Mapping of genetic deletions on the long arm of chromosome 22 in human pancreatic adenocarcinomas.

The molecular mechanisms of carcinogenesis in pancreatic cancer are still poorly understood, although the inactivation of tumor suppressor genes at multiple loci is suspected. We investigated the loss of heterozygosity (LOH) on chromosome 22 in pancreatic cancer by means of a PCR-based microsatellite analysis of archival paraffin-embedded histological sections in order to better define deleted region(s) and to test whether the NF-2 gene is involved. Using a panel of thirteen markers that spanned the long arm of chromosome 22, loss of heterozygosity was identified for at least one locus in 37% of investigated pancreatic adenocarcinomas. These deletions are clustered into two separate areas of the chromosome 22--one proximal to the NF-2 gene and one distal. The NF-2 gene itself is not involved. These regions are likely locations of tumor suppressor genes that may contribute to the development of pancreatic cancer.

Early cancer detection by microsatellite marker analysis.

A major goal of tumor biology has been the development of tumor markers that are useful for the diagnosis and management of cancer. A drawback associated with many of these markers is that they are not unique to tumor cells, but rather are normal or developmental antigens which are overexpressed in tumor tissue Therefore, determination of possible malignancy is based on a designated expression level rather than a clear-cut difference. Studies have shown that DNA from tumor cells has a pattern of chromosomal deletion clearly distinguishable from normal cell DNA, and more importantly, DNA from tumor cells can be detected in the serum of cancer patients. Particular chromosomal deletion patterns are associated with specific tumor types. It is hypothesized that individuals at risk for certain genetically well-characterized cancers, could be successfully screened for those cancers by a PCR-based blood test. In this way, neoplasia could be detected at earlier, more treatable stages of development.

Genetic mapping and physical cloning of UVB susceptibility region in mice.

One of the most important goals of cancer research is to identify environmental and host factors that contribute to the malignant state. Human skin cancers are among the few tumor types for which the predominant environmental carcinogen is known. Ultraviolet light, a component of sunlight, is an important cause of skin cancer in humans. In humans and mice, ultraviolet B radiation induces systematic and local immunosuppression. A consequence of that is inappropriate immune surveillance of somatic tissues for evidence of malignantly transformed cells. The impairment of contact hypersensitivity, as it develops early and correlates well with tumor frequency in various mouse strains, has been used for over 15 y as a model of immunologic events occurring in photocarcinogenesis. In mice, as well as in humans, ultraviolet B radiation induced impairment of contact hypersensitivity is not uniform in all individuals; some individuals are susceptible to the deleterious effects of ultraviolet B, whereas others are resistant to ultraviolet B. We have defined the genetic locus responsible for ultraviolet B susceptibility and resistance in mice within the Bat5 and H-2D segment of the mouse chromosome 17.

Sequence analysis and expression of a mouse homolog of human IkappaBL gene.

The family of transcriptional inhibitors, IkappaBLs, are critical to the regulation of cytokine and chemokine production. We have identified the complete cDNA sequence of the mouse IkappabL gene. The predicted 381-amino-acid sequence showed evidence of two ankyrin repeats characteristic of Ikappab family proteins and 92% identity to the IkappaBL human homolog. Although human IkappaBL has been reported to be ubiquitously expressed, here we show that mouse IkappaBL is transcribed in a more tissue-specific manner.

Characterization and sequencing of glutamine synthetase cDNA from liver of the ureotelic gulf toadfish (Opsanus beta).

The hepatic enzyme, glutamine synthetase (GSase) is a pivotal protein in the regulation of urea synthesis in fish. The sequence of the DNA encoding for GSase from liver of the ureotelic gulf toadfish (Opsanus beta) was analyzed through a suite of molecular techniques (including cDNA cloning, RACE PCR, and genomic PCR). An open reading frame (ORF) was identified in the cDNA sequence which codes for a protein of 394 amino acids with high identity (86%) to dogfish shark GSase. In the course of generating a suitable probe, a partial sequence was also obtained for horned shark GSase which also had high identity with the dogfish shark gene (93%). Like the dogfish shark GSase, the toadfish gene has two methionine translation initiation sites; the downstream site apparently codes for a cytoplasmic isozyme, while the upstream site adds an N-terminal peptide leader sequence of 23 amino acids to the 'cytoplasmic' protein. This leader sequence has characteristics consistent with a mitochondrial targeting peptide, including a cleavage recognition motif (Arg-X-Phe) and the apparent ability to form an amphiphathic helix. Northern analysis revealed that there is a single predominant transcript of approximately 2 kb in size. These results are consistent with the interpretation that in the gulf toadfish GSase cytoplasmic and mitochondrial isozymes are coded for by a single gene and mRNA transcript which is differentially translated at either initiation site. These results are discussed in the context of prior results for enzyme kinetic characteristics and urea synthesis/excretion physiology.

Altered binding of the NF-GMa transcription factor is involved in the upregulated production of TNF-alpha by macrophages of mammary tumor bearing mice.

Macrophages from D1-DMBA-3 mammary tumor bearing mice have profound alterations in various functions, i.e. diminished antigen presentation, decreased cytolytic activity and depressed synthesis of IL-12. In contrast, these cells display a significant enhancement in the levels of TNF-alpha, which may be involved in the cachexia observed in animals bearing large mammary tumors. The molecular mechanisms involved in the upregulation of TNF-alpha in macrophages from tumor bearers were investigated. The levels of TNF-alpha RNA were increased in macrophages from tumor bearers, but, this was not due to an increase in the RNA half-life. An analysis of the binding of transcription factors relevant to the TNF-alpha gene regulatory region by electrophoretic mobility shift assays (EMSA) revealed no differences in the binding of any NF-kB complex component between macrophages from normal and tumor bearing mice. Likewise, there were no changes in the binding patterns of SP-1 and NF-Y. In contrast, the binding of the transcription factor, NF-GMa, was altered in macrophages from tumor bearers. Our results and those reported in other models of disease suggest that the excessive production of cytokines in pathological conditions, could be the result of alterations of the production and/or binding of transcription factors.

Down-regulation of IL-12, not a shift from a T helper-1 to a T helper-2 phenotype, is responsible for impaired IFN-gamma production in mammary tumor-bearing mice.

Altered cytokine production has been implicated in the down-regulation of cell-mediated immunity in mice bearing large mammary tumors. In several diseases, an imbalance between helper T lymphocytes Th1 and Th2 and their cytokines has been suggested as a contributing factor. In this study, although IFN-gamma from splenic T cells of D1-DMBA-3 mammary tumor-bearing mice was greatly diminished, other cytokine levels remained unchanged, indicating no clear shift between the Th1, Th2, or Th3 phenotypes. The IFN-gamma levels can be restored in vitro by addition of rIL-12 to cultured splenocytes from tumor bearers. Furthermore, IL-12 production is greatly down-regulated in macrophages from tumor-bearing mice as detected by ELISA, and this correlates with diminished expression of IL-12 p40 chain RNA. The mammary tumor used in our studies produces several factors, including granulocyte macrophage-CSF, PGE2, and phosphatidyl serine, that can affect the immune system. Addition of these tumor-derived factors in vitro to macrophages from normal mice resulted in decreased levels of IL-12 protein in cultures treated with PGE2 or phosphatidyl serine. These results indicate that the down-regulation of T cell-produced IFN-gamma in this tumor model is the result of decreased IL-12 production caused by tumor-derived factors and not a shift from the Th1 to the Th2 phenotype.

Cytokine production by lymphoreticular cells from mammary tumor bearing mice: the role of tumor-derived factors.

Mammary tumor development has multiple effects on the T cell, B cell and macrophage compartments of the hosts as evidenced by the alterations in their phenotype and functions. Cytokines are known to modulate the immune system, thus a study of the production of these factors has great relevance to tumor immunity. Here we present evidence that tumor progression causes a profound dysregulation of the cytokine production by various lymphoreticular cells. Furthermore, the tumors themselves are capable of secreting factors that can directly or indirectly affect the cells of the immune system, thereby resulting in the immunosuppressive and other deleterious effects that favor the progress of the neoplastic disease.