A genetic analysis of the adenine phosphoribosyl transferase locus in Chinese hamster V79-AP4 cells: relevance to mutagenesis studies

The chromosomal location of the autosomal locus aprt has been investigated in the permanent Chinese hamster cell line V79-AP4 by standard somatic cell genetics methodologies. Aprt is functionally dizygous in V79-AP4 and the 2 alleles map on 2 chromosome 3 homologs, in agreement with the chromosome assignment of the gene in Chinese hamster primary cells. Chromosome G-banding and a Southern blot analysis of V79-AP4 DNA, using as a probe the cloned Chinese hamster aprt gene, have not revealed any structural alteration at either of the 2 aprt alleles. One of the chromosomes 3 has, however, a terminal deletion in its long arm and is therefore morphologically marked. These findings could make V79-AP4 an interesting cell system for the study of mutational mechanisms at the aprt locus in Chinese hamster.     

Differential expression and function of breast regression protein 39 (BRP-39) in murine models of subacute cigarette smoke exposure and allergic airway inflammation

Background

While the presence of the chitinase-like molecule YKL40 has been reported in COPD and asthma, its relevance to inflammatory processes elicited by cigarette smoke and common environmental allergens, such as house dust mite (HDM), is not well understood. The objective of the current study was to assess expression and function of BRP-39, the murine equivalent of YKL40 in a murine model of cigarette smoke-induced inflammation and contrast expression and function to a model of HDM-induced allergic airway inflammation.

Methods

CD1, C57BL/6, and BALB/c mice were room air- or cigarette smoke-exposed for 4 days in a whole-body exposure system. In separate experiments, BALB/c mice were challenged with HDM extract once a day for 10 days. BRP-39 was assessed by ELISA and immunohistochemistry. IL-13, IL-1R1, IL-18, and BRP-39 knock out (KO) mice were utilized to assess the mechanism and relevance of BRP-39 in cigarette smoke- and HDM-induced airway inflammation.

Results

Cigarette smoke exposure elicited a robust induction of BRP-39 but not the catalytically active chitinase, AMCase, in lung epithelial cells and alveolar macrophages of all mouse strains tested. Both BRP-39 and AMCase were increased in lung tissue after HDM exposure. Examining smoke-exposed IL-1R1, IL-18, and IL-13 deficient mice, BRP-39 induction was found to be IL-1 and not IL-18 or IL-13 dependent, while induction of BRP-39 by HDM was independent of IL-1 and IL-13. Despite the importance of BRP-39 in cellular inflammation in HDM-induced airway inflammation, BRP-39 was found to be redundant for cigarette smoke-induced airway inflammation and the adjuvant properties of cigarette smoke.

Conclusions

These data highlight the contrast between the importance of BRP-39 in HDM- and cigarette smoke-induced inflammation. While functionally important in HDM-induced inflammation, BRP-39 is a biomarker of cigarette smoke induced inflammation which is the byproduct of an IL-1 inflammatory pathway.     

Matrigel invasion by the prostate cancer cell lines, PC3 and DU145, and cathepsin L+B activity.

Cathepsins L and B are lysosomal cysteine proteinases whose activities and cellular location are altered in many types of cancers and cancer cell lines. Cathepsins L and B play an unspecified role in cancer invasion and metastasis. The purpose of our study was to determine whether cathepsins L and B are important for the ability of two prostate cancer cell lines, PC3 and DU 145, to invade the basement membrane-like preparation, Matrigel. Exposure of PC3 and DU145 to the irreversible cysteine proteinase inhibitor, E64, decreases the invasive ability of DU145, but not PC3. PC3 and DU145 were treated with the phorbol ester analogue, phorbol 12-myristate 13-acetate (PMA), a known tumor promoter that activates protein kinase C and contributes to the metastatic phenotype. PMA increased secreted cathepsin L+B activity and the invasive ability of PC3 and DU145; co-exposure to E64 and PMA decreased both cathepsin L+B activity and invasion. We conclude that DU145 requires cathepsin L+B activity more than PC3 for the invasion of the Matrigel. When the amount of secreted cathepsin L+B activity is increased by PMA treatment, however, PC3 becomes dependent on cathepsin L+B for invasion. Our study demonstrates that modulation of the amount of secreted cathepsin L+B activity influences the invasive phenotype of PC3 and DU145.     

QuantiSNP: an Objective Bayes Hidden-Markov Model to detect and accurately map copy number variation using SNP genotyping data

Array-based technologies have been used to detect chromosomal copy number changes (aneuploidies) in the human genome. Recent studies identified numerous copy number variants (CNV) and some are common polymorphisms that may contribute to disease susceptibility. We developed, and experimentally validated, a novel computational framework (QuantiSNP) for detecting regions of copy number variation from BeadArray SNP genotyping data using an Objective Bayes Hidden-Markov Model (OB-HMM). Objective Bayes measures are used to set certain hyperparameters in the priors using a novel re-sampling framework to calibrate the model to a fixed Type I (false positive) error rate. Other parameters are set via maximum marginal likelihood to prior training data of known structure. QuantiSNP provides probabilistic quantification of state classifications and significantly improves the accuracy of segmental aneuploidy identification and mapping, relative to existing analytical tools (Beadstudio, Illumina), as demonstrated by validation of breakpoint boundaries. QuantiSNP identified both novel and validated CNVs. QuantiSNP was developed using BeadArray SNP data but it can be adapted to other platforms and we believe that the OB-HMM framework has widespread applicability in genomic research. In conclusion, QuantiSNP is a novel algorithm for high-resolution CNV/aneuploidy detection with application to clinical genetics, cancer and disease association studies.     

Immune responses to the HLA-A*0201-restricted epitopes of tyrosinase and glycoprotein 100 enable control of melanoma outgrowth in HLA-A*0201-transgenic mice.

Many of the Ags recognized by human melanoma-reactive CTL are derived from proteins that are also expressed in melanocytes. The possibility of self-tolerance to these epitopes has led to questions about their utility for antitumor immunotherapy. To investigate the issue, we established a preclinical model based on transgenic mice expressing a recombinant HLA-A*0201 molecule and B16 melanoma transfected to express this molecule. HLA-A*0201-restricted epitopes from the melanocyte differentiation proteins (MDP) tyrosinase and gp100 are expressed in both tumor cells and melanocytes, and the former is associated with self-tolerance. However, adoptive transfer of tyrosinase or gp100-reactive CTL developed from tolerant mice delayed tumor outgrowth, as did immunization with MDP peptide-pulsed dendritic cells. Protection was enhanced by the use of peptide ligands containing conservative substitutions that were cross-reactive with the original Ags. These data establish that CTL populations reactive against MDP-derived self-Ags can be activated to mount effective antitumor immunity and strongly support their continued development for tumor immunotherapy in humans.