End-binding protein 1 stimulates paclitaxel sensitivity in breast cancer by promoting its actions toward microtubule assembly and stability. Protein Cell. 2014;5:469-479. [PMID: 24748116 PMCID: PMC4026418 DOI: 10.1007/s13238-014-0053-0]

Hexachlorobenzene as a differential modulator of the conventional and metronomic chemotherapy response in triple negative breast cancer cells

Aim

Triple negative breast cancer (TNBC) is usually treated with high doses of paclitaxel, whose effectiveness may be modulated by the action of environmental contaminants such as hexachlorobenzene. High doses of paclitaxel cause adverse effects such as low cellular selectivity and the generation of resistance to treatment due to an increase in the expression of multidrug resistance proteins (MRPs). These effects can be reduced using a metronomic administration scheme with low doses. This study aimed to investigate whether hexachlorobenzene modulates the response of cells to conventional chemotherapy with paclitaxel or metronomic chemotherapy with paclitaxel plus carbachol, as well as to study the participation of the MRP ATP-binding cassette transporter G2 (ABCG2) in human TNBC MDA-MB231 cells.

Methods

Cells were treated with hexachlorobenzene alone or in combination with conventional or metronomic chemotherapies. The effects of treatments on cell viability were determined by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay and the nuclear factor kappa B pathway participation was evaluated using a selective inhibitor. ABCG2 expression and its modulation were determined by western blot.

Results

Results confirmed that paclitaxel reduces MDA-MB231 cell viability in a concentration-dependent manner. Results also showed that both conventional and metronomic chemotherapies reduced cell viability with similar efficacy. Although hexachlorobenzene did not modify cell viability per se, it did reverse the effect induced by the conventional chemotherapy, without affecting the efficacy of the metronomic chemotherapy. Additionally, a differential modulation of ABCG2 expression was determined, mediated by the nuclear factor kappa B pathway, which was directly related to the modulation of cell sensitivity to another cycle of paclitaxel treatment.

Conclusions

The findings indicate that, in human TNBC MDA-MB231 cells, in the presence of hexachlorobenzene, the metronomic combination of paclitaxel plus carbachol is more effective in affecting the tumor biology than the conventional therapeutic administration scheme of paclitaxel.

Tubulin Complexity in Cancer and Metastasis

Tubulin plays a fundamental role in cellular function and as the subject for microtubule-active agents in the treatment of ovarian cancer. Microtubule-binding proteins (e.g., tau, MAP1/2/4, EB1, CLIP, TOG, survivin, stathmin) and posttranslational modifications (e.g., tyrosination, deglutamylation, acetylation, glycation, phosphorylation, polyamination) further diversify tubulin functionality and may permit additional opportunities to understand microtubule behavior in disease and to develop microtubule-modifying approaches to combat ovarian cancer. Tubulin-based structures that project from suspended ovarian cancer cells known as microtentacles may contribute to metastatic potential of ovarian cancer cells and could represent an exciting novel therapeutic target.

DIAPH1 facilitates paclitaxel-mediated cytotoxicity of ovarian cancer cells

The chemotherapeutic agent paclitaxel (PTX) selectively binds to and stabilizes microtubule (MTs). Also, the activated formin Diaphanous Related Formin 1 (DIAPH1) binds to MTs and increases its stability. In a recent study, we found that high DIAPH1 levels correlated with increased survival of ovarian cancer (Ovca) patients. A possible explanation for this finding is that Ovca cells with high DIAPH1 levels are more sensitive to PTX. To examine this assumption, in this study the effect of DIAPH1 depletion on PTX-mediated cytotoxicity of OVCAR8 and OAW42 cells was analyzed. Our data showed that down-regulation of DIAPH1 expression decreased PTX sensitivity in both cell lines by reducing apoptosis or necrosis. Analysis of MT stability by Western blotting revealed a decreased concentration of stable, detyrosinated MTs in PTX-treated DIAPH1 knock-down compared to control cells. Also, in fixed metaphase cells the level of stable, detyrosinated spindle MTs decreased in cells with reduced DIAPH1 expression. In vitro analysis with recombinant DIAPH1 protein showed that PTX and DIAPH1 exhibited additive effects on MT-polymerization, showing that also in a cell-free system DIAPH1 increased the effect of PTX on MT-stability. Together, our data strongly indicate that DIAPH1 increases the response of Ovca cells to PTX by enhancing PTX-mediated MT-stability.

Microtubule-Interfering Drugs: Current and Future Roles in Epithelial Ovarian Cancer Treatment

Taxanes and epothilones are chemotherapeutic agents that ultimately lead to cell death through inhibition of normal microtubular function. This review summarizes the literature demonstrating their current use and potential promise as therapeutic agents in the treatment of epithelial ovarian cancer (EOC), as well as putative mechanisms of resistance. Historically, taxanes have become the standard of care in the front-line and recurrent treatment of epithelial ovarian cancer. In the past few years, epothilones (i.e., ixabepilone) have become of interest as they may retain activity in taxane-treated patients since they harbor several features that may overcome mechanisms of taxane resistance. Clinical data now support the use of ixabepilone in the treatment of platinum-resistant or refractory ovarian cancer. Clinical data strongly support the use of microtubule-interfering drugs alone or in combination in the treatment of epithelial ovarian cancer. Ongoing clinical trials will shed further light into the potential of making these drugs part of current standard practice.

Breast cancer: Muscarinic receptors as new targets for tumor therapy

The development of breast cancer is a complex process that involves the participation of different factors. Several authors have demonstrated the overexpression of muscarinic acetylcholine receptors (mAChRs) in different tumor tissues and their role in the modulation of tumor biology, positioning them as therapeutic targets in cancer. The conventional treatment for breast cancer involves surgery, radiotherapy, and/or chemotherapy. The latter presents disadvantages such as limited specificity, the appearance of resistance to treatment and other side effects. To prevent these side effects, several schedules of drug administration, like metronomic therapy, have been developed. Metronomic therapy is a type of chemotherapy in which one or more drugs are administered at low concentrations repetitively. Recently, two chemotherapeutic agents usually used to treat breast cancer have been considered able to activate mAChRs. The combination of low concentrations of these chemotherapeutic agents with muscarinic agonists could be a useful option to be applied in breast cancer treatment, since this combination not only reduces tumor cell survival without affecting normal cells, but also decreases pathological neo-angiogenesis, the expression of drug extrusion proteins and the cancer stem cell fraction. In this review, we focus on the previous evidences that have positioned mAChRs as relevant therapeutic targets in breast cancer and analyze the effects of administering muscarinic agonists in combination with conventional chemotherapeutic agents in a metronomic schedule.

A look into the link between centrosome amplification and breast cancer

Centrosome amplification (CA) is a common feature of human tumors, but it is not clear whether this is a cause or a consequence of cancer. The centrosome amplification observed in tumor cells may be explained by a series of events, such as failure of cell division, dysregulation of centrosome cycle checkpoints, and de novo centriole biogenesis disorder. The formation and progression of breast cancer are characterized by genomic abnormality. The centrosomes in breast cancer cells show characteristic structural aberrations, caused by centrosome amplification, which include: an increase in the number and volume of centrosomes, excessive increase of pericentriolar material (PCM), inappropriate phosphorylation of centrosomal molecular, and centrosome clustering formation induced by the dysregulation of important genes. The mechanism of intracellular centrosome amplification, the impact of which on breast cancer and the latest breast cancer target treatment options for centrosome amplification are exhaustively elaborated in this review.

AKAP350 enables p150glued /EB1 interaction at the spindle poles

A-kinase anchoring protein 350 (AKAP350) is a centrosomal/Golgi scaffold protein, critical for the regulation of microtubule dynamics. AKAP350 recruits end-binding protein 1 (EB1) to the centrosome in mitotic cells, ensuring proper spindle orientation in epithelial cells. AKAP350 also interacts with p150^glued, the main component of the dynactin complex. In the present work, we found that AKAP350 localized p150^glued to the spindle poles, facilitating p150^glued/EB1 interaction at these structures. Our results further showed that the decrease in AKAP350 expression reduced p150^glued localization at astral microtubules and impaired the elongation of astral microtubules during anaphase. Overall, this study provides mechanistic data on how microtubule regulatory proteins gather to define microtubule dynamics in mitotic cells.

Intrinsic and Extrinsic Factors Affecting Microtubule Dynamics in Normal and Cancer Cells

Microtubules (MTs), highly dynamic structures composed of α- and β-tubulin heterodimers, are involved in cell movement and intracellular traffic and are essential for cell division. Within the cell, MTs are not uniform as they can be composed of different tubulin isotypes that are post-translationally modified and interact with different microtubule-associated proteins (MAPs). These diverse intrinsic factors influence the dynamics of MTs. Extrinsic factors such as microtubule-targeting agents (MTAs) can also affect MT dynamics. MTAs can be divided into two main categories: microtubule-stabilizing agents (MSAs) and microtubule-destabilizing agents (MDAs). Thus, the MT skeleton is an important target for anticancer therapy. This review discusses factors that determine the microtubule dynamics in normal and cancer cells and describes microtubule-MTA interactions, highlighting the importance of tubulin isoform diversity and post-translational modifications in MTA responses and the consequences of such a phenomenon, including drug resistance development.

MAPRE1 promotes cell cycle progression of hepatocellular carcinoma cells by interacting with CDK2

Targeting cyclin-dependent kinases (CDKs) is a promising method of therapy for cancer. Unfortunately, the efficacy of CDK inhibitors in hepatocellular carcinoma (HCC) is limited, due in part to incomplete understanding of cell cycle progression and a lack of specific biomarkers to adequately identify which patients may be responsive to CDK inhibitors. In the present study, we report that microtubule-associated protein RP/EB family member 1 (MAPRE1), a gene involved in cell cycle and microtubule regulation, is significantly increased in HCC tissue, promotes HCC cell proliferation, enhances in vitro tumorigenesis, and associates with poor prognosis of HCC. We demonstrate that MAPRE1 binds with CDK2, resulting in the hyperphosphorylation of the CDK2 Thr161 residue in HCC cells. Our findings reveal that targeting MAPRE1 might be an effective therapeutic strategy in HCC, and suggest that MAPRE1 expression might provide a promising biomarker to stratify patients with HCC who may benefit from treatment with CDK inhibitors.

Environmental pollutants damage airway epithelial cell cilia: Implications for the prevention of obstructive lung diseases

Mucociliary epithelium lining the upper and lower respiratory tract constitutes the first line of defense of the airway and lungs against inhaled pollutants and pathogens. The concerted beating of multiciliated cells drives mucociliary clearance. Abnormalities in both the structure and function of airway cilia have been implicated in obstructive lung diseases. Emerging evidence reveals a close correlation between lung diseases and environmental stimuli such as sulfur dioxide and tobacco particles. However, the underlying mechanism remains to be described. In this review, we emphasize the importance of airway cilia in mucociliary clearance and discuss how environmental pollutants affect the structure and function of airway cilia, thus shedding light on the function of airway cilia in preventing obstructive lung diseases and revealing the negative effects of environmental pollutants on human health.

Alteration of cell junctions during viral infection

Cell junctions serve as a protective barrier for cells and provide an important channel for information transmission between cells and the surrounding environment. Viruses are parasites that invade and commandeer components of host cells in order to survive and replicate, and they have evolved various mechanisms to alter cell junctions to facilitate viral infection. In this review, we examined the current state of knowledge on the action of viruses on host cell junctions. The existing evidence suggests that targeting the molecules involved in the virus-cell junction interaction can prevent the spread of viral diseases.

Environmental pollutants damage airway epithelial cell cilia: Implications for the prevention of obstructive lung diseases

Mucociliary epithelium lining the upper and lower respiratory tract constitutes the first line of defense of the airway and lungs against inhaled pollutants and pathogens. The concerted beating of multiciliated cells drives mucociliary clearance. Abnormalities in both the structure and function of airway cilia have been implicated in obstructive lung diseases. Emerging evidence reveals a close correlation between lung diseases and environmental stimuli such as sulfur dioxide and tobacco particles. However, the underlying mechanism remains to be described. In this review, we emphasize the importance of airway cilia in mucociliary clearance and discuss how environmental pollutants affect the structure and function of airway cilia, thus shedding light on the function of airway cilia in preventing obstructive lung diseases and revealing the negative effects of environmental pollutants on human health.

Ai-lncRNA EGOT enhancing autophagy sensitizes paclitaxel cytotoxicity via upregulation of ITPR1 expression by RNA-RNA and RNA-protein interactions in human cancer

BACKGROUND

The biology function of antisense intronic long noncoding RNA (Ai-lncRNA) is still unknown. Meanwhile, cancer patients with paclitaxel resistance have limited therapeutic options in the clinic. However, the potential involvement of Ai-lncRNA in paclitaxel sensitivity remains unclear in human cancer.

METHODS

Whole transcriptome sequencing of 33 breast specimens was performed to identify Ai-lncRNA EGOT. Next, the role of EGOT in regulation of paclitaxel sensitivity was investigated. Moreover, the mechanism of EGOT enhancing autophagy sensitizes paclitaxel cytotoxicity via upregulation of ITPR1 expression by RNA-RNA and RNA-protein interactions was investigated in detail. Furthermore, upstream transcriptional regulation of EGOT expression was also investigated by co-immunoprecipitation and chromatin immunoprecipitation. Finally, clinical breast specimens in our cohort, TCGA and ICGC were applied to validate the role of EGOT in enhancing of paclitaxel sensitivity.

RESULTS

EGOT enhances autophagosome accumulation via the up-regulation of ITPR1 expression, thereby sensitizing cells to paclitaxel toxicity. Mechanistically, on one hand, EGOT upregulates ITPR1 levels via formation of a pre-ITPR1/EGOT dsRNA that induces pre-ITPR1 accumulation to increase ITPR1 protein expression in cis. On the other hand, EGOT recruits hnRNPH1 to enhance the alternative splicing of pre-ITPR1 in trans via two binding motifs in EGOT segment 2 (324-645 nucleotides) in exon 1. Moreover, EGOT is transcriptionally regulated by stress conditions. Finally, EGOT expression enhances paclitaxel sensitivity via assessment of cancer specimens.

CONCLUSIONS

These findings broaden comprehensive understanding of the biology function of Ai-lncRNAs. Proper regulation of EGOT may be a novel synergistic strategy for enhancing paclitaxel sensitivity in cancer therapy.

Phosphorylation of EB1 regulates the recruitment of CLIP-170 and p150glued to the plus ends of astral microtubules

Phosphorylation of end-binding protein 1 (EB1), a key member of microtubule plus end-tracking proteins (+TIPs), by apoptosis signal-regulating kinase 1 (ASK1) has been demonstrated to promote the stability of astral microtubules during mitosis by stimulating the binding of EB1 to microtubule plus ends. However, the roles of other members of the +TIPs family in ASK1/EB1-mediated regulation of astral microtubules are unknown. Herein, we show that ASK1-mediated phosphorylation of EB1 enhances the localization of cytoplasmic linker protein 170 (CLIP-170) and p150^glued to the plus ends of astral microtubules. Depletion of ASK1 or expression of phospho-deficient or phospho-mimetic EB1 mutants results in changes in the levels of plus-end localized CLIP-170 or p150^glued. Mechanistic studies reveal that EB1 phosphorylation promotes its interactions with CLIP-170 and p150^glued, thereby recruiting these +TIPs to microtubules. Structural analysis suggests that serine-40 is the primary phosphorylation site on EB1 that exerts these effects. Together, these findings provide novel insight into the molecular mechanisms that regulate the interactions of EB1 with other +TIPs.

EB1 phosphorylation mediates the functions of ASK1 in pancreatic cancer development

Pancreatic cancer has a poor prognosis due to its rapid rate of metastasis and frequent late-stage diagnosis. An improved understanding of the molecular mechanisms underlying this disease is urgently needed to promote the development of improved diagnostic tools and more effective therapies. Apoptosis signal-regulating kinase 1 (ASK1) has been shown to be overexpressed in pancreatic cancer and to promote the proliferation of pancreatic cancer cells in a kinase activity-dependent manner. However, the molecular mechanisms by which ASK1 promotes cell proliferation remain to be elucidated. In this study, we report that the phosphorylation of end-binding protein 1 (EB1) at threonine 206 (pT206-EB1), which is catalyzed by ASK1, is increased in pancreatic cancer tissues. We further find that the level of pT206-EB1 correlates with that of ASK1 in cancer tissues. Additionally, ASK1 localizes to spindle poles, and knockdown of ASK1 results in the formation of multipolar spindles. Moreover, we show that depletion of ASK1 or disruption of EB1 phosphorylation inhibits spindle microtubule dynamics in pancreatic cancer cells. Collectively, these findings suggest that EB1 phosphorylation mediates the functions of ASK1 in pancreatic cancer development.

Regulation of paclitaxel activity by microtubule-associated proteins in cancer chemotherapy

Microtubules, highly dynamic components of the cytoskeleton, participate in diverse cellular activities such as mitosis, cell migration, and intracellular trafficking. Dysregulation of microtubule dynamics contributes to the development of serious diseases, including cancer. The dynamic properties and functions of microtubule network are regulated by microtubule-associated proteins. Paclitaxel, an anti-microtubule agent of the taxane family, has shown a success in clinical treatment of many cancer patients. However, the variable response activity of patients and acquired resistance to paclitaxel limit the clinical use of the drug. Accumulating studies show that microtubule-associated proteins can regulate paclitaxel sensitivity in a wide range of cancer types. In this review, we will describe the roles of various microtubule-associated proteins in the regulation of paclitaxel in cancers. Particularly, we will focus on the modulation of centrosomal proteins in paclitaxel resistance. Improved understandings of how these proteins act might predict treatment responses and provide insights into more rational chemotherapeutic regimens in clinical practice.

Regulation of end-binding protein EB1 in the control of microtubule dynamics

The regulation of microtubule dynamics is critical to ensure essential cell functions, such as proper segregation of chromosomes during mitosis or cell polarity and migration. End-binding protein 1 (EB1) is a plus-end-tracking protein (+TIP) that accumulates at growing microtubule ends and plays a pivotal role in the regulation of microtubule dynamics. EB1 autonomously binds an extended tubulin-GTP/GDP-Pi structure at growing microtubule ends and acts as a molecular scaffold that recruits a large number of regulatory +TIPs through interaction with CAP-Gly or SxIP motifs. While extensive studies have focused on the structure of EB1-interacting site at microtubule ends and its role as a molecular platform, the mechanisms involved in the negative regulation of EB1 have only started to emerge and remain poorly understood. In this review, we summarize recent studies showing that EB1 association with MT ends is regulated by post-translational modifications and affected by microtubule-targeting agents. We also present recent findings that structural MAPs, that have no tip-tracking activity, physically interact with EB1 to prevent its accumulation at microtubule plus ends. These observations point out a novel concept of "endogenous EB1 antagonists" and emphasize the importance of finely regulating EB1 function at growing microtubule ends.

The Phytoestrogen Genistein Affects Breast Cancer Cells Treatment Depending on the ERα/ERβ Ratio

Genistein (GEN) is a phytoestrogen found in soybeans. GEN exerts its functions through its interaction with the estrogen receptors (ER), ERα and ERβ, and we previously reported that the ERα/ERβ ratio is an important factor to consider in GEN-treated breast cancer cells. The aim of this study was to investigate the effects of GEN in breast cancer cells with different ERα/ERβ ratio: MCF-7 (high ratio), T47D (low ratio), and MCF-7 overexpressing ERβ (MCF7 + ERβ) treated with cisplatin (CDDP), paclitaxel (PTX) or tamoxifen (TAM). Cell viability, ROS production, autophagy, apoptosis, antioxidant enzymes protein levels, and cell cycle were analyzed. GEN treatment provoked an increase in cell viability in MCF-7 cells and in the antioxidant enzymes protein levels in combination with the cytotoxic agents, decreasing ROS production (CDDP + GEN and TAM+GEN) and autophagy (TAM + GEN) or apoptosis (CDDP + GEN and TAM + GEN). Moreover GEN treatment enhanced the cell cycle S phase entry in CDDP+GEN- and TAM + GEN-treated MCF-7 cells and, in the case of CDDP + GEN, increased the proportion of cells in the G2/M phase and decreased it in the subG0 /G1 phase. Otherwise, in the T47D and MCF7 + ERβ cells the combination of GEN with cytotoxic treatments did not cause significant changes in these parameters, even TAM + GEN-treated T47D cells showed less cell viability due to an increment in the autophagy. In conclusion, GEN consumption may be counterproductive in those patients receiving anticancer treatment with a high ERα/ERβ ratio diagnosed breast cancer and it could be harmless or even beneficial in those patients with a lower ERα/ERβ ratio breast cancer cells.

Nanomedicine as an emerging platform for metastatic lung cancer therapy

Metastatic lung cancer is one of the most common cancers leading to mortality worldwide. Current treatment includes chemo- and pathway-dependent therapy aiming at blocking the spread and proliferation of these metastatic lesions. Nanomedicine is an emerging multidisciplinary field that offers unprecedented access to living cells and promises the state of the art in cancer detection and treatment. Development of nanomedicines as drug carriers (nanocarriers) that target cancer for therapy draws upon principles in the fields of chemistry, medicine, physics, biology, and engineering. Given the zealous activity in the field as demonstrated by more than 30 nanocarriers already approved for clinical use and given the promise of recent clinical results in various studies, nanocarrier-based strategies are anticipated to soon have a profound impact on cancer medicine and human health. Herein, we will detail the latest innovations in therapeutic nanomedicine with examples from lipid-based nanoparticles and polymer-based approaches, which are engineered to deliver anticancer drugs to metastatic lung cells. Emphasis will be placed on the latest and most attractive delivery platforms, which are developed specifically to target lung metastatic tumors. These novel nanomedicines may open new avenues for therapeutic intervention carrying new class of drugs such as RNAi and mRNA and the ability to edit the genome using the CRISPER/Cas9 system. Ultimately, these strategies might become a new therapeutic modality for advanced-stage lung cancer.

CYLD - a deubiquitylase that acts to fine-tune microtubule properties and functions

Microtubules are dynamic structures that are crucially involved in a variety of cellular activities. The dynamic properties and functions of microtubules are regulated by various factors, such as tubulin isotype composition and microtubule-binding proteins. Initially identified as a deubiquitylase with tumor-suppressing functions, the protein cylindromatosis (CYLD) has recently been revealed to interact with microtubules, modulate microtubule dynamics, and participate in the regulation of cell migration, cell cycle progression, chemotherapeutic drug sensitivity and ciliogenesis. These findings have greatly enriched our understanding of the roles of CYLD in physiological and pathological conditions. Here, we focus on recent literature that shows how CYLD impacts on microtubule properties and functions in various biological processes, and discuss the challenges we face when interpreting results obtained from different experimental systems.

Microtubule-Binding Proteins as Promising Biomarkers of Paclitaxel Sensitivity in Cancer Chemotherapy

Microtubules, tirelessly animated and highly dynamic structures, are vital for most cellular processes and their intricacies are still being revealed even after a century since their discovery. The importance of microtubules as chemotherapeutic targets cannot be overstated, and their clinical role is unlikely to abate in the near future. Indeed, improved understanding of microtubule biology could herald a new epoch of anticancer drug design by permitting fine-tuning of microtubule-targeting agents, the clinical utility of which is presently often limited by primary or acquired resistance. Paclitaxel, one such agent belonging to the taxane family, has proven a resoundingly successful treatment for many cancer patients; however, for too many others with paclitaxel-refractory tumors, the drug has offered nothing but side effects. Accumulating evidence suggests that microtubule-binding proteins (MBPs) can regulate paclitaxel sensitivity in a wide range of cancer types. Improved understanding of how these proteins can be assayed to predict treatment responses or manipulated pharmacologically to improve clinical outcomes could transform modern chemotherapy and is urgently awaited.

The presence of Estrogen Receptor β modulates the response of breast cancer cells to therapeutic agents

Breast cancer is a leading cause of death for women. The estrogen receptors (ERs) ratio is important in the maintenance of mitochondrial redox status, and higher levels of ERβ increases mitochondrial functionality, decreasing ROS production. Our aim was to determine the interaction between the ERα/ERβ ratio and the response to cytotoxic treatments such as cisplatin (CDDP), paclitaxel (PTX) and tamoxifen (TAM). Cell viability, apoptosis, autophagy, ROS production, mitochondrial membrane potential, mitochondrial mass and mitochondrial functionality were analyzed in MCF-7 (high ERα/ERβ ratio) and T47D (low ERα/ERβ ratio) breast cancer cell lines. Cell viability decreased more in MCF-7 when treated with CDDP and PTX. Apoptosis was less activated after cytotoxic treatments in T47D than in MCF-7 cells. Nevertheless, autophagy was increased more in CDDP-treated MCF-7, but less in TAM-treated cells than in T47D. CDDP treatment produced a raise in mitochondrial mass in MCF-7, as well as the citochrome c oxidase (COX) and ATP synthase protein levels, however significantly reduced COX activity. In CDDP-treated cells, the overexpression of ERβ in MCF-7 caused a reduction in apoptosis, autophagy and ROS production, leading to higher cell survival; and the silencing of ERβ in T47D cells promoted the opposite effects. In TAM-treated cells, ERβ-overexpression led to less cell viability by an increment in autophagy; and the partial knockdown of ERβ in T47D triggered an increase in ROS production and apoptosis, leading to cell death. In conclusion, ERβ expression plays an important role in the response of cancer cells to cytotoxic agents, especially for cisplatin treatment.

Identification of novel microtubule-binding proteins by taxol-mediated microtubule stabilization and mass spectrometry analysis

Microtubule-binding proteins (MBPs) are structurally and functionally diverse regulators of microtubule-mediated cellular processes. Alteration of MBPs has been implicated in the pathogenesis of human diseases, including cancer. MBPs can stabilize or destabilize microtubules or move along microtubules to transport various cargoes. In addition, MBPs can control microtubule dynamics through direct interaction with microtubules or coordination with other proteins. To better understand microtubule structure and function, it is necessary to identify additional MBPs. In this study, we isolated microtubules and MBPs from mammalian cells by a taxol-based method and then profiled a panel of MBPs by mass spectrometry. We discovered a number of previously uncharacterized MBPs, including several membrane-associated proteins and proteins involved in post-translational modifications, in addition to several structural components. These results support the notion that microtubules have a wide range of functions and may undergo more exquisite regulation than previously recognized.

CYLD Regulates Noscapine Activity in Acute Lymphoblastic Leukemia via a Microtubule-Dependent Mechanism

Noscapine is an orally administrable drug used worldwide for cough suppression and has recently been demonstrated to disrupt microtubule dynamics and possess anticancer activity. However, the molecular mechanisms regulating noscapine activity remain poorly defined. Here we demonstrate that cylindromatosis (CYLD), a microtubule-associated tumor suppressor protein, modulates the activity of noscapine both in cell lines and in primary cells of acute lymphoblastic leukemia (ALL). Flow cytometry and immunofluorescence microscopy reveal that CYLD increases the ability of noscapine to induce mitotic arrest and apoptosis. Examination of cellular microtubules as well as in vitro assembled microtubules shows that CYLD enhances the effect of noscapine on microtubule polymerization. Microtubule cosedimentation and fluorescence titration assays further reveal that CYLD interacts with microtubule outer surface and promotes noscapine binding to microtubules. These findings thus demonstrate CYLD as a critical regulator of noscapine activity and have important implications for ALL treatment.

+TIP EB1 downregulates paclitaxel‑induced proliferation inhibition and apoptosis in breast cancer cells through inhibition of paclitaxel binding on microtubules

Microtubule plus‑end‑binding protein (+TIP) EB1 has been shown to be upregulated in breast cancer cells and promote breast tumor growth in vivo. However, its effect on the cellular actions of microtubule‑targeted drugs in breast cancer cells has remained poorly understood. By using cellular and biochemical assays, we demonstrate that EB1 plays a critical role in regulating the sensitivity of breast cancer cells to anti‑microtubule drug, paclitaxel (PTX). Cell viability assays revealed that EB1 expression in the breast cancer cell lines correlated with the reduction of their sensitivity to PTX. Knockdown of EB1 by enzymatically‑prepared siRNA pools (esiRNAs) increased PTX‑induced cytotoxicity and sensitized cells to PTX‑induced apoptosis in three breast cancer cell lines, MCF‑7, MDA MB‑231 and T47D. Apoptosis was associated with activation of caspase‑9 and an increase in the cleavage of poly(ADP‑ribose) polymerase (PARP). p53 and Bax were upregulated and Bcl2 was downregulated in the EB1‑depleted PTX‑treated MCF‑7 cells, indicating that the apoptosis occurs via a p53‑dependent pathway. Following its upregulation, the nuclear accumulation of p53 and its association with cellular microtubules were increased. EB1 depletion increased PTX‑induced microtubule bundling in the interphase cells and induced formation of multiple spindle foci with abnormally elongated spindles in the mitotic MCF‑7 cells, indicating that loss of EB1 promotes PTX‑induced stabilization of microtubules. EB1 inhibited PTX‑induced microtubule polymerization and diminished PTX binding to microtubules in vitro, suggesting that it modulates the binding sites of PTX at the growing microtubule ends. Results demonstrate that EB1 downregulates inhibition of PTX‑induced proliferation and apoptosis in breast cancer cells through a mechanism in which it impairs PTX‑mediated stabilization of microtubule polymerization and inhibits PTX binding on microtubules.

Microtubule-associated protein Mdp3 promotes breast cancer growth and metastasis

Breast cancer is the most prevalent cancer in women worldwide with a high mortality rate, and the identification of new biomarkers and targets for this disease is greatly needed. Here we present evidence that microtubule-associated protein (MAP) 7 domain-containing protein 3 (Mdp3) is highly expressed in clinical samples and cell lines of breast cancer. The expression of Mdp3 correlates with clinicopathological parameters indicating breast cancer malignancy. In addition, Mdp3 promotes breast cancer cell proliferation and motility in vitro and stimulates breast cancer growth and metastasis in mice. Mechanistic studies reveal that γ-tubulin interacts with and recruits Mdp3 to the centrosome and that the centrosomal localization of Mdp3 is required for its activity to promote breast cancer cell proliferation and motility. These findings suggest a critical role for Mdp3 in the growth and metastasis of breast cancer and may have important implications for the management of this disease.