Abstract 2683: Monoclonal antibodies and assays for colorectal cancer monitoring in serum

Colorectal cancer (CRC) is the third most common cancer in both men and women. There were 148,810 new cases and 49,960 deaths anticipated in 2008. The 1-year and 5-year relative survival for CRC patients is 82% and 64% respectively. When CRC is detected early, at a localized stage, the 5-year survival is 90%. However only 39% of CRC are diagnosed at this stage, as only 44% of US adults over 50 undergo the recommended screening.

Our aim is to develop rapid, easy-to-use and cost-effective serum-based immunoassays for CRC surveillance and recurrence monitoring.

We have developed proprietary approaches to the discovery of biomarkers (Bm) using an in-house generated library of monoclonal antibodies (mAb), a large collection of clinical samples from patients with major cancers, and a proprietary multiplex screening platform, known as Matrix Protein Array Technology (MPAT). The MPAT enables us to screen a large number of clinical samples with a large number of antibodies. Briefly, a protein matrix comprising samples from cancer patients, benign and normal controls, is replica printed on the MPAT solid support. Each sample matrix is simultaneously interrogated with a different mAb. mAb-Bm reaction is detected using fluorescence-based Odyssey imaging system (Li-Cor), followed by spot quantification and statistical analysis to select mAb against Bm that are significantly and differentially expressed in cases versus controls.

We have used this approach to identify CRC specific Bm and mAb. We further validated Bm expression by MPAT, using the mAb on tissue protein extracts derived from patients with CRC (173), benign and inflammatory conditions of the colon (23), and normal controls (240). The clinical sample set used also included breast, lung, and ovary cases and controls, amounting to a total of 1329 samples. Some mAb-based Bm showed excellent discriminatory power between cancer and control, with up to 90% sensitivity at 90% specificity, as determined by ROC curves using statistical package GB-STAT (Dynamic Microsystems). Then, immunohistochemistry on in-house and commercial tissue microarrays (75 cases) confirmed cancer specificity, and mAb specifically stained CRC tissues, with membrane, nuclear and cytoplasmic localization. Finally, some candidate Bm appeared to be secreted and overexpressed in CRC patient serum, when tested by Western blot.

From the pool of serum-based Bm, we have developed a pair of capture-detection mAb in an ELISA sandwich assay, and compared performance to a carcinoembryonic antigen (CEA) standard assay. This serum-based immunodiagnostic assay would have tremendous applications in CRC monitoring, whether alone or in combination with CEA.

Note: This abstract was not presented at the AACR 101st Annual Meeting 2010 because the presenter was unable to attend.

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 2683.

New approaches for biomarker discovery in lung cancer

Lung cancer remains the most common cause of cancer death in the US and worldwide. Currently, there is no implemented population-based screening for lung cancer. Of all the markers identified, none have achieved sufficient diagnostic significance to reach clinical application. Here we discuss the status of lung cancer early diagnostics, and the genomic and proteomic approaches currently undertaken for biomarker discovery. We then introduce the ANTIBIOMIX approach that enables high-throughput target discovery by interrogating biological samples using a collection of thousands of polyclonal antibodies. The development of specific and sensitive diagnostic assays using patient's biological fluids, such as sputum and serum, will improve screening, monitoring of disease progression and treatment response, and surveillance for recurrence.

Transgenic mice for interleukin 3 develop motor neuron degeneration associated with autoimmune reaction against spinal cord motor neurons

Interleukin 3 (IL-3) stimulates the proliferation and differentiation of various haematopoietic progenitor cells. Recently, IL-3 and other cytokines were reported to exert a neurotrophic activity and to be associated with neurological disorders, suggesting their complex role in the central nervous system. We now show that overexpression of IL-3 in transgenic mice causes a motor neuron disease with several features of amyotrophic lateral sclerosis and progressive muscular atrophy. These animals exhibit hind limb paralysis at 7 months of age, associated with dendritic and axonal degeneration, loss of motor neurons in the spinal cord, and autoimmune reaction against these cells. We examined the effect of IL-3 on embryonic motor neurons survival in mixed spinal cord cultures. Our results suggest that motor neuronal degeneration is not directly triggered by the high level of expression of IL-3.

Biology and potential strategies for the treatment of GM2 gangliosidoses

The GM2 gangliosidoses are a group of heritable neurodegenerative disorders caused by excessive accumulation of the ganglioside GM2 owing to deficiency in beta-hexosaminidase activity. Tay-Sachs and Sandhoff diseases have similar clinical phenotypes resulting from a deficiency in human hexosaminidase alpha and beta subunits, respectively. The lack of treatment for GM2 gangliosidoses stimulated interest in developing animal models to understand the molecular mechanisms underlying the various forms of this disease and to test new potential therapies. In this review, we discuss the molecular biology of GM2 gangliosidoses and the different strategies that have been tested in animal models for the treatment of this genetic disorder, including gene transfer and cell engraftment of neural stem cells engineered to express the hexosaminidase isoenzymes.

Polyubiquitination and proteasomal degradation of the p185c-erbB-2 receptor protein-tyrosine kinase induced by geldanamycin

Treatment of SKBr3 human breast carcinoma cells with the benzoquinoid ansamycin, geldanamycin, rapidly depletes p185c-erbB-2 protein-tyrosine kinase. Loss of p185c-erbB-2 is initiated by disruption of a heteromeric complex between p185c-erbB-2 and the 94-kDa glucose-regulated protein, GRP94, to which geldanamycin binds avidly. Here we report that within minutes of exposure to geldanamycin, mature p185c-erbB-2 becomes polyubiquitinated. Treatment of cells with the specific proteasome proteolytic inhibitor, lactacystin, blocked geldanamycin-induced degradation of p185c-erbB-2 and enhanced the accumulation of polyubiquitinated p185c-erbB-2. Following geldanamycin and lactacystin treatment, a higher molecular weight form of p185c-erbB-2, which likely represents ubiquitin-p185c-erbB-2 conjugates, was detected by anti-p185c-erbB-2 immunoblotting. Nascent p185c-erbB-2 synthesized in the presence of geldanamycin is incompletely glycosylated and remains sequestered in the endoplasmic reticulum. While this immature form of the protein is not ubiquitinated in the presence of geldanamycin, its marked, drug-induced instability is nonetheless antagonized by lactacystin. Thus, the rapid depletion of mature p185c-erbB-2 caused by geldanamycin and the marked, drug-stimulated decrease in half-life of the newly synthesized protein are both mediated by the proteasome, although only the former phenomenon involves polyubiquitination.

p185erbB2 binds to GRP94 in vivo. Dissociation of the p185erbB2/GRP94 heterocomplex by benzoquinone ansamycins precedes depletion of p185erbB2

Treatment of SKBr3 cells with benzoquinone ansamycins, such as geldanamycin (GA), depletes p185erbB2, the receptor tyrosine kinase encoded by the erbB2 gene. In the same cells, a biologically active benzoquinone photoaffinity label specifically binds a protein of about 100 kDa, and the ability of various GA derivatives to reduce the intracellular level of p185erbB2 correlates with their ability to compete with the photoaffinity label for binding to this protein. In this report, we present evidence that the approximately 100-kDa ansamycin-binding protein is GRP94. Membrane-associated p185erbB2 exists in a stable complex with GRP94. GA binding to GRP94 disrupts this complex, leading to degradation of pre-existing p185erbB2 protein, and resulting in an altered subcellular distribution of newly synthesized p185erbB2.

Contribution of sequence and phosphorothioate content to inhibition of cell growth and adhesion caused by c-myc antisense oligomers

c-myc is overexpressed in glioblastoma multiforme, the most common form of brain tumor. To find a suitable target for in vivo antisense therapy of gliomas, we investigated the biological effects on the human glioma cell line, U87MG, of antisense oligonucleotides targeted against the translation start site of c-myc mRNA. Parameters examined included c-myc protein level, cell proliferation, and cell adhesion to substratum. Oligonucleotides were administered by electroporation as capped phosphorothioates. Antisense oligomers caused a reduction in c-myc protein expression, loss of cell adhesion to plastic, and complete growth inhibition. Various control sequences, including sense, scrambled, and three-base mismatched oligomers, were also tested. Some of the controls retained a dG quartet found in the antisense sequence. Reduction in c-myc protein and cell growth and loss of cell adhesion were specific to the antisense sequence. Surprisingly, fully thioated antisense and scrambled sequences, either containing or lacking a dG quartet, were equally inhibitory to both cell growth and adhesion. Loss of cell adhesion was observed with only phosphorothioate-containing oligomers, not with either their phosphodiester or nuclease-resistant PA congeners, and was completely reversed when cells were plated onto fibronectin. These results demonstrate that a commonly used c-myc antisense oligomer also displays dramatic, sequence- but not antisense-specific effects on cell proliferation and cellular adhesion, depending on the backbone.

Antisense oligonucleotides adsorbed to polyalkylcyanoacrylate nanoparticles specifically inhibit mutated Ha-ras-mediated cell proliferation and tumorigenicity in nude mice

Ras oncogenes owe their transforming properties to single point mutations in the sequence coding for the active site of the p21 protein. These mutations lead to changes in cellular proliferation and induce tumorigenic properties. Point mutations represent a well-defined target for antisense oligonucleotides that can specifically suppress the translation of the targeted mutant mRNA. We show that the stability and cellular disponibility of antisense oligonucleotides can be markedly improved by adsorption to polyalkylcyanoacrylate nanoparticles. Nanoparticle-adsorbed antisense oligonucleotides directed to a point mutation (G-->U) in codon 12 of the Ha-ras mRNA selectively inhibited the proliferation of cells expressing the point-mutated Ha-ras gene at a concentration 100 times lower than free oligonucleotides. In addition they markedly inhibited Ha-ras-dependent tumor growth in nude mice after subcutaneous injection. These experiments show that inhibition of ras oncogenes by antisense oligonucleotides can block tumor development even though ras oncogenic activation might be an early event in tumor progression.

Adsorption of oligonucleotides onto polyisohexylcyanoacrylate nanoparticles protects them against nucleases and increases their cellular uptake

Oligonucleotides can be adsorbed on polyisohexylcyanoacrylate nanoparticles in the presence of hydrophobic quarternary ammonium salts. Oligonucleotides bound to nanoparticles are protected from nuclease attack both in buffer and in cell culture media. Cellular uptake of oligonucleotides is increased when they are adsorbed onto nanoparticles as a result of the capture of nanoparticles by an endocytic phagocytic pathway. Intracellular stability towards nucleolytic degradation is increased in the presence of nanoparticles. These results show that nanoparticles can be considered as convenient carriers for the protection and delivery of oligonucleotides to cells.

An approach for new anticancer drugs: oncogene-targeted antisense DNA

BACKGROUND

Ras oncogenes owe their transforming properties to single point mutations in the sequence coding for the catalytic part of the p21 protein. These mutations lead to changes in cellular proliferation and tumorigenic properties. Point mutations represent a defined target for antisense oligonucleotides which specifically suppress translation of the targeted mRNA. However, the use of oligonucleotides in vivo has, until now, been limited by their instability in serum. NEW TECHNIQUES: Different strategies have been developed to protect the oligonucleotides and increase their transport into the target cell. Linking intercalating agents, hydrophobic groups or polycations to oligonucleotides or encapsulating them in liposomes resulted in a higher resistance to exonucleases and increased oligonucleotide penetration into cells. The stability and cellular uptake of antisense oligonucleotides can also be improved by associating them with polyalkylcyanoacrylate nanoparticles. The polymeric nature renders these small particles more stable than liposomes in biological fluids and during storage.

METHOD

Antisense oligonucleotides directed to the point mutation (G to T) in codon 12 of the Ha-ras mRNA were adsorbed to nanoparticles in the presence of hydrophobic cations.

RESULTS

These stabilized oligonucleotides selectively inhibited the proliferation of cells expressing this point mutation and partially reversed their tumorigenicity in nude mice.

Stability, clearance, and disposition of intraventricularly administered oligodeoxynucleotides: implications for therapeutic application within the central nervous system

We report experiments in the rat demonstrating the feasibility of intraventricular administration of oligodeoxynucleotides (ODNs) as a regional treatment approach to disorders within the central nervous system (CNS). Although we find little intrinsic nuclease activity in cerebrospinal fluid (CSF), phosphodiester ODNs are rapidly degraded by brain-associated alpha-exonuclease activity. Phosphorothioate ODNs, however, appear resistant to degradation in the CNS and, after intraventricular administration, we find they are cleared in a manner consistent with CSF bulk flow. Continuous infusion of ODN at 1.5 nmol/hr by miniosmotic pump can maintain micromolar concentrations of intact phosphorothioate ODN in CSF for at least 1 week without obvious neurologic or systemic toxicity. After infusion, extensive brain penetration and marked cellular uptake, especially by astrocytic cells, is demonstrated.

Effect of over-expression of bacterial ribonuclease H on the utility of antisense MYC oligodeoxynucleotides in the monocytic leukemia cell line U937

RNase H has been clearly implicated in vitro in mediating some antisense effects. In vivo evidence is limited to experiments performed in Xenopus oocytes in which antisense oligonucleotides are microinjected. In other mammalian cell systems scant data have been obtained to support or deny a role for RNase H as an antisense mediator in vivo. These experiments were designed to test the hypothesis that RNase H mediates the MYC antisense-induced reduction in MYC protein observed in the human monocytic leukemia cell line U937. A bacterial RNase H-containing episomal replicon was constructed and stable transfectants were obtained which expressed E coli RNase H in their cytoplasm at a 10-fold higher level than endogenous RNase H. These cells failed to demonstrate heightened sensitivity to MYC antisense (phosphorothioate, end capped and phosphodiester) compared with untransfected or E coli RNase H antisense transfected cells. PCR analysis of each transfectant treated and untreated with MYC antisense failed to demonstrate the appearance of truncated MYC mRNA. These results do not support a role for RNase H in the mediation of MYC antisense-induced MYC protein reduction and growth inhibition in U937 cells.

Polyalkylcyanoacrylate nanoparticles as polymeric carriers for antisense oligonucleotides

Adsorption of oligothymidylates on polyisobutyl- or polyisohexylcyanoacrylate nanoparticles was achieved in the presence of hydrophobic cations such as tetraphenylphosphonium chloride or quaternary ammonium salts. Results suggested that oligonucleotide adsorption on the nanoparticles was mediated by the formation of ion pairs between the negatively charged phosphate groups of the nucleic acid chain and the hydrophobic cations. The adsorption efficiency of oligonucleotide-cation complexes on nanoparticles was found to be highly dependent upon several parameters: oligonucleotide chain length, nature of the cyanoacrylic monomer, hydrophobicity of cations used as ion-pairing agents, and ionic concentration of the medium. Carrier capacity of polyisohexylcyanoacrylate nanoparticles for oligothymidylates (16 nucleotides) complexed with cetyltrimetylammonium bromide in the presence of 0.15 M NaCl was determined to be 5 mumol/g polymer. The in vitro protection of oligothymidylates adsorbed to nanoparticles against degradation by a 3'-exonuclease (snake venom phosphodiesterase) was also demonstrated. These results showed that nanoparticles can be considered as convenient carriers for the protection and delivery of oligonucleotides to cells in culture and for future applications in vivo.