Therapeutic Efficacy Of Paclitaxel Research Articles

The upregulation and transcriptional regulatory mechanisms of Extra spindle pole bodies like 1 in bladder cancer: An immunohistochemistry and high-throughput screening Evaluation

BackgroundThis study aimed to explore the expression level and transcriptional regulation mechanism of Extra Spindle Pole Bodies Like 1 (ESPL1) in bladder cancer (BC). MethodsA multicentre database of samples (n = 1391) was assayed for ESPL1 mRNA expression in BC and validated at the protein level by immunohistochemical (IHC) staining of in-house samples (n = 202). Single-cell sequencing (scRNA-seq) analysis and enrichment analysis explored ESPL1 distribution and their accompanying molecular mechanisms. ATAC-seq, ChIP-seq and Hi-C data from multiple platforms were used to investigate ESPL1 upstream transcription factors (TFs) and potential epigenetic regulatory mechanisms. Immune-related analysis, drug sensitivity and molecular docking of ESPL1 were also calculated. Furthermore, upstream microRNAs and the binding sites of ESPL1 were predicted. The expression level and early screening efficacy of miR-299-5p in blood (n = 6625) and tissues (n = 537) were examined. ResultsESPL1 was significantly overexpressed at the mRNA level (p < 0.05, SMD = 0.75; 95 % CI = 0.09, 1.40), and IHC staining of in-house samples verified this finding (p < 0.0001). ESPL1 was predominantly distributed in BC epithelial cells. Coexpressed genes of ESPL1 were enriched in cell cycle–related signalling pathways, and ESPL1 might be involved in the communication between epithelial and residual cells in the Hippo, ErbB, PI3K-Akt and Ras signalling pathways. Three TFs (H2AZ, IRF5 and HIF1A) were detected upstream of ESPL1 and presence of promoter-super enhancer and promoter-typical enhancer loops. ESPL1 expression was correlated with various immune cell infiltration levels. ESPL1 expression might promote BC growth and affect the sensitivity and therapeutic efficacy of paclitaxel and gemcitabine in BC patients. As an upstream regulator of ESPL1, miR-299-5p expression was downregulated in both the blood and tissues, possessing great potential for early screening. ConclusionsESPL1 expression was upregulated in BC and was mainly distributed in epithelial cells. Elevated ESPL1 expression was associated with TFs at the upstream transcription start site (TSS) and distant chromatin loops of regulatory elements. ESPL1 might be an immune-related predictive and diagnostic marker for BC, and the overexpression of ESPL1 played a cancer-promoting role and affected BC patients’ sensitivity to drug therapy. miR-299-5p was downregulated in BC blood and tissues and was also expected to be a novel marker for early screening.

Biguanide-anchored albumin-based nanoplatform inhibits epithelial-mesenchymal transition and reduces the stemness phenotype for metastatic cancer therapy.

In clinical chemotherapy, albumin-bound paclitaxel (Abraxane) can improve the tumor targeting property and therapeutic efficacy of paclitaxel (PTX) against orthotopic malignancies. However, patients with metastatic cancer have a poor prognosis, probably due to the instability, chemoresistance, and inability of albumin-bound paclitaxel to alter the tumor microenvironment. Here we propose a new biguanide-modified albumin-based nanoplatform that encapsulates paclitaxel for the effective treatment of metastatic cancer. The PTX is encapsulated in poly (lactic-co-glycolic acid) cores coated with biguanide-modified albumin (HSA-NH). The functionalized nanoparticles (HSA-NH NPs) exhibit a remarkable stable profile with low drug release (P < 0.05 versus Abraxane), target tumor tissues, suppress epithelial-mesenchymal transition (EMT) events for anti-metastatic effects, and reduce the phenotype of cancer stem cells. As a result, HSA-NH NPs effectively prolong animal survival (55 days) by inhibiting not only primary tumor growth but also metastasis. This study provides proof of concept that the biguanide-anchored albumin-based nanoplatform encapsulating PTX is a powerful, safe, and clinically translational strategy for the treatment of metastatic cancer. STATEMENT OF SIGNIFICANCE: Albumin-bound paclitaxel (Abraxane) can increase paclitaxel's tumor targeting and therapeutic efficacy in clinical cancer treatments such as breast cancer. However, the instability, chemoresistance, and lack of tumor microenvironment modulation of albumin-bound paclitaxel may lead to poor therapeutic efficacy in metastatic cancer patients. Here we develop biguanide-anchored albumin-based nanoplatforms that encapsulate paclitaxel (HSA-NH NPs) for metastatic cancer treatment. Poly(lactic-co-glycolic acid) (PLGA) cores encapsulating paclitaxel improve the stability of HSA-NH NPs. Based on the activities of metformin, biguanide-anchored albumin adsorbed on PLGA cores improves paclitaxel efficacy, inhibits various aberrant changes during epithelial-mesenchymal transition, and reduces tumor cell stemness. The biguanide-anchored albumin-based nanoplatform encapsulating PTX can serve as a potent, safe, and clinically translational approach for metastatic cancer therapies.

HOTAIR promotes paclitaxel resistance by regulating CHEK1 in ovarian cancer.

The HOX transcript antisense RNA (HOTAIR) has been reported to be aberrantly expressed in ovarian cancer (OC). Abnormal high expression level of HOTAIR has been found to be associated with poor overall survival of OC patients. Yet, the role of HOTAIR in paclitaxel resistance of OC is unclear. This study aims to investigate the effect, as well as the mechanism of HOTAIR in promoting paclitaxel resistance of OC. Ovarian cancer cell lines with down-regulated and up-regulated expression of HOTAIR were, respectively, established. The expression of HOTAIR was confirmed by qRT-PCR. The sensitivity of ovarian cancer cells to paclitaxel was detected by MTT assays, colony formation, EdU assays, flow cytometry, and in vivo experiments. An increased expression level of HOTAIR was observed in ovarian cancer cell lines following treatment with paclitaxel. When the expression of HOTAIR was down-regulated, the proliferation of ovarian cancer cells was found to be inhibited, coupled with enhanced cell sensitivity to paclitaxel. Conversely, when the HOTAIR expression was up-regulated, an opposite effect was observed on the ovarian cancer cells. In addition, cell cycle arrest in G2/M phase was also shown to be accelerated upon HOTAIR suppression. Strikingly, our results also revealed that HOTAIR plays a regulatory role in the expression of checkpoint kinase 1 (CHEK1), and that the restored paclitaxel sensitivity through knockdown of HOTAIR can be weakened by CHEK1 up-regulation. Consistently, in vivo data confirmed that the therapeutic efficacy of paclitaxel can be enhanced through down-regulation of HOTAIR, and that CHEK1 is the down-stream target of HOTAIR in inducing paclitaxel resistance. HOTAIR confers paclitaxel resistance in epithelial ovarian cancer by increasing the protein level of CHEK1.

Abstract 336: A recombinant human protein targeting HER2 overcomes drug resistance in HER2-positive breast cancer

Abstract Background &amp; Goals: HER2 is an oncogenic receptor tyrosine kinase (RTK) implicated in several types of human cancer. It is strongly expressed in about 20% of breast cancer (BC), known as HER2-positive BC (HER2-BC), due to gene amplification. HER2 amplification or overexpression is a strong predictor of poor disease prognosis. Several HER2-targeting drugs are available for treating HER2-BC, including monoclonal antibodies trastuzumab (Ttzm) and pertuzumab, T-DM1 (Ttzm coupled to a microtubule inhibitor), and tyrosine kinase inhibitors (TKIs) lapatinib and neratinib. While these agents have greatly improved disease outcomes, primary and acquired drug resistance, including cross-resistance, is common. Overcoming drug resistance remains a major unmet medical need in HER2-BC. Notably, HER2 remains overexpressed in drug-resistant HER2-BC cells. We recently found that recombinant human peptidase D (PEPD), also known as prolidase, strongly downregulates HER2 and EGFR in cancer cells in vitro and in vivo via its binding to HER2 and EGFR. The enzymatic activity of PEPD plays no role in its modulation of HER2 and EGFR, and we subsequently focused on recombinant PEPDG278D, an enzymatically inactive mutant (point mutation at codon 278). Our objective in the present study is to determine whether PEPDG278D is active in preclinical models of HER2-BC resistant to clinically available HER2 inhibitors and if so, its mechanism of action. Results: PEPDG278D was exceedingly effective against HER2-BC cells that are resistant to Ttzm and other HER2 inhibitors. The cells carried activating PIK3CA mutations, low expression of PTEN, and/or cyclin E overexpression. All the cell lines also overexpressed MUC4 which shields HER2 from Ttzm and stabilizes HER2. However, PEPDG278D rapidly bound to and freed HER2 from MUC4, and rapidly disrupted the interaction of HER2 with other RTKs, including MET and IGF1R. PEPDG278D subsequently induced persistent downregulation of HER2 via internalization and lysosomal degradation. PEPDG278D also downregulated EGFR. Thus, PEPDG278D suppresses multiple RTKs either directly or indirectly in HER2-BC cells. In contrast, Ttzm cannot perform any of these functions of PEPDG278D. PEPDG278D was highly active in mouse tumor models of HER2-BC resistant to Ttzm and also enhanced the therapeutic efficacy of paclitaxel. However, adverse effects of PEPDG278D were not detected in the animal studies. Conclusions &amp; Therapeutic Relevance: The therapeutic activity of PEPDG278D highlights that HER2 remains a critical target in drug-resistant HER2-BC. The strong therapeutic activity of PEPDG278D in preclinical models of drug-resistant HER2-BC, which carry clinically relevant molecular changes that confer resistance to current HER2 inhibitors provides the scientific premise for potential evaluation of this recombinant human protein in patients with drug-resistant HER2-BC. Citation Format: Lu Yang, yun Li, Arup Bhattacharya, yuesheng Zhang. A recombinant human protein targeting HER2 overcomes drug resistance in HER2-positive breast cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 336.

A retrospective analysis of cisplatin/carboplatin plus paclitaxel in advanced or recurrent cervical cancer

To compare the efficacy and safety of paclitaxel plus carboplatin (TC) and paclitaxel plus cisplatin (TP) in the treatment of advanced or recurrent cervical cancer, this retrospective study included 116 advanced or recurrent cervical cancer cases treated at Beijing Obstetrics and Gynecology Hospital between June 2002 and June 2014. Of these cases, 52 were treated with TC (TC group) and 64 were treated with TP (TP group). We found that the overall survival and response and disease-control rates were not significantly different between the two groups. The TC group had a markedly lower incidence of Grade III–IV gastrointestinal toxicity reactions and a shorter hospitalisation stay than the TP group. The incidences of Grade III–IV bone marrow suppression and renal toxicity were not significantly different between the TP and TC groups. These findings suggest that TC may be a safe and effective alternative to TP for the treatment of advanced or recurrent cervical cancer.Impact StatementWhat is already known on this subject: Paclitaxel plus cisplatin (TP) is regarded as the standard regimen for cervical cancer, nevertheless, cisplatin is always associated with nephrotoxicity and requires hydration therapy. Carboplatin is a platinum analogue with milder nephrotoxicity than cisplatin. It is reported that carboplatin may be a viable and less toxic alternative to cisplatin in the management of advanced or recurrent cervical cancer, but another study shows that the therapeutic efficacy of paclitaxel plus carboplatin (TC) is non-inferior to that of TP.What the results of this study add: This study compared the efficacy and safety of TC and TP, and found that the TC and TP groups had similar overall response and disease-control rates and survival, but the TC group was better tolerated with a markedly lower incidence of Grades III–IV gastrointestinal toxicity reactions and had a shorter hospitalisation stay than the TP group.What the implications are of these findings for clinical practice and/or further research: TC may be a safe and effective alternative to TP for the treatment of advanced or recurrent cervical cancer in clinical practice.

Development, characterization and biological in vitro assays of paclitaxel-loaded PCL polymeric nanoparticles

Adenocarcinoma is the most lethal gynecologic tumor and treatment usually consists in surgery followed by chemotherapy. However, the chemotherapy benefits are eventually limited due to drug toxicity to normal tissues and cells, which cause several and harsh side effects. Paclitaxel (PCX) is the drug of first choice for ovarian cancer treatment, but it has low aqueous solubility, which reduces its bioavailability. Thus, in the commercial drug, Taxol®, PCX is solubilized in a mixture of toxic surfactants. The development of drug nanocarriers has been investigated to promote the reduction of toxic effects and increase the safety and therapeutic efficacy of PCX. The aim of this work was the development and characterization of PCX loaded nanoparticles (PNPCX) and evaluation of in vitro efficacy of developed system using adenocarcinoma cell line. The nanocarrier was successfully obtained using nanoprecipitation technique. The results showed that the PNPCX-A had a particle size distribution around 140 nm and polydispersity index smaller than 0.1, with high PCX encapsulation efficiency. The results obtained were suitable for the intravenous administration route and promotion of passive targeting in the tumor microenvironment. The in vitro cytotoxicity assays of SKOV-3 cell line demonstrated that PNPCX-A was able to release PCX and reduce cell viability. The flow cytometry assays first reported that a nanostructured system with such composition (PNPCX-A) presented a time dependent cellular uptake, showing the ability of nanocarrier to be internalized. PNPCX-A present a distinguish potential for ovarian cancer therapy optimization. In vivo studies are needed to confirm the in vitro results and provide additional data regarding safety and efficacy of ovarian cancer treatment.

Rsf-1 Influences the Sensitivity of Non-Small Cell Lung Cancer to Paclitaxel by Regulating NF-κB Pathway and Its Downstream Proteins

Background/Aims: The therapeutic efficacy of paclitaxel is hampered by chemotherapeutic resistance in non-small cell lung cancer (NSCLC). Rsf-1 enhanced paclitaxel resistance via nuclear factor-κB (NF-κB) in ovarian cancer cells and nasopharyngeal carcinoma. This study assessed the function of Rsf-1 in the modulation of the sensitivity of NSCLC to paclitaxel via the NF-κB pathway. Methods: The mRNA and protein levels of the related genes were quantified by RT-PCR and Western blotting. Rsf-1 silencing was achieved with CRISPR/Cas9 gene editing. Cell cycle, migration and proliferation were tested with flow cytometry, transwell test and CCK8 test. Cell apoptosis was analyzed with flow cytometry and quantification of C-capase3. The parameters of the tumors were measured in H460 cell xenograft mice. Results: Rsf-1 was highly expressed in H460 and H1299 cells. Rsf-1 knockout caused cell arrest at the G1 phase, increased cell apoptosis, and decreased migration and cell proliferation. Rsf-1 knockout increased the inhibition of cell proliferation, the reduction in cell migration and the augment in cell apoptosis in paclitaxel treated H460 and H1299 cells. Rsf-1 knockout further enhanced the paclitaxel-mediated decrease in the volume and weight of the tumors in H460 cell xenograft mice. Helenalin and Rsf-1 knockout decreased the protein levels of p-P65, BcL2, CFLAR, and XIAP; hSNF2H knockout decreased the protein level of NF-κB p-P65 without altering Rsf-1 and p65 protein levels, while Rsf-1 and hSNF2H double knockout decreased the level of NF-κB p-P65, in H1299 and H460 cells. Conclusion: These results demonstrate that Rsf-1 influences the sensitivity of NSCLC to paclitaxel via regulation of the NF-κB pathway and its downstream genes.

Application of paclitaxel as adjuvant treatment for benign cicatricial airway stenosis.

Benign cicatricial airway stenosis (BCAS) is a potentially life-threatening disease. Recurrence occurs frequently after endoscopic treatment. Paclitaxel is known to prevent restenosis, but its clinical efficacy and safety is undetermined. Therefore, in this study, we investigated the efficacy and associated complications of paclitaxel as adjuvant treatment for BCAS of different etiologies. The study cohort included 28 patients with BCAS resulting from tuberculosis, intubation, tracheotomy, and other etiologies. All patients were treated at the Department of Respiratory Diseases, Beijing Tian Tan Hospital, Capital Medical University, China, between January 2010 and August 2014. After primary treatment by balloon dilation, cryotherapy, and/or high-frequency needle-knife treatment, paclitaxel was applied to the airway mucosa at the site of stenosis using a newly developed local instillation catheter. The primary outcome measures were the therapeutic efficacy of paclitaxel as adjuvant treatment, and the incidence of complications was observed as well. According to our criteria for evaluating the clinical effects on BCAS, 24 of the 28 cases achieved durable remission, three cases had remission, and one case showed no remission. Thus, the durable remission rate was 85.7%, and the combined effective rate was 96.4%. No differences in outcomes were observed among the different BCAS etiologies (P=0.144), and few complications were observed. Our results indicated that paclitaxel as an adjuvant treatment has greater efficacy than previously reported BCAS treatment methods.

Abstract 3856: The atomic basis for paclitaxel sensitization following loss of CRMP2 phosphorylation in ovarian cancer cells

Abstract The chemotherapeutic agent paclitaxel increases cancer cell microtubule stability, induces mitotic arrest and cancer cell death and improves survival of cancer patients. However, in ovarian and other cancers, it only elicits a response in less than half of patients who receive it. We have previously shown that enhancing microtubule stability in cells prior to paclitaxel treatment, further increases paclitaxel-induced microtubule stability and cancer cell death (Ahmed et al., Cancer Cell, 2007;12:514 and Ahmed et al., Cancer Research 2011;71:5806). We now report that the microtubule-associated protein CRMP2, and FER kinase are expressed in almost half of high-grade serous ovarian cancers and that inhibiting the phosphorylation of CRMP2 by FER is sufficient for enhancing paclitaxel-induced microtubule stability and cytotoxicity in multiple ovarian cancer cell lines. We are also able propose a detailed mechanism underlying these observations. A combination of biochemistry, super-resolution fluorescence microscopy, total internal reflection fluorescence (TIRF) microscopy and electron microscopy reveals that CRMP2 induces microtubule nucleation, elongation, bundling and stability. Moreover, FER phosphorylates CRMP2 at 6 tyrosine residues, two of which (Tyr479 and Tyr499) are critical for modulating CRMP2 function; this agrees with site-directed mutagenesis in cancer cells which points to Tyr479 as a critical site for association between CRMP2 and microtubules. A comparison of the crystal structures of wild-type CRMP2 and Tyr479Glu/Tyr499Glu phosphomimetic mutants indicate that phosphorylation of these sites induces significant conformational changes that prevent CRMP2 from forming tetramers that are known to be critical for its microtubule bundling activity. This then leads us to propose a molecular model of how CRMP2 associates with microtubules, explaining how targeting CRMP2 phosphorylation can be exploited for enhancing the therapeutic efficacy of paclitaxel. Citation Format: Yiyan Zheng, Ritika Sethi, Frank von Delft, Ahmed Ashour Ahmed. The atomic basis for paclitaxel sensitization following loss of CRMP2 phosphorylation in ovarian cancer cells. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 3856.

Effect of coumarin derivative-mediated inhibition of P-glycoprotein on oral bioavailability and therapeutic efficacy of paclitaxel

Since P-glycoprotein (P-gp) acts as a barrier to intestinal absorption of various drugs, P-gp inhibitors have been studied as oral absorption enhancers of P-gp substrate drugs. Here, we investigated the in vitro and in vivo effects of a novel coumarin derivative (LL-348) for its P-gp inhibitory activity. With LL-348, accumulation of daunomycin (DNM) increased 270% and efflux of DNM decreased 63% compared to that of DNM alone. Paclitaxel (PTX, 25mg/kg) after oral administration with LL-348 (5mg/kg), the optimal dose of LL-348 as an oral absorption enhancer of PTX, improved the relative bioavailability (RB) of PTX to 961%. In a xenograft animal model, PTX (40mg/kg) treated with LL-348 (10mg/kg) significantly increased the efficacy of PTX. The results collectively demonstrate that LL-348 can provide a therapeutic benefit in the oral absorption of P-gp substrate anticancer drugs

Abstract IA22: Causes and consequences of cancer-associated thrombocytosis

Abstract Platelets represent one of the largest storage pools of angiogenic and oncogenic growth factors in the human body. The observation that thrombocytosis (platelet count &amp;gt;450,000/μL) occurs in patients with solid malignancies was made over 100 years ago. However, mechanisms of paraneoplastic thrombocytosis and the role that platelets play in abetting cancer growth are unclear. We have used clinical data coupled with sophisticated mouse models to identify the mechanisms and biological implications of paraneoplastic thrombocytosis. Thrombocytosis was significantly associated with advanced disease and shortened survival. Plasma levels of thrombopoietin and interleukin-6 were significantly elevated in patients who had thrombocytosis as compared with those who did not. In mouse models, increased hepatic thrombopoietin synthesis in response to tumor-derived interleukin-6 was an underlying mechanism of paraneoplastic thrombocytosis. Tumor-derived interleukin-6 and hepatic thrombopoietin were also linked to thrombocytosis in patients. Silencing thrombopoietin and interleukin-6 abrogated thrombocytosis in tumor-bearing mice. Anti–interleukin-6 antibody treatment significantly reduced platelet counts in tumor-bearing mice and in patients with epithelial ovarian cancer. In addition, neutralizing interleukin-6 significantly enhanced the therapeutic efficacy of paclitaxel in mouse models of epithelial ovarian cancer. The use of an antiplatelet antibody to halve platelet counts in tumor-bearing mice significantly reduced tumor growth and angiogenesis. Biologically, platelets were detected within the tumor microenvironment and affected tumor growth and response to chemotherapeutic agents. These findings support the existence of a paracrine circuit wherein increased production of thrombopoietic cytokines in tumor and host tissue leads to paraneoplastic thrombocytosis, which fuels tumor growth. Blocking the stimulatory effects of platelets may have implications for new therapeutic approaches. Citation Format: Anil K. Sood, Rebecca L. Stone, Vahid Afshar-Kharghan. Causes and consequences of cancer-associated thrombocytosis. [abstract]. In: Proceedings of the AACR Special Conference on Advances in Ovarian Cancer Research: From Concept to Clinic; Sep 18-21, 2013; Miami, FL. Philadelphia (PA): AACR; Clin Cancer Res 2013;19(19 Suppl):Abstract nr IA22.

Abstract 5670: Phospho-PEA-15 sensitizes ovarian cancer cells to paclitaxel by impairing the microtubule-destabilizing effect of SCLIP

Abstract Paclitaxel is a standard chemotherapeutic agent for ovarian cancer. Resistance of ovarian cancer cells to the drug has been a major obstacle in clinical practice. Thus, alternative approaches are needed to conquer the resistance. PEA-15 (phosphoprotein enriched in astrocytes-15 kDa) regulates cell proliferation and apoptosis. It is phosphorylated at S104 and S116 by Akt, PKC and CaMKII. PEA-15's functions are phosphorylation dependent. Although PEA-15 is known to mediate chemoresistance in breast cancer, the effect of PEA-15 phosphorylation status on chemosensitivity remains unknown. We hypothesized that phospho-PEA-15 (pPEA-15) enhances sensitivity of ovarian cancer cells to paclitaxel. To test our hypothesis, we silenced PEA-15 expression in HEY and OVTOKO cells using siRNA and observed a 14% reduction in apoptosis after paclitaxel exposure. To further determine if PEA-15 phosphorylation contributes to chemosensitivity, we generated SKOV3.ip1-vector (control), SKOV3.ip1-AA (AA, phosphoinhibitory at S104 and S116) and SKOV3.ip1-DD (DD, phosphomimetic at S104 and S116) stable ovarian cancer cells. Compared to the control, DD cells showed a 15% reduction in cell viability (P&amp;lt;0.01), a 92% inhibition in anchorage-independent growth (P&amp;lt;0.001), and a 15% increase in apoptosis after paclitaxel treatment. In contrast, AA cells had a 10% increase in cell viability (P&amp;lt;0.01) and a 20% decrease in apoptosis. These results indicate that pPEA-15 sensitizes ovarian cancer cells to paclitaxel. cDNA microarray analysis revealed that SCLIP, a microtubule (MT)-destabilizing phosphoprotein, was involved in pPEA-15-mediated chemosensitization. The level of SCLIP was 8.5-fold higher at mRNA and 1.6-fold higher at protein in untreated DD cells than in the control and AA cells. Interestingly, exposure to paclitaxel resulted in a 2-fold reduction in SCLIP's protein level and a dramatic increase in its phosphorylation level in DD cells. No similar changes were observed in the control and AA cells. Further, compared to the control and AA cells, higher levels of acetylated and detyrosinated α-tubulin were detected in DD cells exposed to paclitaxel, indicating that MTs are highly stabilized in treated DD cells. These results suggest that reduced expression and increased phosphorylation of SCLIP impair its MT-destabilizing effect, thereby enhancing paclitaxel sensitivity in DD cells. We demonstrate that pPEA-15 mediates chemosensitization in ovarian cancer cells by impairing the MT-destabilizing effect of SCLIP. Our findings highlight the importance of pPEA-15 as a promising target for improving the efficacy of paclitaxel-based chemotherapy in ovarian cancer. Further studies will be conducted to determine: 1) the association between pPEA-15 and SCLIP, and 2) the in vivo effectiveness of pPEA-15 in improving the therapeutic efficacy of paclitaxel in an ovarian xenograft mouse model. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 5670. doi:1538-7445.AM2012-5670

Abstract 601: Macitentan (ACT-064992), a tissue-targeting endothelin receptor antagonist enhances therapeutic efficacy of paclitaxel by modulating survival pathways in orthotopic models of metastatic human ovarian cancer

Abstract Introduction: In 2009, ovarian cancer was the leading cause of death from gynecologic cancer in the United States. Efforts to develop tools for early detection and therapeutic regimens to overcome drug resistance of the ovarian cancer have not made a significant achievement to prolong the median survial of the patients. Potential treatments for ovarian cancers that have become resistant to standard chemotherapies include modulators of tumor cell survival, such as endothelin receptor (ETR) antagonist. We investigated the therapeutic efficacy of the dual ETR antagonist, macitentan, on human ovarian cancer cells, SKOV3ip1 and IGROV1, growing orthotopically in nude mice. Materials and Methods: Mice were injected with one million cells of SKOV3ip1 or IGROV1. Ten days later, mice with established disease were randomized into vehicle (control), paclitaxel (weekly, intraperitoneal injections), macitentan (daily oral administrations) or a combination of paclitaxel and macitentan treatment groups. After 4 weeks of treatment, mice were necropsied and tumor incidence, tumor weight, and incidence of ascites were recorded. Tumor tissues were processed for immunohistochemical analyses. Results: Treatment with paclitaxel decreased tumor weight and volume of ascites. Combination therapy with macitentan and paclitaxel reduced tumor incidence and further reduced tumor weight and volume of ascites when compared with paclitaxel alone. Macitentan alone occasionally reduced tumor weight but alone had no effect on tumor incidence or ascites. Immunohistochemical analyses revealed that treatment with macitentan and macitentan plus paclitaxel inhibited the phosphorylation of ETRs and suppressed the survival pathways of tumor cells by decreasing the levels of pVEGFR2, pAkt, and pMAPK. The dose of macitentan necessary for inhibition of phosphorylation correlated with the dose required to increase antitumor efficacy of paclitaxel. Conclusion: Treatment with macitentan enhanced the cytotoxicity mediated by paclitaxel as measured by the degree of apoptosis in tumor cells and tumor-associated endothelial cells. Collectively, these results show that administration of macitentan in combination with paclitaxel prevents the progression of ovarian cancer in the peritoneal cavity of nude mice in part by inhibiting survival pathways of both tumor cells and tumor-associated endothelial cells. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 601. doi:10.1158/1538-7445.AM2011-601

Curcumin Enhances Oral Bioavailability and Anti-Tumor Therapeutic Efficacy of Paclitaxel upon Administration in Nanoemulsion Formulation

The aim of this study was to evaluate the effect of curcumin (CUR) in oral bioavailability and therapeutic efficacy of paclitaxel (PTX) administered in nanoemulsion to SKOV3 tumor-bearing nu/nu mice. Oral administration of the mice with CUR at 50 mg/kg for 3 consecutive days resulted in a down regulation of intestinal P-glycoprotein (Pgp) and cytochrome P450 3A2 (CYP3A2) protein levels. PTX, a Pgp and CYP3A2 substrate, was administered orally at 20 mg/kg in solution or nanoemulsion either as single agent or upon pretreatment with CUR at 50 mg/kg in tumor-bearing mice. Plasma AUC(0-∞) of PTX administered in nanoemulsion to CUR pretreated mice showed 4.1-fold increase relative to controls. Similarly, relative PTX bioavailability was increased by 5.2-fold, resulting in a 3.2-fold higher PTX accumulation in the tumor tissue. PTX administered in nanoemulsion to CUR pretreated mice also showed significantly enhanced anti-tumor activity. Preliminary safety evaluation showed that CUR + PTX combination did not induce any acute toxicity as measured by body weight changes, blood cell counts, liver enzyme levels, and liver histopathology. The results of this study suggest that combination of PTX and CUR, administered in nanoemulsions, could improve oral bioavailability and therapeutic efficacy in ovarian adenocarcinoma.

Abstract 5462: Enhancing efficacy of drugs by targeting CXCR2 receptor signaling for the treatment of malignant breast cancer

Abstract Breast cancer is the second most common cause of cancer death in women in the United States after lung cancer and is responsible for more than 40,000 deaths each year. Many challenges exist in the current management of advanced stage breast cancer as there are fewer recognized therapeutic strategies, often due to therapy resistance. Recent reports suggest that malignant cells that survive initial chemo- and radiation therapy often express inflammatory cytokines, which provides survival benefit making tumors resistant to further chemotherapy. The specific objective of the study is to develop strategy to manipulate chemokine-chemokine receptor network for effective therapy with limited toxicity against drug-resistant breast cancer. We investigated whether modulation of CXCR2-dependent signaling in malignant mammary tumor enhances therapeutic efficacy of chemotherapy drugs. We used mammary tumor cells expressing different levels of CXCR2 (Cl66-wt and Cl66-shCXCR2) and examined their response to Paclitaxel and Doxorubicin. We observed significant enhancement of paclitaxel and doxorubicin-mediated toxicity at concentrations 5 and 10nM in Cl66-shCXCR2 cells as compared to Cl66-wt cells. Moreover, the expression of CXCL1, a CXCR2 ligand, was increased in paclitaxel and doxorubicin treated mammary tumor cells. Paclitaxel and doxorubicin induced CXCL-1 levels was significantly lower in Cl66-shCXCR2 cells as compared to Cl66-wt cells. In vivo studies using wild type and knockdown cells showed no significant difference in the tumor growth. However, we observed a difference in the tumor growth between wild type and knockdown tumors in mice treated with 10mg/kg concentration of paclitaxel for 3 weeks after starting the treatment. When these studies were further extended there wasn't any difference between the two groups. Furthermore, we extended these studies using human breast cancer cell lines (MDA-MB231, MDA-MET, and SKBR3). MDA-MB231 and MDA-MET are triple negative and considered to be more metastatic and drug resistant than SKBR3 which is HER2-over expressing cell line. We observed differential expression of CXCR2 and its ligands in these cells. Our observation also showed significant difference in the paclitaxel and doxorubicin-mediated inhibitory response in MDA-MB231 and MDA-MET cells as compared to SKBR3 cells. Together these studies demonstrate that manipulating CXCR2-dependent activity in malignant breast cancer cells significantly enhanced therapeutic efficacy of paclitaxel and doxorubicin. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 5462.

Selective inhibition of MDR1 (ABCB1) by HM30181 increases oral bioavailability and therapeutic efficacy of paclitaxel

Multi-drug resistance 1 (MDR1, ABCB1), also known as P-glycoprotein (P-gp), restricts intestinal uptake of many drugs, and contributes to cellular resistance to cancer chemotherapy. In this study, we examined the pharmacologic characteristics of HM30181, a newly developed MDR1 inhibitor, and tested its capacity to increase the oral bioavailability and efficacy of paclitaxel, an anti-cancer drug usually given by intravenous injection. In the ATPase assay using MDR1-enriched vesicles, HM30181 showed the highest potency (IC(50)=0.63nM) among several MDR1 inhibitors, including cycloporin A, XR9576, and GF120918, and effectively blocked transepithelial transport of paclitaxel in MDCK monolayers (IC(50)=35.4nM). The ATPase inhibitory activity of HM30181 was highly selective to MDR1. HM30181 did not inhibit MRP1 (ABCC1), MRP2 (ABCC2), and MRP3 (ABCC3), and partially inhibited BCRP (ABCG2) only at very high concentrations. Importantly, co-administration of HM30181 (10mg/kg) greatly increased oral bioavailability of paclitaxel from 3.4% to 41.3% in rats. Moreover, oral co-administration of paclitaxel and HM30181 showed a tumor-inhibitory strength equal or superior to that of intravenous paclitaxel in the xenograft model in nude mice. These results identify HM30181 as a highly selective and potent inhibitor of MDR1, which in combination with paclitaxel, may provide an orally effective anti-tumor regimen.

Estrogen Receptor α Mediates Breast Cancer Cell Resistance to Paclitaxel through Inhibition of Apoptotic Cell Death

Estrogen receptors (ER) are expressed in approximately 65% of human breast cancer. Cumulative data from clinical trials and retrospective analyses suggest that some chemotherapeutic agents may be less effective in patients with ER-positive (ER+) tumors than those with ER-negative (ER-) tumors. Paclitaxel is an active agent used in breast cancer chemotherapy. To investigate the possible influence of ER on the therapeutic efficacy of paclitaxel and its underlying mechanism, we established several isogenic ER+ cell lines by stable transfection of ERalpha expression vectors into ER- breast cancer BCap37 cells. We showed that 17-beta estradiol significantly reduces the overall cytotoxicity of paclitaxel in BCap37-expressing ERalpha but has no influence on the ER- parental cells. Further analyses indicate that expression of ERalpha in BCap37 cells mainly interferes with paclitaxel-induced apoptotic cell death, without affecting paclitaxel-induced microtubule bundling and mitotic arrest. Moreover, we found that the addition of ICI 182,780 (Fulvestrant), a selective ER down-regulator, could completely reverse the resistance of ER+ BCap37 cells to paclitaxel. These findings showed that ERalpha-mediated breast tumor cell resistance to paclitaxel was through selective inhibition of paclitaxel-induced tumor cell apoptosis. Additionally, the combination of ICI 182,780 also sensitizes MCF-7 and T47D cell lines to the treatment of paclitaxel, which further confirmed the correlation between ERalpha and drug resistance in ER+ tumor cells. The results obtained from this study provide useful information for understanding ER-mediated resistance to paclitaxel and possibly other antineoplastic agents.

Novel biocompatible intraperitoneal drug delivery system increases tolerability and therapeutic efficacy of paclitaxel in a human ovarian cancer xenograft model

We compared the safety, toxicity, biocompatibility and anti-tumour efficacy of a novel chitosan-egg phosphatidylcholine (ePC) implantable drug delivery system that provides controlled and sustained release of paclitaxel (PTX(ePC)) versus commercial paclitaxel formulated in Cremophor EL (PTX(CrEL)). Toxicity studies were conducted in healthy CD-1 female mice, whereas efficacy studies were performed in the SKOV-3 xenograft model of ovarian cancer. Treatments consisted of intraperitoneal (IP) implantation of drug-free or PTX(ePC) formulations, IP bolus PTX(CrEL), or Cremophor EL (CrEL) vehicle. Toxicity was assessed as number of deaths, weight loss, serum hepatic enzyme levels and histopathological changes. Mice implanted with drug-free or PTX(ePC) formulations did not exhibit observable toxicities, local inflammation or fibrous encapsulation of the implant. In contrast, mice receiving PTX(CrEL) or CrEL encountered significant toxicity, lethality, abnormal peritoneal organ morphology and hepatic inflammation. The maximum tolerable dose (MTD) of PTX(CrEL) was 20 mg/kg/week, whereas PTX doses of up to 280 mg/kg/week were well tolerated when administered as PTX(ePC). Enhanced anti-tumour efficacy was achieved with PTX(ePC) in contrast to PTX(CrEL) with the same total dose of 60 mg/kg PTX. The novel PTX(ePC) formulation is a safer and better tolerated method for PTX administration, with significant increase in MTD and enhanced anti-tumour efficacy, suggesting improved therapeutic index with possible clinical implications in the treatment of ovarian tumours.

Glucocorticoids selectively inhibit paclitaxel-induced apoptosis: mechanisms and its clinical impact.

Paclitaxel (Taxol), a naturally occurring antimitotic agent, has shown significant cell-killing activity against tumor cells through induction of apoptosis. The mechanism by which paclitaxel induces cell death is not entirely clear. Recent studies in our laboratory discovered that glucocorticoids selectively inhibited paclitaxel-induced apoptosis without affecting the ability of paclitaxel to induce microtubule bundling and mitotic arrest. This finding implies that apoptotic cell death induced by paclitaxel may occur via a pathway independent of mitotic arrest. Through analyses of a number of apoptosis-associated genes or regulatory proteins, we found that glucocorticoids and paclitaxel possess opposite regulatory role in the NF-kappa B/Ikappa Balpha signaling pathway. Further studies indicate that paclitaxel activates Ikappa B Kinase (IKK), which in turn causes degradation of Ikappa Balpha and activation of NF-kappa B, whereas glucocorticoids antagonize paclitaxel-mediated NF-kappa B activation through induction of Ikappa Balpha synthesis. These results suggest that the NF-kappa B/Ikappa Balpha signaling pathway might play a critical role in the mediation or regulation of paclitaxel-induced cell death. On the other hand, since glucocorticoids (such as dexamethasone) are routinely used in the clinical application of paclitaxel to prevent hypersensitivity reactions and other adverse effects, the inhibitory action of glucocorticoids on paclitaxel-induced apoptosis also raises a clinically relevant question as to whether the pretreatment with glucocorticoids might interfere with the therapeutic efficacy of paclitaxel.

Raf-1 kinase activity predicts for paclitaxel resistance in TP53mut, but not TP53wt human ovarian cancer cells.

We have recently reported that there is a significant Raf-1 kinase dependency of paclitaxel resistance in human cervical tumor cell lines. In light of the possibility that Raf-1 kinase inhibitors could be used to enhance paclitaxel responsiveness in ovarian cancer, we have characterized the Raf-1 kinase dependency of paclitaxel resistance in ovarian cancer cells. The relationship between Raf-1 kinase activity and the sensitivity to clinically relevant paclitaxel concentrations was determined in four ovarian cancer cell lines (CA-OV3, SK-OV3, 2780/WT and OAW42/WT). Furthermore, in recognition that such a drug combination would initially be used in patients whose tumors have recurred following cisplatin/paclitaxel treatment, we also determined the Raf-1 kinase dependency of paclitaxel cytotoxicity in cisplatin resistant variants of two of the ovarian cell lines (2780/CP and OAW42/CP). In the two cell lines (2780/WT and OAW42/WT) that possess a wild-type TP53 (TP53wt), the relationship between Raf-1 kinase activity and paclitaxel resistance was different from that observed in the cervical tumor cell lines. In these cell lines, paclitaxel-induced far more cell killing than would have been predicted from their Raf-1 kinase activity. However, in the ovarian cancer cell lines (CA-OV3, SK-OV3, 2780/CP and OAW42/CP) that have a mutant TP53 (TP53mut), the cytotoxicity induced by 60 nM paclitaxel exhibited the same relationship to Raf-1 kinase activity as previously observed in cervical tumor cell lines. These data suggest that the therapeutic efficacy of paclitaxel in ovarian cancer patient whose tumors have TP53mut might be increased if it is administered in combination with Raf-1 kinase inhibitors, e.g., ISIS 5132.