Src/lck inhibitor dasatinib reversibly switches off cytokine release and T cell cytotoxicity following stimulation with T cell bispecific antibodies

Background

T cell engagers are bispecific antibodies recognizing, with one moiety, the CD3ε chain of the T cell receptor and, with the other moiety, specific tumor surface antigens. Crosslinking of CD3 upon simultaneous binding to tumor antigens triggers T cell activation, proliferation and cytokine release, leading to tumor cell killing. Treatment with T cell engagers can be associated with safety liabilities due to on-target on-tumor, on-target off-tumor cytotoxic activity and cytokine release syndrome (CRS). Tyrosine kinases such as SRC, LCK or ZAP70 are involved in downstream signaling pathways after engagement of the T cell receptor and blocking these kinases might serve to abrogate T cell activation when required (online supplemental material 1). Dasatinib was previously identified as a potent kinase inhibitor that switches off CAR T cell functionality.

Methods

Using an in vitro model of target cell killing by human peripheral blood mononuclear cells, we assessed the effects of dasatinib combined with 2+1 T cell bispecific antibodies (TCBs) including CEA-TCB, CD19-TCB or HLA-A2 WT1-TCB on T cell activation, proliferation and target cell killing measured by flow cytometry and cytokine release measured by Luminex. To determine the effective dose of dasatinib, the Incucyte system was used to monitor the kinetics of TCB-mediated target cell killing in the presence of escalating concentrations of dasatinib. Last, the effects of dasatinib were evaluated in vivo in humanized NSG mice co-treated with CD19-TCB. The count of CD20⁺ blood B cells was used as a readout of efficacy of TCB-mediated killing and cytokine levels were measured in the serum.

Results

Dasatinib concentrations above 50 nM prevented cytokine release and switched off-target cell killing, which were subsequently restored on removal of dasatinib. In addition, dasatinib prevented CD19-TCB-mediated B cell depletion in humanized NSG mice. These data confirm that dasatinib can act as a rapid and reversible on/off switch for activated T cells at pharmacologically relevant doses as they are applied in patients according to the label.

Conclusion

Taken together, we provide evidence for the use of dasatinib as a pharmacological on/off switch to mitigate off-tumor toxicities or CRS by T cell bispecific antibodies.

Glofitamab, a Novel, Bivalent CD20-Targeting T-Cell-Engaging Bispecific Antibody, Induces Durable Complete Remissions in Relapsed or Refractory B-Cell Lymphoma: A Phase I Trial

PURPOSE

Glofitamab is a T-cell-engaging bispecific antibody possessing a novel 2:1 structure with bivalency for CD20 on B cells and monovalency for CD3 on T cells. This phase I study evaluated glofitamab in relapsed or refractory (R/R) B-cell non-Hodgkin lymphoma (B-NHL). Data for single-agent glofitamab, with obinutuzumab pretreatment (Gpt) to reduce toxicity, are presented.

METHODS

Seven days before the first dose of glofitamab (0.005-30 mg), all patients received 1,000 mg Gpt. Dose-escalation steps were determined using a Bayesian continuous reassessment method with overdose control. Primary end points were safety, pharmacokinetics, and the maximum tolerated dose of glofitamab.

RESULTS

Following initial single-patient cohorts, 171 patients were treated within conventional multipatient cohorts and received at least one dose of glofitamab. This trial included heavily pretreated patients with R/R B-NHL; most were refractory to prior therapy (155; 90.6%) and had received a median of three prior therapies. One hundred and twenty-seven patients (74.3%) had diffuse large B-cell lymphoma, transformed follicular lymphoma, or other aggressive histology, and the remainder had indolent lymphoma subtypes. Five (2.9%) patients withdrew from treatment because of adverse events. Cytokine release syndrome occurred in 86 of 171 (50.3%) patients (grade 3 or 4: 3.5%); two (1.2%) patients experienced grade 3, transient immune effector cell-associated neurotoxicity syndrome-like symptoms. The overall response rate was 53.8% (complete response [CR], 36.8%) among all doses and 65.7% (CR, 57.1%) in those dosed at the recommended phase II dose. Of 63 patients with CR, 53 (84.1%) have ongoing CR with a maximum of 27.4 months observation.

CONCLUSION

In patients with predominantly refractory, aggressive B-NHL, glofitamab showed favorable activity with frequent and durable CRs and a predictable and manageable safety profile.

Abstract 3127: MiR-BART9 is a prognostic biomarker associated with PD-1 expression in colon cancer patients

Background:

Epstein-Barr Virus (EBV) is widely expressed in the population in a latent stage. During cancer progression, antiviral immunity is compromised by the same mechanisms leading to suppression of anticancer immunity.

This study was aimed at developing the expression of miR-BART as biomarkers to select patients at risk of fast progression for a defect of the antiviral/anticancer immunity.

Methods:

We first analyzed the expression of EBV-miRNAs in a panel of 438 colon cancer (CC) patients of the TCGA dataset. Analysis was conducted using level 1 miRNA-seq and level 3 RNA-seq available on the same patients.

In order to confirm the results, we tested the expression of miR-BART9 in an additional set of 271 CC patients using spectral imaging and quantitative fluorescent immunohistochemistry (PD-1 and PD-L1 antigens at the protein level and miR-BART9 using a specific designed ISH probe).

In order to increase the clinical applicability of our findings, we also developed a qPCR test to analyze the expression of miR-BART9 in serum of colon cancer patients.

Results:

In the analysis of 438 CC patients of the TCGA dataset, expression of miR-BART9 was found in 78 patients (18%). Levels of miR-BART9 were prognostic of poor outcome in a multivariate Cox model including age and stage (HR = 2.8, CI 1.6-4.7, p<0.0001). In patients positive for miR-BART9 we also noticed a significant higher expression of PD-1, CD3 but not PD-L1 at the gene level. These results suggest that the expression of miR-BART9 is linked to a T cell infiltrate in the cancer tissue capable to induce a potent suppression of anticancer and antiviral immunity.

In order to confirm this hypothesis, we performed spectral imaging in an additional set of 271 CC patients. Expression of miR-BART9 was found in 32 (12%) patients with a prevalent stromal pattern. Also in this case expression of miR-BART9 was associated with poor outcome in Cox-multivariate analysis including age and stage (HR = 2.5, CI 1.6-3.4, p<0.001). Expression of miR-BART9 was again significantly associated with a PD-1 positive T-cell infiltrate.

Based on these results, we have designed a qPCR test to analyze the expression of miR-BART9 in serum using an EBV-infected B lymphoma cell line (Raji) as positive control. The assay was employed for monitoring miR-BART9 expression in serum from CC patients (n = 89) and healthy controls (n = 95). Human miR-486 and miR-17 were used as positive controls.MiR-BART9 expression was found in 33 (37%) of CC patients and only in 5 (5%) of the 95 healthy controls.

Conclusions: Our results reveal that expression of miR-BART9 is associated with aggressive CC. Patients featuring reactivation of latent EBV-infection have also expression of PD-1+ T cells, which will impact both anticancer and antiviral immunity. The expression of miR-BART9 can be detected also in serum and may serve to identify the right timing to treat CC patients with PD-1/PD-L1 inhibitors in order to restore an effective anticancer and antiviral immunity.

Citation Format: Marisa Mariani, Deep Pandya, Mirko Andreoli, Shiquan He, Manuela Spennato, Cristiano Ferlini. MiR-BART9 is a prognostic biomarker associated with PD-1 expression in colon cancer patients. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 3127.

Role and prognostic significance of the epithelial-mesenchymal transition factor ZEB2 in ovarian cancer

ZEB2 is a key factor in epithelial-mesenchymal transition (EMT), a program controlling cell migration in embryonic development and adult tissue homeostasis. We demonstrated a role of ZEB2 in migration and anchorage-independent cell growth in ovarian cancer, as shown by ZEB2 silencing. We found that the RNA-binding protein HuR bound the 3′UTR of ZEB2 mRNA, acting as a positive regulator of ZEB2 protein expression. In Hey ovarian cell line, HuR silencing decreased ZEB2 and ZEB1 nuclear expression and impaired migration. In hypoglycemic conditions ZEB2 expression decreased, along with ZEB1, vimentin and cytoplasmic HuR, and a reduced cellular migration ability was observed. Analysis of ZEB2 and HuR expression in ovarian cancers revealed that nuclear ZEB2 is localized in tumor leading edge and co-localizes with cytoplasmic HuR. In a series of 143 ovarian cancer patients high expression of ZEB2 mRNA significantly correlated with a poor prognosis in term of both overall survival and progression- free survival. Moreover, at immunohistochemical evaluation, we found that prognostic significance of ZEB2 protein relies on its nuclear expression and co-localization with cytoplasmic HuR. In conclusion our findings indicated that nuclear ZEB2 may enhance progression of EMT transition and acquisition of an aggressive phenotype in ovarian cancer.

From Protein Communication to Drug Discovery

The majority of functionally important biological processes are regulated by allosteric communication within individual proteins and across protein complexes. The proteins controlling these communication networks respond to changes in the cellular environment by switching between different conformational states. Targeting the interface residues mediating these processes through the rational identification of molecules modulating or mimicking their effects holds great therapeutic potential. Protein-protein interactions (PPIs) have shown to have a high degree of plasticity since they occur through small regions, called hot spots, which are included in binding surfaces or in binding clefts of the proteins and are characterized by a high degree of complementarity. This prompted several researchers to compare the protein structure to human grammar proposing terms like "protein language". The decoding of this language represent a new paradigm not only to clarify the dynamics of many biological processes but also to improve the opportunities in drug discovery. In this review, we try to give an overview on intra-molecular and inter-molecular protein communication mechanisms describing the protein interaction domains (PIDs) and short linear motifs (SLiMs), which delineate the authentic syntactic and semantic units in a protein. Moreover, we illustrate some novel approaches performed on natural compounds and on synthetic derivatives aimed at developing new classes of potential drugs able to interfere with intra-molecular and inter-molecular protein communication.

Epstein-Barr Virus MicroRNA Expression Increases Aggressiveness of Solid Malignancies

The Cancer Genome Atlas (TCGA) microRNA (miRNA) initiative has revealed a pivotal role for miRNAs in cancer. Utilizing the TCGA raw data, we performed the first mapping of viral miRNA sequences within cancer and adjacent normal tissues. Results were integrated with TCGA RNA-seq to link the expression of viral miRNAs to the phenotype. Using clinical data and viral miRNA mapping results we also performed outcome analysis. Three lines of evidence lend credence to an active role of viral miRNAs in solid malignancies. First, expression of viral miRNA is consistently higher in cancerous compared to adjacent noncancerous tissues. Second, viral miRNA expression is associated with significantly worse clinical outcome among patients with early stage malignancy. These patients are also featured by increased expression of PD1/PD-L1, a pathway implicated in tumors escaping immune destruction. Finally, a particular cluster of EBV-miRNA (miR-BART2, miR-BART4, miR-BART5, miR-BART18, and miR-BART22) is associated with expression of cytokines known to inhibit host response to cancer. Quantification of specific viral miRNAs may help identify patients who are at risk of poor outcome. These patients may be candidates for novel therapeutic strategies incorporating antiviral agents and/or inhibitors of the PD-1/PD-L1 pathway.

Abstract 3994: Herpes virus microRNA expression and significance in serous ovarian cancer

Serous ovarian cancer (SEOC) is the deadliest gynecologic malignancy. MicroRNAs (miRNAs) are a class of small noncoding RNAs which regulate gene expression and protein translation. MiRNAs are also encoded by viruses with the intent of regulating their own genes and those of the infected cells. This is the first study assessing viral miRNAs in SEOC. MiRNAs sequencing data from 487 SEOC patients were downloaded from the TCGA website and analyzed through in-house sequencing pipeline. To cross-validate TCGA analysis, we measured the expression of miR-H25 by quantitative immunofluorescence in an additional cohort of 161 SEOC patients. Gene, miRNA expression, and cytotoxicity assay were performed on multiple ovarian cancer cell lines transfected with miR-H25 and miR-BART7. Outcome analysis was performed using multivariate Cox and Kaplan-Meier method. Viral miRNAs are more expressed in SEOC than in normal tissues. Moreover, Herpetic viral miRNAs (miR-BART7 from EBV and miR-H25 from HSV-2) are significant and predictive biomarkers of outcome in multivariate Cox analysis. MiR-BART7 correlates with resistance to first line chemotherapy and early death, whereas miR-H25 appears to impart a protective effect and long term survival. Integrated analysis of gene and viral miRNAs expression suggests that miR-BART7 induces directly cisplatin-resistance, while miR-H25 alters RNA processing and affects the expression of noxious human miRNAs such as miR-143. This is the first investigation linking viral miRNA expression to ovarian cancer outcome. Viral miRNAs can be useful to develop biomarkers for early diagnosis and as a potential therapeutic tool to reduce SEOC lethality.

Citation Format: Deep Pandya, Marisa Mariani, Mark McHugh, Mirko Andreoli, Steven Sieber, Shiquan He, Candice Dowell-Martino, Paul Fiedler, Giovanni Scambia, Cristiano Ferlini. Herpes virus microRNA expression and significance in serous ovarian cancer. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 3994. doi:10.1158/1538-7445.AM2015-3994

Abstract 4327: Nek6 and Hif-1α cooperate with the cytoskeletal gateway of drug resistance to drive outcome in serous ovarian cancer

Hypoxia selects the most aggressive and drug-resistant clones in solid malignancies. One of the pivotal transcription factors induced by hypoxia is Hif-1α. However, in serous ovarian cancer (SEOC), Hif-1α expression is not a prognostic biomarker. This study aims to assess the hypothesis that the serine-threonine kinase Nek6 functions as a downstream effector cooperating with Hif-1α in driving ovarian cancer aggressiveness.

Nek6 was overexpressed and Hif-1α was silenced in A2780 cells. Nek6 was also stably silenced in Hey cells. The dependence of Nek6 expression on Hif-1α was assayed as a function of hypoxic growth conditions. Nek6 interaction with the cytoskeletal gateway of drug resistance was investigated with far western blot. The co-expression of NEK6, HIF1A, TUBB3 and GBP1 transcripts was quantified with qPCR in two cohorts of SEOC patients (346 locally treated patients and 344 from the TCGA dataset).

Nek6 expression is induced by hypoxia in a Hif-1α dependent fashion. Nek6 directly interacts with GBP-1, thus being a component of the cytoskeletal gateway of drug resistance. Nek6 overexpression increases and silencing decreases the anchorage-independent growth of cultured cells. In SEOC patients, NEK6 expression is significantly correlated with HIF1A. Co-expression of NEK6, HIF1A, TUBB3 and GBP1 transcripts identifies a subset of SEOC patients characterized by poor outcome and drug resistance.

This study demonstrates the functional relevance of Nek6 in the context of the adaptive response to hypoxia in SEOC. This finding may help identify a sub-population of patients at high risk of relapse to standard first-line chemotherapy.

Citation Format: Marta De Donato, Mara Fanelli, Marisa Mariani, Giuseppina Raspaglio, Deep Pandya, Shiquan He, Paul Fiedler, Marco Petrillo, Giovanni Scambia, Cristiano Ferlini. Nek6 and Hif-1α cooperate with the cytoskeletal gateway of drug resistance to drive outcome in serous ovarian cancer. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 4327. doi:10.1158/1538-7445.AM2015-4327

Defining "mutation" and "polymorphism" in the era of personal genomics

BACKGROUND

The growing advances in DNA sequencing tools have made analyzing the human genome cheaper and faster. While such analyses are intended to identify complex variants, related to disease susceptibility and efficacy of drug responses, they have blurred the definitions of mutation and polymorphism.

DISCUSSION

In the era of personal genomics, it is critical to establish clear guidelines regarding the use of a reference genome. Nowadays DNA variants are called as differences in comparison to a reference. In a sequencing project Single Nucleotide Polymorphisms (SNPs) and DNA mutations are defined as DNA variants detectable in >1 % or <1 % of the population, respectively. The alternative use of the two terms mutation or polymorphism for the same event (a difference as compared with a reference) can lead to problems of classification. These problems can impact the accuracy of the interpretation and the functional relationship between a disease state and a genomic sequence. We propose to solve this nomenclature dilemma by defining mutations as DNA variants obtained in a paired sequencing project including the germline DNA of the same individual as a reference. Moreover, the term mutation should be accompanied by a qualifying prefix indicating whether the mutation occurs only in somatic cells (somatic mutation) or also in the germline (germline mutation). We believe this distinction in definition will help avoid confusion among researchers and support the practice of sequencing the germline and somatic tissues in parallel to classify the DNA variants thus defined as mutations.

Nek6 and Hif-1α cooperate with the cytoskeletal gateway of drug resistance to drive outcome in serous ovarian cancer

Hypoxia selects the most aggressive and drug-resistant clones in solid malignancies. One of the pivotal transcription factors induced by hypoxia is Hif-1α. However, in serous ovarian cancer (SEOC), Hif-1α expression is not a prognostic biomarker. This study aims to assess the hypothesis that the serine-threonine kinase Nek6 functions as a downstream effector cooperating with Hif-1α in driving ovarian cancer aggressiveness. Nek6 was overexpressed and Hif-1α was silenced in A2780 cells. Nek6 was also stably silenced in Hey cells. The dependence of Nek6 expression on Hif-1α was assayed as a function of hypoxic growth conditions. Nek6 interaction with the cytoskeletal gateway of drug resistance was investigated with far western blot. The co-expression of NEK6, HIF1A, TUBB3 and GBP1 transcripts was quantified with qPCR in two cohorts of SEOC patients (346 locally treated patients and 344 from the TCGA dataset). Nek6 expression is induced by hypoxia in a Hif-1α dependent fashion. Nek6 directly interacts with GBP-1, thus being a component of the cytoskeletal gateway of drug resistance. Nek6 overexpression increases and silencing decreases the anchorage-independent growth of cultured cells. In SEOC patients, NEK6 expression is significantly correlated with HIF1A. Co-expression of NEK6, HIF1A, TUBB3 and GBP1 transcripts identifies a subset of SEOC patients characterized by poor outcome and drug resistance. This study demonstrates the functional relevance of Nek6 in the context of the adaptive response to hypoxia in SEOC. This finding may help identify a sub-population of patients at high risk of relapse to standard first-line chemotherapy.

HGF/c-Met axis drives cancer aggressiveness in the neo-adjuvant setting of ovarian cancer

Ovarian cancer is the most lethal gynecologic malignancy. Recently, NACT (Neo Adjuvant Chemotherapy) has been tested as alternative approach for the management of ovarian cancer patients. A biological predictor helpful in selecting patients for NACT would be desirable. This study was aimed at identifying actionable mechanisms of resistance to NACT. Expression of a panel of microRNAs was screened in a discovery set of 85 patients. Analysis of the potential targets was conducted in the same RNAs by calculating significant correlations between microRNAs and genes. Quantitative fluorescent immunohistochemistry was employed in a validation set of 109 patients. MiR-193a-5p was significantly overexpressed in the NACT setting. Analysis of its potential targets demonstrated that this microRNA is also significantly correlated with HGF and MET genes. Analysis of protein expression in samples taken before and after NACT demonstrated that both HGF and c-Met are increased after NACT. Patients who relapse shortly after NACT exhibited the highest relative basal expression of both HGF and c-Met, while the opposite phenomenon was observed in the best responders. Mir-193a-5p, HGF and c-Met expression may help select eligible patients for this modality of treatment. Moreover, inhibitors of this pathway may improve the efficacy of NACT.

Class III β-tubulin in normal and cancer tissues

Microtubules are polymeric structures composed of tubulin subunits. Each subunit consists of a heterodimer of α- and β-tubulin. At least seven β-tubulin isotypes, or classes, have been identified in human cells, and constitutive isotype expression appears to be tissue specific. Class III β-tubulin (βIII-tubulin) expression is normally confined to testes and tissues derived from neural cristae. However, its expression can be induced in other tissues, both normal and neoplastic, subjected to a toxic microenvironment characterized by hypoxia and poor nutrient supply. In this review, we will summarize the mechanisms underlying βIII-tubulin constitutive and induced expression. We will also illustrate its capacity to serve as a biomarker of neural commitment in normal tissues and as a pure prognostic biomarker in cancer patients.

Herpes virus microRNA expression and significance in serous ovarian cancer

Serous ovarian cancer (SEOC) is the deadliest gynecologic malignancy. MicroRNAs (miRNAs) are a class of small noncoding RNAs which regulate gene expression and protein translation. MiRNAs are also encoded by viruses with the intent of regulating their own genes and those of the infected cells. This is the first study assessing viral miRNAs in SEOC. MiRNAs sequencing data from 487 SEOC patients were downloaded from the TCGA website and analyzed through in-house sequencing pipeline. To cross-validate TCGA analysis, we measured the expression of miR-H25 by quantitative immunofluorescence in an additional cohort of 161 SEOC patients. Gene, miRNA expression, and cytotoxicity assay were performed on multiple ovarian cancer cell lines transfected with miR-H25 and miR-BART7. Outcome analysis was performed using multivariate Cox and Kaplan-Meier method. Viral miRNAs are more expressed in SEOC than in normal tissues. Moreover, Herpetic viral miRNAs (miR-BART7 from EBV and miR-H25 from HSV-2) are significant and predictive biomarkers of outcome in multivariate Cox analysis. MiR-BART7 correlates with resistance to first line chemotherapy and early death, whereas miR-H25 appears to impart a protective effect and long term survival. Integrated analysis of gene and viral miRNAs expression suggests that miR-BART7 induces directly cisplatin-resistance, while miR-H25 alters RNA processing and affects the expression of noxious human miRNAs such as miR-143. This is the first investigation linking viral miRNA expression to ovarian cancer outcome. Viral miRNAs can be useful to develop biomarkers for early diagnosis and as a potential therapeutic tool to reduce SEOC lethality.

Abstract 3725: HGF/c-Met axis drives cancer aggressiveness in the neo-adjuvant setting of ovarian cancer

Background: Ovarian cancer is the most lethal gynecologic malignancy. Recently, NACT has been clinically tested as alternative approach for the management of ovarian cancer patients. A biological predictor helpful in selecting patients for NACT would be desirable. Indeed, chemotherapy has a strong impact in modifying the biology of tumor and rendering it more aggressive. This study was aimed at identifying actionable mechanisms of resistance to NACT.

Methods: Expression of a panel of microRNAs was screened in a discovery set of 85 patients. Analysis of the potential targets was conducted in the same RNAs by calculating significant correlations between microRNAs and genes. Quantitative fluorescent immunohistochemistry was employed in a validation set of 109 patients. Pre and post-NACT specimens were analyzed in multiple cores of tumor from formalin fixed paraffin embedded material (FFPE).

Results: MiR-193a-5p was significantly overexpressed in the NACT setting. Analysis of its potential targets demonstrated that this microRNA is also significantly correlated with the expression levels of HGF and MET genes. Analysis of protein expression in samples taken before and after NACT demonstrated that both HGF and c-Met are increased after NACT. Patients who relapse shortly after NACT exhibited the highest relative basal expression of both HGF and c-Met, while the opposite phenomenon was observed in the best responders.

Conclusion: These findings demonstrate that NACT refractory patients express activation of the HGF/c-Met pathway. HGF/c-Met expression may help select eligible patients for this modality of treatment. Moreover, inhibitors of this pathway may improve the efficacy of NACT.

Citation Format: Marisa Mariani, Mark McHugh, Marco Petrillo, Steven Sieber, Shiquan He, Mirko Andreoli, Paul Fiedler, Giovanni Scambia, Shohreh Shahabi, Cristiano Ferlini. HGF/c-Met axis drives cancer aggressiveness in the neo-adjuvant setting of ovarian cancer. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 3725. doi:10.1158/1538-7445.AM2014-3725

Abstract 916: A multidimensional analysis of predictive biomarkers in colorectal cancer

Background: CRC cancer is one of the deadliest diseases in Western countries. In order to develop predictive biomarkers for CRC (colorectal cancer) aggressiveness, we analyzed retrospectively 267 CRC patients via a novel, multidimensional biomarker platform.

Methods: Using nanofluidic technology for qPCR analysis and quantitative fluorescent immunohistochemistry for protein analysis, we assessed 33 microRNAs, 124 mRNAs and 9 protein antigens. Analysis was conducted in each single dimension (microRNA, gene or protein) using both the multivariate Cox model and Kaplan-Meier method. Thereafter, we simplified the censored survival data into binary response data (aggressive vs. non aggressive cancer). Subsequently, we combined the data into multidimensional scores using inverse sliced regression for sufficient dimension reduction. Accuracy was assessed using the Area under the Curve (AUC) and the receiver operating characteristic (ROC) method.

Results: Single dimension analysis led to the discovery of individual factors that were significant predictors of outcome. These included seven specific microRNAs, four genes, and one protein. When these factors were quantified individually as predictors of aggressive disease, the highest demonstrable area under the curve (AUC) was 0.68. By contrast, when all results from single dimensions were combined into multidimensional biomarkers, AUCs were dramatically increased with values approaching and even exceeding 0.9. Conclusions: Single dimension analysis generates statistically significant predictors, but their predictive strengths are suboptimal for clinical utility. A novel, multidimensional approach overcomes these deficiencies. Newly derived multidimensional biomarkers have the potential to meaningfully guide the selection of therapeutic agents for individual patients while elucidating molecular mechanisms driving disease progression.

Citation Format: Marisa Mariani, Shiquan He, Mark McHugh, Mirko Andreoli, Deep Pandya, Steven Sieber, Zheyang Wu, Paul Fiedler, Shohreh Shahabi, Cristiano Ferlini. A multidimensional analysis of predictive biomarkers in colorectal cancer. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 916. doi:10.1158/1538-7445.AM2014-916

Identification of the first inhibitor of the GBP1:PIM1 interaction. Implications for the development of a new class of anticancer agents against paclitaxel resistant cancer cells

Class III β-tubulin plays a prominent role in the development of drug resistance to paclitaxel by allowing the incorporation of the GBP1 GTPase into microtubules. Once in the cytoskeleton, GBP1 binds to prosurvival kinases such as PIM1 and initiates a signaling pathway that induces resistance to paclitaxel. Therefore, the inhibition of the GBP1:PIM1 interaction could potentially revert resistance to paclitaxel. A panel of 44 4-azapodophyllotoxin derivatives was screened in the NCI-60 cell panel. The result is that 31 are active and the comparative analysis demonstrated specific activity in paclitaxel-resistant cells. Using surface plasmon resonance, we were able to prove that NSC756093 is a potent in vitro inhibitor of the GBP1:PIM1 interaction and that this property is maintained in vivo in ovarian cancer cells resistant to paclitaxel. Through bioinformatics, molecular modeling, and mutagenesis studies, we identified the putative NSC756093 binding site at the interface between the helical and the LG domain of GBP1. According to our results by binding to this site, the NSC756093 compound is able to stabilize a conformation of GBP1 not suitable for binding to PIM1.

GTP is an allosteric modulator of the interaction between the guanylate-binding protein 1 and the prosurvival kinase PIM1

GBP1 and PIM1 are known to interact with a molar ratio 1:1. GBP1:PIM1 binding initiates a signaling pathway that induces resistance to common chemotherapeutics such as paclitaxel. Since GBP1 is a large GTPase which undergoes conformational changes in a nucleotide-dependent manner, we investigated the effect of GTP/GDP binding on GBP1:PIM1 interaction by using computational and biological studies. It resulted that only GTP decreases the formation of the GBP1:PIM1 complex through an allosteric mechanism, putting the bases for the identification of new compounds potentially able to revert resistance to paclitaxel.

Abstract 1957: MiR-200c can mediate either poor or good outcome in ovarian cancer depending on HuR localization in the cell

MicroRNAs (miRNAs) in solid malignancies can behave as predictors of either good or poor outcome. This is the case with members of the miR-200 family, which are the primary regulators of the epithelial to mesenchymal transition and have been reported to act as both oncogenes and tumor suppressors in independent studies. Expression of miR-200c was assessed in a panel of ovarian cancer cell lines with inherent or acquired drug-resistance. Luciferase reporter assay and ribonucleic-immuno-precipitation assay was used to in vitro characterise the complexes between miR-200c, HuR and class III β-tubulin (TUBB3). Nanofluidic technology and immunohistochemistry were used to analyze the expression of HuR, TUBB3 and miR-200c in 220 ovarian cancer patients. Using such approach, we demonstrated that overexpression of miR-200c in ovarian cancer resulted in poor or good outcome depending on interaction with the RNA binding protein HuR. When the localization of HuR was confined in the nucleus, high expression of miR-200c suppressed class III β-tubulin (TUBB3) expression and resulted in a good prognosis, whereas when HuR occurred in cytoplasm, the same miRNA enhanced TUBB3 expression and produced a poor outcome. Indeed, in an ovarian cancer cell line model, the miR-200c increased HuR binding on TUBB3 mRNA in stressing microenvironmental conditions. This study demonstrated how the prognostic power of a single factor can depend on interactions with additional factors. Through a multidimensional analysis of all components, the actual mechanism(s) underlying the aggressive biological behavior of ovarian cancer can be unraveled, and the prognosis of ovarian cancer patients can be rendered based on rational explanations.

Citation Format: Silvia Prislei, Enrica Martinelli, Marisa Mariani, Giuseppina Raspaglio, Steven Sieber, Gabriella Ferrandina, Shohreh Shahabi, Giovanni Scambia, Cristiano Ferlini. MiR-200c can mediate either poor or good outcome in ovarian cancer depending on HuR localization in the cell. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 1957. doi:10.1158/1538-7445.AM2013-1957

MiR-200c and HuR in ovarian cancer

BACKGROUND

MicroRNAs in solid malignancies can behave as predictors of either good or poor outcome. This is the case with members of the miR-200 family, which are the primary regulators of the epithelial to mesenchymal transition and have been reported to act as both oncogenes and tumor suppressors. This study assessed the role of miR-200c as regulator of class III β-tubulin (TUBB3), a factor associated with drug-resistance and poor prognosis in ovarian cancer.

METHODS

Expression of miR-200c was assessed in a panel of ovarian cancer cell lines with inherent or acquired drug-resistance. Stable overexpression of miR-200c was obtained in A2780 and Hey cell lines. Crosslinking-coupled affinity purification method and ribonucleic-immunoprecipitation assay were used to characterise the complexes between miR-200c, HuR and 3'UTR region of TUBB3 mRNA. Nanofluidic technology and immunohistochemistry were used to analyze the expression of HuR, TUBB3 and miR-200c in 220 ovarian cancer patients.

RESULTS

In a panel of ovarian adenocarcinoma cell lines, we observed a direct correlation between miR-200c expression and chemoresistance. In A2780 cells miR-200c targeted TUBB3 3'UTR, while a positive correlation was observed between miR-200c and TUBB3 expression in most of the other cell lines. Through the analysis of 3'UTR-associated complexes, we found that the miR-200c can increase the association of the RNA binding protein HuR with TUBB3 mRNA, whereas HuR binding enhanced TUBB3 mRNA translation. Most importantly, in our analysis on 220 ovarian cancer patients we observed that overexpression of miR-200c correlated with poor or good outcome depending on the cellular localization of HuR.

CONCLUSION

This study suggests a model for the combined regulatory activity of miR-200c and HuR on TUBB3 expression in ovarian cancer. When HuR is nuclear, high expression of miR-200c inhibits TUBB3 expression and results in a good prognosis, whereas when HuR occurs in cytoplasm, the same miRNA enhances TUBB3 expression and produces a poor outcome. These findings reveal the usefulness of multidimensional analysis in the investigation of the prognostic role of miRNA expression.

βIII-Tubulin: biomarker of taxane resistance or drug target?

INTRODUCTION

βIII-Tubulin (TUBB3) is predominantly expressed in neurons of the central and peripheral nervous systems, while in normal non-neoplastic tissues it is barely detectable. By contrast, this cytoskeletal protein is abundant in a wide range of tumors. βIII-Tubulin is linked to dynamic instability of microtubules (MTs), weakening the effects of agents interfering with MT polymerization. Based on this principle, early studies introduced the classical theory linking βIII-tubulin with a mechanism of counteracting taxane activity and accordingly, prompted its investigation as a predictive biomarker of taxane resistance.

AREAS COVERED

We reviewed 59 translational studies, including cohorts from lung, ovarian, breast, gastric, colorectal and various miscellaneous cancers subject to different chemotherapy regimens.

EXPERT OPINION

βIII-Tubulin functions more as a prognostic factor than as a predictor of response to chemotherapy. We believe this view can be explained by βIII-tubulin's association with prosurvival pathways in the early steps of the metastatic process. Its prognostic response increases if combined with additional biomarkers that regulate its expression, since βIII-tubulin can be expressed in conditions, such as estrogen exposure, unrelated to survival mechanisms and without any predictive activity. Additional avenues for therapeutic intervention could emerge if drugs are designed to directly target βIII-tubulin and its mechanism of regulation.

Gli family transcription factors are drivers of patupilone resistance in ovarian cancer

Epothilones constitute a novel class of antitubulin agents that are active in patients who relapse after treatment with other chemotherapeutics. This study investigated the molecular mechanisms leading to the onset of epothilone-B (patupilone) resistance in ovarian cancer. Results demonstrated that the Gli family of transcription factors was overexpressed in resistant cells and that treatment with a specific Gli1 inhibitor (GANT58) made cells more susceptible to treatment, partially reversing drug resistance. We also demonstrated that Gli1 knockdown halted growth in resistant cells that were exposed to patupilone, confirming that Gli1 is capable of directly mediating epothilone-B resistance. Another observation from our research was that patupilone-resistant cells produced HGF and acquired characteristics of a mesenchymal phenotype. However, HGF silencing alone was not capable of converting the drug-resistant phenotype to a susceptible one, and in this case we demonstrated that Gli1 overexpression led to an increase in HGF, establishing a functional link between Gli1 and HGF. These results demonstrated that Gli1 played a key role in driving resistance to patupilone, suggesting that the combination of epothilones and Gli1-targeted agents could be exploited to improve outcomes in ovarian cancer patients resistant to standard treatments.

Class III β-tubulin and the cytoskeletal gateway for drug resistance in ovarian cancer

The Class III β-tubulin isotype (βIII-tubulin) is a predictive biomarker in ovarian cancer and other solid tumor malignancies. We discovered that βIII-tubulin function is linked to two GTPases: guanylate-binding protein 1 (GBP1), which activates its function, and GNAI1, which inhibits it. This finding was demonstrated in a panel of ovarian cancer cells resistant to several chemotherapeutic agents. Using a protein microarray, we identified PIM1 as the downstream partner of GBP1, recruited into the cytoskeleton under hypoxic conditions. The clinical value of these observations was tested by performing an archive study of 98 ovarian cancer patients, which demonstrated that the βIII-tubulin -/PIM1- cohort responded to treatment, exhibiting long overall survival (OS), while βIII-tubulin +/PIM+ patients experienced poor outcomes and OS times similar to patients receiving palliation alone. βIII-tubulin expression is commonly believed responsible for paclitaxel resistance due to its enhancement of the dynamic instability of microtubules, which counteracts the activity of taxanes. In contrast, our research reveals that βIII-tubulin behaves as a gateway for prosurvival signals, such as PIM1, to move into the cytoskeleton. When cells are exposed to microenvironmental stressors, they activate this pathway by telling the cytoskeleton to incorporate PIM1 through GBP1 and βIII-tubulin, which ultimately leads to drug resistance. This discovery reveals that βIII-tubulin does not act alone but requires partners to play its role. The discovery of such protein:protein interactions underlying this prosurvival cascade makes feasible the development of therapeutic approaches using novel compounds that are capable of inhibiting the transmission of prosurvival signals into the cytoskeleton.

Abstract 4522: Androgen receptor is a main driver of aggressiveness in colorectal cancer through the class III β-tubulin pathway

Colorectal cancer is still one of the deadliest diseases in western countries, particularly for those patients in which the diagnosis is performed at advanced stage. To identify useful predictive biomarkers of the outcome, we assessed using immunohistochemistry the expression of class III (TUBB3) and class V β-tubulin (TUBB6) in a retrospective clinical study on 180 colorectal cancer patients. When stratified by gender, we noticed that only in females a significant link between poor survival, metastatic disease and the expression of both TUBB3 and TUBB6 was found, while in males no relationship was detectable. In order to get insights into this phenomenon, we analyzed the expression levels of both tubulin isotypes in a panel of 22 colorectal cancer cell lines (13 from males and 9 from females) in basal conditions and after serum starvation, as a stimulus capable to activate the expression of this survival pathway. Male cell lines exhibited a relative resistance to serum starvation and higher levels of the tubulin isotypes, while only in female there was the activation of the pathway under stressing conditions. These findings indicate that in males the survival pathway related to TUBB3/TUBB6 is constitutively active, while in females it is activated by environmental stressors. In order to test if androgens could be responsible for the constitutive activation of this pathway in males, we analyzed the expression of androgen receptor (AR) in the 22 cancer cell lines. A statistically significant correlation was found between AR and TUBB3 (R= 0. 53, p= 0.0062) and TUBB6 (R=0.41; p=0.048) at the gene level. The pivotal role of androgen receptor in driving this pathway was demonstrated after constitutive silencing of AR in two models (SW480 and COLO-320) with high AR and TUBB3/TUBB6 expression. Knock-down of AR was associated to a significant reduction of the expression of both TUBB3 and TUBB6, along with decreased clonogenic activity and increased sensitivity to agents such as oxaliplatin and SN-38. Mortality for colorectal cancer is different by gender and higher in males. The molecular basis for such difference is unknown. In this study, we have demonstrated that in female cell lines (and probably patients) the activation of the survival pathway mediated by TUBB3 and TUBB6 is driven by microenvironmental stress like serum starvation. Those tumors which grow in the most compelling microenvironments will overexpress both proteins and will exhibit an aggressive behavior. In male this correlation is lost since the survival pathway is constitutively active and not dependent on microenvironmental conditioning. This makes that the disease intrinsically more aggressive and less sensitive to treatments. The involvement of AR in the activation of this survival pathway opens the avenue to clinical trials assessing the efficacy of antiandrogens in the management of advanced colorectal cancer.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 4522. doi:1538-7445.AM2012-4522

Class III β-tubulin (TUBB3): more than a biomarker in solid tumors?

Class III β-tubulin (TUBB3) is a prominent mechanism of drug resistance expressed in a variety of solid tumors and particularly in lung and ovarian cancer. In the classical view, TUBB3 expression and drug resistance have been linked, and together they have been associated with a perturbation in microtubule dynamics. In keeping with this observation, TUBB3 was associated with drug resistance only when chemotherapy included a taxane in its chemical composition. In this review, we demonstrate that the classical supposition about TUBB3 is not correct, and that instead TUBB3 expression is linked to drug resistance as a complex survival mechanism activated by microenvironmental conditions such as poor nutrient supply and hypoxia.

Gender influences the class III and V β-tubulin ability to predict poor outcome in colorectal cancer

PURPOSE

Colorectal cancer is one of the deadliest diseases in Western countries. To predict the outcome of therapy, we assessed the role of class III (TUBB3) and class V β-tubulin (TUBB6) as predictive biomarkers.

EXPERIMENTAL DESIGN

Using immunohistochemistry and nanofluidics, the expression of TUBB3 and TUBB6 was assessed in two cohorts of 180 and 134 patients, respectively. The CYP17A1 RS743572 was genotyped to identify GG carriers with enhanced androgen levels. TUBB3 and TUBB6 were investigated in 22 colorectal cancer cell lines in basal conditions and after serum starvation, the latter serving as activator of this prosurvival pathway. To ascertain the role of androgen receptor (AR) in such regulation, we silenced AR and checked TUBB3 and TUBB6 expression and sensitivity to chemotherapy.

RESULTS

There was a link between poor survival, the expression of TUBB3/TUBB6, and AR only in females. Conversely, only in males carriers of the GG phenotype exhibited the worst outcome. Importantly, male cell lines were resistant to serum starvation and exhibited higher levels of TUBB6, thereby suggesting that the pathway is activated by androgens. In female cells this phenomenon was absent. In both genders, AR was the main driver of TUBB3/TUBB6 expression, as constitutive silencing of AR was associated with downregulation of TUBB3/TUBB6 expression and increased sensitivity to oxaliplatin and SN-38.

CONCLUSIONS

The involvement of androgens in the TUBB3 pathway opens the way for clinical trials to assess the efficacy of antiandrogens for increasing the efficacy of chemotherapy in male colorectal cancer patients.

Design and synthesis of 2-heterocyclyl-3-arylthio-1H-indoles as potent tubulin polymerization and cell growth inhibitors with improved metabolic stability

New arylthioindoles (ATIs) were obtained by replacing the 2-alkoxycarbonyl group with a bioisosteric 5-membered heterocycle nucleus. The new ATIs 5, 8, and 10 inhibited tubulin polymerization, reduced cell growth of a panel of human transformed cell lines, and showed higher metabolic stability than the reference ester 3. These compounds induced mitotic arrest and apoptosis at a similar level as combretastatin A-4 and vinblastine and triggered caspase-3 expression in a significant fraction of cells in both p53-proficient and p53-defective cell lines. Importantly, ATIs 5, 8, and 10 were more effective than vinorelbine, vinblastine, and paclitaxel as growth inhibitors of the P-glycoprotein-overexpressing cell line NCI/ADR-RES. Compound 5 was shown to have medium metabolic stability in both human and mouse liver microsomes, in contrast to the rapidly degraded reference ester 3, and a pharmacokinetic profile in the mouse characterized by a low systemic clearance and excellent oral bioavailability.

Abstract 4055: Class III β-tubulin and the cytoskeletal gateway of drug resistance in ovarian cancer

Objective: Class III β-tublin (TUBB3) is a potent prognostic biomarker for ovarian cancer and other solid tumors. In this work we have discovered a novel role for TUBB3 as a gateway for cytoskeletal prosurvival signals.

Methods: Through a genomic screening of a cell line made resistant to a drug whose activity is TUBB3 dependent, we have identified two GTPases (GBP1 and GNAI1) whose expression is strictly related to TUBB3 expression. Using the technique of Far Western Blotting, we have demonstrated that these GTPases physically interact with TUBB3. At variance of TUBB3, the two GTPAses can be overexpressed in vitro. Therefore, they served as prey in a high density protein microarray to identify protein kinases capable to interact with them.

Results: Using transient overexpression the functional role of the two GTPases was ascertained, with GBP1 capable to activate the TUBB3 pathway and GNAI1 with an inhibitory function on its. The physical interaction between the two GTPases and cytoskeletal proteins were proven with Far Western Blot. At variance with TUBB3, the two GTPases can be expressed as recombinant proteins. Taken advantage of this fact, the two proteins served as prey on high density protein array containing over 9,000 human proteins. At least 18 protein kinases were capabe to interact with either GBP1 or GNAI1 or both. Among these kinases, we focused our attention on PIM1. PIM1:TUBB3 correlation was proven in ovarian cancer cell lines, both sensitive and resistant to chemotherapeutics, using coimmunoprecipiation experiments and again far western blotting. For the first time, we discovered that PIM1 is expressed in the microtubules and its expression is directly related to resistance to Paclitaxel and Cisplatin, but not to Epothilone-B. Importantly, PIM1 is overexpressed in cytoskeleton in microtubules when TUBB3 pathway is activated in hypoxic conditions. Finally, to analyze the translational value of our findings, we performed immunohistochemical analysis of TUBB3 and PIM1 expression in a clinical subset of 98 ovarian cancer patients. This approach revealed that double negative patients (TUBB3 and PIM1) have an overall survival (median 76 months) better than that noticeable in double positive (median 29 months).

Conclusions: TUBB3 is commonly believed as a simple mechanism of Paclitaxel-resistance. Instead, this work demonstrates that TUBB3 is a gateway for prosurvival signals like PIM1 into the cytoskeleton. Ovarian cancer patients exhibiting expression of both TUBB3 and PIM1 have high probability of drug resistance and extreme short survival and should be carefully monitored for response to first line chemotherapy.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 4055. doi:10.1158/1538-7445.AM2011-4055

RON and cisplatin resistance in ovarian cancer cell lines

RON (recepteur d'origine nantais) tyrosine kinase receptor has revealed its tumorigenic potential in recent studies. RON was reported to be overexpressed in 55% of primary ovarian carcinoma samples and furthermore its activation increases cell motility and invasiveness. In this study, we investigated the correlation between RON expression and chemoresistance in ovarian cancer cells. In A2780 cells, a model featured by high chemosensitivity to cisplatin, stable overexpression of RON was able to reduce sensitivity to this agent, while incubation with a blocking anti-RON antibody (ID1) increased the cisplatin-induced growth inhibition effect. Moreover, we observed an increased RON expression both at the mRNA and protein level in A2780 cells made resistant to doxorubicin and paclitaxel (A2780ADR and TC 1, respectively), two cell lines exhibiting a collateral resistance to cisplatin. OVCAR-3 cells, showing high levels of RON expression, also displayed inherent cisplatin resistance. The morphology observed in these resistant cells is consistent with a scattering phenotype and a RON-activated state. RON expression levels were monitored upon hypoxia. A 2.5-fold increase of RON expression was noticed in response to hypoxia in OVCAR-3 cells, in parallel with a decrease of E-cadherin mRNA. Altogether these results suggest an involvement of RON in the acquisition of cisplatin resistance and highlight the importance of this factor as a promising target for combination with cisplatin-based chemotherapy in ovarian cancer.

HuR regulates beta-tubulin isotype expression in ovarian cancer

The supply of oxygen and nutrients to solid tumors is inefficient because cancer tissues have an inadequate number of microvessels, thus inducing the selective growth of the most aggressive cancer cells. This explains why many of the factors underlying a poor prognosis are induced in hypoxic/hypoglycemic conditions. Among these factors, a prominent role in several solid tumors is played by the class III beta-tubulin gene (TUBB3). The study described here reveals that glucose deprivation enhances TUBB3 expression at both the gene and protein levels in A2780 ovarian cancer cells. In silico analysis of TUBB3 mRNA sequence predicted a putative binding site for the RNA-binding protein Hu antigen (HuR) in the 3' flanking untranslated region. A hypoglycemic-dependent engagement of this site was shown using RNA pull-down and ribonucleoimmunoprecipitation techniques. Thereafter, HuR gene silencing revealed that TUBB3 translation is HuR dependent in hypoglycemia because HuR silencing inhibited the entry of TUBB3 mRNA into cytoskeletal and free polysomes. Finally, the clinical value of this finding was assessed in a clinical cohort of 46 ovarian cancer patients in whom it was found that HuR cytoplasmic staining was associated with high levels of TUBB3 and poor survival.

The epithelial-mesenchymal transition and the estrogen-signaling in ovarian cancer

Epithelial ovarian cancer is the leading cause of death for gynecological cancer in most of the Western world; lethality ensues from the occurrence of occult metastasis within the peritoneal cavity, a process requiring the acquisition of capacity for migration and invasiveness by ovarian tumor cells (metastatic phenotype), and characterized by a complex series of interrelated cellular events. Unlike most carcinomas that dedifferentiate during neoplastic progression with loss of epithelial E-cadherin (epithelial to mesenchymal transition, EMT), ovarian carcinomas undergo transition to a more epithelial phenotype, early in tumor progression, with increased E-cadherin expression. Subsequent reacquisition of mesenchymal features is observed in late-stage tumors, and loss of E-cadherin expression or function is a factor in ovarian cancer progression. Changes in E-cadherin expression are indicative of the phenotypic plasticity that occurs in ovarian cancer, with a variety of signal transduction pathways impinging on the regulation of E-cadherin levels or subcellular distribution. Among them, the Snail transcription family, consisting of members SNAIL and SLUG, is thought to be mainly involved in the repression of E-cadherin expression, leading to EMT. E-cadherin, SNAIL, and SLUG also represent crucial targets of estrogen signaling. In this review, we discuss recent advances in the understanding of the role of estrogen signaling in the complex network underlying the phenotypic plasticity in ovarian cancer. Insight into the mechanisms involved will allow rational drug designs, aimed at the molecules critical to cellular signaling.

Abstract 645: Class V β-tubulin expression as biomarker in solid tumors

Microtubules are a component essential of the cytoskeleton and mediate a complex network of functions, including the assembly of mitotic spindle but also the intracellular trafficking of signaling proteins. In order to achieve their functions, composition of microtubules is tightly regulated, particularly at the (+) end, exposing the β-tubulin subunit. At least seven independent genes encode for β-tubulin, whose expression is diverse in several tissues. Functionally β-tubulin isotypes can be divided in constitutive isotypes and regulatory isotypes. Regulatory isotypes include class III β-tubulin (TUBB3), whose role as factor of resistance to chemotherapy has been demonstrated in a large number of solid tumors. Some structural motifs of TUBB3 are shared with class V β-tubulin (TUBB6), but since no commercial antibodies are available for this isotype its role as an additional factor of chemoresistance is not known. In this work we have developed a polyclonal anti-TUBB6 antibody. Since the highest degree of dishomology between the β-tubulin isotypes is concentrated at the C-terminus, all the tails of the β-tubulin isotypes were cloned in E. coli in a carrier vector encoding MBP (maltose-binding protein). Recombinant proteins were expressed in E. coli and then purified through columns filled with Amylose resin column, able to entrap MBP. The negative control was represented by MBP alone. The developed anti-TUBB6 antibody was validated since it demonstrated specific reactivity only against TUBB6. Therefore, the profile of expression of TUBB6 was assessed in a panel of normal and cancer tissues. In normal tissues, immunostaining of TUBB6 was confined to given cellular elements and in a focal pattern such as in ciliary cells of bronchus, salpinx, thereby suggesting that class V is focally associated to the cilium complex. In contrast to the focal expression noticed in normal tissues, in cancer specimens TUBB6 exhibited a diffuse staining pattern, with the highest expression detectable in colon and prostate carcinoma. In order to have some insights on the role of TUBB6 as a biomarker, we studied TUBB6 expression in a cohort of 56 ovarian cancer patients with a median follow up of 54 months. There was no statistically significant difference in terms of Time to Progression (TTP) in cases with high versus low TUBB6 expression (p value= 0.4). On the other hand, cases with high TUBB6 expression showed a worse Overall Survival (OS) with respect to cases with low TUBB6 expression (median OS= 50 months versus median OS= 96 months, respectively, p value=0.047). In summarizing these results, patients expressing high levels of TUBB6 are featured by biological aggressiveness and poor response in terms of OS to standard chemotherapy. These results suggest that TUBB6 could be useful as a biomarker for ovarian cancer patients and possibly other tumors.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 645.

IgG autoantibody to brain beta tubulin III associated with cytokine cluster-II discriminate cerebral malaria in central India

BACKGROUND

The main processes in the pathogenesis of cerebral malaria caused by Plasmodium falciparum involved sequestration of parasitized red blood cells and immunopathological responses. Among immune factors, IgG autoantibodies to brain antigens are increased in P. falciparum infected patients and correlate with disease severity in African children. Nevertheless, their role in the pathophysiology of cerebral malaria (CM) is not fully defined. We extended our analysis to an Indian population with genetic backgrounds and endemic and environmental status different from Africa to determine if these autoantibodies could be either a biomarker or a risk factor of developing CM.

METHODS/PRINCIPAL FINDINGS

We investigated the significance of these self-reactive antibodies in clinically well-defined groups of P. falciparum infected patients manifesting mild malaria (MM), severe non-cerebral malaria (SM), or cerebral malaria (CM) and in control subjects from Gondia, a malaria epidemic site in central India using quantitative immunoprinting and multivariate statistical analyses. A two-fold complete-linkage hierarchical clustering allows classifying the different patient groups and to distinguish the CM from the others on the basis of their profile of IgG reactivity to brain proteins defined by PANAMA Blot. We identified beta tubulin III (TBB3) as a novel discriminant brain antigen in the prevalence of CM. In addition, circulating IgG from CM patients highly react with recombinant TBB3. Overall, correspondence analyses based on singular value decomposition show a strong correlation between IgG anti-TBB3 and elevated concentration of cluster-II cytokine (IFNgamma, IL1beta, TNFalpha, TGFbeta) previously demonstrated to be a predictor of CM in the same population.

CONCLUSIONS/SIGNIFICANCE

Collectively, these findings validate the relationship between antibody response to brain induced by P. falciparum infection and plasma cytokine patterns with clinical outcome of malaria. They also provide significant insight into the immune mechanisms associated to CM by the identification of TBB3 as a new disease-specific marker and potential therapeutic target.

Abstract C231: A great mime produced by nature: The case of paclitaxel

Paclitaxel is widely used in the medical treatment of solid tumors. Despite the clinical success still now the exact mechanism(s) through which the drug kills cancer cells are unknown. In this work we provide evidence, through Surface Plasmon Resonance technology, that paclitaxel beside to microtubules is able also to target mitochondria by directly interacting with the disordered loop of Bcl-2, thereby stimulating the opening of the permeability transition pore channel and ultimately reverting Bcl-2 function from antiapoptotic to proapoptotic. Studying the paclitaxel binding site in Bcl-2, we discovered through molecular modeling that it is positioned in the disordered loop domain and is extraordinarily similar to that experimentally defined in beta-tubulin, thereby prompting us to speculate that paclitaxel is a peptidomimetic factor. Since to our knowledge, the only factor able to revert the Bcl-2 function from protector to cell killer is Nur77, we tested the hypothesis that paclitaxel mimics the activity of Nur77. To address this issue, coimmunoprecipitation experiments demonstrated that like paclitaxel Nur77 interacts with Bcl-2 in the disordered loop domain and with beta-tubulin. Moreover, stably transformed cells with Nur77 show the classical slow band isoform of Bcl-2 detectable in cells treated with paclitaxel. Finally, interaction between Nur-77 and Bcl-2 was inhibited by paclitaxel, thus demonstrating that the drug and Nur77 compete for the binding to Bcl-2. The discovery of the molecular component mimicked by paclitaxel could promote the development of novel agonists of the paclitaxel receptor with a nontaxane structure.

Citation Information: Mol Cancer Ther 2009;8(12 Suppl):C231.

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.

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.

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.

Novel C-seco-taxoids possessing high potency against paclitaxel-resistant cancer cell lines overexpressing class III beta-tubulin

Novel C-seco-taxoids were synthesized from 10-deacetylbaccatin III and their potencies evaluated against drug-sensitive and drug-resistant cancer cell lines. The drug-resistant cell lines include ovarian cancer cell lines resistant to cisplatin, topotecan, adriamycin and paclitaxel overexpressing class III beta-tubulin, A2780TC1 and A2780TC3. The last two cell lines were selected through chronic exposure of A2780wt to paclitaxel and Pgp blocker cyclosporine. All novel C-seco-taxoids exhibited remarkable potency against A2780TC1 and A2780TC3 cell lines, and no cross resistance to cisplatin- and topotecan-resistant cell lines, A2780CIS and A2780TOP. Four of those C-seco-taxoids exhibit much higher activities than IDN5390 against paclitaxel-resistant cell lines, A2780ADR, A2780TC1 and A2780TC3. SB-CST-10202 possesses the best all-round high potencies across different drug-resistant cell lines. Molecular modeling studies, including molecular dynamics simulations, on the drug-protein complexes of class I and III beta-tubulins were performed to identify possible cause of the remarkable potency of these C-seco-taxoids against paclitaxel-resistant cell lines overexpressing class III beta-tubulin.

Chemoresistant tumor cell lines display altered epidermal growth factor receptor and HER3 signaling and enhanced sensitivity to gefitinib

Deregulated signaling through the epidermal growth factor receptor (EGFR) is involved in chemoresistance. To identify the molecular determinants of sensitivity to the EGFR inhibitor gefitinib (Iressa, ZD1839) in chemoresistance, we compared the response of matched chemosensitive and chemoresistant glioma and ovarian cancer cell lines. We found that chemoresistant cell lines were 2- to 3-fold more sensitive to gefitinib growth-inhibitory effects, because of decreased proliferation rather than survival. Sensitivity to gefitinib correlated with overexpression and constitutive phosphorylation of HER2 and HER3, but not EGFR, altered HER ligand expression, and enhanced activation of EGF-triggered EGFR pathway. No activating mutations were found in EGFR. Gefitinib fully inhibited EGF-induced and constitutive Akt activation only in chemoresistant cells. In parallel, gefitinib downregulated constitutively phosphorylated HER2 and HER3, and activated GSK3beta with a concomitant degradation of cyclin D1. Ectopically overexpressed HER2 on its own was insufficient to sensitize chemonaive cells to gefitinib. pHER3 coimmunoprecipitated with p85-PI3K in chemoresistant cells and gefitinib dissociated these complexes. siRNA-mediated inhibition of HER3 decreased constitutive activation of Akt and sensitivity to gefitinib in chemoresistant cells. Our study indicates that in chemoresistant cells gefitinib inhibits both an enhanced EGF-triggered pathway and a constitutive HER3-mediated Akt activation, indicating that inhibition of HER3 together with that of EGFR could be relevant in chemorefractory tumors. Furthermore, in combination experiments gefitinib enhanced the effects of coadministered drugs more in chemoresistant than chemosensitive ovarian cancer cells. Combined treatment might be therapeutically beneficial in chemoresistant tumors from ovary and likely from other tissues.

Molecular mechanisms of patupilone resistance

Patupilone is an epothilone in advanced clinical development that has shown promising efficacy in heavily pretreated patients. This study aimed at characterizing the mechanisms of patupilone activity in resistant patients. To this end, we generated patupilone-resistant cells using two cellular models, the first characterized by high chemosensitivity and low class III beta-tubulin (TUBB3) expression (A2780), and the second by low chemosensitivity and high TUBB3 expression (OVCAR-3). The obtained cell lines were named EPO3 and OVCAR-EPO, respectively. The same selection procedure was done in A2780 cells to generate a paclitaxel-resistant cell line (TAX50). Factors of resistance are expected to increase in the drug-resistant cell lines, whereas factors of drug sensitivity will be down-regulated. Using this approach, we found up-regulation of TUBB3 in TAX50, but not EPO3, cells, showing that TUBB3 mediates the resistance to paclitaxel but not to patupilone. Moreover, TUBB3 was a factor of patupilone sensitivity because OVCAR-EPO cells exhibited a dramatic reduction of TUBB3 and a concomitant sensitization to hypoxia and cisplatin-based chemotherapy. To identify the mechanisms underlying patupilone resistance, tubulin genes were sequenced, thereby revealing that a prominent mechanism of drug resistance is represented by point mutations in class I beta-tubulin. Overall, these results suggest that paclitaxel and patupilone have nonoverlapping mechanisms of resistance, thus allowing the use of patupilone for those patients relapsing after paclitaxel-based chemotherapy. Furthermore, patupilone represents a promising first-line option for the treatment of high-risk ovarian cancer patients, who exhibit high TUBB3 levels and poor response to standard paclitaxel-platin chemotherapy.

Antitumor effect in medulloblastoma cells by gefitinib: Ectopic HER2 overexpression enhances gefitinib effects in vivo

The effects of the epidermal growth factor receptor (EGFR) inhibitor gefitinib on cell growth and signaling were evaluated in three medulloblastoma (MB) cell lines (D283, D341, Daoy), one supratentorial primitive neuroectodermal tumor cell line (PFSK), and four MB primary cultures. Cell lines showed diverse expression of EGFR and human epidermal receptor 2 (HER2), with high levels of constitutively activated HER2 in the HER2-overexpressing D341 and D283 cells. Gefitinib sensitivity varied across lines and was not related to expression of HER receptors or receptor baseline activation. Gefitinib induced G(0)/G(1) arrest in all lines, whereas apoptosis was dose-dependently induced only in D283 and D341 cells. The molecular response to gefitinib was investigated in Daoy and D341 lines, which showed a higher (half-maximal inhibitory concentration [IC(50)], 3.8 microM) and lower (IC(50), 6.6 microM) sensitivity to the agent, respectively. Gefitinib inhibited constitutive and EGF-triggered EGFR phosphorylation in both lines but was ineffective in constitutive activation of HER2 in D341 cells. Phosphorylated AKT inhibition paralleled that of phosphorylated EGFR, suggesting the presence of an autocrine gefitinib-sensitive EGFR/AKT pathway. On the whole, EGF-dependent signaling was less responsive to ligand stimulation and gefitinib inhibition in D341 cells, which correlated with the lower sensitivity to gefitinib's antiproliferative effect of this line. In vivo, the growth of D341 and Daoy xenografts treated with gefitinib at 150 mg/kg per day was inhibited by approximately 50%. Ectopically overexpressed HER2 in Daoy cells significantly increased sensitivity to gefitinib's antitumor effects in vivo (tumor volume inhibition = 78%). Our data indicate that gefitinib might be a molecularly targeted agent for the treatment of MB.

Role of microRNAs in drug-resistant ovarian cancer cells

OBJECTIVES

Chemotherapy is the preferred therapeutic approach for the therapy of advanced ovarian cancer, but a successful long-term treatment is prevented by the development of drug resistance. Recent works have underlined the involvement of non-coding RNAs, microRNAs (miRNAs) in cancer development, with several conjectures regarding their possible involvement in the evolution of drug resistance. This work was aimed to identify selected microRNAs involved in the development of chemoresistance in ovarian cancer.

METHODS

High-throughput analysis of the miRNA profile in a panel of paclitaxel- (A2780TAX, A2780TC1 and A2780TC3) and cisplatin-resistant (A2780CIS) cells was assessed using a microarray platform and subsequent validation with qPCR and Northern blots. Downstream target validation was performed for miR-130a and the target M-CSF.]

RESULTS

Six miRNAs (let-7e, miR-30c, miR-125b, miR-130a and miR-335) were always diversely expressed in all the resistant cell lines. Let-7e was upregulated in A2780TAX cells, while it was downregulated in the other resistant cell lines. The opposite phenomenon was obtained for miR-125b, which was downregulated in A2780TAX and upregulated in the other cell lines. The miR-30c, miR-130a and miR-335 were downregulated in all the resistant cell lines, thereby suggesting a direct involvement in the development of chemoresistance. Finally downstream target validation was proven for the miR-130a, whose downregulation was linked to the translational activation of the M-CSF gene, a known resistance factor for ovarian cancer.

CONCLUSIONS

Our results indicate that ovarian cancer drug resistance is associated with a distinct miRNA fingerprint, and miRNA microarrays could represent a prognostic tool to monitor the chemotherapy outcome.