Isolation of genes differentially expressed between the Yoshida sarcoma and long-survival Yoshida sarcoma variants: origin of Yoshida sarcoma revisited

Studies on "Ascites sarcoma"

This review seeks to highlight and celebrate Professor Tomizo Yoshida's famous work on "Establishment and characterization of a rat ascites sarcoma, later named "Yoshida ascites sarcoma". Considering the tremendous contribution of this ascites tumor system to the subsequent promotion of research on cancer biology and cancer chemotherapy, his paper should be regarded as a monumental one in the cancer field. The research was carried out during 1943 and the results were submitted to this Journal in October 1944, when Japan was approaching a debilitating defeat in World War II in August 1945. In 1947, when "Research on Ascites sarcoma" was first comprehensively introduced to researchers in a special lecture at the Annual Meeting of the Japanese Society of Pathology, the whole audience was deeply impressed and was encouraged to resume scientific activity in Japan.

Establishment of a novel specific ELISA system for rat N- and C-ERC/mesothelin. Rat ERC/mesothelin in the body fluids of mice bearing mesothelioma

Mesothelioma is a type of malignant tumor that most commonly arises from the pleural or peritoneal membrane and is usually associated with previous exposure to asbestos. In humans, ERC/mesothelin is expressed on the normal mesothelium and in some cancers such as mesothelioma or ovarian carcinoma. Recently, several enzyme-linked immunosorbent assay (ELISA) systems for ERC/mesothelin have been developed, the reported usefulness of which has been assessed and demonstrated as a diagnostic tool. However, the basic roles or physiological functions of, and relationship between, ERC/mesothelin and asbestos exposure-mediated carcinogenesis remain to be resolved. In order to elucidate the precise mechanism, animal models of mesothelioma are desperately needed. In this study, we consider the development of a novel specific ELISA system for not only rat N-ERC/mesothelin but also C-ERC/mesothelin, and the first data on the presence of rat ERC/mesothelin in the body fluids of rat malignant mesothelioma-bearing nude mice. The transplanted mice have revealed the higher concentrations of rat N-ERC/mesothelin in the blood and ascites than C-ERC/mesothelin. We hope these novel ELISA systems are useful in the rat model system to clarify the mechanism of asbestos-induced carcinogenesis and to develop new effective drugs for mesothelioma.

Hereditary renal carcinogenesis fitting Knudson's two-hit model: genotype, environment, and phenotype

Cancer is a heritable disorder of somatic cells. Environment and heredity both operate in the origin of human cancer. The Eker (Tsc2 gene mutant) rat model of hereditary renal carcinoma (RC) is an example of Mendelian dominantly inherited predisposition to a specific cancer in an experimental animal. To the best of our knowledge, this was the first isolation of a Mendelian dominantly predisposing cancer gene in a naturally occurring animal model. Recently, we discovered a new hereditary renal carcinoma in the rat in Japan, and the rat was named the "Nihon" rat, and its predisposing (Nihon) gene could be a novel renal tumor suppressor gene. We present these unique models, comparing these two predisposing genes (both are located on rat chromosome 10), for the study of problems in carcinogenesis, for instance, species-specific difference in tumorigenesis, cell stage and tissue/cell-type specific tumorigenesis, multistep carcinogenesis, modifier gene(s) in renal carcinogenesis, cancer prevention, and the development of the therapeutic treatments that can be translated to human patients, as well as how environmental factors interact with cancer susceptibility gene(s).

Renal carcinogenesis: genotype, phenotype and dramatype

Cancer is a heritable disorder of somatic cells. Environment and heredity are both important in the carcinogenic process. The Eker rat model of hereditary renal carcinoma (RC) is an example of a Mendelian dominantly inherited predisposition to a specific cancer in an experimental animal. Forty years after the discovery of the Eker rat in Oslo, we and Knudson's group independently identified a germline retrotransposon insertion in the rat homologue of the human tuberous sclerosis (TSC2) gene. To our knowledge, this was the first isolation of a Mendelian dominantly predisposing cancer gene in a naturally occurring animal model. Recently, we discovered a new hereditary renal carcinoma in the rat. This rat was named the "Nihon" rat and its predisposing (Nihon) gene could be a novel renal tumor suppressor gene. This article will review the utility of these unique models for the study of problems in carcinogenesis; e.g., species-specific differences in tumorigenesis, cell stage and tissue/cell-type specific tumorigenesis, multistep carcinogenesis, modifier gene(s) in renal carcinogenesis, cancer prevention and the development of therapeutic treatments which can be translated to human patients, as well as how environmental factors interact with cancer susceptibility gene(s).

Multistep renal carcinogenesis as gene expression disease in tumor suppressor TSC2 gene mutant model — genotype, phenotype and environment

Cancer is an inheritable disorder of somatic cells. Environment and heredity both operate in the origins of human cancer. These environmental and genetic determinants of cancer can be classified into four groups designated "Oncodemes" [1]. Oncodeme 1 is the irreducible "background" level of cancer due to spontaneous mutagenesis. Oncodeme 2 is "environmentally induced" cancer, whose causative agents are chemical carcinogens, radiation and viruses. Oncodeme 3 is basically "environmentally induced" cancer, but there are genetically determined differences among persons, e.g. the activation or inactivation of carcinogenes. Most human cancers are believed to belong to Oncodemes 2 and/or 3 (about 80%), for which the probability of the occurrence of the initial carcinogenic step(s) is increased, although the number of steps is not decreased. Oncodeme 1 would contain the approximately 20% that would remain if "environmentally induced" cancers (Oncodeme 2 and/or 3) were prevented. Lastly, Oncodeme 4 is "hereditary" cancer. Hereditary cancers could prove valuable in elucidating carcinogenesis, even though only a small proportion of cancers belong to this group. Here, we present a unique animal model of Oncodeme 4 for the study of problems in carcinogenesis; e.g. cell stage and tissue/cell-type-specific tumorigenesis, multistep carcinogenesis, species-specific differences in tumorigenesis, modifier gene(s) in renal carcinogenesis and cancer prevention.

Genetic imbalances in preleukemic thymuses

To understand the molecular mechanisms involved in preleukemia, the suppression subtractive hybridization method was used in a murine radiation-induced thymic lymphoma model. Seventeen mRNAs overexpressed in preleukemic thymuses were identified: mouse laminin binding protein (p40/37LBP), E25 protein, Rattus norvegicus clone BB.1.4.1, profilin, poly(A) binding protein (PABP), mouse high mobility group protein 1, topoisomerase I, clusterin, proteasome RC1 subunit, rat prostatein C3 and C1 subunits; two ESTs and four unknown genes. The overexpression of PABP, clusterin, profilin, and the p40/37LBP mRNAs was confirmed in preleukemic thymuses and can be related to some cellular events observed during the preleukemic period, i.e., alterations of cell cycle and apoptosis properties. The p40/37LBP and 67-kDa laminin receptor proteins were upregulated during the preleukemic period. The data suggest that additional studies on p40/37LBP and 67-kDa laminin receptor regulation are required to evaluate their potential role in the lymphoma prevention by TNF-alpha and IFN-gamma.

Mapping and determination of the cDNA sequence of the Erc gene preferentially expressed in renal cell carcinoma in the Tsc2 gene mutant (Eker) rat model

The Eker rat develops hereditary renal carcinomas (RCs) due to two hit mutations of the tumor suppressor gene, Tsc2. We previously identified using representational difference analysis (RDA), four genes that were expressed more abundantly in an Eker rat RC cell line than in normal kidney tissue. One gene, Erc (expressed in renal carcinoma) showed sequence homology to the mouse and human megakaryocyte potentiating factor (MPF)/mesothelin gene. The present study determines the full sequence of the cDNA and the exon-intron structure of the rat Erc gene and maps its locus in the chromosome by fluorescence in situ hybridization. Rat Erc and its human homologue were localized in chromosomes 10q12-21 and 16p13.3, respectively, both of which coincided with the locus of the Tsc2/TSC gene. We also found that Erc was expressed at higher levels in primary RCs compared with the normal kidney of the Eker rat. Erc may be related to carcinogenesis in the Tsc2 gene mutant (Eker) rat model.

Generation of metastatic variants of Eker renal carcinoma cell lines for experimental investigation of renal cancer metastasis

We and others have demonstrated that a mutation in Tsc2 is the rate-limiting step for renal carcinogenesis in the Eker rat model. Although inactivation of Tsc2 results in development of renal tumors, it is not sufficient for metastatic renal cell carcinomas (RCs) in the Eker rat. To investigate the additional genetic event(s) necessary for cancer metastasis, we have established highly metastatic S-Lk9d-SLM cell lines from a non-metastatic RC cell line (Lk9dL) by co-implantation with a foreign body (gelatin sponge). Since these cell lines were remarkably different in metastatic performance (all and none, respectively) despite having the same genetic background, they should be useful experimental tools to investigate metastasis-promoting events in renal carcinogenesis.

Identification of cDNAs induced by the tumor suppressor Tsc2 gene using a conditional expression system in Tsc2 mutant (Eker) rat renal carcinoma cells

Alteration of the rat homologue of the tuberous sclerosis 2 (TSC2) gene is associated with dominantly inherited cancer in the Eker rat model, indicating a tumor suppressor nature. The ability of Tsc2 to activate signal transduction and transcription suggests that genes induced by Tsc2 may mediate its biological roles. Using a subtractive hybridization approach in combination with tetracycline operator systems, we identified a set of downstream genes affected by Tsc2. Regulated expression of wild-type Tsc2 gene in Eker renal carcinomas (RCs) resulted in marked expression of cell arrest or programmed cell-death-related genes and stress-induced genes. Thus, the data suggest that Tsc2 might contribute to regulation of the cell cycle and cell survival.

Expressed genes in interleukin-4 treated B cells identified by cDNA representational difference analysis

Interleukin-4 (IL-4) stimulates B cell growth and differentiation, such as inducing mature B cells to switch to IgG1 and IgE production. To further characterize IL-4 effects on B cells, we used a sensitive PCR-based subtraction approach to isolate genes expressed in IL-4 treated cells. Our approach combined an adaptation of the genomic representational difference analysis (RDA) method to cDNA analysis with a physical separation method (magnetic bead depletion). This cDNA RDA technique allowed us to perform subtraction on the relatively small number of highly, characterized, purified B cells that can be conveniently prepared. In the hopes of removing genes responsible for general cell growth, we subtracted cDNA made from lipopolysaccharide (LPS)-stimulated B cells from cDNA from LPS+IL-4 stimulated B cells. Two rounds of subtraction resulted in greater than 100-fold enhancement of expected IL-4-induced Cgamma1 cDNA. At that point, we cloned this subtraction library and analysed 154 randomly picked clones for sequence similarities. From these clones, 37 individual genes were obtained. Most of these genes (30) could be functionally identified by sequence similarity. These included genes encoding Cgamma1 (1), cytoskeletal components (4) and products involved in DNA replication (3), metabolism (5), signal transduction (4), transcription (4), translation (6) and transport (3). Only 7 genes had no similarity to known sequences in the GenBank, EMBL or Swiss Prot databases. One unknown gene (designated Fig1 for IL-Four Induced Gene 1) and one gene with homology to the human transcription factor E4BP4 were confirmed by Northern blot analysis to be induced 10-20-fold by IL-4 treatment. This list of expressed genes in LPS + IL-4 treated B cells may shed further insight on the action and mechanism of IL-4 stimulation of cells.

In search of differentially expressed genes and proteins

A great challenge for modern cell biology is the successful examination of the co-expression of thousands of genes under physiological or pathological conditions and how the expression patterns define the different states of a single cell, tissue or a microorganism. Gene expression can be analyzed today on a large scale by advanced technical approaches for differential screening of proteins and mRNAs. The identification of differentially expressed mRNAs has been successfully applied to understand gene function and the underlying molecular mechanism(-s) of differentiation, development and disease state. Analysis of gene expression by the systematic mapping of thousands of proteins present in a cell or tissue can be achieved by the use of two-dimensional (2D) gel electrophoresis, quantitative computer image analysis, and protein identification techniques. In this article, we comment on some of these techniques and try to stress their advantages and drawbacks. We show how data from RNA/DNA mapping, sequence information from genome projects and protein pattern profiling can be linked with each other and annotated. These comprehensive approaches permit the study of differential gene and protein expressions in cells or tissues.

Strategies for whole microbial genome sequencing and analysis

The introduction of methods for automated DNA sequence analysis nearly a decade ago, together with more recent advances in the field of bioinformatics, have revolutionized biology and medicine and have ushered in a new era of genomic science, the study of genes and genomes. These new technologies have had an impact on many areas of research, including the association between genes and disease, in DNA-based diagnostics, and in the sequencing of genomes from human and other model organisms. The demonstration in 1995, that automated DNA sequencing methods could be used to decipher the entire genome sequence of a free-living organism, Haemophilus influenzae, was a milestone in both the genomics and microbial fields [1]. Since the first report of the complete sequence of H. influenzae, these methodologies have been adopted by laboratories around the world. The complete genomic sequence of five eubacterial species [1-5], one archaea [6], and the eukaryote, Saccharomyces cerevisiae [7], have been reported in the last 18 months. At the beginning of 1997 more than a dozen microbial genome projects are at or near completion, with many others in progress. It is likely that in the next few years we will see the complete sequence of perhaps as many as 30-40 microbial genomes. In this article, we will review methods for whole genome sequencing and analysis and examine how this information can be exploited to better understand microbial physiology and evolution.

Identification of ErbB3-stimulated genes using modified representational difference analysis

The epidermal growth factor receptor (EGFR) family of tyrosine kinases is involved in the growth of normal and tumour cells. The specific contribution of each of the four family members to these processes remains unclear. In the present study we have used a PCR-based subtractive approach to identify differences in messages induced in response to activation of ErbB3 and EGFR. The approach described is a modification of the representational difference analysis technique adapted for analysis of cDNA, which we have modified to permit identification of differential gene expression using as little as 20 microg of total RNA as the starting material. The mRNA obtained from EGF-stimulated NIH-3T3 cells expressing chimaeric EGFR-ErbB3 receptors provided the tester amplicons (small PCR-amplified fragments) which were subtracted against driver amplicons derived from unstimulated NIH-3T3 cells expressing the EGFR-ErbB3 chimaera or EGF-stimulated NIH-3T3 cells overexpressing the EGFR. A total of 22 different clones were isolated, 90% of which showed increased expression in the tester amplicons. Six of these, corresponding to known DNA sequences, were selected for further Northern blot analysis against total RNA prepared from the starting cell lines. Of these, the gene encoding the protein dlk (or a closely related protein, Pref-1) was identified as being regulated by ErbB3 but not by the EGFR. Other genes appeared to be elevated by both ErbB3 and EGFR, including those encoding c-jun, Ret finger protein (RFP), neuroleukin and amyloid protein precursor. One gene product, TIS11, was identified as being regulated by EGFR but not by ErbB3.

[Regression of Yoshida sarcoma during normoxia and hypoxia after fractionated irradiation]

PURPOSE

Tumor regression is one of the most important factors determinating the tumor control probability after radiotherapy. The changes in the regression of tumors during fractionated radiotherapy and the application of different radioprotectors or radiosensitizers make render to assess their effectivity.

MATERIAL AND METHOD

The effect of hypoxic breathing (8.1% O2) on the tumor regression of Yoshida sarcoma was studied using rats of Wistar strain. Different fractionation schedules were used: 10 x 3 Gy, 6 x 5 Gy and 3 x 10 Gy.

RESULTS

No significant changes in the tumor regression after radiotherapy in any group in any time independent from respiratoric hypoxia were recorded. The tumor regression rate was significantly influenced by treatment schedule (p < 0.0005).

CONCLUSIONS

Our results support the hypothesis of hypoxy-radiotherapy: The acute hypoxic hypoxia, caused due the breathing of hypoxic gas mixture with 8 to 10% oxygen, did not influence the radiation induced tumor regression in animal experiment. For this criterium no protection can be shown. The influence of hypoxy-radiotherapy on the local tumor control is necessary to evaluate in further experiments.

Renal carcinogenesis in the Eker rat

The Eker rat hereditary renal carcinoma is an excellent example of a Mendelian dominant predisposition to a specific cancer in an experimental animal. We recently reported that a germline insertion in the rat homologue of the human tuberous sclerosis (TSC2) gene gives rise to the dominantly inherited cancer in the Eker rat model. The function of the TSC2/Tsc2 gene product (called "tuberine" in the human case) is not yet understood, although it contains a short amino acid sequence homologous to the ras family GTPase-activating proteins (GAP3). In the study, we isolated subtracted cDNA clones having increased expression in Eker renal carcinoma cells, using a modified representational difference analysis method to search for additional genes specifically involved in renal carcinogenesis. Here we identified four genes: the third component of the complement (C3) gene, the fos-related antigen I (fra-1) gene, an unknown gene (designated as being expressed in renal carcinoma: erc) and the calpactine I heavy-chain (Annexin II) gene.