The extent of proliferative and apoptotic activity in intraductal and invasive ductal breast carcinomas detected by Ki-67 labeling and terminal deoxynucleotidyl transferase-mediated digoxigenin-11-dUTP nick end labeling

BACKGROUND

The balance among cell proliferation, cell differentiation, and cell death determines the cell number in a population as well as the size or even the stage of a tumor. Thus, to improve our understanding of the pathogenesis of neoplasms, it is important to investigate the regulation of both cell proliferation and cell death.

METHODS

This study examined the occurrence of apoptosis and proliferative capacity in 46 breast carcinomas: 20 intraductal carcinomas (ductal carcinomas in situ [DCIS]) and 26 infiltrative ductal carcinomas (IDC). Terminal deoxynucleotidyl transferase-mediated digoxigenin-11-dUTP nick end labeling (TUNEL) and immunostaining with the Ki-67 antibody were used in the examination. A ladder of DNA fragments induced by apoptosis was demonstrated by means of DNA agarose gel electrophoresis in 10 of the available TUNEL positive and negative samples.

RESULTS

The results were correlated with p53, bcl-2, estrogen receptor (ER), and progesterone receptor (PR) protein expression, which would suggest association with apoptosis by immunohistochemistry. The apoptosis and proliferation of each cancer were expressed as the number of tumor cells undergoing apoptosis and proliferation per 1000 tumor cells. The extent of apoptosis was more frequently observed in DCIS than in IDC (21.9+/-6.8 vs. 4.0+/-0.9, P < 0.001), and the proliferation activity was significantly higher in IDC than in DCIS (16.8+/-6.5 vs. 3.5+/-0.8, P < 0.006). Apoptosis associated with MIB-1 positive cells and TUNEL labeling was significantly higher in IDC than in DCIS (3.26 vs. 0.42, P=0.001). In DCIS, apoptosis was correlated with p53 (r=0.663, P=0.005), and p53 had a reverse correlation with bcl-2 (r=0.620, P= 0.018). Moreover, bcl-2 expression was associated with ER (P=0.028) and PR (P= 0.005) expression in both DCIS and IDC.

CONCLUSIONS

The results of this study show that a higher degree of apoptosis and lower proliferation activity in intraductal carcinoma result in a steady-state, self-renewing condition in which net growth of the tumor is rare. The results also indicate that apoptosis was altered by the expression of p53, bcl-2, ER, and PR.

Alterations in GLUT1 and GLUT3 glucose transporter gene expression following unilateral hypoxia-ischemia in the immature rat brain

The brain damage produced by unilateral cerebral hypoxia-ischemia in the immature rat results from major alterations in cerebral energy metabolism and glucose utilization which begin during the course of the insult and proceed into the recovery period. Consistent with a lack of pathology, the alterations in the hemisphere contralateral to the carotid artery ligation are transient and return to normal within 24 h of recovery, whereas the hemisphere ipsilateral to the ligation exhibits both early and late responses, and infarction. The facilitative glucose transporter proteins mediate glucose transport across the blood-brain barrier (55 kDa GLUT1), and into neurons and glia (GLUT3 and 45 kDa GLUT1), and demonstrate both early and late responses to perinatal hypoxia-ischemia. This study employed in situ hybridization histochemistry to investigate the temporal and regional patterns of GLUT1 and GLUT3 gene expression following a severe (2.5 h) hypoxic-ischemic insult in the 7-day old rat brain. Enhanced GLUT1 mRNA expression was apparent in cerebral microvessels of both hemispheres and remained elevated in the ipsilateral hemisphere through 24 h of recovery, consistent with our previous observation of increased microvascular 55 kDa GLUT1 protein. The expression of the neuronal isoform, GLUT3, was enhanced in penumbral regions, such as piriform cortex and amygdala, but was rapidly reduced in the affected areas of cortex, hippocampus and thalamus, reflecting necrosis. The late response, observed at 72 h of recovery, was characterized by extensive necrosis in the ipsilateral hemisphere, loss of GLUT3 expression, and a gliotic reaction including increased GLUT1 in GFAP-positive astrocytes. This study demonstrates that cerebral hypoxia-ischemia in the immature rat produces both immediate-early and long-term effects on the glucose transporter proteins at the level of gene expression.

The BRC repeats in BRCA2 are critical for RAD51 binding and resistance to methyl methanesulfonate treatment

The BRCA2 gene was identified based on its involvement in familial breast cancer. The analysis of its sequence predicts that the gene encodes a protein with 3,418 amino acids but provides very few clues pointing to its biological function. In an attempt to address this question, specific antibodies were prepared that identified the gene product of BRCA2 as a 390-kDa nuclear protein. Furthermore, direct binding of human RAD51 to each of the four single 30-amino acid BRC repeats located at the 5' portion of exon 11 of BRCA2 was demonstrated. Such an interaction is significant, as BRCA2 and RAD51 can be reciprocally coimmunoprecipitated by each of the individual, specific antibodies and form complexes in vivo. Inferring from the function of RAD51 in DNA repair, human pancreatic cancer cells, Capan-1, expressing truncated BRCA2 were shown to be hypersensitive to methyl methanesulfonate (MMS) treatment. Exogenous expression of wild-type BRCA2, but not BRC-deleted mutants, in Capan-1 cells confers resistance to MMS treatment. These results suggest that the interaction between the BRC repeats of BRCA2 and RAD51 is critical for cellular response to DNA damage caused by MMS.

Identification of a novel cytoplasmic protein that specifically binds to nuclear localization signal motifs

Active transport of proteins into the nucleus is mediated by interaction between the classical nuclear localization signals (NLSs) of the targeted proteins and the NLS receptor (importin) complex. This nuclear transport system is highly regulated and conserved in eukaryotes and is essential for cell survival. Using a fragment of BRCA1 containing the two NLS motifs as a bait for yeast two-hybrid screening, we have isolated four clones, one of which is importin alpha. Here we characterize one of the other clones identified, BRAP2, which is a novel gene and expressed as a 2-kilobase mRNA in human mammary epithelial cells and some but not all tissues of mice. The isolated full-length cDNA encodes a novel protein containing 600 amino acid residues with pI 6.04. Characteristic motifs of C2H2 zinc fingers and leucine heptad repeats are present in the middle and C-terminal regions of the protein, respectively. BRAP2 also shares significant homology with a hypothetical protein from yeast Saccharomyces cerevisiae, especially in the zinc finger region. Antibodies prepared against the C-terminal region of BRAP2 fused to glutathione S-transferase specifically recognize a cellular protein with a molecular size of 68 kDa, consistent with the size of the in vitro translated protein. Cellular BRAP2 is mainly cytoplasmic and binds to the NLS motifs of BRCA1 with similar specificity to that of importin alpha in both two-hybrid assays in yeast and glutathione S-transferase pull-down assays in vitro. Other motifs such as the SV40 large T antigen NLS motif and the bipartite NLS motif found in mitosin are also recognized by BRAP2. Similarly, the yeast homolog of BRAP2 also binds to these NLS motifs in vitro. These results imply that BRAP2 may function as a cytoplasmic retention protein and play a role in regulating transport of nuclear proteins.

Administration of dexamethasone induces proteinuria of glomerular origin in mice

The administration of glucocorticoids has been reported to exacerbate proteinuria in a few patients with glomerulonephritis. This effect has not been well recognized, and the pathogenetic mechanism responsible for this phenomenon remains to be clarified. In this study, we observed that a high daily oral dose (0.5 mg/kg body weight) of dexamethasone was capable of inducing overt proteinuria in mice, beginning on day 5 and persisting for a 19-day duration. One fourth of mice also intermittently presented with slight hematuria beginning on day 12. Renal lesions in the dexamethasone-treated mice, which were killed on day 23, were characterized by mild mesangial expansion, segmental or global hyalinosis/sclerosis in deep cortical glomeruli, and focal tubular changes. No glomerular inflammatory cell infiltration or proliferative lesion was noted in any of the mice. Ultrastructural features of glomeruli included mesangial widening characterized by either an increase of mesangial matrix, dilated mesangial channels filled with slightly electron-dense material or mesangial lysis-like appearance showing intracytoplasmic microcysts filled with electron-lucent material, and evidence to support injury of endothelial cells, erythrocytes, and podocytes. An immunofluorescence study revealed enhanced glomerular deposition of IgG, IgA, IgM, and fibrinogen (P < 0.001, compared with normal control mice), but no glomerular C3 deposition was identified in any of the dexamethasone-treated mice. Charge analysis showed no impairment in anionic property of glomerular tufts in the dexamethasone-treated mice. In addition, the dexamethasone-induced proteinuria was greatly attenuated by treatment with a low molecular weight heparin, although it was not reduced by an angiotensin-converting enzyme inhibitor. Data from these experiments suggest that a large dose of glucocorticoids is potentially nephrotoxic. Alteration of a size-dependent permeability may predominantly contribute to the dexamethasone-induced proteinuria. However, the effect of glomerular hyperfiltration may be only partially involved in the pathogenesis of this dexamethasone-induced glomerulopathy in mice.

Characterization of three fibrinogenolytic enzymes from Chinese green tree viper (Trimeresurus stejnegeri) venom

From the venom of Chinese green tree viper (Trimeresurus stejnegeri), three distinct fibrinogenolytic enzymes: stejnefibrase-1, stejnefibrase-2 and stejnefibrase-3, were purified by gel filtration, ion-exchange chromatography and reverse-phase high-performance chromatography (HPLC). SDS-PAGE analysis of those three enzymes showed that they consisted of a single polypeptide chain with mol. wt of 50000, 31000 and 32000, respectively. Like TSV-PA (a specific plasminogen activator) and stejnobin (a fibrinogen-clotting enzyme) purified from the same venom, stejnefibrase-1, -2 and -3 were able to hydrolyze several chromogenic substrate. On the other hand, different from TSV-PA and stejnobin, stejnefibrase-1, -2 and -3 did not activate plasminogen and did not possess fibrinogen-clotting activity. The three purified enzymes directly degraded fibrinogen to small fragments and rendered it unclottable by thrombin. Stejnefibrase-2 degraded preferentially Bbeta-chain while stejnefibrase-1 and -3 cleaved concomitantly Aalpha and Bbeta-chains of fibrinogen. None of these proteases degraded the gamma-chain of fibrinogen. When correlated with the loss of clottability of fibrinogen, the most active enzyme was stejnefibrase-1. The activities of the three enzymes were inhibited by phenylmethylsulfonyl fluoride (PMSF) and p-nitrophenyl-p-guanidinobenzoate (NPGB), indicating that like TSV-PA and stejnobin, they are venom serine proteases.

Characterization of a fibrinogen-clotting enzyme from Trimeresurus stejnegeri venom, and comparative study with other venom proteases

Trimeresurus stejnegeri venom which contains TSV-PA (a specific plasminogen activator sharing 60-70% sequence homology with venom fibrinogen-clotting enzymes), also possesses fibrinogen-clotting activity in vitro. A fibrinogen-clotting enzyme (stejnobin) has been purified to homogeneity by gel filtration and ion-exchange chromatography on a Mono-Q column. It is a single-chain glycoprotein with a mol. wt of 44,000. The NH2-terminal amino acid sequence of stejnobin shows great homology with venom fibrinogen-clotting enzymes and TSV-PA. Like TSV-PA, stejnobin was able to hydrolyse several chromogenic substrates. Comparative study of substrate specificities of stejnobin and other venom proteases purified in our laboratory was carried out on five chromogenic substrates. Stejnobin clotted human fibrinogen with a specific activity of 122 NIH thrombin-equivalent units/mg protein. However, stejnobin did not act on other blood coagulation factors, such as factor X, prothrombin and plasminogen. Diisopropyl fluorophosphate and phenylmethanesulfonyl fluoride inhibited its activity, whereas ethylenediamine tetracetic acid had no effect on it, indicating that it is a serine protease. Although stejnobin showed strong immunological cross-reaction with polyclonal antibodies raised against TSV-PA, it was interesting to observe that, unlike the case of TSV-PA, these antibodies did not inhibit the amidolytic and fibrinogen-clotting activities of stejnobin.

Effects of Pallas' viper (Agkistrodon halys pallas) venom on blood coagulation and characterization of a prothrombin activator

The action of Pallas' viper (Agkistrodon halys pallas) venom on blood coagulation was examined in vitro and a strong anticoagulant effect was observed. This action was abolished after treatment with a specific inhibitor of phospholipase A2 activity (p-bromophenacyl bromide), revealing a procoagulant action in low concentrations of treated venom (around 1 microgram/ml). The effect of the venom on haemostasis was further characterized by measuring its ability to activate purified blood coagulation factors. It is concluded that A. halys pallas venom contains prothrombin activation activity. A prothrombin activator (aharin) was purified from the venom by Sephadex G-75 gel filtration and ion-exchange chromatography on a Mono-Q column. It consisted of a single polypeptide chain, with a mol. wt of 63,000. Purified aharin possessed no amidolytic activity on chromogenic substrates. It did not act on other blood coagulation factors, such as factor X and plasminogen, nor did it cleave or clot purified fibrinogen. The prothrombin activation activity of aharin was readily inhibited by ethylenediamine tetracetic acid (a metal chelator), but specific serine protease inhibitors such as diisopropyl fluorophosphate and phenylmethanesulfonyl fluoride had no effect on it. These observations suggest that, like those prothrombin activators from Echis carinatus and Bothrops atrox venoms, the prothrombin activator from A. halys pallas venom is a metalloproteinase.

Epstein-Barr virus LMP1 modulates the malignant potential of gastric carcinoma cells involving apoptosis

About 10% of gastric carcinomas including lymphoepithelioma-like carcinoma and adenocarcinoma are associated with Epstein-Barr virus (EBV) infection. In EBV-associated gastric carcinomas, the tumor cells express Epstein-Barr nuclear antigen 1 (EBNA-1) but not EBNA-2, -3A, -3B, or -3C, leader protein, or latent membrane proteins (LMPs) because of gene methylation. Only a few exceptional cases have LMP1 expression in tumor cells as demonstrated by immunohistochemical studies. To elucidate the biological effects of LMP1 and the significance of its restricted expression in EBV-associated gastric carcinomas, the LMP1 gene was transferred into EBV-negative gastric carcinoma cell lines (SCM1 and TMC1) and into EBV-negative nasopharyngeal carcinoma (NPC) cells (HONE-1) as a control. The biological effects of LMP1 in gastric carcinoma cells were monitored in vitro and in vivo. These results showed that the consequence of LMP1 expression is a growth enhancement in NPC cells, but it is a growth suppression in gastric carcinoma cells. The LMP1-expressing gastric carcinoma cells had a reduced growth rate, colony-forming efficiency, mean colony size, and tumorigenicity and a lower malignant cytological grade. The reduced growth rate, colony-forming efficiency, and mean colony size were partially reversible in vitro with treatment with LMP1 antisense oligonucleotide. In addition, enhanced apoptosis was found in the LMP1-expressing gastric carcinoma cells. This suggests that LMP1 may negatively modulate the malignant potential of gastric carcinoma cells via an enhancement of apoptosis. We concluded that the restriction of LMP1 expression in EBV-associated gastric carcinomas may lead to a growth advantage for tumor cells by avoiding LMP1 apoptotic effects and immunologically mediated elimination.

The Department of Molecular Medicine at the University of Texas Institute of Biotechnology

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Mitosin (a new proliferation marker) correlates with clinical outcome in node-negative breast cancer

Tumor proliferation rate is an important prognostic factor in breast cancer, and S-phase fraction (SPF), as measured by flow cytometry, is the most clinically validated of several methods for measuring it. However, flow cytometry is not well suited to evaluating the formalin-fixed, paraffin-embedded tumors that are routinely available or to the increasing number of small breast cancers. These and other limitations have motivated research into alternative methods for measuring proliferation, including immunohistochemistry (IHC) against cell cycle-related antigens, which are better suited for the evaluation of small archival tissue samples. Mitosin is a recently described 350 kD nuclear phosphoprotein that is expressed in the late G1, S, G2, and M phases of the cell cycle but not in G0. Using a new monoclonal antibody (14C10), this pilot study evaluated mitosin expression by IHC in a series of 386 node-negative, formalin-fixed, archival breast cancers and correlated the results with several prognostic factors and clinical outcome (median follow-up, 78 months; range 3-214 months). The median and range of mitosin positive cells were 7% and 1-47%, respectively. There was a strong positive correlation between mitosin and SPF (r = 0.57; P = 0.0001), and there were significant negative correlations with estrogen receptor, progesterone receptor, and patient age. Mitosin was not related to overall survival in this pilot study. However, in a univariate cutpoint analysis of disease-free survival (DFS), patients with high levels of mitosin (>9% positive cells) had significantly worse DFS than did patients with lower levels (68% versus 84% at 5 years, respectively). In a multivariate analysis of DFS, large tumor size (>2 cm) and high mitosin were the only independently significant predictors of recurrence (relative risks = 2.47 and 1.72, respectively) in a model containing the additional factors estrogen receptor, progesterone receptor, patient age, and SPF. These preliminary results suggest that mitosin as assessed by IHC may be superior to SPF as a prognostic factor in node-negative breast cancer, but additional studies are necessary to validate these promising findings.

Mutations of N-terminal regions render the retinoblastoma protein insufficient for functions in development and tumor suppression

To assess biological roles of the retinoblastoma protein (RB), four independent transgenic mouse lines expressing human RB with different deletions in the N-terminal region (RBdeltaN) were generated and compared with mice expressing identically regulated, full-length RB. Expression of both RB and RBdeltaN caused developmental growth retardation, but the wild-type protein was more potent. In contrast to wild-type RB, the RBdeltaN proteins were unable to rescue Rb-/- mice completely from embryonic lethality. Embryos survived until gestational day 18.5 but displayed defects in the terminal differentiation of erythrocytes, neurons, and skeletal muscle. In Rb+/- mice, expression of the RBdeltaN transgenes failed to prevent pituitary melanotroph tumors but delayed tumor formation or progression. These results strongly suggest that N-terminal regions are crucial for embryonic and postnatal development, tumor suppression, and the functional integrity of the entire RB protein. Furthermore, these transgenic mice provide models that may begin to explain human families with low-penetrance retinoblastoma and mutations in N-terminal regions of RB.

Apoptosis occurs more frequently in intraductal carcinoma than in infiltrating duct carcinoma of human breast cancer and correlates with altered p53 expression: detected by terminal-deoxynucleotidyl-transferase-mediated dUTP-FITC nick end labelling (TUNEL)

AIMS

We examined the relationship between apoptosis and three different major stages of human breast carcinoma: intraductal carcinoma (DCIS), infiltrating duct carcinoma (IDC) and metastatic carcinoma in lymph nodes. We also determined the correlation between apoptosis and oestrogen receptor (ER), progesterone receptor (PR) and p53.

METHODS AND RESULTS

The study investigates the extent of apoptosis in 63 breast carcinomas by in-situ end-labelling, in formalin-fixed, paraffin-processed tissue sections. The 63 breast carcinomas, included 22 DCISs, 26 IDCs, three infiltrating lobular carcinomas (ILC) and 12 metastatic lymph nodes. The apoptotic labelling index was higher in DCIS than IDC and metastatic carcinoma (P < 0.001, P < 0.007, respectively). By immunohistochemistry, we also analysed p53, ER and PR. Apoptosis correlated significantly with p53 (r = 0.748, P = 0.0004) in IDC. Also, ER correlated significantly with PR (r = 0.629, P = 0.00001). No apparent correlation was found between the apoptosis and ER or PR.

CONCLUSION

Our data suggest that not only does apoptosis differ between intraductal carcinoma and infiltrating carcinoma but also it might be regulated by altered p53 expression.

Interleukin-1 receptor antagonist modulates the progression of a spontaneously occurring IgA nephropathy in mice

Cytokines, such as interleukin-1 (IL-1), may play a key role in the pathogenesis of IgA nephropathy (IgAN). This study was conducted to evaluate the effects of IL-1 receptor antagonist (IL-1ra) in the treatment of a spontaneously occurring experimental IgAN in established phase. ddY mice (12/group) were injected twice daily with 3 mg/kg of IL-1ra, intraperitoneally, for 8 consecutive weeks. The placebo mice were injected with saline only. As normal controls, ddY mice, which were not treated with IL-1ra or saline, were killed at 6 weeks of age. Results showed a significant reduction of proteinuria in the IL-1ra-treated mice, compared with saline-treated mice (urinary albumin/creatinine, 0.24 +/- 0.04 v 0.39 +/- 0.03, P < 0.001). A significant improvement of renal 51Cr-EDTA (ethylenediaminetetra-acetic acid) clearance was observed in the IL-1ra-treated mice (t1/2, 12 +/- 2.7 minutes, compared with saline-treated mice 25 +/- 2.0 minutes, P < 0.001). Similarly, serum levels of creatinine (1.0 +/- 0.4 v 2.4 +/- 0.3 mg/dL, P < 0.001) and urea nitrogen (46 +/- 6 v 58 +/- 2 mg/dL, P < 0.01) were significantly lower in IL-1ra-treated mice than in saline-treated mice. In renal tissue studies, the IL-1ra-treated mice exhibited significantly decreased mesangial cell proliferation, compared with saline-treated mice (P < 0.001), as shown by light and electron microscopy. In addition, the IL-1ra-treated mice showed significantly lower glomerular expression of collagen type IV, fibronectin, laminin, and IL-6 (P < 0.001) than saline-treated mice, although they still showed higher glomerular expression of collagen type IV (P < 0.01), fibronectin (P < 0.01), laminin (P < 0.001), IL-1 (P < 0.001), and IL-6 (P < 0.01) than did normal control mice. Meanwhile, glomerular C3 deposition was significantly lower in IL-1ra-treated mice than in saline-treated mice (P < 0.001). These findings indicate that IL-1ra partially prevented the progression of spontaneously occurring IgAN in this experimental model. Data from these experiments also confirm the pathogenic effects of IL-1 in the established phase of IgAN in ddY mice.

HEC, a novel nuclear protein rich in leucine heptad repeats specifically involved in mitosis

The protein encoded by the human gene HEC (highly expressed in cancer) contains 642 amino acids and a long series of leucine heptad repeats at its C-terminal region. HEC protein is expressed most abundantly in the S and M phases of rapidly dividing cells but not in terminal differentiated cells. It localizes to the nuclei of interphase cells, and a portion distributes to centromeres during M phase. Inactivation of HEC by microinjection of specific monoclonal antibodies into cells during interphase severely disturbs the subsequent mitoses. Disordered sister chromatid alignment and separation, as well as the formation of nonviable cells with multiple, fragmented micronuclei, are common features observed. These results suggest that the HEC protein may play an important role in chromosome segregation during M phase.

Identification of cellular TSG101 protein in multiple human breast cancer cell lines

tsg101 was identified as a tumor susceptibility gene by homozygous functional inactivation of allelic loci in mouse 3T3 fibroblasts. The human homologue was mapped at chromosome 11p15.1-2 and found to have intragenic deletion in 7 of 15 breast cancer specimens. To further confirm the relevance of defects in this gene to breast cancer, antibodies specific for the putative gene product were prepared and used to identify cellular TSG101 protein. The antibodies recognized a 46-kDa protein in human retinoblastoma WERI-27 cells labeled with [35S]methionine. This protein was not detected with preimmune sera. In cell fractionation studies, the 46-kDa protein cofractionating with glutathione S-transferase was found mainly in the cytoplasm. Similarly, when cells were immunostained with anti-TSG101 antibodies, fluorescence was localized in the cytoplasm of most of the cells. A full-size 46-kDa TSG101 protein was detected in a panel of 10 breast cancer cell lines and 2 normal breast epithelial cell lines with the same antibodies. Consistently, the full-length TSG101 mRNA was also detected in these breast cells using reverse transcription-PCR. These results indicate that homozygous intragenic deletion of TSG101 is rare in breast cancer cells.

Earlier onset of melanotroph carcinogenesis in mice with inherited mutant paternal allele of the retinoblastoma gene

The role of genomic imprinting in the development of tumors with defective retinoblastoma protein function remains debatable. Disruption of either parental allele of the murine retinoblastoma (Rb) gene is sufficient for spontaneous melanotroph carcinogenesis to occur in almost all Rb+/- mice. Nevertheless, mice with a disrupted paternal Rb allele succumb to tumors faster. In these animals, the first foci of proliferating atypical Rb-negative cells appear and progress to overtly malignant tumors earlier. In addition, more foci of early atypical proliferation are observed. In Rb+/- mice, however, parental origin influences neither Rb expression nor proliferation of melanotrophs. Accordingly, Rb-/- mice rescued by the human RB transgene transmitted either paternally or maternally have similar survival rates. Taken together, the data point to the existence of an imprinted gene in an Rb-linked locus. The function of this gene affects the onset of melanotroph carcinogenesis, likely by controlling preferential survival of the cells with secondary loss of the Rb maternal allele. Rb+/- mice may serve as useful models to identify and characterize genomic imprinting mechanisms influencing carcinogenesis associated with Rb loss of function.

HEC binds to the seventh regulatory subunit of the 26 S proteasome and modulates the proteolysis of mitotic cyclins

A newly identified nuclear protein rich in leucine heptad repeats called HEC is important for mitosis. To elucidate its mechanism of action, the region containing leucine heptad repeats was used to identify cellular proteins that potentially interact with HEC. Complementary DNAs encoding several proteins including MSS1, p45, Nek2, and Smc1/Smc2, known to be important for G2/M progression, were identified. The interaction between HEC and MSS1, the seventh regulatory subunit of the 26 S proteasome, was further demonstrated by in vitro GST pull-down assays. HEC is not a part of the 26 S proteasome and interacts with MSS1 only when it is dissociated from the complex during M phase. Purified MSS1 specifically hydrolyzes ATP, an activity inhibited by HEC. In addition, HEC inhibits the proteolysis of mitotic cyclin B in vitro. Consistent with this biochemical activity, ectopic expression of HEC inhibits the degradation of mitotic cyclins after telophase, resulting eventually in cell death. These results show that HEC is a negative regulator of MSS1 and suggest that it may modulate M phase progression, in part, through the regulation of proteasome-mediated degradation of cell cycle regulatory proteins.

[The retinoblastoma gene: from its basic understanding as a signal mediator for growth and differentiation to its use in the treatment of cancer]

The retinoblastoma gene (RB) plays important roles in the genesis of human cancers. Several pieces of evidence have shown that the retinoblastoma protein (Rb) has dual roles in gating cell cycle progression and promoting cellular differentiation. The molecular mechanisms involved in these roles have been elucidated in some biological systems: Rb sequesters the transcription factors of E2F-1 to regulate entry of cell cycle, but enhances the activities of transcription factors such as C/ EBPs to initiate terminal differentiation. Thus, the Rb protein can serve as a mediator of extracellular signals for growth or differentiation. RB also has a tumor suppression function. Introduction of wild-type RB into human tumor cells deficient for RB suppresses their tumorigenicity in nude mice. Similarly, mice with RB+/- genotypes created by gene knockout methods spontaneously develop melanotrophic tumors with complete penetrance. Immune-competent RB+/- mice benefited significantly from adenovirus-mediated RB gene therapy. The fundamental knowledge of Rb function will allow us to take the next steps toward the use of tumor suppressor genes in the treatment of human cancer.

A thyroid hormone receptor coactivator negatively regulated by the retinoblastoma protein

The retinoblastoma protein (Rb) plays a critical role in cell proliferation, differentiation, and development. To decipher the mechanism of Rb function at the molecular level, we have systematically characterized a number of Rb-interacting proteins, among which is the clone C5 described here, which encodes a protein of 1,978 amino acids with an estimated molecular mass of 230 kDa. The corresponding gene was assigned to chromosome 14q31, the same region where genetic alterations have been associated with several abnormalities of thyroid hormone response. The protein uses two distinct regions to bind Rb and thyroid hormone receptor (TR), respectively, and thus was named Trip230. Trip230 binds to Rb independently of thyroid hormone while it forms a complex with TR in a thyroid hormone-dependent manner. Ectopic expression of the protein Trip230 in cells, but not a mutant form that does not bind to TR, enhances specifically TR-dependent transcriptional activity. Coexpression of wild-type Rb, but not mutant Rb that fails to bind to Trip230, inhibits such activity. These results not only identify a coactivator molecule that modulates TR activity, but also uncover a role for Rb in a pathway that responds to thyroid hormone.

Interaction of the nuclear matrix-associated region (MAR)-binding proteins, SATB1 and CDP/Cux, with a MAR element (L2a) in an upstream regulatory region of the mouse CD8a gene

Matrix-associated regions (MARs), AT-rich DNA segments that have an affinity for the nuclear matrix, have been shown to play a role in transcriptional regulation of eukaryotic genes. The present study demonstrates that a DNA element, called L2a, which has been implicated in the transcriptional regulation of the mouse CD8a gene encoding an important T cell coreceptor, is a MAR. Moreover, the identities of two nuclear proteins, L2a-P1 and L2a-P2, previously shown to bind to the L2a element, have been determined. The L2a-P1 protein found to be present in all CD8-positive T cell lines tested is SATB1, a known MAR-binding protein. The widely expressed L2a-P2 protein is CDP/Cux, a MAR-binding protein that has been associated with repression of gene transcription. Interaction of both proteins with the L2a element was studied using the missing nucleoside approach, DNase I footprinting, and electrophoretic mobility shift assays with wild type and mutant L2a elements. The data suggest that CDP/Cux bound to the L2a element is displaced by binding of SATB1 and the accompanying conformational change in the DNA lying between the primary binding sites of SATB1 and CDP/Cux. We suggest that displacement of CDP/Cux by SATB1 favors transcription of the CD8a gene, possibly by enhancing or altering its association with the nuclear matrix.

Adenocarcinoma combined with malignant peripheral nerve sheath tumor of the gallbladder

Adenocarcinoma of the gallbladder combined with a malignant peripheral nerve sheath tumor (MPNST) in the gallbladder in an 81-year-old woman is reported. The resected gallbladder showed two distinct tumor components, the epithelioid type of MPNST and adenocarcinoma with areas of mucin production. Although the immediate postoperative course was uneventful, a pathologic fracture of her right upper femur developed 4 months after the cholecystectomy. The pathology was determined to be a feature of metastatic MPNST rather than of adenocarcinoma. A whole body bone scan revealed multiple metastases, including the left parietal skull, left ninth rib, seventh thoracic vertebra, and right upper third of the femur. Despite cholecystectomy and postoperative irradiation therapy, she died 6 months after diagnosis of the tumor. Without an autopsy the primary site of the MPNST was unknown. We found that the prognosis was very poor in patients with distal metastatic MPNST, especially in older patients.

Association between Epstein-Barr virus and Burkitt's lymphoma in Taiwan

BACKGROUND

The association between Epstein-Barr virus (EBV) and Burkitt's lymphoma (BL) in Taiwan is not clear. In this study, the authors attempted to determine the frequency of the occurrence of EBV infection in patients with BL in Taiwan.

METHODS

A retrospective study was performed using a nonisotopic in situ hybridization technique to detect the presence of EBV-encoded small RNAs (EBERs) in paraffin embedded BL tissues. Tissues of other types of B-cell non-Hodgkin's lymphoma (NHL) were used as controls. Immunohistochemical staining was performed to examine the presence of an EBV-encoded protein, latent membrane protein (LMP), and p53 in specimens.

RESULTS

EBERs were detectable in 10 of 18 BL specimens. It was present in the cervical lymph nodes (LNs) in six of the seven cases of cervical tumors, in the maxillary region in one case, in one of two cases of axillary LNs, and in the abdominal tumors in two of the seven cases of intraabdominal disease. EBER positive cells were diffusely present in all tumors except in one abdominal BL, in which only a few EBER positive cells were scattered in a small part of the tumor. EBER positive cells were not detected in the case with BL in an inguinal LN and in the seven cases with intraabdominal tumors. Immunohistochemical studies showed that LMP and p53 were expressed in 3 and 4 of the 18 cases, respectively. In another 20 NHLs in peripheral LNs, EBERs were detectable in only 1 case of diffuse large cell histology with numerous reactive T cells in which only large tumor cells expressed EBERs and LMP. EBERs were not detected in any of the ten cases of extranodal NHL.

CONCLUSIONS

In Taiwan, EBV is frequently associated with BL occurring outside the abdomen but rarely with intraabdominal BL. The overall association between EBV and BL in Taiwan is intermediate compared with other regions of the world. These results support the theory that the frequency of EBV associated with BL is influenced by the endemicity of EBV and/or the socioeconomic status of a country.

CG island methylation changes near the GSTP1 gene in prostatic carcinoma cells detected using the polymerase chain reaction: a new prostate cancer biomarker

Cancer-associated somatic genome alterations offer great promise as cancer biomarkers. Here we describe a new biomarker for human prostate cancer: extensive methylation of deoxycytidine nucleotides distributed throughout a 5' "CG island" region of the pi-class glutathione S-transferase gene (GSTP1). Using the PCR to amplify a GSTP1 promoter sequence fragment containing 12 recognition sites for HpaII and MspI, 52 of 57 (91%) prostatic carcinoma DNA specimens demonstrated extensive somatic increases in deoxycytidine methylation, detected as amplification of target GSTP1 promoter sequences following HpaII digestion, but not following MspI treatment. Using nested primer sets, a sensitive PCR assay for extensive GSTP1 CG island methylation changes was developed that was capable of detecting 200 pg of prostate cancer cell DNA among 1 microgram of normal leukocyte DNA. This GSTP1 CG island DNA methylation assay, which targets a somatic genome change present in most prostate cancer cells but not in normal cells, may serve as a new molecular diagnosis and staging tool to aid in prostate cancer detection and treatment.

Anti-IL-4 monoclonal antibody prevents antibiotics-induced active fatal anaphylaxis

We previously reported that anti-IL-4 mAb (11B11) failed to prevent protein-induced fatal murine anaphylaxis. To investigate the effect of anti-IL-4 on hapten-induced anaphylaxis, a model of murine anaphylaxis induced by antibiotics, penicillin V (Pen V) and cephalothin (CET), was developed, and the effect of anti-IL-4 on the anaphylaxis was observed. Pen V and CET induced 100 and 70 to 90% fatal reactions, respectively, when C57BL/6 mice were sensitized i.p. with 500 microg of antibiotic-OVA conjugate with 2 x 10(9) Bordetella pertussis and 1.0 mg of alum and challenged i.v. with 100 microg of antibiotic-BSA conjugate 14 days later. Serum taken from mice sensitized to Pen V passively sensitized normal mice to develop systemic anaphylaxis, and this ability of the serum was abrogated by heating at 56 degrees C for 2 h or depletion of IgE, but not IgG, Abs. Thus, the antibiotic-induced fatal reaction was an IgE-dependent anaphylactic reaction. Administration of anti-IL-4 at the beginning of sensitization completely prevented the fatal anaphylactic reactions to both Pen V and CET. This effect of anti-IL-4 was associated with its suppressive activity on antibiotic-specific serum IgE, but not IgG, levels. More importantly, anti-IL-4 therapy in previously sensitized mice was also effective in preventing the fatal reactions and rapidly reduced the established IgE levels. This study provides a new animal model of hapten-induced anaphylaxis and indicates that blocking of IL-4 activity may be beneficial in allergic diseases caused by a variety of haptens in which IgE Abs play a major role.