Immunohistochemical expression of bcl-2 and p53 oncoproteins: correlation with Ki67 proliferation index and prognostic histopathologic parameters in colorectal neoplasia

Prognostic Biomarkers of Cell Proliferation in Colorectal Cancer (CRC): From Immunohistochemistry to Molecular Biology Techniques

Colorectal cancer (CRC) is one of the most common and severe malignancies worldwide. Recent advances in diagnostic methods allow for more accurate identification and detection of several molecular biomarkers associated with this cancer. Nonetheless, non-invasive and effective prognostic and predictive testing in CRC patients remains challenging. Classical prognostic genetic markers comprise mutations in several genes (e.g., APC, KRAS/BRAF, TGF-β, and TP53). Furthermore, CIN and MSI serve as chromosomal markers, while epigenetic markers include CIMP and many other candidates such as SERP, p14, p16, LINE-1, and RASSF1A. The number of proliferation-related long non-coding RNAs (e.g., SNHG1, SNHG6, MALAT-1, CRNDE) and microRNAs (e.g., miR-20a, miR-21, miR-143, miR-145, miR-181a/b) that could serve as potential CRC markers has also steadily increased in recent years. Among the immunohistochemical (IHC) proliferative markers, the prognostic value regarding the patients' overall survival (OS) or disease-free survival (DFS) has been confirmed for thymidylate synthase (TS), cyclin B1, cyclin D1, proliferating cell nuclear antigen (PCNA), and Ki-67. In most cases, the overexpression of these markers in tissues was related to worse OS and DFS. However, slowly proliferating cells should also be considered in CRC therapy (especially radiotherapy) as they could represent a reservoir from which cells are recruited to replenish the rapidly proliferating population in response to cell-damaging factors. Considering the above, the aim of this article is to review the most common proliferative markers assessed using various methods including IHC and selected molecular biology techniques (e.g., qRT-PCR, in situ hybridization, RNA/DNA sequencing, next-generation sequencing) as prognostic and predictive markers in CRC.

Mechanism of Apoptosis Induced by Curcumin in Colorectal Cancer

Colorectal cancer (CRC) is among the top three cancer with higher incident and mortality rate worldwide. It is estimated that about over than 1.1 million of death and 2.2 million new cases by the year 2030. The current treatment modalities with the usage of chemo drugs such as FOLFOX and FOLFIRI, surgery and radiotherapy, which are usually accompanied with major side effects, are rarely cured along with poor survival rate and at higher recurrence outcome. This trigger the needs of exploring new natural compounds with anti-cancer properties which possess fewer side effects. Curcumin, a common spice used in ancient medicine was found to induce apoptosis by targeting various molecules and signaling pathways involved in CRC. Disruption of the homeostatic balance between cell proliferation and apoptosis could be one of the promoting factors in colorectal cancer progression. In this review, we describe the current knowledge of apoptosis regulation by curcumin in CRC with regard to molecular targets and associated signaling pathways.

Expression and clinicopathologic significance of TUFM and p53 for the normal-adenoma-carcinoma sequence in colorectal epithelia

BACKGROUND

Evidence indicates that most cases of colorectal carcinoma (CRC) develop from adenoma. A previous study demonstrated that mitochondrial Tu translation elongation factor (TUFM) might serve as an independent prognostic factor for colorectal cancer. However, the expression and function of TUFM in the normal-adenoma-cancer sequence have not been reported. In this study, we investigated the clinicopathologic significance of TUFM and p53 expression for the normal-adenoma-carcinoma sequence in colorectal epithelia and evaluated the roles of TUFM during the progression of colorectal tumors.

METHODS

Paraffin-embedded specimens from 261 colorectal normal mucosa samples, 157 adenomas, and 104 early carcinomas were analyzed for TUFM and p53 expression by immunohistochemistry.

RESULTS

Expression of TUFM and p53 was significantly increased during the colorectal normal-adenoma-carcinoma sequence (all P < 0.05). The expression of TUFM and p53 was associated with histologic type of adenomas (P = 0.028; P = 0.001) and grade of dysplasia (all P = 0.001). Expression of TUFM was positively correlated with that of p53 (r = 0.319, P = 0.001).

CONCLUSIONS

Upregulated TUFM expression may play an important role in the transformation from colorectal normal mucosa to carcinoma through adenoma. Combined immunohistochemical detection of TUFM and p53 may be useful for evaluating the biological behavior of colorectal adenoma.

Dietary cocoa inhibits colitis associated cancer: a crucial involvement of the IL-6/STAT3 pathway

Patients with inflammatory bowel disease (IBD) are at increased risk for developing ulcerative colitis-associated colorectal cancer (CRC). The interleukin-6 (IL-6)/signal transducer and activator of transcription (STAT)-3 signaling regulates survival and proliferation of intestinal epithelial cells and play an important role in the pathogenesis of IBD and CRC. Cocoa is enriched with polyphenols that known to possess antioxidant, anti-inflammatory and antitumor activities. Here, we explored the antitumor effects and mechanisms of cocoa diet on colitis-associated cancer (CAC) using the azoxymethane/dextran sulfate sodium model, with a particular focus on whether cocoa exerts its anticancer effect through the IL-6/STAT3 pathway. We found that cocoa significantly decreased the tumor incidence and size in CAC-induced mice. In addition to inhibiting proliferation of tumor epithelial cells, cocoa suppressed colonic IL-6 expression and subsequently activation of STAT3. Thus, our findings demonstrated that cocoa diet suppresses CAC tumorigenesis, and its antitumor effect is partly mediated by limiting IL-6/STAT3 activation. In addition, cocoa induces apoptosis by increased the expressions of Bax and caspase 3 and decreased Bcl-xl. Thus, we conclude that cocoa may be a potential agent in the prevention and treatment of CAC.

The potential of carcinoembryonic antigen, p53, Ki-67 and glutathion Stransferase-π as clinico-histopathological markers for colorectal cancer

Objective

Colorectal cancer is one of the major contributors to cancer death worldwide. Lack of reliable colorectal cancer markers has hampered the management of these cancer patients. Our main purpose was to study the correlation between histopathological variables of colorectal adenocarcinomas and identify histopathological markers that are of prognostic value in patients with colorectal cancer.

Methods

In the present study, we examined the expression of carcinoembryonic antigen (CEA), p53, Ki-67 and glutathion Stransferase (GST) -π by using immunohistochemical staining methods in 126 colorectal carcinoma patients and evaluated the lymph node metastasis status in these patients by histopathological examination.

Results

The positive rates of CEA, p53, Ki-67 and GST-π expression in the colorectal cancer tissue specimens examined were 95.23%, 55.56%, 53.38% and 82.30%, respectively. Expression of p53 and Ki-67 was significantly correlated with the Dukes stages of the tumor, with higher levels of these proteins in Dukes'C and D tumors than those in Dukes' A and B tumors. Furthermore, the expression of p53, GST-π and Ki-67 correlated with prognosis of patients with colorectal cancer. Additionally, the expression of p53 in colorectal cancer was closely related to the expression of Ki-67 and the expression of GST-π was directly correlated with that of p53.

Conclusion

The expression of CEA, p53, Ki-67 and GST-π was correlated with various clinical features of patients with colorectal cancer. The combined use of these histopathological markers appeared to be a promising tool in predicting the prognosis of patients with this type of cancer.

Expression Profiling of Proliferation and Apoptotic Markers along the Adenoma-Carcinoma Sequence in Familial Adenomatous Polyposis Patients

Introduction. Familial adenomatous polyposis (FAP) patients have a germline mutation in the adenomatous polyposis coli (APC) gene. The APC protein interacts with beta-catenin, resulting in the activation of the Wnt signalling pathway. This results in alterations in cell proliferation and apoptosis. We investigated the expression of beta-catenin and related proliferation and apoptotic factors in FAP patients, exploring the expression along the adenoma-carcinoma sequence. Methods. The expression of beta-catenin, p53, bcl-2, cyclin-D1, caspase-3, CD10, and Ki-67 proteins was studied by immunohistochemistry in samples of colonic nonneoplastic mucosa (n = 71), adenomas (n = 152), and adenocarcinomas (n = 19) from each of the16 FAP patients. Results. The expression of beta-catenin, caspase-3, cyclin-D1, and Ki-67 was increased in both adenomas and carcinomas in FAP patients, compared with normal mucosa. p53 and CD10 expression was only slightly increased in adenomas, but more frequently expressed in carcinomas. Bcl-2 expression was increased in adenomas, but decreased in carcinomas. Conclusion. This is the first study investigating collectively the expression of these molecules together in nonneoplastic mucosa, adenomas, and carcinomas from FAP patients. We find that beta-catenin and related proliferative and apoptotic factors (cyclin-D1, bcl-2, caspase-3, and Ki-67) are expressed early in the sequence, in adenomas. However, p53 and CD10 are often expressed later in the sequence, in carcinomas.

Chicken skin mucosa surrounding adult colorectal adenomas is a risk factor for carcinogenesis

OBJECTIVES

Transformation of normal mucosa to colorectal adenoma could occur over a span of 5 to 20 years, whereas transformation of colorectal adenoma to colorectal cancer could take an additional 5 to 15 years. This study aims to investigate whether chicken skin mucosa (CSM) surrounding adult colorectal adenomas may be a risk factor for carcinogenesis.

METHODS

Patients with colorectal mucosa, colorectal adenomas without CSM, or colorectal adenomas with CSM were enrolled in this study. Immunohistochemistry and enzyme-linked immunosorbent assays were used to determine the expression levels of proliferation markers (ki-67 and COX-2) and apoptosis factors (survivin and caspase-3) in tissues.

RESULTS

The expression of ki-67 was significantly higher in colorectal adenomas with CSM compared with colorectal adenoma tissues (P < 0.01). Colorectal adenocarcinoma showed significantly higher levels of COX-2 protein compared with normal colorectal mucosa and colorectal adenoma tissues (P < 0.001). COX-2 expression was significantly higher in adenomas with CSM compared with normal colorectal mucosa (P < 0.001). Adenomas with CSM and adenocarcinomas exhibited significantly higher levels of survivin when compared with colorectal adenoma without CSM and normal tissues (P < 0.001). Although we found no significant difference in caspase-3 levels between adenocarcinomas and adenomas with CSM, caspase-3 expression was significantly lower in these tissues when compared with colorectal adenomas without CSM and normal mucosa (P < 0.001).

CONCLUSIONS

The biological characteristics of colorectal adenomas with CSM were different from those of colorectal adenomas without CSM. Colorectal adenomas with CSM exhibited active cell proliferation and inhibition of apoptotic pathways, suggesting an increased risk of carcinogenesis in these adenomas.

Meta-analysis of histopathological features of primary colorectal cancers that predict lymph node metastases

BACKGROUND

Treatment decisions for colorectal cancer vary based on lymph node status. While some histopathological features of the primary tumor correlate with lymph node spread, the relative influences of these risk factors are not well quantified.

OBJECTIVE

This study aims to systematically review published studies relating histopathological features of primary colorectal cancer to the presence of lymph node metastases and to determine how reliable certain factors might be at predicting nodal metastasis when only the primary lesion is available for study.

DATA SOURCES

Inclusive literature search using EMBASE and Ovid MEDLINE databases plus manual reference checks of all articles correlating lymphatic spread with colorectal cancer (any T stage) from 1984 to mid-2008 was performed.

STUDY SELECTION

This search generated two levels of screening utilized on 602 citations, yielding 123 articles for full review. Data reported from 76 articles were chosen.

MAIN OUTCOME MEASURES

The relative influence of each histopathological feature on the likelihood of lymphatic metastases was determined. Fixed-effects meta-analysis was performed, and results were reported as Mantel-Haenszel odds ratios (OR).

RESULTS

Of 42 histopathological features analyzed, only 40.4% were reported in >2 articles. The positive predictive values for the top quartile of most frequently reported risk factors were 25.5-86.4%. Among the commonly reported histopathological findings, lymphatic invasion (OR, 8.62) significantly outperformed tumor depth (T2 vs. T1; OR, 2.62) and overall differentiation (OR, 2.38) in predicting nodal spread. For the rectal cancer subset, risk factors differed from the overall colorectal group in predictive ability; poor differentiation at the invasive front (OR, 6.08) and tumor budding (OR, 5.82) were the most predictive.

LIMITATIONS

This literature search is limited by the small number of studies examining only rectal cancers and the potential changes in histological and/or surgical techniques over the study period.

CONCLUSIONS

No single histopathological feature of colorectal cancer reliably predicted lymph node metastases. Several risk factors that correlate highly with nodal disease are not routine components of standard pathology reports. Until further research establishes histopathological or molecular patterns for predicting lymph node spread, caution should be exercised when basing treatment decisions solely on these factors.

Analysis of the immunohistochemical expressions of p53, bcl-2 and Ki-67 in colorectal adenocarcinoma and their correlations with the prognostic factors

CONTEXT

Search of tumors markers that allow treatment with higher survival rates, and indicate the response to treatment and recurrence of cancer

OBJECTIVE

To analyze the immunoexpression of the proteins p53, bcl-2 and Ki-67 in colorectal adenocarcinoma and correlate them with the clinical-pathological prognostic factors.

METHOD

Tissue microarray paraffin blocks were made from colorectal adenocarcinoma tissue resected from 82 patients who had undergone surgery but not chemotherapy or radiotherapy, at "Hospital São Paulo", São Paulo, SP, Brazil, between 2002 and 2005. Thin sections (4 microm) were subjected to immunohistochemical reactions, and immunoexpression staining scores were obtained. The scores were correlated with the degree of cell differentiation, staging, disease-free interval, recurrence, survival and specific mortality. The study variables were analyzed using the chi-square and Kaplan-Meier tests to investigate associations with the markers. The significance of the differences between the curves of the disease-free interval and survival was analyzed using the Logrank and Wilcoxon tests.

RESULTS

The immunohistochemical expression of p53 was positive in 70 tumors (85.4%) and negative in 12 (14.6%). The expression of bcl-2 was positive in 26 (31.7%) and negative in 56 (68.3%). The expression of Ki-67 was positive in 62 (75.6%) and negative in 20 (24.4%). There was no statistically significant correlation between the expressions of these markers separately or in conjunction, in relation to the degree of cell differentiation, staging, disease-free interval, survival and specific mortality. In relation to recurrence, there was a statistically significant correlation with positive expression of Ki-67 (P = 0.035).

CONCLUSION

The immunohistochemical expression of Ki-67 in colorectal cancer is associated with recurrence of this disease.

Antiangiogenic effect of TW37, a small-molecule inhibitor of Bcl-2

Bcl-2 is an antiapoptotic protein that is up-regulated in several tumor types, and its expression levels have strong correlation to development of resistance to therapy and poor prognosis. We have shown recently that Bcl-2 also functions as a proangiogenic signaling molecule that activates a nuclear factor-kappaB-mediated pathway resulting in up-regulation of the angiogenic chemokines CXCL1 and CXCL8 by neovascular endothelial cells. Here, we evaluate the antiangiogenic effect of the novel small-molecule inhibitor of Bcl-2 (TW37) developed using a structure-based design strategy. We observed that TW37 has an IC(50) of 1.8 mumol/L for endothelial cells but showed no cytotoxic effects for fibroblasts at concentrations up to 50 mumol/L. The mechanism of TW37-induced endothelial cell death was apoptosis, in a process mediated by mitochondrial depolarization and activation of caspase-9 and caspase-3. The effect of TW37 on endothelial cell apoptosis was not prevented by coexposure to the growth factor milieu secreted by tumor cells. Inhibition of the angiogenic potential of endothelial cells (i.e., migration and capillary sprouting assays) and expression of the angiogenic chemokines CXCL1 and CXCL8 were accomplished at subapoptotic TW37 concentrations (0.005-0.05 micromol/L). Notably, administration of TW37 i.v. resulted in a decrease in the density of functional human microvessels in the severe combined immunodeficient mouse model of human angiogenesis. In conclusion, we describe functionally separate proapoptotic and antiangiogenic mechanisms for a small-molecule inhibitor of Bcl-2 and show the potential for Bcl-2 inhibition as a target for antiangiogenic therapy.

Transforming growth factor beta 1 and metalloproteinase-9 overexpression in colorectal cancer (CC) and adenoma

BACKGROUND AND AIMS

Although the role of transforming growth factor beta (TGFbeta) 1 and metalloproteinase-9 (MMP-9) is well documented in colorectal cancer (CC), there is a little evidence supporting its role in early carcinogenesis. The aim of the study was to determine the pattern of immunohistochemical expression of TGFbeta1, MMP-9, and Ki-67 in CC and adenomatous polyps.

PATIENT/METHODS

The study group comprised 50 patients with colorectal polyps and 33 patients with CC. Endoscopically removed polyps and CC biopsies had been evaluated with histopatologic examination and immunohistochemistry. The biopsies from 30 healthy objects served as a control group. For all antibodies labeling indices (LI) had been calculated.

RESULTS

Among 62 adenomas, 33 high-grade dysplasia (HGD) and 29 low-grade dysplasia (LGD) had been detected. Mean TGFbeta1, MMP-9, and Ki-67 LI in CC were significantly higher (p < 0.01, 0.01, and 0.01, respectively) than in HGD polyps. Mean TGFbeta1, MMP-9, and Ki-67 LI in HGD polyps were significantly higher than in LGD polyps (p < 0.01, 0.01, and 0.01, respectively). There had been no statistical difference in TGFbeta1, MMP-9, and Ki-67 LI between LGD and the control group (p > 0.05, 0.05, and 0.05, respectively). There was a positive correlation between TGFbeta1 and MMP-9 (r = 0.898), Ki-67 and MMP-9 (r = 0.938), and TGFbeta1 and Ki-67 (r = 0.913). We did not observe any correlation between TGFbeta1, MMP-9, Ki-67 LI and the clinical parameters evaluated.

CONCLUSION

The increased expression of TGFbeta1, MMP-9 observed in colorectal adenomas seems to be related to the grade of dysplasia. We assume that overexpression of TGFbeta1, MMP-9 represent an early event in colorectal carcinogenesis and may possibly have the prognostic value.

TUNEL - an efficient prognosis predictor of salivary malignancies

Biological markers are necessary for predicting prognosis of salivary malignancies and better understanding the pathogenesis of salivary cancer. We analysed terminal deoxynucleotidyl transferase (TdT)-mediated biotinylated deoxyuridine-triphosphate (dUTP)-biotin nick-end labelling (TUNEL), p53 and Ki67 expression in 66 patients with malignant salivary tumours by immonohistochemistry, and correlated the data with survival, disease-free survival, tumour grade, stage, and local and distant metastasis. TUNEL efficiently predicted poor prognosis in salivary malignancies. The 5-year (5Y) survival probability dropped significantly with the level of TUNEL staining (from 83% in negatively stained tumours to 57 and 24% in TUNEL positively stained levels 1 and 2, respectively), (P=0.042). Extensive Ki67 staining (in addition to TUNEL) reduced the 5Y-survival rate even further and addition of positively stained p53 dropped the 5Y-survival rate to 0. The correlation rates between TUNEL and Ki67 was 58% (P=0.0001), and between TUNEL and p53 it was 50% (P=0.035). Concurrently, TUNEL correlated with metastasis, extracapsular spread, grade and stage. The correlation between TUNEL, p53 and Ki67 staining and survival probabilities, and the pathological grade, stage and metastasis spread of salivary malignancies makes this a highly effective tool in patient follow-up and prognosis.

Colon cancer and apoptosis

BACKGROUND

The implementation of new therapeutic options for the management of metastatic colon cancer mandates a revisit to apoptosis and its role in colon cancer tumorigenesis with an emphasis on the mechanisms leading to chemotherapeutic resistance and immune system evasion of colon cancer cells.

DATA SOURCES

Literature regarding molecular apoptosis mechanisms and the role of apoptosis in colon cancer progression are reviewed by this article.

CONCLUSION

Programmed cell death has rapidly emerged as a potential target for cancer treatment at various stages of tumor progression. Chemoprevention, immuno-regulation, and metastasis are prospective targets by which apoptotic mechanisms could be utilized in the prevention and management of tumorigenesis. Understanding how defects in the death receptor pathway of apoptosis permit colon cancer cells to escape the immune system would allow for treatment options whereby the body's immune system could again recognize and eliminate unwanted cells.

Evidence that the p53 negative / Bcl-2 positive phenotype is an independent indicator of good prognosis in colorectal cancer: a tissue microarray study of 460 patients

BACKGROUND

Advances in our understanding of the molecular biology of colorectal cancer have fuelled the search for novel molecular prognostic markers to complement existing staging systems. Markers assessed in combination may perform better than those considered individually. Using high-throughput tissue microarray technology, we describe the prognostic value of combined p53 / Bcl-2 status in colorectal cancer.

PATIENTS AND METHODS

Tumour samples from 462 patients who underwent elective surgery to resect a primary colorectal cancer between 1994 and 2000 (mean follow-up of 75 months) were assembled in tissue microarray format. Clinico-pathological data including tumour grade, stage, vascular invasion status along with disease specific survival data has been collected prospectively. Immunohistochemical analysis of p53 and Bcl-2 expression was performed using antibodies DO-7 (p53) and 124 (Bcl-2), and results correlated with known clinico-pathological variables and outcomes.

RESULTS

Abnormal nuclear p53 accumulation and Bcl-2 overexpression were detected in 221/445 (49.6%) and199/437 (45.5%) tumours respectively, with a significant inverse correlation between the two markers (p = 0.023). On univariate analysis no correlations were found between either marker and standard clinico-pathological variables, however nuclear p53 expression was associated with a significantly reduced survival (p = 0.024). Combined analysis of the two markers indicated that 112/432 (24.2%) cases displayed a p53(-)/Bcl-2(+) phenotype, this occurring more frequently in earlier stage tumours. Kaplan-Meier analysis revealed a significant survival advantage in these p53(-)/Bcl-2(+) tumours compared with the remaining cases (p = 0.0032). On multivariate analysis using the Cox proportional hazards model, neither p53 expression nor Bcl-2 expression alone were of independent prognostic significance, however the combined p53(-)/Bcl-2(+) phenotype was significantly associated with a good prognosis in this series (HR 0.659, 95%CI 0.452-0.959, p = 0.029).

CONCLUSION

Patient stratification by combined p53 / Bcl-2 phenotype provides stage-independent prognostic information in colorectal cancer. Specifically, that up to a quarter of patients display a good prognosis p53(-)/Bcl-2(+) phenotype. This may indicate a more clinically indolent phenotype and a subset of patients for whom less aggressive adjuvant treatment appropriate.

Quantitative study of multiple biomarkers of colorectal tumor with diagnostic discrimination model

AIM: To evaluate the multiple biomarkers of colorectal tumor and their potential usage in early diagnosis of colorectal cancers.

METHODS: Multiple biomarkers (DNA contents, AgNOR, PCNA, p53, c-erbB-2) in 10 normal colorectal mucosae, 37 colorectal adenomas and 55 colorectal cancers were analyzed quantitatively in the computed processing imaging system. Discrimination patterns were employed to evaluate the significance of single and multiple indices in diagnosis of colorectal cancers.

RESULTS: The mean values of the analyzed parameters increased in order of the normal mucosa, adenoma and adenocarcinoma, and this tendency reflected the progression of colorectal malignancy. The parameters including DNA index, positive rates, densities of AgNOR, c-erbB-2, and p53, shape and density of nucleus were relatively valuable for diagnoses. Then a diagnostic discrimination model was established. The samples were confirmed with the model, the sensitivity rates in cancer group and adenoma group were 96.36% and 89.19%, respectively. The value of proliferating cell nuclear antigen (PCNA) in early diagnosis of colorectal cancers was uncertain.

CONCLUSION: The quantitative evaluation of some parameters for colorectal tumor can provide reproducible data for differential diagnosis. The established diagnostic discrimination model may be of clinicopathological value, and can make the early diagnosis of colorectal cancer possible.

Enhanced oxaliplatin-induced apoptosis following antisense Bcl-xl down-regulation is p53 and Bax dependent: Genetic evidence for specificity of the antisense effect

Introduction: Oxaliplatin, licensed for colorectal cancer chemotherapy, damages DNA by generating intrastrand and interstrand cross-links and can induce apoptosis via a Bax-dependent pathway. Bcl-xl, an antiapoptotic Bcl-2 family member, regulates apoptosis and chemoresistance in several cancer models. Bcl-xl expression correlates with invasiveness in primary colorectal cancer. Bcl-xl may therefore represent a therapeutic target in this disease. We used the mismatch repair-deficient HCT116 colorectal cancer cell line (wild-type HCT116) and p53 null, Bax null, or p21/WAF1 null derivatives to identify genetic determinants of the response to oxaliplatin and tested the hypothesis that antisense-mediated Bcl-xl down-regulation would enhance the apoptotic response in a p53- or Bax-dependent manner. Results: At clinically relevant concentrations, oxaliplatin induced p53 and p53-dependent Bax, Bcl-xl, and p21/WAF1 protein accumulation. A minor degree of apoptosis resulted via a p53- and Bax-dependent pathway. The major response was a transient mixed G1 and G2 growth arrest. The G1 arrest was p53 and p21/WAF1 dependent. A 2′-O-ribose methoxyethyl phosphorothioate antisense oligonucleotide reduced Bcl-xl protein expression by ∼90% in HCT116 (Bcl-xl knockdown). Missense controls were inactive. Prior Bcl-xl knockdown enhanced the apoptotic and the global cytotoxic effect of oxaliplatin. The extent of enhancement of apoptosis depended on the integrity of the p53- and Bax-mediated apoptotic pathway, providing genetic evidence that the desired proapoptotic antisense effect is due to specific down-regulation of the Bcl-xl target. Conclusion: The combination of oxaliplatin and Bcl-xl antisense merits testing in models of colorectal cancer in vivo.

p53 in nonneoplastic central nervous system lesions: an immunohistochemical and genetic sequencing study

OBJECTIVE

Immunostaining for p53 commonly is considered a marker of neoplasia. Previous studies of nonneoplastic processes have yielded conflicting results.

METHODS

To test the assumption that p53 immunoreactivity indicates neoplasia, we examined 60 formalin-fixed, paraffin-embedded biopsies of nonneoplastic central nervous system lesions, including gliosis (n = 12), infarction (n = 9), demyelinating disease (n = 23), progressive multifocal leukoencephalopathy (n = 11), and herpes simplex virus encephalitis (n = 5). Diffuse astrocytomas (n = 50) of World Health Organization Grades 2 to 4 also were studied, as were six control autopsy brains. The avidin-biotin-peroxidase complex method was used with commercially available monoclonal antisera to both p53 (clone DO7; Dako, Carpinteria, CA) and mdm2 (Dako), a protein known to stabilize p53. Two samples of each nonneoplastic lesion also were subjected to deoxyribonucleic acid isolation, amplification, and sequencing of exons 5 to 8 of TP53.

RESULTS

Although it was low level in most instances, p53 immunoreactivity was noted in all but normal control samples. In reactive lesions, staining was largely observed in astrocytes and histiocytes. Scant oligodendroglia also were labeled in demyelinating disease. The progressive multifocal leukoencephalopathy samples revealed exceptionally strong staining in astrocytes and infected oligodendrocytes. Staining also was noted in occasional endothelial cells and neurons, and in rare lymphocytes. Immunoreactivity for mdm2, studied only in nonneoplastic lesions, was moderate to strong in all cases and limited to reactive astrocytes and histiocytes. No TP53 mutations were noted in the nonneoplastic lesions studied. To some extent, all astrocytomas exhibited p53 immunopositivity, particularly high-grade lesions.

CONCLUSION

p53 immunoreactivity is not limited to astrocytomas, but it can be observed in lesions that often are mistaken for glioma. No TP53 mutations accompany p53 expression in nonneoplastic lesions, and mdm2 may be responsible for persistence of p53 expression in these processes.