Induction of apoptosis by wild-type p53 in a human colon tumor-derived cell line

Apoptosis and predisposition to oral cancer

The term apoptosis, also known as programmed cell death (PCD), was coined by developmental biologists a number of years ago to describe a form of cell death characterized by several unique morphological and biochemical features. Genetic studies of the round worm Caeneorhabditis elegans, a simple multicellular organism, first revealed apoptosis to be an integral part of the developmental program. Subsequently, the importance of apoptosis in higher organisms was demonstrated in several eukaryotic systems. [n mammals, apoptosis is widespread during embryogenesis and in adult tissues. It is required for normal tissue homeostasis and for clonal selection in the immune system. In both developing and adult organisms, apoptosis plays a central role in reinforcing appropriate cellular patterns and in regulating cell number by eliminating cells that are harmful or no longer needed. It is becoming increasingly clear that disruption in the apoptosis pathway can contribute to the development of a number of developmental, inflammatory, degenerative, and neoplastic diseases. The effector arm of the apoptotic program includes members of the Bcl-2 gene family that function as either death agonists or death antagonists. These proteins participate in an elaborate genetically controlled biochemical pathway that functions to maintain tissue and organ homeostasis and serve as a critical defense mechanism to guard against malignant transformation. Cancer is the result of a series of genetic lesions that include activation of oncogenes and inactivation or loss of tumor suppressor genes. Several groups of investigators have observed that deregulated expression of oncogenes can subvert apoptotic pathways, resulting in prolonged cell survival. In pathological settings such as cancer, members of the Bcl-2 gene family are able to synergize with oncogenes and tumor suppressor genes to transform cells. In this review, we describe the process of apoptosis in mammalian cells and define the role and biochemical pathways through which the Bcl-2 gene family induce and/or protect cells from apoptosis. Last, we will discuss the evidence which suggests that alterations in this pathway may play a central role in tumorigenesis by allowing genetically damaged cells normally destined for elimination to persist, predisposing them to additional mutations and driving them to malignancy.

Analysis of p53-regulated gene expression patterns using oligonucleotide arrays

Oligonucleotide microarrays were employed to quantitate mRNA levels from a large number of genes regulated by the p53 transcription factor. Responses to DNA damage and to zinc-inducible p53 were compared for their transcription patterns in cell culture. A cluster analysis of these data demonstrates that genes induced by γ radiation, UV radiation, and the zinc-induced p53 form distinct sets and subsets with a few genes in common to all these treatments. Cell type- or cell line-specific p53 responses were detected. When p53 proteins were induced with zinc, the kinetics of induction or repression of mRNAs from p53-responsive genes fell into eight distinct classes, five different kinetics of induction, and three different kinetics of repression. In addition, low levels of p53 in a cell induced or repressed only a subset of genes observed at higher p53 levels. The results of this study demonstrate that the nature of the p53 response in diverse mRNA species depends on the levels of p53 protein in a cell, the type of inducing agent or event, and the cell type employed. Of 6000 genes examined for p53 regulatory responses, 107 induced and 54 repressed genes fell into categories of apoptosis and growth arrest, cytoskeletal functions, growth factors and their inhibitors, extracellular matrix, and adhesion genes.

Analysis of p53-regulated gene expression patterns using oligonucleotide arrays

Oligonucleotide microarrays were employed to quantitate mRNA levels from a large number of genes regulated by the p53 transcription factor. Responses to DNA damage and to zinc-inducible p53 were compared for their transcription patterns in cell culture. A cluster analysis of these data demonstrates that genes induced by gamma radiation, UV radiation, and the zinc-induced p53 form distinct sets and subsets with a few genes in common to all these treatments. Cell type- or cell line-specific p53 responses were detected. When p53 proteins were induced with zinc, the kinetics of induction or repression of mRNAs from p53-responsive genes fell into eight distinct classes, five different kinetics of induction, and three different kinetics of repression. In addition, low levels of p53 in a cell induced or repressed only a subset of genes observed at higher p53 levels. The results of this study demonstrate that the nature of the p53 response in diverse mRNA species depends on the levels of p53 protein in a cell, the type of inducing agent or event, and the cell type employed. Of 6000 genes examined for p53 regulatory responses, 107 induced and 54 repressed genes fell into categories of apoptosis and growth arrest, cytoskeletal functions, growth factors and their inhibitors, extracellular matrix, and adhesion genes.

The Incidence of Apoptosis During Colorectal Tumorigenesis

Epithelial homeostasis in colorectal tumorigenesis is dependent not only on the rate of cell production but also on the rate of apoptosis, a genetically programmed process of autonomous cell death. Ideally, an analysis of cell kinetics should be carried out for both cell proliferation and death. We investigated the incidence of apoptosis in 35 colorectal neoplasms (15 adenomas and 20 carcinomas) using the DNA nick end labeling method (TUNEL). The expression of Ki-67 as a marker of proliferating activity and some kinds of oncogene products were analyzed immunohistochemically. When the TUNEL labeling index (TI) and the Ki-67 labeling index (KI) were determined, TI was found to be significantly higher in adenomas with high-grade dysplasia (TI: 2.5%) than in adenomas with low-grade dysplasia (TI: 0.6%) or carcinomas (TI: 1.4%). In contrast, KI increased with the progression of colorectal tumorigenesis. Moreover, TI of the carcinomas was significantly higher in c-Myc-positive cases than in c-Myc-negative cases (p<0.05). The results indicate that apoptosis plays an important role in the early stage of the adenoma-carcinoma sequence, permitting us to speculate that the increased tumor cell proliferation is negated by increased apoptosis at the stage of adenoma with high-grade dysplasia (or intramucosal carcinoma), while cell proliferation overwhelms cell death at the stage of invasive carcinoma. Int J Surg Pathol 8(2):123-132, 2000

Apoptosis of fetal testicular cells is regulated by both p53-dependent and independent mechanisms

A portion of fetal germ cells undergoes apoptosis in the physiological context, but the molecular mechanisms of their apoptosis are largely unknown. Because p53 tumor suppressor gene product promotes apoptosis in various types of cells, we have investigated the expression of p53 in fetal gonads and examined the influence of loss of p53 function in fetal gonad cells using mice deficient in the p53 gene. We found that the expression of p53 protein in fetal testis was induced after 15.5 dpc (days post coitum), while the expression was not detected in fetal ovary. The number of apoptotic cells found in the seminiferous tubules of fetal testes was not significantly different between p53-deficient and wild-type mice until 16.5 dpc. At 17.5 dpc, however, more apoptotic cells were observed in wild-type testes than in the p53-deficient mice. In contrast, a similar number of apoptotic cells was found in fetal ovaries throughout these developmental stages. These observations indicate that p53 promotes apoptosis of fetal testicular cells after 16.5 dpc.

Transfection of antisense p53 tumor suppressor gene oligodeoxynucleotides into rat carotid artery results in abnormal growth of vascular smooth muscle cells

BACKGROUND

Although loss of activity of an antioncogene, the p53 tumor suppressor gene product, has been postulated in the pathogenesis of human restenosis, little is known about the role of p53 in the regulation of vascular smooth muscle cell (VSMC) growth. In this study, to clarify the role of p53 in the pathogenesis of restenosis, we examined transfection of antisense p53 oligodeoxynucleotides (ODN) into VSMC in vitro and rat carotid artery in vivo.

METHODS AND RESULTS

The specificity of antisense p53 ODN was confirmed by a significant decrease in p53 protein. Transfection of antisense p53 ODN into VSMC resulted in a significant increase in DNA synthesis and cell number as compared with sense and scrambled ODN (P<0.01). Importantly, transfection of antisense p53 ODN into rat intact carotid artery resulted in a significant increase in the ratio of neointima to medial area at 2 and 4 weeks after transfection, accompanied by a significant decrease in p53 protein (P<0.01). Moreover, cotransfection of wild-type p53 plasmid completely abolished neointimal formation induced by antisense p53 ODN. The sustained effect of a single antisense ODN administration was confirmed by the kinetics of ODN in the vessel wall with the use of FITC-labeled ODN.

CONCLUSIONS

Overall, the present study demonstrated that loss of p53 by antisense p53 ODN resulted in an abnormal VSMC growth in vitro and in vivo. These results demonstrated the potential contribution of p53 to the pathogenesis of restenosis.

Differential effects of retinoic acid on growth and apoptosis in human colon cancer cell lines associated with the induction of retinoic acid receptor beta

Retinoids are well known as potential chemopreventive and chemotherapeutic agents against a variety of human cancers. Here, we report that retinoic acid (RA) induced differential growth inhibition in human colon cancer cell lines: while DLD-1, HT-29, and WiDr were relatively resistant, HCT-15 and Colo201 were relatively sensitive. All-trans-retinoic acid caused morphological and biochemical changes such as membrane shrinkage, chromatin condensation, and DNA cleavage, which are typical features of cells undergoing apoptosis in sensitive cell lines. Although retinoic acid receptor (RAR)alpha, beta, gamma and retinoid X receptor alpha were expressed in all cell lines examined, a significant induction of RARbeta by all-trans-RA was observed only in sensitive cell lines, suggesting important roles of RARbeta in RA sensitivity. When a vector containing the RARbeta gene was introduced into a relatively resistant cell line, DLD-1, the cells acquired RA sensitivity. Further, we found that the RARbeta transfectants of DLD-1 expressed an enhanced level of c-Myc and Bax proteins, which may result in the increased susceptibility of the cells to all-trans-RA-induced apoptosis. In summary, our data demonstrated that RA induced growth inhibition and apoptosis in human colon cancer cells and that the induction of RAR3 may mediate the retinoid action.

Hydrogen peroxide-induced apoptosis in human hepatoma cells is mediated by CD95(APO-1/Fas) receptor/ligand system and may involve activation of wild-type p53

Reactive oxygen species (ROS) play an important role in cell death induced by many different stimuli. Direct exposure of human hepatoma cell line SMMC-7221 to hydrogen peroxide (H2O2) can induce apoptosis characterized by morphological evidence and fragmentation of DNA assayed by terminal deoxynucleotidyl transferase assay (TUNEL assay). Analysis of flow cytometry indicated that H2O2 can decrease the level of CD95(APO-1/Fas), and it is confirmed that H2O2 can also activate the differential expression of some specific gene such as p53 by means of RT-PCR technique. The results indicated that CD95 signal transduction system may be involved in the H2O2-induced apoptosis, and can regulate some specific genes associated with apoptosis in transcription and translation levels such as p53.

Diverse effects of 9-hydroxyellipticine on the chemosensitivity of human pancreatic cancer cells harboring p53 mutations

Recently, it has been shown that 9-hydroxyellipticine (9-HE), an antitumor alkaloid has a unique property of restoring functional wild-type (wt) p53 activity via inhibition of mutant (mt) p53 protein phosphorylation. In the present study, we investigated the effect of 9-HE on the drug sensitivity of human pancreatic cancer cells. Exposure of cells to 9-HE at a relatively low concentration of 1 microM induced almost no cell death but was sufficient to restore wt p53 activity, as evidenced by an induction of endogenous p21WAF1/CIP1 concomitant with G1 and G2/M arrests in cell-cycle progression. Pretreatment with 1 microM 9-HE markedly enhanced cell killing when combined with cisplatin or mitomycin C. In contrast, 9-HE pretreatment protected cells from killing by 5-fluorouracil, VP-16, or vincristine. These effects of 9-HE were specific for several cell lines containing mt p53 and were not observed in p53-negative or wt p53 expressing cells. Taken together, these findings suggest that 9-HE may exert different effects on the drug sensitivity of pancreatic cancer cells displaying p53 mutations possibly through restoration of wt p53.

Bcl-2 and p53 protein expression, apoptosis, and p53 mutation in human epithelial ovarian cancers

Bcl-2 and p53 gene products have been both linked to cell death by apoptosis. In the present study, we examined the relationship of Bcl-2 and p53 protein expression, p53 mutation and apoptosis in normal human ovaries and different types of human ovarian epithelial tumors by immunohistochemical localization, in situ terminal transferase-mediated dUTP nick end labeling and polymerase chain reaction-single strand conformation polymorphism. It was found that Bcl-2 expressed strongly in the surface epithelium of normal ovaries and benign and borderline ovarian tumors but weakly in the malignant tumors. On the contrary, strong protein expression of p53 was found in 54% (25/46) of the malignant epithelial tumors examined but similar expression of p53 was not observed in borderline and benign tumors and normal ovarian surface epithelium. A significant inverse correlation between Bcl-2 and p53 expression was found in the malignant ovarian tumors examined. p53 gene mutation at exons 5-11 was however not a pre-requisite for p53 expression in both borderline and malignant tumors. Apoptotic activities, as reflected by apoptotic indices, were low in normal ovarian surface epithelium and benign tumors but were increased in borderline and malignant tumors, with the highest average apoptotic index found in grade III malignant tumors. Statistical analyses showed a positive correlation between apoptosis and p53 expression, but similar correlation was not found between apoptosis and Bcl-2 expression. Our results also indicate that although expression of Bcl-2 is important during ovarian carcinogenesis, the Bcl-2 protein may have other roles to play apart from being a modulator of apoptosis in human ovarian epithelial cancers.

p53 mutants have selective dominant-negative effects on apoptosis but not growth arrest in human cancer cell lines

A bidirectional expression vector that allowed equal transcription of cloned wild-type and mutant p53 cDNAs from the same vector was developed. The vector was transfected into CaLu 6 lung carcinoma cells or Saos-2 osteosarcoma cells. All p53 mutants examined were recessive to wild-type p53 transactivation of p21(WAF1/CIP1) but dominant-negative for transactivation of Bax. An examination of effects on growth arrest and apoptotic pathways indicated that all mutants were recessive to wild type for growth arrest but only three of seven mutants were dominant negative for induction of apoptosis.

Implications of p53 protein expression in experimental spinal cord injury

In order to clarify the role of p53, known as a tumor suppressor protein and also as a key molecule of apoptotic cell death, we have studied p53 expression in relation to localization, time course, cell type, and TUNEL reaction in a rat model of transectional spinal cord injury. Other apoptosis related molecules, p21, Bcl-2 and Bax, that are in the cascade of p53 pathway, were also examined. p53 was expressed in cells residing in the vicinity of transection as early as 30 min. For the next 2 days, the positive cells spread in distribution, increased in number, and thereafter decreased. p53 immunoreactivity was localized primarily to the nucleus but not to cytoplasm. Double-staining with glial cell markers revealed that p53 immunoreactivity was often co-localized in microglia, oligodendrocytes and astrocytes, but not in neurons. In view of the results of the double-staining of p53 and Bcl-2, Bax or TUNEL, a variety of apoptosis-related molecules are expressed with p53, all within the first three days of injury. Further, the process of apoptosis via the p53, pathway appears complex even in this simple model of CNS injury. Our study suggests that the manipulation of these apoptosis-related molecules may prove useful in modifying the cell and tissue damage in traumatic CNS injury.

Immunohistochemical detection of p53 tumor-suppressor protein is a poor indicator of prognosis for canine cutaneous mast cell tumors

Eighty-three canine cutaneous mast cell tumors were graded histologically and evaluated immunohistochemically for p53 tumor-suppressor protein expression. An avidin-biotin immunohistochemical protocol incorporated a rabbit polyclonal antibody (CM-1) directed against normal and mutant p53 protein. Positive staining was observed in 44.6% (37/83) of tumors and included 50% (12/24) of grade I (well differentiated) tumors, 46.9% (23/49) of grade II (intermediate differentiation) tumors, and 20% (2/10) of grade III (poorly differentiated) tumors. A statistically significantly higher proportion (P < 0.019) of tumors from the head and neck (83.3%, 10/12), stained positive for p53 than tumors from the thorax, back, abdomen, and axilla (39.4%, 13/33), legs (35.7%, 10/28), or prepuce, scrotal, or inguinal areas (44.4%, 4/9). No statistically significant difference between p53 labeling and histologic grade, breed, or tumor size was present. Survival data were available for 53/83 (63.9%) of dogs. Positive reactivity for p53 was observed in 47% (25/53) of tumors within this group, with 57.9% (11/19) of grade I, 43.3% (13/30) of grade II, and 25% (1/4) of grade III tumors labeled. Mean survival time for the 53 dogs was 12.1 months. The median survival time for dogs with grade III tumors or tumors >5 cm was statistically significantly shorter (P < 0.0001) than for dogs with grades I and II or smaller tumors. Although p53 protein abnormalities may play a role in tumor development or behavior in some canine cutaneous mast cell tumors, immunoreactivity was not associated with lack of tumor differentiation, tumor locations previously shown to demonstrate aggressive biological behavior, breed predisposition, or survival times.

Cyclic AMP inhibited proliferation of human aortic vascular smooth muscle cells, accompanied by induction of p53 and p21

Although cAMP is an important second messenger that plays a pivotal role in the regulation of platelet aggregation and dilatation of blood vessels, little is known about the action of cAMP on the growth of vascular smooth muscle cells (VSMCs). Thus, we initially studied the effects of cAMP accumulation by using various cAMP stimulants, including a phosphodiesterase type 3 inhibitor (cilostazol) on human aortic VSMC growth. Accumulation of cAMP inhibited the platelet-derived growth factor (PDGF)-stimulated VSMC growth in a dose-dependent manner (P<0.01), whereas PDGF significantly stimulated the growth of human VSMCs. Thus, we focused on the role of cell cycle regulatory genes, especially on a negative regulator, an anti-oncogene, p53. The protein of p53 was potentiated by cilostazol as well as forskolin and 8-bromo-cAMP, whereas PDGF decreased p53 expression. Upregulation of p53 protein by cAMP was further confirmed by the observation that the decrease in p21, a p53-inducible protein, by PDGF was significantly attenuated by cilostazol in a dose-dependent manner (P<0.01). These results revealed that accumulation of cAMP inhibited VSMC proliferation, which was at least in part due to an increase in p53-p21 expression. Because p53 and p21 have been reported to induce apoptosis, we examined apoptotic cells for cAMP accumulation. Incubation of VSMCs with cilostazol resulted in a significant increase in apoptotic cells in a dose-dependent manner compared with vehicle treatment as assessed by nuclear chromatic morphology (P<0.01); forskolin also stimulated apoptotic cells. Consistent with nuclear staining, DNA fragmentation in VSMCs treated with forskolin as well as 8-bromo-cAMP and cilostazol was significantly increased compared with DNA fragmentation in VSMCs treated with vehicle, whereas PDGF significantly decreased the rate of DNA fragmentation (P<0.01). Overall, these results demonstrated that cAMP inhibited the proliferation of human aortic VSMCs, accompanied by p53-p21-mediated apoptosis. Analogues of cAMP that have direct inhibitory effects on VSMC proliferation can be considered as potential antiproliferative drugs against VSMC growth.

p53 gene status modulates the chemosensitivity of non-small cell lung cancer cells

This study examined the effects of p53 gene status on DNA damage-induced cell death and chemosensitivity to various chemotherapeutic agents in non-small cell lung cancer (NSCLC) cells. A mutant p53 gene was introduced into cells carrying the wild-type p53 gene and also vice versa to introduce the wild-type p53 gene into cells carrying the mutant p53 gene. Chemosensitivity and DNA damage-induced apoptosis in these cells were then examined. This study included five cell lines, NCI-H1437, NCI-H727, NCI-H441 and NCI-H1299 which carry a mutant p53 gene and NCI-H460 which carries a wild-type p53 gene. Mutant p53-carrying cells were transfected with the wild-type p53 gene, while mutant p53 genes were introduced into NCI-H460 cells. These p53 genes were individually mutated at amino acid residues 143, 175, 248 and 273. The representative cell line NCI-H1437 cells transfected with wild-type p53 gene (H1437/wtp53) showed a dramatic increase in susceptibility to three anticancer agents (7-fold to cisplatin, 21-fold to etoposide, and 20-fold to camptothecin) compared to untransfected or neotransfected H1437 cells. An increase in chemosensitivity was also observed in wild-type p53 transfectants of H727, H441, H1299 cells. The results of chemosensitivity were consistent with the observations on apoptotic cell death. H1437/wtp53 cells, but not H1437 parental cells, exhibited a characteristic feature of apoptotic cell death that generated oligonucleosomal-sized DNA fragments. In contrast, loss of chemosensitivity and lack of p53-mediated DNA degradation in response to anticancer agents were observed in H460 cells transfected with mutant p53. These observations suggest that the increase in chemosensitivity was attributable to wild-type p53 mediation of the process of apoptosis. In addition, our results also suggest that p53 gene status modulates the extent of chemosensitivity and the induction of apoptosis by different anticancer agents in NSCLC cells.

Apoptosis is physiologically restricted to a specialized cytoplasmic compartment in rat spermatids

Cytoplasmic caudal tags of maturing spermatids condense and are detached from the spermatidal cells just before the spermatids are released as spermatozoa. The detached cytoplasmic masses are termed "residual bodies." Features of residual bodies seem to be compatible with those of apoptosis and, just as occurs with apoptotic bodies, residual bodies are phagocytosed by Sertoli cells. Since in vitro studies have demonstrated that nucleus and cytoplasm apoptosis events can be independent phenomena, we reasoned that apoptosis pathways might be restricted to the caudal tag of the maturing spermatids in order to originate residual bodies. Consistent with this idea, here we showed that annexin V specifically bound the membranes of isolated residual bodies and that expression levels of caspase-1, c-jun, p53, and p21 were specifically increased in these cytoplasmic compartments. Electron microscopy of cytoplasmic lobes and residual bodies confirmed that their ultrastructural features were those of apoptosis. These data indicate that the mechanism responsible for the formation of residual bodies is similar to that for apoptotic bodies; and the study presents evidence, for the first time, that apoptotic signaling molecules can be restricted to a cytoplasmic compartment and proceed in the presence of a healthy nucleus.

Adenovirus-mediated p53 growth inhibition of ovarian cancer cells is independent of endogenous p53 status

OBJECTIVE

The aim of this study was to determine the effect of transfection of adenovirus-mediated wild-type p53 into ovarian cancer cells with both wild-type and mutant endogenous p53.

STUDY DESIGN

Eight human ovarian cancer cell lines were used: three with p53 mutations, one that is p53 null, and four with wild-type p53. The recombinant p53 adenovirus (Adp53) contains the cytomegalovirus promoter, wild-type p53 cDNA, and SV40 polyadenylation signal in a minigene cassette inserted into the E1-deleted region of modified Ad5. The transduction efficiency of cells was assessed using a beta-gal-containing adenovirus. Cell-counting assays were used to evaluate the effect of transfection with Adp53 on the growth of cells. P53 expression was evaluated using Western blot. Cell cycle analysis and apoptosis studies were done using a tunnel-based assay and fluorescent activated cell sorting.

RESULTS

Transduction efficiencies varied between cell lines. More than 90% growth inhibition occurred in seven of eight cell lines after infection with adenovirus-mediated p53 if a viral dose leading to at least 50% of cells infected was used. Regardless of endogenous p53 status, apoptosis occurred in cells infected with p53.

CONCLUSIONS

Ovarian cancer cells are growth inhibited by transfection with adenovirus-mediated p53 regardless of their endogenous p53 status. Growth inhibition is related to transduction efficiency.

Expression of apoptosis and its related protein in astrocytic tumors

The relationship between malignant potential and apoptosis in astrocytic tumors has not been clearly defined, and further classification of astrocytic tumors is necessary. To elucidate the relationship between the histopathological grade of astrocytic tumors and apoptosis, we studied 25 cases of astrocytic tumors, comprising 10 cases of glioblastoma (GB), 7 cases of anaplastic astrocytoma (AA), and 8 cases of astrocytoma (AC). We detected apoptosis using the TdT-mediated dUTP-biotin nick-end labeling (TUNEL) method. We studied immunohistochemical expression of bcl-2 protein and p53 protein, which are apoptosis-related factors, and cell proliferative activity using Ki-67 antibody. No significant change was noted between apoptotic index and the histological grade of the tumors. In GB, apoptotic cell-rich foci were present at the pseudopalisading necrosis. No correlation between histopathological grades and expression of either p53 or bcl-2 was observed. In GB, however, poor distribution of bcl-2 was found in the areas of pseudopalisade formation. bcl-2 is one of the regulatory factors in the cell cycle and inhibits apoptosis. Expression of apoptosis had no correlation with histopathological grade. However, in GB, the distribution of apoptotic cells showed a correlation with bcl-2-poor foci. It was thought that apoptosis was one of the regulatory factors in the formation of pseudopalisading necrosis in GB.

IFN-tau exhibits potent suppression of human papillomavirus E6/E7 oncoprotein expression

The effects of interferon-tau (IFN-tau) on tumor suppressor factors and virus oncoprotein expression were compared with two other type I IFN in human papillomavirus (HPV-16)-transformed cells. Nontumorigenic human keratinocytes, HuKc/HPV-16d-2C (d-2C), treated with recombinant human IFN-alpha2a (Roferon), a human recombinant alpha IFN hybrid, alpha B/D (IFN-alphaB/D), or ovine IFN-tau were evaluated for their effects on the levels of E6 and E7 expression. IFN-tau was comparable to IFN-alpha2a in decreasing intracellular levels of E6 and E7, and IFN-alphaB/D was more effective than IFN-a2a in suppressing E7 levels. All three IFN were capable of increasing the cellular concentration of wild-type p53 tumor suppressor with the magnitude IFN-tau > IFN-alpha2a > IFN-alphaB/D. Increases in p53 concentrations correlated with the observed decreases in E6 mRNA and protein levels. The antiviral effects observed in this study reveal that IFN-tau has potent antipapillomavirus activity. Sequences/structures unique to IFN-tau could allow for alternative IFN/receptor interactions and may explain the differences in biologic function.

Pharmaceutical perspectives of nonviral gene therapy

The use of nonviral plasmid-based gene medicines represents an attractive in vivo gene transfer strategy that is simple and lacks many risks that are inherent to viral systems. Commercialization of gene medicines requires a thorough analysis of business opportunities, unmet clinical needs, competitive products under development, and issues related to intellectual property. Synthetic gene delivery systems are designed to control the location of a gene within the body by affecting distribution and access of a gene expression system to the target cell, and/or recognition by a cell surface receptor and uptake followed by intracellular and nuclear translocation. Plasmid-based gene expression systems are designed to control the level, fidelity, and duration of in vivo production of a therapeutic gene product. This review will provide insights into the potentials of plasmid-based gene therapy and critical evaluation of gene delivery sciences and clinical applications of gene medicines.

The role of autosomal cell apoptosis regulator genes in human spermatogenesis

Immunohistochemical analysis of the expression of the autosomal apoptosis regulator genes, BAX, bcl-2, p53, and cyclic-AMP responsive element modulator (CREM) in testis biopsies from infertile men demonstrated that BAX, bcl-2, and p53 immunoreactivity was absent irrespective of seminiferous tubule histology. In contrast, cell-specific CREM immunoreactivity in round spermatids, with complete absence of CREM in patient biopsies showing spermatocyte maturation arrest and Sertoli cell only, was evident, suggesting a possible role of autosomal genes in the regulation of apoptosis in human spermatogenesis regulation.

Nucleotide sequence of the porcine p53 cDNA, and the detection of recombinant porcine p53 expressed in vitro with a variety of anti-p53 antibodies

The cDNA of porcine p53 was cloned and sequenced by a reverse transcriptase polymerase chain reaction (RT - PCR) approach with primers based on regions of homology between all known p53 sequences. The p53 cDNA was found to be 87% conserved to human p53 and 86% conserved to bovine p53 at the nucleotide level. The porcine p53 sequence was inserted into an expression vector and recombinant protein expressed in vitro. An approximately 50 kDa protein was detected by Western blotting using both polyclonal and monoclonal anti-p53 antibodies. The sequence data of porcine p53 and the ability to detect expressed protein with various anti-p53 antibodies will allow the p53 status of the pig population, and the role of p53 in porcine tumours, to be assessed. An understanding of tumour development in the pig may be important if pig cells, tissues or organs are to be used in the treatment of humans.

Altered growth response of oral mucosal keratinocytes in p53-deficient mice

P53 has important regulatory functions in cell growth, differentiation and apoptosis. Here we analyzed the effects of p53 on the growth response of oral mucosal keratinocytes (OMKCs) using p53-deficient (p53-/-) mice. No morphological difference was found between p53-/- and wild-type (p53+/+) oral mucosa. In a long-term culture, p53-/- OMKCs continued to proliferate past the point at which p53+/+ became senescent. The percentage of p53-/- OMKCs in the G0/G1 phase was lower than that of p53+/+ OMKCs. Proliferation of cultured OMKCs induced by epidermal growth factor (EGF) and interleukin-(IL)-1alpha was more strongly enhanced in p53-/- than in p53+/+ mice. Such an enhanced response was not due to increased mRNA expression of growth factor receptors. These data suggest that p53 acts as a modulator of G1 arrest in OMKCs and is also involved in the regulation of responses to EGF and IL-1alpha without affecting the expression of their receptors.

Change in oligomerization specificity of the p53 tetramerization domain by hydrophobic amino acid substitutions

The tumor suppressor function of the wild-type p53 protein is transdominantly inhibited by tumor-derived mutant p53 proteins. Such transdominant inhibition limits the prospects for gene therapy approaches that aim to introduce wild-type p53 into cancer cells. The molecular mechanism for transdominant inhibition involves sequestration of wild-type p53 subunits into inactive wild-type/mutant hetero-tetramers. Thus, p53 proteins, whose oligomerization specificity is altered so they cannot interact with tumor-derived mutant p53, would escape transdominant inhibition. Aided by the known three-dimensional structure of the p53 tetramerization domain and by trial and error we designed a novel domain with seven amino acid substitutions in the hydrophobic core. A full-length p53 protein bearing this novel domain formed homo-tetramers and had tumor suppressor function, but did not hetero-oligomerize with tumor-derived mutant p53 and resisted transdominant inhibition. Thus, hydrophobic core residues influence the oligomerization specificity of the p53 tetramerization domain.

Biochemical uncovering of mdm2/p53 complexes in liposarcomas parallels their immunohistochemical detection

Recent observations indicate the existence of pathogenetically distinct groups of well-differentiated (WD) dedifferentiated (DD) liposarcomas. In the retroperitoneal WD-DD liposarcomas, the predominant phenotype is represented by the aberrant (overexpressed) mdm2+/p53+ wild-type profile. At the nonretroperitoneal site, the WD liposarcomas present a wider association of MDM2/P53 gene expression; i.e., mdm2+/p53+, mdm2+/p53-, mdm2-/p53+ and mdm2-/p53-, and TP53 mutations seem to correlate with the dedifferentiation process. A biochemical study of mdm2-p53 association in 11 tumor samples characterized by the presence of different mdm2 and p53 immunophenotypes was performed. Immunoprecipitation assays using a p53-specific antibody were performed on tumor tissue and surrounding normal tissue; the immunoprecipitated material was then investigated for the presence of p53 (control) and of coimmunoprecipitated mdm2. This biochemical analysis showed that, in mdm2+/p53+/wild-type retroperitoneal liposarcomas, a band corresponded to mdm2 protein in the cellular lysates immunoprecipitated with a p53-directed antibody. In contrast, the mdm2+/p53- liposarcoma did not evidence the presence of mdm2 protein nor was p53 protein available to direct immunoprecipitation, as in the p53 mutant tumor samples with mdm2-/p53+ and mdm2-/p53- phenotypes. From the normal counterpart of retroperitoneal liposarcoma lysates, no p53 protein was immunoprecipitated. The findings in this study agree with the molecular data and they show the physical association of mdm2 and p53 in fresh liposarcoma surgical specimens.

Infrequent p53 gene alterations in ulcerative colitis

The purpose of this study was to determine whether point mutations and loss of the p53 gene take place in ulcerative colitis which is histologically negative for dysplasia. DNA was extracted from 13 frozen rectal or colon biopsies and blood samples. Ulcerative colitis was classified histologically as active (10 cases) and inactive (3 cases). Exons 5-8 were amplified by PCR, treated with exonuclease and shrimp alkaline phosphatase and sequenced by the dideoxy chain termination method with the Sequenase Version 2.0 DNA sequencing kit. PCR products of intron 6 and exon 4 were digested with MspI and AccII, respectively, for RFLP analysis. No p53 gene mutation was detected in these cases. The number of informative patients for loss of heterozygosity (LOH) at the p53 intron 6 was high, 11 out of 12 (92%), whereas no LOH was observed. LOH affecting p53 exon 4 was not detected in lesions from 5 of 12 patients (42%). In ulcerative colitis, tumor progression is similar to that in sporadic colon cancer, and other oncogenes and tumor suppressor genes are likely to be mutated before the p53 gene.

Isolation of differentially expressed cDNAs from p53-dependent apoptotic cells: activation of the human homologue of the Drosophila peroxidasin gene

Inactivation of the p53 tumor suppressor protein has been observed in a large number of human cancers. Overexpression of p53 induces either growth arrest or programmed cell death (apoptosis). The growth arrest function of p53 is mediated by induction of p21 (WAF1/CIP1), but the mechanisms underlying p53-dependent apoptosis are still largely unknown. To investigate these mechanisms, we have identified six differentially expressed transcripts in a human colon cancer cell line undergoing p53-dependent apoptosis. One of the p53-responsive genes showed significant homology to Drosophila peroxidasin, an extracellular matrix-associated peroxidase, and is likely to be its human homologue. Our results suggest a possible connection between p53-dependent apoptosis and the production of reactive oxygen species.

A phase I/II study of hepatic artery infusion with wtp53-CMV-Ad in metastatic malignant liver tumours

Colorectal cancer (CRC) is the second commonest cause of cancer death in the UK, with greater than 40% of these patients destined to die of the disease despite current medical management. Death is commonly due to liver metastases with sequelae including progressive liver dysfunction. Most patients with liver metastases present with tumours that are unresectable and incurable with existing therapies. The median survival for CRC patients after diagnosis with liver metastases is approximately 6 months or less. The human p53 gene is a tumour suppressor gene involved in the control of cell proliferation. Loss of wild-type p53 function is associated with the uncontrolled growth of many types of human cancers. The reintroduction and expression of wild-type p53 into p53 altered tumour cells has been shown to suppress tumour growth or induce apoptosis in both in vitro and in vivo models. In our experience greater than 50% of CRC tumours have p53 alterations. This study seeks to evaluate the safety, biological efficacy and the effectiveness of wtp53-CMV-Ad treatment which is a recombinant adenoviral vector containing the wild-type human p53 gene. It will be administered by infusion via the hepatic artery, for the regional gene therapy of malignant liver tumours. Study patients will have incurable metastatic (CRC) malignant tumours of the liver with evidence of p53 alteration in their liver tumours. In vitro studies have demonstrated p53-specific antiproliferative effects of wtp53-CMV-Ad on human liver tumour cells and in vivo studies have demonstrated p53-specific antiproliferative effects on human liver tumour cells. The vector Ad-p53 is a recombinant, replication-defective adenovirus based on adenovirus serotype 5. It contains a sequence encoding wild-type p53 whose expression is under the control of the human cytomegalovirus immediate early promoter-enhancer. This construct will be growth in 293 cells which contain the adenoviral E1A and E1B coding sequences which have been removed from the vector to render it replication defective. The study design is an open-label, non-randomised, single-dose, dose escalation Phase I/II clinical trial anticipated to involve a maximum of 19 patients. wtp53-CMV-Ad will be administered by infusion in a reservoir connected to the hepatic artery, for regional gene therapy (surgically implanted pump) in 3 escalating doses to successive cohorts of 3 patients each until the maximum tolerated dose is determined. Subsequently, 10 patients will be treated with this dose. Regional wtp53-CMV-Ad therapy will be administered as a single bolus infusion via hepatic artery catheter. The route of administration of wtp53-CMV-Ad via hepatic artery infusion is designed to maximise gene therapy exposure to the malignant tumours while minimising exposure to normal tissues outside the liver. The clinical protocol is designed to monitor treatment toxicity. Another objective is to evaluate the biological efficacy, including efficiency and stability of gene transfer by analysis of tumour tissues following therapy. As an important part of this objective the pharmacokinetics of wtp53-CMV-Ad will be studied. Clinical evidence of anti-tumour efficacy will also be collected. In addition, the safety and efficacy of different doses levels of wtp53-CMV-Ad will be studied.

Apoptosis in breast cancer and its relationship to clinicopathological characteristics and prognosis

BACKGROUND AND OBJECTIVES

Apoptosis is essential to maintain homeostasis in living organisms and occurs in a variety of tissues in response to both physiological and pathological stimuli. In breast cancer, most cytotoxic drugs and hormonal treatments induce apoptosis. We studied the relationships between apoptosis and clinicopathological variables or prognosis in 143 patients with operable breast cancer.

METHODS

Apoptosis was numerically graded in 5 consecutive 40x high-power fields (HPF) of hematoxylin-eosin (H&E) stained sections, since we showed that there was a significant correlation of H&E staining with terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labeling (TUNEL) staining.

RESULTS

The average number of apoptotic cells was 19.9 (0 approximately 168)/5 HPF, and cases were classified into 3 groups based on the number of apoptotic cells/5HPF: 0 to 10, 11 to 30, and 31+. The level of apoptosis increased with increasing size of the tumor, and apoptosis was rarely seen in tumors with positive ER or lower proliferative activity, as assessed by DNA polymerase alpha. As shown by DNA content analysis, apoptotic cells were observed more frequently in tumors with low G1 and high S-phase fractions. In addition, apoptosis was correlated with overexpression of p53 and poor prognosis. Although apoptosis did not correlate with EIC (extensive intraductal component) status, tumors with comedo component had higher values of apoptosis than those without comedo component.

CONCLUSIONS

In breast cancer, apoptosis might reflect biological behavior, namely a higher degree of biological aggressiveness and unfavorable prognosis.

p53 compound heterozygosity in a severely affected child with Li-Fraumeni syndrome

The Li-Fraumeni Syndrome (LFS) is a rare, dominantly inherited syndrome that features high risk of cancers in childhood and early adulthood. Affected families tend to develop bone and soft tissue sarcomas, breast cancers, brain tumors, leukemias, and adrenocortical carcinomas. In some kindreds, the genetic abnormality associated with this cancer phenotype is a heterozygous germline mutation in the p53 tumor suppressor gene. Recently, we identified one patient who presented in early childhood with multiple primary cancers and who harbored three germline p53 alterations (R156H and R267Q on the maternal allele and R290H on the paternal allele). To classify the biologic effects of these alterations, functional properties of each of the p53 mutants were examined using in vitro assays of cellular growth suppression and transcriptional activation. Each amino acid substitution conferred partial or complete loss of wild-type p53 function, but the child completed normal embryonic development. This observation has not been previously reported in a human, but is consistent with observations of normal embryogenesis in p53-deficient mice.

Prognostic significance of bcl-2 expression in leiomyosarcoma of the uterus

We examined bcl-2 expression as well as p53 expression and mutation in human uterine smooth muscle tumours to determine the influence of bcl-2 expression on prognosis in patients with uterine leiomyosarcomas. bcl-2 protein was expressed in nearly all benign smooth muscle tumours but in only 57% of leiomyosarcomas. Benign smooth muscle tumours were usually negative for p53 protein, but 16 out of 21 (76%) leiomyosarcomas were positive. A p53 gene mutation was detected in nine of the 16 leiomyosarcomas that showed p53-positive staining. A significant positive correlation was observed between p53 mutation and p53 expression, between the number of mitoses and the Ki-67 labelling index, and between clinical stage and p53 mutation. A significant negative correlation was observed between bcl-2 expression and p53 mutation, and between bcl-2 expression and p53 overexpression. Univariate survival analysis revealed that bcl-2 expression, p53 mutation and clinical stage (stage 1 vs stages 2-4) all showed a significant correlation with prognosis. In a multivariate stepwise regression analysis, positive bcl-2 expression and stage 1 disease were the independent predictors of a favourable prognosis. Our results suggest that bcl-2 is frequently expressed in human uterine smooth muscle tumours, and that its expression may correlate with a favourable prognosis in patients with uterine leiomyosarcoma.

Regulators of apoptosis in human breast cancer

OBJECTIVES

Apoptosis or programmed cell death represents a mechanism by which tumor cells with DNA damage can be deleted. Bcl-2 and p53 gene products have been both linked to apoptosis. Bcl-2 plays a role as an inhibitor of apoptosis that may extend the viability of cells containing genetic alterations and facilitate tumor progression. Mutant p53 has a similar effect. The purpose of this study was to investigate expression of bcl-2 in 70 malignant and 30 benign breast lesions using different methods (enzyme immunoassay, immunodot blot, Western blot) and to compare it with the established clinicopathological prognostic factors (age, tumor size, type, grade, lymph node status) and some molecular genetic markers in breast cancer.

RESULTS

bcl-2 and mutant p53 were highly expressed in breast cancer than benign breast lesions and aneuploidy was more frequently detected in malignant breast samples. No correlation could be observed between bcl-2 expression and node status, tumor size, differentiation, type, age at excision or mutant p53 expression. However, a strong positive associations were seen between bcl-2 and estrogen receptors (ER), DNA aneuploidy. Eighty-five percent of bcl-2 positive tumors were ER positive and 65% were aneuploid, while in bcl-2 negative tumors only 28% were ER positive and 37% were aneuploid.

CONCLUSIONS

The association seen between bcl-2 and ER raises the possibility that bcl-2 is an ER-regulated gene which suggests a potential important role for bcl-2 as a modulator of response to hormonal therapy in breast cancer. Monitoring hormonal therapy can easily be done by bcl-2 quantitative EIA method.

Physical interaction and functional antagonism between the RNA polymerase II elongation factor ELL and p53

ELL was originally identified as a gene that undergoes translocation with the trithorax-like MLL gene in acute myeloid leukemia. Recent studies have shown that the gene product, ELL, functions as an RNA polymerase II elongation factor that increases the rate of transcription by RNA polymerase II by suppressing transient pausing. Using yeast two-hybrid screening with ELL as bait, we isolated the p53 tumor suppressor protein as a specific interactor of ELL. The interaction involves respectively the transcription elongation activation domain of ELL and the C-terminal tail of p53. Through this interaction, ELL inhibits both sequence-specific transactivation and sequence-independent transrepression by p53. Thus, ELL acts as a negative regulator of p53 in transcription. Conversely, p53 inhibits the transcription elongation activity of ELL, suggesting that p53 is capable of regulating general transcription by RNA polymerase II through controlling the ELL activity. Elevated levels of ELL in cells resulted in the inhibition of p53-dependent induction of endogenous p21 and substantially protected cells from p53-mediated apoptosis that is induced by genotoxic stress. Our observations indicate the existence of a mutually inhibitory interaction between p53 and a general transcription elongation factor ELL and raise the possibility that an aberrant interaction between p53 and ELL may play a role in the genesis of leukemias carrying MLL-ELL gene translocations.

Broad patterns of gene expression revealed by clustering analysis of tumor and normal colon tissues probed by oligonucleotide arrays

Oligonucleotide arrays can provide a broad picture of the state of the cell, by monitoring the expression level of thousands of genes at the same time. It is of interest to develop techniques for extracting useful information from the resulting data sets. Here we report the application of a two-way clustering method for analyzing a data set consisting of the expression patterns of different cell types. Gene expression in 40 tumor and 22 normal colon tissue samples was analyzed with an Affymetrix oligonucleotide array complementary to more than 6,500 human genes. An efficient two-way clustering algorithm was applied to both the genes and the tissues, revealing broad coherent patterns that suggest a high degree of organization underlying gene expression in these tissues. Coregulated families of genes clustered together, as demonstrated for the ribosomal proteins. Clustering also separated cancerous from noncancerous tissue and cell lines from in vivo tissues on the basis of subtle distributed patterns of genes even when expression of individual genes varied only slightly between the tissues. Two-way clustering thus may be of use both in classifying genes into functional groups and in classifying tissues based on gene expression.

1,25-Dihydroxyvitamin D3, recombinant human transforming growth factor-beta 1, and recombinant human bone morphogenetic protein-2 induce in vitro differentiation of canine osteosarcoma cells

Effects of 1,25-dihydroxyvitamin D3 (1,25(OH)2D3), recombinant human transforming growth factor (rhTGF)-beta 1 and recombinant human bone morphogenetic protein (rhBMP)-2 on differentiation in four different canine osteosarcoma cell lines (POS53B, 53C, 53D and 14A) were examined using markers specifically expressed by phenotypic osteoblasts. 1,25(OH)2D3 increased alkaline phosphatase (ALP) activity in one cell line, osteocalcin production in two lines and type I collagen production in three lines. RhTGF-beta 1 increased ALP activity in one clonal cell, osteocalcin production in one clonal cell and type I collagen production in two clonal cells. RhBMP-2 increased ALP activity in all clonal cells, osteocalcin production in two clonal cells and type I collagen production in three clonal cells. Thus, these agents induced differentiation in osteosarcoma cells at different efficacies. Electron microscopic study revealed that these agents increased cellular activity in all cell lines with no evidence of degeneration of cell organelle by drug cytotoxicity. In some cultures treated with either 1,25(OH)2D3 or rhBMP-2, apoptotic cells were observed. Based on the change in markers, rhBMP-2 and 1,25(OH)2D3 seemed to be more effective than rhTGF-beta 1. These agents are potential inducers of apoptosis.

Low rate of apoptosis and overexpression of bcl-2 in Epstein-Barr virus-associated gastric carcinoma

AIMS

Epstein-Barr virus (EBV) has been demonstrated in about 10% of gastric carcinomas. However, the pathogenetic role of EBV in gastric carcinoma is uncertain. We compared the rate of apoptotic cell death, cell proliferation and the expression of apoptosis-related proteins in gastric carcinomas with or without EBV.

METHODS AND RESULTS

Epstein-Barr virus was detected in 40 gastric carcinomas by EBV-encoded small RNA-1 in-situ hybridization. Apoptotic cell death, MIB-1, p53, bcl-2 and bcl-x were examined by the terminal deoxynucleotidyl-mediated dUTP-nick end labelling method and immunohistochemistry. We also included 40 age-, sex- and disease stage-matched EBV-negative cases as a control. The number of apoptotic cells was significantly lower in EBV-positive (20 +/- 15. 1/1000 cells) and bcl-2-positive (17 +/- 12.9/1000 cells) tumours than in EBV-negative (43 +/- 37.1) and bcl-2-negative tumours (38 +/- 32.1, P < 0.001, P < 0.001, respectively). bcl-2 immunostaining was significantly higher in EBV-positive tumours (24 cases) than in EBV-negative tumours (12 cases, P < 0.05). There was no significant difference in bcl-x and p53 expression between EBV-positive and -negative tumours. The number of MIB-1-positive cells in EBV-positive tumours (237 +/- 161/1000) was significantly lower than in EBV-negative tumours (480 +/- 208/1000 cells, P < 0.001).

CONCLUSIONS

A low rate of apoptosis and high bcl-2 expression were recognized in EBV-positive gastric carcinomas, suggesting that bcl-2 protein is the main inhibitor of apoptosis in EBV-positive carcinomas. In addition, the low apoptotic and proliferative activities may reflect a low biological activity in EBV-positive gastric carcinomas.

Growth dysregulation and p53 accumulation in human primary colorectal cancer

p53 accumulation is common in colorectal cancer, but effects on growth homeostasis are unclear. In this study, DNA content, cell cycle phase fractions and DNA strand-breaks consistent with apoptosis were assessed by flow cytometry in 42 fresh primary colorectal tumours and matched normal mucosa. p53 accumulation was assessed in 37 fixed tumour sections, by immunohistochemistry. In normal mucosa, 10.3 +/- 6.6% (mean +/- s.d.) cells were in DNA synthesis phase while 28.7 +/- 17.9% showed apoptosis. A relationship suggestive of growth homeostasis, was observed between these parameters (r = 0.8; P < 0.05). In cancers, a greater number of cells were in DNA synthesis phase (15.6 +/- 12.9% tumour vs mucosa 10.3 +/- 6.6%; P < 0.02) while fewer showed apoptosis than normal mucosa (18.5 +/- 17.0% tumour vs mucosa 28.7 +/- 17.9%; P < 0.01). DNA synthesis and apoptosis fractions were unrelated in cancers, suggesting growth dysequilibrium. p53 accumulation was detected in 59% (22/37) tumours and was associated with reduced apoptosis compared to p53-negative tumours or mucosa (14.8 +/- 15% p53 accumulation vs 26.3 +/- 18% p53-negative; P < 0.05; vs 28.7 +/- 17.9% mucosa; P < 0.05). p53 accumulation was unrelated to DNA synthesis phase fractions. p53 accumulation is accompanied by reduced apoptosis which may accentuate growth dysequilibrium in colorectal cancer.

Increase of BCNU sensitivity by wt-p53 gene therapy in glioblastoma lines depends on the administration schedule

In this article, we investigated the effect induced by the reintroduction of wild-type p53 (wt-p53) protein on BCNU sensitivity in the ADF glioblastoma line. Using a wt-p53 recombinant adenovirus (Ad-p53), we demonstrated that exogenous wt-p53 expression was able to increase the sensitivity to BCNU in ADF cells. Interestingly, this effect was more evident when Ad-p53 infection was performed after BCNU treatment compared with the opposite sequence. To understand the biological basis of these different behaviors, we analyzed the cell cycle of the differently treated cells. We found that Ad-p53 infection induced a persistent accumulation of cells in the G0/G1 phase while, as expected, BCNU induced a block in the G2-M phase. Ad-p53-->BCNU sequence did not significantly modify the cell cycle profile in respect of Ad-p53 infected cells. In contrast, BCNU-->Ad-p53 sequence provoked G2-M arrest similar to that observed after treatment with BCNU alone, but prevented the later recovery of the cells through the cell cycle, by driving the cells to apoptotic death. These results demonstrate that the administration sequence is important to increase drug sensitivity. To generalize the phenomenon observed on ADF line, the antiproliferative effect of the two different schedules was analyzed on other glioblastoma lines (A172, CRS-A2, U373MG) with different BCNU sensitivity and p53 status. The data obtained confirm that the wt-p53 gene transfer enhances BCNU sensitivity in glioblastoma cells depending on the administration sequence.

Activation of caspases and p53 by bovine herpesvirus 1 infection results in programmed cell death and efficient virus release

Programmed cell death (PCD), or apoptosis, is initiated in response to various stimuli, including virus infection. Bovine herpesvirus 1 (BHV-1) induces PCD in peripheral blood mononuclear cells at the G0/G1 phase of the cell cycle (E. Hanon, S. Hoornaert, F. Dequiedt, A. Vanderplasschen, J. Lyaku, L. Willems, and P.-P. Pastoret, Virology 232:351-358, 1997). However, penetration of virus particles is not required for PCD (E. Hanon, G. Meyer, A. Vanderplasschen, C. Dessy-Doize, E. Thiry, and P. P. Pastoret, J. Virol. 72:7638-7641, 1998). The mechanism by which BHV-1 induces PCD in peripheral blood mononuclear cells is not understood, nor is it clear whether nonlymphoid cells undergo PCD following infection. This study demonstrates that infection of bovine kidney (MDBK) cells with BHV-1 leads to PCD, as judged by terminal deoxynucleotidyltransferase-mediated dUTP-biotin nick end labeling, DNA laddering, and chromatin condensation. p53 appears to be important in this process, because p53 levels and promoter activity increased after infection. Expression of proteins that are stimulated by p53 (p21(Waf1) and Bax) is also activated after infection. Cleavage of Bcl-xL, a protein that inhibits PCD, occurred after infection, suggesting that caspases (interleukin-1beta-converting enzyme-like proteases) were activated. Other caspase substrates [poly(ADP-ribose) polymerase and actin] are also cleaved during the late stages of infection. Inhibition of caspase activity delayed cytotoxic activity and virus release but increased the overall virus yield. Taken together, these results indicate that nonlymphoid cells undergo PCD near the end of productive infection and further suggest that caspases enhance virus release.

The level of DNA modification by (+)-syn-(11S,12R,13S,14R)- and (-)-anti-(11R,12S,13S,14R)-dihydrodiol epoxides of dibenzo[a,l]pyrene determined the effect on the proteins p53 and p21WAF1 in the human mammary carcinoma cell line MCF-7

The polycyclic aromatic hydrocarbon (PAH) dibenzo[a,l]pyrene (DB[a,l]P), the most carcinogenic PAH tested in rodent bioassays, exerts its pathobiological activity via metabolic formation of electrophilically reactive DNA-binding fjord region (+)-syn-(11S,12R,13S,14R)- or (-)-anti-(11R,12S,13S,14R)-DB[a,l]P-dihydrodiol epoxides (DB[a,l]-PDEs). DB[a,l]P is metabolized to these DB[a,l]PDEs which bind to DNA in human mammary carcinoma MCF-7 cells. The molecular response of MCF-7 cells to DNA damage caused by DB[a,l]PDEs was investigated by analyzing effects on the expression of the tumor suppressor protein p53 and one of its target gene products, the cyclin-dependent kinase inhibitor p21WAF1. Treatment of MCF-7 cells with (+)-syn- and (-)-anti-DB[a,l]PDE at a concentration range of 0.001-0.1 microM resulted in DB[a,l]PDE-DNA adduct levels between 2 and 30, and 3 and 80 pmol/mg DNA, respectively, 8 h after exposure. (-)-anti-DB[a,l]PDE exhibited a higher binding efficiency that correlated with a significantly stronger p53 response at low concentrations of the dihydrodiol epoxides. The level of p53 increased by 6-8 h after treatment. The p21WAF1 protein amount exceeded control levels by 12 h and remained elevated for 96 h. At a dose of 0.01 microM (+)-syn-DB[a,l]PDE, an increase in p21WAF1 was observed in the absence of a detectable change in p53 levels. The results indicate that the increase in p53 induced by DB[a,l]PDEs in MCF-7 cells requires an adduct level of approximately 15 pmot/mg DNA and suggest that the level of adducts rather than the specific structure of the DB[a,l]PDE-DNA adduct formed triggers the p53 response. The PAH-DNA adduct level formed may determine whether p53 and p21VAF1 pathways respond, resulting in cell-cycle arrest, or fail to respond and increase the risk of mutation induction by these DNA lesions.

Increased sensitivity of human colon cancer cells to DNA cross-linking agents after GRP78 up-regulation

We have shown earlier that pre-treatment of V79 Chinese hamster cells with 6-aminonicotinamide (6-AN) or 2-deoxyglucose (2-dG) results in over-expression of the Mr 78,000 glucose-regulated stress protein (GRP78) and the subsequent development of resistance to inhibitors of topoisomerase II. These phenomena also occur in V79-derived cell lines that are deficient in poly(ADP-ribose) (p(ADPR)) metabolism. In contrast, over-expression of GRP78 under the conditions outlined above is found to be associated with hypersensitivity to several clinically-relevant DNA cross-linking agents, namely, 1,3-bis (2-chloroethyl)-1-nitrosourea (BCNU), cisplatin, and melphalan. We have also previously shown that pre-treatment with 6-AN, an inhibitor of p(ADPR) metabolism, causes an increase in the life span in BCNU-treated mice bearing L1210 tumors. These observations prompted us to examine whether 6-AN pre-treatment can result in the over-expression of GRP78 in human colon cancer cell lines and, if so, whether this increase is associated with sensitization to DNA cross-linking agents outlined above. Following treatment of three colon cancer cell lines, HCT116, SW480, and VACO-8, for 48 h with 0.1 mM 6-AN, cytosolic GRP78 levels were elevated approximately 4.2 times, 8 times, and 2.5 times for each cell line respectively, as measured by Western immunoblotting. To determine sensitivity after GRP78 up-regulation, the cells were washed and grown for 412 h in growth medium devoid of 6-AN, before being treated with DNA cross-linking agents. The 412 h time period allowed p(ADPR) metabolism to return to normal while GRP78 levels remained elevated, thus allowing us to associate GRP78 over-expression with sensitivity to those agents. After treating cells for 1 h with BCNU, cisplatin, or melphalan, cell sensitivity was determined by clonogenic survival assay or a fluorescence-based cytotoxicity assay. Based on changes in IC50 values, 6-AN caused an increase in sensitivity for HCT116, SW480, and VACO-8 cells of 1.5, 2.3, and 1.0 times, respectively, for BCNU, 4.8, 3.8, and 2.6 for cisplatin, and 6.4, 3.7, and 2.2 times for melphalan. Thus, our results show that over-expression of GRP78 in human tumor cell lines is associated with increased sensitivity to clinically useful chemotherapy agents. This sensitization occurred in three different tumor cell lines, each bearing a separate genetic defect associated with altered sensitivity.

Gene therapy in veterinary medicine

Gene therapy in simple terms is the introduction of a gene into a cell, in vivo, in order to ameliorate a disease process. Human clinical trials have focused on the correction of monogenic deficiency diseases, cancer and AIDS. This paper summarises the technology of gene therapy, gives a brief synopsis of the current applications of gene therapy to veterinary medicine and discusses some of the problems which need to be overcome so that gene therapy can become accepted clinical practice.

TP53 alterations in relation to the cell cycle-associated proteins p21, cyclin D1, CDK4, RB, MDM2, and EGFR in cancers of the uterine corpus

In the present study, TP53 alterations have been analysed and compared with the expression of the proteins p21, cyclin D1, cdk4, RB, EGFR, and MDM2 in 53 cancers of the uterine corpus. TP53 gene mutations analysed by CDGE/DGGE and direct sequencing showed a TP53 gene mutation in 18 per cent of the cases. TP53 gene mutations were not significantly related to overexpression or down-regulation of any of the proteins. Immunohistochemically, there was an increased protein level of TP53 in 77 per cent, p21 in 36 per cent, cyclin D1 in 45 per cent, cdk4 in 77 per cent, EGFR in 8 per cent, and MDM2 in 32 per cent of the cases. Expression of RB protein was normal in all cancers. Significant association of protein expression was seen between TP53 and MDM2 (p=0.005) and p21 and MDM2 (p=0.001). Furthermore, there may be an association between TP53 and p21 (p=0. 038) and cyclin D1 and cdk4 (p=0.045). The results revealed increased levels of TP53 protein in all MDM2-positive cases that did not show TP53 mutations, indicating TP53 protein stabilization and inactivation by complex formation with MDM2. In summary, the high number of cases showing an increased level of TP53 and cdk4 proteins suggests that these proteins play an important role in the neoplastic process in cancers of the uterine corpus.

Prognostic value and expression of p21(waf1/cip1) protein in prostate cancer

BACKGROUND

p21(waf1/cip1) protein is a cyclin-dependent kinase inhibitor able to arrest the cell cycle at the G1 phase by inhibiting DNA replication. The expression of p21(waf1/cip1) and its prognostic value in prostate cancer are largely unexplored.

METHODS

We used immunohistochemistry to analyze the expression of p21(waf1/cip1) in 213 prostate cancer cases, and the results were related to other known prognostic factors and patient survival during a long-term follow-up.

RESULTS

The expression of p21 (waf1/cip1) protein was significantly associated with high Gleason score (P = 0.001), DNA aneuploidy (P = 0.013), high S-phase fraction (P = 0.019), and expression of Ki-67 (P = 0.021) and bcl-2 (P = 0.001) as well as cyclin A (P = 0.035) and D proteins (P<0.001). In univariate survival analysis the signal of p21(waf1/cip1) was significantly related to unfavorable prognosis (P = 0.010) both in the entire cohort and in local tumors (P = 0.034). In multivariate analysis, M-category, clinical T-category, Gleason score, and patient age were independent prognostic factors. In local tumors the expression of p21(waf1/cip1) together with clinical T-category and S-phase fraction were significant independent predictors of cancer related survival.

CONCLUSIONS

The results suggest that the expression of p21(waf1/cip1) protein is associated both with cell proliferation and patient survival in prostate cancer.

Expression of phosphatidylethanolamine N-methyltransferase in Yoshida ascites hepatoma cells and the livers of host rats

Previous studies have implicated phosphatidylethanolamine N-methyltransferase-2 (PEMT2) in the regulation of non-neoplastic liver growth [Tessitore,L., Cui,Z. and Vance,E. (1997) Biochem. J., 322, 151-154]. We have now investigated whether or not PEMT2 is also involved in the control of proliferation of hepatoma cells growing in an animal and cell death by apoptosis in the liver of tumor-bearing rats. PEMT activity was barely detectable and PEMT2 protein was absent in hepatoma cells growing exponentially in vivo whereas CTP:phosphocholine cytidylyltransferase (CT) activity and expression were high. The lack of PEMT2 corresponded with the absence of its mRNA. Both PEMT2 protein and mRNA appeared when cells entered the stationary phase of tumor growth and, in parallel, CT expression decreased. The host liver first became hyperplastic and exhibited a slight increase in CT activity and decrease in PEMT2 expression. During the stationary phase of hepatoma growth the host liver regressed and eventually became hypoplastic following induction of apoptosis. The appearance of apoptosis in the host liver was associated with a marked reduction in both CT activity and expression as well as an enhancement of PEMT activity and PEMT2 expression. McArdle RH7777 hepatoma cells underwent apoptosis when transfected with cDNA for PEMT2. The evidence supports the proposal that PEMT2 may have a role in the regulation of 'in vivo' hepatoma and hepatocyte cell division as well as hepatocyte cell death by apoptosis.

Cleavage of poly(ADP-ribose) transferase during p53-independent apoptosis in rat liver after treatment with N-nitrosomorpholine and cyproterone acetate

The aim of this work was to study the role of the tumor suppressor p53 and of poly(ADP-ribose) transferase (pADPRT) in the control of hepatocyte apoptosis in two different in vivo models, i.e., during the process of tumor initiation by the genotoxin and cytotoxin N-nitrosomorpholine (NNM) and after withdrawal of the hepatomitogen cyproterone acetate (CPA). Treatment with NNM induces apoptosis followed by necrosis and regenerative DNA synthesis. At the first wave of apoptosis 12 h after NNM application, no p53 expression could be detected by immunohistochemical analysis and immunoblotting. However, 24 h after treatment, numerous p53-positive hepatocyte nuclei were detected, whereas hepatocytes in early and later stages of apoptosis were always negative. Simultaneously with the increased p53 levels, p21 protein was induced. This was accompanied by a block in replicative DNA synthesis, as detected by proliferating-cell nuclear antigen immunostaining. Concomitantly with the increase in apoptosis, dramatic degradation of the nuclear enzyme pADPRT was observed, as evidenced by immunoblotting and activity blotting. The decrease in pADPRT enzymatic activity observed 12 h after treatment coincided with the greatest extent of pADPRT cleavage. One prominent cleavage product was 64 kDa, suggesting that granzyme B was involved in pADPRT degradation. In the second in vivo model we used, i.e., withdrawal of treatment with the hepatomitogen CPA, apoptosis of excessive hepatocytes but no necrosis occurs. Again, no induction of p53 expression could be detected in the liver even at the maximum level of apoptosis, whereas a strong correlation between induction of apoptosis and cleavage of pADPRT to a 64-kDa fragment was observed. These results from whole-animal experiments strongly suggest that the induction of apoptosis in rat liver after genotoxic and cytotoxic damage and during regression of hyperplasia is driven by a p53-independent pathway but is accompanied by cleavage of pADPRT.