CD40 ligation alters the cell cycle of differentiating keratinocytes

CD40 is expressed in normal human keratinocytes, especially in the basal cell layer. We have recently reported that CD40 ligation strongly inhibits keratinocyte proliferation and induces their differentiation. In this study, the CD40 pathway that prevents keratinocyte growth was investigated. We first reported that interferon-gamma treatment potentiated the CD40-mediated inhibition of keratinocyte proliferation. CD40-CD40 ligand interactions, in the presence or absence of interferon-gamma, neither enhanced spontaneous keratinocyte apoptosis, nor did it enhance apoptosis induced by various agents. More importantly, we showed that CD40 signaling altered the keratinocyte cell cycle, as demonstrated by a decreasing number of cells in the G1 and S phases and an accumulation in G2/M phase of the cell cycle. Furthermore, western blot analysis of cell cycle regulatory proteins, showed a decrease in cyclin A and E expression in CD40-activated keratinocytes. Collectively, these results indicate that CD40 ligation inhibits keratinocyte renewal by a mechanism independent of cell apoptosis and that modulation of the keratinocyte cell cycle is an additional outcome of CD40 signaling.

Primary angioleiomyoma of the iliac bone: clinical pathological study of one case with flow cytometric DNA content and S-phase fraction analysis

We report on a primary angioleiomyoma of the right iliac bone in a 28-year-old woman. To our knowledge this is the 16th reported case of a primary leiomyoma of bone, the 9th reported primary osseous angioleiomyoma and the first description of a primary angioleiomyoma located in the iliac bone. The problems of differentiating primary leiomyoma of bone from primary or metastatic leiomyosarcoma of bone are stressed. A literature review of primary leiomyomas of bone is presented.

Hepatoma-derived growth factor stimulates smooth muscle cell growth and is expressed in vascular development

Hepatoma-derived growth factor (HDGF) is the first member identified of a new family of secreted heparin-binding growth factors highly expressed in the fetal aorta. The biologic role of HDGF in vascular growth is unknown. Here, we demonstrate that HDGF mRNA is expressed in smooth muscle cells (SMCs), most prominently in proliferating SMCs, 8-24 hours after serum stimulation. Exogenous HDGF and endogenous overexpression of HDGF stimulated a significant increase in SMC number and DNA synthesis. Rat aortic SMCs transfected with a hemagglutinin-epitope-tagged rat HDGF cDNA contain HA-HDGF in their nuclei during S-phase. We also detected native HDGF in nuclei of cultured SMCs, of SMCs and endothelial cells from 19-day fetal (but not in the adult) rat aorta, of SMCs proximal to abdominal aortic constriction in adult rats, and of SMCs in the neointima formed after endothelial denudation of the rat common carotid artery. Moreover, HDGF colocalizes with the proliferating cell nuclear antigen (PCNA) in SMCs in human atherosclerotic carotid arteries, suggesting that HDGF helps regulate SMC growth during development and in response to vascular injury.

UCN-01 selectively enhances mitomycin C cytotoxicity in p53 defective cells which is mediated through S and/or G(2) checkpoint abrogation

We have previously reported that UCN-01 (7-hydroxystaurosporine), a protein kinase inhibitor that is under clinical trials as an anti-cancer agent in the USA and Japan, enhanced the anti-tumor activity of mitomycin C (MMC) in vitro and in vivo. Subsequent studies from other laboratories revealed that UCN-01 could selectively enhance cytotoxicity of DNA damaging agents in p53 defective cells and that this was mediated by abrogation of S and /or G(2) arrest by UCN-01. In this study, we report that UCN-01 selectively enhances the cytotoxicity of MMC in human p53 mutant cell lines. In contrast, UCN-01 showed little, if any, effect on MMC cytotoxicity in human p53 wild-type cell lines. Terminal deoxynucleotidyl transferase (TdT)-mediated dUTP-nick end-labeling (TUNEL) assay revealed that the combination of MMC with UCN-01 increased DNA breaks consistent with apoptosis in p53 defective A431 epidermoid carcinoma cells. In p53 wild-type MCF-7 breast carcinoma cells, the cyclin-dependent kinase inhibitor protein p21/WAF1 was markedly induced after the treatment with MMC alone, although this response was significantly delayed from the time of MMC treatment. Detailed cell-cycle studies revealed that UCN-01 abrogated S and G(2) phase accumulation induced by MMC in p53 defective cells and to a lesser extent in p53 wild-type cell lines. The abrogation of arrest in p53 wild-type cells was observed prior to significant induction of the p53 response. Since MMC was less effective against p53 defective cell lines than against p53 wild-type cell lines and UCN-01 selectively enhanced MMC cytotoxicity in p53 defective cell lines, UCN-01 may provide a new modality of MMC-based cancer chemotherapy, particularly in p53 defective cancer patients.

Anti-apoptotic phenotype is associated with decreased locoregional recurrence rate in breast cancer

PURPOSE

Tumor stage and nodal status are the most important factors predicting locoregional recurrence in breast cancer. We wanted to investigate the prognostic value of some newer molecular genetic markers for the occurrence of a locoregional recurrence, in order to improve the selection of patients for locoregional adjuvant therapy.

METHODS

Bcl-2, p53, MIB-1, pS2 and CD44v6 were determined immunohistochemically on formalin-fixed and paraffin embedded tumour tissues of 163 patients treated by modified radical mastectomy between 1982 and 1987. Postoperative irradiation was given to 35 patients to the intermammary chain only and to only 13 (8%) patients to the chest wall with or without the regional lymph nodes. Node-positive patients were treated with CAF adjuvant chemotherapy and were randomized for whether or no additional Medroxyprogesteroneacetate (MPA). A multivariate analysis was performed on a number of potential prognostic factors. The risk for locoregional recurrence was estimated using the competing risk approach.

RESULTS

After a median period of 7.5 years 28 patients developed a locoregional recurrence. The cumulative incidence of loco-regional recurrence at 10 years was 17%. Bcl-2 and p53 were found to be independent factors predicting locoregional recurrence, whereas a trend was found for MIB-1. Increased Bcl-2 as well as p53 expression were associated with a decreased risk, whereas the increased presence of MIB-1 was associated with an increased risk.

CONCLUSION

Results indicate that molecular markers of apoptosis as well as proliferation provide additional information for the risk of locoregional recurrence after modified radical mastectomy. If confirmed, these markers may play a role in the selection of appropriate locoregional adjuvant treatment after primary surgery.

Differential effect of Rac and Cdc42 on p38 kinase activity and cell cycle progression of nonadherent primary mouse fibroblasts

The Rho GTPases play an important role in transducing signals linking plasma membrane receptors to the organization of the cytoskeleton and also regulate gene transcription. Here, we show that expression of constitutively active Ras or Cdc42, but not RhoA, RhoG, and Rac1, is sufficient to cause anchorage-independent cell cycle progression of mouse embryonic fibroblasts. However, in anchorage free conditions, whereas activation of either Cdc42 or Ras results in cyclin A transcription and cell cycle progression, Cdc42 is not required for Ras-mediated cyclin A induction, and the two proteins act in a synergistic manner in this process. Surprisingly, the ability of Cdc42 to induce p38 MAPK activity in suspended mouse embryonic fibroblast was impaired. Moreover, inhibition of p38 activity allowed Rac1 to induce anchorage-independent cyclin A transcription, indicating that p38 MAPK has an inhibitory function on cell cycle progression of primary fibroblasts. Finally, a Rac mutant, which is unable to induce lamellipodia and focal complex formation, promoted cyclin A transcription in the presence of SB203580, suggesting that the organization of the cytoskeleton is not required for anchorage-independent proliferation. This demonstrates a novel function for Cdc42, distinct from that of Rac1, in the control of cell proliferation.

Ras1 promotes cellular growth in the Drosophila wing

The Ras GTPase links extracellular mitogens to intracellular mechanisms that control cell proliferation. To understand how Ras regulates proliferation in vivo, we activated or inactivated Ras in cell clones in the developing Drosophila wing. Cells lacking Ras were smaller, had reduced growth rates, accumulated in G1, and underwent apoptosis due to cell competition. Conversely, activation of Ras increased cell size and growth rates and promoted G1/S transitions. Ras upregulated the growth driver dMyc, and both Ras and dMyc increased levels of cyclin E posttranscriptionally. We propose that Ras primarily promotes growth and that growth is coupled to G1/S progression via cyclin E. Interestingly, upregulation of growth by Ras did not deregulate G2/M progression or a developmentally regulated cell cycle exit.

Variation of flow cytometric DNA measurement in 1,485 primary breast carcinomas according to guidelines for DNA histogram interpretation

From 1990-1996, 1,485 previously untreated invasive breast carcinomas were sampled by a pathologist for flow cytometric DNA analysis. The aim of the present work was to study the variations of flow cytometric DNA ploidy and S-phase evaluation according to the conditions of DNA histogram interpretation. Results obtained with the American Consensus guidelines of 1993 and the François Baclesse Department of Pathology's own guidelines are presented. According to the percentage of events taken into account to identify a DNA aneuploid peak, the proportion of DNA diploid cases can change from 35-39%. For S-phase evaluation, although the two guidelines were quite different, the results of S-phase cutoff were identical. Whichever guidelines were used, there was a strong relationship between DNA ploidy and/or S-phase and classical clinicopathological factors (T, N, histological type, grade, receptor status, or lymphatic invasion), with the exception of age, whose correlation was discrepant with S phase according to the set of guidelines. Whichever guidelines were used, ploidy and S phase correlated strongly with survival (overall, metastasis-free, or recurrence-free). Hence we recommend the use of the American consensus guidelines, despite minor imperfections, because they are now well-known, allow a high yield in the ratio of assessable S phases, and permit standardization in the technical processing and reporting of S phases, thanks to the use of terciles.

Progression of meiotic DNA replication is modulated by interchromosomal interaction proteins, negatively by Spo11p and positively by Rec8p

Spo11p is a key mediator of interhomolog interactions during meiosis. Deletion of the SPO11 gene decreases the length of S phase by approximately 25%. Rec8p is a key coordinator of meiotic interhomolog and intersister interactions. Deletion of the REC8 gene increases S-phase length, by approximately 10% in wild-type and approximately 30% in a spo11Delta background. Thus, the progression of DNA replication is modulated by interchromosomal interaction proteins. The spo11-Y135F DSB (double strand break) catalysis-defective mutant is normal for S-phase modulation and DSB-independent homolog pairing but is defective for later events, formation of DSBs, and synaptonemal complexes. Thus, earlier and later functions of Spo11 are defined. We propose that meiotic S-phase progression is linked directly to development of specific chromosomal features required for meiotic interhomolog interactions and that this feedback process is built upon a more fundamental mechanism, common to all cell types, by which S-phase progression is coupled to development of nascent intersister connections and/or related aspects of chromosome morphogenesis. Roles for Rec8 and/or Spo11 in progression through other stages of meiosis are also revealed.

Plasticity of retrovirus-labelled myotubes in the newt limb regeneration blastema

Two important indices of myogenic differentiation are the formation of syncytial myotubes and the postmitotic arrest from the cell cycle, both of which occur after fusion of mononucleate cells. We show here that these indices are reversed in the environment of the urodele limb regeneration blastema. In order to introduce an integrated (genetic) marker into newt myotubes, we infected mononucleate cells in culture with a pseudotyped retrovirus expressing human placental alkaline phosphatase (AP). After fusion the myotubes expressed AP and could be purified by sieving and micromanipulation so as to remove all mononucleate cells. When such purified retrovirus-labelled myotubes were implanted into a limb blastema they gave rise to mononucleate progeny with high efficiency. Purified myotubes labelled with fluorescent lipophilic cell tracker dye also gave rise to mononucleate cells; myotubes which were double labelled with the tracker dye and a nuclear stain gave rise to double-labelled mononucleate progeny. Nuclei within retrovirus-labelled myotubes entered S phase as evidenced by widespread labelling after injection of implanted newts with BrdU. The relation between the two aspects of plasticity is a critical further question.

Regulation of E2F1 activity by acetylation

During the G(1) phase of the cell cycle, an E2F-RB complex represses transcription, via the recruitment of histone deacetylase activity. Phosphorylation of RB at the G(1)/S boundary generates a pool of 'free' E2F, which then stimulates transcription of S-phase genes. Given that E2F1 activity is stimulated by p300/CBP acetylase and repressed by an RB-associated deacetylase, we asked if E2F1 was subject to modification by acetylation. We show that the p300/CBP-associated factor P/CAF, and to a lesser extent p300/CBP itself, can acetylate E2F1 in vitro and that intracellular E2F1 is acetylated. The acetylation sites lie adjacent to the E2F1 DNA-binding domain and involve lysine residues highly conserved in E2F1, 2 and 3. Acetylation by P/CAF has three functional consequences on E2F1 activity: increased DNA-binding ability, activation potential and protein half-life. These results suggest that acetylation stimulates the functions of the non-RB bound 'free' form of E2F1. Consistent with this, we find that the RB-associated histone deacetylase can deacetylate E2F1. These results identify acetylation as a novel regulatory modification that stimulates E2F1's activation functions.

A comparison of the roles of p53 mutation and AraC inhibition in the enhancement of bleomycin-induced chromatid aberrations in mouse and human cells

Previous studies have shown that p53 is involved in the repair of bleomycin-induced DNA damage, and that the frequency of bleomycin-induced chromatid aberrations is elevated in G(2)-treated p53 null transgenic mouse embryo fibroblasts (MEF) as compared to isogenic controls. To further characterize p53-mediated DNA repair, we studied the effect of p53 status on the ability of the DNA repair inhibitor 1-ss-D-arabinofuranosylcytosine (AraC) to sensitize MEF to bleomycin-induced chromatid aberrations. Both p53+/+ and p53-/- MEF were treated in G(2) with 0 to 7.5 microg/ml bleomycin in the presence or absence of AraC (5x10(-5) M). The frequency of bleomycin-induced chromatid aberrations was significantly higher in p53-/- cells than wild-type cells in the absence of AraC. AraC treatment significantly increased the frequency of bleomycin-induced chromatid aberrations in p53+/+ MEF to the levels in p53-/- (no AraC) but had no effect in p53-/- MEF. These results suggest that an AraC-sensitive DNA repair component is altered or absent in p53-/- cells. Similar results were observed in p53-mutant WTK1 and wild-type TK6 human lymphoblast cells exposed to 0 to 3 microg/ml bleomycin in G(2). However, AraC did cause a small increase in bleomycin sensitivity in WTK1 cells. This difference from the p53-/- MEF response may be due to differences in p53-mutant phenotype. To determine whether mutation of p53 alters DNA replication fidelity, p53+/+ and p53-/- MEF were exposed to 0 to 1 microg/ml mitomycin C (MMC). MMC did not induce chromosome aberrations in either cell line treated in G(2) but did with the same effectiveness in both cell lines treated in S-phase. Thus, p53 deficiency does not affect DNA replication fidelity or the repair of MMC-induced DNA damage.

v-Abl utilizes multiple mechanisms to drive G1/S progression in fibroblasts

Transformation of 3T3 fibroblasts by the v-Abl tyrosine kinase replaces mitogenic and adhesion signals normally required for cell cycle progression. A 3T3 cell line conditionally transformed with v-Abl has been used to study v-Abl's effects on cell cycle in the context of either serum depletion or absence of adhesion signals. We show that E2F-dependent mRNAs, encoding proteins required for cell cycle progression, are induced by v-Abl. In addition, we identify two previously unknown targets of v-Abl signaling: (1) cyclin D1 and D2 mRNAs are induced upon v-Abl activation; and (2) the CDK inhibitor p27 is decreased upon v-Abl activation.

Differential regulation of p27(Kip1) expression by mitogenic and hypertrophic factors: Involvement of transcriptional and posttranscriptional mechanisms

Platelet-derived growth factor-BB (PDGF-BB) acts as a full mitogen for cultured aortic smooth muscle cells (SMC), promoting DNA synthesis and cell proliferation. In contrast, angiotensin II (Ang II) induces cellular hypertrophy as a result of increased protein synthesis, but is unable to drive cells into S phase. In an effort to understand the molecular basis for this differential growth response, we have examined the downstream effects of PDGF-BB and Ang II on regulators of the cell cycle machinery in rat aortic SMC. Both PDGF-BB and Ang II were found to stimulate the accumulation of G(1) cyclins with similar kinetics. In addition, little difference was observed in the expression level of their catalytic partners, Cdk4 and Cdk2. However, while both factors increased the enzymatic activity of Cdk4, only PDGF-BB stimulated Cdk2 activity in late G(1) phase. The lack of activation of Cdk2 in Ang II-treated cells was causally related to the failure of Ang II to stimulate phosphorylation of the enzyme on threonine and to downregulate p27(Kip1) expression. By contrast, exposure to PDGF-BB resulted in a progressive and dramatic reduction in the level of p27(Kip1) protein. The time course of p27(Kip1) decline was correlated with a reduced rate of synthesis and an increased rate of degradation of the protein. Importantly, the repression of p27(Kip1) synthesis by PDGF-BB was associated with a marked attenuation of Kip1 gene transcription and a corresponding decrease in Kip1 mRNA accumulation. We also show that the failure of Ang II to promote S phase entry is not related to the autocrine production of transforming growth factor-beta1 by aortic SMC. These results identify p27(Kip1) as an important regulator of the phenotypic response of vascular SMC to mitogenic and hypertrophic stimuli.

Different expression profiles of human cyclin B1 in normal PHA-stimulated T lymphocytes and leukemic T cells

BACKGROUND

In a previous work, we demonstrated with flow cytometry (FCM) methods that accumulation of human cyclin B1 in leukemic cell lines begins during the G(1) phase of the cell cycle (Viallard et al. , Exp Cell Res 247:208-219, 1999). In the present study, FCM was used to compare the localization and the kinetic patterns of cyclin B1 expression in Jurkat leukemia cell line and phytohemagglutinin (PHA)-stimulated normal T lymphocytes.

METHODS

Cell synchronization was performed in G(1) with sodium n-butyrate, at the G(1)/S transition with thymidine and at mitosis with colchicine. Cells (leukemic cell line Jurkat or PHA-stimulated human T-lymphocytes) were stained for DNA and cyclin B1 and analyzed by FCM. Western blotting was used to confirm certain results.

RESULTS

Under asynchronous growing conditions and for both cell populations, cyclin B1 expression was essentially restricted to the G(2)/M transition, reaching its maximal level at mitosis. When the cells were synchronized at the G(1)/S boundary by thymidine or inside the G(1) phase by sodium n-butyrate, Jurkat cells accumulated cyclin B1 in both situations, whereas T lymphocytes expressed cyclin B1 only during the thymidine block. The cyclin B1 fluorescence kinetics of PHA-stimulated T lymphocytes was strictly similar when considering T lymphocytes blocked at the G(1)/S phase transition by thymidine and in exponentially growing conditions. These FCM results were confirmed by Western blotting. The detection of cyclin B1 by Western blot in cells sorted in the G(1) phase of the cell cycle showed that cyclin B1 was present in the G(1) phase in leukemic T cells but not in normal T lymphocytes. Cyclin B1 degradation was effective at mitosis, thus ruling out a defective cyclin B1 proteolysis.

CONCLUSIONS

We found that the leukemic T cells behaved quite differently from the untransformed T lymphocytes. Our data support the notion that human cyclin B1 is present in the G(1) phase of the cell cycle in leukemic T cells but not in normal T lymphocytes. Therefore, the restriction point from which cyclin B1 can be detected is different in the two models studied. We hypothesize that after passage through a restriction point differing in T lymphocytes and in leukemic cells, the rate of cyclin B1 synthesis becomes constant in the S and G(2)/M phases and independent from the DNA replication cycle.

Prediction of clinical outcome from primary tamoxifen by expression of biologic markers in breast cancer patients

The aim of this study was to evaluate pretreatment clinical features and biological markers together with changes in these factors as predictors of response and relapse in patients receiving tamoxifen for primary breast cancer. Fine-needle aspiration cytology of the primary breast cancer was performed before tamoxifen treatment in 54 patients and repeated after therapy on day 14, day 60, or on both days in a subset of 35 patients. These samples were evaluated for estrogen receptor (ER), progesterone receptor (PgR), Ki67, S-phase fraction and ploidy. The overall response to tamoxifen was 57% (31 of 54 patients). Pretreatment ER and PgR significantly predicted for response by univariate analysis (P < 0.0001 and P < 0.003, respectively). By multivariate analysis, ER expression was the only independent predictor of response, and it was associated with 27 times the likelihood of response (95% confidence interval, 6-136). Increase in PgR and decrease in Ki67 on day 14 significantly predicted for response to tamoxifen (P < 0.03 and P < 0.04, respectively). Lack of ER, clinical node-positive disease, and failure to decrease Ki67 on day 14 were significantly associated with increased risk of relapse (P < 0.05). By multivariate analysis, ER expression was the only independent predictor of relapse (P < 0.005). Pretreatment and early changes in molecular marker expression may assist in the prediction of response and clinical outcome in primary breast cancer patients receiving tamoxifen.

Proliferative response of mantle cell lymphoma cells stimulated by CD40 ligation and IL-4

Mantle cell lymphoma (MCL) is a tumor of intermediate-size, IgM+, IgD+ B cells derived from the mantle zone of the germinal center. Little is known about its specific immunologic features or responsiveness to T cell-derived signals. In this work, we evaluated the proliferation and cell cycle properties of freshly isolated MCL cells after CD40 ligation, in the absence and presence of interleukin 4 (IL-4). In each MCL case examined, there was a marked growth-enhancing effect of these two stimuli characterized by improved viability, augmented expression of Ki-67, and induction of the proliferating cell nuclear antigen (PCNA). Cyclin D1 was expressed throughout the cell cycle in MCL cells induced to enter S phase. From these investigations, we conclude that the biology of MCL B lymphocytes is affected by CD154 (CD40 ligand) and IL-4, two signals usually provided by CD4+ T cells. The capacity to manipulate the activation and cell cycle state of MCL cells by these specific immunological stimuli may be exploited to confer susceptibility to chemotherapy agents and develop novel therapies in this disease.

The APC-hDLG complex negatively regulates cell cycle progression from the G0/G1 to S phase

The adenomatous polyposis coli (APC) gene is mutated in familial adenomatous polyposis and in many sporadic colorectal tumors. The carboxyl-terminal S/TXV motif of the APC gene product interacts with the PDZ domain of hDLG, the human homolog of the Drosophila lethal (1) discs larige-1 (dlg) tumor suppressor. In the present study, we found that overexpression of hDLG suppresses cell proliferation by blocking cell cycle progression from the G0/G1 to S phase. This inhibition of cell cycle progression was abolished when the PDZ, SH3 or guanylate kinase-like domain of hDLG was mutated. Moreover, overexpression of these mutant hDLGs partially interfered with the cell cycle blocking activity of APC. Consistent with this result, mutant APC lacking the S/TXV motif exhibited weaker cell cycle blocking activity than the intact APC. These results suggest that APC-hDLG complex formation plays an important role in transducing the APC cell cycle blocking signal.

Specific chromosome 1 breaks induced by human cytomegalovirus

Human cytomegalovirus (HCMV) is the major viral cause of birth defects and a serious problem for immunocompromised individuals. Here we show that infection of cells with HCMV during the S-phase of the cell cycle results in two specific chromosome 1 breaks at positions 1q42 and 1q21. We demonstrate that purified virions, and not infected cell supernatant alone, are responsible for the damage. In addition, we show that the specific breaks occur when different sources of fibroblasts and strains of HCMV are used. Incubation of the virus with neutralizing antibody prevents the induction of breaks. However, UV-inactivated virus is as efficient as untreated virus in inducing specific damage to chromosome 1. Thus, there is a requirement for viral adsorption/penetration, but not new viral gene expression. This HCMV-mediated induction of site-specific damage in actively dividing cells may provide clues for the development of neurological defects in the congenitally infected infant.

Deregulation of the p14ARF/MDM2/p53 pathway is a prerequisite for human astrocytic gliomas with G1-S transition control gene abnormalities

Deregulation of G1-S transition control in cell cycle is one of the important mechanisms in the development of human tumors including astrocytic gliomas. We have previously reported that approximately two-thirds of glioblastomas (GBs) had abnormalities of G1-S transition control either by mutation/homozygous deletion of RB1 or CDKN2A p16INK4A), or amplification of CDK4 (K. Ichimura et al., Oncogene, 13: 1065-1072, 1996). However, abnormalities of G1-S transition control genes may induce p53-dependent apoptosis in cells. Recent investigations suggest that p14ARF is induced in response to abnormal cell cycle entry and results in p53 accumulation by inhibiting MDM2-mediated transactivational silencing and degradation of p53. To investigate the roles of the G1-S transition control system and the p14ARF/MDM2/p53 pathway in the development of astrocytic gliomas, we examined abnormalities of genes involved in these regulatory pathways in a total of 190 primary human astrocytic gliomas of different malignancy grades [136 GBs, 39 anaplastic astrocytomas (AAs) and 15 astrocytomas (As)]. Sixty-seven percent of GBs (91/136) and 21% of AAs (8/39) had abnormalities of the G1-S control system either by mutation/homozygous deletion of RB1, CDKN2A or CDKN2B, or amplification of CDK4. Seventy-six percent of GBs (103 of 136), 72% of AAs (28 of 39), and 67% of As (10 of 15) had deregulated p53 pathway either by mutation of TP53, amplification of MDM2, or homozygous deletion/mutation of p14ARF. When all of the data were combined and compared, 96% of GBs (87 of 91) and 88% of AAs (7 of 8) with abnormal G1-S transition control also had deregulated p53 pathway. Thus, we demonstrate that deregulation of the G1-S transition control system was almost always accompanied by inactivation of the p53 pathway, clearly illustrating the cooperative roles of these two systems in the development/progression of primary human astrocytic gliomas.

Adozelesin triggers DNA damage response pathways and arrests SV40 DNA replication through replication protein A inactivation

The cyclopropylpyrroloindole anti-cancer drug, adozelesin, binds to and alkylates DNA. Treatment of human cells with low levels of adozelesin results in potent inhibition of both cellular and simian virus 40 (SV40) DNA replication. Extracts were prepared from adozelesin-treated cells and shown to be deficient in their ability to support SV40 DNA replication in vitro. This effect on in vitro DNA replication was dependent on both the concentration of adozelesin used and the time of treatment but was not due to the presence of adozelesin in the in vitro assay. Adozelesin treatment of cells was shown to result in the following: induction of p53 protein levels, hyperphosphorylation of replication protein A (RPA), and disruption of the p53-RPA complex (but not disruption of the RPA-cdc2 complex), indicating that adozelesin treatment triggers cellular DNA damage response pathways. Interestingly, in vitro DNA replication could be rescued in extracts from adozelesin-treated cells by the addition of exogenous RPA. Therefore, whereas adozelesin and other anti-cancer therapeutics trigger common DNA damage response markers, adozelesin causes DNA replication arrest through a unique mechanism. The S phase checkpoint response triggered by adozelesin acts by inactivating RPA in some function essential for SV40 DNA replication.

S phase-specific DNA-binding proteins interacting with the Hex and Oct motifs in type I element of the wheat histone H3 promoter

The type I element (CCACGTCANCGATCCGCG), consisting of the Hex motif (CCACGTCA) and the reverse-oriented Oct motif (GATCCGCG), is necessary and sufficient to confer the S phase-specific transcription of the wheat histone H3 (TH012) gene. The transcriptional regulation via the type I element is thought to occur through interactions between transcription factors which bind specifically to the Hex and Oct motifs. Here we report S phase-specific DNA-binding proteins interacting with the type I element in partially synchronized wheat cultured cells. Hex motif-binding proteins found here resembled HBP-1a, as reported previously in terms of DNA-binding specificity. DNA-binding activities of the HBP-1a-like proteins were modulated by phosphorylation/dephosphorylation. In the electrophoretic mobility shift assay of the wheat nuclear extract, we also found three Oct motif-specific binding proteins, named OBRF (octamer-binding regulatory factor)-1, -2 and -3. One of the HBP-1a-like proteins and OBRF-1 appeared predominantly at the S phase. Thus, it was supposed that these two factors play a crucial role in the S phase-specific regulation of wheat histone gene expression.

[DNA ploidy in epithelial ovarian cancer--an independent prognostic factor]

Ovarian cancer is the most lethal of the gynecological malignancies. One of the aims of the ongoing research in this field is the search for prognostic and/or predictive factors which can contribute to a more individualized patient treatment. All studies performed at The Norwegian Radium Hospital with regard to the prognostic significance of DNA ploidy in borderline, early and advanced ovarian cancer, were reviewed. The conclusions emanating from these studies were compared to the international literature. DNA ploidy analysis is of definite independent prognostic significance in borderline and early (FIGO stage I) ovarian cancer, and is of help in the selection of patients expected to benefit from adjuvant chemotherapy, or in whom a more conservative surgical procedure can be acceptable. DNA ploidy status is also of prognostic significance in advanced ovarian cancer; however, for the time being this information has no direct consequences for patient treatment. We conclude that DNA ploidy analysis should be incorporated in the routine histopathological evaluation of borderline and early (stage I) ovarian cancer.

Evaluation of DNA content and proliferative activity in prediction of short-term relapses in mammary carcinoma: a prospective study

DNA content according to six various ploidy classes was analysed by flow cytometry on fresh tumor tissue in 701 unselected, consecutive breast cancers. Age, menopausal status, tumor size, histology and in particular nodal status were also taken into consideration. Diploid and nondiploid mammary carcinomas differed significantly in values of proliferative indicators. In node positive patients nondiploid tumors were more frequent. In node negative and node positive breast cancer patients tumor grade strongly influenced disease free survival and in the last group hypertriploidy (1.6 < DI < or = 1.8) was also an independent prognostic factor. The combination of tumor grade and hypertriploidy permitted differentiation of three groups of node positive patients, differing in the risk of relapses.