cell cycle in ovarian cancer cells. The differences between effects of LA-12 and cisplatin suggest that more attention should be paid to elucidation of modes of action of novel platinum(IV) complexes at cellular level.

Repression of cell cycle–related proteins by oxaliplatin but not cisplatin in human colon cancer cells

Oxaliplatin (Eloxatin) is a third-generation platinum derivative with an in vitro and in vivo spectrum of activity distinct from that of cisplatin, especially in colon cancer cells. Here, we studied the molecular basis of this difference on the HCT-116 human colon carcinoma cell line (mismatch repair-deficient, wild-type functional p53). Oxaliplatin inhibited HCT-116 cell proliferation with greater efficacy than cisplatin. At comparable concentrations, cisplatin slowed down the replication phase and activated the G2-M checkpoint, whereas oxaliplatin activated the G1-S checkpoint and completely blocked the G2-M transition. With the aim of finding oxaliplatin-specific target genes and mechanisms differing from those of cisplatin, we established the transcriptional signatures of both products on HCT-116 cells using microarray technology. Based on hierarchical clustering, we found that (a) many more genes were modulated by oxaliplatin compared with cisplatin and (b) among the 117 modulated genes, 79 were regulated similarly by both drugs and, in sharp contrast, 38 genes were dose dependently down-regulated by oxaliplatin and, conversely, up-regulated or unaffected by cisplatin. Interestingly, several cell cycle-related genes encoding proteins involved in DNA replication and G2-M progression belong to this latter group. RNA modulations, confirmed at the protein level, were in accordance with oxaliplatin- and cisplatin-induced cell cycle variations. Beyond the identification of genes affected by both drugs, the identified oxaliplatin-specific target genes could be useful as predictive markers for evaluating and comparing the efficacy and molecular pharmacology of platinum drugs.

Platinum(IV) complex with adamantylamine overcomes intrinsic resistance to cisplatin in ovarian cancer cells

OBJECTIVES

The resistance of tumor cells to cisplatin remains a major cause of treatment failure in cancer patients. In this study, the ability of Pt(IV) complex with adamantylamine-LA-12 and its reduced counterpart with lower oxidation state Pt(II)-LA-9 to overcome intrinsic cisplatin resistance was investigated.

METHODS

The ovarian adenocarcinoma SK-OV-3 cells were exposed to cisplatin, LA-9, or LA-12 for 72 h and the effects of drug concentrations that caused 10% or 50% inhibition of cell proliferation were determined. After 24-72 h of sustained exposure viability, apoptosis and inhibition of proliferation were analyzed. DNA synthesis and cell cycle analysis were performed simultaneously in order to determine the modulation of cell cycle after platinum complexes treatment.

RESULTS

Lung Resistance-related Protein (LRP/MVP) was detected in SK-OV-3 cells but not in the other two ovarian cancer lines with different sensitivity to cisplatin. LRP/MVP overexpression may be an important factor contributing to intrinsic cisplatin resistance. Interestingly, Pt(IV) complex-LA-12 had approximately 2.7-fold lower IC(50) concentration than LA-9 or cisplatin in SK-OV-3 cells. Moreover, LA-12 caused persistent accumulation of cells in S-phase of the cell cycle while LA-9 and cisplatin treatment-induced S-phase arrest was transient and shifted to G(2)/M-phase at later intervals. Apoptosis seemed to be not the dominant type of cell death caused by such the derivatives, but it was the most intensive after LA-12 treatment.

CONCLUSIONS

We found strong differences between effects of Pt(IV) complex-LA-12 and Pt(II) derivatives-LA-9 and cisplatin on cytokinetic parameters. Overall, LA-12 but not its reduced Pt(II) counterpart LA-9 is the compound effective in p53 null human ovarian cancer cells and it is able to overcome intrinsic cisplatin resistance in these cells.

A Phase I Trial of the Novel Farnesyl Protein Transferase Inhibitor, BMS-214662, in Combination with Paclitaxel and Carboplatin in Patients with Advanced Cancer

PURPOSE

This phase I study was conducted to determine the toxicities, pharmacokinetics, and pharmacodynamics of BMS-214662, a farnesyl transferase inhibitor, in combination with paclitaxel and carboplatin, in patients with advanced solid tumors.

EXPERIMENTAL DESIGN

Patients with solid tumors received one of six escalating dose levels of BMS-214662 infused over 1 hour given following paclitaxel and carboplatin on the first day of a 21-day cycle. Toxicities were graded by the National Cancer Institute common toxicity criteria and recorded as maximum grade per patient for each treatment cycle. Inhibition of farnesyl transferase activity in peripheral blood mononuclear cells (PBMCs) was evaluated. Accumulation of unfarnesylated HDJ-2 in PBMCs of patients was evaluated as a marker of farnesyl transferase inhibition by BMS-214662.

RESULTS

Thirty patients received 141 cycles of treatment through six dose levels. Dose-limiting toxicities were neutropenia, thrombocytopenia, nausea, and vomiting. There was no pharmacokinetic interaction between BMS-214662 and paclitaxel. The maximum tolerated dose was established as BMS-214662 (160 mg/m(2)), paclitaxel (225 mg/m(2)) and carboplatin (area under the curve = 6 on day 1), every 21 days. Inhibition of HDJ-2 farnesylation in PBMCs of patients was shown. One measurable partial response was observed in a patient with taxane-resistant esophageal cancer. There was partial regression of evaluable disease in two other patients (endometrial and ovarian cancer). Stable disease (> 4 cycles) occurred in eight other patients.

CONCLUSIONS

The combination of BMS-214662 with paclitaxel and carboplatin was well tolerated, with broad activity in solid tumors. There was no correlation between dose level and accumulation of unfarnesylated HDJ-2 in PBMCs nor tumor response.

Thermal enhancement of oxaliplatin-induced inhibition of cell proliferation and cell cycle progression in human carcinoma cell lines

Hyperthermia is used to treat intraperitoneal colorectal carcinomatosis. In this setting, the molecular effects of oxaliplatin and hyperthermia, in combination and alone, were deciphered in ovarian and colon cancer cells. The combined antiproliferative effects of hyperthermia and oxaliplatin (Eloxatine) on human IGROV-1 ovarian carcinoma, Caco-2 and HT-29 colon carcinoma cell lines were investigated by cell viability test, cell cycle analysis and modulation of expression of cell cycle-related proteins. Oxaliplatin inhibited growth of all cell lines in a dose-dependent manner. The efficacy of the drug was markedly enhanced by concurrent exposure to mild heat shock (1 h, 42 degree C). In IGROV-1 cells, a low concentration (15 microg/ml) of oxaliplatin in combination with hyperthermia induced a transient G2/M arrest. In both colon carcinoma cell lines, a G1/S arrest with a reduction of the G0/G1 population occurred. In IGROV-1 and Caco-2 cells, growth arrest was accompanied by apoptosis as suggested by the appearance of sub-G1 population. Time-course changes of cell cycle regulatory proteins levels revealed accumulation of cyclins A and B as well as of cdc2 and cdk2 upon exposure of IGROV-1 cells to hyperthermia and oxaliplatin. In this cell line, p53 appeared to be implicated in both G2/M arrest and apoptosis. G1/S arrest of HT-29 cells was linked to up-regulation of cyclin E and p27(Kip1) and accumulation of the hypophosphorylated form of pRB, whereas in Caco-2 cells only the hyperphosphorylated form was detected as well as a down-regulation of the proto-oncogene c-myc. Taken together, the results of these in vitro studies suggest that hyperthermia and oxaliplatin might elicit antiproliferative effects by modulating the expression of cell cycle regulatory proteins through different signalling pathways.

Time-dependent changes in factors involved in the apoptotic process in human ovarian cancer cells as a response to cisplatin

OBJECTIVES

Apoptosis is believed to be a major mechanism of cisplatin-induced cell death. We investigated the kinetics of apoptosis in four human ovarian cancer cell lines treated with cisplatin to obtain insight into the role and the behavior of a variety of factors involved in this process.

METHODS

The cell lines A2780, H134, and IGROV-1 (all wild-type p53) and OVCAR-3 (mutant p53) were exposed to cisplatin for 1 h and the antiproliferative effects were measured after 96 h. At various time points up to 96 h after the 1-h exposure to the individual 90% growth-inhibiting cisplatin concentrations, FACS analysis and May-Grünwald Giemsa staining were carried out to determine the extent of apoptosis. At the same time points protein expression levels of p53, p21/WAF1, Bax, and Bcl-2 and the activity of caspase-3 were measured. FACS analysis was also carried out to determine changes in cell cycle distribution as a response to cisplatin.

RESULTS

The four cell lines differed in sensitivity to cisplatin. A2780 was the most sensitive and IGROV-1 was the least sensitive. In contrast, IGROV-1 cells showed the highest percentage of apoptosis (30-40%), while A2780 had the lowest percentage (6-14%) (r = 0.99). The occurrence of apoptosis was not dependent on functional p53. Of interest, caspase-3 activity was in line with the percentage of apoptosis and preceded DNA fragmentation and the visualization of condensed nuclei. Wild-type p53 cells accumulated in the S phase, while OVCAR-3 arrested in the G2/M phase. The protein expression levels of p53, p21/WAF1, Bax, and Bcl-2 varied in time, but were not related to the apoptotic behavior of the cells. Upregulation of p53 was already evident before activation of caspase-3.

CONCLUSIONS

Time-dependent changes in the various factors involved in the apoptotic process induced by equitoxic doses of cisplatin vary strongly among the cell lines. Caspase-3 activation plays an important role in cisplatin-induced apoptosis and this precedes morphological changes. The ability of cells to enter apoptosis, however, does not seem to predict sensitivity to cisplatin.

Drug interactions and cytotoxic effects of paclitaxel in combination with carboplatin, epirubicin, gemcitabine or vinorelbine in breast cancer cell lines and tumor samples

The purpose of this study was to analyze the drug interactions of paclitaxel (PTX) with epirubicin (EPI), carboplatin (CBDCA), gemcitabine (GEM) and vinorelbine (VIN) in human breast cancer cells and compare the cytotoxic activity of each drug combination in primary breast cancer samples. These experiments were intended to identify the most active agents in combination with PTX, and to provide a preclinical rational for future clinical investigations in breast cancer. Multiple drug effect/combination index (CI) isobologram analysis was applied to combinations of PTX with either CBDCA, EPI, GEM or VIN in MCF-7, MDA-MB-231 and SK-BR-3 human breast cancer cell lines. Drug concentrations were limited to the ranges achievable in humans in vivo, and the drugs were applied simultaneously at fixed molar ratios for each drug combination. Interactions were assessed at multiple effect levels (IC10-IC90). Additionally, the cytotoxic activity of these combinations was assessed in tumor samples of 50 primary breast cancer patients, utilizing the ATP-tumorchemosensitivity assay (ATP-TCA). Drug interactions were shown to be strongly dose-related in the human breast cancer cell lines investigated. At clinically relevant concentrations, CBDCA/PTX demonstrated synergistic (MCF-7) or additive (MDA-MB-231, SK-BR-3) interactions, and EPI/PTX showed additive (SK-BR-3, MCF-7) and antagonistic (MDA-MB-231) interactions. GEM/PTX and VIN/PTX, however, demonstrated antagonism over multiple dose effect levels at clinically relevant drug concentrations in all three cell lines tested. At plasma peak concentrations, EPI/PTX, CBDCA/PTX, GEM/PTX and VIN/PTX achieved > or = 90% tumor growth inhibition in 93, 86, 63 and 50%, respectively, of primary breast cancer samples investigated with the ATP-TCA. Cumulative dose-response plots of primary breast cancer tumor cells responding in vitro with > or = 90% growth inhibition showed a strong dose dependence for both EPI/PTX and CBDCA/PTX. In conclusion, the current data indicate favorable drug interactions for CBDCA/PTX at clinically relevant drug concentrations in breast cancer cells, and demonstrate superior in vitro cytotoxicity of EPI/PTX and CBDCA/PTX compared to GEM/PTX and VIN/PTX in primary breast cancer cultures.

The nm23-H1 gene as a predictor of sensitivity to chemotherapeutic agents in oesophageal squamous cell carcinoma

Recently, nm23-H1, an anti-metastasis gene, has been reported to correlate with sensitivity to chemotherapeutic agents including cisplatin in human breast and ovarian carcinoma cells. The aim of this study was to evaluate a role for nm23-H1 in responsiveness to cisplatin-based chemotherapy in patients with oesophageal squamous cell carcinoma (OSCC). The expression of nm23-H1 protein was examined immunohistochemically in 32 eligible patients with OSCC who underwent adjuvant chemotherapy with cisplatin, etoposide, and 5-fluorouracil after tumour resection. Fifteen (46.9%) of 32 patients were positive for nm23-H1 staining and 17 (53.1%) were negative. Both disease-free survival and overall survival rates of nm23-H1-negative patients were significantly shorter than in nm23-H1-positive patients (P < 0.01 for both). There was no significant difference in clinicopathologic characteristics between nm23-H1-positive and nm23-H1-negative groups. Multivariate analysis also showed that nm23-H1 expression was the most significant factor for overall survival of OSCC patients included in this study (P = 0.0007). To further study the role of nm23-H1, a human OSCC cell line (YES-2) was transfected with a plasmid containing a fragment of the nm23-H1 cDNA in an antisense orientation. Reduced expression of nm23-H1 protein in the antisense-transfected (AS) clones was found by Western blot analysis as compared to wild-type YES-2 and YES-2/Neo (clone transfected with the neomycin resistance gene alone). MTT (3-(4,5-dimethyl-2-thiazol)-2,5-diphenyl-2H tetrazolium bromide) assay showed that reduced expression of the nm23-H1 protein in AS clones was consistent with the degree of increased resistance to cisplatin but not etoposide or 5-fluorouracil. These data support the conclusion that reduced expression of nm23-H1 may be associated with resistance to cisplatin, suggesting the value of nm23-H1 expression as a prognostic marker for OSCC patients who are to undergo cisplatin-based chemotherapy.

Cytokinetic effects of cisplatin on diverse human head and neck carcinomas in vitro: dependence on the tumor sensitivity to cisplatin

Studies performed with xenografted human head and neck carcinomas in vivo have demonstrated that the cytokinetic phenomena occurring under the influence of cisplatin closely correlate with the response of the tumors to therapy. The present paper analyses whether this correlation also exists in vitro. Four human head and neck carcinoma cell lines showing different degrees of sensitivity to cisplatin, as determined by the trypan blue exclusion assay, were investigated by flow cytometry at various intervals after administration of cisplatin. Early cell-cycle blockades in the S phase always reflected a high degree of cytostatic potency of cisplatin and were usually succeeded by a pronounced inhibition of tumor cell proliferation and a reduction of cell viability. In the case of a minimal response to therapy and in untreated control cultures of all four tumor lines, the relative number of S-phase cells continuously diminished during the observation period. These findings point to the S-phase blockade as the crucial cytokinetic effect of cisplatin preceding relevant growth reductions. This knowledge might support the development of a drug-response assay that could predict the sensitivity of individual patient tumors in vitro before the beginning of clinical cancer chemotherapy.

Long-term persistence and cytokinetics of human tumor cells in vitro following high-dose alkylating agent exposure

Relapse after high-dose alkylating agent therapy continues to be an important clinical issue. To begin to understand the characteristics of cells surviving alkylating agent exposure human MCF-7 breast carcinoma cells were exposed to a range of concentrations of melphalan or cis-diamminedichloroplatinum(II) and cell survival determined by colony formation over a time course of 4 weeks. When antitumor alkylating agent exposure killed 3-4 logs of cells as determined by surviving fraction after 1 week of colony formation a progressive increase in surviving fraction was evident over the 4-week course of the experiment. Many attached single cells with abnormal morphology were evident in these dishes; however, the colonies which arose over the 4-week observation time were made up of cells morphologically indistinguishable from the control cells. Cell cycle patterns in the cultures exposed to high concentrations of the antitumor alkylating agents indicated a block in G2/M but by 4 weeks post-drug exposure most had returned to a normal exponential growth pattern. When MCF-7 cells or human SW2 small cell lung cancer cells were exposed to a concentration of melphalan or cis-diamminedichloroplatinum(II) that killed 1-2 logs of cells followed by exposure to a concentration range of the same drug for 24 h or 7 days later resistance to the second drug exposure was evident in both cell lines. Using [14C]melphalan the uptake of the drug into MCF-7 cells pre-treated was compared. Decreased drug uptake did not appear to be a factor in resistance to melphalan observed upon re-exposure to the drug. The potential clinical implications of these findings is discussed.