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Purpose: This study assesses the ability of multidrug resistance (MDR)-associated gene expression patterns to predict survival in patients with newly diagnosed carcinoma of the ovary. The scope of this research differs substantially from that of previous reports, as a very large set of genes was evaluated whose expression has been shown to affect response to chemotherapy., Experimental Design: We applied a customized TaqMan low density array, a highly sensitive and specific assay, to study the expression profiles of 380 MDR-linked genes in 80 tumor specimens collected at initial surgery to debulk primary serous carcinoma. The RNA expression profiles of these drug resistance genes were correlated with clinical outcomes., Results: Leave-one-out cross-validation was used to estimate the ability of MDR gene expression to predict survival. Although gene expression alone does not predict overall survival (OS; P = 0.06), four covariates (age, stage, CA125 level, and surgical debulking) do (P = 0.03). When gene expression was added to the covariates, we found an 11-gene signature that provides a major improvement in OS prediction (log-rank statistic P < 0.003). The predictive power of this 11-gene signature was confirmed by dividing high- and low-risk patient groups, as defined by their clinical covariates, into four specific risk groups on the basis of expression levels., Conclusion: This study reveals an 11-gene signature that allows a more precise prognosis for patients with serous cancer of the ovary treated with carboplatin- and paclitaxel-based therapy. These 11 new targets offer opportunities for new therapies to improve clinical outcome in ovarian cancer.

The development of multidrug resistance (MDR) is a major hindrance to cancer eradication as it renders tumors unresponsive to most chemotherapeutic treatments and is associated with cancer resurgence. This study describes a novel mechanism to overcome MDR through a polymer-blend nanoparticle platform that delivers a combination therapy of C6-ceramide (CER), a synthetic analog of an endogenously occurring apoptotic modulator, together with the chemotherapeutic drug paclitaxel (PTX), in a single formulation. The PTX/CER combination therapy circumvents another cellular mechanism whereby MDR develops, by lowering the threshold for apoptotic signaling. In vivo studies in a resistant subcutaneous SKOV3 human ovarian and in an orthotopic MCF7 human breast adenocarcinoma xenograft showed that the PTX and CER nanoparticle combination therapy reduced the final tumor volume at least twofold over treatment with the standard PTX therapy alone. The study also revealed that the cotherapy accomplished this enhanced efficacy by generating an enhancement in apoptotic signaling in both tumor types. Additionally, acute evaluation of safety with the combination therapy did not show significant changes in body weight, white blood cell counts, or liver enzyme levels. The temporal-controlled nanoparticle delivery system presented in this study allows for a simultaneous delivery of PTX + CER in breast and ovarian tumor model drug, leading to a modulation of the apoptotic threshold. This strategy has tremendous potential for effective treatment of refractory disease in cancer patients.

Previous studies have identified interleukin 6 (IL-6) as an important cytokine with prognostic significance in ovarian cancer. Activation of the IL-6-Stat3 pathway contributes to tumor cell growth, survival and drug resistance in several cancers, including ovarian cancer. To explore potential therapeutic strategies for interrupting signaling through this pathway, we assessed the ability of CDDO-Me, a synthetic triterpenoid, to inhibit IL-6 secretion, Stat3 phosphorylation, Stat3 nuclear translocation and paclitaxel sensitivity in several cell line model systems. These studies demonstrated that CDDO-Me significantly inhibits IL-6 secretion in paclitaxel-resistant ovarian cancer cells and specifically suppresses IL-6- or oncostatin M-induced Stat3 nuclear translocation. Treatment with CDDO-Me significantly decreases the levels of Stat3, Jak2, and Src phosphorylation in ovarian and breast cancer cell lines with constitutively activated Stat3. This inhibition of the IL-6-Stat3 pathway correlated with suppression of the anti-apoptotic Stat3 target genes Bcl-X(L), survivin, and Mcl-1, and with apoptosis induction as measured by monitoring PARP and its cleavage product, as well as by quantitative measurement of the apoptosis-associated CK18Asp396. Furthermore, CDDO-Me increases the cytotoxic effects of paclitaxel in the paclitaxel-resistant ovarian cancer cell line OVCAR8(TR) (2 to 5-fold) and of cisplatin in the cisplatin-resistant ovarian cancer cell line A2780cp70 (2 to 4-fold). Our data confirm that CDDO-Me interrupts the signaling of multiple kinases involved in the IL-6-Stat3 and Src signaling pathways. Inhibition is likely achieved through multiple points within these pathways. In a model system of established acquired drug resistance, CCDO-Me is effective at partially reversing the drug-resistance phenotype.

In this study, we have investigated the biodistribution and pharmacokinetic analysis of paclitaxel (PTX) and the apoptotic signaling molecule, C6-ceramide (CER), when administered in a multifunctional polymer-blend nanoparticle formulation to female nude mice bearing an orthotopic drug sensitive MCF7 and multidrug resistant MCF7 TR (MDR-1 positive) human breast adenocarcinoma. A polymer-blend nanoparticle system was engineered to incorporate temporally controlled sequential release of the combination drug payload. Hereby, PTX was encapsulated in the pH-responsive rapid releasing polymer, poly(beta-amino ester) (PbAE), while CER was present in the slow releasing polymer, poly(D,L-lactide-co-glycolide) (PLGA) within these blend nanoparticles. When particle formulations were administered intravenously to MCF7 and MCF7 TR tumor bearing mice, higher concentrations of PTX were found in the blood due to longer retention time and an enhanced tumor accumulation relative to administration of free drug. In addition, the PLGA/PbAE blend nanoparticles were effective in enhancing the residence time of both drugs at the tumor site by reducing systemic clearance. Overall, these results are highly encouraging for development of multifunctional polymer-blend nanoparticle formulations that can be used for temporal-controlled administration of two drugs from a single formulation.

Purpose: To modulate intracellular ceramide levels and lower the apoptotic threshold in multidrug-resistant ovarian adenocarcinoma, we have examined the efficacy and preliminary safety of tamoxifen coadministration with paclitaxel in biodegradable poly(ethylene oxide)-modified poly(epsilon-caprolactone) (PEO-PCL) nanoparticles., Experimental Design: In vitro cytotoxicity and proapoptotic activity of paclitaxel and tamoxifen, either as single agent or in combination, was examined in wild-type (SKOV3) and MDR-1-positive (SKOV3TR) human ovarian adenocarcinoma cells. Subcutaneous SKOV3 and SKOV3TR xenografts were established in female nu/nu mice, and this model was used to evaluate the antitumor efficacy and preliminary safety. Paclitaxel (20 mg/kg) and tamoxifen (70 mg/kg) were administered i.v. either as a single agent or in combination in aqueous solution and in PEO-PCL nanoparticles., Results: In vitro cytotoxicity results showed that administration of paclitaxel and tamoxifen in combination lowered the IC50 of paclitaxel by 10-fold in SKOV3 cells and by >3-fold in SKOV3TR cells. The combination paclitaxel/tamoxifen co-therapy showed even more pronounced effect when administered in nanoparticle formulations. Upon i.v. administration of paclitaxel/tamoxifen combination in PEO-PCL nanoparticle formulations, significant enhancement in antitumor efficacy was observed. Furthermore, the combination paclitaxel/tamoxifen therapy did not induce any acute toxicity as measured by body weight changes, blood cell counts, and hepatotoxicity., Conclusions: The results of this study show that combination of paclitaxel and tamoxifen in biodegradable PEO-PCL nanoparticles can serve as an effective clinically translatable strategy to overcome multidrug resistance in ovarian cancer.

Interleukin 6 and the signal transducer and activator of transcription (STAT) 3 proteins have important roles in cancer cell survival and proliferation. Recent studies demonstrate that abnormal STAT3 activation promotes tumor growth and supports survival of many human cancers, and thus, this protein or the pathway responsible for its activation is a potential target for the new anticancer therapy. STAT3 is a DNA binding transcription factor, and therefore, its function depends on nuclear translocation. To discover inhibitors of the STAT3 pathway, we designed a cell-based screening assay capable of identifying small molecules that inhibit nuclear translocation. Among the 2000-compound National Cancer Institute Diversity set, we identified 8-benzyl-4-oxo-8-azabicyclo[3.2.1]oct-2-ene-6,7-dicarboxylic acid (SD-1008) as a micromolar inhibitor of interleukin-6 or oncostatin-induced STAT3 nuclear translocation. In addition, SD-1008 inhibits tyrosyl phosphorylation of STAT3, Janus kinase 2 (JAK2), and Src. SD-1008 also reduces STAT3-dependent luciferase activity. Biochemical studies with recombinant JAK2 proteins demonstrate that high concentrations of SD-1008 directly inhibit JAK2 kinase autophosphorylation. Exposure of various cell lines to SD-1008 decreases levels of the STAT3-dependent proteins, Bcl-X(L) and survivin, inducing apoptosis. SD-1008 also enhances apoptosis induced by paclitaxel in ovarian cancer cells. These results demonstrate that SD-1008 directly blocks the JAK-STAT3 signaling pathway in human cancer cells that express constitutively active Stat and add to the growing literature that identifies this pathway as a viable target for drug development. Finally, SD-1008 may be a suitable prototype for further chemical modification and exploration as a therapeutic agent.

The objective of this study was to overcome drug resistance upon systemic administration of combination paclitaxel (PTX) and the apoptotic signaling molecule C(6)-ceramide (CER) in biodegradable poly(ethylene oxide)-modified poly(epsilon-caprolactone (PEO-PCL) nanoparticles. Subcutaneous sensitive (wild-type) and multidrug resistant (MDR-1 positive) SKOV-3 human ovarian adenocarcinoma xenografts were established in female Nu/Nu mice. PTX and CER were administered intravenously either as a single agent or in combination in aqueous solution and in PEO-PCL nanoparticles to the tumor-bearing mice. There was significant (p< 0.05) tumor growth suppression in both wild-type SKOV-3 and multidrug resistant SKOV-3(TR) models upon single dose co-administration of PTX (20 mg/kg) and CER (100 mg/kg) in nanoparticle formulations as compared to the individual agents and administration in aqueous solutions. For instance, in SKOV-3 wild-type model, more than 4.3-fold increase (p < 0.05) in tumor growth delay and 3.6-fold (p < 0.05) increase in tumor volume doubling time (DT) were observed with the combination treatment in nanoparticles as compared to untreated animals. Similarly, 3-fold increase (p < 0.05) in tumor growth delay and tumor volume DT was observed in SKOV-3(TR) model. Body weight changes and blood cells counts were used as measures of safety and, except for an increase in platelet counts (p < 0.05) in PTX + CER treated animals, there was no difference between various treatment strategies. The results of this study show that combination of PTX and CER in biodegradable polymeric nanoparticles can serve as a very effective therapeutic strategy to overcome drug resistance in ovarian cancer., ((c) 2007 Wiley-Liss, Inc.)

In the search for novel genes involved in the paclitaxel resistance phenotype, prior studies of gene expression in paclitaxel-resistant cell lines and their paired drug-sensitive parental lines using high-density Affymetrix GeneChip arrays identified guanylate-binding protein 1 (GBP1) gene as an overexpressed transcript. The GBP1 gene encodes a large GTPase that is induced by interferon gamma (IFN-gamma) in a variety of eukaryotic cells. In this report we characterize GBP1 and demonstrate that GBP1 expression is consistently upregulated in 7 of 8 paclitaxel or doxorubicin-resistant human cancer cell lines as compared to its expression in the relevant drug-sensitive parental lines. Analysis of GBP1 expression using the Cancer Profiling Array showed that GBP1 is ubiquitously expressed with no significant difference in expression levels between normal and tumor tissue. Parallel analysis of the Cancer Cell Line Profiling Array determined that GBP1 expression in a majority of cell lines derived from human tumors of different tissue origin was induced to variable levels following exposure to multiple stress agents including paclitaxel and doxorubicin. Importantly, stable expression of a GBP1 transgene in the paclitaxel-sensitive ovarian cancer cell line OVCAR8 was sufficient to confer moderate paclitaxel resistance. Our data suggest that increased expression of the GBP1 gene may play an important role in the development of multi-drug resistance (MDR).

Purpose: To identify genes involved in the paclitaxel resistance phenotype., Methods: High-density Affymetrix HG-U95Av2 microarrays were used to quantify gene expression in the resulting cell lines, SKOV-3TR, OVCAR8TR and MCF-7TR, and their drug-sensitive parental lines, SKOV-3, OVCAR8 and MCF-7., Results: Three paclitaxel-resistant human ovarian and breast cancer cell lines were established. We identified 790 (SKOV-3TR), 689 (OVCAR8TR) and 964 (MCF-7TR) transcripts that were more than twofold overexpressed relative to their expression in the corresponding parental cell line. A comparison of these transcripts identified eight genes that were significantly overexpressed in all three drug-resistant daughter cell lines. These genes included MDR1, a gene often implicated in both in vitro and in vivo resistance to multiple chemotherapeutics, including paclitaxel. The remaining seven genes have not been previously associated with resistance to paclitaxel in human cancer. Furthermore, we identified 815 (SKOV-3TR), 430 (OVCAR8TR) and 332 (MCF-7TR) transcripts that were more than twofold decreased relative to their expression in the corresponding parental cell line. Comparison of these transcripts identified three genes that were significantly underexpressed in all three drug-resistant cell lines, none of which have been previously associated with paclitaxel resistance., Conclusions: Our results confirm that the paclitaxel resistance phenotype is associated with a large number of transcriptional changes. In addition, acquired paclitaxel resistance was associated with distinct transcriptional changes in each of the cell lines studied, suggesting that paclitaxel resistance is a complex phenotype that can arise through multiple mechanisms.

Previous studies directed at identifying paclitaxel resistance genes in a paclitaxel-resistant subclone of the human ovarian cancer cell line SKOV-3 identified a novel cancer testis antigen, Taxol resistance-associated gene 3 (TRAG-3). Because investigation suggested that TRAG-3, located on chromosome Xq28, does not directly participate in the paclitaxel-resistant phenotype, it was hypothesized that TRAG-3 might be linked to a neighboring gene that is directly involved in the drug-resistant phenotype, or alternatively, overexpression of TRAG-3 might be attributable to coregulation with other cancer testis antigens. To distinguish between these two hypotheses, expression of the genes that flank TRAG-3 was evaluated, namely the Centrin 2 gene and several members of the MAGE gene cluster. Northern analysis demonstrates overexpression of MAGE2 but not Centrin 2. Extension of this analysis to other neighboring and non-neighboring representative cancer testis antigens reveals overexpression of MAGE3, MAGE6, MAGE11, and MAGE12, as well as GAGE-2, GAGE-4, GAGE-5, GAGE-6, and GAGE-7 (clustered on Xp11) in SKOV-3(TR), as compared with SKOV-3. In addition, Affymetrix-based analysis of gene expression in SKOV-3 subclones with variable paclitaxel resistance demonstrates MAGE gene overexpression occurs early in the development of the paclitaxel-resistant phenotype, whereas GAGE gene overexpression occurs somewhat later. Evaluation of additional breast and ovarian cancer cell lines reveals MAGE/GAGE overexpression in both paclitaxel- and doxorubicin-resistant cell lines, whereas gemcitabine-resistant subclones of several ovarian cancer cell lines, including SKOV-3(GR), reveals no change in MAGE/GAGE expression. To determine whether MAGE gene overexpression contributes directly to the drug-resistant phenotype, MAGE2 or MAGE6, cDNA was introduced into the paclitaxel-sensitive human ovarian cancer cell line OVCAR8. 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide cytotoxicity analysis of both MAGE2 and MAGE6 transfectants demonstrates a 4-fold increase in resistance to paclitaxel and 2-fold increase in resistance to doxorubicin but not to other drugs, such as topotecan and cisplatin, through a nonmultidrug resistance-1 mechanism. MAGE2 or MAGE6 overexpression also induces a growth advantage in OVCAR8-transfected cells. These studies suggest that the in vitro acquisition of paclitaxel and doxorubicin resistance can be associated with increased expression of a variety of both neighboring and non-neighboring cancer testis antigens genes. This does not appear to be a consequence of random genetic instability or genomic amplification of the X chromosome. These antigens, because of limited expression in normal tissues, may be suitable targets for immunotherapy and novel therapeutic strategies in the treatment of chemotherapy-resistant epithelial tumors.

It has been approximately ten years since the Food and Drug Administration (FDA) approved paclitaxel for the treatment of platinum resistant epithelial ovarian carcinoma. Since the approval, the drug has found therapeutic applications in a variety of schedules and in a wide variety of epithelial malignancies. Its novel mechanism of action provided the hope that it would demonstrate anti-neoplastic activity in multidrug resistant tumor cells. Unfortunately, as with other chemotherapeutic drugs, resistance is commonly seen. Laboratory investigation has defined a wide variety of resistance mechanisms including overexpression of multidrug resistance (MDR-1) gene, molecular changes in the target molecule (betatubulin), changes in apoptotic regulatory and mitosis checkpoint proteins, and more recently changes in lipid composition and potentially the overexpression of interleukin 6 (IL-6). This review describes the in vitro molecular data that define and support the various mechanisms of resistance and critically evaluates the evidence for the participation of these mechanisms in clinically relevant paclitaxel resistance. This review also explores pharmacologic attempts to modulate paclitaxel resistance, principally through inhibition of the MDR-1 drug efflux pump. Future avenues for drug resistance research and its pharmacologic manipulation in the clinic are discussed.

The cytokines IL-6, initially recognized as a regulator of immune and inflammatory response and IL-8, a potential regulator of angiogenesis, also regulate the growth of many tumor cells. Human cancer cells selected for multidrug resistance to common chemotherapeutic agents demonstrate increased expression of IL-6 and IL-8. To determine whether IL-6 or IL-8 overexpression contributes directly to the drug resistant phenotype, IL-6 or IL-8 cDNA were introduced into the paclitaxel sensitive human osteosarcoma cell line U-2OS using the pIRESneo bicistronic expression vector. Interleukin-6 and IL-8 transfectants were selected for either high IL-6 or IL-8 secretion and evaluated in drug resistance assays. Two IL-6 and two IL-8 secreting clones express IL-6 or IL-8 levels of 10 ng/ml and 1 ng/ml in culture, while parental U-2OS and pIRESneo vector transfected control cells express IL-6 and IL-8 levels of 0.005 ng/ml and 0.1 ng/ml, respectively. MTT cytotoxicity with IL-6 transfected cells demonstrates a five-fold increase in resistance to paclitaxel and a four-fold increase in resistance to doxorubicin as compared to U-2OS. There are no changes in mitoxantrone or topotecan resistance in the IL-6 transfectants as compared to parental U-2OS. Northern analysis of IL-6 transfectants demonstrates that the resistant phenotype is not related to increased levels of MDR-1, MRP-1, or LRP. Western analysis also confirms that P-glycoprotein levels are not altered in IL-6 transfectants. Further supporting an MDR-1 independent mechanism of drug resistance, verapamil cannot reverse paclitaxel resistance in transfected cells, findings further supported by rhodamine 123 exclusion data. Treatment of IL-6 transfected cells with paclitaxel, compared with drug-sensitive parental U-2OS, shows U-2OS(IL-6) are significantly more resistant to apoptosis induced by paclitaxel and exhibit decreased proteolytic activation of caspase-3. In contrast U-2OS(IL-8) transfectants demonstrate no appreciable increase in paclitaxel resistance when compared with parental cells. In summary, while both IL-6 and IL-8 are overexpressed in paclitaxel resistant cell lines, only IL-6 has the potential to contribute directly to paclitaxel and doxorubicin resistance in U-2OS. This resistance is through a non-MDR-1 pathway., (Copyright 2002 Elsevier Science Ltd. All rights reserved.)