Cellular efflux pump and interaction between cisplatin and paclitaxel in ovarian cancer cells

OBJECTIVE: The aim of this study was to evaluate the combination effect of paclitaxel (PTX) and cisplatin (CDDP) and to determine the mechanisms of interaction between these agents. METHODS AND RESULTS: We used human ovarian adenocarcinoma cell lines, namely a parent cell line (KF), a CDDP-resistant cell line (KFr) and a PTX-resistant cell line (KFTx).The combination effect of PTX and CDDP was synergistic on KF and KFTx and additive on KFr. The incidence of anaphase or telophase, evaluated by immunofluorescence microscopy, decreased with PTX and significantly decreased with PTX and CDDP in KF and KFTx. The concentration of PTX, which was measured by high-performance liquid chromatography, was higher in KF and KFTx cells treated with a combination of PTX and CDDP than those treated with PTX alone. Multidrug resistance gene mRNA appeared in KFTx and its expression decreased after exposure to PTX and CDDP. After exposure to CDDP, the expression of multidrug resistance-associated protein (MRP) and the concentration of glutathione increased in KF, but not in KFr or KFTx. MRP expression slightly increased in KF and KFTx after exposure to PTX. In contrast, its expression decreased in KFr. CONCLUSION: The present study suggests that CDDP enhances PTX accumulation and that the interaction of these agents is synergistic in CDDP-sensitive cells.     

Tubulin from paclitaxel-resistant cells as a probe for novel antimicrotubule agents

Purpose: Treatment with paclitaxel (PTX) can lead to the appearance of drug resistance with accompanying changes in tubulin. The purpose of this study was to develop an assay for microtubule-active agents that are able to circumvent changes in tubulin that result in acquired resistance to paclitaxel. Methods: The assay measured the promotion of microtubule polymerization when target agents were added to solutions containing tubulin purified from cultured cells. Tubulin was prepared from PTX-sensitive 1A9 ovarian carcinoma cells and from a PTX-resistant clone. Polymerization was monitored spectrophotometrically and validated by electron microscopy. Results: Exposure of tubulin isolated from PTX-sensitive 1A9 ovarian carcinoma cells to substoichiometric PTX resulted in polymerization equivalent to that observed with brain tubulin. In contrast, tubulin from a PTX-resistant 1A9 clone failed to polymerize under identical conditions. If a C-2-modified analog of PTX (2-debenzoyl-2-(m-azidobenzoyl)paclitaxel) was substituted for PTX in the same experiment, the tubulins from both sensitive and resistant cells polymerized as well as brain tubulin. As predicted from these results, the PTX analog was nearly as cytotoxic to the PTX-resistant cells as it was to the parental cells: the relative resistance of the resistant cells compared to the parental is only 3–5-fold for the PTX analog versus 25–30-fold for PTX. Conclusion: Polymerization of purified tubulin from the paclitaxel-resistant cells provided an assay for agents able to circumvent the tubulin alterations that result in acquired paclitaxel resistance. Received: 30 October 1996 / Accepted: 9 December 1996     

Mechanisms of paclitaxel-induced apoptosis in an ovarian cancer cell line and its paclitaxel-resistant clone

BACKGROUND: To understand the complicated network of paclitaxel (PTX)-induced apoptosis pathways and to elucidate mechanisms of drug resistance in ovarian cancer, we looked at PTX-induced apoptosis by using cDNA microarray. We also quantitated the changes in apoptosis-related proteins in the process of apoptosis. METHODS: An ovarian cancer cell line KF, and its PTX-resistant clone KFTX, were treated with PTX or carboplatin (CBDCA). After exposure to PTX or CBDCA, the induction of apoptosis was examined by internucleosomal DNA fragmentation. Changes in mRNA expression after 12 h of exposure to PTX were studied using cDNA microarray and RT-PCR. Changes in P53 and Bcl-2 levels were also measured over 24 h by ELISA. RESULTS: With increased doses of PTX or CBDCA, an increase in apoptosis was noted in both cell lines. cDNA microarray revealed that PTX treatment upregulated expression of caspase 1, 2, 3, 4, 6, 9, 10, their activator apaf-1, and stress reaction-related genes, gadd34, gadd153 in KF, although most of them were unchanged or downregulated in KFTX. bag-1 and hsc70 were markedly upregulated in KFTX. p53 and bcl-2 were not upregulated in either cell line. Results from protein studies also supported the cDNA microarray data. CONCLUSIONS: p53-independent mitochondrial pathways and stress-reaction-induced pathways play critical roles in PTX-induced apoptosis in ovarian cancer cells. Suppression of those pathways and upregulation of bag-1 and hsp-70 played an important role in acquiring resistance to PTX.     

Sensitivity to paclitaxel is not related to p53-dependent apoptosis in ovarian cancer cells

We conducted this study to determine whether the sensitivity of ovarian cancer cells to paclitaxel (PTX) relates to cells undergoing p53-dependent apoptosis. Human ovarian adenocarcinoma cell lines (SK-OV-3, KF and KP cells) were used in this study. In SK-OV-3 and KP cells, which have a homozygous deletion of the TP53 gene, wild-type TP53 gene-transduction markedly enhanced the sensitivity to cisplatin (CDDP), but did not enhance the sensitivity to PTX. In all cells, the apoptotic index was increased by CDDP or PTX. After exposure to CDDP, p53 and Bax protein expression increased and Bcl-xL expression decreased in the KF cells and TP53 gene-transducted SK-OV-3 cells. However, these proteins did not change in KP cells. Therefore, the role of p53 in CDDP-induced apoptosis depends upon the cell type. In contrast, TP53 gene status did not correlate with PTX-induced cytotoxicity in any of the cell lines with differing apoptotic pathways. In conclusion, the sensitivity to PTX may not be related to p53-dependent apoptosis in ovarian cancer cells.     

Induction of a multifactorial resistance phenotype by high paclitaxel selective pressure in a human ovarian carcinoma cell line

Paclitaxel (PTX) is a potent anti-neoplastic agent that is highly effective in treating ovarian cancer. Nevertheless, the emergence of PTX resistance has limited the control of this disease. To gain insight into the molecular alterations accompanying drug resistance in ovarian cancer, we generated a new stable PTX-resistant ovarian carcinoma cell line. CABA I cells, which display an intrinsic PTX resistance (IC50 = 800 ng/ml), were subjected to continuous exposure to PTX. From the residual surviving cells, the highly PTX-resistant line CABA-PTX (IC50 = 256000 ng/ml) was generated and stably maintained in vitro. Analysis of beta-tubulin expression indicated that only the HM40 and Hbeta9 isotypes were expressed in both parental and resistant cells. No specific point mutations in the HM40 were detected in either cell line, but expression levels of this isotype were significantly reduced (40%) in CABA-PTX cells. Hbeta9 levels were unchanged. In those cells, PTX resistance was associated with cross-resistance to vinblastine but not to methotrexate or 5-fluorouracil. Verapamil treatment did not reverse the intrinsic drug resistance of parental cells, but partially modulated the sensitivity of CABA-PTX cells to PTX and induced total sensitivity to vinblastine. No changes in the cell surface expression of the drug efflux pumps MRP1, MRP2 and P-glycoprotein were observed. PTX influx, monitored using a fluorescent drug derivative, was significantly reduced and delayed in CABA-PTX cells as compared to the parental cells. Together, these findings suggest that more than one mechanism is involved in PTX resistance, making CABA-PTX cell line a potentially valuable in vitro tool to study multifactorial acquired drug resistance in ovarian cancer.     

Dysregulation of miR-106a and miR-591 confers paclitaxel resistance to ovarian cancer

Background:

MicroRNAs are noncoding regulatory RNAs strongly implicated in carcinogenesis, cell survival, and chemosensitivity. Here, microRNAs associated with chemoresistance in ovarian carcinoma, the most lethal of gynaecological malignancies, were identified and their functional effects in chemoresistant ovarian cancer cells were assessed.

Methods:

MicroRNA expression in paclitaxel (PTX)-resistant SKpac sublines was compared with that of the PTX-sensitive, parental SKOV3 ovarian cancer cell line using microarray and qRT–PCR. The function of differentially expressed microRNAs in chemoresistant ovarian cancer was further evaluated by apoptosis, cell proliferation, and migration assays.

Results:

Upregulation of miR-106a and downregulation of miR-591 were associated with PTX resistance in ovarian cancer cells and human tumour samples. Transfection with anti-miR-106a or pre-miR-591 resensitized PTX-resistant SKpac cells to PTX by enhancing apoptosis (23 and 42% increase), and inhibited their cell migration (43 and 56% decrease) and proliferation (64 and 65% decrease). Furthermore, ZEB1 was identified as a novel target gene of miR-591, and BCL10 and caspase-7 were target genes of miR-106a, as identified by immunoblotting and luciferase assay.

Conclusion:

MiR-106a and miR-591 have important roles in conferring PTX resistance to ovarian cancer cells. Modulation of these microRNAs resensitizes PTX-resistant cancer cells by targeting BCL10, caspase-7, and ZEB1.     

Combinations of pacliataxel and vinblastine and their effects on tublin polymerization and cellular cytotoxicity: Characterization of a synergistic schedule

Paclitaxel (PTX) and vinblastine (VBL) represent 2 classes of drugs that target tubulin but have separate binding properties and opposing mechanisms of action. To evaluate the potential use of these agents together in a chemotherapeutic regimen, we investigated their effects on the dynamics of tubulin polymerization and cellular cytotoxicity, when administered singly or in combination. In human epidermoid carcinoma KB cells and MCF-7 breast carcinoma cells, we observed a time- and dose-dependent effect on cytoskeletal dynamics for both PTX and VBL. Tubulin polymerization induced by PTX was stable for more than 24 hr. When PTX treatment was followed by VBL, a time- and dose-dependent reversal of tubulin polymerization was observed. In contrast, rapid tubulin polymerization occurred when VBL was followed by PTX. When both agents were added simultaneously, a diminution of PTX-induced tubulin polymerization was observed with increasing doses of VBL; a maximum reduction was achieved when equal concentrations were used. Examination of the tubulin pattern by immunofluorescence in MCF-7 breast cancer cells confirmed and extended our findings. Bundle formation followed treatment with PTX. Addition of increasing concentrations of VBL prevented bundling; however, the normal cytoskeletal architecture was not restored. Cytotoxicity studies carried out using the median dose effect principles and the combination index analysis showed synergism when VBL and PTX were administered sequentially and antagonism for simultaneous administration. Our results demonstrate changes in tubulin dynamics following drug treatment and provide a rationale for combined PTX/VBL therapy after careful evaluation of the schedule of administration. Int. J. Cancer 75:57–63, 1998. Published 1998 Wiley-Liss, Inc.     

A retrospective study of docetaxel or paclitaxel in patients with advanced or recurrent esophageal squamous cell carcinoma who previously received fluoropyrimidine- and platinum-based chemotherapy

Introduction

Fluoropyrimidine plus platinum (FP)-based chemotherapy has been widely used as a first-line regimen for advanced or recurrent esophageal cancer, and taxanes have shown efficacy after FP-based chemotherapy, but there is no standard regimen for second-line chemotherapy (SLC). We retrospectively investigated the clinical features of taxane therapy in SLC for esophageal squamous cell carcinoma (ESCC).

Methods

The selection criteria were pathologically proven ESCC; advanced or recurrent disease previously treated with FP at our hospital; performance status (PS) 0–2; and adequate organ function. Docetaxel (DTX) was administered 3-weekly at 70 mg/m². Paclitaxel (PTX) was administered at 100 mg/m² weekly for 6 weeks, with 1 week’s rest.

Results

The analysis covered 163 patients from August 2006 to June 2012. Median age was 64 years (range 37–83: DTX group 132 patients and PTX group 31). Progression-free survival and median overall survival (OS) were 2.3 and 6.1 months, respectively, with PTX and 2.3 and 5.3 months with DTX. Response rates were 20.7 % for PTX and 5.9 % for DTX. The rate of grades 3–4 neutropenia was higher with DTX (32.6 %) than with PTX (16.1 %). Grade 3 febrile neutropenia was seen in 6.1 % of DTX recipients but in no PTX group. According to multivariate analyses of OS, PS 2, number of metastatic sites ≧2, and CRP ≧1 mg/dL were independent predictors of poor prognosis.

Conclusions

PTX and DTX were both effective in SLC for ESCC, but their toxicity profiles differed. In terms of febrile neutropenia, PTX seems more appropriate.     

CXCL8 Facilitates the Survival and Paclitaxel-Resistance of Triple-Negative Breast Cancers

BackgroundThis study aimed to demonstrate CXCL8 expression in TNBC tissues and cells, and elucidate the functional mechanism of CXCL8 in paclitaxel (PTX)-resistant TNBC.MethodsBioinformatics analysis was performed to identify differentially expressed genes (DEGs) in PTX-resistant TNBC using publicly available data from the GEO, TCGA and METABRIC databases. STRING was used to identify the interacting partners of CXCL8. Kaplan-Meier software was used to analyze the relationship between CXCL8 expression and patient survival rate. The protein expression and distribution of CXCL8 were examined by immunohistochemistry, MTT assay and colony formation assay were performed to determine cell viability of TNBC cells treated with PTX. Western blotting was used to assess the levels of drug resistance and apoptosis-related proteins. GO-KEGG analysis was conducted on the DEGs to identify enriched signaling pathways.ResultsThe results of bioinformatics analysis demonstrated a high expression of CXCL8 in TNBC tissues and cells. Kaplan-Meier analysis revealed that the expression of CXCL8 is associated with poor prognosis. CXCL8 was upregulated in PTX-resistant TNBC cells. Knockdown of CXCL8 increased the sensitivity of TNBC cells to PTX. Mechanically, CXCL8 deficiency regulated PTX resistance in TNBC cells via cell apoptosis signaling pathway.ConclusionOur work demonstrated that CXCL8 may be a potential molecule to be targeted for the treatment of PTX-resistant TNBC.     

The uptake of paclitaxel and docetaxel into ex vivo porcine bladder tissue from polymeric micelle formulations

Superficial bladder cancer occurs in the urothelial layer of the bladder and is usually treated by transurethral resection and chemotherapy. Although the bladder is well suited for intravesical chemotherapy, effective drug delivery is restricted by urine dilution and poor drug uptake by bladder tissues during a 2 h instillation. In this study, freshly excised pig bladder sections were mounted on Franz diffusion cells and treated with anticancer drugs paclitaxel (PTX) and docetaxel (DTX) formulated in diblock copolymer (methoxy poly(ethylene glycol)-block-poly (D,L-lactic acid) (MePEG-PDLLA) and methoxy poly(ethylene glycol)-block-poly(caprolactone) (MePEG-PCL) nanoparticles for 2 h. The bladder sections were then frozen, cryosectioned (60-μm sections) and the amount of ³H drug taken up into each section was determined using liquid scintillation counting. Tissue concentration versus tissue depth profiles were obtained for all drug formulations and drug exposure obtained from area-under-the-curve (AUC) calculations. PTX or DTX loaded in MePEG-PDLLA micelles produced significantly higher urothelial tissue levels and greater bladder wall exposures compared to their commercial formulations, Cremophor EL/ethanol (PTX) or Tween 80 (DTX). The results of this study support the use of diblock copolymer micellar PTX or DTX formulations as they allow for improved drug penetration of bladder tissues compared to commercial formulations for taxane delivery to superficial bladder tumors.     

Bcl-2 family inhibition sensitizes human prostate cancer cells to docetaxel and promotes unexpected apoptosis under caspase-9 inhibition

Docetaxel (DTX) is a useful chemotherapeutic drug for the treatment of hormone-refractory prostate cancer. However, emergence of DTX resistance has been a therapeutic hurdle. In this study, we investigated the effect of combining DTX with Bcl-2 family inhibitors using human prostate cancer cell lines (PC3, LNCaP, and DU145 cells). PC3 cells were less sensitive to DTX than were the other two cell lines. In contrast to ABT-199, which inhibits Bcl-2 and Bcl-w, both ABT-263 and ABT-737, which inhibit Bcl-2, Bcl-xL, and Bcl-w, significantly augmented the antitumor effect of DTX on PC3 cells. ABT-263 also enhanced the antitumor effect of DTX on a DTX-resistant PC3 variant cell line. The antitumor effect of ABT-263 was due mainly to its inhibitory effect on Bcl-xL. In a xenograft mouse model, DTX and ABT-737 combination therapy significantly inhibited PC3 tumor growth. Interestingly, although ABT-263 activated caspase-9 in PC3 cells, inhibition of caspase-9 unexpectedly promoted ABT-263-induced apoptosis in a caspase- 8-dependent manner. This augmented apoptosis was also observed in LNCaP cells. These findings indicate that Bcl-xL inhibition can sensitize DTX-resistant prostate cancer cells to DTX, and they reveal a unique apoptotic pathway in which antagonism of Bcl-2 family members in caspase-9-inhibited prostate cancer cells triggers caspase-8-dependent apoptosis.     

Cellular bases of the antitumor activity of the novel taxane IDN 5109 (BAY59-8862) on hormone-refractory prostate cancer.

Taxane-based therapies appear to have a significant efficacy in clinical trials on hormone-refractory prostate carcinoma. In the present study, we investigated the cellular response of androgen-independent prostate carcinoma cell lines to the novel taxane IDN 5109 (BAY 59-8862) and evaluated its antitumor activity. In previous preclinical studies, this new paclitaxel (PTX) analogue was characterized by high tolerability and antitumor efficacy, ability to overcome multidrug resistance, and activity by oral administration. Upon treatment, DU145 and PC3 prostate carcinoma cell lines underwent a transient mitotic arrest. This was followed by G1 arrest and rapid occurrence of apoptosis in DU145 cells, whereas in PC3 cells, which are defective for the postmitotic checkpoint, a slow cell death was preceded by DNA endoreduplication. At the biochemical level, such events were associated with tubulin polymerization, activation of the mitosis-promoting factor, and phosphorylation of Bcl-X(L)/Bcl-2/Raf-1. In addition, IDN 5109 shared with PTX the ability to down-regulate the expression of the two potent angiogenic factors vascular endothelial growth factor and basic fibroblast growth factor. These findings indicated that IDN 5109 affected the same pathways involved in the cellular response to PTX and suggested that an antiangiogenic effect mediated by inhibition of paracrine stimulation of endothelial cells might contribute to the antitumor effect of both drugs. In in vivo experiments, the new taxane displayed a superior and more persistent effect compared with PTX against DU145 tumor xenografts. Such an effect was associated with pronounced reduction of the tumor microvessel density, superior to that achieved by PTX. These results support a potential therapeutic advantage of IDN 5109 over PTX against hormone-refractory prostate carcinoma.     

Evaluations of combination MDR-1 gene silencing and paclitaxel administration in biodegradable polymeric nanoparticle formulations to overcome multidrug resistance in cancer cells

In this study, the effect of MDR-1 gene silencing, using small interfering RNA (siRNA), and paclitaxel (PTX) co-therapy in overcoming tumor multidrug resistance was examined. Poly(ethylene oxide)-modified poly(beta-amino ester) (PEO-PbAE) and PEO-modified poly(epsilon-caprolactone) (PEO-PCL) nanoparticles were formulated to efficiently encapsulate MDR-1 silencing siRNA and PTX, respectively. Upon administration in multidrug resistant SKOV3_TR human ovarian adenocarcinoma cells, siRNA-mediated MDR-1 gene silencing was evident at 100 nM dose. Combination of MDR-1 gene silencing and nanoparticle-mediated delivery significantly influenced the cytotoxic activity of PTX in SKOV3_TR cells similar to what was observed in drug sensitive SKOV3 cells. We speculate that the enhancement in cytotoxicity was due to an increase in intracellular drug accumulation upon MDR-1 gene silencing leading to an apoptotic cell-kill effect. Taken together, these preliminary results are highly encouraging for the development of combination nano-therapeutic strategies that combine gene silencing and drug delivery to provide more potent therapeutic effect, especially in refractory tumors.     

Anti-HER-2 engineering antibody ChA21 inhibits growth and induces apoptosis of SK-OV-3 cells

Background and Aims

Anti-HER-2 antibodies targeting distinct epitopes have different biological functions on cancer cells. In a previous study, we demonstrated that anti-HER-2 engineering antibody ChA21 was able to bind to subdomain I of HER-2 extracellular domain. In this study, The effects of ChA21 on growth and apoptosis against ovarian carcinoma cell SK-OV-3 over-expressing HER-2 in vitro and in vivo were investigated.

Methods

Cell growth inhibition was evaluated by MTT assay. Apoptosis was detected by TUNEL stain, transmission electron microscopy and flow cytometry on cultured cells and tissue sections from nude mice xenografts. The apoptosis-related proteins Bax and Bcl-2 were assessed by immunohistochemistry.

Results

We found that treatment of ChA21 caused a dose-dependent decrease of cell proliferation in vitro and a significant inhibition of tumor growth in vivo. ChA21 therapy led to a significant increase in the induction of apoptosis, and up-regulated the expression of Bax, while the expression of Bcl-2 was down-regulated.

Conclusion

These data suggest that ChA21 inhibits the growth and induces apoptosis of SK-OV-3 via regulating the balance between Bax and Bcl-2.     

Class III ��-tubulin expression and in vitro resistance to microtubule targeting agents

Background:

Class III β-tubulin overexpression is a marker of resistance to microtubule disruptors in vitro, in vivo and in the clinic for many cancers, including breast cancer. The aims of this study were to develop a new model of class III β-tubulin expression, avoiding the toxicity associated with chronic overexpression of class III β-tubulin, and study the efficacy of a panel of clinical and pre-clinical drugs in this model.

Methods:

MCF-7 (ER+ve) and MDA-MB-231 (ER−ve) were either transfected with pALTER-TUBB3 or siRNA-tubb3 and 24 h later exposed to test compounds for a further 96 h for proliferation studies. RT–PCR and immunoblotting were used to monitor the changes in class III β-tubulin mRNA and protein expression.

Results:

The model allowed for subtle changes in class III β-tubulin expression to be achieved, which had no direct effect on the viability of the cells. Class III β-tubulin overexpression conferred resistance to paclitaxel and vinorelbine, whereas downregulation of class III β-tubulin rendered cells more sensitive to these two drugs. The efficacy of the colchicine-site binding agents, 2-MeOE2, colchicine, STX140, ENMD1198 and STX243 was unaffected by the changes in class III β-tubulin expression.

Conclusion:

These data indicate that the effect of class III β-tubulin overexpression may depend on where the drug''s binding site is located on the tubulin. Therefore, this study highlights for the first time the potential key role of targeting the colchicine-binding site, to develop new treatment modalities for taxane-refractory breast cancer.     

Protopine, a novel microtubule-stabilizing agent, causes mitotic arrest and apoptotic cell death in human hormone-refractory prostate cancer cell lines

In this study, we investigated the anticancer effect of protopine on human hormone-refractory prostate cancer (HRPC) cells. Protopine exhibited an anti-proliferative effect by induction of tubulin polymerization and mitotic arrest, which ultimately led to apoptotic cell death. The data suggest that protopine increased the activity of cyclin-dependent kinase 1 (Cdk1)/cyclin B1 complex and that contributed to cell apoptosis by modulating mitochondria-mediated signaling pathways, such as Bcl-2 phosphorylation and Mcl-1 down-regulation. In conclusion, the data suggest that protopine is a novel microtubule stabilizer with anticancer activity in HRPC cells through apoptotic pathway by modulating Cdk1 activity and Bcl-2 family of proteins.