Inhibition of apoptosis by survivin predicts shorter survival rates in colorectal cancer

Deregulated inhibition of apoptosis (programmed cell death) may facilitate the insurgence of neoplasia, but whether it also influences the outcome of common cancers has remained controversial. In this study, we investigated the expression of a novel inhibitor of apoptosis, survivin, in colorectal cancer and its relationship with tumor cell apoptosis and overall prognosis. By immunohistochemistry, survivin was expressed in 91 of 171 (53.2%) cases of colorectal carcinomas of histological stages 0 to IV. In contrast, normal colon epithelium did not express survivin. Although survivin expression did not correlate with p53 abnormalities (46.5% versus 58.0%; P = 0.18), survivin-positive cases were strongly associated with bcl-2 expression (72.5% versus 27.4%; P < 0.0001) and reduced apoptotic index (0.76% +/- 0.39% versus 1.17% +/- 0.62%; P < 0.0001). Expression of survivin alone in bcl-2-negative (discordant) cases also resulted in reduced apoptotic index (0.82% +/- 0.57% versus 1.16% +/- 0.66%; P = 0.0046). When analyzed for prognostic significance, patients with low apoptotic index (< 0.97%) had worse survival rates than the group with high apoptosis (P < 0.001), and a multivariate Cox proportional hazard model identified reduced apoptosis as an independent predictive factor for overall survival (P < 0.0001). These data demonstrate that apoptosis inhibition by survivin, alone or in cooperation with bcl-2, is an important predictive/prognostic parameter of poor outcome in colorectal carcinoma and identify survivin as a new diagnostic/therapeutic target in cancer.     

Clinicopathologic analysis of bcl-2 immunostaining in breast carcinoma

Tissue sections of 81 breast carcinomas and 19 benign breast tissues were immunostained with a monoclonal antibody to the bcl-2 gene product, a cytoplasmic protein that regulates apoptosis. The degree of immunoreactivity was then compared with clinicopathologic parameters and to immunostaining for mutated p53 gene product. Immunoreactivity for bcl-2 was present consistently in lymphocyte populations and in residual benign lobules. Apocrine metaplasia (n = 6) and lactating breast (n = 1) exhibited minimal bcl-2 expression, whereas duct hyperplasia (n = 10) showed staining of cells primarily at the periphery of the involved structure and adenosis (n = 7) displayed staining in a majority of cells. Neoplastic epithelial bcl-2 immunoreactivity was negative or minimally positive (staining in 1-5% of cells) in 42% of cases, heterogeneous (staining in 6-30% of cells) in 27% of cases, and diffuse (> 30% of cells) in 31% of cases. Immunostaining for bcl-2 correlated with the presence of estrogen receptor (bcl-2 negative, 16% estrogen receptor positive versus bcl-2 positive, 88% estrogen receptor-positive; P < 0.001), with differentiation (bcl-2 negative, 62% poorly differentiated versus bcl-2 positive, 8% poorly differentiated; P < 0.001) and with better disease-free survival (bcl-2 negative, 82% recurrence versus bcl-2 positive, 28% recurrence; P = 0.0001; 52-mo mean follow-up). Immunostaining for p53 in greater than 5% of tumor cells was observed in 39% of cases and was more frequent in bcl-2-negative tumors (18/35, 51%) as opposed to bcl-2-positive tumors (14/46, 30%); P = NS. Disease recurrence correlated with p53 staining, which was observed in 51% of tumors that relapsed versus only 22% of tumors that did not recur. We conclude that bcl-2 is expressed in benign breast tissues that retain proliferative capacity and partial differentiation. Moreover, in neoplastic breast tissue, it is better correlated with a differentiated, "hormonally responsive," prognostically favorable phenotype than with disabled p53 gene function.     

Bcl-2 expression and its association with cell kinetics in human gastric carcinomas and intestinal metaplasia

The bcl-2 protooncogene was initially discovered at the t(14;18) chromosomal breakpoint in follicular lymphomas. It has been demonstrated that bcl-2 protein (Bcl-2) expression blocks apoptosis and plays an important role in cell development and maturation. In the present study, Bcl-2 expression was immunohistochemically examined in 103 cases of gastric carcinoma, as well as 64 cases of non-carcinous gastric mucosa, and its correlation with apoptosis, cell proliferation and p53 immunoreactivity was investigated. Bcl-2 was detected in 18.0% of differentiated-type gastric carcinomas (9 of 50) and 7.5% of the undifferentiated type (4 of 53). In adjacent intestinal metaplastic gastric epithelium, the incidence of Bcl-2 positivity in the incomplete type (21/23, 91.3%) was significantly higher than in the complete type (23/41, 56.1%) (P < 0.04). Double immunostaining for Bcl-2 and Ki-67 clearly revealed the majority of Bcl-2-positive cancer cells to be in a nonproliferating state, although some cancer cells expressed both proteins together. Statistical assessment demonstrated that the average Ki-67 labeling index and apoptotic labeling index in Bcl-2-positive foci were significantly lower than in Bcl-2-negative foci (P < 0.0001, P < 0.0003). In addition, a significant dissociation between Bcl-2 and p53 immunoreactivity was found in cancer tissues. These results indicate that aberrant Bcl-2 expression in gastric carcinomas possibly originates from intestinal metaplastic epithelium, and suggest a possible role in tumor development and growth.     

Expression of bcl-2, p53 and Ki-67 in arsenical skin cancers

To investigate the regulation of apoptosis and proliferation in arsenic-induced skin cancers, we examined the expression of bcl-2, p53, and Ki-67 using immunohistochemical staining. Thirty patients with Bowen's disease (BD), ten with basal cell carcinoma (BCC), eight with squamous cell carcinoma (SCC) and eleven of perilesional normal skin (PLN) of the non-sun exposure sites from endemic area were examined. The results showed that: 1) bcl-2 was expressed in all of the BCC homogeneously, in none of the SCC, and in 12/30 of the BD focally or homogeneously; 2) p53 was expressed in all of the arsenical skin cancers with a labelling index of 75 +/- 14% of BD, 50 +/- 17% of BCC, 61 +/- 15% of SCC, and also in all of the perilesional normal skin with a labelling index of 55 +/- 24%; 3) Ki-67 was expressed in all of the skin cancers with labelling index of 58 +/- 17% of BD, 12 +/- 7% of BCC, 47 +/- 21% of SCC, and in 9/11 of PLN with a labelling index of 41 +/- 24%. Expression of bcl-2 in BCC or BD is related to the phenotype of germinative basal cell. The constant expression of bcl-2 i early dysplastic cells of BD and the earliest expression of P53 in the basal cells of perilesional normal skin indicate that the initial step of arsenic-induced carcinogenesis is from the basal germinative cells. There is no mutual relationship between bcl-2, p53 or Ki-67 expression in any type of the arsenical skin cancers, but there is a positive correlation between p53 and Ki-67 expression identified in perilesional normal skin. BD had the highest labelling index of p53 and Ki-67.     

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

BACKGROUND: The balance among cell proliferation, cell differentiation, and cell death determines the cell number in a population as well as the size or even the stage of a tumor. Thus, to improve our understanding of the pathogenesis of neoplasms, it is important to investigate the regulation of both cell proliferation and cell death. METHODS: This study examined the occurrence of apoptosis and proliferative capacity in 46 breast carcinomas: 20 intraductal carcinomas (ductal carcinomas in situ [DCIS]) and 26 infiltrative ductal carcinomas (IDC). Terminal deoxynucleotidyl transferase-mediated digoxigenin-11-dUTP nick end labeling (TUNEL) and immunostaining with the Ki-67 antibody were used in the examination. A ladder of DNA fragments induced by apoptosis was demonstrated by means of DNA agarose gel electrophoresis in 10 of the available TUNEL positive and negative samples. RESULTS: The results were correlated with p53, bcl-2, estrogen receptor (ER), and progesterone receptor (PR) protein expression, which would suggest association with apoptosis by immunohistochemistry. The apoptosis and proliferation of each cancer were expressed as the number of tumor cells undergoing apoptosis and proliferation per 1000 tumor cells. The extent of apoptosis was more frequently observed in DCIS than in IDC (21.9+/-6.8 vs. 4.0+/-0.9, P < 0.001), and the proliferation activity was significantly higher in IDC than in DCIS (16.8+/-6.5 vs. 3.5+/-0.8, P < 0.006). Apoptosis associated with MIB-1 positive cells and TUNEL labeling was significantly higher in IDC than in DCIS (3.26 vs. 0.42, P=0.001). In DCIS, apoptosis was correlated with p53 (r=0.663, P=0.005), and p53 had a reverse correlation with bcl-2 (r=0.620, P= 0.018). Moreover, bcl-2 expression was associated with ER (P=0.028) and PR (P= 0.005) expression in both DCIS and IDC. CONCLUSIONS: The results of this study show that a higher degree of apoptosis and lower proliferation activity in intraductal carcinoma result in a steady-state, self-renewing condition in which net growth of the tumor is rare. The results also indicate that apoptosis was altered by the expression of p53, bcl-2, ER, and PR.     

Evidence of significant apoptosis in poorly differentiated ductal carcinoma in situ of the breast

Following breast-conserving surgery for ductal carcinoma in situ (DCIS), the presence of comedo necrosis reportedly predicts for higher rates of post-operative recurrence. To examine the role of programmed cell death (apoptosis) in the aetiology of the cell death described as comedo necrosis, we studied 58 DCIS samples, using light microscopy, for morphological evidence of apoptotic cell death. The percentage of apoptotic cells (apoptotic index, AI) was compared between DCIS with and without evidence of 'comedo necrosis' and related to the immunohistochemical expression of the anti-apoptosis gene bcl-2, mitotic index (MI), the cellular proliferation antigen Ki67, nuclear grade and oestrogen receptor (ER) status. AI was significantly higher in DCIS samples displaying high-grade comedo necrosis than in low-grade non-comedo samples: median AI = 1.60% (range 0.84-2.89%) and 0.45% (0.1-1.31%) respectively (P < 0.001). Increasing nuclear grade correlated positively with AI (P < 0.001) and negatively with bcl-2 expression (P = 0.003). Bcl-2 correlated negatively with AI (P = 0.019) and strongly with ER immunoreactivity (P < 0.001). Cellular proliferation markers (MI and Ki67 immunostaining) correlated strongly with AI and were higher in comedo lesions and tumours of high nuclear grade (P < 0.001 in all cases). Thus, apoptosis contributes significantly to the cell death described in ER-negative, high-grade DCIS in which a high proliferative rate is associated with a high apoptotic rate. It is likely that dysregulation of proliferation/apoptosis control mechanisms accounts for the more malignant features typical of ER negative comedo DCIS.     

Old and new substrates in clinical nutrition

Bcl-2 has been demonstrated to inhibit apoptosis in breast cancer cells in vitro, and the ratio between Bcl-2 and its proapoptotic homologue Bax seems to be an important determinant of cellular sensitivity to induction of apoptosis. However, little information is available on the relationship between Bcl-2 and the rate of apoptotic and necrotic cell death in breast tumours. From a series of 441 premenopausal, lymphnode-negative breast cancer patients, a subset of 49 tumours was selected in which immunostaining for the 26-kDa isoform of Bcl-2 was either absent (n = 23) or very high (n = 26). High expression of Bcl-2 was found to be strongly associated with low rates of apoptotic (P < 0.001) and necrotic cell death (P < 0.001). The mean value of the apoptotic index was 2.69%+/-1.40% in Bcl-2-negative tumours and 0.68%+/-1.00% in Bcl-2-positive tumours. Expression of the proapoptotic protein Bax correlated neither with Bcl-2 nor with the frequency of apoptotic cells. Immunostaining for the antiapoptotic Bcl-2 homologue BcI-X(L) correlated with Bcl-2 expression (P < 0.001) but not with apoptosis. High proliferation rate and high tumour grade (Bloom-Richardson) were strongly associated with absence of Bcl-2 expression (P< 0.001). p53 accumulation was associated with absence of Bcl-2 expression and increased apoptotic activity. Loss of Bcl-2 expression was strongly correlated with increased apoptotic and necrotic cell death, high proliferation rate and high tumour grade, supporting a model in which Bcl-2 not only mediates cell death, but also cell division in breast cancer tissue, and in which regulation of cell division and cell death are tightly linked.     

Detection of P2 precursors in the sperm cells of infertile patients who have reduced protamine P2 levels

Many chemotherapeutic agents are thought to exert their genotoxic effects through induction of programmed cell death (PCD) (apoptosis) in tumor cells. The bcl-2 is an anti-apoptotic oncoprotein and can confer a survival advantage to tumor cells by preventing apoptosis. Overexpression of bcl-2 may therefore be implicated in resistance to chemotherapy. We studied the significance of bcl-2 expression and the PCD index in pediatric acute lymphoblastic leukemia. Evaluation of bcl-2 by immunocytochemistry and PCD by an enzymatic end labelling technique using biotin-dUTP was carried out in a total of 55 cases and 40 controls. Bcl-2 was found to be expressed in 47% (26/55) of the acute lymphoblastic leukemia cases. The positive cells varied from 0-49% among individual samples. Pre-treatment (spontaneous) apoptosis was observed in 62% (34/55) cases. The mean pre-treatment PCD index was 8.27 1.3%, while the median PCD index was 5. The PCD value for the leukemic samples analyzed were then classified as either high apoptosis values ( 5) and low apoptosis values (<5). PCD index was high in 53% (29/55) and low in 47% (26/55). However, 23% (13/55) of cases did not show presence of either apoptosis or bcl-2. There was no association between clinical and laboratory parameters with the apoptotic index or bcl-2 protein expression. However, evaluation of apoptotic index and bcl-2 expression on day 7 of induction chemotherapy showed a borderline correlation between these markers and initial WBC count, presence of mediastinal mass and hepatosplenomegaly. Follow-up of these patients is being done to look for any association between treatment response and apoptosis.     

Differential CD95 expression and function in T and B lineage acute lymphoblastic leukemia cells

CD95 (Fas/APO-1) is a cell surface receptor able to trigger apoptosis in a variety of cell types. The expression and function of the CD95 antigen on leukemic blasts from 42 patients with B lineage and 53 patients with T lineage acute lymphoblastic leukemia (ALL) were investigated using immunofluorescence staining and apoptosis assays. The CD95 surface antigen was expressed in most ALL cases, with the T lineage ALL usually showing a higher intensity of surface CD95 expression as compared with the B lineage ALL cells (relative fluorescence intensity, RFI: 4.8 +/- 0.47 vs 2.2 +/- 0.23, respectively, P < 0.01). Functional studies disclosed that upon oligomerization by anti-CD95 monoclonal antibodies the CD95 protein was either not able to initiate apoptosis of leukemic cells (75% of cases) or induced low rates of apoptosis (20% of cases). Only in 5% of cases did the apoptosis rate exceed the 20% level of the CD95-specific apoptosis. Most of the CD95-sensitive cases were found among T lineage ALLs (38% of T lineage vs 10% of B lineage ALLs). Overall, the extent of CD95-induced apoptosis did not correlate with the expression level of CD95. Similarly, no significant correlation between expression level and functionality of CD95 in human leukemia cell lines of B and T cell origin could be observed. Bcl-2 protein has been associated with prolonged cell survival and has been shown to block partially CD95-mediated apoptosis, but for ALL cells no correlation between bcl-2 expression and spontaneous or CD95-mediated apoptosis could be found. The results obtained in this study indicate that, despite constitutive expression of CD95, the ALL cells are mainly resistant to CD95-triggering. More detailed investigations of the molecular mechanisms involved in the intracellular apoptotic signal transduction, such as interactions of the bcl-2 and the other members of the bcl-2 family, and functionality of the interleukin-1beta converting enzyme (ICE) like-proteases, may give new insights into key events responsible for the resistance or sensitivity to the induction of apoptosis in acute leukemia.     

Immunohistochemical and mutational analysis of the p53 tumour suppressor gene and the bcl-2 oncogene in primary testicular germ cell tumours

The role of p53 in testicular germ cell tumours is still contradictory based on the finding of immunohistochemical overexpression at the protein level, but lack of mutations at the DNA level. In addition, p53 wild-type activity has been demonstrated in cell culture experiments. Overexpression of the proto-oncogene bcl-2 might block p53-induced apoptosis and might inhibit p53 functional activity. To clarify the apparent paradox with respect to p53 overexpression and lack of mutations, an immunohistochemical and mutational analysis of p53 and bcl-2 in TGCT was performed. Ten normal testes, 52 CIS and 151 clinical stage I nonseminomatous GCTs were included in our study. A commercially available anti-p53 polyclonal rabbit antibody and an anti-bcl-2-mouse monoclonal antibody were used to stain the 5pm sections. Staining was assessed by counting at least 500 cells from the area of the most intense staining in each tumour cell type, and this was scored semiquantitatively for intensity of staining on a 4 point scale. In addition, 30 primary GCTs were included in the mutational analysis: areas with p53 overexpression were identified and microdissected prior to DNA extraction. p53 exons 5-8 were amplified by polymerase chain reaction (PCR) followed by single strand conformation polymorphism analysis. Templates demonstrating band shifts on SSCP were subjected to direct DNA sequence analysis. None of the normal testes, 32/52 (62%) CIS, and 142/151 (94%) germ cell tumours exhibited p53 overexpression. p53 expression was significantly lower in mature teratomas (0.8 +/- 0.2) than in other germ cell tumour components (2.8 +/- 1.2, p > 0.001). PCR-SSCP did not reveal any missense mutations or deletions for the p53 gene. Bcl-2 protein expression was observed in none of the normal testes, in none of the CIS, and in 14/151 (9.3%) germ cell tumours. 13/14 germ cell tumours demonstrated bcl-2 expression only in the glandular and stromal elements of their teratomatous components whereas all other components were negative for bcl-2. Our results--p53 overexpression, lack of p53 mutations, undetectable bcl-2--are consistent with recent in vitro studies. High susceptibility of testicular cancer to drug-induced apoptosis appears to be the result of wild-type p53 and lack of bcl-2. Radiation and chemotherapeutic insensitivity of mature teratomas might be the result of bcl-2 overexpression and lack of p53 overexpression. Therefore, chemoresistance to DNA damaging agents might be reflected by the expression of p53 and bcl-2 and it might be useful to evaluate p53 and bcl-2 in primary tumours and metastatic lesions in order to identify patients early with primary or secondary chemoresistance.     

bcl-2 and p53 expression in resectable pancreatic adenocarcinomas: association with clinical outcome

The bcl-2 proto-oncogene and the p53 tumor suppressor gene are important determinants of tumor cell susceptibility to apoptosis. bcl-2 and mutant p53 proteins inhibit apoptosis in vitro and can provide prognostic information in certain tumor types. We analyzed bcl-2 and p53 expression in archival pancreatic (n = 35) and ampullary (n = 6) adenocarcinomas, resected for cure, and their relationship to overall survival. Patients were treated with 5-fluorouracil and irradiation either pre- (n = 21) or postoperatively (n = 15); 5 patients received surgery alone. Using specific monoclonal antibodies, cytoplasmic bcl-2 and nuclear p53 proteins were detected in 22 of 40 (55%) and 20 of 37 (54%) tumors, respectively. No relationship was found between bcl-2 and p53 expression. Neither bcl-2 nor p53 correlated with histological response to preoperative chemoradiation. Lymph node involvement predicted poor overall survival (P = 0.02). A trend toward improved survival was seen in well-differentiated (P = 0.08) tumors and in those with increased bcl-2 expression (P = 0.06). p53 expression was not related to clinical outcome. In a multivariate analysis, nodal status was the single most important predictor of overall survival. Of note, the combined variable of bcl-2 expression and histological grade was a stronger prognostic variable than nodal status alone. Unlike nodal status, these features can potentially be evaluated in preoperative biopsy specimens.     

T-cell-rich large-B-cell lymphomas contain non-activated CD8+ cytolytic T cells, show increased tumor cell apoptosis, and have lower Bcl-2 expression than diffuse large-B-cell lymphomas

The factor(s) responsible for the reduced B cell number and increased T cell infiltrate in T-cell-rich large-B-cell lymphomas (TCRBCLs) have not been well characterized. We studied 18 TCRBCLs and 12 diffuse large-B-cell lymphomas (DLBCLs) to compare the 1) predominant T cell subpopulation(s), 2) expression of cytotoxic granule proteins (TIA-1 and granzyme B), 3) level of tumor cell apoptosis (Apoptag system, Oncor, Gaithersburg, MD), and 4) expression of Ki-67 (Mib-1) and apoptosis-related proteins (fas (CD95), bcl-2, and p53). T cells in TCRBCLs and DLBCLs were predominantly CD8+ T cells expressing alphabeta T-cell receptors and TIA-1 (16 of 18 TCRBCLs with >50% TIA-1+ small lymphocytes) but lacking granzyme B (16 of 18 TCRBCLs with <25% granzyme B+ small lymphocytes). Scattered apoptotic tumor cells (confirmed with CD20 co-labeling) were present in 15 of 18 TCRBCLs, with 14 of 15 cases having <10% apoptotic cells. No apoptotic cells were seen in 12 of 12 DLBCLs. In 16 of 16 immunoreactive TCRBCLs, <25% tumor cells were bcl-2+, whereas 6 of 12 DLBCLs had >50% bcl-2+ tumor cells. CD95 (fas) expression was also lower, with 3 of 18 (16.7%) TCRBCLs versus 4 of 12 (33%) DLBCLs having >25% CD95+ tumor cells. TCRBCLs and DLBCLs had similar levels of p53 and Ki-67 (Mib-1) expression. Thus, T cells in TCRBCLs are non-activated cytotoxic T lymphocytes (TIA-1+, granzyme B-). Tumor cell apoptosis (perhaps cytotoxic T cell mediated) may partly account for the decreased number of large (neoplastic) B cells in TCRBCLs, but other factors (ie, decreased bcl-2 expression) may also be needed.     

Spontaneous programmed cell death in infiltrating duct carcinoma: association with p53, BCL-2, hormone receptors and tumor proliferation

Recent evidence has emphasized the importance of programmed cell death or apoptosis in the maintenance of tissue homeostasis and pathogenesis of tumors. This study, analyzed in breast cancer, investigates the significance of apoptosis in relation to the expression of p53 and bcl-2 proteins, tissue proliferation defined by Ki-67 expression, hormone receptors and tumor grade. The extent of apoptosis was defined by morphological criteria and the TUNEL (Tdt-mediated dUTP biotin nick end labelling) assay. Immunocytochemistry was performed for p53, bcl-2, estrogen receptor, progesterone receptor and Ki-67 expression. Mutant p53 protein was detected using a mutant specific ELISA. Immunoreactivity of p53 significantly correlated with the presence of mutant p53 protein detected by ELISA (r = 0.654, p = 0.00001). An inverse correlation was observed between bcl-2 expression and the extent of apoptosis (r = -0.33369, p = 0.01912). The extent of apoptosis directly correlated with p53 protein accumulation (r = 0.485, p = 0.00041), Ki-67 immunoreactivity (r = 0.435, p = 0.001), histopathological grade (r = 0.492, p = 0.0003), tumor size (r = 0.326, p = 0.023) and lymph node status (r = 0.287, p = 0.047). A direct correlation was also observed between p53 expression and Ki-67 immunoreactivity (r = 0.623, p = 0.0002). There was no statistically significant association between estrogen and progesterone receptor status and apoptosis. In addition, the TNM stage of the disease correlated with immunoreactivity of p53 (r = 0.572, p = 0.00012) and Ki-67 (r = 0.3744, p = 0.00818). Bcl-2, by inhibiting apoptosis, may cause a shift in tissue kinetics towards the preservation of genetically aberrant cells, thereby facilitating tumor progression. These results imply that rapidly proliferating tumors appear to have a high "cell turnover state" in which there may be an increased chance of apoptosis amongst the proliferating cells. The ability of apoptosis to also occur in the presence of mutant p53 protein suggests the existence of at least two p53-dependent apoptotic pathways, one requiring activation of specific target genes and the other independent of it.     

Activation of the K-ras oncogene in colorectal neoplasms is associated with decreased apoptosis

BACKGROUND: Recent in vitro data indicate that the oncogenic effects of activated ras genes may be mediated, at least in part, through inhibition of apoptotic cell death. To examine this proposition in vivo, the relationship between mutations of the K-ras gene and the frequency of apoptosis was studied in a series of 69 sporadic colorectal neoplasms (11 adenomas and 58 carcinomas). METHODS: Mutations in codon 12 of K-ras were determined by a single tube, enriched polymerase chain reaction. Apoptotic cells in tumor sections were identified by in situ end-labeling of fragmented DNA, whereas levels of bcl-2 and p53 proteins were determined by immunohistochemistry. RESULTS: Tumors with mutant K-ras had a significantly lower apoptotic index than those with the wild-type allele (P < 0.05). They were also more likely to exhibit positive bcl-2 staining (P < 0.05). Adenomas showed significantly greater bcl-2 positivity than carcinomas (89% and 51%, respectively; P < 0.05). The frequency of apoptosis in these tumors was not related to either bcl-2 positivity or p53 status. CONCLUSIONS: These findings suggest that activation of K-ras in colorectal carcinoma may inhibit apoptosis and thus favor tumor progression. Alternatively, this association may reflect an accumulation of K-ras mutations in cells in which normal apoptotic pathways have been impaired.     

Increased apoptosis accompanies neoplastic development in the human colorectum

A disturbance in the balance between cell proliferation and cell loss, or apoptosis, may underlie neoplastic development. Therefore, we determined spontaneous apoptotic and proliferative rates in normal, hyperplastic, adenomatous, and malignant colorectal epithelia. In paired sections, DNA strand breaks were detected using the terminal deoxynucleotidyltransferase-mediated dUTP nick-end labeling assay, and apoptotic cells were also identified in H&E-stained slides by morphological criteria. Cell proliferation, bcl-2, and p53 expression were analyzed using specific monoclonal antibodies. In normal mucosa, luminal epithelial cells demonstrated higher rates of apoptosis compared to cells in the proliferative zone. Neoplastic transformation was associated with a significant increase in rates of apoptosis and proliferation. However, apoptosis, but not proliferation, decreased at the adenoma-to-carcinoma transition coincident with expression of mutant p53. In carcinomas, both mutant p53 and bcl-2 protein levels were associated with attenuated apoptotic rates. In conclusion, apoptosis is an important regulator of growth in normal and neoplastic colorectal epithelia. Increased apoptosis and proliferation accompany neoplastic transformation, suggesting that an alteration in apoptotic rates is an important event in colorectal carcinogenesis. Furthermore, the imbalance in these processes found in carcinomas may facilitate tumor growth and progression.     

Differential regulation of P53 and Bcl-2 expression by ultraviolet A and B

The induction of apoptosis by ultraviolet (UV) radiation and other DNA damaging agents plays a critical role in monitoring the accumulation of genetic damage and the suppression of tumor development. We hypothesize that UVA and UVB induce apoptosis by modulating balances between p53 and/or bcl-2 genes. Using MCF-7 cells that express both wild-type P53 and Bcl-2 proteins, we demonstrated that UVA and UVB induced apoptosis through regulating expression of apoptosis promoting or inhibiting genes. UVA induced immediate apoptosis and downregulated bcl-2 expression. Bcl-2 expression was reduced by approximately 40% at 4 h post-150 kJ UVA irradiation per m2 with a maximum downregulation (over 70%) at 24 h. The dose-response studies revealed that significant reduction of bcl-2 expression was observed at UVA doses ranging from 50 to 200 kJ per m2; however, p53 levels were not affected by UVA. In contrast, UVB exhibited a entirely different action than UVA in that UVB substantially induced p53 expression, but had no effect on bcl-2 expression. The induction of P53 by UVB was dose and time dependent with the maximum expression at 24 h post-2 and post-4 kJ UVB irradiation per m2. Down-regulation of bcl-2 and fragmentation of DNA induced by UVA occurred earlier (approximately at 4 h) than upregulation of p53 and DNA fragmentation by UVB (12-24 h). These results suggest that UVA and UVB cause cell damage through different mechanisms and that the balances between the expression of p53 and bcl-2 may play an important role in regulating the apoptosis induced by UV irradiation.     

HIDA kinetics in children

We have investigated the immunohistochemical expression of p53, mdm2, p21/waf1 and bcl-2 proteins in 31 thymic epithelial tumours comprising five medullary thymomas (MDT), four mixed thymomas (MT), 12 cortical thymomas (CT), eight predominately cortical thymomas (PCT) and two well-differentiated thymic carcinomas (WDTC). We have found p53, mdm2, p21 and bcl-2 protein expression in 25/31, 8/31, 5/31 and 10/31 thymic epithelial tumours, respectively. Coexpression of p53 and mdm2 proteins was found in eight cases (three CT, four PCT and one WDTC). Five of them were also p21 positive and three p21 negative. Discordant p53+/mdm2-/p21- protein expression was found in 19 cases (three MDT, three MT, nine CT, three PCT and one WDTC). Mdm2 and p21 proteins were not expressed in the absence of p53 protein. Coexpression of bcl-2 and p53 proteins was found in seven cases (three MDT, three MT and one WDTC). Eighteen cases were p53+/bcl-2- (10 CT, seven PCT and one WDTC) and three cases (two MDT and one MT) were bcl-2+/p53-. Our findings indicate that in thymomas, p53 expression is more frequently associated with cortical histotypes while bcl-2 expression is strongly associated with medullary and mixed histotypes. In addition, there is an inverse correlation between p53 and bcl-2 protein expression in thymomas. Coexpression of p53/mdm2/p21 proteins may reflect thymomas with wild-type (wt), p53 gene since mdm2 and p21 proteins are inducible by wt p53 gene. However, in view of previous findings that p53 mutation is an early event in thymomas, the possibility of p53 gene mutation with p53-independent mdm2 and p21 expression should be considered in these cases. Discordant p53+/mdm2-/p21- protein expression may represent thymomas with p53 gene mutations unable to activate expression of mdm2 and p21 proteins.     

Ochratoxin A disturbs pH homeostasis in the kidney: increases in pH and HCO3- in the tubules and vasa recta

The aim of this study was to ascertain whether apoptotic counts have prognostic significance in colorectal cancer and if such counts are related to the expression of proteins implicated in cell cycle regulation. Material from a cohort of patients aged 45 years or less with colorectal carcinoma was re-examined to determine apoptotic and mitotic counts by light microscopy, in addition to assessing p53, c-myc, and bcl-2 protein status by immunohistochemistry. The apoptotic index in the 74 patients who were alive or who had died of colorectal carcinoma ranged from 1.2 per cent to 12.3 per cent and exhibited independent prognostic significance, with high counts predicting better survival (P = 0.02). Mitotic counts were not related to survival, despite a close correlation with apoptosis (r = 0.85). Tumours regarded as not staining with the CM1 antibody for p53 protein demonstrated higher apoptotic counts, compared with those that stained (medians 5.2 and 4.0 per cent, respectively; P = 0.03), but p53 expression was found not to be related to survival. The 68 tumours which stained for c-myc appeared to exhibit higher mitotic counts than those that did not. bcl-2 was detected in only four tumours. The latter two proteins exhibited no apparent relationship to the apoptotic index or survival. Although these results indicate a potential role for apoptotic counting in prognostic prediction in colorectal tumours, this is an uncommon group of patients who exhibited some atypical features. The likelihood of a proportion of cases arising within hereditary non-polyposis colorectal cancer syndrome may limit the application of the findings to a more general population with cancer of the colon and rectum. Further work is required, including critical measurement of reproducibility and assessment of the relative impact of this parameter compared with 'traditional' prognostic markers.     

Selective activation of rolipram-sensitive, cAMP-specific phosphodiesterase isoforms by phosphatidic acid

BACKGROUND: Regulatory coupling of cell proliferation and apoptosis is suggested by recent findings with regard to certain tumors, such as the finding of tumor resistance to anticancer therapy caused by inhibition of apoptosis. The processes leading to apoptosis appear to be regulated by a variety of oncogenes and tumor suppressor genes. In the current study, the relation between apoptosis and expression of retinoblastoma protein (pRB) was assessed in 50 primary anaplastic astrocytomas (AAs) and 46 recurrent tumors in the same patients as the primary tumors after macroscopic total surgical resection and chemoradiotherapy. METHODS: Apoptotic cells were identified by the in situ 3'-end labeling technique. Proliferative potential, pRB expression, and p53 expression were evaluated immunohistochemically using anti-Ki-67 (MIB-1), anti-pRB, and anti-p53 antibodies, respectively. The prognostic value of these biologic markers in AA patients undergoing treatment was also evaluated. RESULTS: The mean apoptotic index (AI) was 0.91 +/- 0.70% for specimens obtained at the initial surgery and 2.32 +/- 1.71% for those obtained at recurrence. There was no apparent correlation between the AI and the MIB-1 staining index (MI) in primary AAs, whereas significantly higher AI and MI were observed in recurrent pRB negative cases than in their pRB positive counterparts. The survival of patients with AAs showing a high MI and negative pRB immunostaining was significantly shorter than in the other cases. Neither the size of the apoptotic fraction nor the p53 expression in primary tumor correlated with the overall survival. CONCLUSIONS: The clinical outcome of patients with AA may be associated with aberrant pRB function and increased proliferative activity rather than an inability of tumor cells to undergo apoptosis.     

Prognostic value of bcl-2 oncoprotein expression in stage II colon carcinoma

The bcl-2 proto-oncogene encodes a Mr 25,000 protein that has been shown to prevent apoptosis or programmed cell death. The bcl-2 protein is detectable in basal cells of normal colonic epithelium, and an altered topographic distribution of this protein is found in colonic neoplasms. However, the clinical significance of abnormal bcl-2 expression in colon carcinomas remains unknown. We examined the prognostic value of the bcl-2 protein in TNM stage II colon carcinomas and its relationship to DNA ploidy, cell proliferation indices, p53 expression, and clinicopathological features. We analyzed 119 resected and otherwise untreated, paraffin-embedded stage II colon carcinomas for bcl-2 and p53 protein expression using immunohistochemistry. DNA ploidy and proliferative index (% S-phase + % G2-M) were determined by flow cytometry, and tumor grade and vascular microinvasion were assessed on histological sections. Cytoplasmic expression of the bcl-2 protein was detected in 72 (66%) of 110 carcinomas, and a high level of expression was significantly correlated with diploid DNA content (P = 0.02) and low proliferative activity (P = 0.005). bcl-2 was not associated with nuclear p53 expression. In a univariate analysis, a higher fraction of bcl-2-positive tumor cells was associated with better relapse-free survival (P = 0.02) and overall survival (P = 0.05) rates. Moreover, a high level of bcl-2 expression was an independent predictor of better relapse-free survival (P = 0.04), but not overall survival (P = 0.14), after adjustment for other variables, including proliferative index, DNA ploidy, and race. In conclusion, bcl-2 overexpression is associated with favorable prognostic features and may predict clinical outcome in stage II colon carcinomas.