Retinoic acid activates p53 in human embryonal carcinoma through retinoid receptor-dependent stimulation of p53 transactivation function

Although retinoids are known to regulate gene transcription by activating retinoid receptors, the targets of retinoid receptors are largely unknown. This study indicates effective all-trans retinoic acid (RA)-induced differentiation of human embryonal carcinoma cells engages p53. Unexpectedly, RA has been found to activate the transactivation function of p53 in the human embryonal carcinoma cell line, NT2/D1, in a retinoid receptor-dependent manner. A derived RA-resistant line, NT2/D1-R1, is deficient in this activity and is co-resistant to cisplatin. This indicates that RA and cisplatin responses may share a common pathway involving p53 in embryonal carcinomas. RA has no effect on p53 steady-state protein levels in either line. RA enhances endogenous p53 transactivation activity in NT2/D1 but not NT2/D1-R1 cells. In addition, RA induces transactivation activity of a gal4-p53 fusion protein, suggesting that RA activates p53 independent of increasing p53 levels or sequence-specific DNA binding. This activity is absent in retinoic acid receptor gamma (RARgamma)-deficient NT2/D1-R1 cells but can be restored upon co-transfection with specific RARs. Transient transfection of a dominant-negative p53 construct in NT2/D1 cells blocks the RA-mediated transcriptional decline of a differentiation-sensitive reporter plasmid and enhances survival of NT2/D1 cells following cisplatin treatment. Taken together, these findings indicate that RA activates the intrinsic activation function of p53 by a novel mechanism independent of effects on p53 stability or DNA binding and that this activation may be a general mechanism that contributes to RA-mediated G1 arrest.

Evaluation of HER2, p53, bcl-2, topoisomerase II-alpha, heat shock proteins 27 and 70 in primary breast cancer and metastatic ipsilateral axillary lymph nodes

BACKGROUND

Breast cancer is a heterogeneous disease. Predictive biological markers (BM) of responsiveness to therapy need to be identified. Evaluation of BM is mainly done at the primary site. However, in the adjuvant therapy of breast cancer, the main goal is control of micrometastases. It is still unknown whether heterogeneity in the expression of BM between the primary site and its micrometastases exists.

OBJECTIVE

To evaluate the expression of some BM with potential predictive value from the primary breast cancer site and metastatic ipsilateral axillary lymph nodes.

PATIENTS AND METHODS

Focality (percentage of positive cells) and intensity staining scores were evaluated for each marker. Freshly cut sections (4 microm) from embedded blocks of breast cancer fixed in formalin or bouin were put onto superfrost slides (Menzel-Gläser). Protein expression was evaluated immunohistochemically (IHC) using monoclonal antibodies against: topo II-alpha (clone KiS1, 1 microg/ml, Roche) with a trypsine pre-treatment (P); HSP27 (clone G3.1, 1/60, Biogenex), HSP70 (clone BRM.22, 1/80, Biogenex) and HER2 (clone CB11, 1/40, Novocastra; without P); p53 (clone D07, 1/750, Dako) and bcl-2 (clone 124, 1/60, Dako) with citrate buffer as P.

RESULTS

Overall, the percentage of discordant marker status in the primary tumour and its metastatic lymph nodes was 2% for HER2, 6% for p53, 15% for bcl-2, 19% for topoisomerase II-alpha, 24% for HSP27 and 30% for HSP70. For the subgroup of patients with positive BM in the primary tumour, the percentage of discordance was 6% for HER2, 7% for p53, 14% for bcl-2, 19% for HSP70, 21% for topoisomerase II-alpha and 36% for HSP27. For the subgroup of patients with positive BM in the lymph nodes, the percentage of discordance was 9% for bcl-2, 15% for HER2 and p53, 21% for topoisomerase II-alpha, 22% for HSP27 and 25% for HSP70.

CONCLUSIONS

1) No biological marker had 100% concordant results. 2) Although some discordant cases might be explained by the limitations of the IHC technique, future studies aiming to evaluate the predictive value of BM in the adjuvant therapy of breast cancer should take into account a possible difference in BM expression between the primary and the metastatic sites.

Effect of ultraviolet light, methyl methanesulfonate and ionizing radiation on the genotoxic response and apoptosis of mouse fibroblasts lacking c-Fos, p53 or both

c-Fos and p53 are DNA damage-inducible proteins that are involved in gene regulation, cell cycle checkpoint control and cell proliferation following exposure to genotoxic agents. To investigate comparatively the role of c-Fos and p53 in the maintenance of genomic stability and the induction of apoptosis, we generated mouse fibroblast cell lines from knockout mice deficient for either c-fos (fos -/-) or p53 (p53-/-) or for both gene products (fosp53-/-). The sensitivity of these established cell lines was compared with the corresponding wild-type cells as to the cytotoxic, clastogenic and apoptosis-inducing effects of ultraviolet (UV-C) light and methyl methanesulfonate (MMS). Additionally, we analysed the frequency of apoptosis of the cell lines after treatment with ionizing radiation (IR). We observed c-fos-/-, p53-/- and fosp53-/- cells to be more sensitive than wild-type cells with respect to cell death, as measured in a cytotoxicity (MTT) assay. Regarding apoptosis, all deficient cell lines displayed hypersensitivity to UV-C light, MMS and IR. With chromosomal aberrations as the endpoint, the sensitivity of the double-knockout cells was between wild-type and single-knockouts. The results indicate that both c-Fos and p53 play an important role in protecting fibroblasts against a broad range of genotoxic agents. The results also show that, in fibroblasts, apoptosis induced by UV-C light, MMS and IR does not require p53 and that, in this cell type, p53 rather protects against DNA damage-induced apoptotic cell death.

Transcriptional dysregulation of the p73L / p63 / p51 / p40 / KET gene in human squamous cell carcinomas: expression of Delta Np73L, a novel dominant-negative isoform, and loss of expression of the potential tumour suppressor p51

We have recently identified a second p53 -related p73L gene, also referred to as p63 / p51 / p40 / KET gene, which encodes the 2 major isoforms p73L and p51 resulting from different exon usage at their amino terminal regions. Although p73L and p51 are suspected to play oncogenic and tumour suppressive roles in mammalian cells, respectively, no evidence of linkage between the expression of these isoforms and human cancers has been reported so far. In this study, we first investigated the expression profile of p51 and p73L in various human tumour cell lines and found that a novel isoform, termed DeltaNp73L, was predominantly expressed in squamous cell carcinomas. The expression profile of DeltaNp73L/p73L/p51 in primary human skin cancer specimens showed that the expression of p51 was frequently lost (62%) but was detected in all normal skin samples. In p51-expressing skin cancers, DeltaNp73L expression was associated at a high frequency (75%) though it was not detected in normal skin tissues. Transient co-transfection data indicate the possibility that DeltaNp73L can inhibit p53-, and more preferentially, p51-mediated transactivation. These data suggest that the loss of expression of p51 and/or the expression of DeltaNp73L might contribute to the pathogenesis of human squamous cell carcinomas.

Localization of metallothionein in urothelial carcinoma of the human urinary bladder: an immunohistochemical study including correlation with HLA-DR antigen, p53, and proliferation indices

Metallothionein (MT) is a low-molecular-weight cysteine-rich protein, which has the ability to bind and sequestrate heavy metal ions. Synthesis of MT is induced in a variety of tissues by these metal ions, as well as by endogenous factors such as glucocorticoids, interferon, interleukin-1 and vitamin D. Several lines of evidence show that MT may play a role in carcinogenesis. In this study MT expression was detected immunohistochemically, using a monoclonal antibody (E9) against a conserved epitope of I and II isoforms, in a series of 63 cases of urothelial carcinomas of the urinary bladder. Correlation between MT expression and HLA-DR antigen expression, p53, proliferation indices (PCNA and MIBI) as well as the various clinicopathological parameters, such as age, sex, squamous metaplasia, tumor grade, stage and recurrence were studied. In a semiquantitative analysis MT expression (> 10% of neoplastic cells) was observed in 12.7%, focal MT positivity in 11.1% and almost completely lack of MT expression in 76.2% of tumors. The incidence of MT expression was significantly higher (p=0.0002) in cases with high pathological tumor grades. MT values were significantly correlated with tumor stage (p=0.0009). A statistically significant positive correlation between MT expression and the HLA-DR antigen expression (p=0.001) was also detected. The data suggested that MT expression was correlated with a more aggressive behavior in urothelial bladder cancer.

[Detection of HPV in human esophageal cancer in high-incidence area and its correlation with p53 expression]

OBJECTIVE

To investigate the association of HPV with the development of esophageal cancer (EC) in a high-incidence area of EC and to elucidate its correlation with p53 overexpression.

METHODS

Thirty EC specimens were collected from Anyang, Henan. Four pairs of primers were designed to perform in situ hybridization (ISH) and in situ PCR(ISPCR). Immunohistochemical staining was used to detect p53.

RESULTS

HPV L1, HPV-16-E6 and HPV-16-E7 was detected in 10.0%, 60.0% and 63.3% of the EC samples, respectively. The detection rate of HPV-18-E6 was low(6.7%) and no EBV was detected. Overexpression of p53 was identified in 73.3% EC. With ISH or ISPCR, HPV-16-E6 was positive in 53.3% of EC.

CONCLUSION

The low detection rate of HPV L1 and high detection rate of HPV-16-E6 and E7 genes suggest that HPV may be partially lost when integrating into tumor cell genome, while E6 and E7 genes are intact. The results support a role of HPV-16 in the pathogenesis of EC in high incidence area. Although p53 mutation takes an important part in tumor pathogenesis, it is not consistent with the HPV existence in the EC cells.

Expression of vascular endothelial growth factor in renal cell carcinoma and the relation to angiogenesis and p53 protein expression

BACKGROUND AND OBJECTIVES

Vascular endothelial growth factor (VEGF) seems to play an important role in tumor angiogenesis. The tumor-suppressor gene p53 has been thought to regulate VEGF expression. We investigated the effect of VEGF expression on renal cell carcinoma (RCC) and the correlation between the expression of VEGF and tumor angiogenesis and p53 protein expression.

METHODS

Sixty-two RCCs were examined by immunohistochemical studies with anti-VEGF, anti-p53, and anti-CD34 antibodies.

RESULTS

Forty tumors (80.6%) were classified as VEGF positive, and 28 tumors (45.2%) were positive for p53 protein. The microvessel density was 75.3 +/- 33.5. A significant correlation was found between VEGF expression and both the nuclear grade (P < 0.05) and the TNM stage (P < 0.05). The tumors with VEGF expression had a significantly higher microvessel density than those without VEGF expression (P < 0.01). There was no statistically significant correlation between p53 protein and VEGF expression. No statistically significant differences in survival were found to be associated with microvessel density, VEGF expression or p53 protein expression. By using multivariate survival analyses, nuclear grade (P < 0.05) and TNM stage (P < 0.05) were the only independent prognostic factors.

CONCLUSIONS

Our data do not show a direct regulation of VEGF expression by p53. We suggest that VEGF expression plays a role in the promotion of angiogenesis in RCC.

Enforced expression of wild-type p53 curtails the transcription of the O(6)-methylguanine-DNA methyltransferase gene in human tumor cells and enhances their sensitivity to alkylating agents

We used isogenic human tumor cell lines to investigate the specific and direct effects of wild-type (wt) p53 on the expression of O(6)-methylguanine-DNA methyltransferase (MGMT), a DNA repair protein that confers tumor resistance to many anticancer alkylating agents. A p53-null, MGMT-proficient lung tumor cell line (H1299) was engineered to express wt p53 in a tetracycline-regulated system. High levels of p53 induction achieved by tetracycline withdrawal were accompanied by G(1) cell cycle arrest without significant apoptosis in this cell line. p53 accumulation resulted in a gradual and dramatic loss of MGMT mRNA, protein, and enzyme activity, whose levels were undetectable by day 3 of induction. The loss of MGMT protein was, however, not due to its degradation because the ubiquitin-promoted in vitro degradation of MGMT, which mediates the cellular disposal of the repair protein, was not altered by p53. Run-on transcription assays revealed a significant reduction in the rate of MGMT gene transcription. The negative regulation of MGMT expression by wt p53 was confirmed in two other human isogenic cell lines, namely, the GM47.23 glioblastoma, which contains a dexamethasone-inducible wt p53, and the H460 lung cancer cell line, in which wt p53 had been inactivated by the human papillomavirus E6 protein. Furthermore, a panel of four human tumor cell lines, including gliomas with wt p53 status, displayed markedly lower levels of MGMT gene transcripts than those having p53 mutations. Induction of wt p53 in these models led to a 3- and 2-fold increase in sensitivity to 1,3-bis(2-chloroethyl)-1-nitrosourea and temozolomide, respectively, which generate the MGMT-repairable O(6)-alkyl adducts in DNA. These results demonstrate that p53 is a negative regulator of MGMT gene expression and can create a MGMT-depleted state in human tumors similar to that achieved by O(6)-benzylguanine, a potent inhibitor of MGMT currently undergoing clinical trials. Thus, our study exposes an additional benefit associated with p53 gene therapy and provides a strong biochemical rationale for combining the MGMT-directed alkylators with p53 gene transfer to achieve improved antitumor efficacy.

[The determination of p53 protein in maxillary sinus carcinoma and its prognosis value]

OBJECTIVE

To determine whether p53 protein overexpression correlated with early tumor recurrence in carcinoma of maxillary sinus.

METHOD

Forty-five patients with T2N0M0 squamous cell carcinoma of maxillary sinus were treated with operation and/or radiotherapy. The median follow up time was 3 years. The ratio of local control was 62.2% (28 patients), as control group; The ratio of local recurrence and/or metastasis was 37.8% (17 patients), as experiment group. Cancer specimens were obtained before treatment. p53 protein overexpression, which indicated a mutated p53 gene, was analyzed by immunohistochemistry, using the mouse monoclonal antibody DO-7.

RESULT

Approximately 88.2% of the carcinoma that recurred locally overexpressed p53 protein, compared with only 28.6% of those with local control (P < 0.01). No significant relation was noted between p53 protein overexpression and pathohistologic grade. Intensity of staining did not predict tumor recurrence.

CONCLUSION

The study demonstrated that the p53 protein is an important prognostic marker on gene level for maxillary sinus carcinoma.

p53 gene mutation and protein accumulation during neoplastic progression in Barrett's esophagus

The aim of the present study was to characterize expression and mutation of p53 during the neoplastic progression from Barrett's esophagus to adenocarcinoma and to test the reliability of immunohistochemistry for p53 overexpression as an indicator of p53 mutation in this context. The association of both gene mutation and protein accumulation with clinicopathological findings and survival was also studied. A total of 77 samples from 30 esophagectomy specimens with Barrett's esophagus and adenocarcinoma of patients in longitudinal clinical follow-up were analyzed. Different lesions (intestinal metaplasia, dysplasia, and adenocarcinoma) as well as normal squamous-cell esophageal epithelia were sampled from formalin-fixed, paraffin-embedded tissues by microdissection. Mutations in p53 Exons 5 to 9 were detected by polymerase chain reaction-single-strand conformation polymorphisms (PCR-SSCP) and confirmed by direct DNA sequencing. Nuclear accumulation of p53 protein was analyzed immunohistochemically from tissue sections adjacent to those used for microdissection. p53 gene mutations were found in 17 and p53 protein accumulation were found in 20 tumor samples. Of the 17 adenocarcinomas with a p53 mutation, 16 stained positive for p53 protein. p53 mutations were detected significantly more frequently in high-grade dysplastic than in low-grade dysplastic lesions (77% versus 29%, P < 0.01). In contrast, nuclear accumulation of p53 was detected in 85% of high-grade and 71% of low-grade dysplastic lesions. In eight cases with p53 mutation, the mutation identified in the tumors was also detected in premalignant lesions, mainly in high-grade dysplasia. In four cases of p53-mutated tumors, clones with different p53 mutations were detected in premalignant lesions. Neither p53 mutations nor p53 protein accumulations were found in metaplastic lesions. In summary, we found that p53 mutations occurred mainly during the transition from low-grade to high-grade dysplasia in the neoplastic progression of Barrett's esophagus but not in the nondysplastic Barrett's mucosa. Mutational analysis of p53 by PCR-SSCP and p53 accumulation by immunohistochemistry were mostly concordant in adenocarcinoma and high-grade dysplastic lesions but frequently discordant in low-grade dysplastic lesions. No correlation between p53 gene mutation or p53 accumulation and clinicopathological findings was observed in this study.

p53, bcl-2 and thymidine phosphorylase as predictive markers of chemotherapy in patients with advanced and recurrent gastric cancer

PURPOSE

To study the relationship between expression of p53, bcl-2, thymidine phosphorylase and Ki-67 and the response to chemotherapy and survival in patients with recurrent and advanced gastric cancer.

MATERIALS AND METHODS

Protein expression was assessed immunohistochemically in 28 patients treated with 5-fluorouracil, pirarubicin and cisplatin (FAP).

RESULTS

The response rate in patients positive for p53 expression was 23% compared with 47% of p53-negative patients. The response rate was also reduced from 44% in patients negative for bcl-2 protein expression to 25% in bcl-2 positive patients. Thymidine phosphorylase (dThdPase) expression was observed in 20 patients (71%), 50% of whom responded to chemotherapy, while patients negative for dThdPase expression did not respond to chemotherapy. The correlation between response rate and dThdPase-positivity was statistically significant (p < 0.05). However, with regard to patient survival, p53- and bcl-2-negative patients showed significantly better survival than patients positive for p53 and/or bcl-2 (p = 0.036).

CONCLUSION

While dThdPase expression may be a useful predictor of response to chemotherapies that include 5-FU, p53 and bcl-2 expression may predict the outcome of patients with recurrent and advanced gastric cancer following chemotherapy.

Apoptosis and p53 overexpression in human rectal cancer; relationship with response to hyperthermo-chemo-radiotherapy

Hyperthermo-chemo-radio (HCR) therapy has been found to be effective for rectal cancer. Biomarkers for predicting the effect of HCR therapy are important in determining optimum treatment regimens. Hyperthermo-chemo-radiotherapy (HCR therapy), consisting of hyperthermia at 42 degrees C to 45 degrees C for 40 minutes (twice per week for two weeks), a total of 60 Gy irradiation and administration of 1-hexylcarbamoyl-5-fluorouracil (HCFU) (total 8400 mg), were prescribed pre-operatively for 29 patients with rectal cancer, using tissue specimens collected at pre-treatment biopsy. Apoptosis and overexpression of p53 protein were investigated histopathologically and immunohistochemically. On termination of HCR therapy, all the tumors were surgically resected and effectiveness of the therapy was evaluated histologically. Spontaneous apoptosis was evident in the pre-treatment cancer tissues of 14 patients (48.2%). In this apoptosis-positive group, the positive rate of expression of the p53 protein (21.4%, 3 out of 14) was lower as compared to findings in the apoptosis-negative group (66.7%, 10 out of 15). The response to HCR therapy was better in the apoptosis-positive group than in the apoptosis-negative group. We propose that spontaneous apoptosis is closely related to the function of wild-type p53 protein and is also a predictive biomarker of the effect of HCR therapy for patients with rectal cancer.

HER-2/neu overexpression in breast cancer: an immunohistochemical study including correlations with clinicopathologic parameters, p53 oncoprotein and cathepsin-D

PURPOSE

To evaluate the relationship between HER-2/neu overexpression and standard as well as investigational prognostic factors in Greek females with invasive breast carcinoma.

MATERIALS AND METHODS

Paraffin-embedded tumor sections from 128 consecutive primary breast cancer patients were screened for HER-2/neu oncoprotein (p185) overexpression by immunohistochemistry using the polyclonal antibody A 0485. The relationship between HER-2/neu staining and other established markers of prognosis were examined using both a univariate and a multivariate analysis.

RESULTS

HER-2/neu overexpression was detected in 46.1% of tumors. No statistical correlation was found between HER-2/neu and age, tumor diameter, histologic type, nodal status, tumor grade, stage, estrogen and progesterone receptor status or cathepsin-D. A significant correlation was noted between HER-2/neu and p53 overexpression in the total sample (p=0.014) as well as in node-positive patients (p=0.026). In those groups, HER-2/neu and p53 co-expression was found in 19.5% and 21.6% of cases, respectively. In node-negative patients, HER-2/neu overexpression did not correlate with any other marker.

CONCLUSION

HER-2/neu overexpression seemed to correlate only with p53 oncoprotein.

Differences in estrogen receptor status, HER2, and p53 comparing metachronous bilateral breast carcinoma

BACKGROUND AND OBJECTIVES

We analyzed the clinicopathologic characteristics and tumor biology of metachronous bilateral breast carcinoma with regard to p53, HER2 and hormone receptor status.

METHODS

A consecutive series of 54 female metachronous bilateral breast carcinoma patients treated at the National Cancer Center Hospital between 1980 and 1997 were the primary source of these retrospective data. Clinicopathologic background factors were analyzed, and immunohistochemical staining for p53, HER2, and hormone receptor status was carried out on paraffin-embedded specimens.

RESULTS

There were no significant differences in clinical stage, p53 and HER2 expression levels between the first and second primary tumors. The positive rates for ER and PR were 48% (25 of 52) and 46% (25 of 54) for the first tumors, but only 19% (10 of 52) and 32% (17 of 54) for the second tumors (P = 0.004 for ER, P = 0.16 for PR), showing a significant loss of ER.

CONCLUSIONS

Our findings indicate that p53 and HER2 expression levels in the second tumors might be the same as those of the first tumors in metachronous bilateral breast carcinoma; however, loss of ER was more frequently observed in the second primary tumors than in the first tumors.

Condensation by DNA looping facilitates transfer of large DNA molecules into mammalian cells

Experimental studies of complete mammalian genes and other genetic domains are impeded by the difficulty of introducing large DNA molecules into cells in culture. Previously we have shown that GST-Z2, a protein that contains three zinc fingers and a proline-rich multimerization domain from the polydactyl zinc finger protein RIP60 fused to glutathione S-transferase (GST), mediates DNA binding and looping in vitro. Atomic force microscopy showed that GST-Z2 is able to condense 130-150 kb bacterial artificial chromosomes (BACs) into protein-DNA complexes containing multiple DNA loops. Condensation of the DNA loops onto the Z2 protein-BAC DNA core complexes with cationic lipid resulted in particles that were readily transferred into multiple cell types in culture. Transfer of total genomic linear DNA containing amplified DHFR genes into DHFR(-) cells by GST-Z2 resulted in a 10-fold higher transformation rate than calcium phosphate co-precipitation. Chinese hamster ovarian cells transfected with a BAC containing the human TP53 gene locus expressed p53, showing native promoter elements are active after GST-Z2-mediated gene transfer. Because DNA condensation by GST-Z2 does not require the introduction of specific recognition sequences into the DNA substrate, condensation by the Z2 domain of RIP60 may be used in conjunction with a variety of other agents to provide a flexible and efficient non-viral platform for the delivery of large genes into mammalian cells.

Human herpesviruses HHV-4 (EBV) and HHV-6 in Hodgkin's and Kikuchi's diseases and their relation to proliferation and apoptosis

BACKGROUND

Human herpesviruses types 4 and 6 (EBV, HHV-6) are frequently found in Hodgkin 's disease (HD) and--to a certain extent--in Kikuchi-Fujimoto's disease (KFD). Both viruses are apparently related to proliferative and/or apoptotic processes as represented by HD or KFD respectively.

OBJECTIVE

To correlate frequency and location of antigen- and DNA expression of both viruses in HD and KFD tissue sections in relation to markers for cell proliferation and apoptosis.

STUDY DESIGN

Archival lymph node biopsies from 103 patients with HD and 14 KFD patients were investigated immunohistologically for viral antigen expression (EBV LMP- 1: HHV-6 pl 10/60), Ki67/PCNR, marker for proliferation (MIB1)/p53 and WAF1 for apoptosis. Viral DNA was shown by in situ hybridization. Apoptosis was determined by ISEL and TUNEL techniques.

RESULTS

HD is frequently infected by both EBV and HHV-6 while KFD tends to be infected only by HHV-6. EBV in HD is present in HD cells and in Reed-Sternberg cells (HD/RS cells), HHV-6 preferentially in lymphocytes and in histiocytes in both HD and in KFD. Proliferation marker Ki67 is found in lymphocytes and histiocytes of both diseases and in HD and RS cells in HD. Apoptosis is demonstrated in lymphocytes and histiocytes preferentially in KFD and to a lesser extent also in HD.

CONCLUSION

Although EBVand HHV-6 may not be openly oncogenic in HD and KFD, they may well influence the course of the disease. Dual infection in HD appears to support proliferative processes, i.e. a predominance of EBV effects. Single infection with HHV-6 in KFD instead appears to favor an apoptotic course. These effects are--according to the literature--possibly cytokine-mediated.

Malnutrition-induced macrophage apoptosis

BACKGROUND

Human and murine studies suggest protein-calorie malnutrition (PCM) results in significant host immunosuppression resulting in increased morbidity and mortality. Apoptosis has been implicated as an important mediator in the immunosuppression observed in several disease states. This study was designed to characterize macrophage apoptosis in a murine model of PCM and investigate components that regulate the apoptotic process, such as protein kinase C (PKC) and Bcl-2 activity.

METHODS

Swiss-Webster mice (n = 50) were randomly assigned to receive either a control (24% protein) or a PCM diet (0% protein) for 7 days. Peritoneal macrophages were harvested and detection of apoptosis was performed by terminal deoxy-transferase-mediated deoxyuridine triphosphate (dUTP) nick-end labeling (TUNEL) and propidium iodide DNA staining under baseline and pro-apoptotic conditions. Pro-apoptotic conditions included cells treated with tumor necrosis factor-alpha (TNF-alpha) (10 ng/mL), interferon-gamma (IFN-gamma) (10 ng/mL), and a combination of both agents. In addition, levels of PKC activity and expression of Bcl-2 and p53 protein were measured.

RESULTS

Peritoneal macrophages from PCM mice had a significantly greater amount of apoptosis at baseline and under stimulated conditions compared with controls. Levels of PCM apoptosis were elevated at baseline by TUNEL staining compared with macrophages from the control group (16.5% +/- 1.4%, versus 4.5% +/- 1.1%, P <.01). In addition, peritoneal macrophages from the malnourished animals were significantly more susceptible to the apoptotic effect of TNF-alpha and the effects of INF-gamma (27.3% +/- 2.1% and 31% +/- 1.4%) compared with control mice (5.5% +/- 0.7% and 7.2% +/- 0.5%, P <.01), respectively. Again, an increase in the baseline apoptosis rate was demonstrated in peritoneal macrophages from PCM mice compared with control fed mice (13.2% +/- 4.4% versus 4.3% +/- 3.1%, P <.01) as measured by propidium iodide staining. The combination of agents, TNF-alpha and INF-gamma, resulted in an additive apoptotic effect in the malnourished host compared with the control animals (43.4% +/- 4.7% versus 10.5% +/- 2.2%, P <.01), respectively. Furthermore, there was a significant decrease in the mean total PKC activity in the malnourished macrophages compared with results in controls (110,000 +/- 8000 versus 60,000 +/- 4000 cpm, P <.01). Similar changes were also observed in PKC cytosolic and membrane activity between both groups. In addition, Bcl-2 protein expression was significantly decreased in PCM animals compared with control animals.

CONCLUSIONS

Thus, peritoneal macrophages from PCM mice exhibit significantly greater levels of apoptosis at baseline and when stimulated with pro-apoptotic agents compared with controls. The propensity of macrophages from PCM mice to undergo apoptosis may be attributable in part to decreased PKC activity and Bcl-2 protein expression. These findings may help to explain the associated immune dysfunction observed in malnutrition.

[Study on p53 gene expression following transient ischemia in the gerbil]

OBJECTIVE

To study the expression of p53 gene after transient ischemia in the gerbil.

METHODS

Northern blot was used to detect the expression of the p53 mRNA in the forebrain during different periods after post-ischemic reperfusion in the gerbil.

RESULTS

The expression of p53 mRNA increased in the forebrain during the 6th hour to the 3rd day of reperfusion following 6 min of ischemia (P < 0.05).

CONCLUSION

The high level expression of p53 might induce neuronal apoptosis after ischemia.

Site-specific phosphorylation of human p53 protein determined by mass spectrometry

Human recombinant p53 (r-p53) protein was studied by mass spectrometry (MS) to determine site-specific posttranslational differences between basal and hyperphosphorylated r-p53. Wild-type p53 was basally expressed after baculovirus infection while a parallel preparation was treated with the phosphatase inhibitor okadaic acid during the terminal stages of expression to create a hyperphosphorylated form of p53 known for its higher DNA binding and transcriptional activation. After immunoaffinity and HPLC purification, MALDI/MS measured a higher molecular mass for r-p53 from okadaic acid treatment relative to control, suggesting a higher phosphorylation state. This was supported by an acidic shift of r-p53 isoforms separated by gel isoelectric focusing. Employing a variety of mass spectrometric analyses combined with separation and affinity techniques, six specific phosphorylation sites of p53 were identified. The MS data indicated that hyperphosphorylated p53 showed a higher degree of phosphorylation than basal p53 at specific amino- and carboxy-terminal sites. In particular, ESI-MS demonstrated that Ser(315) was entirely phosphorylated after okadaic acid treatment, as confirmed biochemically by CDK2 kinase assay and by isoelectric focusing. In summary, MS analysis uniquely revealed increased, site-specific phosphorylations on p53 after phosphatase inhibition, particularly at Ser(315), which may be critical molecular events in defining p53 activity.

8-Cl-adenosine induces differentiation in LS174T cells

8-Cl-adenosine represents a novel nontoxic chemotherapeutic agent shown to inhibit growth of a number of colorectal cancer cell lines. We have utilized the mucin-secreting colorectal cancer cell line, LS174T, to assess the growth inhibitory properties of 8-Cl-adenosine independent of its parental compound, 8-Cl-cAMP. Conversion of 8-Cl-cAMP to 8-Cl-adenosine is required for growth inhibition in LS174T cells. 8-Cl-Adenosine inhibited growth by inducing a G1 cell cycle arrest that was associated with large (eightfold) increases in p21WAF1/Cip1 and p53 protein levels and a decrease in the phosphorylation status of the retinoblastoma protein. LS174T cells did not undergo apoptosis. In addition, 8-Cl-adenosine also induced some degree of enterocytic differentiation. Both villin protein levels as well as alkaline phosphatase activity rose (2- and 3.5-fold, respectively) in response to treatment with 8-Cl-adenosine. Our results suggest that in LS174T cells, 8-Cl-adenosine not only serves as a growth inhibitory agent but also as an inducer of enterocytic differentiation.

Xeroderma pigmentosum group A gene action as a protection factor against 4-nitroquinoline 1-oxide-induced tongue carcinogenesis

To test the hypothesis that nucleotide excision repair (NER) plays a protective role in chemical carcinogenesis in internal organs, xeroderma pigmentosum group A gene-deficient (XPA(-/-)) mice, heterozygous (XPA(+/-)) and wild-type (XPA(+/+)) mice were orally administered 0.001% 4-nitroquinoline 1-oxide (4NQO) in their drinking water and compared. After 50 weeks of 4NQO exposure, tongue squamous cell carcinomas (SCCs) occurred in XPA(-/-) mice only, no tumors being observed in XPA(+/-) and XPA(+/+) animals. Of the XPA(-/-) mice 86% had tumors and 100% demonstrated multiple foci of dysplastic epithelium in the tongue. Accumulation of p53 protein was immunohistochemically detected in 56% of the SCCs. Mutational analysis of the p53 gene (exons 4-10) in carcinoma DNA revealed missense mutations in exons 5 and 9 in four of 20 samples. Our results clearly demonstrate that the NER gene XPA acts as a defensive factor against 4NQO-induced tongue carcinogenesis in vivo.

p53 and p21waf-1 expression correlates with apoptosis or cell survival in poorly differentiated, but not well-differentiated, retinoblastomas

In human retinoblastomas, rare genetic mutations of the retinoblastoma gene cause massive cell proliferation, altered differentiation, and tumor formation; but paradoxically, this is accompanied by extensive apoptotic cell loss. We quantified the immunohistochemical distribution of p53, its downstream effector p21 (WAF-1), and apoptotic cells in 50 human retinoblastomas, within three concentric zones of sleeves of tumor cells surrounding blood vessels. In poorly differentiated retinoblastomas, both p53 expression and apoptosis increase toward the outer zone of tumor sleeves, whereas p21 expression occurs primarily within the inner zone. This staining pattern of p53 expression is reversed in well-differentiated tumors, whereas p21 staining and apoptotic cell distributions are unchanged. We detected no p53 mutations in four retinoblastomas and two retinoblastoma cell lines. We postulate that oxygen and cell "survival/growth factors" delivered via blood vessels protect retinoblastoma cells from apoptosis. In poorly differentiated tumors, apoptosis is spatially associated with increased p53 expression and may be p53 mediated, but in well-differentiated tumors, apoptosis does not colocalize with p53 and may be p53 independent. In retinoblastomas, p21 is involved not in cell death by apoptosis but in cell survival. Thus, p53 varies its expression (and by implication its function) with altered differentiation in retinoblastomas.

Characterization of molecular abnormalities in human fibroblastic neoplasms: a model for genotype-phenotype association in soft tissue tumors

Desmoid tumors and fibrosarcomas (FS) are part of a wide spectrum of disordered fibroblastic growth that display striking clinical and phenotypic differences. This study was designed to characterize molecular abnormalities that are associated with these differences and to determine their clinical relevance. A cohort of 24 desmoid tumors and 25 low-grade (LG) and 14 high-grade (HG) FS that were clinically and pathologically well characterized was analyzed for alterations in expression of Ki-67, Bcl-2, retinoblastoma gene product (pRB), and p53 by immunohistochemistry. LG-FS and HG-FS showed abnormal expression of Ki-67 (32 versus 86%), Bcl-2 (48 versus 57%), and pRB (56 versus 93%). In contrast, desmoid tumors showed a normal phenotype with these markers. p53 overexpression was identified in 20% of LG-FS and in 29% of HG-FS cases but only in 4% of desmoid tumors. There was an increasing trend in the proportion of abnormal expression of Ki-67, Bcl-2, pRB, and p53 with the increase of tumor aggressiveness from desmoid tumors to LG-FS to HG-FS. The molecular differences between tumor entities were highly statistically significant (P < 0.01). Significant associations between abnormal expression of pRB and recurrence-free survival of LG-FS patients (P = 0.05) and between Ki-67 overexpression and recurrence-free survival for tumors of >5 cm were observed (P = 0.02). The demonstrated differences of molecular alterations in HG-FS, LG-FS, and desmoids appear to be related to biological aggressiveness of such tumors, and they might be useful to differentiate between histologically similar cases of desmoid tumors and LG-FS. pRB and Ki-67 status may be useful to predict recurrence in certain subsets of patients.

Overexpression of transforming growth factor-beta3 immunohistochemical staining in extramammary Paget's disease, but downregulated expression in Bowen's disease

BACKGROUND

The role of transforming growth factor-beta (TGF-beta) in carcinogenesis is complex, with some reports indicating a tumor inhibition role and others indicating a tumor promotion role. In particular, TGF-beta3 is thought to play a key role in controlling epithelial homeostasis. Immunopositive p53 has been demonstrated in a variety of human malignant tumors and its role in oncogenesis and tumor progression is thought to be important. Extramammary Paget's disease (EPD) and Bowen's disease are skin cancers of unknown histogenesis.

OBJECTIVE

To clarify the role of TGF-beta3 and p53 in EPD and Bowen's disease and to better understand the origin of these disorders.

METHODS

Specimens were obtained from 12 patients with EPD and 12 patients with Bowen's disease seen at our clinic between 1993 and 2000. TGF-beta3 and p53 immunohistochemical staining was performed.

RESULTS

In three of the 12 EPD patients and five of the 12 Bowen's disease patients, positive p53 staining was detected. In contrast, TGF-beta3 overexpression was detected in all EPD patients, whereas downregulated TGF-beta3 expression was detected in all Bowen's disease patients.

CONCLUSIONS

The present data suggest different roles for TGF-beta3 in abnormal epidermal cells in EPD and Bowen's disease. Thus, TGF-beta3 expression may be modulated differently via a p53-dependent or -independent pathway in the pathogenesis of EPD and Bowen's disease. Moreover, high TGF-beta expression appears to be a useful indicator of tumor activity in EPD.