Establishment and characterization of models of chemotherapy resistance in colorectal cancer: Towards a predictive signature of chemoresistance

Current standard treatments for metastatic colorectal cancer (CRC) are based on combination regimens with one of the two chemotherapeutic drugs, irinotecan or oxaliplatin. However, drug resistance frequently limits the clinical efficacy of these therapies. In order to gain new insights into mechanisms associated with chemoresistance, and departing from three distinct CRC cell models, we generated a panel of human colorectal cancer cell lines with acquired resistance to either oxaliplatin or irinotecan. We characterized the resistant cell line variants with regards to their drug resistance profile and transcriptome, and matched our results with datasets generated from relevant clinical material to derive putative resistance biomarkers. We found that the chemoresistant cell line variants had distinctive irinotecan- or oxaliplatin-specific resistance profiles, with non-reciprocal cross-resistance. Furthermore, we could identify several new, as well as some previously described, drug resistance-associated genes for each resistant cell line variant. Each chemoresistant cell line variant acquired a unique set of changes that may represent distinct functional subtypes of chemotherapy resistance. In addition, and given the potential implications for selection of subsequent treatment, we also performed an exploratory analysis, in relevant patient cohorts, of the predictive value of each of the specific genes identified in our cellular models.

Purification and characterization of bioactive his6-tagged recombinant human tissue inhibitor of metalloproteinases-1 (TIMP-1) protein expressed at high yields in mammalian cells

Tissue inhibitor of metalloproteinases-1 (TIMP-1) is an endogenous inhibitor of matrix metalloproteinases (MMPs) with reported tumor promoting, as well as inhibitory, effects. These paradoxical properties are presumably mediated by different biological functions, MMP-dependent as well as -independent, and probably related to TIMP-1 levels of protein expression, post-translational modifications, and cellular localization. TIMP-1 is an N-glycosylated protein that folds into two functional domains, a C- and an N-terminal domain, with six disulfide bonds. Furthermore, TIMP-1 is processed in the N-terminal sequence. These three biochemical properties make TIMP-1 difficult to produce in conventional bacterial, insect, or yeast expression systems. We describe here a HEK293 cell-based strategy for production and purification of secreted and N-glycosylated recombinant his6-tagged human TIMP-1 (his6-rTIMP-1), which resulted in large amounts of highly purified and bioactive protein. Matrix-assisted laser desorption ionization mass spectrometry confirmed the N- and C-termini of his6-rTIMP-1, and N-glycosylation profiling showed a match to the N-glycosylation of human plasma TIMP-1. The his6-rTIMP-1 was bioactive as shown by its proper inhibitory effect on MMP-2 activity, and its stimulatory effect on cell growth when added to the growth medium of four different breast cancer cell lines. This study provides an easy set-up for large scale production and purification of bioactive, tagged recombinant human TIMP-1, which structurally and functionally is similar to endogenous human TIMP-1, while using an expression system that is adaptable to most biochemical and biomedical laboratories including those that do not perform protein purifications routinely.

One-dimensional isoelectric focusing and immunoblotting of bovine major histocompatibility complex (BoLA) class I molecules and correlation with class I serology

One-dimensional isoelectric focusing followed by immunoblotting and development of the immunoblots with the monoclonal antibody HC-10, raised against denatured HLA class I heavy chains, was used to demonstrate biochemical variation in cattle MHC (BoLA) class I molecules. The bands obtained correlated well with BoLA-A specificities. Two or three bands were identified for the specificities w7, w8, w16, w18, w21, cph43 and cph49, whereas no bands were observed for the specificity w2. Two serologically indistinguishable subtypes of specificity w18 were identified.

Reactivity of monoclonal antibodies to human CD antigens with cells from mink

Three hundred and seventy six monoclonal antibodies (mAbs) raised against human leukocyte surface antigens were analyzed by flow cytometry for cross reactivities against mink leukocytes. We found 53 mAbs (14%) to cross react. This study defined cross reactions to the following human markers: CD1a, CD9 (4 mAbs), CD10, CD11a (2 mAbs), CD14 (3 mAbs), CD18 (5 mAbs), CD20 (atypical reaction), CD21, CD25 (atypical reaction), CD29 (3 mAbs), CD32, CD41, CD42a, CD44 (4 mAbs), CD45, CD45RO, CD47 (2 mAbs), CD49d (3 mAbs), CD61 (2 mAbs), CD62P, CD66abcd, CD71, CD75s, CD79b (2 mAbs), CD86, CD88, CD104 (atypical reaction), CD172a, CD236R (glycophorin C, (atypical reaction)), Xg(a) carbohydrate antigen, Rhesus antigen and two unspecified PAN-reactive mAbs. In order to characterize the molecular mass of the corresponding cross reacting mink markers, the mAbs were used to immunoprecipitate the surface antigens. Fourteen mAbs out of the 53 mAbs reactive with mink leukocytes gave reproducible IP findings. The masses of the precipitated antigens were generally in good agreement with those of the homologous human markers. We also performed immunohistochemical staining analyses on formalin fixed, paraffin embedded mink tissue from lymph node and spleen, and found 7 out of 22 mAbs to give a positive signal. Generally, the immunohistological analyses resulted in expected staining patterns.

Porcine ecto-nucleotide pyrophosphatase/phosphodiesterase 1 (NPP1/CD203a): cloning, transcription, expression, mapping, and identification of an NPP1/CD203a epitope for swine workshop cluster 9 (SWC9) monoclonal antibodies

Swine workshop cluster 9 (SWC9) antibody identifying a porcine epitope on macrophages and thymocytes was used to precipitate and characterize the molecule from biotinylated macrophages and to obtain peptide sequence by mass spectrometry. The protein was identified as ecto-nucleotide pyrophosphatase/phosphodiesterase 1 (NPP1/CD203a). The porcine NPP1/CD203a encoding gene was mapped to chromosome 1 using a radiation hybrid panel, and transcription was investigated by RT-PCR analysis of several tissues. The cDNA was cloned and introduced into COS7 cells resulting in expression of functionally active enzyme and verification of the specificity of an SWC9 reacting monoclonal antibody. The antibody was used for immunohistochemical examination of various porcine tissues. Most prominent expression of NPP1/CD203a was found in lung macrophages and liver sinusoids.

Influence of routes and administration parameters on antibody response of pigs following DNA vaccination

Using the nucleoprotein of porcine reproductive and respiratory syndrome virus as model antigen, we optimised parameters for gene gun vaccination of pigs, including firing pressure and vaccination site. As criteria for optimisation, we characterised particle penetration and local tissue damage by histology. For selected combinations, vaccination efficiency in terms of antibody response was studied. Gene gun vaccination on ear alone was as efficient as a multi-site (ear, thorax, inguinal area, tongue mucosa) gene gun approach, and more efficient than combined intramuscular (i.m.)/intradermal (i.d.) injection of plasmid DNA. This indicates, that the ear is an attractive site for gene gun vaccination of pigs.

An experimental infection model for reproduction of calf pneumonia with bovine respiratory syncytial virus (BRSV) based on one combined exposure of calves

Bovine respiratory syncytial virus (BRSV) has been recognised as an important pathogen in calf pneumonia for 30 years, but surprisingly few effective infection models for studies of the immune response and the pathogenesis in the natural host have been established. We present a reproducible experimental infection model for BRSV in 2-5-month-old, conventionally reared Jersey calves. Thirty-four colostrum-fed calves were inoculated once by aerosol and intratracheal injection with BRSV. Respiratory disease was recorded in 91% of the BRSV-inoculated calves, 72% had an accompanying rise in rectal temperature and 83% exhibited >5% consolidation of the lung tissue. The disease closely resembled natural outbreaks of BRSV-related pneumonia, and detection of BRSV in nasal secretions and lung tissues confirmed the primary role of BRSV. Nine mock-inoculated control calves failed to develop respiratory disease. This model is a valuable tool for the study of the pathogenesis of BRSV and for vaccine efficacy studies.

Replication and clearance of respiratory syncytial virus: apoptosis is an important pathway of virus clearance after experimental infection with bovine respiratory syncytial virus

Human respiratory syncytial virus is an important cause of severe respiratory disease in young children, the elderly, and in immunocompromised adults. Similarly, bovine respiratory syncytial virus (BRSV) is causing severe, sometimes fatal, respiratory disease in calves. Both viruses are pneumovirus and the infections with human respiratory syncytial virus and BRSV have similar clinical, pathological, and epidemiological characteristics. In this study we used experimental BRSV infection in calves as a model of respiratory syncytial virus infection to demonstrate important aspects of viral replication and clearance in a natural target animal. Replication of BRSV was demonstrated in the luminal part of the respiratory epithelial cells and replication in the upper respiratory tract preceded the replication in the lower respiratory tract. Virus excreted to the lumen of the respiratory tract was cleared by neutrophils whereas apoptosis was an important way of clearance of BRSV-infected epithelial cells. Neighboring cells, which probably were epithelial cells, phagocytized the BRSV-infected apoptotic cells. The number of both CD4(+) and CD8+ T cells increased during the course of infection, but the T cells were not found between the epithelial cells of the bronchi up until apoptosis was no longer detected, thus in the bronchi there was no indication of direct contact-dependent T-cell-mediated cytotoxicity in the primary infection.

The acute phase response of haptoglobin and serum amyloid A (SAA) in cattle undergoing experimental infection with bovine respiratory syncytial virus

The ability of a pure virus infection to induce an acute phase protein response is of interest as viral infections are normally considered to be less efficient in inducing an acute phase protein response than bacterial infections. This was studied in a bovine model for infection with bovine respiratory syncytial virus (BRSV), analysing the induction of the two most dominant bovine acute phase proteins haptoglobin and serum amyloid A (SAA). Strong and reproducible acute phase responses were detected for both proteins, peaking at around 7-8 days after inoculation of BRSV, while no response was seen in mock-inoculated control animals. The serum concentrations reached for SAA and haptoglobin during the BRSV-induced acute phase response were generally the same or higher than previously reported for bacterial infections in calves. The magnitude and the duration of the haptoglobin response was found to correlate well with the severity of clinical signs (fever) and with the extent of lung consolidation while SAA responded most rapidly to infection.

Extensive sequence divergence among bovine respiratory syncytial viruses isolated during recurrent outbreaks in closed herds

The nucleotides coding for the extracellular part of the G glycoprotein and the full SH protein of bovine respiratory syncytial virus (BRSV) were sequenced from viruses isolated from numerous outbreaks of BRSV infection. The isolates included viruses isolated from the same herd (closed dairy farms and veal calf production units) in different years and from all confirmed outbreaks in Denmark within a short period. The results showed that identical viruses were isolated within a herd during outbreaks and that viruses from recurrent infections varied by up to 11% in sequence even in closed herds. It is possible that a quasispecies variant swarm of BRSV persisted in some of the calves in each herd and that a new and different highly fit virus type (master and consensus sequence) became dominant and spread from a single animal in connection with each new outbreak. Based on the high level of diversity, however, the most likely explanation was that BRSV was (re)introduced into the herd prior to each new outbreak. These findings are highly relevant for the understanding of the transmission patterns of BRSV among calves and human respiratory syncytial virus among humans.

Increased pulmonary secretion of tumor necrosis factor-alpha in calves experimentally infected with bovine respiratory syncytial virus

Bovine respiratory syncytial virus (BRSV) is an important cause of respiratory disease among calves in the Danish cattle industry. An experimental BRSV infection model was used to study the pathogenesis of the disease in calves. Broncho alveolar lung lavage (BAL) was performed on 28 Jersey calves, of which 23 were experimentally infected with BRSV and five were given a mock inoculum. The presence of the cytokine tumor necrosis factor alpha (TNF-alpha) in the BAL fluids was detected and quantified by a capture ELISA. TNF-alpha was detected in 21 of the infected animals. The amount of TNF-alpha in the BAL fluid of calves killed post inoculation day (PID) 2 and 4 was at the same very low level as in the uninfected control animals. Large amounts of TNF-alpha were detected on PID 6, maximum levels of TNF-alpha were reached on PID 7, and smaller amounts of TNF-alpha were seen on PID 8. The high levels of TNF-alpha appeared on the days where severe lung lesions and clinical signs were obvious and the amounts of BRSV-antigen were at their greatest. Although Pasteurellaceae were isolated from some of the BRSV-infected calves, calves treated with antibiotics before and through the whole period of the infection, as well as BRSV-infected calves free of bacteria reached the same level of TNF-alpha as animals from which bacteria were isolated from the lungs. It is concluded that significant quantities of TNF-alpha are produced in the lungs of the calves on PID 6-7 of BRSV infection. The involvement of TNF-alpha in the pathogenesis of, as well as the anti-viral immune response against, BRSV infection is discussed.

Antibody dynamics in BRSV-infected Danish dairy herds as determined by isotype-specific immunoglobulins

Using specific ELISAs, antibody levels of four different isotypes to bovine respiratory syncytial virus (BRSV) were determined in calves, following experimental BRSV infection. Most calves experienced an increase in the specific IgM and IgG1 titres about 6-10 days after infection with BRSV. The IgM titre was transient showing positive titres for only 5-10 days, while specific IgG1 was present for a longer time. IgA was detected concomitantly with IgM but at a lower level. Production of IgG2 anti-BRSV antibodies was detected from 3 weeks after infection. In two closed herds, repeated blood samplings were performed on young stock to analyse maternal immunity. The passively transferred antibodies were mainly of the IgG1 isotype and the half-life of IgG1 to BRSV was estimated to be 26.6 days. One of the herds had an outbreak of enzootic pneumonia, diagnosed to be caused by BRSV. Furthermore, another herd with acute BRSV was followed by weekly blood samples in six calves; in both herds IgM and IgG1 was detected shortly after the appearance of clinical signs. Serum samples from 50 Danish dairy herds (453 samples) were tested for immunoglobulins of the isotypes IgG1, IgG2 and IgM. The presence of antibodies to BRSV was widespread and more than 54% of the samples had BRSV antibodies of both the IgG1 and IgG2 isotypes indicating a high herd prevalence to BRSV. Test samples from two herds out of 50 were free from all isotypes to BRSV.

Diagnosis of enzootic pneumonia in Danish cattle: reverse transcription-polymerase chain reaction assay for detection of bovine respiratory syncytial virus in naturally and experimentally infected cattle

A reverse transcription-polymerase chain reaction (RT-PCR) assay was developed for detection of bovine respiratory syncytial virus (BRSV) in lung tissue of naturally and experimentally infected cattle. Primers were selected from the gene coding the F fusion protein, which is relatively conserved among BRSV isolates. The RT-PCR assay was highly specific, it yielded positive reactions only when performed on BRSV-infected cell cultures or tissues. The detection limit of the RT-PCR assay was assessed as 5 TCID50. BRSV was detected in tissues of the respiratory tract and in the tracheobroncheal lymph node of calves euthanized 2-8 days after experimental infection with BRSV, whereas samples of other tissues and samples from mock-infected animals were negative at all time points. Examination of lung samples from 8 different regions of the lungs revealed that although the virus was most often found in the cranioventral lobules, it was frequently present in all lung lobules. Microbiologic examinations of all acute fatal cases of pneumonia (135 animals) in cattle submitted for diagnostic purposes during 1 year revealed that Actinomyces pyogenes (11%), Haemophilus somnus (10%), Pasteurella sp. (7%), and Pasteurella haemolytica (7%) were the most common bacterial agents found in the lungs. BRSV was identified using a conventional antigen enzyme-linked immunosorbent assay (ELISA) in 23 (17%) animals. The established BRSV-specific RT-PCR assay yielded positive results for the same 23 animals. In addition, 10 animals that were negative with the ELISA were positive with the RT-PCR assay. These results indicates that the RT-PCR assay can be a sensitive, reliable alternative to conventional diagnostic procedures.

Serological and genetic characterisation of bovine respiratory syncytial virus (BRSV) indicates that Danish isolates belong to the intermediate subgroup: no evidence of a selective effect on the variability of G protein nucleotide sequence by prior cell culture adaption and passages in cell culture or calves

Danish isolates of bovine respiratory syncytial virus (BRSV) were characterised by nucleotide sequencing of the G glycoprotein and by their reactivity with a panel of monoclonal antibodies (MAbs). Among the six Danish isolates, the overall sequence divergence ranged between 0 and 3% at the nucleotide level and between 0 and 5% at the amino acid level. Sequence divergences of 7-8%, 8-9% and 2-3% (nucleotide) and 9-11%, 12-16% and 4-6% (amino acid) were obtained in the comparison made between the group of Danish isolates and the previously sequenced 391-2USA, 127UK and 220-69Bel isolates, respectively. Phylogenetic analysis showed that the Danish isolates formed three lineages within a separate branch of the phylogenetic tree. Nevertheless, the Danish isolates were closely related to the 220-69Bel isolate, the prototype of the intermediate antigenic subgroup. The sequencing of the extracellular part of the G gene of additional 11 field BRSV viruses, processed directly from lung samples without prior adaption to cell culture growth, revealed sequence variabilities in the range obtained with the propagated virus. In addition, several passages in cell culture and in calves had no major impact on the nucleotide sequence of the G protein. These findings indicated that the previously established variabilities of the G protein of RS virus isolates were not attributable to mutations induced during the propagation of the virus. The reactivity of the Danish isolates with G protein-specific MAbs were similar to that of the 220-69Bel isolate. Furthermore, the sequence of the immunodominant region was completely conserved among the Danish isolates on one side and the 220-69Bel isolate on the other. When combined, these data strongly suggested that the Danish isolates belong to the intermediate subgroup.

Sites of replication of bovine respiratory syncytial virus in naturally infected calves as determined by in situ hybridization

Replication of bovine respiratory syncytial virus (BRSV) was studied in three naturally infected calves by in situ hybridization using strand-specific RNA probes. One of the calves was a 5-month-old Friesian, the other two calves were a 3-month-old and a 3-week-old Jersey. Two Jersey calves, 3 months and 3 weeks of age, served as controls. Replication of BRSV took place in the luminal lining of the respiratory tract. In one of the BRSV infected animals (calf No. 1), replication was especially seen in the bronchi, whereas in the two other animals (calf Nos. 2 and 3) replication of BRSV was demonstrated in the bronchiolar epithelial cells and in alveolar cells. Syncytia were often observed in the bronchiolar walls and in alveoli and such syncytia were always replicating BRSV. By immunohistochemistry it was possible to demonstrate BRSV antigen at the same location as replication of BRSV was detected. In tissue outside the respiratory tract neither BRSV antigen nor replication of BRSV could be demonstrated.

Role of alveolar type II cells and of surfactant-associated protein C mRNA levels in the pathogenesis of respiratory distress in mink kits infected with Aleutian mink disease parvovirus

Neonatal mink kits infected with Aleutian mink disease parvovirus (ADV) develop an acute interstitial pneumonia with clinical symptoms and pathological lesions that resemble those seen in preterm human infants with respiratory distress syndrome and in human adults with adult respiratory distress syndrome. We have previously suggested that ADV replicates in the alveolar type II epithelial cells of the lung. By using double in situ hybridization, with the simultaneous use of a probe to detect ADV replication and a probe to demonstrate alveolar type II cells, we now confirm this hypothesis. Furthermore, Northern (RNA) blot hybridization showed that the infection caused a significant decrease of surfactant-associated protein C mRNA produced by the alveolar type II cells. We therefore suggest that the severe clinical symptoms and pathological changes characterized by hyaline membrane formation observed in ADV-infected mink kits are caused by a dysfunction of alveolar surfactant similar to that observed in respiratory distress syndrome in preterm infants. However, in the infected mink kits the dysfunction is due to the replication of ADV in the lungs, whereas the dysfunction of surfactant in preterm infants is due to lung immaturity.

Comparison of promoter activity in Aleutian mink disease parvovirus, minute virus of mice, and canine parvovirus: possible role of weak promoters in the pathogenesis of Aleutian mink disease parvovirus infection

Aleutian mink disease parvovirus (ADV) infection causes both acute and chronic disease in mink, and we have previously shown that it is the level of viral gene expression that determines the disease pattern. To study the gene regulation of ADV, we have cloned the P3 ADV and P36 ADV promoters in front of a reporter gene, the chloramphenicol acetyltransferase (CAT) gene, and analyzed these constructs by transient transfection in a feline kidney cell line and mouse NIH 3T3 cells. The genes for ADV structural proteins (VP1 and VP2) and the nonstructural proteins (NS-1, NS-2, and NS-3) were cloned into a eukaryotic expression vector, and their functions in regulation of the P3 ADV and P36 ADV promoters were examined in cotransfection experiments. The ADV NS-1 protein was able to transactivate the P36 ADV promoter and, to a lesser degree, the P3 ADV promoter. Constitutive activities of the P3 ADV and P36 ADV promoters were weaker than those of the corresponding promoters from the prototypic parvovirus minute virus of mice (MVM) and canine parvovirus (CPV). Also, the level of transactivation of the P36 ADV promoter was much lower than those of the corresponding P38 MVM and P38 CPV promoters transactivated with MVM NS-1. Moreover, the ADV NS-1 gene product could transactivate the P38 MVM promoter to higher levels than it could transactivate the P36 ADV promoter, while the P36 ADV promoter could be transactivated by MVM NS-1 and ADV NS-1 to similar levels. Taken together, these data indicated that cis-acting sequences in the P36 ADV promoter play a major role in determining the low level of transactivation observed. The P3 ADV and P4 MVM promoters could be transactivated to some degree by their respective NS-1 gene products. However, in contrast to the situation for the late promoters, switching NS-1 proteins between the two viruses was not possible. This finding may indicate a different mechanism of transactivation of the early promoters (P3 ADV and P4 MVM) compared with the late (P36 ADV and P38 MVM) promoters. In summary, the constitutive levels of expression from the ADV promoters are weaker than the levels from the corresponding promoters of MVM and CPV. Moreover, the level of NS-1-mediated transactivation of the late ADV promoter is impaired compared with the level of transactivation of the late promoters of MVM and CPV.(ABSTRACT TRUNCATED AT 400 WORDS)

Identification of alternatively spliced mRNAs encoding potential new regulatory proteins in cattle infected with bovine leukemia virus

The polymerase chain reaction was used to detect and characterize low-abundance bovine leukemia virus (BLV) mRNAs. In infected cattle we could detect spliced mRNA with a splice pattern consistent with a Tax/Rex mRNA, as well as at least four alternatively spliced RNAs. Two of the alternatively spliced mRNAs encoded hitherto unrecognized BLV proteins, designated RIII and GIV. The Tax/Rex and alternatively spliced mRNAs could be detected at their highest levels in BLV-infected cell cultures; the next highest levels were found in samples from calves experimentally infected at 6 weeks postinoculation. Alternatively spliced mRNAs were also expressed, albeit at lower levels, in naturally infected animals; they were detected by a nested polymerase chain reaction. Interestingly, the GIV mRNA was specifically detected in naturally infected cows with persistent lymphocytosis and in two of five calves at 6 months after experimental infection with BLV. Furthermore, the calf with the strongest signal for GIV had the highest lymphocyte counts. These data may suggest a correlation between expression of the GIV product and development of persistent lymphocytosis. Some of the donor and acceptor sites in the alternatively spliced mRNAs were highly unusual. The biological mechanisms and significance of such a choice of unexpected splice sites are currently unknown.

Characterization of early pathogenic effects after experimental infection of calves with bovine immunodeficiency-like virus

The early pathogenic effects of bovine immunodeficiency-like virus (BIV) were studied in calves experimentally inoculated with BIV. All animals inoculated with BIV R29-infected cells seroconverted by 6 weeks postinoculation, and BIV was recoverable from each animal at 2 weeks postinoculation. However, levels of BIV replication in vivo appeared to be low. In situ hybridization studies indicated that during peak periods of viral replication in vivo, less than 0.03% of peripheral blood mononuclear cells were expressing detectable levels of viral RNA. Moreover, the levels of viral RNA in these cells in vivo were less than 1/10 the levels observed in persistently infected cells in vitro. BIV-inoculated calves had significantly higher numbers of circulating lymphocytes, and follicular hyperplasia was observed in lymph nodes, hemal nodes, and spleen. The histopathological changes observed in BIV-infected calves were similar to changes found early after infection with the immunosuppressive lentiviruses, including human immunodeficiency virus type 1.