General nitrogen regulation of nitrate assimilation regulatory gene nasR expression in Klebsiella oxytoca M5al

Klebsiella oxytoca can assimilate nitrate and nitrite by using enzymes encoded by the nasFEDCBA operon. Expression of the nasF operon is controlled by general nitrogen regulation (Ntr) via the NtrC transcription activator and by pathway-specific nitrate and nitrite induction via the NasR transcription antiterminator. This paper reports our analysis of nasR gene expression. We constructed strains bearing single-copy Phi(nasR-lacZ) operon fusions within the chromosomal rhaBAD-rhaSR locus. The expression of DeltarhaBS::[Phi(nasR-lacZ)] operon fusions was induced about 10-fold during nitrogen-limited growth. Induction was reduced in both ntrC and rpoN null mutants, indicating that Ntr control of nasR gene expression requires the NtrC and sigma(N) (sigma(54)) proteins. Sequence inspection of the nasR control region reveals an apparent sigma(N)-dependent promoter but no apparent NtrC protein binding sites. Analysis of site-specific mutations coupled with primer extension analysis authenticated the sigma(N)-dependent nasR promoter. Fusion constructs with only about 70 nucleotides (nt) upstream of the transcription initiation site exhibited patterns of beta-galactosidase expression indistinguishable from Phi(nasR-lacZ) constructs with about 470 nt upstream. Expression was independent of the Nac protein, implying that NtrC is a direct activator of nasR transcription. Together, these results indicate that nasR gene expression does not require specific upstream NtrC-binding sequences, as previously noted for argT gene expression in Salmonella typhimurium (G. Schmitz, K. Nikaido, and G. F.-L. Ames, Mol. Gen. Genet. 215:107-117, 1988).

Impaired paracrine effect of endothelin-1 on vascular smooth muscle in streptozotocin-diabetic rats

OBJECTIVE

This study was to examine the effect of streptozotocin-induced diabetes on endothelin-1 and its receptors in the mesenteric artery and in the thoracic aorta.

METHODS

Diabetes was induced in SD rats by streptozotocin. Insulin was given subcutaneously. Endothelin-1 levels in the plasma, thoracic aorta and mesenteric artery were measured using radioimmunoassay. The Bmax and Kd values of endothelin-1 receptors in the mesenteric artery and in the thoracic aorta were analyzed using Scatchard plot analysis. Preproendothelin mRNA levels were examined using RT-PCR.

RESULTS

Endothelin-1 levels in the mesenteric artery (83.6 +/- 6.9 pg/mg protein) and in the thoracic aorta (73.9 +/- 8.2 pg/mg protein) increased in 2 week diabetic rats compared with both control (51.8 +/- 5.3, 46.3 +/- 5.9 pg/mg protein) and insulin treated rats (65.6 +/- 8.1, 48.1 +/- 4.2 pg/mg protein) but not in 4 week diabetic rats. There was no change in plasma endothelin-1 levels in these diabetic rats. The RT-PCR results indicated that preproendothelin mRNA levels in the mesenteric artery (0.38 +/- 0.02 vs 0.52 +/- 0.05 units) and in the thoracic aorta (0.45 +/- 0.06 vs 0.62 +/- 0.03 units) decreased in 4 week diabetic rats but not in 2 week diabetic rats. A significant increase in Kd and Bmax of endothelin receptors in the mesenteric artery and in the thoracic aorta was observed in both 2 week (about 70%) and 4 week (80-85%) diabetic rats. Insulin replacement reversed the effects of diabetes on endothelin-1 peptide contents, preproendothelin mRNA levels and the binding activity in the blood vessels.

CONCLUSION

Increased endothelin peptide content with no change in mRNA or decreased mRNA levels with no change in peptide content together with increased receptor binding sites and affinities might imply a decrease in endothelin release and therefore an impaired paracrine effect of endothelin on vascular smooth muscles in these STZ-diabetic rats.

Streptozotocin-induced diabetes has differential effects on atrial natriuretic peptide synthesis in the rat atrium and ventricle: a study by solution-hybridization-RNase protection assay

In rats with streptozotocin (STZ)-diabetes for 2 or 4 weeks, the atrial natriuretic peptide (ANP) concentrations in the atria decreased whilst that of ANP in the plasma and ventricles increased. ANP concentrations in the hypothalamus and in the brainstem did not change in either 2- or 4-week diabetic rats. Atrial ANP content was partly restored by insulin replacement in 4-week diabetic rats. Plasma ANP concentrations and ventricular ANP contents were reversed to normal by insulin treatment in both 2- and 4-week diabetic rats. Solution-hybridization-RNase protection assay showed a significant increase in the preproANP mRNA expression in the ventricles but not in the atria. These results indicated that the STZ-diabetes increased the synthesis of ANP in the ventricles and consequently its release from the ventricles. The synthesis of ANP in the atria did not change as judged from the preproANP mRNA expression but the release of ANP from the atria might also be increased for ANP content decreased in the atria. The reason for the difference in the response of atrial and ventricular preproANP concentrations to STZ-diabetes is not known.

Karyotypic changes associated with spontaneous acquisition and loss of tumorigenicity in a human transformed bronchial epithelial cell line: evidence for in vivo selection of transformed clones

In this study, we describe the karyotypic changes associated with the spontaneous acquisition of tumorigenicity in an immortalized tumor bronchial cell line. Neoplastic transformation of the NL20 human bronchial epithelial cell line occurred after 3 yr in culture, and was associated with loss of chromosome 18 together with acquisition of multiple copies of 9q21.2-->34. The nontumorigenic NL20 cell line had been established by transfection of human bronchial epithelial cells with the SV40 T antigen, and had retained a relatively stable karyotype after the first 32 passages in vitro. However, when cells from p184 were inoculated into nude mice, a transplantable tumor was obtained that was derived from a minor clone present in this otherwise stable line. Subsequent passaging of the NL20 cells in vitro did not yield further tumors, and the minor clone from which the tumorigenic NL20T cell line derived was no longer evident in NL20 cells by Passage 205. Furthermore, the original tumorigenic NL20T cells lost the neoplastic phenotype after 25 passages in vitro and reverted to the nontumorigenic karyotype observed at p189. In contrast to the loss of the tumorigenic phenotype and karyotype, which occurred with in vitro passaging of the original tumor, when the NL20T cells were passaged in other nude mice, they continued to give rise to tumors with sevenfold amplifications of 9q sequences and loss of chromosome 18, and cells from the secondary tumors (NL20T-A cells) have maintained a stable karyotype and remain tumorigenic even after 64 passages in vitro. A mixture of 10% tumorigenic NL20T-A and 90% nontumorigenic NL20 cells formed tumors in athymic nude mice when cultured in vitro on fibronectin, but not on plastic; cytogenetic analysis demonstrated that the tumors and cell cultures were composed of tumorigenic NL20T-A cells, whereas cytogenetic analysis of cells cultured on plastic were identical to the nontumorigenic NL20 cells. These data support the hypothesis that neoplastic transformation in our original cell line arose from in vivo selection of a small mutant clone, which had arisen in culture and was subsequently selected in vivo but was lost with in vitro culture.

The genomic structure and chromosomal location of the human TR2 orphan receptor, a member of the steroid receptor superfamily

Human TR2 orphan receptor, isolated from the testis and prostate, is a member of the steroid/thyroid hormone receptor superfamily. With the screening of a human genomic library and the combination of primer walking and PCR sequencing, we found that the entire TR2 orphan receptor gene coding region and 5'-untranslated region feature 13 introns and 14 exons, and that the consensus splice sequences (GT-AG) are present in all intron-exon boundaries. Within the region that codes for the DNA binding domain, TR2 orphan receptor gene has a distinct intron-exon junction. Whereas all other known steroid receptors have one splice site that separates their first and second zinc fingers in the DNA binding domain, TR2 orphan receptor has a rare splice site located in the middle of its first zinc finger. The identification of specific junction sequences for potential alternative splicing sites helps to explain the existence of multiple forms of TR2 orphan receptor cDNA (TR2-5, 7, 9, 11). The S1 nuclease protection assay for TR2 message revealed that there are multiple transcription initiations, and that the major cap site surrounded by an initiator-like sequence is located at the 104th nucleotide upstream from the translation start codon. Sequence analysis of a 2.7-kb DNA fragment upstream of the TR2 orphan receptor translation start codon unveiled several potential cis-acting elements, such as AP-1, HNF-5, GATA1 binding sites, and GC boxes. Using fluorescence in situ hybridization combined with a high-resolution G-banding technique, we found that the TR2 orphan receptor gene was mapped to human chromosome 12 at band q22, whereas the structurally closely related TR4 orphan receptor gene was mapped to human chromosome 3 at band q24.3.

The effect of aging on ANP levels in the plasma, heart, and brain of rats

Atrial natriuretic peptide (ANP) is a hormone important in the cardiovascular system via its regulatory roles in sodium and water excretion, and in vasodilatation. Aging represents a major risk factor in the development of hypertension, a perturbation which may activate compensatory mechanisms. The influence of aging on the ANP levels in plasma, atria, ventricles, hypothalamus, and brainstem was evaluated by comparing young (3 mo), middle-aged (12 mo), and old (24 mo) rats. Plasma and ventricular ANP levels increased with age, while ANP content in the atria as well as hypothalamus decreased significantly. PreproANP mRNA contents increased with age in the ventricle but not in the atrium. It is suggested that the increase in plasma ANP levels in old rats is due to the increase in ANP secretion from the atrium and the ventricle, partly as a result of an increase of release of ANP from hypothalamus.

Detection of ebaf, a novel human gene of the transforming growth factor beta superfamily association of gene expression with endometrial bleeding

Human endometrium is unique since it is the only tissue in the body that bleeds at regular intervals. In addition, abnormal endometrial bleeding is one of the most common manifestations of gynecological diseases, and is a prime indication for hysterectomy. Here, we report on a novel human gene, endometrial bleeding associated factor (ebaf), whose strong expression in endometrium was associated with abnormal endometrial bleeding. In normal human endometrium, this gene was transiently expressed before and during menstrual bleeding. In situ hybridization showed that the mRNA of ebaf was expressed in the stroma without any significant mRNA expression in the endometrial glands or endothelial cells. The predicted protein sequence of ebaf showed homology with and structural features of the members of TGF-beta superfamily. Fluorescence in situ hybridization showed that the ebaf gene is located on human chromosome 1 at band q42.1. Thus, ebaf is a novel member of the TGF-beta superfamily and an endometrial tissue factor whose expression is associated with normal menstrual and abnormal endometrial bleeding.

The correlation between the loss of chromosome 14q with histologic tumor grade, pathologic stage, and outcome of patients with nonpapillary renal cell carcinoma

BACKGROUND

Conventional pathologic classifications of human renal cell carcinoma (RCC) give little insight into oncogenesis and little assistance in predicting the clinical behavior of this disease. Identification of specific genetic alterations involved in the development of RCC using fluorescence in situ hybridization (FISH) however, may help provide foundations for classification, prognosis, and clinical management of the patients.

METHODS

Archival, paraffin embedded tissue sections from 30 human non-papillary RCCs were examined with a dual color FISH technique for loss of chromosomes 3p and 14q. Telomeric DNA probes from 3p or 14q and an internal ploidy control probe, centromeric probe of chromosome 2, were applied directly to the tumor sections. The correlations between loss of 3p or 14q, and tumor ploidy, with tumor grade, pathologic stage, and patient outcome were assessed.

RESULTS

Ninety percent of the patients (27) lost chromosome 3p, and 36.7% of the patients (11) had chromosome 14q deletions. The loss of 3p in the samples tested was unrelated to patient age, gender, outcome, tumor stage, or histologic grade. However, the deletion of 14q was significantly correlated with higher stage (P = 0.01), histologic grade (P = 0.01), and patient outcome (P < 10(-4)).

CONCLUSION

The close correlation of 14q loss with higher stage, higher histologic grade, and poorer outcome for patients with nonpapillary RCC indicates that it may be a promising prognostic marker.

A novel 80 kDa human estrogen receptor containing a duplication of exons 6 and 7

Alterations in the amino acid sequence of the estrogen receptor (ER) have been shown to have dramatic effects on its function. Recently, mutant ERs have been isolated from both clinical samples and established breast cancer cell lines, primarily through the use of the polymerase chain reaction (PCR). All previously reported mutations have given rise to either alterations or truncations of the ER protein. We determined the structure of a novel 80 kDa ER which is expressed in an estrogen independent subclone of the MCF-7 human breast cancer cell line (MCF-7:2A). This 80 kDa ER was initially detected by Western blot analysis using a variety of ER specific antibodies. PCR mapping and partial PCR mediated subcloning of the ER cDNA were used to demonstrate that this protein was an ER containing an in-frame duplication of exons 6 and 7. This type of duplication has not been previously described for any members of the steroid receptor superfamily. Karyotype analysis coupled with fluorescence in situ hybridization (FISH) demonstrated that MCF-7:2A cells contained 4-5 copies of the ER gene in contrast to 2 copies in MCF-7:WS8 cells. The ER gene was localized by FISH analyses in both the MCF-7:WS8 and MCF-7:2A cells on chromosome 6, which is the source of the ER in normal human cells. The relative expression level of 2:1 is consistent with DNA gene dosage analysis. Genomic PCR was then used to demonstrate that the 80 kDa ER mRNA was not derived from the trans-splicing of two ER mRNAs but was the result of a genomic rearrangement in which exons 6 and 7 were duplicated in an in-frame fashion. This variant ER may prove to be useful in elucidating the mechanism of estrogen action in breast cancer cells.

Extensive amplification of bcr/abl fusion genes clustered on three marker chromosomes in human leukemic cell line K-562

Using fluorescence in situ hybridization (FISH), we were able to demonstrate 22-24-fold amplification of the bcr/abl fusion gene in the human leukemic cell line K-562. About 60% of the amplified sequences are localized to a large acrocentric marker chromosome, with another 30% clustered on a small acrocentric chromosome. In addition to these two masked Ph chromosomes, the remaining bcr/abl fusion genes are located on a der(2) distal to band q33. G- and C-banding analysis revealed similar unique banding patterns in both masked Ph chromosomes and suggests that amplification occurred by tandem duplication of the bcr/abl fusion site. Because the number of bcr/abl fusion genes may be increasing over time, it is critical that researchers using K-562 cells should be aware of this extensive amplification.

Nonrandom cytogenetic changes accompany malignant progression in clonal lines abelson virus-infected lymphocytes

Initially, lymphoid cells transformed by v-abl or BCR/ABL oncogenes are poorly oncogenic but progress to full transformation over time. Although expression of the oncogene is necessary to initiate and maintain transformation, other molecular mechanisms are thought to be required for full transformation. To determine whether tumor progression in ABL oncogene-transformed lymphoid cells has a genetic basis, we examined whether progression of the malignant phenotype of transformed clones correlates with particular cytogenetic abnormalities. A modified in vitro bone marrow transformation model was used to obtain clonal Abelson murine leukemia virus-transformed B lymphoid cells that were poorly oncogenic. Multiple subclones were then derived from each clone and maintained over a marrow-derived stromal cell line for several weeks. Over time, clonally related Abelson murine leukemia virus-transformed subclones progressed asynchronously to full transformation. The data show that tumor progression can occur in the absence of detectable cytogenetic changes but, more importantly, that certain cytogenetic abnormalities appear reproducibly in highly malignant subclones. Therefore, three independent subclones showed deletion in a common region of chromosome 13. Other highly malignant cells carried a common breakpoint in the X chromosome, and, finally, two subclones carried an additional chromosome 5. These results are consistent with the hypothesis that ABL oncogenes are sufficient for the initial transformation of cells but that additional genetic events can drive oncogenic progression. These observations further suggest that diverse genetic mechanisms may be able to drive tumor progression in cells transformed with ABL oncogenes.

Allogeneic T-cell clones able to selectively destroy Philadelphia chromosome-bearing (Ph1+) human leukemia lines can also recognize Ph1- cells from the same patient

Immunocompetent cells in bone marrow allografts have been associated with a graft-versus-leukemia (GVL) effect. To further characterize effector mechanisms that may be involved in this GVL phenomenon, we have previously established an in vitro model to identify allogeneic T-cell clones that selectively mediate cytotoxicity against a patient's leukemic cells, but not against nonleukemic lymphocytes from the same patient. We have modified this in vitro model to test whether the Ph1 chromosome and the P210 fusion protein it controls have a detectable role in leukemia-specific recognition by allogeneic T-cell clones. In this report, T-cell lines reactive with allogeneic Ph1 chromosome-bearing (Ph1+) chronic myeloid leukemia (CML) cell lines were derived and selected to be minimally reactive with Ph1 negative (Ph1-) lymphoid lines from the same patient. However, after prolonged culture, these same T-cell lines also mediated significant destruction of the Ph1- target cells from the same patients. These T-cell lines specifically recognized cells from the allogeneic CML patient to which they were sensitized, and were not contaminated by an outgrowth of natural killer cells. Furthermore, subclones could be derived from these T-cell lines, and some of these subclones again showed selective killing of the allogeneic Ph1+ leukemia cell lines, and not of the Ph1- cell line from the same patient. Analyses of T-cell receptor (TCR) genes showed the alloreactive T-cell lines and the Ph1+ selective subclones derived from them to be of the same clonal origin. This suggests that the same T cells reacting with antigens expressed on the nonleukemic Ph1- targets can at times selectively and preferentially kill the allogeneic Ph1+ cells. As the same TCR that recognizes Ph1+ cells also can recognize the Ph1- targets, it appears that the Ph1+ chromosome does not play a detectable role in recognition by these allogeneic T-cell clones. This in vitro observation may provide a model for evaluating the relationship between GVL and graft-versus-host disease effects.

Assessing the significance of chromosome-loss data: where are suppressor genes for bladder cancer?

Cytogenetic analysis reveals alterations of chromosome structure (losses, gains, and rearrangements of genetic material) in bladder cancer cells generated using an in vitro/in vivo transformation system. To predict possible locations of bladder cancer suppressor genes, we performed a robust Bayesian analysis of the chromosome-loss data. We postulated a simple stochastic model to describe chromosome loss during tumour progression. Posterior computations are enabled by a dynamic simulation algorithm. Ordered by decreasing posterior probability of putatively harbouring a suppressor gene, we observe significant losses on chromosomes 3, 18, 13, 10, 11, and y.

In vitro radiation-induced neoplastic progression of low-grade uroepithelial tumors

Recent interest has focused on the identification of molecular genetic mechanisms in multistep neoplastic transformation. In vitro exposure of simian virus 40 (SV40)-immortalized human uroepithelial cells (SV-HUC) that are environmentally relevant to bladder carcinogens has been shown to produce tumorigenic transformation, as assessed by the ability of cells exposed to a carcinogen to form xenograph tumors with heterogeneous cancer phenotypes ranging from very aggressive, invasive high-grade carcinomas to superficial low-grade indolent tumors. In addition, exposure of a low-grade indolent tumor generated in the SV-HUC system, MC-T11, to the same carcinogens results in neoplastic progression as assessed by the production of high-grade aggressive cancers. In the present study, we show neoplastic progression of MC-T11 after in vitro exposure to a single dose of 6 Gy X rays. In addition, we show that the chromosome deletions, including losses of 4q, 11p, 13q and 18, observed in these radiation-induced tumors are similar to those observed in carcinogen-induced tumors, thus supporting the hypothesis that the experimental cell system, not the transforming agent, dictates the genetic losses required for tumorigenic transformation and progression.

[Submaxillary gland epidermal growth factor accelerated healing of chronic gastric mucosal lesions in rats]

Large amount of EGF-like immunoreactivity was observed in the submandibular gland of rats with immunohistochemical method. The staining is mainly localized in the ductal cells. The level of EGF in gastric juice and serum was measured with a specific and sensitive RIA method. It was observed that EGF level was decreased both in gastric juice and in serum after sialoadenectomy and subsequent healing of chronic gastric ulcer induced by serosal acetic acid was delayed. Oral administration of EGF to sialoadenectomized rats could reverse the lowered rate of ulcer healing to almost normal level. The above results suggested that secretion of EGF may have an important effect on the healing of chronic gastric lesions in rats.

Carcinogen-induced amplification of SV40 DNA inserted at 9q12-21.1 associated with chromosome breakage, deletions, and translocations in human uroepithelial cell transformation in vitro

The fate of integrated SV40 viral genome in SV40-immortalized human uroepithelial cells (SV-HUC) during multistep chemical transformation in vitro was studied. We previously reported that exposure of SV-HUC at passage (P) 15 to the chemical carcinogens 3-methylcholanthrene (MCA), 4-aminobiphenyl (ABP), or the N-hydroxy metabolites of ABP causes tumorigenic transformation and/or neoplastic progression. We report now that these same chemical carcinogens induce amplification of SV40 DNA in SV-HUC. We used fluorescence in situ hybridization (FISH) to show that this amplification occurs at the SV40 integration site, which was mapped near a common fragile site at 9q12-21.1 on the der(9)t(8;9) chromosome that is present in all SV-HUC at the earliest passage studied. Karyotypic analysis, along with FISH, also revealed that all carcinogen-induced tumors (T-SV-HUCs) had breaks at 9q12-21.1, deletions of 9q12-21.1-->pter, and new derivative chromosomes containing SV40 in the segment 9q12-21.1-->9q34::8q22-->8qter. Southern blot analysis, along with FISH, confirmed SV40 genome rearrangements in T-SV-HUCs. In contrast, no 9q12-21.1 breaks were observed in control SV-HUC. Thus, these results associate 9q12-21.1-->pter alterations with HUC tumorigenic transformation. In addition, these results indicate for the first time that (carcinogen-induced) amplification of chromosome-integrated viral genes may create sites that are prone to breakage, deletions, and translocations. These results suggest a new mechanism by which chemical carcinogens in synergy with a DNA tumor virus could initiate a cascade of events that contribute to the genomic instability associated with tumorigenesis.

Role of SV40 T antigen binding to pRB and p53 in multistep transformation in vitro of human uroepithelial cells

In the present study, we examined the sufficiency of SV40 T antigen (Tag) binding to pRB and p53 to substitute for alterations in RB and TP53 at all stages of human uroepithelial cell (HUC) transformation in vitro. Two independent SV40 immortalized HUCs (SV-HUC and SV-HUC/CK2) and 17 independent derivative carcinogen-induced or spontaneous tumors (T-SV-HUCs and T-SV-HUC/CK2) representing different stages of urothelial tumorigenesis were examined. Although five of 17 T-SV-HUCs and SV-HUC/CK2 and its derivative tumor showed 13q chromosome deletion and loss of heterozygosity (LOH), this did not reflect functional loss of pRB because Tag/pRB binding was unaltered and sequencing showed a normal RB gene in all these tumors. No genetic alterations involving 17p or TP53 were detected in any tumors in this study using the same techniques. These results indicate that Tag/pRB and Tag/p53 binding apparently abrogate requirements for/or a selective advantage of RB and TP53 mutations in HUC tumorigenic transformation and progression, as well as in HUC immortalization. These data also provide new evidence that more than one suppressor gene may be located on chromosome 13q.

[Analysis of 930 cases of low birth weight newborns]

The birth weight of 13,048 newborns were analyzed. The results showed: (1) The incidences of low birth weight (LBW) and very low birth weight (VLBW) were 60.10% and 11.19% respectively. (2) The perinatal mortality rates (PMR) for birth weight of < 1,500 g, 1,500-2,499 g and > or = 2,500 g were 465.8%, 127.60% and 5.30% respectively, (3) The causes of perinatal death included hypoxia, deformities, neonatal diseases and therapeutic induction of labour (38.80%, 25.86%, 22.84% and 12.50% respectively). The incidence of malformation in < 2,500 g group was 36 times of that in > or = 2,500 g group. (4) The incidence of LBW was significantly related to gestational age (P < 0.01). (5) The incidences of LBW among groups of various maternal age were significantly different, and the best age for childbirth was 25-29. (6) LBW was associated with mother's occupation, and LBW newborns from woman farmers were 5.8 times of those from intellectuals. (7) The PMRs differed significantly among groups of different maternal cultural background (P < 0.01).

Losses of 3p, 11p, and 13q in EJ/ras-transformable simian virus 40-immortalized human uroepithelial cells

Five independent clones of Simian virus 40 (SV40)-immortalized human uroepithelial cells (CK/SV-HUC) were established after transfection of HUC cultures from the same tissue donor with plasmids encoding SV40 large T and small t antigen genes. Each CK/SV-HUC clone contained a unique SV40 integration site, and all expressed similar levels of SV40 mRNA. All five clones were nontumorigenic, but clones 2, 4, and 5 tumorigenically transformed after transfection at P19 with mutant EJ/ras and also spontaneously after 40 serial passages in vitro. In contrast, CK/SV-HUC clones 1 and 3 did not transform when either approach was used. These differences in transformability among CK/SV-HUC clones could not be predicted based on differences in SV40 gene expression nor on any in vitro growth property tested. In cytogenetic analyses, a transformable clone showed losses of three chromosome arms containing putative cancer suppressor gene regions, including 3p14----pter, 13q, and 11p, whereas the nontransformable clones showed none of these losses. Thus these data indicate that genetic losses on 3p, 11p, and 13q may contribute to tumorigenic transformation of SV40-immortalized human uroepithelial cells.

Chromosome losses in tumorigenic revertants of EJ/ras-expressing somatic cell hybrids

Tumorigenic transformation of SV40-immortalized human uroepithelial cells (SV-HUC) after transfection with EJ/ras was previously reported to be a rare event. To test the hypothesis that ras transformation requires loss of suppressor genes, somatic cell hybrids were generated between a rare tumorigenic transformant and an isogeneic nontumorigenic EJ/ras transfectant obtained in the same experiment. Both parental cell lines, as well as all hybrid progeny, expressed mutant p21 ras protein, but injections of three such independent hybrids into athymic nude mice at passage (P) 4 demonstrated that tumorigenicity was suppressed at 20 of 22 sites. Two tumors developed, after a relatively long 17-week latent period, as compared with a 4-week latent period for the tumorigenic parent. All three hybrids produced tumors at P8, but these showed different latent periods (3-14 weeks). Revertant hybrid tumors were high-grade carcinomas. Cell lines derived from these tumors expressed mutant p21 ras and retained at least 1 EJ/ras integration site. Karyotypic analysis of six independent hybrid tumor revertants showed that each had a unique clonal karyotype. Losses of two or more homologues of 1p, 3p, 4, 8, 10p, 11p, 13q, and 18 were identified in one or more tumorigenic revertants. Losses of all these chromosomes were previously associated with transformation of SV-HUC by EJ/ras, but were also associated with chemical transformation of SV-HUC in tumors that did not express mutant ras. Genetic losses involving most of these chromosomes have also been identified in clinical bladder cancers (i.e., 1p, 3p, 8, 11p, 13 and 18q). These data show that expression of EJ/ras does not negate or significantly alter requirements for multiple genetic losses in HUC tumorigenesis.

Loss of 3p13----p21.2 in tumorigenic reversion of a hybrid between isogeneic nontumorigenic and tumorigenic human uroepithelial cells

Previous studies in our laboratory showed nonrandom losses of chromosome 3p in association with tumorigenic transformation of SV40-immortalized human uroepithelial cells (HUC) to high grade cancers. To test the hypothesis that genes on 3p suppress HUC tumorigenesis, somatic cell hybrids were formed between nontumorigenic SV40-immortalized HUC and an isogeneic derivative transitional cell carcinoma line, MC-T16, that lost 3p on initial transformation. All hybrids were initially tumorigenically suppressed and reversion was always associated with genetic losses, including losses of 3p (Klingelhutz et al., Somatic Cell Mol. Genet., 17: 551-565, 1991). In this paper, we report that the smallest 3p region lost in a tumorigenic hybrid revertant (THR-X) in this system was an unusual interstitial deletion of 3p13----p21.2. Restriction fragment length polymorphism analysis confirmed this loss by showing that THR-X was reduced to homozygosity for D3S30, a 3p13 probe, but remained heterozygous for the distal 3p21.3 probe, D3F15S2. These data, along with our previous report identifying loss of 3p13----p14.2 as the smallest 3p region deleted in association with SV40-immortalized HUC tumorigenic transformation (Klingelhutz et al., Genes Chromosomes Cancer, 3: 346-357, 1991), provide compelling new evidence for a bladder cancer suppressor gene in the 3p13----p21.2 region.

Neoplastic progression by EJ/ras at different steps of transformation in vitro of human uroepithelial cells

The biological effects of expression of mutant ras at different stages of human uroepithelial cell (HUC) tumorigenesis were tested after transfection of EJ/ras into nonestablished HUC and three isogeneic cell lines representing different steps in HUC transformation in vitro. Transfection with EJ/ras failed to immortalize diploid HUC and also failed to cause tumorigenic conversion of a near-diploid SV40-immortalized HUC line (SV-HUC) except at one of six nude mouse inoculation sites. In contrast, EJ/ras-transfected aneuploid low-grade squamous cell carcinoma cells formed undifferentiated, invasive carcinomas at four of six inoculation sites. Furthermore, EJ/ras accelerated tumor growth in MC-ppT11-HA2, an aneuploid high-grade transitional cell carcinoma line, as determined by decreased tumor latent periods and doubling times. These results suggest that EJ/ras contributes to progression, possibly by accelerating tumor growth, but does not in itself cause tumorigenic transformation of uroepithelial cells. To test whether chromosome losses accompanied EJ/ras transformation of SV-HUC, the karyotype of the one SV-HUC tumorigenic transformant obtained (above) was examined. This tumor cell line showed losses of chromosome arms 3p, 10p, 11p, and 18, all of which have been hypothesized to contain genes that suppress cancer development. Therefore, these results also provide new evidence suggesting that genetic losses may be required for mutant ras to contribute to HUC tumorigenic progression.

Nonrandom chromosome losses in tumorigenic revertants of hybrids between isogeneic immortal and neoplastic human uroepithelial cells

Somatic cell hybrid analysis was used to examine the role of recessive cancer genes in tumorigenic transformation in vitro of human uroepithelial cells (HUC). Hybrids between nontumorigenic pseudodiploid SV40-immortalized HUC (SV-HUC) and two aggressive grade III transitional cell carcinomas (TCC) produced in nude mice after in vitro exposure of SV-HUC to 3-methylcholanthrene (MC) were completely suppressed for tumorigenicity at early passage. Tumorigenic reversion occurred after five or more passages in culture and was always accompanied by chromosome losses. Overall, the tumorigenic revertants showed statistically significant losses of chromosomes 1, 4, 5, 9q, 12, 14q, and 17 (all P less than or equal to 0.05) as compared to losses in suppressed hybrids. In addition, hybrid reversion was accompanied by losses that left specific tumors with a single remaining homolog of certain chromosomes (i.e., 3, 5q, 11p, 17p, and 18q). These losses were also considered significant because of the likelihood that genes on these chromosomes were reduced to homozygosity. Many of the significant losses (i.e., 5q, 9q, 11p, and 17p) were of chromosomes that are frequently lost in clinical TCC. Thus, these results support the hypothesis that these chromosomes contain genes whose loss leads to HUC tumorigenesis.

Allelic 3p deletions in high-grade carcinomas after transformation in vitro of human uroepithelial cells

Restriction fragment length polymorphism (RFLP) analysis for allelic losses on the chromosome arm 3p were performed on independent carcinomas produced in athymic nude mice after transformation in vitro of a pseudodiploid clonal SV40-immortalized human uroepithelial cell line (SV-HUC). We analyzed ten primary carcinomas with heterogeneous phenotypes for deletions on 3p by using three informative probes, D3S30, D3S2, and D3F15S2, which map to the 3p11-p14, 3p21.1, and 3p21 regions, respectively. Five of the ten primary cancers showed reduction to homozygosity with at least one of the probes, and all five cancers were high-grade and poorly differentiated. We also analyzed six carcinomas that arose after progression of low-grade cancers, either spontaneously or after exposure to a human bladder carcinogen, to higher grades (progressed carcinomas). Four of the six exhibited 3p allelic loss. No preferential loss of a specific 3p allele was observed in any of the carcinomas. In addition, whereas most of the carcinomas showed allelic loss for all three of the probes, indicating a large-scale deletion, several of the carcinomas exhibited losses for only one or two of the probes, thus making it possible, along with the cytogenetic data, to define the least common region of deletion to 3p13----p14.2. These results support the hypothesis that nonrandom loss of a gene or genes on 3p leads to the development of cancer. Furthermore, these findings associate deletion of a putative 3p13----p14.2 tumor suppressor gene region with the development of high-grade uroepithelial carcinomas.