Myriam Banville

Roles for Endothelin Receptor B and BCL2A1 in Spontaneous CNS Metastasis of Melanoma

Metastatic spread of melanoma to the central nervous system (CNS) is a common and devastating manifestation of disease progression, which, despite its clinical importance, remains poorly understood with respect to underlying molecular mechanisms. Using a recently developed preclinical model of spontaneous melanoma CNS metastasis, we have identified alterations in expression of endothelin receptor B (EDNRB) as a potential factor that influences brain metastatic potential. Induced overexpression of this gene mediated enhanced overall metastatic disease, and resulted in an increased incidence of spontaneous CNS metastases. In contrast, the overexpression of other highlighted genes, such as BCL2A1, did not affect the incidence of CNS metastases but nevertheless appears to facilitate intracranial tumor growth. The prometastatic effect in the CNS associated with EDNRB appears to be mediated by the interaction with its ligands resulting in enhanced tumor cell proliferation and thus intracranial melanoma growth. That EDNRB contributes to melanoma metastasis is underscored by the fact that its therapeutic inhibition by the EDNRB-specific inhibitor A192621 translated into improved outcomes when treating mice with either visceral metastases or intracranial tumors. The identification of an influential role of EDNRB in CNS melanoma spontaneous metastasis may provide both a target for therapeutic intervention as well as a potential prognostic marker for patients having an increased predisposition for incidence of CNS melanoma metastases.

Bacterial luciferase produced with rapid-screening baculovirus vectors is a sensitive reporter for infection of insect cells and larvae.

Bacterial luciferase, derived from a fusion of the luxA and luxB genes of Vibrio harveyi, has been expressed at very high levels in caterpillars and insect cells. The coding sequence for luciferase was inserted into vectors developed in our laboratory which were designed to expedite screening of recombinant virus. These vectors contained the beta-galactosidase indicator gene under control of immediate early (IE1), early (ETL), or very late (P10) promoters and a cloning site for inserting the fused luciferase gene next to the polyhedrin promoter. Recombinant baculoviruses containing the luciferase gene as well as the beta-galactosidase gene could be easily selected when Bluo-gal (beta-galactosidase indicator) was included in the plaque assays. Using cells derived from the fall armyworm (Spodoptera frugiperda), luciferase was strongly expressed very late in infection (48-72 h). The bacterial luciferase assay was sufficiently sensitive that light production could be detected from an extract of a single cell. In addition, live insects, including the cabbage looper (Trichoplusia ni) and saltmarsh caterpillar (Estigmene acrea) were infected by mixing recombinant baculovirus into their diet. Cabbage loopers (with an average wet weight of 223 mg) produced at least 195 micrograms of active luciferase and levels of synthesis peaked between 96-120 h. The results indicate that bacterial luciferase may be used as a reporter of gene expression in insects.

Comparison of the thymidine kinase genes from three entomopoxviruses

The entomopoxviruses (insect poxviruses) of eastern spruce budworm (Choristoneura fumiferana), two year cycle spruce budworm (C. biennis) and the Indian red army worm (Amsacta moorei) are being studied in our laboratory for their potential as biological insecticides and expression vectors. These viruses characteristically replicate in the cytoplasm of insect cells and produce occlusion bodies that serve to protect the virion from the environment. By analogy to mammalian poxviruses, they should also contain a viral thymidine kinase (TK) that functions in viral DNA synthesis. The replication of the A. moorei entomopoxvirus was inhibited by bromodeoxyuridine whereas the baculovirus of Autographa californica was insensitive to this drug. This result was a biochemical indication that entomopoxviruses contained a kinase that phosphorylated this nucleoside analogue and thus viral DNA synthesis was inhibited. TK genes from the three different insect poxviruses were identified, cloned and sequenced. The sequences of the TK genes of the entomopoxviruses were closely related and exhibited 63.2% identity and 9.9% similarity at the protein level. However, there was only 36.7% identity and 13.6% similarity when these enzymes were compared to their mammalian poxvirus counterpart in vaccinia virus. Finally, one entomopoxvirus TK gene was expressed in Escherichia coli mutants lacking the enzyme. These bacteria were converted to a phenotype that could incorporate radioactive thymidine into their chromosomal DNA. The results presented in this paper provide impetus for the design of a recombinant entomopoxvirus expression system in which foreign genes could be introduced into the viral TK locus under selective pressure from bromodeoxyuridine.

The crystal structure and dimerization interface of GADD45γ

Gadd45 proteins are recognized as tumor and autoimmune suppressors whose expression can be induced by genotoxic stresses. These proteins are involved in cell cycle control, growth arrest, and apoptosis through interactions with a wide variety of binding partners. We report here the crystal structure of Gadd45γ, which reveals a fold comprising an αβα sandwich with a central five-stranded mixed β-sheet with α-helices packed on either side. Based on crystallographic symmetry we identified the dimer interface of Gadd45γ dimers by generating point mutants that compromised dimerization while leaving the tertiary structure of the monomer intact. The dimer interface comprises a four-helix bundle involving residues that are the most highly conserved among Gadd45 isoforms. Cell-based assays using these point mutants demonstrate that dimerization is essential for growth inhibition. This structural information provides a new context for evaluation of the plethora of protein–protein interactions that govern the many functions of the Gadd45 family of proteins.

The predicted amino acid sequence of the spheroidin protein from Amsacta moorei entomopoxvirus: lack of homology between major occlusion body proteins of different poxviruses

Entomopoxviruses replicate in the cytoplasm of insect cells and characteristically produce occlusion bodies which serve to protect the virion from the environment; the major component of these bodies is a protein called spheroidin. We have previously identified and sequenced the gene encoding the major occlusion body protein of eastern spruce budworm (Choristoneura biennis) entomopoxvirus (CbEPV) and found it to encode a 47K polypeptide which aggregates due to the formation of intermolecular disulphide bonds. In this publication we demonstrate that the insect poxvirus of Amsacta moorei produces spheroidin with a unit Mr of 114.8K. The gene for this protein was cloned and sequenced, and the predicted polypeptide was demonstrated to contain 38 cysteine residues, a leucine zipper for possible protein-protein interactions and 14 potential Asn-linked glycosylation sites. Other than possessing a large number of sulphydryl groups, this protein showed no homology to its analogue found in cells infected with CbEPV. Antibodies directed against occlusion body proteins of the two viruses also failed to cross-react significantly on Western blots. In addition, nucleic acid probes prepared from the two different genes did not cross-hybridize on Southern blots of genomic DNA prepared from the viruses. Finally, the occlusion body proteins from the two insect viruses were compared with the A-type inclusion body protein of cowpox virus. Again, little homology between these proteins was evident, with the exception of a generally high cysteine content and a similarity between their late gene promoters. We conclude that the major occlusion body proteins of different poxviruses possess diverse primary structures, but all are capable of yielding large aggregates through the formation of disulphide bonds.

Differential sensitivity of A549 non-small lung carcinoma cell responses to epidermal growth factor receptor pathway inhibitors.

It has been demonstrated that A549 non-small cell lung cancer (NSCLC) cells are sensitive to epidermal growth factor receptor (EGFR) inhibitors in in vivo xenograft animal models, but are relatively resistant in conventional in vitro monolayer growth assays. Here, we utilized anchorage-independent cell growth/survival assays as well as motility assays and demonstrated that these tests detect the effects of two EGFR inhibitors, the small molecule inhibitor AG1478 and the ligand-blocking antibody 225 mAb, on A549 cells more sensitively than monolayer growth assays. AG1478 was more effective than 225 mAb at inhibiting EGF-stimulated anchorage-independent cell growth, in part due to its pronounced ability to inhibit cell survival, whereas 225 mAb and AG1478 were both able to inhibit cell motility. In order to determine which EGFR signalling pathway components were most strongly associated with these cell responses, we analyzed in parallel the phosphorylation levels of EGFR itself as well as several downstream pathway elements. We found that the limited ability of 225 mAb to inhibit MAPK, PI3K and STAT3 phosphorylation correlated with its inability to promote anchorage independent apoptosis, but did not correlate with its ability to inhibit motility. Based on our results in A549 cells, we propose that EGF stimulates tumour progression of NSCLC largely through effects on anchorage-independent growth and survival, as well as motility.

Abstract 1778: Nimotuzumab, a humanized antiepidermal growth factor receptor antibody, interacts with EGFRvIII

Proceedings: AACR 101st Annual Meeting 2010‐‐ Apr 17‐21, 2010; Washington, DC Introduction: Glioblastomas frequently overexpress a variant form of EGFR, called variant III (EGFRvIII), which has an in-frame deletion of an 801-bp sequence in the extracellular domain. EGFRvIII does not bind EGF ligand but exhibits constitutive kinase activity that results in enhanced transformation, reduced apoptosis, and resistance to therapy. Nimotuzumab (Nmab) is an EGFR-targeting antibody that has demonstrated encouraging results in early clinical trials treating adult and pediatric brain tumors. Here we present data characterizing the interaction of Nmab with EGFRvIII. Methods: Binding of Nmab to the extracellular domain of wtEGFR and EGFRvIII was first characterized by SPR biosensor analysis: Nmab was captured via its Fc domain and varying concentrations of EGFRvIII and EGFRwt were flowed. Flow cytometry analysis was subsequently performed using a parental U87MG glioblastoma cell line and derivatives which were engineered to overexpress either wtEGFR or EGFRvIII. Results: Nmab bound EGFRvIII and EGFRwt with similar affinity, which was in the 10−8 M range. This KD is consistent with the previously reported affinity constant of Nmab for EGFRwt (Telavera et al, 2009). Binding was further analyzed by flow cytometry. Nmab bound both EGFRwt and EGFRvIII expressed on the surface of parental U87MG, U87MG EGFRvIII and U87MG wtEGFR cells. Additional data concerning effects of Nmab on EGFRvIII expressing cell lines will be presented. Conclusion: Nmab binds to wtEGFR and EGFRvIII with similar affinity, which supports development of the antibody as a therapeutic for glioblastoma. In U87MG glioblastoma cells, synergistic activity of Nmab in combination with radiotherapy has been previously reported (Diaz Miqueli et al, 2009). Nmab is currently being tested in an advanced randomized study in the first line setting for the treatment of adult glioma. Nmab is being tested in combination with radiation plus temozolomide, vs radiation plus temozolomide alone, with preliminary results expected in the second half of 2010. 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 1778.

Abstract 1216: Assays for the selection and functional characterization of antibody-drug conjugates at the National Research Council of Canada

One of the most promising and fastest growing classes of cancer therapeutics builds on the molecular targeting abilities of antibodies by combining them with drugs to generate highly specific antibody-drug conjugates (ADCs). However, the development of ADCs requires time-consuming selection of the antibody for every target and cancer type. Screening technologies based on the use of conjugated secondary antibodies provide a fast and efficient surrogate assay from which to identify which antibodies are best internalized and suitable for immunoconjugate development into ADCs. As part of its integrated antibody development initiative, NRC has isolated and characterized anti- mouse Fc and anti-human Fc monoclonal antibodies to serve as very selective detective reagents for various IgG isoforms. We have shown that these secondary antibodies are species specific, selective and of high affinity. Furthermore, they exhibit high specific potency and low background toxicity after conjugating them to drugs (DM1, MMAE) or immunotoxins(saporin) in cell viability studies. By combining this methodology with our proprietary mRNA and DNA expression database for the selection of appropriate cell lines, we plan on screening thousands of NRC antibodies generated against variety of cancer associated cell surface targets for ADC development. In addition to secondary conjugate cytotoxicity assays, we have developed a suite of assays based on cellular accumulation, endosomal routing and activation (intracellular drug release) of antibody drug conjugates. These assays can all contribute to our mechanistic understanding of ADCs under development. Combined with our strength in biologic production and characterization, this expertise promotes the integration and advancement of NRC9s capabilities and strengths in the area of Antibody-Drug Conjugates (ADCs), and can be used to establish strategic collaborations with other Canadian or international partners to develop external or internal NRC antibodies into novel ADC biologics. Citation Format: Maria L. Jaramillo, Luc Meury, Normand Jolicoeur, Myriam Banville, Limei Tao, Maureen O’Connor McCourt. Assays for the selection and functional characterization of antibody-drug conjugates at the National Research Council of Canada. [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 1216.

Abstract 1452: Examination of mechanisms involved in spontaneous melanoma metastasis to CNS

Cerebral metastases occur in a majority of metastatic melanoma patients and are the major cause of mortality in those cases. Testing of novel therapeutic approaches has been slowed by the absence of appropriate preclinical models of spontaneous metastatic melanoma, particularly spontaneous CNS metastasis. To examine the efficacy of potentially promising treatment regimens, a highly visceral metastatic variant of the human melanoma WM239 cell line, named 6-4L, was developed and used to test the effectiveness of metronomic chemotherapy in the treatment of advanced metastatic disease. Concurrent low-dose cyclophosphomide/vinblastine led to significant disease control of mice with overt metastases in lungs, liver and lymph nodes. Among mice that survived the long-term treatment, 20% showed the presence of spontaneous brain metastases which likely emerged as a result of prolonged survival mediated by the therapy. From these, 2 cell lines (131/4-5B1 and 131/4-5B2) were generated which metastasize spontaneously to brain parenchyma. This constitutes the first model of heritable spontaneous melanoma brain metastasis by a human cell line from a subdermal transplant, without any therapeutic intervention. Characterization shows two salient functional alterations that may contribute to this phenotype 1) adhesion to brain-endothelial cells and 2) proliferation in the presence of brain-derived factors. When compared to poorly or highly metastatic cell lines (WM239A and 113/6-4L respectively), microarray analysis shows that 4-5B1/B2 cell lines have markedly different expression profiles. These cell lines show differential expression of 108 genes, thirteen of which share a common alteration for both brain-metastatic cell lines, including ednrb (endothelin receptor B) and bcl2a1 (BCL2-related protein A1), which stand out as potentially relevant. These molecules have been previously associated with increased proliferation in the presence of ENT-3; a peptide expressed in the brain, as well as resistance to TNF induced apoptosis and increased metastatic potential. Lentiviral vectors were used to induce stable upregulation of these genes in the otherwise non-brain metastatic parental 113/6-4L cell line. This upregulation mediated an increase in metastatic potential and, in the case of EDNRB, increased intracranial tumor growth. Future efforts will focus on characterizing the alterations in these cell lines, to confirm their clinical relevance and to test novel inhibitors for treating melanoma brain metastases. 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 1452.