Thymosin Beta-4, Actin-Sequestering Protein Regulates Vascular Endothelial Growth Factor Expression via Hypoxia-Inducible Nitric Oxide Production in HeLa Cervical Cancer Cells

Nuclear factor (erythroid-derived 2)-like 2 counter-regulates thymosin beta-4 expression and primary cilium formation for HeLa cervical cancer cell survival

We investigated the function of thymosin beta-4 (TB4) expression and primary cilium (PC) formation via the underlying Nrf2-dependent mechanism for cervical cancer cell (CC) survival under conditions of serum deprivation (SD). TB4 silencing was achieved using RNA interference. The percentage of PC formation was analyzed by immunofluorescence staining. Nrf2 expression was modified by the preparation of stable Nrf2-knockdown cells with shNrf2 and the overexpression of Nrf2 with pcDNA-Nrf2 plasmids. Gene expression was measured using reverse-transcription PCR, Gaussia luciferase assay, and western blotting. Cell viability was assessed using the MTT assay or CellTiter Glo assay. Reactive oxygen species (ROS) were detected with flow cytometry. CCs incubated in SD without fetal bovine serum remained viable, and SD increased PC formation and TB4 transcription. CC viability was further decreased by treatment with ciliobrevin A to inhibit PC formation or TB4-siRNA. SD increased ROS, including H₂O₂. N-acetylcysteine inhibited ROS production following H₂O₂ treatment or SD, which also decreased PC formation and TB4 transcription. Meanwhile, H₂O₂ increased PC formation, which was attenuated in response to TB4 siRNA. Treatment with H₂O₂ increased Nrf2 expression, antioxidant responsive element (ARE) activity, and PC formation, which were inhibited by the Nrf2 inhibitor clobestasol propionate. Nrf2 knockdown via expression of Tet-On shNrf2 enhanced ROS production, leading to increased PC formation and decreased TB4 expression; these effects were counteracted by Nrf2 overexpression. Our data demonstrate that Nrf2 counter-regulates TB4 expression and PC formation for CC survival under conditions of SD, suggesting cervical CC survival could be upregulated by PC formation via Nrf2 activation and TB4 expression.

Gasotransmitters in the tumor microenvironment: Impacts on cancer chemotherapy (Review)

Nitric oxide, carbon monoxide and hydrogen sulfide are three endogenous gasotransmitters that serve a role in regulating normal and pathological cellular activities. They can stimulate or inhibit cancer cell proliferation and invasion, as well as interfere with cancer cell responses to drug treatments. Understanding the molecular pathways governing the interactions between these gases and the tumor microenvironment can be utilized for the identification of a novel technique to disrupt cancer cell interactions and may contribute to the conception of effective and safe cancer therapy strategies. The present review discusses the effects of these gases in modulating the action of chemotherapies, as well as prospective pharmacological and therapeutic interfering approaches. A deeper knowledge of the mechanisms that underpin the cellular and pharmacological effects, as well as interactions, of each of the three gases could pave the way for therapeutic treatments and translational research.

2-Arachidonyl-lysophosphatidylethanolamine Induces Anti-Inflammatory Effects on Macrophages and in Carrageenan-Induced Paw Edema

2-Arachidonyl-lysophosphatidylethanolamine, shortly 2-ARA-LPE, is a polyunsaturated lysophosphatidylethanolamine. 2-ARA-LPE has a very long chain arachidonic acid, formed by an ester bond at the sn-2 position. It has been reported that 2-ARA-LPE has anti-inflammatory effects in a zymosan-induced peritonitis model. However, it’s action mechanisms are poorly investigated. Recently, resolution of inflammation is considered to be an active process driven by M2 polarized macrophages. Therefore, we have investigated whether 2-ARA-LPE acts on macrophages for anti-inflammation, whether 2-ARA-LPE modulates macrophage phenotypes to reduce inflammation, and whether 2-ARA-LPE is anti-inflammatory in a carrageenan-induced paw edema model. In mouse peritoneal macrophages, 2-ARA-LPE was found to inhibit lipopolysaccharide (LPS)-induced M1 macrophage polarization, but not induce M2 polarization. 2-ARA-LPE inhibited the inductions of inducible nitric oxide synthase and cyclooxygenase-2 in mouse peritoneal macrophages at the mRNA and protein levels. Furthermore, products of the two genes, nitric oxide and prostaglandin E₂, were also inhibited by 2-ARA-LPE. However, 1-oleoyl-LPE did not show any activity on the macrophage polarization and inflammatory responses. The anti-inflammatory activity of 2-ARA-LPE was also verified in vivo in a carrageenan-induced paw edema model. 2-ARA-LPE inhibits LPS-induced M1 polarization, which contributes to anti-inflammation and suppresses the carrageenan-induced paw edema in vivo.

Di-(2-ethylhexyl) phthalate-induced tumor growth is regulated by primary cilium formation via the axis of H2O2 production-thymosin beta-4 gene expression

Di-(2-ethylhexyl) phthalate (DEHP) that is one of the most commonly used phthalates in manufacturing plastic wares regulates tumorigenesis. Thymosin beta-4 (TB4), an actin-sequestering protein, has been reported as a novel regulator to form primary cilia that are antenna-like organelles playing a role in various physiological homeostasis and pathological development including tumorigenesis. Here, we investigated whether DEHP affects tumor growth via primary cilium (PC) formation via the axis of TB4 gene expression and the production of reactive oxygen species (ROS). Tumor growth was increased by DEHP treatment that enhanced TB4 expression, PC formation and ROS production. The number of cells with primary cilia was enhanced time-dependently higher in HeLa cells incubated in the culture medium with 0.1% fetal bovine serum (FBS). The number of cells with primary cilia was decreased by the inhibition of TB4 expression. The incubation of cells with 0.1% FBS enhanced ROS production and the transcriptional activity of TB4 that was reduced by ciliobrevin A (CilioA), the inhibitor of ciliogenesis. ROS production was decreased by catalase treatment but not by mito-TEMPO, which affected to PC formation with the same trend. H₂O₂ production was reduced by siRNA-based inhibition of TB4 expression. H₂O₂ also increased the number of ciliated cells, which was reduced by siRNA-TB4 or the co-incubation with CilioA. Tumor cell viability was maintained by ciliogenesis, which was correlated with the changes of intracellular ATP amount rather than a simple mitochondrial enzyme activity. TB4 overexpression enhanced PC formation and DEHP-induced tumor growth. Taken together, data demonstrate that DEHP-induced tumor growth might be controlled by PC formation via TB4-H₂O₂ axis. Therefore, it suggests that TB4 could be a novel bio-marker to expect the risk of DEHP on tumor growth.

Curcumin-induced cell death depends on the level of autophagic flux in A172 and U87MG human glioblastoma cells

Glioblastoma is the deadliest neoplasm with the worst 5-year survival rate among all human cancers. Autophagy promotes autophagic cell death or blocks the induction of apoptosis in eukaryotic cells. Here, we investigated whether varying levels of autophagic flux in glioblastoma lead to different efficacies of curcumin treatment using U87MG and A172 human glioblastoma cells. The number of LC3 puncta, the number of cells with LC3 puncta and the level of LC3 II, Atg5 and Atg7 protein were higher in U87MG cells compared with A172 cells. When the cells were incubated with curcumin for 24 or 48 h, the percentage of cell death was higher in A172 cells compared with U87MG cells. Although the level of LC3 was lower, that of curcumin-induced LC3 was higher, in A172 cells than in U87MG cells. The relative increases in cell death and LC3-mediated autophagy were greater under serum starvation in A172 cells compared with U87MG cells. Curcumin-induced A172 cell death was reduced by serum starvation. When both types of cells were transfected with LC3-GFP, the percentage of cell death was higher in A172 cells than that in U87MG cells. Taken together, the data demonstrate that curcumin-mediated tumor cell death is regulated by the basal level of autophagic flux in different glioblastoma cells. This suggests that prior to the use of various curcumin therapeutics, the level of basal or induced autophagic flux should be carefully examined in tumor cells for the best efficacy.

Synovial Cell Migration is Associated with B Cell Activating Factor Expression Increased by TNFα or Decreased by KR33426

Fibroblast-like synoviocytes (FLS) play a crucial role in initiating rheumatoid arthritis. B-cell activating factor (BAFF) plays a role in FLS survival as well as in B cell maturation and maintenance. Here, we investigated whether tumor necrosis factor (TNF)-α-induced BAFF expression controls FLS migration and whether BAFF expression in FLS could be regulated by KR33426 which is the inhibitor of BAFF binding to BAFF receptors (BAFF-R) by using MH7A synovial cells transfected with the SV40 T antigen. More TNF-α-treated cells migrated compared to the control. TNF-α increased BAFF expression in FLS, significantly. FLS migration was inhibited by the transfection with BAFF-siRNA. KR33426 also inhibited BAFF expression increased by TNF-α treatment in FLS as judged by western blotting, PCR, and transcriptional activity assay. Kinases including JNK, p38 and Erk were activated by TNF-α treatment. While JNK and p38 were inhibited by KR33426 treatment, no changes in Erk were observed. Transcription factors including p65, c-Fos, CREB and SP1 were enhanced by TNF-α treatment. Among them, c-Fos was inhibited by KR33426 treatment. Small interference(si)-RNA of c-fos decreased BAFF transcriptional activity. FLS migration induced by TNF-α was inhibited by the transfection with BAFF-siRNA. KR33426 increased Twist, Snail, Cadherin-11 and N-Cadherin. In contrast, KR33426 decreased E-cadherin and TNF-α-enhanced CCL2. Taken together, our results demonstrate that synovial cell migration via CCL2 expression could be regulated by BAFF expression which is decreased by KR33426 and c-Fos-siRNA. It suggests for the first time that the role of BAFF-siRNA on FLS migration might be matched in the effect of KR33426 on BAFF expression.

Curcumin-Induced Autophagy Augments Its Antitumor Effect against A172 Human Glioblastoma Cells

Glioblastoma is the most aggressive common brain tumor in adults. Curcumin, from Curcuma longa, is an effective antitumor agent. Although the same proteins control both autophagy and cell death, the molecular connections between them are complicated and autophagy may promote or inhibit cell death. We investigated whether curcumin affects autophagy, which regulates curcumin-mediated tumor cell death in A172 human glioblastoma cells. When A172 cells were incubated with 10 μM curcumin, autophagy increased in a time-dependent manner. Curcumin-induced cell death was reduced by co-incubation with the autophagy inhibitors 3-methyladenine (3-MA), hydroxychloroquine (HCQ), and LY294002. Curcumin-induced cell death was also inhibited by co-incubation with rapamycin, an autophagy inducer. When cells were incubated under serum-deprived medium, LC3-II amount was increased but the basal level of cell viability was reduced, leading to the inhibition of curcumin-induced cell death. Cell death was decreased by inhibiting curcumin-induced autophagy using small interference RNA (siRNA) of Atg5 or Beclin1. Therefore, curcumin-mediated tumor cell death is promoted by curcumin-induced autophagy, but not by an increase in the basal level of autophagy in rapamycin-treated or serum-deprived conditions. This suggests that the antitumor effects of curcumin are influenced differently by curcumin-induced autophagy and the prerequisite basal level of autophagy in cancer cells.

Pathophysiological Role of S-Nitrosylation and Transnitrosylation Depending on S-Nitrosoglutathione Levels Regulated by S-Nitrosoglutathione Reductase

Nitric oxide (NO) mediates various physiological and pathological processes, including cell proliferation, differentiation, and inflammation. Protein S-nitrosylation (SNO), a NO-mediated reversible protein modification, leads to changes in the activity and function of target proteins. Recent findings on protein-protein transnitrosylation reactions (transfer of an NO group from one protein to another) have unveiled the mechanism of NO modulation of specific signaling pathways. The intracellular level of S-nitrosoglutathione (GSNO), a major reactive NO species, is controlled by GSNO reductase (GSNOR), a major regulator of NO/SNO signaling. Increasing number of GSNOR-related studies have shown the important role that denitrosylation plays in cellular NO/SNO homeostasis and human pathophysiology. This review introduces recent evidence of GSNO-mediated NO/SNO signaling depending on GSNOR expression or activity. In addition, the applicability of GSNOR as a target for drug therapy will be discussed in this review.

Tβ4 Increases Neovascularization and Cardiac Function in Chronic Myocardial Ischemia of Normo- and Hypercholesterolemic Pigs

Translations of new therapeutic options for cardiovascular disease from animal studies into a clinical setting have been hampered, in part by an improper reflection of a relevant patient population in animal models. In this study, we investigated the impact of thymosin β4 (Tβ4), which promotes collateralization and capillarization, during hypercholesterolemia, a known risk factor of coronary artery disease. Initial in vitro results highlighted an improved endothelial cell function upon Tβ4 treatment under control conditions and during hypercholesterolemic stress (scratch area [pixels]: oxidized low-density lipoprotein [oxLDL], 191,924 ± 7,717; and oxLDL + Tβ4, 105,621 ± 11,245). To mimic the common risk factor of hypercholesterolemia in vivo, pigs on regular (NC) or high-fat (HC) diet underwent chronic myocardial ischemia followed by recombinant adeno-associated virus (rAAV)-mediated transduction of Tβ4 or LacZ as a control. We show that Tβ4 overexpression improves capillarization and collateralization (collaterals: NC + rAAV.LacZ, 2.1 ± 0.5; NC + rAAV.Tβ4, 6.7 ± 0.5; HC + rAAV.LacZ, 3.0 ± 0.3; and HC + rAAV.Tβ4, 6.0 ± 0.4), ultimately leading to an improved myocardial function in both diet groups (ejection fraction [EF] at day 56 [%]: NC + rAAV.LacZ, 26 ± 1.1; NC + rAAV.Tβ4, 45 ± 1.5; HC + rAAV.LacZ, 26 ± 2.5; and HC + rAAV.Tβ4, 41 ± 2.6). These results demonstrate the potency of Tβ4 in a patient-relevant large animal model of chronic myocardial ischemia.

Di-(2-ethylhexyl) phthalate enhances melanoma tumor growth via differential effect on M1-and M2-polarized macrophages in mouse model

Phthalates are widely used as plasticizers that influence sexual and reproductive development. Here, we investigated whether di-(2-ethylhexyl) phthalate (DEHP) affects macrophage polarization that are associated with tumor initiation and progression. No changes were observed in LPS- or ConA-stimulated in vitro spleen B or T cell proliferation for 48 h, respectively. In contrast, macrophage functions were inhibited in response to DEHP for 12 h as judged by LPS-induced H₂O₂ and NO production and zymosan A-mediated phagocytosis. When six weeks old male mice were pre-exposed to 4.0 mg/kg DEHP for 21 days before the injection of B16F10 melanoma cells and post-exposed to 4.0 mg/kg DEHP for 7 days, tumor nodule formation and the changes in tumor volume were higher than those in control group. Furthermore, when male mice were intraperitoneally pretreated with DEHP for 3 or 4 weeks and peritoneal exudate cells (PECs) or bone marrow-derived macrophages (BMDMs) were incubated with lipopolysaccharide (LPS), the expression of COX-2, TNF-α, and IL-6 was reduced in DEHP-pretreated cells as compared with that in LPS-stimulated control cells. While the production of nitric oxide (NO) for 18 h was reduced by LPS-stimulated PECs and M1-type BMDMs, IL-4 expression was enhanced in LPS-stimulated BMDMs. When BMDMs were incubated with IL-4 for 30 h, arginase 1 for M2-type macrophages was increased in transcriptional and translational level. Data implicate that macrophages were differentially polarized by DEHP treatment, which reduced M1-polarzation but enhanced M2-polarization. Taken together, these data demonstrate that DEHP could affect in vivo immune responses of macrophages, leading to the suppression of their tumor-preventing ability. This suggests that individuals at high risk for tumor incidence should avoid long-term exposure to various kind of phthalate including DEHP.

Trichostatin A resistance is facilitated by HIF-1α acetylation in HeLa human cervical cancer cells under normoxic conditions

Trichostatin A (TSA) is an anticancer drug that inhibits histone deacetylases (HDACs). Hypoxia-inducible factor 1 (HIF-1) participates in tumor angiogenesis by upregulating target genes, such as vascular endothelial growth factor (VEGF). In the present study, we investigated whether TSA treatment increases HIF-1α stabilization via acetylation under normoxic conditions, which would lead to VEGF upregulation and resistance to anticancer drugs. TSA enhanced total HIF-1α and VEGF-HRE reporter activity under normoxic conditions. When cells were transfected with GFP-HIF-1α, treatment with TSA increased the number of green fluorescence protein (GFP)-positive cells. TSA also enhanced the nuclear translocation of HIF-1α protein, as assessed by immunoblotting and as evidenced by increased nuclear localization of GFP-HIF-1α. An increase in the interaction between HIF-1α and the VEGF promoter, which was assessed by a chromatin immunoprecipitation (ChIP) assay, led to activation of the VEGF promoter. TSA acetylated HIF-1α at lysine (K) 674, which led to an increase in TSA-induced VEGF-HRE reporter activity. In addition, TSA-mediated cell death was reduced by the overexpression of HIF-1α but it was rescued by transfection with a HIF-1α mutant (K674R). These data demonstrate that HIF-1α may be stabilized and translocated into the nucleus for the activation of VEGF promoter by TSA-mediated acetylation at K674 under normoxic conditions. These findings suggest that HIF-1α acetylation may lead to resistance to anticancer therapeutics, such as HDAC inhibitors, including TSA.

Nonylphenol increases tumor formation and growth by suppressing gender-independent lymphocyte proliferation and macrophage activation

Nonylphenol (NP) is a well-known endocrine disruptor that influences sexual and reproductive development. Here, we investigated whether NP affects immune responses that are associated with tumor initiation and progression. When spleen cells were incubated with lipopolysaccharide (LPS) and concanavalin A in the presence of 10^-4 M NP, the proliferation of B and T lymphocytes was reduced compared with that in controls, in a gender-independent fashion. While 10^-4 M NP also decreased the production of nitric oxide (NO) in LPS-stimulated bone marrow-derived macrophages (BMDMs), no changes in NO production were detected following treatment with 10^-5 M NP. LPS-stimulated expression of iNOS, COX2, IL-6 and TNF-α in BMDMs was reduced after 6 or 18 hours of incubation with 10^-5 M NP. Furthermore, when mice were pre-exposed to NP for 7 days prior to the injection of B16F10 melanoma cells, the rates of tumor nodule formation and relative tumor growth were higher than those in the control group. In vivo immunosuppressive effect was also clarified by the inhibition of proliferation in B/T lymphocyte and cytokine production in peritoneal macrophages from the mice pretreated with NP for 7 days. Taken together, these data demonstrate that NP could affect the immune responses of lymphocytes and macrophages, leading to the suppression of their tumor-preventing ability. This suggests that individuals at high risk for tumor development should avoid frequent exposure to NP and other endocrine disruptors.

Synovial cell death is regulated by TNF-α-induced expression of B-cell activating factor through an ERK-dependent increase in hypoxia-inducible factor-1α

B-cell activating factor (BAFF) has a role in the maturation and maintenance of B cells and is associated with rheumatoid arthritis (RA). Here, we investigated whether tumor necrosis factor (TNF)-α-induced BAFF expression controls the survival of fibroblast-like synoviocytes (FLS) and whether their survival can be regulated by TNF-α-mediated upregulation of hypoxia-inducible factor (HIF)-1α using MH7A synovial cells transfected with the SV40 T antigen. More TNF-α-treated cells died compared with the control. Survival was increased by incubation with Z-VAD but inhibited after transfection with BAFF-siRNA. Both BAFF and HIF-1α expression were enhanced when MH7A cells were treated with TNF-α. TNF-α-induced BAFF expression decreased in response to HIF-1α-siRNA, whereas it increased under hypoxia or by overexpressing HIF-1α. The HIF-1α binding site on the BAFF promoter (−693 to −688 bp) was confirmed by chromatin immunoprecipitation assay to detect the −750 to −501 bp and −800 to −601 bp regions. The BAFF promoter increased in response to TNF-α treatment or overexpression of HIF-1α. However, TNF-α-induced BAFF expression and promoter activity decreased after treatment with the ERK inhibitor PD98059. Cell death was enhanced by PD98059 but was inhibited by overexpression of HIF-1α. Taken together, our results demonstrate that BAFF expression to control synovial cell survival was regulated by HIF-1α binding to the BAFF promoter, and suggest for the first time that HIF-1α might be involved in the production of inflammatory cytokines to regulate the physiological function of rheumatic FLS.

Ginsenoside Rg3 promotes inflammation resolution through M2 macrophage polarization

Background

Ginsenosides have been reported to have many health benefits, including anti-inflammatory effects, and the resolution of inflammation is now considered to be an active process driven by M2-type macrophages. In order to determine whether ginsenosides modulate macrophage phenotypes to reduce inflammation, 11 ginsenosides were studied with respect to macrophage polarization and the resolution of inflammation.

Methods

Mouse peritoneal macrophages were polarized into M1 or M2 phenotypes. Reverse transcription-polymerase chain reaction, Western blotting, and measurement of nitric oxide (NO) and prostaglandin E₂ levels were performed in vitro and in a zymosan-induced peritonitis C57BL/6 mouse model.

Results

Ginsenoside Rg₃ was identified as a proresolving ginseng compound based on the induction of M2 macrophage polarization. Ginsenoside Rg₃ not only induced the expression of arginase-1 (a representative M2 marker gene), but also suppressed M1 marker genes, such as inducible NO synthase, and NO levels. The proresolving activity of ginsenoside Rg₃ was also observed in vivo in a zymosan-induced peritonitis model. Ginsenoside Rg₃ accelerated the resolution process when administered at peak inflammatory response into the peritoneal cavity.

Conclusion

These results suggest that ginsenoside Rg₃ induces the M2 polarization of macrophages and accelerates the resolution of inflammation. This finding opens a new avenue in ginseng pharmacology.

Polarized macrophages treated with nonylphenol differently regulate lipopolysaccharide-induced sepsis

Nonylphenol (NP) as well-known "endocrine disrupter" influences sexual and reproductive development. Here, we investigated the effect of NP on M1-/M2-type macrophages and their role in lipopolysaccharide (LPS)-induced sepsis. Polarized macrophages of M1- and M2-types were obtained by the treatment with LPS and interleukin-4 (IL-4) to bone marrow-derived macrophages (BMDM), respectively. Coincubation of M1-macrophages with NP decreased COX-2, iNOS, IL-6, and TNF-α expression but no changes were detected in the production of nitric oxide (NO). Survival probability of LPS-induced sepsis mice was enhanced by the injection of NP-treated BMDM as compared to the injection of NP-untreated control BMDM. In the meanwhile, the expression of arginase 1(Arg1), a marker for M2-polarized macrophages was increased by the stimulation with LPS in BMDM. Arg1 expression was also enhanced by the treatment with IL-4 in BMDM, which was reduced by the coincubation with NP. Survival probability of LPS-induced sepsis mice was decreased by the injection of BMDM treated with IL-4 and NP as compared to the injection of IL-4-treated BMDM. It suggests that NP might inhibit macrophage function and the polarization to M2-macrophages. Taken together, data demonstrate that NP could differently affect immune responses of polarized macrophages resulted in the modulation of LPS-induced sepsis. © 2015 Wiley Periodicals, Inc. Environ Toxicol 31: 2081-2089, 2016.

Curcumin hampers the antitumor effect of vinblastine via the inhibition of microtubule dynamics and mitochondrial membrane potential in HeLa cervical cancer cells

BACKGROUND

Curcumin, a major component of curry powder, which is a natural polyphenol product extracted from rhizoma curcumae longae, interacts with a specific binding site on microtubules. Vinblastine is an antitumor drug that induces microtubule depolymerization.

PURPOSE

We investigated whether curcumin influences the antitumor effect of vinblastine in HeLa human cervical cancer cells.

STUDY DESIGN

Changes in microtubule filaments were visualized by immuno-staining. Cell death was determined by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide(MTT) or water-soluble tetrazolium(WST) assay. Apoptotic cell formation was assessed by flow cytometry after staining cells with propidium iodide(PI) and/or Annexin V or with 6-diamidino-2-phenylindole(DAPI). Reactive oxygen species(ROS) were also measured by flow cytometry using dichloro-dihydro-fluorescein diacetate(DCF-DA). JC-1 was used to determine mitochondrial membrane potential (MMP).

RESULTS

When cells were pretreated with curcumin, microtubule filaments were disordered. Vinblastine-induced microtubule depolymerization and cell death were reduced in HeLa human cervical cancer cells pretreated with curcumin compared to the control. The decrease in cell death was much greater in cells pretreated with curcumin compared to cotreatment or post-treatment. DNA condensation by vinblastine was also decreased in curcumin-pretreated cells. Curcumin reduced ROS production by vinblastine. However, no changes in vinblastine-mediated microtubule depolymerization were detected upon N-acetylcysteine(NAC) treatment. In contrast, vinblastine-induced MMP collapse was inhibited by pretreatment with curcumin or NAC. These findings suggest that vinblastine-induced tumor cell death might be inhibited by curcumin via ROS-independent microtubule dynamics and ROS-dependent MMP collapse. It also suggests that microtubule dynamics could be necessary for the optimal antitumor activity of vinblastine. Our results suggest that patients treated with vinblastine should not consume curcumin.