Proteolysis of microtubule associated protein 2 and sensitivity of pancreatic tumours to docetaxel

Expression of the microtubule-associated protein 2 (MAP2) as a potential independent prognostic marker in prostate cancer

PURPOSE

Investigation of Microtubuli-associated Protein 2 (MAP2) expression and its clinical relevance in prostate cancer.

MATERIAL AND METHODS

MAP2 expression was immunohistochemically analysed on radical prostatectomy specimens using whole block sections (n = 107) and tissue microarrays (TMA; n = 310). The staining intensity was evaluated for carcinoma, benign tissue and prostatic intraepithelial neoplasia. Expression data were correlated with clinicopathological parameters and biochemical recurrence-free survival. Additionally, MAP2 protein expression was quantitatively analysed in the serum of histologically confirmed prostate carcinoma patients and the control group using a commercial enzyme-linked immunosorbent assay.

RESULTS

MAP2 staining was significantly stronger in neoplastic tissue than in non-neoplastic prostatic glands, both in whole block sections (p < 0.01) and in TMA sections (p < 0.05). TMA data revealed significantly stronger MAP2 staining in high-grade tumors. Survival analysis showed a significant correlation between strong MAP2 staining in carcinoma and shortened biochemical recurrence-free survival after prostatectomy (p < 0.001). Multivariate Cox regression analysis confirmed MAP2 as an independent predictor for an unfavourable course. Mean MAP2 serum levels for non-PCA vs. PCA patients differed significantly (non-PCA = 164.7 pg/ml vs. PCA = 242.5 pg/ml, p < 0.001).

CONCLUSION

The present data support MAP2 as a novel biomarker in PCA specimens. MAP2 is correlated with tumor grade and MAP2 high-expressing PCA is associated with an increased risk of biochemical recurrence after radical prostatectomy. Future studies are necessary to evaluate MAP2 as a valuable immunohistochemical biomarker in preoperative PCA diagnostic procedures, in particular with regard to treatment modalities.

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.

Network Pharmacology Analysis, Molecular Docking, and In Vitro Verification Reveal the Action Mechanism of Prunella vulgaris L. in Treating Breast Cancer

Background

Prunella vulgaris L. is effective in the treatment of breast cancer (BRCA); however, the underlying mechanism is still unclear. The aim of this study was to elucidate the mechanism of treatment of BRCA by P. vulgaris using network pharmacology and molecular docking technology, and to verify the experimental results using human BRCA MDA-MB-231 cells.

Methods

Active components and action targets of P. vulgaris were determined using the TCMSP™, SwissTarget Prediction™, and TargetNet™ databases. GeneCards™ and OMIM™ provided BRCA targets. After obtaining common targets, a protein-protein interaction (PPI) network was constructed using the STRING™ database, and Gene Ontology and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analyses were conducted using the Xiantao™ academic database. Cytoscape™ was used to construct "single drug-disease-component-target" and "single drug-disease-component-target-pathway" networks. The Human Protein Atlas™ was used to determine protein expression levels in BRCA cell lines. AutoDock tools™ were used to carry out molecular docking for the first 10 targets of quercetin and the PPI network. Finally, the abovementioned results were verified using cell experiments.

Results

We obtained 11 active components, 198 targets, and 179 common targets, including DUOX2, MET, TOP2A, and ERBB3. The results of KEGG pathway analysis screened 188 related signaling pathways and indicated the potential key role of PI3K-Akt and MAPK signaling pathways in the antibreast cancer process of P. vulgaris. The results of molecular docking showed that the first 10 targets of quercetin interacted well with the protein network. Cell experiments showed that quercetin effectively inhibited the proliferation of MDA-MB-231 cells by regulating apoptosis and cell cycle, which may be partly related to the MAPK signaling pathway.

Conclusion

Synergistic effects of multiple components, targets, and pathways on the anti-BRCA activity of P. vulgaris could provide a theoretical basis for further study on its complex anti-BRCA mechanism.

Microtubule-associated protein 2 knockdown sensitizes glioma cells to vincristine treatment

Gliomas are the most common and lethal tumor of the central nervous system (CNS). At present, standard treatment involves chemotherapy and radiotherapy after surgery, but the prognosis for most gliomas remains poor due to tumor heterogeneity and drug resistance. Microtubule-associated protein 2 (MAP2), a microtubule-stabilizing protein, plays a critical role in many cellular processes and may correlate with the proliferation, apoptosis, and drug sensitivity of tumor cells, especially their sensitivity to microtubule-targeting drugs (MTDs). In this study, we investigated the role of MAP2 in gliomas and its relationship to the chemosensitivity of vincristine (VCR), an MTD commonly used in glioma chemotherapy. We downregulated MAP2 expression in glioma cells using RNA interference, observed the resultant changes in the biological characteristics of the cells, and tested their drug sensitivity to VCR by MTT assay. The results show downregulation of MAP2 in glioma cells significantly inhibited cell viability and migration, induced apoptosis, and increased sensitivity to VCR in vitro. Our findings suggest that MAP2 may be a useful molecular marker in MTD chemotherapy and a potential therapeutic target in gliomas.

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.

Proteomic analysis of gemcitabine-resistant pancreatic cancer cells reveals that microtubule-associated protein 2 upregulation associates with taxane treatment

Background:

Chemoresistance hampers the treatment of patients suffering from pancreatic ductal adenocarcinoma (PDAC). Here we aimed to evaluate the (phospho)proteome of gemcitabine-sensitive and gemcitabine-resistant PDAC cells to identify novel therapeutic targets and predictive biomarkers.

Methods:

The oncogenic capabilities of gemcitabine-sensitive and resistant PDAC cells were evaluated in vitro and in vivo. Cultured cells were analyzed by label-free proteomics. Differential proteins and phosphopeptides were evaluated by gene ontology and for their predictive or prognostic biomarker potential with immunohistochemistry of tissue microarrays.

Results:

Gemcitabine-resistant cells had increased potential to induce xenograft tumours (p value < 0.001). Differential analyses showed that proteins associated with gemcitabine resistance are correlated with microtubule regulation. Indeed, gemcitabine-resistant cells displayed an increased sensitivity for paclitaxel in vitro (p < 0.001) and nab-paclitaxel had a strong anti-tumour efficacy in vivo. Microtubule-associated protein 2 (MAP2) was found to be highly upregulated (p = 0.002, fold change = 10) and phosphorylated in these resistant cells. Expression of MAP2 was correlated with a poorer overall survival in patients treated with gemcitabine in the palliative (p = 0.037) and adjuvant setting (p = 0.014).

Conclusions:

These data show an explanation as to why the combination of gemcitabine with nab-paclitaxel is effective in PDAC patients. The identified gemcitabine-resistance marker, MAP2, emerged as a novel prognostic marker in PDAC patients treated with gemcitabine and warrants further clinical investigation.

Targeting mitotic pathways for endocrine-related cancer therapeutics

A colossal amount of basic research over the past few decades has provided unprecedented insights into the highly complex process of cell division. There is an ever-expanding catalog of proteins that orchestrate, participate and coordinate in the exquisite processes of spindle formation, chromosome dynamics and the formation and regulation of kinetochore microtubule attachments. Use of classical microtubule poisons has still been widely and often successfully used to combat a variety of cancers, but their non-selective interference in other crucial physiologic processes necessitate the identification of novel druggable components specific to the cell cycle/division pathway. Considering cell cycle deregulation, unscheduled proliferation, genomic instability and chromosomal instability as a hallmark of tumor cells, there lies an enormous untapped terrain that needs to be unearthed before a drug can pave its way from bench to bedside. This review attempts to systematically summarize the advances made in this context so far with an emphasis on endocrine-related cancers and the avenues for future progress to target mitotic mechanisms in an effort to combat these dreadful cancers.

End-binding protein 1 stimulates paclitaxel sensitivity in breast cancer by promoting its actions toward microtubule assembly and stability

Paclitaxel is a microtubule-targeting agent widely used for the treatment of many solid tumors. However, patients show variable sensitivity to this drug, and effective diagnostic tests predicting drug sensitivity remain to be investigated. Herein, we show that the expression of end-binding protein 1 (EB1), a regulator of microtubule dynamics involved in multiple cellular activities, in breast tumor tissues correlates with the pathological response of tumors to paclitaxel-based chemotherapy. In vitro cell proliferation assays reveal that EB1 stimulates paclitaxel sensitivity in breast cancer cell lines. Our data further demonstrate that EB1 increases the activity of paclitaxel to cause mitotic arrest and apoptosis in cancer cells. In addition, microtubule binding affinity analysis and polymerization/depolymerization assays show that EB1 enhances paclitaxel binding to microtubules and stimulates the ability of paclitaxel to promote microtubule assembly and stabilization. These findings thus reveal EB1 as a critical regulator of paclitaxel sensitivity and have important implications in breast cancer chemotherapy.

Identification of markers of taxane sensitivity using proteomic and genomic analyses of breast tumors from patients receiving neoadjuvant paclitaxel and radiation

PURPOSE

To identify molecular markers of pathologic response to neoadjuvant paclitaxel/radiation treatment, protein and gene expression profiling were done on pretreatment biopsies.

EXPERIMENTAL DESIGN

Patients with high-risk, operable breast cancer were treated with three cycles of paclitaxel followed by concurrent paclitaxel/radiation. Tumor tissue from pretreatment biopsies was obtained from 19 of the 38 patients enrolled in the study. Protein and gene expression profiling were done on serial sections of the biopsies from patients that achieved a pathologic complete response (pCR) and compared to those with residual disease, non-pCR (NR).

RESULTS

Proteomic and validation immunohistochemical analyses revealed that alpha-defensins (DEFA) were overexpressed in tumors from patients with a pCR. Gene expression analysis revealed that MAP2, a microtubule-associated protein, had significantly higher levels of expression in patients achieving a pCR. Elevation of MAP2 in breast cancer cell lines led to increased paclitaxel sensitivity. Furthermore, expression of genes that are associated with the basal-like, triple-negative phenotype were enriched in tumors from patients with a pCR. Analysis of a larger panel of tumors from patients receiving presurgical taxane-based treatment showed that DEFA and MAP2 expression as well as histologic features of inflammation were all statistically associated with response to therapy at the time of surgery.

CONCLUSION

We show the utility of molecular profiling of pretreatment biopsies to discover markers of response. Our results suggest the potential use of immune signaling molecules such as DEFA as well as MAP2, a microtubule-associated protein, as tumor markers that associate with response to neoadjuvant taxane-based therapy.

Microtubule-associated proteins as targets in cancer chemotherapy

Natural and synthetic compounds that disrupt microtubule dynamics are among the most successful and widely used cancer chemotherapeutic agents. However, lack of reliable markers that predict sensitivity of cancers to these agents and development of resistance remain vexing issues. There is accumulating evidence that a family of cellular proteins that are associated with and alter the dynamics of microtubules can determine sensitivity of cancer cells to microtubule-targeting agents and play a role in tumor cell resistance to these agents. This growing family of microtubule-associated proteins (MAP) includes products of oncogenes, tumor suppressors, and apoptosis regulators, suggesting that alteration of microtubule dynamics may be one of the critical events in tumorigenesis and tumor progression. The objective of this review is to integrate the knowledge on these seemingly unrelated proteins that share a common function and examine their relevance to microtubule-targeting therapies and highlight MAPs-tubulin-drug interactions as a novel avenue for new drug discovery. Based on the available evidence, we propose that rational microtubule-targeting cancer therapeutic approaches should ideally include proteomic profiling of tumor MAPs before administration of microtubule-stabilizing/destabilizing agents preferentially in combination with agents that modulate the expression of relevant MAPs.

Transcriptional regulation of human MAP2 gene in melanoma: role of neuronal bHLH factors and Notch1 signaling

Microtubule-associated protein 2 (MAP2), a neuron-specific protein, stabilizes microtubules and is critical for neurite outgrowth and dendrite development. Although MAP2 is widely used as a marker of neuronal differentiation, regulation of its transcription has not been investigated. We showed that MAP2 is frequently activated in human cutaneous melanoma. Here, we identified a 2.2 kb region that is sufficient for neuronal-specific expression in vitro and in vivo. Comparative analysis of the mouse, rat and human MAP2 promoter sequences showed the presence of a conserved bHLH factor binding sites. Electrophoretic mobility shift analysis, promoter mutagenesis and co-transfection experiments showed that NeuroD, a pro-neuronal differentiation factor, and Hairy and Enhancer of Split (HES1), a transcription repressor, are involved in the regulation of MAP2 promoter activity. Melanoma cells express both NeuroD and HES1. Chromatin immunoprecipitation showed that in metastatic melanoma cells N-box region of the MAP2 promoter is occupied by endogenous HES1. We show that the inhibition of Notch signaling, a regulator of HES1 gene expression, and/or shRNA knockdown of HES1 results in the upregulation of MAP2 promoter activity. Thus, our data suggest that Notch signaling, which is implicated in melanoma progression, and HES1 play a role in MAP2 gene regulation during melanoma progression.

Emerging drugs in pancreatic cancer

Improving survival in patients with pancreatic cancer remains a formidable challenge. For the few patients with localised stages of the disease, intra-operative radiotherapy, adjuvant chemoradiotherapy and neo-adjuvant therapies remain non-validated and the survival benefit conferred by 5-fluorouracil-folinic acid adjuvant chemotherapy over radical surgery alone is still a matter of debate. Gemcitabine has recently emerged as the standard single agent in advanced stages of the disease and pharmacokinetic refinements such as the use of a fixed-dose infusion rate may further improve still rather modest result figures. At present, most efforts deal with the development of more effective doublet or triplet therapies, combining gemcitabine with either conventional cytotoxic drugs--the most promising being oxaliplatin--or more innovative, targeted therapeutic agents. Among these agents, matrix metalloprotease inhibitors and farnesyltransferase inhibitors have already undergone Phase III trials, alone or in combination with gemcitabine, with rather disappointing results. However, preclinical and Phase I and II studies of cyclooxygenase-2 or lipoxygenase inhibitors, various immunotherapeutic approaches and several tyrosine kinase inhibitors or monoclonal antibodies against growth factors or their receptors are encouraging and may provide some hope for patients with pancreatic cancer.

Microtubule-associated protein 2, a marker of neuronal differentiation, induces mitotic defects, inhibits growth of melanoma cells, and predicts metastatic potential of cutaneous melanoma

Dynamic instability of microtubules is critical for mitotic spindle assembly and disassembly during cell division, especially in rapidly dividing tumor cells. Microtubule-associated proteins (MAPs) are a family of proteins that influence this property. We showed previously that MAP2, a neuron-specific protein that stabilizes microtubules in the dendrites of postmitotic neurons, is induced in primary cutaneous melanoma but is absent in metastatic melanomas. We proposed that induction of a microtubule-stabilizing protein in primary melanoma could disrupt the dynamic instability of microtubules, inhibit cell division and prevent or delay tumor progression. Here we show, by Kaplan-Meier survival and multivariate Cox regression analysis, that patients diagnosed with MAP2+ primary melanomas have significantly better metastatic disease-free survival than those with MAP2- disease. Investigation of the mechanisms that underlie the effect of MAP2 on melanoma progression showed that MAP2 expression in metastatic melanoma cell lines leads to microtubule stabilization, cell cycle arrest in G2-M phase and growth inhibition. Disruption of microtubule dynamics by MAP2 resulted in multipolar mitotic spindles, defects in cytokinesis and accumulation of cells with large nuclei, similar to those seen in vivo in MAP2+ primary melanomas cells. These data suggest that ectopic activation of a neuronal differentiation gene in melanoma during early tumor progression inhibits cell division and correlates with inhibition or delay of metastasis.

MAP-2 expression in the human adenohypophysis and in pituitary adenomas. An immunohistochemical study

MAP-2, a well characterized member of the microtubule associated protein (MAP) family, binds to and stabilizes microtubules and is involved in cell proliferation as well as neuronal differentiation. The aim of the present work was to study MAP-2 expression in human adenohypophyses and pituitary adenomas. To our knowledge, data regarding MAP-2 expression in human pituitaries has not been reported to date. For immunohistochemistry, the streptavidin-biotin-peroxidase complex method was used. Nine non-tumorous adenohypophyses and 77 adenomas (GH-, PRL-, ACTH-, TSH-, FSH/LH- and/or alpha subunit- producing or immunonegative tumors) were investigated. The results show that MAP-2 is expressed in the cytoplasm of non-tumorous adenohypophysial cells as well as of various pituitary adenoma types. No significant correlation was found between MAP-2 expression and gender, patient age, mitotic activity, MIB-1 labelling indices, hormone immunoprofile, and endocrine status, ie. hormonal activity or lack thereof. Thus MAP-2 expression cannot be used to estimate cell proliferation rate, growth potential, endocrine activity or biologic behaviour of an adenoma. Immunopositivity appeared to be stronger in the cytoplasm of adenoma cells than in that of non-tumorous adenohypophysial cells, implying that the adenoma cells contain larger quantities of MAP-2. It can be concluded that the functional activity of MAP-2 is not associated with the manufacture of any specific adenohypophysial hormone(s) and is not limited to one specific cell type.

The future in advanced prostate cancer: take your partners or is the last dance for me?

Recent therapeutic initiatives have improved quality of life and survival for patients with advanced prostate cancer. This review focuses predominantly on prostate cancer that has become refractory to standard androgen ablation treatment. Planned trials will answer further questions on the optimal use and sequencing of currently available hormonal agents, cytotoxic therapies, and radiolabeled nucleotides. Future therapeutic advances are likely to come in 2 areas: targeted therapies and response prediction. Molecular targeted agents will be most useful in combination with each other or with established systemic therapies. The selection of combinations will require the application of paradigms targeting key biochemical pathways and specific microenvironments in prostate cancer. Response prediction for individual patients may be assisted by either pretreatment or sequential molecular profiling, or sequential imaging, or biochemical studies that predicate outcome prior to or soon after treatment has been initiated. To bring these advances to the metastatic prostate cancer patient, a series of well-designed clinical trials is needed that integrates the lessons learned through laboratory, translational, and clinical studies in recent years.

Taxotere resistance in SUIT Taxotere resistance in pancreatic carcinoma cell line SUIT 2 and its sublines

AIM: To investigate the specific mechanisms of intrinsic and acquired resistance to taxotere (TXT) in pancreatic adenocarcinoma (PAC).

METHODS: MTT assay was used to detect the sensitivity of PAC cell line SUIT-2 and its sublines (S-007, S-013, S-020, S-028 and TXT selected SUIT-2 cell line, S2/TXT) to TXT. Mdr1 (P-gp), multidrug resistance associated protein (MRP), lung resistance protein (LRP) and β-tubulin isotype gene expressions were detected by RT-PCR. The functionality of P-gp and MRP was tested using their specific blocker verapamil (Ver) and indomethacin (IMC), respectively. The transporter activity of P-gp was also confirmed by Rhodamine 123 accumulation assay.

RESULTS: S-020 and S2/TXT were found to be significantly resistant to TXT (19 and 9.5-fold to their parental cell line SUIT-2, respectively). RT-PCR demonstrated strong expression of Mdr1 in these two cell lines, but weaker expression or no expression in other cells lines. MRP and LRP expressions were found in most of these cell lines. The TXT-resistance in S2-020 and S2/TXT could be reversed almost completely by Ver, but not by IMC. Flow cytometry showed that Ver increased the accumulation of Rhodamine-123 in these two cell lines. Compared with S-020 and SUIT-2, the levels of β-tubulin isotype II, III expressio ns in S-2/TXT were increased remarkably.

CONCLUSION: The both intrinsic and acquired TXT-related drug resistance in these PAC cell lines is mainly mediated by P-gp, but had no relationship to MRP and LRP express ions. The increases of β-tubulin isotype II, III might be collateral changes that occur when the SUIT-2 cells are treated with TXT.

Expression of microtubule-associated protein 2 in benign and malignant melanocytes: implications for differentiation and progression of cutaneous melanoma

Cutaneous melanocytic neoplasms are known to acquire variable characteristics of neural crest differentiation. Melanocytic nevus cells in the dermis and desmoplastic melanomas often display characteristics of nerve sheath differentiation. The extent and nature of neuronal differentiation characteristics displayed by primary and metastatic melanoma cells are not well understood. Here, we describe induction of a juvenile isoform of microtubule-associated protein 2 (MAP-2c) in cultured metastatic melanoma cells by the differentiation inducer hexamethylene bisacetamide. Up-regulation of this MAP-2 isoform, a marker for immature neurons, is accompanied by extended dendritic morphology and down-regulation of tyrosinase-related protein 1 (TYRP1/gp75), a melanocyte differentiation marker. In a panel of cell lines that represent melanoma tumor progression, MAP-2c mRNA and the corresponding approximately 70-kd protein could be detected predominantly in primary melanomas. Immunohistochemical analysis of 61 benign and malignant melanocytic lesions showed abundant expression of MAP-2 protein in melanocytic nevi and in the in situ and invasive components of primary melanoma, but only focal heterogeneous expression in a few metastatic melanomas. In contrast, MAP-2-positive dermal nevus cells and the invasive cells of primary melanomas were TYRP1-negative. This reciprocal staining pattern in vivo is similar to the in vitro observation that induction of the neuronal marker MAP-2 in metastatic melanoma cells is accompanied by selective extinction of the melanocytic marker TYRP1. Our data show that neoplastic melanocytes, particularly at early stages, retain the plasticity to express the neuron-specific marker MAP-2. These observations are consistent with the premise that both benign and malignant melanocytes in the dermis can express markers of neuronal differentiation.