Synergistic Effect Of Paclitaxel Research Articles

Computational and in vitro analyses on synergistic effects of paclitaxel and thymoquinone in suppressing invasive breast cancer cells.

In the present experiment, we evaluated the impact of thymoquinone (TQ) and paclitaxel (PTX) treatment on MDA-MB-231 cell line growth inhibition via controlling apoptosis/autophagy. MDA-MB-231cells were exposed to PTX (0, 25, 50, 75, and 100 nM), TQ (0, 25, 50, 75, and 100 µM), and combinations for 48h. After the MTT assessment, dose-response curves and IC50 values were calculated, and the combination synergism was evaluated using the Compusyn software. Following the treatment with PTX, TQ, and combinations at IC50 doses, the expression of apoptosis and autophagy genes was assessed in cells. The GraphPad Prism program was used to analyze the data, and Tukey's test at p < 0.05 was then run. PTX, TQ, and their combinations inhibited MDA-MB-231cell proliferation and viability dose-dependently. TQ reduced the effective concentration (IC50) of PTX in co-treatment groups. PTX and TQ showed antagonistic effects when cell proliferation declined above 70%. Antagonistic effects shifted into additive and synergistic effects upon increasing PTX concentration, indicated by diminished cell proliferation below 70%. PTX-TQ co-treatment significantly enhanced P53 and BAX expression while reducing Bcl-2 expression. Also, their combination increased Beclin-1, ATG-5, and ATG-7 expression in treated cells. Effective concentrations of TQ and PTX had synergic effects and inhibited breast cancer cells via prompting apoptosis and autophagy in vitro.

Optimizing combination therapy in prostate cancer: mechanistic insights into the synergistic effects of Paclitaxel and Sulforaphane-induced apoptosis

BackgroundCombination therapies in cancer treatment have demonstrated synergistic or additive outcomes while also reducing the development of drug resistance compared to monotherapy. This study explores the potential of combining the chemotherapeutic agent Paclitaxel (PTX) with Sulforaphane (SFN), a natural compound primarily found in cruciferous vegetables, to enhance treatment efficacy in prostate cancer.MethodsTwo prostate cancer cell lines, PC-3 and LNCaP, were treated with varying concentrations of PTX, SFN, and their combination. Cell viability was assessed using the thiazolyl blue tetrazolium bromide (MTT) assay to determine the EC50 values. Western blot analysis was conducted to evaluate the expression of Bax, Bcl2, and Caspase-3 activation proteins in response to individual and combined treatments of PTX and SFN. Fluorescent microscopy was employed to observe morphological changes indicative of apoptotic stress in cell nuclei. Flow cytometry analysis was utilized to assess alterations in cell cycle phases, such as redistribution and arrest. Statistical analyses, including Student’s t-tests and one-way analysis of variance with Tukey’s correction, were performed to determine significant differences between mono- and combination treatments.ResultsThe impact of PTX, SFN, and their combination on cell viability reduction was evaluated in a dose-dependent manner. The combined treatment enhanced PTX’s effects and decreased the EC50 values of both drugs compared to individual treatments. PTX and SFN treatments differentially regulated the expression of Bax and Bcl2 proteins in PC-3 and LNCaP cell lines, favoring apoptosis over cell survival. Our data indicated that combination therapy significantly increased Bax protein expression and the Bax/Bcl2 ratio compared to PTX or SFN alone. Flow cytometry analysis revealed alterations in cell cycle phases, including S-phase arrest and an increased population of apoptotic cells. Notably, the combination treatments did not have a discernible impact on necrotic cells. Signs of apoptotic cell death were confirmed through Caspase-3 cleavage, and morphological changes in cell nuclei were assessed via western blot and fluorescent microscopy.ConclusionThis combination therapy of PTX and SFN has the potential to improve prostate cancer treatment by minimizing side effects while maintaining efficacy. Mechanistic investigations revealed that SFN enhances PTX efficacy by promoting apoptosis, activating caspase-3, inducing nuclear morphology changes, modulating the cell cycle, and altering Bax and Bcl2 protein expression. These findings offer valuable insights into the synergistic effects of PTX and SFN, supporting the optimization of combination therapy and providing efficient therapeutic strategies in preclinical research.

Evaluation of pH-Sensitive Polymeric Micelles Using Citraconic Amide Bonds for the Co-Delivery of Paclitaxel, Etoposide, and Rapamycin.

Paclitaxel (PTX), etoposide (ETP), and rapamycin (RAPA) have different mechanisms, allowing multiple pathways to be targeted simultaneously, effectively treating various cancers. However, these drugs have a low hydrosolubility, limiting clinical applications. Therefore, we used pH-sensitive polymeric micelles to effectively control the drug release in cancer cells and to improve the water solubility of PTX, ETP, and RAPA. The synergistic effect of PTX, ETP, and RAPA was evaluated in gastric cancer, and the combination index values were evaluated. Thin-film hydration was used to prepare PTX/ETP/RAPA-loaded mPEG-pH-PCL micelles, and various physicochemical properties of these micelles were evaluated. In vitro cytotoxicity, pH-sensitivity, drug release profiles, in vivo pharmacokinetics, and biodistribution studies of PTX/ETP/RAPA-loaded mPEG-pH-PCL micelles were evaluated. In the pH-sensitivity evaluation, the size of the micelles increased more rapidly at a pH of 5.5 than at a pH of 7.4. The release rate of each drug increased with decreasing pH values in PTX/ETP/RAPA-loaded mPEG-pH-PCL micelles. In vitro and in vivo studies demonstrated that PTX/ETP/RAPA-loaded mPEG-pH-PCL micelles exhibit different drug release behaviors depending on the pH of the tumor and normal tissues and increased bioavailability and circulation time in the blood than solutions. Therefore, we propose that PTX/ETP/RAPA- loaded mPEG-pH-PCL micelles are advantageous for gastric cancer treatment in drug delivery systems.

Synergistic effect of Paclitaxel and Curcumin in nano-formulations on U87 and A549 cancer cell lines

Synergistic effect of Paclitaxel and Curcumin in nano-formulations on U87 and A549 cancer cell lines

Synergistic Antitumor Effect of Taxanes and CDK4/6 Inhibitor in Lung Cancer Cells and Mice Harboring KRAS Mutations

LY2835219 (LY), a novel CDK4/6 inhibitor, prevents cell proliferation through G1 arrest. Docetaxel (DTX) and paclitaxel (PTX) are cytotoxic drugs targeting tubulin-mediated apoptotic cell death via G2/M arrest. We evaluated the antitumor effects of DTX/PTX and LY individually and in combination in lung adenocarcinoma cells with or without KRAS mutations and xenograft mice harboring KRAS mutations. We investigated in vitro/in vivo changes in signaling molecules and analyzed cell proliferation, cycle, and apoptosis via flow cytometry and western blotting. LY cytotoxicity was dose-dependent and varied with KRAS mutation status. DTX→LY showed synergistic cytotoxicity regardless of KRAS mutation. Furthermore, the synergistic effect of PTX→LY was significantly greater than that of PTX+LY. DTX→LY remarkably reduced the number of G0/G1 cells and increased the number of G2/M arrested cells, resulting in an increase in apoptosis and subG1 cells. DTX→LY has synergistic antitumor effect in lung cancer cells and xenograft mice regardless of KRAS mutation.

Enhanced antitumor efficacy of glutathione-responsive chitosan based nanoparticles through co-delivery of chemotherapeutics, genes, and immune agents

To achieve the co-delivery of chemotherapeutic drugs, genes, and immune agents in a single nanoparticulate system, p-mercaptobenzoic acid-grafted N, N, N-trimethyl chitosan nanoparticles (MT NPs) were successfully synthesized. Paclitaxel (PTX) was encapsulated into the hydrophobic core of the MT NPs, and meanwhile, survivin shRNA-expressing plasmid (iSur-pDNA) and recombinant human interleukin-2 (rhIL-2) were loaded onto the hydrophilic shell of the MT NPs. Owing to the redox-sensitiveness of MT NPs, a rapid release of PTX was triggered by the high concentration of glutathione. The synergistic effects of PTX (1.5 mg/kg), iSur-pDNA (1.875 mg/kg), and rhIL-2 (6 × 105 IU/kg) at a low dose endowed the MT/PTX/pDNA/rhIL-2 NPs with enhanced antitumor efficacies and improved tumor-induced immunosuppression. These results demonstrated that the co-delivery of PTX, iSur-pDNA, and rhIL-2 by the amphiphilic chitosan based NPs with redox-sensitiveness could be a promising strategy in the treatment of tumors.

Anti-cancer effects of Fenbendazole and Paclitaxel combination on HL-60 cells

Fenbendazole (FBZ) is one of the safest anthelmintic drugs. FBZ has been found to have anti-cancer effects by destabilizing microtubules. In this study, a synergistic effect of paclitaxel (PA), a microtubule-stabilizing anti-cancer agent, and FBZ was investigated on HL-60 cells, a human leukemia cell line. The metabolic activity of cells significantly decreased and the nucleus morphology upon the treatment of FBZ and PA based on 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazoliumbromide assay and Hoechst 33342 staining, respectively. To investigate the involvement of reactive oxygen species (ROS), the metabolic activity of the cells after treatment of N-acetyl-L-cysteine (NAC) was measured. Indeed, NAC significantly increased the metabolic activity of the cells treated with FBZ and PA, suggesting that both drugs affect at least in part via ROS. Furthermore, FBZ and PA increased cell death in an annexin V- fluorescein isothiocyanate/propidium iodide staining assay. Taken together, FBZ and PA have a synergistic anti-cancer activity on HL-60 cells at a certain concentration. These results may provide researchers and clinicians in cancer-related fields with some valuable information to broaden the use of FBZ.

Paclitaxel and Sorafenib: The Effective Combination of Suppressing the Self-Renewal of Cancer Stem Cells.

“Combination therapy”, which is a treatment modality combining two or more therapeutic agents, is considered a cornerstone of cancer therapy. The combination of anticancer drugs, of which functions are different from the other, enhances the efficiency compared to the monotherapy because it targets cancer cells in a synergistic or an additive manner. In this study, the combination of paclitaxel and sorafenib in low concentration was evaluated to target cancer stem cells, miPS-BT549cmP and miPS-Huh7cmP cells, developed from mouse induced pluripotent stem cells. The synergistic effect of paclitaxel and sorafenib on cancer stem cells was assessed by the inhibition of proliferation, self-renewal, colony formation, and differentiation. While the IC50 values of paclitaxel and sorafenib were approximately ranging between 250 and 300 nM and between 6.5 and 8 µM, respectively, IC50 of paclitaxel reduced to 20 and 25 nM, which was not toxic in a single dose, in the presence of 1 µM sorafenib, which was not toxic to the cells. Then, the synergistic effect was further assessed for the potential of self-renewal of cancer stem cells by sphere formation ability. As a result, 1 µM of sorafenib significantly enhanced the effect of paclitaxel to suppress the number of spheres. Simultaneously, paclitaxel ranging in 1 to 4 nM significantly suppressed not only the colony formation but also the tube formation of the cancer stem cells in the presence of 1 µM sorafenib. These results suggest the combination therapy of paclitaxel and sorafenib in low doses should be an attractive approach to target cancer stem cells with fewer side effects.

Mitochondria-targeting nanomedicine self-assembled from GSH-responsive paclitaxel-ss-berberine conjugate for synergetic cancer treatment with enhanced cytotoxicity

Mitochondria play a fundamental role in plenty of cellular metabolic processes, and mitochondria-homing drug delivery is a promising and effective strategy for cancer treatment. Paclitaxel (PTX) is a broad-spectrum anticancer drug, but its therapeutic effect is highly limited due to the development of multidrug resistance. Berberine (BBR) can selectively accumulate in tumor cell mitochondria and inhibit the growth of cancer cells with different biological action mechanism from PTX. Here, these two “old” drug molecules, BBR and PTX were linked together by a disulfide bond rope to construct GSH-responsible drug-drug conjugate (PTX-ss-BBR). Molecular dynamics simulation results revealed that PTX-ss-BBR conjugate could be self-assembled in water to form nanoparticles (PTX-ss-BBR NPs) forced by π-π stacking and hydrophobic interactions and the average size of NPs was around 165 nm measured by DLS. The better in vitro potency of PTX-ss-BBR NPs against A549 cells might be ascribed to the simultaneous drug release and mitochondria-targeting delivery, which dissipated mitochondria membrane potential, upregulated ROS levels in cancer cells, arrested cells in phase G2/M, elicited apoptosis of cancer cells and inhibited the growth of tumors. Furthermore, PTX-ss-BBR NPs also exerted efficacy better than or comparable to BBR on S. aureus and E. coli, which were closely associated with the development of lung cancer. The synergistic effect of PTX and BBR enhanced the treatment effect of conventional chemotherapy drugs against A549 cells.

125Incidence and outcomes of bailout stenting following use of drug coated balloon

Abstract Background The incidence of bailout stenting post-drug coated balloon use (DCB) in the literature has been more than 10%; ranging up-to 21% in Bello trial and this variation could be due to the different criteria used to consider bailout stenting and may also reflect aggressive pre-dilatation. Our eyes are trained to expect stent like result and anything less is considered sub-optimal and this could be one of the reasons for high incidence of bailout stenting. The current recommendation is to use drug eluting stent (DES) for bailout stenting and hence raising in the possibility of drug toxicity or maybe even synergistic effect from combination of Paclitaxel (DCB) and limus (DES). Aim We have evaluated the incidence and outcomes of patients needing bailout stenting in our centre. Methods and results We evaluated all patients who were treated with DCB between January 2016-August 2017. Bailout stenting per lesion were identified and studied for endpoints which included cardiac death, target vessel MI, stent thrombosis, target lesion revascularization and target vessel revascularisation. Between the study period; 468 lesions (in 364 patients) were treated with paclitaxel DCB (Sequent Please, B Braun, Germany). Bailout stenting was required in 23 lesions (4.9%) and of which 12 (52%) was for flow limiting dissections (type C or more) and the remaining 11 was for recoil of more than 50%. Majority of the lesions were de novo (18; 78%). All bailout stenting was performed with third generation limus eluting stents. During a median follow-up of 18.14 months; range; 7–33 months, there was no cardiac death and target vessel MI occurred in 1 patient (4.3%), TLR and TVR were in 3 lesions (13%). MACE rate (combination of cardiac death, target vessel MI and TVR) was 13%. There were no cases of stent thrombosis as per the ARC definition. Conclusion One of the highlighting features of our study is very low-rates of bailout stenting. This may be due to our criteria of not stenting mild dissections (unless they are flow limiting) and also to accepting recoil of up-to 50% post-DCB use. The outcome in bailout stenting group is acceptable especially with hard endpoints (cardiac death, target vessel MI and stent thrombosis) although TLR and TVR rates were higher indicating synergistic effect of paclitaxel and limus may not offer additional benefits.

Synergistic Anticancer Effect of a Combination of Paclitaxel and 5-Demethylnobiletin Against Lung Cancer Cell Line In Vitro and In Vivo.

Lung cancer remains a highly prevalent disease and a leading cause of cancer-related deaths worldwide. Currently, exploring antitumor drugs derived from herbs used in traditional Chinese medicine is increasingly becoming an attractive area of research. Paclitaxel (PTX), a highly effective chemotherapeutic drug, is widely used for treating different cancers; however, the clinical use of PTX is dose limited because of its adverse side effects. Chemotherapeutic agents are being developed to enhance the anticancer activity of PTX, particularly for use in combination therapy. 5-Demethylnobiletin (5-DMN), a natural, active compound isolated from orange peel, has been reported to induce apoptosis in several cancer cell lines. In this study, we tested the synergistic anticancer antiproliferative effects of combinations of PTX and 5-DMN on CL1-5 lung cancer cells through the MTT and propidium iodide assays. After low-dose combination treatments (PTX and 5-DMN), a reduction in cell viability and a concomitant increase in apoptosis were observed in the CL1-5 cells. We propose that 5-DMN cooperates with PTX to induce apoptosis via the caspase pathway (by modulating caspase-3, caspase-8, and caspase-9 activities). Furthermore, we observed that the combination treatment significantly suppressed tumor growth in the nude mouse xenograft model. The results suggest that the synergistic effects of PTX and 5-DMN in lung cancer cells deserve particular attention and indicate the possibility of developing additional new strategies for treating lung cancer.

A Bimetallic Silver-Neodymium Theranostic Nanoparticle with Multimodal NIR/MRI/CT Imaging and Combined Chemo-photothermal Therapy.

An engineered metallic nanostructure is an excellent candidate for "theranosis" of cancer, having intrinsic properties of multimodal imaging and therapy. Toward this target, the development of silver-neodymium bimetallic nanoparticles (Ag-Nd BNPs) via microwave-assisted polyol synthesis is presented. The resultant Ag-Nd BNPs exhibit good monodispersity with average size of 10 nm, fluorescence in the near-infrared (NIR) region, and magnetic properties. The Ag-Nd BNPs also validate MRI, CT, and NIR trimodal imaging ability and enunciate valuable temperature response upon irradiation under a NIR laser. Aided by chitosan functionalization on the surface, the Ag-Nd BNPs deliver good biocompatibility and also promote the loading of paclitaxel, an anticancer drug. Isothermal titration calorimetry affirms the combination of strong binding affinity of drug and high loading efficiency of 7 drug molecules per nanoparticle. Moreover, Ag-Nd BNPs also illustrate a highly efficient photothermal effect in PBS. Therefore, the synergistic effects of paclitaxel and the photothermal effect make BNPs excellent "combined therapeutic agents", and also give them the important ability to destroy cancer cells in vitro at very low dose in comparison to single therapy. Thus, the Ag-Nd BNPs unveil a combination of MRI/CT/NIR imaging and chemo-photothermal therapy that ensures accurate diagnosis at an early stage and comprehensive eradication of tumor cells without affecting healthy cells.

SET antagonist enhances the chemosensitivity of non-small cell lung cancer cells by reactivating protein phosphatase 2A.

SET is known as a potent PP2A inhibitor, however, its oncogenic role including its tumorigenic potential and involvement in the development of chemoresistance in non-small cell lung cancer (NSCLC) has not yet been fully discussed. In present study, we investigated the oncogenic role of SET by SET-knockdown and showed that SET silencing impaired cell growth rate, colony formation and tumor sphere formation in A549 cells. Notably, silencing SET enhanced the pro-apoptotic effects of paclitaxel, while ectopic expression of SET diminished the sensitivity of NSCLC cells to paclitaxel. Since the SET protein was shown to affect chemosensitivity, we next examined whether combining a novel SET antagonist, EMQA, sensitized NSCLC cells to paclitaxel. Both the in vitro and in vivo experiments suggested that EMQA and paclitaxel combination treatment was synergistic. Importantly, we found that downregulating p-Akt by inhibiting SET-mediated protein phosphatase 2A (PP2A) inactivation determined the pro-apoptotic effects of EMQA and paclitaxel combination treatment. To dissect the critical site for EMQA functioning, we generated several truncated SET proteins. By analysis of the effects of EMQA on the binding affinities of different truncated SET proteins to PP2A-catalytic subunits, we revealed that the 227-277 amino-acid sequence is critical for EMQA-induced SET inhibition. Our findings demonstrate the critical role of SET in NSCLC, particularly in the development of chemoresistance. The synergistic effects of paclitaxel and the SET antagonist shown in current study encourage further validation of the clinical potential of this combination.

Paclitaxel and trastuzumab treatment affects insulin growth factor I expression in breast cancer cell lines

&lt;p class="Abstract"&gt;Breast cancer is the most common type of cancers and second primary cause of death among women. Insulin-like growth factor I (IGF-1) signaling pathway plays a vital role in cancer cell survival, proliferation, chemotaxis and angiogenesis. In this study, the effect of combination of two drugs, paclitaxel and trastuzumab on IGF signaling and cell cycle arrest in breast cancer cell lines, T47D and Hs0578T were explored. The interaction of paclitaxel and trastuzumab on IGF-1 signaling pathway was studied with IGF-1 and phosphoinositide 3-kinase inhibitor, LY294002. The protein expression of IGF signaling molecules were reduced in the drug treated cancer cells. LY294002 and IGF-1 with paclitaxel and trastuzumab treatment inhibited phosphorylated Akt. During G0/G1 phase, cell cycle arrest and accumulation of apoptotic cells were observed in drug treated cancer cells. The synergistic effect of paclitaxel and trastuzumab decreased the multiplication of breast cancer cells by altering the expression of IGF-I signaling molecules. This combination proves to be one of the useful methods to treat breast cancer.&lt;/p&gt;&lt;p&gt; &lt;/p&gt;

Differential Network Analysis Applied to Preoperative Breast Cancer Chemotherapy Response

In silico approaches are increasingly considered to improve breast cancer treatment. One of these treatments, neoadjuvant TFAC chemotherapy, is used in cases where application of preoperative systemic therapy is indicated. Estimating response to treatment allows or improves clinical decision-making and this, in turn, may be based on a good understanding of the underlying molecular mechanisms. Ever increasing amounts of high throughput data become available for integration into functional networks. In this study, we applied our software tool ExprEssence to identify specific mechanisms relevant for TFAC therapy response, from a gene/protein interaction network. We contrasted the resulting active subnetwork to the subnetworks of two other such methods, OptDis and KeyPathwayMiner. We could show that the ExprEssence subnetwork is more related to the mechanistic functional principles of TFAC therapy than the subnetworks of the other two methods despite the simplicity of ExprEssence. We were able to validate our method by recovering known mechanisms and as an application example of our method, we identified a mechanism that may further explain the synergism between paclitaxel and doxorubicin in TFAC treatment: Paclitaxel may attenuate MELK gene expression, resulting in lower levels of its target MYBL2, already associated with doxorubicin synergism in hepatocellular carcinoma cell lines. We tested our hypothesis in three breast cancer cell lines, confirming it in part. In particular, the predicted effect on MYBL2 could be validated, and a synergistic effect of paclitaxel and doxorubicin could be demonstrated in the breast cancer cell lines SKBR3 and MCF-7.

Synergistic effect of paclitaxel and epigenetic agent phenethyl isothiocyanate on growth inhibition, cell cycle arrest and apoptosis in breast cancer cells

This study examined whether combining paclitaxel (taxol) with a novel epigenetic agent phenethyl isothiocyanate (PEITC) will yield a synergistic effect on inhibiting breast cancer cells. Two drug-resistant breast cancer cell lines, MCF7 and MDA-MB-231, were treated with PEITC and taxol. Cell growth, cell cycle, and apoptosis were examined. The combination of PEITC and taxol significantly decreased the IC50 of PEITC and taxol over each agent alone. The combination also increased apoptosis by more than two fold over each single agent in both cell lines. A significant increase of cells in the G2/M phases was detected. In conclusion, the combination of PEITC and taxol exhibits a synergistic effect on growth inhibition in breast cancer cells. This combination deserves further study in vivo.

Combined-modality radioimmunotherapy: synergistic effect of paclitaxel and additive effect of bevacizumab

This study was undertaken to investigate the effect of paclitaxel and bevacizumab on the therapeutic efficacy of (90)Y-labeled B3 monoclonal antibody, directed against Le(y) antigen, for the treatment of Le(y)-positive A431 tumors implanted subcutaneously in the right hind flank of nude mice. When the tumor size reached ~200 mm(3), the mice received a single dose of intravenous (iv) (90)Y-labeled B3 (60 μCi/150 μg or 100 μCi/150 μg B3), intraperitoneal paclitaxel (40 mg/kg) or iv bevacizumab (5 mg/kg) for monotherapy. To investigate the effect of combined therapies on survival, the mice were treated with two or three agents in the following combinations: (90)Y-B3 on day 0 and paclitaxel on day 1; bevacizumab on -1 day and (90)Y-B3 on day 0; bevacizumab on -1 day and paclitaxel on day 1; bevacizumab, (90)Y-B3 and paclitaxel each at 1-day intervals. The mice with no treatment were used as a control. The tumor volume at 1000 mm(3) was used as a surrogate end point of survival. Compared to control animals, paclitaxel delayed tumor growth with a significantly longer median survival time (P<.001), whereas bevacizumab alone showed a less pronounced effect on a median survival time (P=.18). (90)Y-B3 increased the median survival time in a dose-dependent manner (P<.05). The combined therapy of bevacizumab with paclitaxel produced a trend toward an increase of the median survival time compared to paclitaxel alone (P=.06), whereas bevacizumab combined with (90)Y-B3 showed a statistically insignificant increase in the median survival time compared to (90)Y-B3 alone (P=.25). The tumor sizes of all animals in these groups reached the surrogate end point of survival by day 35. In contrast, the combined therapy involving (90)Y-B3 with paclitaxel showed a striking synergistic effect in shrinking tumors and prolonging the survival time (P<.001); on day 120, three of nine mice (33%) and six of six mice (100%) were alive without tumor when treated with 60 μCi (90)Y-B3 and 100 μCi (90)Y-B3, respectively. The addition of bevacizumab treatment 1 day before the combined therapy of 60 μCi (90)Y-B3 with paclitaxel did not produce a statistically significant increase in survival when compared to the (90)Y-B3 with paclitaxel (P>.10). Fluorescence microscopy analysis indicated that paclitaxel increased, whereas bevacizumab decreased, the accumulation and penetration of Alexa Fluor 647-B3 into tumor microenvironment compared to the control (P<.05). Our findings on the paclitaxel effect support a hypothesis that the increased tumor accumulation and penetration of (90)Y-B3 as well as the high radiosensitization of tumor cells by paclitaxel may be the major factors responsible for the synergistic effect of the combined therapy involving (90)Y-B3 with paclitaxel.

Preclinical Evaluation of Gemcitabine Combination Regimens for Application in Acute Myeloid Leukemia

The DNA antimetabolite gemcitabine is an anticancer agent with shown preclinical and clinical utility and a low toxicity profile. In this study, we sought to identify and optimize drug partners for binary and tertiary combinations with gemcitabine for use in the treatment of acute myelogenous leukemia (AML). Drug interaction was assessed by growth inhibition assay with metabolic end points. The combination index method was used to evaluate combinations of gemcitabine with fludarabine, paclitaxel, chlorambucil, doxorubicin, mitoxantrone, and SN-38 in U937 human AML cells. A three-dimensional method was used to determine the effect of dose ratio and schedule on drug interaction. Mechanisms underlying interactions related to cell cycle effects and apoptosis were assessed by flow cytometric and caspase-3 and -7 assays, respectively. The most synergistic binary combination was gemcitabine + fludarabine. The most synergistic tertiary combination was gemcitabine + fludarabine + paclitaxel, where the interaction was sequence dependent with paclitaxel given before gemcitabine + fludarabine, producing a 2-fold increase in synergy. Cell cycle analysis did not reveal a significant G(2)-M arrest, suggesting that the synergistic effect of paclitaxel in this combination, which produced the greatest caspase activation, might be independent of microtubule stabilization. In contrast, the gemcitabine + fludarabine + mitoxantrone combination was synergistic and schedule independent. Moreover, few ratios of gemcitabine + fludarabine to mitoxantrone were antagonistic, which could be important for clinical translation. In conclusion, synergistic interactions with gemcitabine occurred with several drugs, the most promising being gemcitabine + fludarabine, gemcitabine + fludarabine + paclitaxel, and gemcitabine + fludarabine + mitoxantrone. These findings provided a rationale for clinical trials of gemcitabine + fludarabine and gemcitabine + mitoxantrone where responses were observed in heavily pretreated AML patients.

Phosphorylation of FADD is critical for sensitivity to anticancer drug-induced apoptosis.

FADD has been shown to be phosphorylated at Ser194 at the G2/M transition of the cell cycle. Here we have investigated the contribution of this phosphorylation to apoptosis induced by anticancer drugs in two human prostate cancer cell lines, LNCaP and DU145. Both were arrested at G2/M and FADD was found to be phosphorylated at Ser194 on treatment with paclitaxel. Inhibition of paclitaxel-induced c-jun NH2-terminal kinase (JNK) activation by treatment with a specific inhibitor, SP600125, or overexpression of a dominant-negative mutant form of upstream kinases, MEK kinase 1 (MEKK1) and mitogen-activated protein kinase kinase (MKK) 7, significantly reduced the increase in phosphorylated FADD. It is noteworthy that pretreatment with paclitaxel significantly up-regulated MEKK1 expression, resulting in enhancement of etoposide- or cisplatin-induced MEKK1/MKK7-dependent JNK activation and apoptosis in LNCaP and DU145 cells. Interestingly, MEKK1 up-regulation and the synergistic effects of paclitaxel on anticancer drug-induced apoptosis were abolished by overexpression of mutant FADD (Ser194-->Ala). The results clearly show that FADD phosphorylation at Ser194 affects functions both upstream and downstream of the MEKK1/MKK7/JNK1 pathway and is closely associated with chemosensitivity in prostate cancer cells. This is the first report indicating that phosphorylated FADD plays an essential role in the mechanisms of amplifications of chemotherapy-induced apoptosis.

Synergistic effect of paclitaxel and 4-hydroxytamoxifen on estrogen receptor-negative colon cancer and lung cancer cell lines.

Antiestrogen tamoxifen (Tam) is the most prescribed drug for the treatment of estrogen receptor (ER)-positive breast cancers. It is also used in long-term clinical trials with encouraging preliminary results as a chemopreventive agent for breast cancer. The effect of Tam on ER-negative cancers, however, is unclear. Here we reported that paclitaxel and 4-hydroxytamoxifen (4-HT) have a synergistic cytotoxic effect on the ER-negative colon cancer cell line HCT15, which is refractory to paclitaxel alone. Our results showed that 4-HT at submicromolar concentrations effectively enhanced the antiproliferative effect of paclitaxel. In addition, at 1/10 of the paclitaxel concentrations used for HCT15, 4-HT and paclitaxel also showed synergistic effect on NCI H460, an ER-negative lung cancer cell line. For both cell lines, the effective concentration for paclitaxel to inhibit cell growth was 1 log lower in the combination treatment than the concentration used in the single treatment. Cell cycle analysis showed that the combination of paclitaxel and 4-HT increased the G2/M population and resulted in the increase of apoptosis in both cell lines. Enhanced early release of cytochrome c from mitochondria may be the apoptotic pathway activated in the combination treatment in HCT15 cells.