Nuclear βII-Tubulin Associates with the Activated Notch Receptor to Modulate Notch Signaling

Flavone-based dual PARP-Tubulin inhibitor manifesting efficacy against endometrial cancer

Structural tailoring of the flavone framework (position 7) via organopalladium-catalyzed C-C bond formation was attempted in this study. The impact of substituents with varied electronic effects (phenyl ring, position 2 of the benzopyran scaffold) on the antitumor properties was also assessed. Resultantly, the efforts yielded a furyl arm bearing benzopyran possessing a 4-fluoro phenyl ring (position 2) (14) that manifested a magnificent antitumor profile against the Ishikawa cell lines mediated through dual inhibition of PARP and tubulin [(IC50 (PARP1) = 74 nM, IC50 (PARP2) = 109 nM) and tubulin (IC50 = 1.4 µM)]. Further investigations confirmed the ability of 14 to induce apoptosis as well as autophagy and cause cell cycle arrest at the G2/M phase. Overall, the outcome of the study culminated in a tractable dual PARP-tubulin inhibitor endowed with an impressive activity profile against endometrial cancer.

Tubulin Isotypes: Emerging Roles in Defining Cancer Stem Cell Niche

Although the role of microtubule dynamics in cancer progression is well-established, the roles of tubulin isotypes, their cargos and their specific function in the induction and sustenance of cancer stem cells (CSCs) were poorly explored. But emerging reports urge to focus on the transport function of tubulin isotypes in defining orchestrated expression of functionally critical molecules in establishing a stem cell niche, which is the key for CSC regulation. In this review, we summarize the role of specific tubulin isotypes in the transport of functional molecules that regulate metabolic reprogramming, which leads to the induction of CSCs and immune evasion. Recently, the surface expression of GLUT1 and GRP78 as well as voltage-dependent anion channel (VDAC) permeability, regulated by specific isotypes of β-tubulins have been shown to impart CSC properties to cancer cells, by implementing a metabolic reprogramming. Moreover, βIVb tubulin is shown to be critical in modulating EphrinB1signaling to sustain CSCs in oral carcinoma. These tubulin-interacting molecules, Ephrins, GLUT1 and GRP78, are also important regulators of immune evasion, by evoking PD-L1 mediated T-cell suppression. Thus, the recent advances in the field implicate that tubulins play a role in the controlled transport of molecules involved in CSC niche. The indication of tubulin isotypes in the regulation of CSCs offers a strategy to specifically target those tubulin isotypes to eliminate CSCs, rather than the general inhibition of microtubules, which usually leads to therapy resistance.

Targeting Notch to Maximize Chemotherapeutic Benefits: Rationale, Advanced Strategies, and Future Perspectives

Simple Summary

The Notch signaling pathway regulates cell proliferation, apoptosis, stem cell self-renewal, and differentiation in a context-dependent fashion both during embryonic development and in adult tissue homeostasis. Consistent with its pleiotropic physiological role, unproper activation of the signaling promotes or counteracts tumor pathogenesis and therapy response in distinct tissues. In the last twenty years, a wide number of studies have highlighted the anti-cancer potential of Notch-modulating agents as single treatment and in combination with the existent therapies. However, most of these strategies have failed in the clinical exploration due to dose-limiting toxicity and low efficacy, encouraging the development of novel agents and the design of more appropriate combinations between Notch signaling inhibitors and chemotherapeutic drugs with improved safety and effectiveness for distinct types of cancer.

Abstract

Notch signaling guides cell fate decisions by affecting proliferation, apoptosis, stem cell self-renewal, and differentiation depending on cell and tissue context. Given its multifaceted function during tissue development, both overactivation and loss of Notch signaling have been linked to tumorigenesis in ways that are either oncogenic or oncosuppressive, but always context-dependent. Notch signaling is critical for several mechanisms of chemoresistance including cancer stem cell maintenance, epithelial-mesenchymal transition, tumor-stroma interaction, and malignant neovascularization that makes its targeting an appealing strategy against tumor growth and recurrence. During the last decades, numerous Notch-interfering agents have been developed, and the abundant preclinical evidence has been transformed in orphan drug approval for few rare diseases. However, the majority of Notch-dependent malignancies remain untargeted, even if the application of Notch inhibitors alone or in combination with common chemotherapeutic drugs is being evaluated in clinical trials. The modest clinical success of current Notch-targeting strategies is mostly due to their limited efficacy and severe on-target toxicity in Notch-controlled healthy tissues. Here, we review the available preclinical and clinical evidence on combinatorial treatment between different Notch signaling inhibitors and existent chemotherapeutic drugs, providing a comprehensive picture of molecular mechanisms explaining the potential or lacking success of these combinations.

Tubulin Beta 2C Chain (TBB2C), a Potential Marker of Ovarian Cancer, an Insight from Ovarian Cancer Proteome Profile

Ovarian cancer (OC) is the most lethal among female reproductive system malignancies. Depending upon the stage at presentation, the five year survival ratio varies from ∼92 to ∼30%. The role of biomarkers in early cancer diagnosis, including OC, is well understood. In our previous study, through an initial screening, we have analyzed eleven proteins that exhibited differential expression in OC using two-dimensional gel electrophoresis (2D-GE) and matrix-assisted laser desorption/ionization-time of flight mass spectrometric (MALDI-TOF MS) analysis. In continuation of our previous study, the present work describes analysis of twenty more proteins that showed aberrant expression in OC. Among these, six showed consistent significant deregulation in the OC false discovery rate [FDR ≤ 0.05]. Upon MS analysis, they were identified as vimentin, tubulin beta 2C chain, tubulin alpha 1C chain, actin cytoplasmic 2, apolipoprotein A-I, and collagen alpha 2(VI) chain [peptide mass fingerprint (PMF) score ≥ 79]. One of the differentially regulated proteins, tubulin beta 2C chain, was found to be significantly (fold change, 2.5) enhanced in OC. Verification by western blot and enzyme-linked immunosorbent assay (ELISA) demonstrated that the tubulin beta 2C chain may serve as a valuable marker for OC (ANOVA p < 0.0001). The assessment of the likely association of TBB2C with OC in a larger population will not only help in developing clinically useful biomarkers in the future but also improve our understanding of the progression of OC disease.

Keratin 17 regulates nuclear morphology and chromatin organization

Keratin 17 (KRT17; K17), a non-lamin intermediate filament protein, was recently found to occur in the nucleus. We report here on K17-dependent differences in nuclear morphology, chromatin organization, and cell proliferation. Human tumor keratinocyte cell lines lacking K17 exhibit flatter nuclei relative to normal. Re-expression of wild-type K17, but not a mutant form lacking an intact nuclear localization signal (NLS), rescues nuclear morphology in KRT17-null cells. Analyses of primary cultures of skin keratinocytes from a mouse strain expressing K17 with a mutated NLS corroborated these findings. Proteomics screens identified K17-interacting nuclear proteins with known roles in gene expression, chromatin organization and RNA processing. Key histone modifications and LAP2β (an isoform encoded by TMPO) localization within the nucleus are altered in the absence of K17, correlating with decreased cell proliferation and suppression of GLI1 target genes. Nuclear K17 thus impacts nuclear morphology with an associated impact on chromatin organization, gene expression, and proliferation in epithelial cells.This article has an associated First Person interview with the first author of the paper.

Tubulin is actively exported from the nucleus through the Exportin1/CRM1 pathway

Microtubules of all eukaryotic cells are formed by α- and β-tubulin heterodimers. In addition to the well known cytoplasmic tubulins, a subpopulation of tubulin can occur in the nucleus. So far, the potential function of nuclear tubulin has remained elusive. In this work, we show that α- and β-tubulins of various organisms contain multiple conserved nuclear export sequences, which are potential targets of the Exportin 1/CRM1 pathway. We demonstrate exemplarily that these NES motifs are sufficient to mediate export of GFP as model cargo and that this export can be inhibited by leptomycin B, an inhibitor of the Exportin 1/CRM1 pathway. Likewise, leptomycin B causes accumulation of GFP-tagged tubulin in interphase nuclei, in both plant and animal model cells. Our analysis of nuclear tubulin content supports the hypothesis that an important function of nuclear tubulin export is the exclusion of tubulin from interphase nuclei, after being trapped by nuclear envelope reassembly during telophase.

Nuclear localization of PD-L1: artifact or reality?

BACKGROUND

The levels of expression and membrane localization of programmed cell death ligand 1 (PD-L1), an immune checkpoint type I transmembrane glycoprotein, are related to the clinical response of anti-PD-L1/PD-1 therapy. Although the biologically relevant localization of PD-L1 is on the plasma membrane of cancer cells, it has also been reported to be in the cytoplasm and sometimes in the nucleus. Furthermore, it has been claimed that chemotherapeutics can modify PD-L1 expression and/or its nuclear localization.

RESULTS

Data from our group suggest that the nuclear localization of PD-L1, and other plasma membrane proteins as well, could be an artifact resulting from inadequate experimental conditions during immunocytochemical studies. Mild detergent and rigorous fixation conditions should be used in order to preserve the membrane localization and to prevent an erroneous translocation of PD-L1 and other non-interconnected membrane proteins, such as CD24, into other cellular compartments including the nucleus, of untreated and chemotherapeutically treated breast cancer cells.

CONCLUSION

We propose that well-specified and rigorously followed protocols should be applied to immunocytochemical diagnostic techniques, especially to those related to individualized diagnosis and treatment.

Phosphorylation, Dephosphorylation, and Multiprotein Assemblies Regulate Dynamic Behavior of Neuronal Cytoskeleton: A Mini-Review

Cellular localization, assembly and abnormal aggregation of neurofilaments depend on phosphorylation. Pathological processes associated with neurodegeneration exhibit aberrant accumulation of microtubule associated aggregated forms of hyperphosphorylated neuronal protein tau in cell bodies. These processes are critical for the disease progression in patients suffering from Alzheimer's disease, Parkinson's disease, and Amyotrophic Lateral Sclerosis. In healthy cells, tau is localized in axons. Topographic regulation suggests that whereas the sites of synthesis of kinases and neurofilaments are the cell bodies, and sites of their functional assemblies are axons, phosphorylation/dephosphorylation are the key processes that arrange the molecules at their precise locations. Phosphorylation sites in the dynamic developmental and degenerative processes differ. Not all these processes are well understood. New advancements identify epigenetic factors involved in AD which account for the influence of age-related environment/genome interactions leading to the disease. Progress in proteomics highlights previously found major proteins and adds more to the list of those involved in AD. New key elements of specificity provide determinants of molecular recognition important for the assembly of macromolecular complexes. In this review, we discuss aberrant spatial distribution of neuronal polypeptides observed in neuropathies: aggregation, association with proteins of the neuronal cytoskeleton, and phosphorylation dependent dynamics. Particularly, we emphasize recent advancements in understanding the function and determinants of specific association of molecules involved in Alzheimer's disease with respect to the topographic regulation of phosphorylation in neuronal cytoskeleton and implications for the design of new therapies. Further, we address the role of various filament systems in maintenance of the shape, rigidity and dynamics of the cytoskeleton.

Allosteric modulators of MEK1: drug design and discovery

Mitogen-activated protein kinase kinase (MAPKK, MEK) mediates signal transduction, controlling cell proliferation and survival. MEK occupies a key downstream position in the Ras-Raf-MEK-ERK signaling pathway, implying that inhibition of MEK will potently suppress tumor cell growth, with potential applications in cancer therapy. Based on the promising therapeutic effects of MEK modulators, continued efforts have been made in this class. Here, we review the discovery and development of MEK1 allosteric modulators, classifying them into four structural groups. The allosteric mechanisms and recent clinical progress involving these modulators are also reviewed.

Shaping of interphase chromosomes by the microtubule network

It is well established that microtubule dynamics play a major role in chromosome condensation and localization during mitosis. During interphase, however, it is assumed that the metazoan nuclear envelope presents a physical barrier, which inhibits interaction between the microtubules located in the cytoplasm and the chromatin fibers located in the nucleus. In recent years, it has become apparent that microtubule dynamics alter chromatin structure and function during interphase as well. Microtubule motor proteins transport several transcription factors and exogenous DNA (such as plasmid DNA) from the cytoplasm to the nucleus. Various soluble microtubule components are able to translocate into the nucleus, where they bind various chromatin elements leading to transcriptional alterations. In addition, microtubules may apply force on the nuclear envelope, which is transmitted into the nucleus, leading to changes in chromatin structure. Thus, microtubule dynamics during interphase may affect chromatin spatial organization, as well as transcription, replication and repair.

Proteomic analysis of high NaCl-induced changes in abundance of nuclear proteins

Mammalian cells are normally stressed by high interstitial NaCl in the renal medulla and by lesser elevation of NaCl in several other tissues. High NaCl damages proteins and DNA and can kill cells. Known protective responses include nuclear translocation of the transcription factor NFAT5 and other proteins. In order better to understand the extent and significance of changes in nuclear protein abundance, we extracted nuclear and cytoplasmic proteins separately from HEK293 cells and measured by LC-MS/MS (iTRAQ) changes of abundance of proteins in the extracts in response to high NaCl at three time points: 1 h, 8 h, and adapted for two passages. We confidently identified a total of 3,190 proteins; 163 proteins changed significantly at least at one time point in the nucleus. We discerned the biological significance of the changes by Gene Ontology and protein network analysis. Proteins that change in the nucleus include ones involved in protein folding and localization, microtubule-based process, regulation of cell death, cytoskeleton organization, DNA metabolic process, RNA processing, and cell cycle. Among striking changes in the nucleus, we found a decrease of all six 14-3-3 isoforms; dynamic changes of "cytoskeletal" proteins, suggestive of nucleoskeletal reorganization; rapid decrease of tubulins; and dynamic changes of heat shock proteins. Identification of these changes of nuclear protein abundance enhances our understanding of high NaCl-induced cellular stress, and provides leads to previously unknown damages and protective responses.

Nucleocytoplasmic shuttling of cytoskeletal proteins: molecular mechanism and biological significance

Various nuclear functional complexes contain cytoskeletal proteins as regulatory subunits; for example, nuclear actin participates in transcriptional complexes, and actin-related proteins are integral to chromatin remodeling complexes. Nuclear complexes such as these are involved in both basal and adaptive nuclear functions. In addition to nuclear import via classical nuclear transport pathways or passive diffusion, some large cytoskeletal proteins spontaneously migrate into the nucleus in a karyopherin-independent manner. The balance of nucleocytoplasmic distribution of such proteins can be altered by several factors, such as import versus export, or capture and release by complexes. The resulting accumulation or depletion of the nuclear populations thereby enhances or attenuates their nuclear functions. We propose that such molecular dynamics constitute a form of cytoskeleton-modulated regulation of nuclear functions which is mediated by the translocation of cytoskeletal components in and out of the nucleus.

Targeting Notch signaling pathway to overcome drug resistance for cancer therapy

Chemotherapy is an important therapeutic strategy for cancer treatment and remains the mainstay for the management of human malignancies; however, chemotherapy fails to eliminate all tumor cells because of intrinsic or acquired drug resistance, which is the most common cause of tumor recurrence. Recently, emerging evidences suggest that Notch signaling pathway is one of the most important signaling pathways in drug-resistant tumor cells. Moreover, down-regulation of Notch pathway could induce drug sensitivity, leading to increased inhibition of cancer cell growth, invasion, and metastasis. This article will provide a brief overview of the published evidences in support of the roles of Notch in drug resistance and will further summarize how targeting Notch by "natural agents" could become a novel and safer approach for the improvement of tumor treatment by overcoming drug resistance.

Intravenous paclitaxel is specifically retained in human gynecologic carcinoma tissues in vivo

Paclitaxel and carboplatin are commonly used and well-tolerated agents for gynecologic malignancies. The persistence of platinum in human tissues for 14 days and the long-term retention of platinum in tissues for up to 17 months have been reported. Paclitaxel remains in human uterine cervical cancer tissues for 6 days. These findings prompted us to determine the retention of paclitaxel and carboplatin in human uterine cervical carcinoma, endometrial carcinoma, ovarian carcinoma, and pelvic lymph nodes to establish baseline parameters and guide the development of more effective treatment interventions. Thirty patients with uterine or ovarian carcinomas were treated with intravenous weekly paclitaxel-carboplatin chemotherapy before surgery. The concentrations of these agents in carcinoma tissue, normal cervical, myometrial and ovarian tissues, and pelvic lymph nodes were measured 5 days after the final administration. Paclitaxel was specifically retained in cervical, endometrial, and ovarian carcinoma tissues but was not detected in lymph nodes. In contrast to paclitaxel, carboplatin was readily detectable with similar levels in all tumor-associated and normal host tissues. In addition, a low paclitaxel concentration in cervical carcinoma tissue was significantly associated with short progression-free survival and overall survival. Further studies are needed to clarify the tissue distribution of anticancer drugs in humans and promote optimal treatment strategies enhancing paclitaxel lymphatic targeting.

Intracellular beta-tubulin/chaperonin containing TCP1-beta complex serves as a novel chemotherapeutic target against drug-resistant tumors

In the present study, treatment of HEK-293 cells with the synthetic small molecule N-iodoacetyl-tryptophan (I-Trp) at submicromolar concentrations efficiently induced cell apoptosis as judged from the accumulation of sub-G(0) cells and intracellular DNA fragmentation. Activation of all intracellular caspases, except caspase-1, was detected in I-Trp-treated cells. Proteomic analysis revealed that beta-tubulin acted as a specific intracellular target of I-Trp. Protein fingerprinting analysis indicated that the Cys(354) residue in the peptide fragment TAVCDIPPR of beta-tubulin, which is located at the binding interface with chaperonin containing TCP1-beta (CCT-beta), was alkylated by I-Trp. Moreover, site-directed mutagenesis of Cys(354) (Cys-Ala) abolished the incorporation of I-Trp into beta-tubulin, suggesting Cys(354) is indeed the targeting site of I-Trp. Immunoprecipitation showed that the beta-tubulin/CCT-beta complex was constitutively formed but disrupted after treatment with I-Trp. Overexpression of the truncated beta-tubulin (T351-S364) or treatment with I-Trp or the synthetic peptide Myr-TAVCDIPPRG caused more severe cell apoptosis in multidrug-resistant MES-SA/Dx5 cancer cells due to higher levels of CCT-beta relative to wild-type MES-SA cancer cells. Silencing the expression of CCT-beta rendered MES-SA/Dx5 cells less sensitive to I-Trp-induced apoptotic cell death. These findings suggest that the beta-tubulin/CCT-beta complex may serve as an effective chemotherapeutic target for treating clinical tubulin-binding agent-resistant or CCT-beta-overexpressing tumors.

The autonomous notch signal pathway is activated by baicalin and baicalein but is suppressed by niclosamide in K562 cells

The Notch signaling pathway plays important roles in a variety of cellular processes. Aberrant transduction of Notch signaling contributes to many diseases and cancers in humans. The Notch receptor intracellular domain, the activated form of Notch receptor, is extremely difficult to detect in normal cells. However, it can activate signaling at very low protein concentration to elicit its biological effects. In the present study, a cell based luciferase reporter gene assay was established in K562 cells to screen drugs which could modulate the endogenous CBF1‐dependent Notch signal pathway. Using this system, we found that the luciferase activity of CBF1‐dependent reporter gene was activated by baicalin and baicalein but suppressed by niclosamide in both dose‐ and time‐dependent manners. Treatment with these drugs modulated endogenous Notch signaling and affected mRNA expression levels of Notch1 receptor and Notch target genes in K562 cells. Additionally, erythroid differentiation of K562 cells was suppressed by baicalin and baicalein yet was promoted by niclosamide. Colony‐forming ability in soft agar was decreased after treatment with baicalin and baicalein, but was not affected in the presence of niclosamide. Thus, modulation of Notch signaling after treatment with any of these three drugs may affect tumorigenesis of K562 cells suggesting that these drugs may have therapeutic potential for those tumors associated with Notch signaling. Taken together, this system could be beneficial for screening of drugs with potential to treat Notch signal pathway‐associated diseases. J. Cell. Biochem. 106: 682–692, 2009. © 2009 Wiley‐Liss, Inc.

Nucleocytoplasmic shuttling of soluble tubulin in mammalian cells

We have investigated the subcellular distribution and dynamics of soluble tubulin in unperturbed and transfected HeLa cells. Under normal culture conditions, endogenous alpha/beta tubulin is confined to the cytoplasm. However, when the soluble pool of subunits is elevated by combined cold-nocodazole treatment and when constitutive nuclear export is inhibited by leptomycin B, tubulin accumulates in the cell nucleus. Transfection assays and FRAP experiments reveal that GFP-tagged beta-tubulin shuttles between the cytoplasm and the cell nucleus. Nuclear import seems to occur by passive diffusion, whereas exit from the nucleus appears to rely on nuclear export signals (NESs). Several such motifs can be identified by sequence criteria along the beta-tubulin molecule and mutations in one of these (NES-1) cause a significant accumulation in the nuclear compartment. Under these conditions, the cells are arrested in the G0-G1 phase and eventually die, suggesting that soluble tubulin interferes with important nuclear functions. Consistent with this interpretation, soluble tubulin exhibits stoichiometric binding to recombinant, normally modified and hyper-phosphorylated/acetylated histone H3. Tubulin-bound H3 no longer interacts with heterochromatin protein 1 and lamin B receptor, which are known to form a ternary complex under in vitro conditions. Based on these observations, we suggest that nuclear accumulation of soluble tubulin is part of an intrinsic defense mechanism, which tends to limit cell proliferation under pathological conditions. This readily explains why nuclear tubulin has been detected so far only in cancer or in transformed cells, and why accumulation of this protein in the nucleus increases after treatment with chemotherapeutic agents.

p150/glued modifies nuclear estrogen receptor function

Estrogen modulates gene expression through interactions with estrogen receptors (ERs) that bind chromosomal target genes. Recent studies have suggested an interaction between the cytoskeletal system and estrogen signaling; these have implicated a role of cytoplasmic microtubules in scaffolding ERalpha and enhancing nongenomic function; in addition, other experiments demonstrate that dynein light chain 1 may chaperone ERalpha to the nucleus, indirectly increasing transcriptional potency. Actin/myosin and dynein light chain 1 are also required for estrogen-mediated chromosomal movement that is required for transcriptional up-regulation of ERalpha targets. We present evidence that the dynactin component, p150/glued, directly influences the potency of nuclear ER function. Increasing the stoichiometric ratio of p150/glued and ERalpha by overexpression enhances estrogen responses. ERalpha enhancement by p150/glued does not appear to be influenced by shifts in subcellular localization because microtubule disruption fails to increase nuclear ERalpha. Rather, we find that modest amounts of p150/glued reside in the nucleus of cells, suggesting that it plays a direct role in nuclear transcription. Notably, p150/glued is recruited to the pS2 promoter in the presence of hormone, and, in MCF-7 cells, knockdown of p150/glued levels reduces estrogen-dependent transcription. Our results suggest that p150/glued modulates estrogen sensitivity in cells through nuclear mechanisms.

The activated Notch1 receptor cooperates with alpha-enolase and MBP-1 in modulating c-myc activity

The Notch signal pathway plays multifaceted roles to promote or suppress tumorigenesis. The Notch1 receptor intracellular domain (N1IC), the activated form of the Notch1 receptor, activates the c-myc proto-oncogene. The complex of N1IC and transcription factor YY1 binds to the human c-myc promoter to enhance c-myc expression in a CBF1-independent manner. Here we demonstrated that N1IC interacted with the c-Myc-regulating proteins alpha-enolase and c-myc promoter binding protein 1 (MBP-1). Both alpha-enolase and MBP-1 suppressed the N1IC-enhanced activity of the c-myc promoter in a CBF1-independent manner. The YY1 response element in front of the P2 c-myc promoter was essential and sufficient for the modulation of c-myc by N1IC and alpha-enolase or MBP-1. Furthermore, N1IC, YY1, and alpha-enolase or MBP-1 but not CBF1 bound to the c-myc promoter through associating with the YY1 response element. Hemin-induced erythroid differentiation was suppressed by N1IC in K562 cells. This suppression was relieved by the expression of alpha-enolase and MBP-1. In addition, both alpha-enolase and MBP-1 suppressed the N1IC-enhanced colony-forming ability through c-myc. These results indicate that the activated Notch1 receptor and alpha-enolase or MBP-1 cooperate in controlling c-myc expression through binding the YY1 response element of the c-myc promoter to regulate tumorigenesis.

Normal and prostate cancer cells display distinct molecular profiles of alpha-tubulin posttranslational modifications

BACKGROUND

Multiple diverse posttranslational modifications of alpha-tubulin such as detyrosination, further cleavage of the penultimate glutamate residue (Delta2-tubulin), acetylation, and polyglutamylation increase the structural and functional diversity of microtubules.

METHODS

Herein, we characterized the molecular profile of alpha-tubulin posttranslational modifications in normal human prostate epithelial cells (PrEC), immortalized normal prostate epithelial cells (PZ-HPV-7), androgen-dependent prostate cancer cells (LNCaP), transitional androgen-independent prostate cancer cells (LNCaP-cds and CWR22Rv1), and androgen-independent prostate cancer cells (PC3).

RESULTS

Compared to PrEC and PZ-HPV-7 cells, all cancer cells exhibited elevated levels of detyrosinated and polyglutamylated alpha-tubulin, that was paralleled by decreased protein levels of tubulin tyrosine ligase (TTL). In contrast, PrEC and PZ-HPV-7 cells expressed markedly higher levels of Delta2-tubulin. Whereas alpha-tubulin acetylation levels were generally equivalent in all the cell lines, PC3 cells did not display detectable levels of Ac-tubulin.

CONCLUSION

These data may reveal novel biomarkers of prostate cancer and new therapeutic targets.