FGFR4 polymorphism, TP53 mutation, and their combinations are prognostic factors for oral squamous cell carcinoma

The genotype of the fibroblast growth factor receptor 4 (FGFR4) gene and TP53 mutation have been reported as prognostic factors for cancers of the head and neck, bladder, breast and colon. To determine whether they are applicable for oral squamous cell carcinoma (OSCC), we investigated these two genes in OSCC samples from 150 patients who had undergone radical surgery and in 100 cancer-free individuals. In OSCC, the FGFR4 Gly388Arg polymorphism and the presence or absence of mutation in TP53 did not show a significant association with the clinicopathological features of the tumors at surgery. However, the FGFR4 Arg388 allele, as well as mutations in TP53, was found to be closely associated with poor prognosis. Moreover, these two parameters synergistically affected the survival of OSCC patients. During 60 months of observation after radical surgery, a majority of patients with homozygous Arg388 FGFR4 plus mutated TP53 died of cancer, whereas >90% patients carrying homozygous Gly388 FGFR4 plus wild-type TP53 survived. Therefore, the FGFR4 Gly388Arg polymorphism and TP53 mutations, as well as their combinations, are excellent predictors of the prognosis for OSCC patients.

Selective loss of resistant alleles at p15INK4B and p16INK4A genes in chemically-induced rat tongue cancers

We previously reported that susceptibility to 4-nitroquinoline 1-oxide (4NQO)-induced tongue cancer in Dark-Agouti (DA) and Wistar/Furth (WF) rats was determined by a number of quantitative trait loci. In this article, we further scrutinized one of the quantitative trait loci at a suggestive level on rat chromosome 5. Analyzing a DNA panel of 130 (DAxWF) F2 rats treated with 4NQO showed a quantitative trait loci, containing p15INK4B and p16INK4A. To study the possible relevance of these genes in the development of tongue cancer, we examined 45 4NQO-induced tongue cancers in 100 (DAxWF) F1 rats for loss of heterozygosity. The incidence of loss of heterozygosity at p15INK4B and p16INK4A genes in large advanced tongue cancers was 37.8% and 40.0%, respectively, and the WF allele was selectively lost. Accumulation of loss of heterozygosity and methylation of the promoter regions in the tumour suppressor genes in advanced tumours suggests that they may play a role in tongue cancer progression.

Quantitative trait loci determining weight reduction of testes and pituitary by diethylstilbesterol in LEXF and FXLE recombinant inbred strain rats

Increasing exposure to environmental endocrine disruptor, xeno-estrogen, is a serious hazard to male reproductive activity. To explore possible genetic control in susceptibility to xeno-estrogen, the weight reduction of testes induced by the continuous administration of a synthetic estrogen, diethylstilbesterol, were investigated by quantitative trait analysis in LEXF and FXLE recombinant inbred strain rats, consisting of 21 independent strains, 9 of their substrains, parental F344/Stm and LE/Stm strains, and (F344 x LE)F1. For the weight of testes, one highly significant quantitative trait locus (QTL) and one significant QTL were mapped on chromosomes 7 and 1, respectively. The QTL on chromosome 7 is closely associated with c-myc. Pituitary weight and serum prolactin were also variable among recombinant inbred strains, but no QTL was detected for them in this study.

A speed congenic rat strain bearing the tongue cancer susceptibility locus Tscc1 from Dark-Agouti rats

We previously reported that Dark-Agouti (DA) rats are highly susceptible to 4-nitroquinoline 1-oxide (4NQO)-induced tongue cancer (TC), whereas Wistar/Furth (WF) rats are barely susceptible. Linkage analysis of reciprocal (DAxWF)F2 rats demonstrated five quantitative trait loci, Tongue squamous cell carcinoma 1-5 (Tscc1-5) determining the size and number of the TCs. The major susceptibility locus Tscc1 is mapped on rat chromosome 19. In the present study, we used a marker-assisted speed congenic procedure to construct WF.DA-Tscc1 (WF-T1D) rats, i.e. WF rats carrying a DA-derived Tscc1 chromosomal segment, and evaluated the effect of a single Tscc1 on 4NQO-induced tongue carcinogenesis. In WF-T1D rats, the incidence, number and size of 4NQO-induced TCs were significantly higher than those in WF rats, indicating that the introgressed segment contains one of the susceptibility loci for 4NQO-induced TCs from DA rats. Detection of a single nucleotide polymorphism in NQO1, one of the Tscc1 candidate genes, enabled us to map NQO1 in the Tscc1 segment between D19Wox8 and D19Wox7 on chromosome 19. Possible relevance of NQO1 polymorphism to TC susceptibility is discussed.

Genetic predisposition to 4NQO-induced tongue carcinogenesis in the rat

OBJECTIVE

This study aims to elucidate the genetic basis of predisposition to 4-nitroquinoline 1-oxide (4NQO)-induced tongue cancers (TCs).

MATERIALS AND METHODS

We have reported that inbred Dark-Agouti (DA) strain rats were highly susceptible to 4NQO-induced TCs, whereas Wistar/Furth (WF) rats were resistant to tongue squamous cell carcinomas induced by oral administration of 4NQO. Using size and number of the tumours as quantitative parameters, responsible host loci were analysed by an interval mapping of F2 intercross of DA and WF given carcinogenic regimen. Also, loss of heterozygosity (LOH) at these loci was analysed in tongue cancers in (DA x WF) F1.

RESULTS

We identified and mapped 5 significant quantitative trait loci (QTL), the Tongue squamous cell carcinoma 1-5 (Tscc1-5), and several other suggestive QTL that determine susceptibility to 4NQO-induced TC. Study of TCs induced in (DA x WF)F1 rats revealed a high frequency of LOH in the chromosomal regions of Tscc2, 3, and 4 and also of suggestive QTL on chromosomes 5 and 6. The fact that LOH was found only in larger TCs indicates that LOH occurred in the process of tumour progression. In most LOH, the allele of the resistant WF strain was lost, suggesting that these loci may encode tumour suppressor genes. In larger TCs, in addition to LOH, point mutations and the methylation of possible candidate genes were accumulated.

CONCLUSION

These observations indicate that the 4NQO-induced TC in the rat is a multifactorial disease of a polygenic trait. This model will be useful to understand the complicated genetic basis of predisposition to oral cancers.

Use of A Standard Strain for External Calibration in Behavioral Phenotyping

The present paper evaluates the inclusion of a standard strain or outbred stock in multi-strain behavioral phenotyping protocols to perform the same role as the external standard in biochemical assay procedures. As potential standards, the F344 inbred strain and an outbred stock of Long Evans were tested with three other inbred strains. To evaluate the influence of rearing conditions on phenotype stability, one group of F344s was born at the University of Tsukuba, another, bred elsewhere and delivered to Tsukuba at 4 weeks of age. All animals were tested in open-field (OF), runway emergence (RE) and digging tests as adults. The results showed no influence of breeding or transportation history on OF and RE behavior of the two F344 groups, while there was evidence that digging behavior may be affected by the different rearing experience. The inclusion of a 'standard strain or stock' in phenotyping protocols involving multiple inbred strains or lines of rats, mice and flies has obvious advantages by providing a reference point for inter-laboratory comparisons. The properties of inbred strains and outbred stocks favorable to their use as standards are discussed.

Expressions of junB and c-fos are enhanced in 4-nitroquinoline 1-oxide-induced rat tongue cancers

Activator protein-1 (AP-1) is a transcription factor activated in many tumors. Using 4-nitroquinoline 1-oxide (4NQO)-induced rat tongue cancers (TC), the present study investigated the expression levels of genes that encode the components of AP-1, the jun gene family (c-jun, junB and junD) and the fos gene family (c-fos, fra-1, fra-2 and fosB). Expression levels of junB and c-fos mRNAs in TC were significantly elevated compared with those in epithelial tissue of control rat tongue, although only c-fos mRNA levels tended to be elevated in dysplastic tongue epithelium. Histologically, all 4NQO-induced rat TC were well-differentiated squamous cell carcinomas. Immunostaining for JunB and c-Fos proteins was positive in the nuclei of tumor cells of all TC. It is noteworthy that JunB was negative, but c-Fos was positive in the dysplastic tongue epithelium of the 4NQO-treated rats. Immunostaining for both proteins was negative in tongue mucosal epithelium of control rats. There were no mutations in the coding regions of either junB or c-fos in all the TC examined. These results suggest the possibility that the expressions of junB and c-fos were enhanced stepwise in 4NQO-induced carcinogenesis of rat tongue, and that the coexpression of JunB and c-Fos might play an important role in the establishment of TC.

Carcinogenesis modifier loci in rat tongue are subject to frequent loss of heterozygosity

Rats of the DA strain are highly susceptible to 4NQO-induced TCs, whereas WF rats are barely susceptible. In (DA x WF)F2 rats, 5 QTL, Tscc1-5, are responsible for most of the phenotypic variations, though they do not account for all of the phenotypic differences between WF and DA rats. Analysis of 40 tongue tumors >5 mm in diameter from (DA x WF)F1 rats for LOH at the Tscc loci revealed a high frequency of LOH in chromosomal regions where the Tscc2, -3 and -4 loci map. In most cases of LOH, the allele of the barely susceptible WF strain was lost, suggesting that these loci in the WF strain encode tumor-suppressor genes. Analysis of the same tumors for somatic mutations in oncogenes indicated frequent alteration of Ha-ras, which maps in the Tscc3 region, but rare mutation of the p15(INK4B) and p16(INK4A) genes or the p53 and Msh2 genes. Frequent LOH was also found on rat chromosomes 5 (RNO5) and 6 (RNO6). Tumors of large size accumulated LOH at multiple loci, suggesting the involvement of Tscc loci in tumor progression.

Failure of ureteric bud invasion: a new model of renal agenesis in mice

FUBI (failure of ureteric bud invasion) is a highly inbred strain of mouse with a high spontaneous incidence of uni- or bilateral renal agenesis (60%). Bilateral renal agenesis is lethal within 2 days after birth. The primary defect of FUBI is failure of the ureteric bud to penetrate into the metanephric mesenchyme at around embryonic day 11, resulting in apoptosis of metanephric cells and leading to renal agenesis on the affected side. The metanephros seemed to be normal because co-culturing of the FUBI metanephros with homologous spinal cord induced differentiation of the rudiment, but co-culturing with the homologous ureteric bud frequently did not. Genetic analysis revealed that more than two genes were involved in this malformation and we mapped one of the modifier loci, fubi1, on chromosome 2, at approximately 65 cM from the centromere. In this region, there are two possible candidate genes, Wilms' tumor 1 and formin, that play important roles in kidney development. Some of formin mutants shared a similar phenotype with FUBI; however, there was no difference in the expression of formin in embryonic kidneys between FUBI and control NFS/N mice. Studies of fubi1 congenic mice indicated that interaction of two or more loci is essential for the FUBI phenotype.

Five quantitative trait loci affecting 4-nitroquinoline 1-oxide-induced tongue cancer in the rat

In our previous study, Dark-Agouti (DA) rats were found to be highly susceptible to 4-nitroquinoline 1-oxide (4NQO)-induced tongue carcinoma (TC), whereas Wistar / Furth (WF) rats were barely susceptible. Interval mapping analysis of reciprocal backcross rats showed two quantitative trait loci (QTL) on rat chromosomes (RNO) 1 and 19. In the present study, a composite interval mapping analysis was applied to 4NQO-induced TC in 130 (DA x WF) F2 rats, demonstrating five independent QTL, Tongue squamous cell carcinoma 1 - 5 (Tscc1 - 5), responsible for phenotypic differences in the size and number of TCs in the two strains. Two of these QTL were mapped on RNO1, and the others were mapped on RNO4, 14, and 19. The DA allele at these loci consistently yielded semidominant susceptibility to TC. Out of the five loci detected in this F2 generation, Tscc1 and 2 were identical to Stc1 and Rtc1 described in our previous study, but the other three were novel. We propose a new nomenclature consistent with their function. Genome-wide screening of the F2 progeny also suggested the presence of three additional QTL on RNO5, 6, and 10. The possible roles of these loci in tongue carcinogenesis are discussed.

Propylnitrosourea-induced T-lymphomas in LEXF RI strains of rats: genetic analysis

Oral administration of propylnitrosourea (PNU) in drinking water induces high incidence of lympho-haemopoietic malignancies in rats. Previously we reported that F344 strain rats were highly susceptible to T-lymphomas, and LE/Stm rats, to erythro- or myeloid leukaemias. For analysis of the genetic factors determining types of diseases, we have established LEXF recombinant inbred strains of rats comprising 23 substrains, each derived from intercross between F344 and LE/Stm rats. Rats of 23 LEXF substrains were given PNU, and the development of tumours was observed. The overall incidence of haemopoietic tumours ranged from 100% to 66.7%, and the fractions of T-lymphomas, from 100% to 4%, showing a continuous spectrum. Based on the genetic profile published as a strain distribution pattern table for the LEXF, we screened the potential quantitative trait loci involved in determination of the types of disease and length of the latency period. Statistical calculation was performed using the Map Manager QT software developed by Manly. Four loci, on chromosome 4, 7, 10 and 18, were suggested to associate with the T-lymphoma susceptibility and three loci, on chromosome 1, 5 and 16, with the length of the latency period. These putative loci were further examined in backcross (F344 x LE)F1 x LE. Among seven loci suggested by the recombinant inbred study, three loci, on chromosome 5, 7 and 10, were significantly associated with T-lymphomas and another locus on chromosome 1, just weakly. These observations indicate that PNU-induced lymphomagenesis is a multifactorial genetic process involving a number of loci linked with susceptibility and resistance.

Quantitative trait loci affecting 4-nitroquinoline 1-oxide-induced tongue carcinogenesis in the rat

The incidence of tongue carcinomas (TCs) induced by oral administration of 4-nitroquinoline 1-oxide in rats is strain dependent. The inbred Dark-Agouti (DA) strain showed a much higher susceptibility to large mass-forming infiltrative TCs than did the Wistar-Furth (WF) strain. Our previous study (M. Kitano et al, Jpn. J. Cancer Res., 87: 1097-1101, 1996) on crosses between these two strains postulated a dominant susceptibility gene in DA and a dominant resistance gene in WF rats. The present study mapped these loci by analyzing the backcrosses to each parent with simple sequence repeat polymorphisms. Five quantitative parameters were analyzed: (a) the number of TCs > 5 mm in diameter; (b) the total number of TCs per rat; (c) the diameter of the largest TCs (DTCmax values); (d) the number of non-TC cancers per rat; and (e) and the number of cancers of any site per rat. All of these parameters were closely correlated (P < 0.0001). DA rats had a semidominant gene (Stc1) favoring the development of 4-nitroquinoline 1-oxide-induced cancers on chromosome 19, closely linked to D19Mit9. Peak linkage was observed 4 cM distal from D19Mit9, with a logarithm of the odds (lod) score of 5.72 for the number of large TCs and 6.08 for the DTCmax. On the other hand, WF rats had a semidominant gene (Rtc1) mapped between D1Mit1 and D1Mit3, approximately 20 cM from D1Mit1, with a peak lod score of 3.30 for both the number of large TCs and the DTCmax. The main effect of Rtc1 seemed to be to reduce the size of the TCs. The action of these genes was dose dependent and cooperative. The final incidence of TC in DA, WF, F1, and backcross rats seemed to be explained by combinations of genotype at these two loci. Possible candidate genes for Stc1 and Rtc1 are discussed.

Isolation of mitochondrial DNA-less mouse cell lines and their application for trapping mouse synaptosomal mitochondrial DNA with deletion mutations

For isolation of mouse mtDNA-less (rho0) cell lines, we searched for various antimitochondrial drugs that were expected to decrease the mtDNA content and found that treatment with ditercalinium, an antitumor bis-intercalating agent, was extremely effective for completely excluding mtDNA in all the mouse cell lines we tested. The resulting rho0 mouse cells were successfully used for trapping the mtDNA of living nerve cells into dividing cultured cells by fusion of the rho0 cells with mouse brain synaptosomes, which represent synaptic endings isolated from nerve cells. With neuronal mtDNA obtained, all of the cybrid clones restored mitochondrial translation activity similarly regardless of whether the mtDNA was derived from young or aged mice, thus at least suggesting that defects in mitochondrial genomes are not involved in the age-associated mitochondrial dysfunction observed in the brain of aged mice. Furthermore, we could trap a very small amount of a common 5823-base pair deletion mutant mtDNA (DeltamtDNA5823) that was detectable by polymerase chain reaction in the cybrid clones. As the amount of mutant mtDNA with large scale deletions was expected to increase during prolonged cultivation of the cybrids, these cells should be available for establishment of mice containing the deletion mutant mtDNA.

The LEXF: a new set of rat recombinant inbred strains between LE/Stm and F344

A new set of rat RI strains consisting of 11 independent strains and 13 of their substrains was established by inbreeding F2 rats between F344/DuCrj and LE/Stm. The strain distribution pattern was examined for 66 microsatellite loci, 8 biochemical genetic markers, 2 histocompatibility loci, and 2 coat color genes. A rat salivary protein gene Spe1 was newly mapped on Chr 1.

To be or not to be a T-lymphomas, that is determined by a dominant gene Tlsm-1 in mouse models

A single dominant gene Tlsm-1 was found to determine the type of spontaneous lymphomas to be T in the cross between AKR/Ms and SL/Kh. Microsatellite analysis mapped Tlsm-1 at the position 61 cM from centromere of Chr. 7. Study of this segment of T-lymphoma prone AKXD Rl strains also showed association of Tlsm-1 with T-lymphomas. On the other hand, lymphoma latency was significantly shorten by a recessive gene lla of SL/Kh. By a quantitative trait analysis, lla was located in class II gene in MHC.

Cloning and characterization of the nucleoredoxin gene that encodes a novel nuclear protein related to thioredoxin

In a yeast artificial chromosome contig close to the nude locus on mouse chromosome 11, we identified a novel gene, nucleoredoxin, that encodes a protein with similarity to the active site of thioredoxins. Nucleoredoxin is conserved between mammalian species, and two homologous genes were found in Caenorhabditis elegans. The nucleoredoxin transcripts are expressed in all adult tissues examined, but restricted to the nervous system and the limb buds in Day 10.5-11.5 embryos. The nucleoredoxin protein is predominantly localized in the nucleus of cells transfected with the nucleoredoxin expression construct. Since the bacterially expressed protein of nucleoredoxin showed oxidoreductase activity of the insulin disulfide bonds with kinetics similar to that of thioredoxin, it may be a redox regulator of the nuclear proteins, such as transcription factors.

Genetic controls of susceptibility and resistance to 4-nitroquinoline 1-oxide-induced tongue carcinomas in rats

We analyzed the incidence of infiltrative mass-type tongue carcinomas (IMTC) induced in 550 rats by continuous oral administration of 0.001% 4-nitroquinoline 1-oxide solution for 180 days. The study included various crosses of susceptible Dark-Agouti rats (DA) and resistant Wistar/Furth rats (WF). DA showed a 93.6% incidence of IMTC measuring more than 5 mm in their largest diameter, while WF showed only a 4% incidence. Reciprocal F1 and F2 hybrids mated by DA and WF showed 47.5% and 45.8% incidences, respectively. Meanwhile, reciprocal backcrossed hybrids to DA and WF showed 73.7%, and 24.6% incidences, respectively. Segregation of the incidences suggests that there are two autosomal dominant genes, one linked to the susceptibility of DA and the other to the resistance of WF.

A quantitative trait locus in major histocompatibility complex determining latent period of mouse lymphomas

The effects of two host genes on retrovirus-induced murine lymphoma were evaluated by studying 114 F2 intercross mice between SL/Kh and AKR/Ms mice. Out of 47 T-lymphoma-bearing F2 mice, 45 had the AKR-derived dominant allele at Tism-1. The length of the lymphoma latent period was not related to type of tumor. Instead, it was significantly shortened by a recessive SL/Kh-derived allele at a major histocompatibility complex (MHC)-linked locus on Chr. 17. A quantitative trait analysis of the latent period yielded a maximal logarithm of likelihood ratio for linkage (LOD) score of 7.06 at a class II gene within MHC. The SL/Kh-derived recessive gene was named lla (lymphoma latency acceleration).

Genetic and epigenetic resistance of SL/Ni mice to lymphomas

The murine spontaneous B lymphoma is etiologically related to the expression of endogenous ecotropic murine leukemia virus (ETV). Although both SL/Kh and SL/Ni mouse strains show a high level of expression of ETV from early in life, the former is a pre-B lymphoma-prone strain and the latter is rather lymphoma-resistant. In order to identify the host background difference related to the lymphomagenesis, we performed a genetic cross study between these two strains. In the reciprocal F1 generation, the length of the lymphoma latent period was slightly but significantly longer in (SL/Ni xSL/Kh)F1 than in (SL/KhxSL/Ni)F1(P < 0.05). The incidence of overall lymphomas and that of acute pre-B lymphomas was lower in (SL/NixSL/Kh)F1 than in (SL/KhxSL/Ni)F1, although the difference was not statistically significant. These observations indicate that an epigenetic maternal resistance mechanism of SL/Ni mice plays a role in the lymphoma resistance. Furthermore, in the backcross combinations without maternal influence of SL/Ni, we observed a genetic mechanism of lymphoma resistance: an SL/Ni-derived recessive lymphoma-resistance gene mapped in the proximal segment of Chr. 4. We named this gene nir-1 (SL/Ni-lymphoma resistance-1). Thus, we have demonstrated epigenetic and genetic mechanisms of lymphoma resistance of the SL/Ni mouse with the high expression of endogenous ETV.

Age-associated changes of mitochondrial translation and respiratory function in mouse brain

We examined age-associated changes of respiratory enzyme activities and protein synthesis in mitochondria isolated from mouse brain with high oxidative activities. Cytochrome c oxidase activity increased unexpectedly with aging, while the mitochondrial translational activities showed two phases of alterations: they increased progressively up to 21 weeks after birth followed by a gradual decrease with aging. Results showed that these changes were not due to the change in mitochondrial DNA (mtDNA) copy number or the accumulation of deletion mutations in mtDNA. These observations suggest that the common feature of age-associated changes in both human and mouse mitochondrial functions is limited to the decrease in mitochondrial translational activity. Therefore, mouse brain can be used as a model to understand the relationships between aging and mitochondrial function by examining the cause of decrease in mitochondrial translation activity.

Immunohistochemical detection of ras p21 oncoprotein in undifferentiated and well-differentiated epithelial carcinomas of the human ovary

Expression of ras p21 oncoproteins in human ovarian carcinomas was examined immunohistochemically by using a monoclonal antibody(clone RAS 10) with respect to the degree of their histological differentiation. To achieve this, the intensity of staining for the protein was compared between undifferentiated and well differentiated carcinomas, i.e. extreme subtypes of common epithelial carcinomas. The former was composed of 8 "solid" carcinomas and the latter, 11 serous, 8 mucinous, 4 endometrioid and 4 clear cell carcinomas. All the cases examined, including both undifferentiated and well-differentiated carcinomas, showed a positive reaction to this antibody. Staining intensity and the number of positive cells somewhat varied among the cases. Additionally, 2 cases of ovarian epithelial tumors of low malignant potential (I,MP) were stained with this antibody. Both the cases were positive, but the number of positive cells seemed to be rather less than that found in the carcinoma groups. Thus, no differences in ras p21 expression were observed between the cases examined in spite of the differences in the degree of differentiation of the epithelial ovarian carcinomas. However, the possibility remained that the number of positive cells could be an indicator of malignant potential, enabling us to distinguish LMPs from carcinomas.

Cloning and gene mapping of the mouse homologue of the CBFA2T1 gene associated with human acute myeloid leukemia

The human CBFA2T1 (also known as MTG8) gene, on chromosome 8, has been identified through its involvement in the t(8;21) chromosomal translocation, frequently found in acute myeloid leukemia. We report here the isolation and characterization of the mouse homologue of the CBFA2T1 gene, Cbfa2t1h. Nucleotide sequence analysis of Cbfa2t1h cDNA clones revealed an open reading frame encoding a protein of 577 amino acids with an extremely high degree of amino acid identity (99.3%) to the human protein. The nucleotide sequence is also highly conserved between mouse and human in the 5'- and 3'-untranslated regions (87.0, 92.0, and 93.7% identities for 5'-untranslated, coding, 3'-untranslated regions, respectively). The 3'-untranslated region of Cbfa2t1h contains a (CA)n dinucleotide repeat, and the polymerase chain reaction amplification of the (CA)n repeat region revealed fragment length polymorphism among mouse strains. Using this polymorphism, we have mapped Cbfa2t1h to mouse chromosome 4 close to the centromere using SMXA recombinant inbred strains and 106 intersubspecific backcross progenies of the (DBA/2 x Mae) x Mae cross. The chromosomal location was also confirmed by fluorescence in situ hybridization.

T lymphomagenesis is determined by a dominant host gene thymic lymphoma susceptible mouse-1 (TLSM-1) in mouse models

Susceptibility to T lymphomas in mice is determined by a number of viral and host genetic factors. We analyzed the types and latent period of lymphomas spontaneously occurring in crosses between AKR/Ms, a T lymphoma-prone mouse strain, and SL/Kh, a pre-B lymphoma-prone strain. The incidence of T lymphomas in the F1 hybrids backcross to SL/Kh as well as F2 generation mice indicated that a dominant host gene thymic lymphoma susceptible mouse-1 (Tlsm-1) of AKR/Ms determined the type of lymphomas to be thymic. Linkage analysis with microsatellite markers assigned Tlsm-1 to the map position 61 cM from centromere of the chromosome 7. Close scrutiny of this region of AKXD recombinant inbred strains for spontaneous T lymphomas revealed the presence of Tlsm-1-like gene most likely between D7MIT71 (map position 62) and D7MIT13 (map position 70). On the other hand, a SL/Kh-derived recessive allele at a major histocompatibility complex (MHC)-linked locus accelerated development of both T and B lymphomas.

Development of pigmented scales on rat skin: relation to age, sex, strain, and hormonal effect

Development of brownish scales on the skin was examined in seven inbred strains of laboratory rats, Rattus norvegicus (F344, WM, WF, LOU, BUF, ACI, and LEJ rats) up to 104 weeks old. Pigmented scales appeared mainly on the dorsum of the body but also on the perineum and the tail. The distribution of the scales changed with age and showed sex and strain differences. In males of all seven strains except F344, the scales on the dorsal region appeared at puberty then gradually developed and spread extensively in a strain-dependent pattern, until the rats were of adult age. The coloring gradually decreased with further aging. However, in F344 rats, the coloring did not spread after puberty, and in adult rats, it was partial and very weak. Among female rats, scales appeared only in LEJ rats when they were of adult and old age. Gonadectomy in WM and WF rats caused fading of the dorsal scales in males but slightly induced coloring in females. Androgen administration to the gonadectomized rats increased the pigmented scales in both sexes of both strains. In F344 rats, however, skin color was hardly changed by gonadectomy and/or the subsequent androgen administration in either sex. In F344 male rats, the testosterone concentration in serum was not significantly lower than that of WM and WF male rats. These results indicate that the development of brownish scales on rat skin is dependent on age, sex, strain, and androgen, and it is suggested that the ability producing the scales is genetically poor in the F344 strain.

Strain difference of susceptibility to 4-nitroquinoline 1-oxide-induced tongue carcinoma in rats

Strain difference of susceptibility to 4-nitroquinoline 1-oxide (4NQO)-induced squamous cell carcinomas of the tongue among Dark-Agouti, Long-Evans, Sprague-Dawley, ACI/Ms, Fischer 344, Donryu and Wistar/Furth rats was surveyed by evaluating the survival times, incidences and sizes of developed tumors as markers of susceptibility. Administration of 4NQO dissolved in drinking water induced squamous cell carcinomas in various sites of the upper digestive tract mucosa of all the experimental male and female rats of the seven strains. Regarding the mean survival times, Wistar/Furth rats survived much longer than any other strain of rats, and Dark-Agouti showed the shortest survival. The incidence of large, mass-type carcinomas of the tongue of Dark-Agouti rats was higher than in any other strain of rats, while that of Wistar/Furth rats was the lowest. Subsequently the mitotic activity and bromodeoxyuridine incorporation in the tongue epithelium of Dark-Agouti and Wistar/Furth rats were estimated after a short-term administration of 4NQO. There was a pronounced difference between the two strains of rats, because the proliferative responses of the tongue epithelium of Dark-Agouti rats to the 4NQO stimulation were much higher than those of Wistar/Furth rats. These results indicated that there are marked differences in the susceptibility to 4NQO-induced tongue carcinoma among the seven strains of rats, and that Dark-Agouti and Wistar/Furth rats could be useful as models of highly and poorly susceptible strains, respectively, for further genetic analysis.

Mapping of the nu gene using congenic nude strains and in situ hybridization

The chromosomal location of the nu gene, which is responsible for hairlessness and athymus, was determined using six DNA markers (interleukin 3 [Il-3], Myhs, Acrb, Evi-2, Mpo, and Hox-2) on mouse chromosome 11. We constructed the high-resolution physical mapping of the six DNA markers on chromosome 11 by in situ hybridization using fluorescence-labeled cosmid probes. The results indicate the order of centromere-(41cM)-Il-3-(3cM)-Myhs- (4cM)-Acrb-(6cM)-Evi-2-(3cM)-Mpo- (5cM)- Hox-2. We have used congenic nude strains and examined which of the six DNA markers were derived from the original nude mouse. We found the Evi-2 locus is linked to the nu gene in all the informative, independent congenic nude strains. From these data, we could estimate the location of the nu gene, not only genetically but also physically within a region that spans approximately 17 megabases (9 cM) between the Acrb and Mpo genes.

Action site of the gene determining susceptibility to propylnitrosourea-induced thymic lymphomas in F344 rats

To clarify whether the determining effect of the thymic lymphoma susceptible-1 (Tls-1) gene is on putative N-propyl-N-nitrosourea (PNU) target cells among T-lineage cells or on other host factors, we investigated the PNU-induced lymphomagenesis in transplantation chimeras between susceptible F344 and resistant LES strain rats. Administration of PNU to lethally irradiated (F344 x LES)F1 rats reconstituted with bone marrow cells from either F344 or LES parental rats invariably led to development of donor-origin thymic lymphomas. On the other hand, thymic lymphomas were induced in thymectomized F1 rats grafted with neonatal LES thymus, of which 4 out of 8 were of the donor origin. These observations indicate that the target cells of thymic lymphomagenesis of F344 and LES rats were equally susceptible to PNU provided they are in susceptible hosts and the LES thymus seems capable of supporting thymic lymphomagenesis, although this capability wanes with aging of the thymus. The effect of the Tls-1 gene, therefore, is neither on PNU susceptibility of the target cells nor on the capability of the thymus to support lymphomagenesis, but on other host factors either in or out of the thymus.

A lung cancer case with numerous calcified metastatic nodules of the brain

A case of pulmonary adenocarcinoma with numerous calcified metastatic nodules of the brain is reported. Autopsy revealed about 400 metastatic nodules in the central nervous system, most of which were calcified.

Molecular and cytogenetic studies on nucleolar cistrons (rDNA) in mouse leukemia cells

The gene dosage change of nucleolar cistrons (rDNA) in tumor cells has not been extensively studied. The present studies showed that increased dosage, as well as abnormal distribution of rDNA, was frequently associated with leukemia cells of SL/Ni and AKR mice. In normal SL cells, 37%, 39%, and 25% of rDNA was located in nucleolar organizer regions (NOR) of chromosomes #12, #18, and #19, respectively. Increase of rDNA/DNA was shown by hybridization on filter membranes in SL1, SL2, SL3, and M1 leukemia cells. Direct measurement of rDNA/DNA in G1 cells revealed an 11% increase in synchronized M1 cells. The increased rDNA dosage was explained by trisomy 12 in SL1 and SL2, the ectopic NOR of #9 in SL3, and the double t(X;19) marker chromosomes in M1. On the other hand, in normal AKR cells, 27%, 29%, and 45% of rDNA was assigned to NORs of chromosomes #15, #16, and #18, respectively. The relative rDNA distribution among NORs estimated by autoradiographic grain counting was suggested to be abnormal in AKR leukemia cells despite their normal karyotype; 36% rDNA was shown to be in chromosomes #15 and #16, respectively, by relative reduction in chromosome #18 in AKR1; the trisomy 15 explained the increased rDNA in AKR2; a relative increase was found in chromosome #15 in AKR3. These results were discussed with reference to the reported NOR involvement in chromosome translocation and amplification in tumor cells.

Accelerating effect of nude gene heterozygosity on spontaneous AKR thymic lymphomagenesis

The effect of nude gene heterozygosity on spontaneous AKR thymic lymphomagenesis was studied by comparing female littermates of AKR/Ms-nu/+ and +/+. As previously reported in nude gene heterozygotes with genetic background other than AKR, AKR/Ms-nu/+ mice had a significantly smaller thymus than the +/+ littermates. Overall incidences of thymic lymphomas were comparable in the two genotypes, but the mean latent period for lymphoma development was significantly shorter in the nu/+ mice (266.3 +/- 11.6 days) than in the +/+ mice (319.3 +/- 7.9 days). Both genotypes of mice expressed a high level of XC+-ecotropic murine leukemia virus. Expression of xenotropic virus was more variable, but there was no consistent difference in onset of virus expression or in virus titer that could explain accelerated lymphomagenesis in the nude gene heterozygotes.

Role of the thymus in propylnitrosourea-induced thymic lymphomagenesis in F344 rats

The role of the thymus in propylnitrosourea (PNU)-induced thymic lymphomagenesis was studied in F344 rats with genetically determined high susceptibility. The thymus was absolutely required for thymic lymphomagenesis, since thymectomy prior to or after PNU treatment abolished lymphomagenesis, whereas grafting of a normal neonatal thymus before PNU treatment restored it. Exposure to PNU for 42 days resulted in the appearance of potentially lymphomatous cells first in the thymus, and overt T-lymphomas subsequently appeared. Such cells seemed to be thymus-dependent, since intrathymic transfer of the thymus cells from 42-day PNU-treated rats induced T-lymphomas much more efficiently than intravenous transfer. Further, grafting of the thymus from 42-day PNU-treated rats into thymectomized rats resulted in T-lymphomas of donor origin without additional PNU treatment. Cells from the spleen or bone marrow from the same donors did not give rise to T-lymphomas irrespective of the route of cell transfer and sublethal irradiation of the recipients. Morphologically atypical cell foci were detected first on the 28th day in the thymus and were most pronounced during the 35th-42nd days. Therefore, the thymus is the essential organ in which the early events of PNU-induced rat T-lymphomagenesis take place.

Genetically determined susceptibility of Fischer 344 rats to propylnitrosourea-induced thymic lymphomas

Administration of propylnitrosourea p.o. by our protocol induced a high incidence of hematolymphatic neoplasms in all six rat strains studied. Remarkable strain differences in susceptibility to thymic lymphomas were observed. The incidence of thymic lymphomas was high in Fischer 344 (98%) and Wistar/Furth (71%) but low in Sprague-Dawley (29%), ACI/Ms (23%), Donryu (24%), and Long-Evans (10%) strains. Segregation of thymic lymphoma incidence among crosses between highly susceptible Fischer and poorly susceptible Long-Evans rats indicated that the increased susceptibility to thymic lymphomas of Fischer rats was determined by a dominant gene TIs-1 (thymic lymphoma susceptible) and that this gene was linked to the coat color loci, p and c, in Linkage Group I in the order of TIs-1 - c - p. The presence of another independently assorting dominant gene, TIs-2, was also suggested to accelerate the thymic lymphoma-genesis. Expression of the group-specific antigen of murine leukemia virus as well as infectious viruses was not detected in nine propylnitrosourea-induced thymic lymphomas of Fischer rats.

Formation of symbiotic complex by microenvironment-dependent mouse leukemias and thymic epithelial reticular cells

Developing thymic leukemias of the mouse have been assumed to form symbiotic complexes with thymic microenvironments. This symbiosis is morphologically based on pseudoemperipolesis (PEMP). The mechanism of the association of microenvironment-dependent leukemia cells with thymic epithelial reticular cells (TER) was analyzed in vitro by scanning electron microscopy, microcinematography, and a quantitative assessment of PEMP. PEMP was a consequence of active locomotion of the leukemia cells, with TER passively accepting the leukemia cells "crawling" under their cytoplasm. The integrity of the cytoskeletal system of both cells was essentially required for PEMP, since cytochalasins and colchicine were highly inhibitory to PEMP. The mechanism of action of these compounds was probably dual: inhibition of the locomotive movements of the leukemia cells. A similar inhibition of PEMP was also observed with the tumor promoter 12-O-tetradecanoylphorbol 13-acetate.

Early changes of dog esophageal mucosa induced by N-ethyl-N'-nitro-N-nitrosoguanidine

Early changes in the esophageal mucosa of dogs induced by N-ethyl-N'-nitro-N-nitrosoguanidine (ENNG) were studied. Seven one-year-old beagle dogs were given a solution of 250 micrograms ENNG/ml to drink ad libitum for 4 months. Three different kinds of lesions (10 erosive carcinomas, 4 slightly elevated microcarcinomas and 19 leukoplakias) were recognized. These three kinds of lesions were not located adjacent to one another, and were surrounded by almost normal stratified squamous epithelium. The foci of the carcinomas revealed an abrupt transition to normal epithelium and were considered to have arisen abruptly from normal esophageal epithelium. The histogenesis of squamous cell carcinomas of the esophagus in dogs may differ from that in man.

Establishment and characterization of a cell line (Br-NHF-1) derived from human mammary carcinoma

A new human cell line, Br-NHF-1, was established from the pleural effusion of a patient with advanced mammary carcinoma. The cells survived 52 subcultivations during more than 33 months. The cells possess epithelial features, showing rosettes, acinar formation and domes in or among the compact colonies. The modal chromosome number is 51 with some marker chromosomes. Xenografted tumors retained a similar histology to the original tumor. No estrogen-binding protein was detectable in the culture, but there was a significant amount of basic fetoprotein. Production of casein in the cells was detected by immuno-fluorescence testing.

Effect of BNU treatment on leukaemogenesis in lethally irradiated AKR mice restored with bone-marrow and spleen cells

The leukaemogenic effect of N-butyl-N-nitrosourea (BNU) was studied in normal and thymectomized AKR mice which were lethally irradiated and restored with either bone-marrow (BM) or spleen cells from (AKR X AKR/T1ALD)F1 donors. In some instances T1ALD thymic cells were added to the restorative inoculum. It was possible to determine the origin of the leukemic cells by the metacentric marker chromosomes of T1ALD. The T- or B-cell characteristics were further ascertained by the cytotoxicity test for theta antigen and the EAC rosette test. All leukaemias whether thymic (TLS) or extra-thymic (ETL), developed from donor bone-marrow or spleen cells and never from the injected thymic cells. In non-thymectomized animals BNU increased the percentage of TLS and shortened their latency. Most of TLS which occurred after BNU treatment of BM-restored mice were theta-negative whereas the majority of TLS which occurred in controls and in spleen-restored animals were theta-positive. This suggests that during their maturation process BM-derived T precursors transit through a theta-negative compartment. This compartment does not reach a similar size during the maturation process of the spleen-derived precursors. Adding thymic cells to the restorative inoculum enhanced leukaemogenesis and suppressed theta-negative TLS in BM-restored mice. Thymectomized mice, restored either by BM or spleen, had a low incidence of ETL which was not significantly increased by BNU treatment except in the case of mice restored with spleen cells. The leukaemic cells of one ETL were theta-positive whereas all the other leukaemias had no detectable T or B marker. The percentage of ETL was higher in thymectomized mice treated with BNU alone than in those previously subjected to irradiation and restoration. These results strongly suggest that a theta-negative T precursor could be involved in extra-thymic leukaemogenesis but the possible involvement of a B precursor cannot be rule out unless experiments are carried out with specific markers of T- and B-cell sub-classes.

Production of thymic cells by mouse spleen and bone marrow

Karyotype difference between the AKR/TIALD strain (T1) that bears 2 metacentric markers, and the AKR strain (no marker) was used to follow the thymic repopulation of lethally irradiated (AKR X T1) F1 hybrids restored by AKR bone marrow (BM) or spleen cells. Eleven days following radiation exposure, 40-50% of the thymic cells were BM-derived in the mice restored with BM cells whereas spleen-derived cells remained below 10% in those restored with spleen cells. The thymic repopulation by spleen-derived elements was enhanced either by injecting a larger munber of spleen cells or by adding thymic cells to the spleen inoculum; however in both cases the appearance of the spleen-derived karyotypes still required a delay of about 11 days. The thymic cells could either recruit thymic precursor cells or trigger their multiplication. On the opposite, it has not been possible to demonstrate a favorable effect of the injected thymic cells on the repopulation of the thymus by BM-derived elements.

Origin of leukemic cells in mouse leukemia induced by N-butylnitrosourea

Administration of N-butylnitrosourea (BNU) induces leukemia in thymectomized C57BL/6J and C3Hf/Bi mice with almost the same high frequency as in non-thymectomized mice. Thymectomized and BNU-treated (C3Hf/Bi times CBA/H-T6T6)F1 mice receiving neonatal thymus tissues from C3Hf donors developed leukemias with or without marked enlargement of the grafts. The origin of leukemic cells was analysed by T6 marker chromosome and thymus allo-antigen theta in this hybrid system. Cells from leukemia with enlarged thymus grafts possessed the sigma-antigen detected by cytotoxicity tests. Cells from leukemia without thymus involvement had no sigma antigen. The leukemic cells arising at the site of thymus grafts were derived from the graft itself (C3Hf) or from the host (C3Hf times CBA/H-T6T6)F1 cells, most probably bone marrow cells which are repopulating into the graft. When the mice were treated with BNU after the lymphoid elements in the grafted thymus had been replaced by host cells, leukemia mainly composed of host-origin cells developed. Leukemia in which neoplastic cells in the thymus grafts were of donor origin and those in other hematopoietic tissues were of host origin was found not infrequently. The present results mean that the target cells in BNU leukemogenesis are distributed within and outside the thymus and that some leukemias are of multifocal tissue origin.