The 1p-encoded protein stathmin and resistance of malignant gliomas to nitrosoureas

Restricting Colorectal Cancer Cell Metabolism with Metformin: An Integrated Transcriptomics Study

BACKGROUND

Metformin is a first-line therapy for type 2 diabetes as it disrupts cellular metabolism. Despite the association between metformin and lower cancer incidence, the anti-tumour activity of the drug in colorectal cancer (CRC) is incompletely understood. This study identifies underlying molecular mechanisms by which metformin slows colorectal cancer cell proliferation by investigating metformin-associated microRNA (miRNA) and target gene pairs implicated in signalling pathways.

METHODS

The present study analysed changes in miRNAs and the coding transcriptome in CRC cells treated with a sublethal dose of metformin, followed by the contextual validation of potential miRNA-target gene pairs.

RESULTS

Analyses of small RNA and transcriptome sequencing data revealed 104 miRNAs and 1221 mRNAs to be differentially expressed in CRC cells treated with metformin for 72 h. Interaction networks between differentially expressed miRNAs and putative target mRNAs were identified. Differentially expressed genes were mainly implicated in metabolism and signalling processes, such as the PI3K-Akt and MAPK/ERK pathways. Further validation of potential miRNA-target mRNA pairs revealed that metformin induced miR-2110 and miR-132-3p to target PIK3R3 and, consequently, regulate CRC cell proliferation, cell cycle progression and the PI3K-Akt signalling pathway. Metformin also induced miR-222-3p and miR-589-3p, which directly target STMN1 to inhibit CRC cell proliferation and cell cycle progression.

CONCLUSIONS

This study identified novel changes in the coding transcriptome and small non-coding RNAs associated with metformin treatment of CRC cells. Integration of these datasets highlighted underlying mechanisms by which metformin impedes cell proliferation in CRC. Importantly, it identified the post-transcriptional regulation of specific genes that impact both metabolism and cell proliferation.

Nucleic acid drug vectors for diagnosis and treatment of brain diseases

Nucleic acid drugs have the advantages of rich target selection, simple in design, good and enduring effect. They have been demonstrated to have irreplaceable superiority in brain disease treatment, while vectors are a decisive factor in therapeutic efficacy. Strict physiological barriers, such as degradation and clearance in circulation, blood-brain barrier, cellular uptake, endosome/lysosome barriers, release, obstruct the delivery of nucleic acid drugs to the brain by the vectors. Nucleic acid drugs against a single target are inefficient in treating brain diseases of complex pathogenesis. Differences between individual patients lead to severe uncertainties in brain disease treatment with nucleic acid drugs. In this Review, we briefly summarize the classification of nucleic acid drugs. Next, we discuss physiological barriers during drug delivery and universal coping strategies and introduce the application methods of these universal strategies to nucleic acid drug vectors. Subsequently, we explore nucleic acid drug-based multidrug regimens for the combination treatment of brain diseases and the construction of the corresponding vectors. In the following, we address the feasibility of patient stratification and personalized therapy through diagnostic information from medical imaging and the manner of introducing contrast agents into vectors. Finally, we take a perspective on the future feasibility and remaining challenges of vector-based integrated diagnosis and gene therapy for brain diseases.

RNA interference for glioblastoma therapy: Innovation ladder from the bench to clinical trials

Glioblastoma multiforme (GBM) is the most common and deadliest type of primary brain tumor with a prognosis of 14months after diagnosis. Current treatment for GBM patients includes "total" tumor resection, temozolomide-based chemotherapy, radiotherapy or a combination of these options. Although, several targeted therapies, gene therapy, and immunotherapy are currently in the clinic and/or in clinical trials, the overall survival of GBM patients has hardly improved over the last two decades. Therefore, novel multitarget modalities are urgently needed. Recently, RNA interference (RNAi) has emerged as a novel strategy for the treatment of most cancers, including GBM. RNAi-based therapies consist of using small RNA oligonucleotides to regulate protein expression at the post-transcriptional level. Despite the therapeutic potential of RNAi molecules, systemic limitations including short circulatory stability and low release into the tumor tissue have halted their progress to the clinic. The effective delivery of RNAi molecules through the blood-brain barrier (BBB) represents an additional challenge. This review focuses on connecting the translational process of RNAi-based therapies from in vitro evidence to pre-clinical studies. We delineate the effect of RNAi in GBM cell lines, describe their effectiveness in glioma mouse models, and compare the proposed drug carriers for the effective transport of RNAi molecules through the BBB to reach the tumor in the brain. Furthermore, we summarize the most important obstacles to overcome before RNAi-based therapy becomes a reality for GBM treatment.

Use of nanoparticles for glioblastoma treatment: a new approach

Glioblastoma (GBM) is a very aggressive CNS tumor with poor prognosis. Current treatment lacks efficacy indicating that new therapeutic approaches are needed. One of these new approaches is based on the use of nanoparticles (NPs) to deliver different cargos (antitumoral drugs or genetic materials) to tumoral cells. This review covers the signaling pathways altered in GBM cells to understand the rationale behind choosing new therapeutic targets and recent advances in the use of different NPs to deliver to GBM cells, both in vitro and in vivo, different therapeutic molecules. A special focus is placed on the effect of NPs on orthotopic brain tumors since this animal model represents the optimal model for translational purposes.

Stathmin is overexpressed and regulated by mutant p53 in oral squamous cell carcinoma

Background

The aim of this study was to investigate the oncogenic function and regulatory mechanism of stathmin in oral squamous cell carcinoma (OSCC).

Methods

Two-dimensional electrophoresis and liquid chromatography-tandem mass chromatography were applied to screen differentiated proteins during carcinogenesis in OSCC. Cell Counting Kit-8 (CCK-8) assays, colony formation, migration, flow cytometry, immunofluorescence and a xenograft model were used to detect the function of stathmin. The correlation between stathmin and p53 expression was analyzed using immunohistochemistry. Mutant/wild type p53 plasmids and small interfering RNA were used to examine the regulation of stathmin. Chromatin immunoprecipitation assays and luciferase assays were performed to detect the transcriptional activation of stathmin by p53.

Results

Overexpression of stathmin was screened and confirmed in OSCC patients and cell lines. Silencing expression of stathmin inhibited proliferation, colony formation and migration and promoted apoptosis. Poly ADP ribose polymerase (PARP) and cyclin-dependent kinase 1 (cdc2) were activated after silencing the expression of stathmin. Suppression of tumorigenicity was also confirmed in vivo. Mutant p53 transcriptionally activated the expression of stathmin in HN6 and HN13 cancer cells, but not in HN30 cells harboring wild type p53.

Conclusions

These results suggest that stathmin acts as an oncogene and is transcriptionally regulated by mutant p53, but not by wild-type p53. Stathmin could be a potential anti-tumor therapeutic target in OSCC.

Electronic supplementary material

The online version of this article (doi:10.1186/s13046-017-0575-4) contains supplementary material, which is available to authorized users.

Overexpression of SCLIP promotes growth and motility in glioblastoma cells

SCLIP, a microtubule-destabilizing phosphoprotein, is known to be involved in the development of the central nervous system (CNS). It has been well established that there are notable parallels between normal development and tumorigenesis, especially in glioma. However, no studies have examined the significance of SCLIP in gliomagenesis. To address this, we investigated the expression of SCLIP and its roles in the development of gliomas. Notably, we found that SCLIP was highly expressed in various grades of glioma samples, as compared with normal brain tissues. Overexpression of SCLIP dramatically stimulated tumor cell migration and invasion as well as proliferation and downregulation of SCLIP showed opposite effects, establishing an important oncogenic role for this gene. Furthermore, we revealed that STAT3 was required to maintain SCLIP stability, suggesting that overexpression of STAT3 may be a critical step to facilitate microtubule dynamics and subsequently promotes migration and invasion of glioma cells. Taken together, our findings demonstrate that SCLIP plays an important role in glioma pathology, and may represent a novel therapeutic strategy against human glioma.

Emerging microtubule targets in glioma therapy

Major advances in the genomics and epigenomics of diffuse gliomas and glioblastoma to date have not been translated into effective therapy, necessitating pursuit of alternative treatment approaches for these therapeutically challenging tumors. Current knowledge of microtubules in cancer and the development of new microtubule-based treatment strategies for high-grade gliomas are the topic in this review article. Discussed are cellular, molecular, and pharmacologic aspects of the microtubule cytoskeleton underlying mitosis and interactions with other cellular partners involved in cell cycle progression, directional cell migration, and tumor invasion. Special focus is placed on (1) the aberrant overexpression of βIII-tubulin, a survival factor associated with hypoxic tumor microenvironment and dynamic instability of microtubules; (2) the ectopic overexpression of γ-tubulin, which in addition to its conventional role as a microtubule-nucleating protein has recently emerged as a transcription factor interacting with oncogenes and kinases; (3) the microtubule-severing ATPase spastin and its emerging role in cell motility of glioblastoma cells; and (4) the modulating role of posttranslational modifications of tubulin in the context of interaction of microtubules with motor proteins. Specific antineoplastic strategies discussed include downregulation of targeted molecules aimed at achieving a sensitization effect on currently used mainstay therapies. The potential role of new classes of tubulin-binding agents and ATPase inhibitors is also examined. Understanding the cellular and molecular mechanisms underpinning the distinct behaviors of microtubules in glioma tumorigenesis and drug resistance is key to the discovery of novel molecular targets that will fundamentally change the prognostic outlook of patients with diffuse high-grade gliomas.

Phase 1 Trial of Bi-shRNA STMN1 BIV in Refractory Cancer

Stathmin1 (STMN1) is a microtubule modulator that is expressed in multiple cancers and correlates with poor survival. We previously demonstrated in vivo safety of bifunctional (bi) shRNA STMN1 bilamellar invaginated vesicle (BIV) and that systemic delivery correlated with antitumor activity. Patients with superficial advanced refractory cancer with no other standard options were entered into trial. Study design involved dose escalation (four patients/cohort) using a modified Fibonacci schema starting at 0.7 mg DNA administered via single intratumoral injection. Biopsy at baseline, 24/48 hours and resection 8 days after injection provided tissue for determination of cleavage product using next-generation sequencing (NGS) and reverse transcription quantitative polymerase chain reaction (RT-qPCR), 5' RLM rapid amplification of cDNA ends (RACE) assay. Serum pharmacokinetics of circulating plasmid was done. Twelve patients were entered into three dose levels (0.7, 1.4, 7.0 mg DNA). No ≥ grade 3 toxic effects to drug were observed. Maximum circulating plasmid was detected at 30 seconds with less than 10% detectable in all subjects at 24 hours. No toxic effects were observed. Predicted cleavage product was detected by both NGS (n = 7/7 patients analyzed, cohorts 1, 2) and RLM RACE (n = 1/1 patients analyzed cohort 3). In conclusion, bi-shRNA STMN1 BIV is well tolerated and detection of mRNA target sequence-specific cleavage product confirmed bi-shRNA BIV mechanism of action.

The prognostic value and therapeutic target role of stathmin-1 in urinary bladder cancer

Background:

The oncoprotein-18/stathmin 1 (STMN1), involved in cell progression and migration, is associated with clinical outcome in breast cancer. Here we aim to investigate its clinical significance in urinary bladder cancer and its possibilities as a therapeutic target.

Methods:

Immunohistochemical analyses of STMN1 protein expression were performed in three patient cohorts: cohort I (n=115 Ta, n=115 T1, n=112 T2–4 stages), cohort II, based on randomised controlled trials (n=239 T1–T4), and cohort III of primary tumour/matched metastasis (n=90 T1–T4). The effects of STMN1 on cell proliferation and migration were evaluated in the urinary bladder cancer cell line, T24, by inhibiting STMN1-cellular expression using siRNA.

Results:

In cohort I, high STMN1 expression correlated to shorter disease-specific survival hazard ratio (HR)=2.04 (95% confidence interval (CI) 1.13–3.68; P=0.02), elevated p53- (P<0.001) and Ki67-protein levels (P<0.001). The survival result was validated in cohort II: HR=1.76 (95% CI 1.04–2.99; P=0.03). In the metastatic bladder cancer material, 70% of the patients were STMN1-positive in both the primary tumour and matched metastases. In vitro, the growth and migration of the T24 cells were significantly reduced (P<0.01, P<0.0001, respectively), when transfecting the cells with STMN1-siRNA.

Conclusions:

STMN1 protein expression has prognostic significance but is primarily a potential treatment target in urinary bladder cancer.

MicroRNA-9 inhibits vasculogenic mimicry of glioma cell lines by suppressing Stathmin expression

The purpose of this study was to investigate the functions of microRNA-9, which is a tissue-specific microRNA in central nervous system, in the vasculogenic mimicry (VM) of glioma cell lines in vitro and in vivo. Glioma cell lines U87MG, U251 and SHG44 were transfected with microRNA-9 mimic, microRNA-9 inhibitor or scramble sequences. The amount of microRNA-9 and Stathmin (STMN1) mRNA was determined by quantitative real-time PCR, and the protein expression of STMN1 was determined by western blot. Cell proliferation and apoptosis were assessed. The interactions between the 3'UTR of STMN1 and miR-9 was determined by luciferase reporter assay. The VM capacity in vitro was evaluated using VM formation assay, and the rescue experiment of STMN1 was carried out in U251 cells. The in vivo experiment was applied with animal models implanted with U87MG cells.MicroRNA-9 mimic transfection reduced proliferation and increased apoptosis in glioma cell lines (p < 0.05). MicroRNA-9 mimic up-regulated STMN1 mRNA levels but reduced its protein levels (p < 0.05), and luciferase activity of STMN1 was suppressed by microRNA-9 mimic transfection (p < 0.05). Furthermore, microRNA-9 mimic transfection suppressed tumor volume growth, as well as VM both in vitro and in vivo. The cell viability and microtube density were upregulated in U251 cells after STMN1 up-regulation (p < 0.05). STMN1 is a target of microRNA-9, and microRNA-9 could modulate cell proliferation, VM and tumor volume growth through controlling STMN1 expression. MicroRNA-9 and its targets may represent a novel panel of molecules for the development of glioma treatment.

Discovery of structural alterations in solid tumor oligodendroglioma by single molecule analysis

Background

Solid tumors present a panoply of genomic alterations, from single base changes to the gain or loss of entire chromosomes. Although aberrations at the two extremes of this spectrum are readily defined, comprehensive discernment of the complex and disperse mutational spectrum of cancer genomes remains a significant challenge for current genome analysis platforms. In this context, high throughput, single molecule platforms like Optical Mapping offer a unique perspective.

Results

Using measurements from large ensembles of individual DNA molecules, we have discovered genomic structural alterations in the solid tumor oligodendroglioma. Over a thousand structural variants were identified in each tumor sample, without any prior hypotheses, and often in genomic regions deemed intractable by other technologies. These findings were then validated by comprehensive comparisons to variants reported in external and internal databases, and by selected experimental corroborations. Alterations range in size from under 5 kb to hundreds of kilobases, and comprise insertions, deletions, inversions and compound events. Candidate mutations were scored at sub-genic resolution and unambiguously reveal structural details at aberrant loci.

Conclusions

The Optical Mapping system provides a rich description of the complex genomes of solid tumors, including sequence level aberrations, structural alterations and copy number variants that power generation of functional hypotheses for oligodendroglioma genetics.

Endosomolytic anionic polymer for the cytoplasmic delivery of siRNAs in localized in vivo applications

The use of small interfering RNAs (siRNAs) to down-regulate the expression of disease-associated proteins carries significant promise for the treatment of a variety of clinical disorders. One of the main barriers to the widespread clinical use of siRNAs, however, is their entrapment and degradation within the endolysosomal pathway of target cells. Here we report the trafficking and function of PP75, a non-toxic, biodegradable, lipid membrane disruptive anionic polymer composed of phenylalanine derivatized poly(L-lysine iso-phthalamide). PP75 is readily endocytosed by cells, safely permeabilizes endolysosomes in a pH dependent manner and facilitates the transfer of co-endocytosed materials directly into the cytoplasm. The covalent attachment of siRNAs to PP75 using disulfide linkages generates conjugates that effectively traffic siRNAs to the cytoplasm of target cells both in vitro and in vivo. In a subcutaneous malignant glioma tumor model, a locally delivered PP75-stathmin siRNA conjugate decreases stathmin expression in tumor cells and, in combination with the nitrosourea chemotherapy carmustine, is highly effective at inhibiting tumor growth. PP75 may be clinically useful for the local delivery of siRNAs, in particular for the treatment of solid tumors.

Stathmin 1: a protein with many tasks. New biomarker and potential target in cancer

Stathmin 1 (STMN1) is a critical protein involved in microtubule polymerization and is necessary for survival of cancer cells. This editorial describes the role of targeted therapeutics which disrupt STMN1 modulation and such effect on cancer survival.

Quantitative proteomic Isotope-Coded Protein Label (ICPL) analysis reveals alteration of several functional processes in the glioblastoma

Glioblastoma (GB), the most frequent primary tumor of the central nervous system, remains one of the most lethal human cancers despite intensive researches. Current paradigm in the study of GB has been focused on inter-patient variability and on trying to isolate new classification elements or prognostic factors. Here, using ICPL, a technique for protein relative quantification by mass spectrometry, we investigated protein expression between the four regions of GB on clinically relevant biopsies from 5 patients. We identified 584 non-redundant proteins and 31 proteins were found to be up-regulated in the tumor region compared to the peri-tumoral brain tissue, among which, 24 proteins belong to an interaction network linked to 4 biological processes. The core of this network is mainly constituted of interactions between beta-actin (ACTB) with heat shock proteins (HSP90AA1, HSPA8) and 14-3-3 proteins (YWHAZ, YWHAG, YWHAB). A cluster of three isoforms of the sodium pump α-subunit (ATP1A1, ATP1A2, ATP1A3) was also identified outside this network. The differential expression observed for ACTB and 14-3-3γ was further validated by western blot and/or immunohistochemistry. Our study confirms the identity of previously proposed molecular targets, highlights several functional processes altered in GB such as energy metabolism and synaptic transmission and could thus provide added value to new therapeutic trails.

The microtubule cytoskeleton is required for a G2 cell cycle delay in cancer cells lacking stathmin and p53

In several cancer cell lines, depleting the microtubule (MT)-destabilizing protein stathmin/oncoprotein18 leads to a G2 cell cycle delay and apoptosis. These phenotypes are observed only in synergy with low levels of p53, but the pathway(s) activated by stathmin depletion to delay the cell cycle are unknown. We found that stathmin depletion caused greater MT stability in synergy with loss of p53, measured by the levels of acetylated α-tubulin and the rate of centrosomal MT nucleation. Nocodazole or vinblastine-induced MT depolymerization abrogated the stathmin-depletion induced G2 delay, measured by the percentage of cells staining positive for several markers (TPX2, CDK1 with inhibitory phosphorylation), indicating that MTs are required to lengthen G2. Live cell imaging showed that stathmin depletion increased time in G2 without an impact on the duration of mitosis, indicating that the longer interphase duration is not simply a consequence of a previous slowed mitosis. In contrast, stabilization of MTs with paclitaxel (8 nM) slowed mitosis without lengthening the duration of interphase, demonstrating that increased MT stability alone is not sufficient to delay cells in G2.

Proteomics of gliomas: initial biomarker discovery and evolution of technology

Gliomas are a group of aggressive brain tumors that diffusely infiltrate adjacent brain tissues, rendering them largely incurable, even with multiple treatment modalities and agents. Mostly asymptomatic at early stages, they present in several subtypes with astrocytic or oligodendrocytic features and invariably progress to malignant forms. Gliomas are difficult to classify precisely because of interobserver variability during histopathologic grading. Identifying biological signatures of each glioma subtype through protein biomarker profiling of tumor or tumor-proximal fluids is therefore of high priority. Such profiling not only may provide clues regarding tumor classification but may identify clinical biomarkers and pathologic targets for the development of personalized treatments. In the past decade, differential proteomic profiling techniques have utilized tumor, cerebrospinal fluid, and plasma from glioma patients to identify the first candidate diagnostic, prognostic, predictive, and therapeutic response markers, highlighting the potential for glioma biomarker discovery. The number of markers identified, however, has been limited, their reproducibility between studies is unclear, and none have been validated for clinical use. Recent technological advancements in methodologies for high-throughput profiling, which provide easy access, rapid screening, low sample consumption, and accurate protein identification, are anticipated to accelerate brain tumor biomarker discovery. Reliable tools for biomarker verification forecast translation of the biomarkers into clinical diagnostics in the foreseeable future. Herein we update the reader on the recent trends and directions in glioma proteomics, including key findings and established and emerging technologies for analysis, together with challenges we are still facing in identifying and verifying potential glioma biomarkers.

Stathmin: a protein with many tasks. New biomarker and potential target in cancer

INTRODUCTION

Stathmin is a microtubule-destabilizing phosphoprotein, firstly identified as the downstream target of many signal transduction pathways. Several studies then indicated that stathmin is overexpressed in many types of human malignancies, thus deserving the name of Oncoprotein 18 (Op18). At molecular level, stathmin depolymerizes microtubules by either sequestering free tubulin dimers or directly inducing microtubule-catastrophe. A crucial role for stathmin in the control of mitosis has been proposed, since both its overexpression and its downregulation induce failure in the correct completion of cell division. Accordingly, stathmin is an important target of the main regulator of M phase, cyclin-dependent kinase 1.

AREAS COVERED

Recent evidences support a role for stathmin in the regulation of cell growth and motility, both in vitro and in vivo, and indicate its involvement in advanced, invasive and metastatic cancer more than in primary tumors.

EXPERT OPINION

Many studies suggest that high stathmin expression levels in cancer negatively influence the response to microtubule-targeting drugs. These notions together with the fact that stathmin is expressed at very low levels in most adult tissues strongly support the use of stathmin as marker of prognosis and as target for novel anti-tumoral and anti-metastatic therapies.

Neurological surgery at the National Institutes of Health

The Surgical Neurology Branch (SNB) in the intramural program of the National Institute of Neurological Disorders and Stroke at the National Institutes of Health has been a unique setting for academic neurosurgery for nearly 60 years. Every patient evaluated and treated in the SNB is enrolled in a clinical research protocol, which underscores a singular focus on advancing neurosurgical research and patient care. Since the inception of the SNB, this research effort has been driven by dedicated clinician-investigators and basic scientists including Maitland Baldwin, Igor Klatzo, John M. Van Buren, Ayub K. Ommaya, Richard J. Youle, and Edward H. Oldfield. These and other SNB investigators have studied and advanced treatment of a number of neuropathologic processes, including delineation of differences between cytotoxic and vasogenic edema, head injury, Cushing disease, the effects of vascular endothelial growth factor in nervous system tissues, tumor suppressor syndromes, the pathophysiology of syringomyelia, mechanisms underlying cerebral vasospasm after subarachnoid hemorrhage, spinal arteriovenous malformations, mechanisms of cell death, and drug delivery. Currently, SNB efforts are focused on central nervous system drug delivery, the natural history of familial tumor syndromes, functional neurosurgery, epilepsy, vasospasm, and development of chemotherapeutics for malignant glioma. Throughout its history, the SNB has also been dedicated to training neurosurgeon clinician-investigators; 23 previous fellows/staff have become chairs of their respective neurosurgical departments. Recently, the commitment to training future neurosurgeon clinician-investigators has been further defined with the development of a residency-training program in neurological surgery approved in 2010.

Toxicogenomic analysis of exposure to TCDD, PCB126 and PCB153: identification of genomic biomarkers of exposure to AhR ligands

Background

Two year cancer bioassays conducted by the National Toxicology Program have shown chronic exposure to dioxin-like compounds (DLCs) to lead to the development of both neoplastic and non-neoplastic lesions in the hepatic tissue of female Sprague Dawley rats. Most, if not all, of the hepatotoxic effects induced by DLC's are believed to involve the binding and activation of the transcription factor, the aryl hydrocarbon receptor (AhR). Toxicogenomics was implemented to identify genomic responses that may be contributing to the development of hepatotoxicity in rats.

Results

Through comparative analysis of time-course microarray data, unique hepatic gene expression signatures were identified for the DLCs, 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) (100 ng/kg/day) and 3,3',4,4',5-pentachlorobiphenyl (PCB126) (1000 ng/kg/day) and the non-DLC 2,2',4,4',5,5',-hexachlorobiphenyl (PCB153) (1000 μg/kg/day). A common time independent signature of 41 AhR genomic biomarkers was identified which exhibited at least a 2-fold change in expression following subchronic (13-wk) and chronic (52-wk) p.o. exposure to TCDD and PCB126, but not the non DLC, PCB153. Real time qPCR analysis validated that 30 of these genes also exhibited at least a 2-fold change in hepatic expression at 24 hr following a single exposure to TCDD (5 μg/kg, po). Phenotypic anchoring was conducted which identified forty-six genes that were differently expressed both following chronic p.o. exposure to DLCs and in previously reported studies of cholangiocarcinoma or hepatocellular adenoma.

Conclusions

Together these analyses provide a comprehensive description of the genomic responses which occur in rat hepatic tissue with exposure to AhR ligands and will help to isolate those genomic responses which are contributing to the hepatotoxicity observed with exposure to DLCs. In addition, the time independent gene expression signature of the AhR ligands may assist in identifying other agents with the potential to elicit dioxin-like hepatotoxic responses.

Oligodendroglial tumors: diagnostic and molecular pathology

Oligodendroglial tumors, which encompass pure oligodendroglioma and mixed oligoastrocytoma, represent the second most common glioma in adults after glioblastoma. They remain controversial neoplasms in the realm of surgical neuropathology. The early recognition of their more favorable prognosis and responsiveness to treatment when compared with diffusely infiltrating astrocytomas has influenced the pathologic diagnostic interpretation, and resulted in a pervasive interobserver variability. The more recent finding of an increased frequency of 1p/19q deletion in these tumors by cytogenetic analysis, and the association of this molecular abnormality with a better prognosis has greatly impacted the field of neuro-oncology. In this review, we focus on important histopathologic aspects in the evaluation of oligodendroglial tumors, key differential diagnoses, and highlight particular clinical and molecular characteristics, as well as current diagnostic and conceptual controversies.

Prognosis of oligodendroglial tumor with ring enhancement showing central necrotic portion

Oligodendroglial tumors sometimes show heterogeneous ring enhancement with a central necrotic portion. We aimed to reveal the prognosis of such tumors based on such radiologic findings and compare them to other prognostic factors. Participants were 32 patients with oligodendroglioma (17 oligodendrogliomas, 15 anaplastic oligodendrogliomas) who underwent surgery from 2004 to 2008. We investigated tumor radiologic findings, locations, calcification, whether localized or diffuse type, and enhancement patterns. Of other prognostic factors, we analyzed age, sex, pathology, extent of removal, adjuvant therapy, genetic change in 1p and 19q, and MGMT methylation status. We checked for genetic abnormality in 1p and 19q using the FISH method. To investigate MGMT methylation, we performed methylation-specific PCR (MSP). Mean follow-up duration was 3.2 years. Median age was 42.4 years, and the male:female ratio was 21:11. Out of 17 oligodendrogliomas, 14 (82.4%) showed combined 1p/19q deletion, and 14 (82.4%), methylated MGMT. Among 15 anaplastic oligodendrogliomas, there were 7 (46.6%) with combined 1p/19q deletion and 11 (73.3%) with methylated MGMT. The 4-year recurrence-free survival and overall survival were 77.6 and 100% in oligodendrogliomas and 59.1 and 71.6% in anaplastic oligodendrogliomas, respectively. On univariate analysis, radiologic variable of ring enhancement pattern was statistically significant related with recurrence-free survival (P = 0.003). Variables such as sex (P = 0.03), combined 1p/19q loss (P = 0.04), tumor location (P = 0.02), and anaplastic pathology (P = 0.04) were significantly correlated with overall survival. Cox's regression model revealed that ring enhancement pattern was associated with frequent recurrence (ring enhancement, hazard ratio = 8.281, P = 0.04), and these showed 1p deletion only. Anaplastic oligodendrogliomas with ring enhancement like glioblastomas and without combined 1p/19q loss should receive close follow-up after treatment because of frequent recurrences.

Enhanced target gene knockdown by a bifunctional shRNA: a novel approach of RNA interference

RNA interference (RNAi) is a natural cellular regulatory process that inhibits gene expression by transcriptional, post-transcriptional and translational mechanisms. Synthetic approaches that emulate this process (small interfering RNA (siRNA), short hairpin RNA (shRNA)) have been shown to be similarly effective in this regard. We developed a novel 'bifunctional' RNAi strategy, which further optimizes target gene knockdown outcome. A bifunctional construct (bi-sh-STMN1) was generated against Stathmin1, a critical tubulin modulator that is overexpressed in human cancers. The bifunctional construct is postulated to concurrently repress the translation of the target mRNA (cleavage-independent, mRNA sequestration and degradation) and degrade (through RNase H-like cleavage) post-transcriptional mRNA through cleavage-dependent activities. Bi-sh-STMN1 showed enhanced potency and durability in parallel comparisons with conventional shRNA and siRNAs targeting the same sequence. Enhanced STMN1 protein knockdown by bi-sh-STMN1 was accompanied by target site cleavage at the mRNA level showed by the rapid amplification of complementary DNA ends (RACE) assay. Bi-sh-STMN1 also showed knockdown kinetics at the mRNA level consistent with its multieffector silencing mechanisms. The bifunctional shRNA is a highly effective and advantageous approach mediating RNAi at concentrations significantly lower than conventional shRNA or siRNA. These results support further evaluations.

Stathmin1 overexpression associated with polyploidy, tumor-cell invasion, early recurrence, and poor prognosis in human hepatoma

Frequent intrahepatic metastasis causes early tumor recurrence and dismaying prognosis of human hepatocellular carcinoma (HCC). We recently identified overexpression of stathmin1 (STMN1) in human HCC. This study was designed to elucidate the clinical and biological significance of overexpression of STMN1 in HCC. Expression of STMN1 was conducted by quantitative reverse transcription-polymerase chain reaction and immunoblotting assays on 58 pairs of HCC and para-tumor liver tissues from patients with HCC along with normal liver tissues as the controls. Association of STMN1 overexpression with tumor recurrence and prognosis was investigated by Kaplan-Meier cumulative survival and Cox Regression analyses. Roles of STMN1 in cell cycle, cell motility, and invasion were determined by in vitro assays. STMN1 overexpression in hepatoma was strongly associated with local invasion (P = 0.031), early recurrence (P = 0.002), and poor prognosis (P = 0.005), and was an independent indicator for tumor recurrence (P = 0.0045). STMN1 overexpression further identified subgroups of HCC patients with higher tumor recurrence and worse prognosis among HCC patients with early tumor stage (T1) or intermediate histological grades (G2 and G3), both of whom represent the majority of HCC patients receiving primary curative hepatectomy. Silencing STMN1 expression via RNA interference suppressed invasion activity, while ectopic expression of STMN1 enhanced cell invasion and caused polyploidy of cells. In conclusion, STMN1 overexpression could predict early tumor recurrence and poor prognosis, particularly at early stage of hepatoma. Overexpression of STMN1 promoted polyploidy formation, tumor-cell invasion, and intrahepatic metastasis, suggesting that STMN1 can be a target for anti-cancer therapy of human hepatoma.

Glioma proteomics: status and perspectives

High grade gliomas are the most common brain tumors in adults and their malignant nature makes them the fourth biggest cause of cancer death. Major efforts in neuro-oncology research are needed to reach similar progress in treatment efficacy as that achieved for other cancers in recent years. In addition to the urgent need to identify novel effective drug targets against malignant gliomas, the search for glioma biomarkers and grade specific protein signatures will provide a much needed contribution to diagnosis, prognosis, treatment decision and assessment of treatment response. Over the past years glioma proteomics has been attempted at different levels, including proteome analysis of patient biopsies and bodily fluids, of glioma cell lines and animal models. Here we provide an extensive review of the outcome of these studies in terms of protein identifications (protein numbers and regulated proteins), with an emphasis on the methods used and the limitations of the studies with regard to biomarker discovery. This is followed by a perspective on novel technologies and on the potential future contribution of proteomics in a broad sense to understanding glioma biology.

Genetic signature of adult gliomas and correlation with MRI features

In recent years the amount of information concerning the genetics and the biology of gliomas, and particularly of glioblastoma multiforme, increased steadily. Such an increase has been paralleled by the technological progress of MRI. The merging of these scientific areas, as summarized in this review, is helping the stratification of glioma patients for clinical trials and their clinical follow-up. Although available therapeutic options appear limited in number, it is likely that in the next 5 years, both as a consequence of the increased knowledge due to genomic sequencing of hundreds of glioblastoma specimens and to continuous improvements of MRI, new perspectives will be available for these patients, with a sizable impact on their prognosis.

High rate of deletion of chromosomes 1p and 19q in insular oligodendroglial tumors

It has been reported recently that oligodendroglial tumors arising in the insula rarely harbor co-deletions of chromosomes 1p and 19q, a molecular signature which is associated with a good prognosis and increased responsiveness to radiation and chemotherapy compared with tumors in which 1p and/or 19q is intact. In the context of this claim, we analyzed a series of insular oligodendroglial tumors in order to determine the frequency of 1p/19q co-deletion in tumors arising in this region. We identified 14 insular cases operated on after 2003 in which testing for losses of 1p and 19q was performed. Of these cases, co-deletion of 1p and 19q occurred in eight (57%). Four (50%) of eight oligodendrogliomas and four (67%) of six oligoastrocytomas demonstrated 1p/19q co-deletions. Seven of the eight tumors with co-deletion of 1p/19q were WHO grade II gliomas. There were no statistical differences between tumors with 1p/19q co-deletion compared to those with 1p and/or 19q intact in terms of age, preoperative KPS, presenting symptoms, left versus right lateralization, tumor location (purely insular versus extension into frontal or temporal lobe), preoperative tumor size. There was a preponderance of females in the co-deletion group, and a greater average extent of resection. In contradistinction to previous reports, loss of 1p/19q occurs commonly in insular oligodendroglial tumors. With respect to 1p/19q, insular gliomas do not appear to be distinct from gliomas arising elsewhere in the brain.

A cohort study of STMN1 expression in colorectal cancer: body mass index and prognosis

OBJECTIVES

STMN1 (stathmin or oncoprotein-18) destabilizes microtubules and reorganizes cytoskeleton, and functions in cell cycle progression and cell migration. STMN1 activity is influenced by p53, p27, and the PI3K/AKT pathway. However, its prognostic significance in colon cancer is uncertain.

METHODS

Utilizing 546 colorectal cancers (stage I-IV) from two independent prospective cohort studies (the Nurses' Health Study and Health Professionals Follow-up Study), STMN1 expression was detected in 297 (54%) tumors by immunohistochemistry. Cox proportional hazard models computed hazard ratios (HRs) of mortality, adjusted for clinical and tumoral features, including microsatellite instability (MSI), CpG island methylation phenotype (CIMP), LINE-1 hypomethylation, KRAS, BRAF, PIK3CA, p53, p21, p27, cyclin D1, beta-catenin, fatty acid synthase, FASN, and COX-2.

RESULTS

Five-year colorectal cancer-specific survival was 78% in STMN1-positive patients and 76% in STMN1-negative patients (log-rank P=0.30). STMN1-positivity was not significantly associated with cancer-specific survival in univariate analysis with HR of 0.82 (95% confidence interval (CI), 0.59-1.14), which became significant in multivariate analysis (adjusted HR=0.60; 95% CI, 0.41-0.87; P=0.0078). Notably, the prognostic effect of obesity (body mass index, BMI> or =30 kg/m2) significantly differed by STMN1 (P(interaction)=0.005). Obesity was associated with high cancer-specific mortality among STMN1-positive patients (adjusted HR=2.36; 95% CI, 1.18-4.69), whereas obesity was not associated with high mortality among STMN1-negative patients (adjusted HR=0.51; 95% CI, 0.24-1.07).

CONCLUSIONS

STMN1 overexpression in colorectal cancer is independently associated with improved survival. The adverse prognostic effect of obesity was limited to patients with STMN1-positive tumors. Our findings suggest the presence of a tumor (STMN1)-host (BMI) interaction that potentially determines clinical outcome.

Coordinated expression of stathmin family members by far upstream sequence element-binding protein-1 increases motility in non-small cell lung cancer

Dynamic instability of the microtubule network modulates processes such as cell division and motility, as well as cellular morphology. Overexpression of the microtubule-destabilizing phosphoprotein stathmin is frequent in human malignancies and represents a promising therapeutic target. Although stathmin inhibition gives rise to antineoplastic effects, additional and functionally redundant microtubule-interacting proteins may attenuate the efficiency of this therapeutic approach. We have systematically analyzed the expression and potential protumorigenic effects of stathmin family members in human non-small cell lung cancer (NSCLC). Both stathmin and stathmin-like 3 (SCLIP) were overexpressed in adenocarcinoma as well as squamous cell carcinoma (SCC) tissues and induced tumor cell proliferation, migration, and matrix invasion in respective cell lines. Accordingly, reduced stathmin and SCLIP levels affected cell morphology and were associated with a less malignant phenotype. Combined inhibition of both factors caused additive effects on tumor cell motility, indicating partial functional redundancy. Because stathmin and SCLIP expression significantly correlated in NSCLC tissues, we searched for common upstream regulators and identified the far upstream sequence element-binding protein-1 (FBP-1) as a pivotal inducer of several stathmin family members. Our results indicate that the coordinated overexpression of microtubule-destabilizing factors by FBP-1 is a critical step to facilitate microtubule dynamics and subsequently increases proliferation and motility of tumor cells.

Stathmin 1: a novel therapeutic target for anticancer activity

Stathmin 1 (STMN1), also known as p17, p18, p19, 19K, metablastin, oncoprotein 18, LAP 18 and Op18, is a 19 kDa cytosolic protein. It was the first discovered member of a family of phylogenetically related microtubule-destabilizing phosphoproteins critically involved in the construction and function of the mitotic spindle. A threshold level of STMN1 is required for orderly progression through mitosis in a variety of cell types. STMN1 is overexpressed across a broad range of human malignancies (leukemia, lymphoma, neuroblastoma; ovarian, prostatic, breast and lung cancers and mesothelioma). It is also upregulated in normally proliferating cell lines but is only rarely upregulated in nonproliferating cell lines with the exception of neurons, anterior pituitary cells and glial cells. Its expression is also upregulated in hepatocytes during regeneration and in lymphoid cells when they are signaled to proliferate. In this review, we summarize available data as rationale for the therapeutic manipulation of STMN1 in cancer patients.

Pharmacotherapy for adults with tumors of the central nervous system

Tumors of the adult central nervous system are among the most common and most chemoresistant neoplasms. Malignant tumors of the brain and spinal cord collectively account for approximately 1.3% of all cancers and 2.2% of all cancer-related deaths. Novel pharmacological approaches to nervous system tumors are urgently needed. This review presents the current approaches and challenges to successful pharmacotherapy of adults with malignant tumors of the central nervous system and discusses novel approaches aimed at overcoming these challenges.

Nitrosoureas inhibit the stathmin-mediated migration and invasion of malignant glioma cells

Malignant gliomas are the most common primary intrinsic brain tumors and are highly lethal. The widespread migration and invasion of neoplastic cells from the initial site of tumor formation into the surrounding brain render these lesions refractory to definitive surgical treatment. Stathmin, a microtubule-destabilizing protein that mediates cell cycle progression, can also regulate directed cell movement. Nitrosoureas, traditionally viewed as DNA alkylating agents, can also covalently modify proteins such as stathmin. We therefore sought to establish a role for stathmin in malignant glioma cell motility, migration, and invasion and determine the effects of nitrosoureas on these cell movement-related processes. Scratch wound-healing recovery, Boyden chamber migration, Matrigel invasion, and organotypic slice invasion assays were performed before and after the down-regulation of cellular stathmin levels and in the absence and presence of sublethal nitrosourea ([1-(2-chloroethyl)-3-cyclohexyl-l-nitrosourea]; CCNU) concentrations. We show that decreases in stathmin expression lead to significant decreases in malignant glioma cell motility, migration, and invasion. CCNU, at a concentration of 10 micromol/L, causes similar significant decreases, even in the absence of any effects on cell viability. The direct inhibition of stathmin by CCNU is likely a contributing factor. These findings suggest that the inhibition of stathmin expression and function may be useful in limiting the spread of malignant gliomas within the brain, and that nitrosoureas may have therapeutic benefits in addition to their antiproliferative effects.

Covalent modification of stathmin by CCNU determined by FTMS analysis of modified proteins and tryptic peptides

Chemical modification of proteins is often carried out to generate protein-small molecule conjugates for various applications. The high resolution and mass accuracy of a Fourier transform mass spectrometer is particularly useful for assessing the extent or sites of covalent modifications. As protein-small molecule reactions often produce products with variable numbers of the compound incorporated at different sites, a direct mass analysis of the reaction products at times yields mass spectra hard to interpret. Chromatographic separation at protein level could reduce the complexity of a sample, thus allowing more accurate mass spectrometric analysis. In this report, we demonstrate the utility of reversed-phase protein chromatography and FT-ICR mass spectrometry in analyzing CCNU (lomustine, 1-(2-chloroethyl)-3-cyclohexyl-1-nitroso-urea, MW: 233.7Da) modification of stathmin. With this combined approach, we determined the stoichiometry as well as sites of CCNU incorporation into the protein, demonstrating differential reactivity of several lysyl residues to CCNU alkylation.

Molecular genetic markers as predictors of response to chemotherapy in gliomas

PURPOSE OF REVIEW

This review summarizes recent studies on applications of molecular markers such as chromosome 1p/19q codeletion and MGMT status in the treatment of glioma.

RECENT FINDINGS

Prospective trials confirmed that 1p/19q codeletion represents a strong and independent favourable prognostic factor in anaplastic oligodendroglial tumours. Other retrospective studies have suggested that 1p/19q loss is also predictive of chemosensitivity to alkylating agents (nitrosoureas and temozolomide) in low-grade gliomas. Recent reports have provided evidence that 1p and 19q deletions are mediated by unbalanced translocation. The targeted genes remain to be identified, however. Promoter methylation of MGMT gene silencing has been shown to predict benefit from chemotherapy in glioblastoma. MGMT promoter methylation and low expression of MGMT-encoded protein are frequently observed in low-grade gliomas and anaplastic oligodendroglial tumours. In such tumours, however, preliminary studies have yielded contradictory results on the predictive value of MGMT status regarding objective response to chemotherapy and correlation with 1p/19q deletion.

SUMMARY

There is mounting evidence that 1p/19q deletion and MGMT inactivation are relevant prognostic markers and predictors of chemosensitivity in gliomas. Although such markers remain to be formally validated by ongoing and planned prospective trials, it is likely that they will soon become essential for optimizing treatment decisions.