Urinary expression of let-7c cluster as non-invasive tool to assess the risk of disease progression in patients with high grade non-muscle invasive bladder Cancer: a pilot study.

BACKGROUND: High grade non-muscle-invasive bladder cancer (HG-NMIBC) is a heterogeneous disease with variable risk of progression. Urinary microRNAs are promising biomarkers for BC detection and surveillance. Let-7c-5p miRNA, clustered with miR-99a-5p and -125b-5p, is deregulated in cancer, including BC. The aim of this study is to evaluate urinary let-7c cluster expression in Ta/T1 HG-NMIBC patients and its impact on progression-free survival (PFS). METHODS: Quantitative Real-Time-Polymerase-Chain-Reaction (qRT-PCR) was used to analyze the let-7c cluster expression in 57 urine and 49 neoplastic paired tissue samples prospectively collected from transurethral resection (TUR) HG-NMIBC patients. Twenty urine and 10 bladder tissue samples were collected and analyzed as normal controls. QRT-PCR was also used to detect intra-/extra-cellular let-7c cluster in BC cells. Receiver Operating Characteristic (ROC) curves were used to identify urinary miRNAs cut-off values predicting T-stage and PFS. Uni/multivariable Cox regression was performed to identify predictors of PFS. A nomogram predicting progression risk and a decision curve analysis (DCA) were performed. RESULTS: Urinary let-7c was significantly up-regulated in patients compared with controls, while the whole cluster was down-regulated in tumor tissues. Supporting these findings, in vitro comparison of extra-/intra-cellular ratios of cluster levels between BC cells, showed a higher ratio for let-7c in HG-NMIBC versus low-grade cells. Urinary let-7c cluster expression was increased in higher T-stage and was an independent predictor of progression. Lower EORTC-score and downregulation of urinary cluster were predictors of higher PFS on univariable Cox regression, while on multivariable analysis only cluster expression was an independent progression predictor. On DCA, a benefit was evident for patients with a PFS probability > 20%. CONCLUSIONS: Urinary let-7c cluster evaluation may improve prognosis, identifying patients at risk of progression and addressing early radical treatment.

The clinical and prognostic value of miR-9 gene expression in Tunisian patients with bladder cancer.

There is a major need for the identification of biomarkers, which are able to guide personalized therapy for bladder cancer, in particular after resection of the primary tumor. Specifically, miR-9 upregulation has been preliminarily associated with a more aggressive phenotype of bladder cancer, namely muscle-invasive bladder cancer (MIBC) or high-grade non-muscle-invasive bladder cancer (HG NMIBC). In order to explore the potential utility of miR-9 as a biomarker in bladder cancer, we have investigated its expression pattern in a sample of Tunisian patients who have undergone primary resection. This is a retrospective study performed on BCa samples from 90 patients (44 specimens of HG NMIBC, 23 specimens of LG NMIBC, and 23 specimens of MIBC). Ten samples from the non-tumoral zone of cystectomy specimens were used as controls. For each specimen, we measured miR-9 expression and correlated it with the clinical characteristics of the patients. Overall, miR-9 was overexpressed in MIBC compared to NMIBC specimens (median fold change [FC]: - 8.89 vs 1.41, p = 0.001). Similarly, miR-9 expression was significantly different in LG NMIBC, HG NMIBC and MIBC subgroups (median FC: 0.68, 2.14 and 8.89, respectively; p = 0.001). ROC analysis showed that miR-9 expression pattern could be used as potential biomarker for distinguishing NMIBC subgroups: indeed miR-9 expression is relatively low in LG NMIBC and high in HG NMIBC. The thresholds are estimated at 0.063 and 21.597, respectively. Moreover, miR-9 was associated with a higher risk of progression. This study suggests the clinical value of miR-9 as a prognostic factor in bladder cancer after tumor resection. Should the prognostic ability of miR-9 be confirmed in larger studies, also on different ethnic groups, it would be useful to investigate whether urine sampling-which is easier to perform, less invasive and less costly-can provide the same results as analysis on surgical specimens.

The prognostic significance of positive peritoneal cytology in endometrial cancer and its correlations with L1-CAM biomarker.

BACKGROUND: The aim of this study was to evaluate the prognostic role of positive peritoneal cytology (PPC) in a cohort of patients with endometrial cancer (EC). The secondary objective was to correlate the PPC and the expression of L1CAM in a group of patients with recurrence endometrial disease. METHODS: All women diagnosed with EC and who performed a peritoneal cytology at "Regina Elena" National Cancer Institute of Rome from 2001 to 2013 were included in the study. Patients were divided into two groups according to positivity at peritoneal cytology. Moreover, patients with a recurrence disease and whose a tissue microarray (TMA) tumor sample was available underwent a L1CAM analysis. RESULTS: Seven hundred sixty six patients underwent to EC staging in our Institute: 696 (90.8%) with negative and 70 (9.2%) with positive cytology. Five-year recurrence rate was higher in women with PPC (46.9% vs 18.4%, p = 0 < 0.0001) and, in particular, distant recurrence (86.7% vs 53.4%, p = 0.03). Moreover, we found an interesting pattern of recurrence disease in the group of early stage of EC with NPC and positive L1CAM. CONCLUSIONS: Our results support the data that PPC may be a potential prognostic factor in early EC, due to its significant association with other risk factors and its significant influence on survival. Our findings confirm the need for large studies that point out the role of PPC and new prognostic factors, including biomarkers as L1CAM.

Endometrial cancer prognosis correlates with the expression of L1CAM and miR34a biomarkers.

BACKGROUND: Patients with endometrial cancer (EC) and presumably with good prognosis may develop a recurrence indicating that the classification of this tumor is still not definitive and that new markers are needed to identify a subgroup at risk of relapse. The cell adhesion molecule L1CAM is highly expressed in several human carcinomas and has recently been described as a new marker for endometrial and ovarian carcinomas. The aim of this study was to determine the relevance of L1CAM in recurrent EC. METHODS: In this work we have analyzed, by immunohistochemical and RT-qPCR analysis, the expression of L1CAM in a cohort of 113 endometrial cancers at different stages, which 50% have relapsed. As a predictor of good outcome, the tumors were also analyzed for the expression of miR-34a, a post-transcriptional regulator of L1CAM. RESULTS: Among metastatic EC, the highest levels (60%) and the median level (24%) of L1CAM in tumors correlate with the progression, suggesting that the expression of this molecule is linked to the tumor component most involved in metastatic processes. We also found an inverse correlation between miR-34a and L1CAM protein expression, suggesting that miR-34a is a positive prognostic marker of EC. CONCLUSIONS: Our results demonstrate the expression of L1CAM and miR-34a in EC as prognostic factors that identify subgroup of patients at high risk of recurrence suggesting for them more aggressive schedules of treatment.

Correction to: Serum DNA integrity index as a potential molecular biomarker in endometrial cancer.

CORRECTION: In the publication of this article [1], there is an error in the first sentence of the Acknowledgements section.

Serum DNA integrity index as a potential molecular biomarker in endometrial cancer.

BACKGROUND: Circulating cell-free DNA (cfDNA) and its integrity index may represent a rapid and noninvasive "liquid biopsy" biomarker, which gives important complementary information for diagnosis, prognosis, and treatment stratification in cancer patients. The aim of our study was to evaluate the possible role of cfDNA and its integrity index as a complementary tool for endometrial cancer (EC) management. METHODS: Alu-quantitative real-time PCR (qPCR) analysis wasprformed on 60 serum samples from preoperative EC patients randomly recruited. Both cfDNA content and DNA integrity index were measured by qPCR-Alu115 (representing total cfDNA) and qPCR-Alu247 (corresponding to high molecular weight DNA) and correlated with clinicopathologic characteristics. Lymphovascular space invasion (LVSI) was detected by hematoxylin and eosin staining. In case of doubt, LVSI status was further evaluate by immunohistochemistry using anti-CD31 and anti-CD34 antibodies. RESULTS: Total cfDNA content significantly increases in high grade EC. A significant decrease of DNA integrity index was detected in the subset of hypertensive and obese high grade EC. Serum DNA integrity was higher in samples with LVSI. The ordinal regression analysis predicted a significant correlation between decreased integrity index values and hypertension specifically in tumors presenting LVSI. CONCLUSIONS: Our study supports the utility of serum DNA integrity index as a noninvasive molecular biomarker in EC. We show that a correlation analysis between cfDNA quantitative and qualitative content and clinicopathologic features, such as blood pressure level, body mass index (BMI) and LVSI status, could represent a potential predictive signature to help stratification approaches in EC.

Doxorubicin upregulates CXCR4 via miR-200c/ZEB1-dependent mechanism in human cardiac mesenchymal progenitor cells.

Doxorubicin (DOXO) treatment is limited by its cardiotoxicity, since it causes cardiac-progenitor-cell depletion. Although the cardioprotective role of the stromal cell-derived factor-1/C-X-C chemokine receptor type 4 (SDF1/CXCR4) axis is well established, its involvement during DOXO-induced cardiotoxicity has never been investigated. We showed that in a mouse model of DOXO-induced cardiomyopathy, CXCR4+ cells were increased in response to DOXO, mainly in human cardiac mesenchymal progenitor cells (CmPC), a subpopulation with regenerative potential. Our in vitro results showed a CXCR4 induction after 24 h of DOXO exposure in CmPC. SDF1 administration protected from DOXO-induced cell death and promoted CmPC migration. CXCR4 promoter analysis revealed zinc finger E-box binding homeobox 1 (ZEB1) binding sites. Upon DOXO treatment, ZEB1 binding decreased and RNA-polymerase-II increased, suggesting a DOXO-mediated transcriptional increase in CXCR4. Indeed, DOXO induced the upregulation of miR-200c, that directly targets ZEB1. SDF1 administration in DOXO-treated mice partially reverted the adverse remodeling, decreasing left ventricular (LV) end diastolic volume, LV ejection fraction and LV anterior wall thickness in diastole, recovering LV end systolic pressure and reducing±dP/dt. Moreover, in vivo administration of SDF1 partially reverted DOXO-induced miR-200c and p53 protein upregulation in mouse hearts. In addition, downmodulation of ZEB1 mRNA and protein by DOXO was significantly increased by SDF1. In keeping, p21 mRNA, that is induced by p53 and inhibited by ZEB1, is induced by DOXO treatment and is decreased by SDF1 administration. This study showed new players of the DOXO-induced cardiotoxicity, that can be exploited to ameliorate DOXO-associated cardiomyopathy.

Circulating cell-free DNA content as blood based biomarker in endometrial cancer.

BACKGROUND: Altered circulating cell-free DNA (cfDNA) levels are related to cancer development and aggressiveness. Up to now, very few studies have been performed for evaluating cfDNA content in endometrial cancer (EC). METHODS: First, we measured cfDNA release in blood serum of EC cancer patients collected before surgery and before the beginning of any treatment by SYBR Gold assay and correlated it with tumor aggressiveness. We also assessed the relative mitochondrial cell-free DNA (cfmtDNA) content by qRT-PCR. Next, we correlated cfDNA levels with BMI, age, hypertension and inflammation markers. RESULTS: CfDNA levels are higher in G2 and G3 compared with G1 EC sera. A significant modulation of cfDNA content was detected in sera from patients with BMI>30 compared with those with BMI<30. We observed a further and significant alteration in cfDNA level in hypertensive patients with G2-G3, but not in G1 EC. Analysis of preoperative neutrophil-to-lymphocyte (NLR) and monocyte-to-lymphocyte (MLR) ratios suggests a contribution of the host response in the altered cfDNA levels in EC. CONCLUSIONS: Our data indicate that assessment of total and mitochondrial cfDNA levels in blood sera and the relative NLR and MLR in blood obtained from preoperative patients may help clinical management and prognosis in EC.

Prognostic role of NF-YA splicing isoforms and Lamin A status in low grade endometrial cancer.

Although most cases of low grade (G1) endometrial cancer (EC) do not behave aggressively, in rare instances, can progress in a highly aggressive manner. In this study we analyzed formalin-fixed, paraffin-embedded (FFPE) EC tissues to find novel clinical and biological features to help diagnosis and treatment of G1 ECs s in order to better stratify patient risk of recurrence. A retrospective cohort of FFPE specimens from patients with EC (n=87) and benign tissue specimens (NE) from patients who underwent a hysterectomy to treat other benign disease (n = 13) were collected. Total RNA and proteins were extracted and analyzed, respectively, by quantitative PCR and western blotting. NF-YAs is expressed and lamin A is down-modulated in all high grade (G2 and G3) ECs. In G1 ECs, NF-YAs expression is heterogeneous being expressed only in a subset of these tumours. Interestingly, the G1 ECs that express NF-YAs display low levels of lamin A similar to those present in G2 and G3 ECs. Of note, this pattern of NF-YAs and lamin A expression correlates with tumor aggressiveness assessed by comparative analysis with estrogen receptor (ER) status and epithelial-mesenchymal transition (EMT) markers thus suggesting its potential role as biomarker of tumour aggressiveness in G1 EC. In all grade ECs, lamin A is strongly downmodulated, being its expression inversely correlated with tumor aggressiveness and its loss of expression. We identified NF-YAs and lamin A expression levels as novel potential biomarkers useful to identify G1 ECs patients with risk of recurrence.

The laminA/NF-Y protein complex reveals an unknown transcriptional mechanism on cell proliferation.

Lamin A is a component of the nuclear matrix that also controls proliferation by largely unknown mechanisms. NF-Y is a ubiquitous protein involved in cell proliferation composed of three subunits (-YA -YB -YC) all required for the DNA binding and transactivation activity. To get clues on new NF-Y partner(s) we performed a mass spectrometry screening of proteins that co-precipitate with the regulatory subunit of the complex, NF-YA. By this screening we identified lamin A as a novel putative NF-Y interactor. Co-immunoprecipitation experiments and confocal analysis confirmed the interaction between the two endogenous proteins. Interestingly, this association occurs on euchromatin regions, too. ChIP experiments demonstrate lamin A enrichment in several promoter regions of cell cycle related genes in a NF-Y dependent manner. Gain and loss of function experiments reveal that lamin A counteracts NF-Y transcriptional activity. Taking advantage of a recently generated transgenic reporter mouse, called MITO-Luc, in which an NF-Y-dependent promoter controls luciferase expression, we demonstrate that lamin A counteracts NF-Y transcriptional activity not only in culture cells but also in living animals. Altogether, our data demonstrate the occurrence of lamin A/NF-Y interaction and suggest a possible role of this protein complex in regulation of NF-Y function in cell proliferation.

A restricted signature of serum miRNAs distinguishes glioblastoma from lower grade gliomas.

BACKGROUND: Malignant gliomas are the most common primary brain tumors in adults and challenging cancers for diagnosis and treatment. They remain a disease for which non-invasive, diagnostic and/or prognostic novel biomarkers are highly desirable. Altered microRNA (miRNA) profiles have been observed in tumor tissues and biological fluids. To date only a small set of circulating/serum miRNA is found to be differentially expressed in brain tumors compared to normal controls. Here a restricted signature of circulating/serum miRNA including miR-15b*,-23a, -99a, -125b, -133a, -150*, -197, -340, -497, -548b-5p and let-7c were investigated as potential non-invasive biomarkers in the diagnosis of glioma patients. METHODS: Serum and tissues miRNAs expression in patients with brain cancers (n = 30) and healthy controls (n = 15) were detected by quantitative real-time polymerase chain reaction (qRT-PCR). Relative expression was calculated using the comparative Ct method. Statistical significance (p ≤ 0,05) was determined using the Mann-Whitney rank sum and Fisher's exact test. Diagnostic accuracy of miRNAs in distinguishing glioblastoma multiforme (GBM) from lower grade cancer was assessed by the Receiver Operating Characteristic (ROC) curve analysis. To validate the role of the identified miRNAs in cancer a comprehensive literature search was conducted using PubMed, Web of Science (Core Collection) and Scopus databases. RESULTS: We observed a decrease of miR-497 and miR-125b serum levels depending on tumor stages with reduced level in GBM than lower grade tumors. The ROC curve analysis distinguishing GBM from lower grade cases yielded an area under the curve (AUC) of 0.87 (95 % confidence interval (CI) = 0.712-1) and of 0.75 (95 % CI = 0.533-0.967) for miR-497 and -125b, respectively. GBM patients are more likely to show a miR-497 and -125b down-regulation than the lower grade group (p = 0.002 and p = 0.024, respectively). These results were subsequently compared with evidence from 19 studies included in the final systematic review. CONCLUSIONS: Although multiple biomarkers are currently leveraged in the clinic to detect specific cancer types, no such standard blood biomolecules are used as yet in gliomas. Our data suggest that serum miR-497 and -125b could be a novel diagnostic markers with good perspectives for future clinical applications in patients with glioma.

Hypoxia-inducible factor 1-α induces miR-210 in normoxic differentiating myoblasts.

MicroRNA-210 (miR-210) induction is a virtually constant feature of the hypoxic response in both normal and transformed cells, regulating several key aspects of cardiovascular diseases and cancer. We found that miR-210 was induced in normoxic myoblasts upon myogenic differentiation both in vitro and in vivo. miR-210 transcription was activated in an hypoxia-inducible factor 1-α (Hif1a)-dependent manner, and chromatin immunoprecipitation experiments show that Hif1a bound to the miR-210 promoter only in differentiated myotubes. Accordingly, luciferase reporter assays demonstrated the functional relevance of the Hif1a binding site for miR-210 promoter activation in differentiating myoblasts. To investigate the functional relevance of increased miR-210 levels in differentiated myofibers, we blocked miR-210 with complementary locked nucleic acid oligonucleotides (anti-miR-210). We found that C2C12 myoblast cell line differentiation was largely unaffected by anti-miR-210. Likewise, miR-210 inhibition did not affect skeletal muscle regeneration following cardiotoxin damage. However, we found that miR-210 blockade greatly increased myotube sensitivity to oxidative stress and mitochondrial dysfunction. In conclusion, miR-210 is induced in normoxic myofibers, playing a cytoprotective role.

Characterisation of a multimeric protein complex associated with ERp57 within the nucleus in paclitaxel-sensitive and -resistant epithelial ovarian cancer cells: the involvement of specific conformational states of beta-actin.

Ovarian cancer is the second most frequently diagnosed malignancy of the reproductive system and is the leading cause of gynecological cancer mortality. Although the majority of advanced ovarian carcinomas initially respond successfully to taxane-based chemotherapy, resistance to chemotherapy remains the primary factor accounting for the low 5-year survival in this patient population. Recent data obtained by our group demonstrate that the disulphide isomerase ERp57 is strongly modulated in paclitaxel resistance suggesting that it may represent a chemoresistance biomarker in ovarian cancer. In the present study, we characterise a nuclear multimeric complex where ERp57 is associated with protein species involved in cell division and gene expression, as Nucleolin, Nucleophosmin, Vimentin, Aurora kinase C and beta-actin. In particular, we show that the occurrence of the interaction of nuclear ERp57 with beta-actin is associated with paclitaxel resistance and that specific actin conformations modulate this complex. We propose the involvement of the nuclear ERp57 complex in mechanisms associated with chromosome segregation in which specific conformational states of actin play a role in the pathway involved in paclitaxel resistance.

Glycoproteomics of paclitaxel resistance in human epithelial ovarian cancer cell lines: towards the identification of putative biomarkers.

Glycosylation, one of the most common post translational modifications (PTMs) of proteins, is often associated with carcinogenesis and tumor malignancy. Ovarian cancer is the sixth cause of cancer-related death in Western countries. Currently, it is treated by debulking surgery followed by chemotherapy based on paclitaxel, alone or in combination with other drugs. However, chemoresistance represents a major obstacle to positive clinical outcome. We used two approaches, Multiplexed Proteomics (MP) technology and Multilectin Affinity Chromatography (MAC) to characterize the glycoproteome of the human ovarian cancer cell line A2780 and its paclitaxel resistant counterpart A2780TC1. Furthermore proteins were separated by traditional 2DE or DIGE and identified by MS (MALDI TOF or LC MS/MS). Seventy glycoproteins were successfully identified in ovarian cancer cells and 10 were found to be differentially expressed between sensitive and resistant cell lines. We focused on four glycoproteins (tumor rejection antigen (gp96) 1, triose phosphate isomerase, palmitoyl-protein thioesterase 1 precursor and ER-associated DNAJ) which were remarkably upregulated in A2780TC1 compared to A2780 cell line and which may represent biomarkers for paclitaxel resistance in ovarian cancer.

Paclitaxel directly binds to Bcl-2 and functionally mimics activity of Nur77.

We reported previously that Bcl-2 is paradoxically down-regulated in paclitaxel-resistant cancer cells. We reveal here that paclitaxel directly targets Bcl-2 in the loop domain, thereby facilitating the initiation of apoptosis. Molecular modeling revealed an extraordinary similarity between the paclitaxel binding sites in Bcl-2 and beta-tubulin, leading us to speculate that paclitaxel could be mimetic of an endogenous peptide ligand, which binds both proteins. We tested the hypothesis that paclitaxel mimics Nur77, which, like paclitaxel, changes the function of Bcl-2. This premise was confirmed by Nur77 interacting with both paclitaxel targets (Bcl-2 and beta-tubulin) and a peptide sequence mimicking the Nur77 structural region, thus reproducing the paclitaxel-like effects of tubulin polymerization and opening the permeability transition pore channel in mitochondria. This discovery could help in the development of novel anticancer agents with nontaxane skeleton as well as in identifying the clinical subsets responsive to paclitaxel-based therapy.

Comparative proteomic analysis of paclitaxel sensitive A2780 epithelial ovarian cancer cell line and its resistant counterpart A2780TC1 by 2D-DIGE: the role of ERp57.

Epithelial ovarian cancer is the leading cause of gynecological cancer mortality. Despite good response to surgery and initial chemotherapy, chemoresistance occurrence represents a major obstacle to a successful therapy. To better understand biological mechanisms at the basis of paclitaxel resistance, a comparative proteomic approach based on DIGE coupled with mass spectrometry (MALDI-TOF and LC-MS/MS) was applied to the human epithelial ovarian cancer cell lines A2780 and its paclitaxel resistant counterpart A2780TC1. Most of the differentially expressed proteins between the two cell lines belong to the class of stress response (29%), metabolism (21%), and cell cycle and apoptosis (17%). We focused on proteins which were most strongly modulated by paclitaxel resistance and in particular on the disulphide isomerase ERp57, which may represent a chemoresistance biomarker. ERp57 was found to interact with class III beta-tubulin (TUBB3), involved in paclitaxel resistance in ovarian and other cancers. Moreover, we demonstrated a novel localization of this protein in cytoskeleton and described that ERp57/TUBB3 interaction occurs also in the nuclear compartment and in association with a multimeric complex formed by nucleolin, nucleophosmin, hnRNPK, and mortalin. Our data suggest that ERp57 plays an important role in chemoresistance mechanisms in ovarian cancer by modulating the attachment of microtubules to chromosomes following paclitaxel treatment through its interaction with TUBB3.

A proteomic approach to paclitaxel chemoresistance in ovarian cancer cell lines.

Ovarian cancer is the leading cause of gynaecological cancer mortality. Paclitaxel is used in the first line treatment of ovarian cancer, but acquired resistance represents the most important clinical problem and a major obstacle to a successful therapy. Several mechanisms have been implicated in paclitaxel resistance, however this process has not yet been fully explained. To better understand molecular resistance mechanisms, a comparative proteomic approach was undertaken on the human epithelial ovarian cancer cell lines A2780 (paclitaxel sensitive), A2780TC1 and OVCAR3 (acquired and inherently resistant). Proteins associated with chemoresistance process were identified by DIGE coupled with mass spectrometry (MALDI-TOF and LC-MS/MS). Out of the 172 differentially expressed proteins in pairwise comparisons among the three cell lines, 151 were identified and grouped into ten main functional classes. Most of the proteins were related to the category of stress response (24%), metabolism (22%), protein biosynthesis (15%) and cell cycle and apoptosis (11%), suggesting that alterations of those processes might be involved in paclitaxel resistance mechanisms. This is the first direct proteomic comparison of paclitaxel sensitive and resistant ovarian cancer cells and may be useful for further studies of resistance mechanisms and screening of resistance biomarkers for the development of tailored therapeutic strategies.

Proteomic characterization of cytoskeletal and mitochondrial class III beta-tubulin.

Class III beta-tubulin (TUBB3) has been discovered as a marker of drug resistance in human cancer. To get insights into the mechanisms by which this protein is involved in drug resistance, we analyzed TUBB3 in a panel of drug-sensitive and drug-resistant cell lines. We identified two main different isoforms of TUBB3 having a specific electrophoretic profile. We showed that the apparently higher molecular weight isoform is glycosylated and phosphorylated and it is localized in the cytoskeleton. The apparently lower molecular weight isoform is instead found exclusively in mitochondria. We observed that levels of phosphorylation and glycosylation of TUBB3 are associated with the resistant phenotype and compartmentalization into cytoskeleton. By two-dimensional nonreduced/reduced SDS-PAGE analysis, we also found that TUBB3 protein in vivo forms protein complexes through intermolecular disulfide bridges. Through TUBB3 immunoprecipitation, we isolated protein species able to interact with TUBB3. Following trypsin digestion, these proteins were characterized by mass spectrometry analysis. Functional analysis revealed that these proteins are involved in adaptation to oxidative stress and glucose deprivation, thereby suggesting that TUBB3 is a survival factor able to directly contribute to drug resistance. Moreover, glycosylation of TUBB3 could represent an attractive pathway whose inhibition could hamper cytoskeletal compartmentalization and TUBB3 function.

Hypoxia induces class III beta-tubulin gene expression by HIF-1alpha binding to its 3' flanking region.

Class III beta-tubulin (TUBB3) overexpression represents a major mechanism of drug resistance to microtubule interacting agents such as taxanes and Vinca alkaloids. Here, we tested hypoxia as a possible inducer of TUBB3. The effects of hypoxia on TUBB3 expression were monitored at mRNA and protein level in A2780, in its paclitaxel-resistant counterpart (TC1) and in HeLa cells. Hypoxia was a strong inducer of TUBB3 in A2780, but not in TC1 and HeLa cells. In A2780 HIF-1alpha was knocked down using RNA interference and TUBB3 expression was assessed in normoxia and hypoxia. The silencing abolished the hypoxia-dependent increase of TUBB3, thereby demonstrating that HIF-1alpha mediates TUBB3 induction in hypoxia. To investigate this phenomenon, the 5' flanking region of human TUBB3 was cloned upstream GFP as a reporter. This region contained the promoter gene, but activity of the reporter was unaffected by hypoxia. Thus, we looked at the 3' flanking region and, at +168 nucleotides from the stop codon, an HIF-1alpha binding site was proven to be active in hypoxia, using a construct in which the site was cloned downstream GFP as reporter gene. Deletion of the site in the construct abolished GFP enhancement upon hypoxia. Chromatin immunoprecipitation revealed the engagement by HIF-1alpha of this site in hypoxia. Methylation analysis of this 3' enhancer showed that it was free of methylation in 70% of cells in A2780, while in less than 16% in both TC1 and HeLa cells, thereby suggesting that TUBB3 increase upon hypoxia is abolished through methylation of the 3' enhancer.

From plasma membrane to cytoskeleton: a novel function for semaphorin 6A.

Class III beta-tubulin (TUBB3) overexpression has been reported in ovary, lung, breast, and gastric cancer patients. Currently, no clinical drugs are available for a specific targeting of TUBB3, whereas the investigational drug IDN5390 specifically interacts with TUBB3. To gain insight into the pathways leading to TUBB3 up-regulation, we did a human genome microarray analysis in A2780 cells made resistant to IDN5390 to identify selected pathways specifically disrupted in resistant cells. Using this approach, we discovered that semaphorin 6A (SEMA6A) is down-regulated not only in IDN5390-resistant cells but also in cells made resistant to cisplatin, topotecan, and doxorubicin, whereas no changes were noticed in paclitaxel- and gemcitabine-resistant cells. Acute treatment with IDN5390 was able to down-regulate SEMA6A in cells unselected for drug resistance. TUBB3 expression was assessed in A2780 clones with stable overexpression of SEMA6A and in a panel of clones in which silencing of the protein was obtained. Quantitative PCR was then used to check the modulation of SEMA6A as well as to assess the expression of TUBB3. TUBB3 was increased (median value, 5.4) and reduced (median value, 0.47) in cells with overexpression and silencing of SEMA6A, respectively. Thus, the findings indicate a correlation between the expression of SEMA6A and TUBB3. Then, we found that a form of 83 kDa of SEMA6A is expressed in the cytoskeleton in association with beta-actin. These findings suggest for SEMA6A a novel function in the cytoskeleton and a role in modulating tubulin isotype composition and microtubule dynamics.