IMMUNOHISTOCHEMICAL ANALYSIS OF p53 AND PROLIFERATING CELL NUCLEAR ANTIGEN (PCNA) IN BLADDER CANCER: POSITIVE IMMUNOSTAINING AND RADIOSENSITIVITY

Altered p53/p16 expression is linked to urothelial carcinoma progression but largely unrelated to prognosis in muscle-invasive tumors

BACKGROUND

Most inactivating p53 mutations result in a nuclear p53 accumulation - detectable by immunohistochemistry (IHC). p53 alterations leading to a complete lack of p53 protein and absence of immunostaining do also occur - not easily detectable by IHC. p16 is upregulated in p53 inactivated cells. We hypothesized that a positive p16 IHC may help to distinguish p53 inactivation in IHC negative cases.

MATERIAL AND METHODS

We investigated p53 and p16 immunostaining on 2710 urothelial bladder carcinomas in a tissue microarray format to understand their impact in relation to clinicopathological parameters of disease progression and patient outcome.

RESULTS

p16 immunostaining was absent in normal urothelium but occurred in 63.5% (30.4% strong) of cancers. p16 strongly positive cases increased from pTaG2 low-grade (9.6%) to pTaG3 high-grade tumors (46.5%, p < .0001) but decreased from pTaG3 to pT4 (33.3%; p = .0030). Among pT2-4 carcinomas, p16 positivity was linked to high-grade (p = .0005) but unrelated to overall survival. p53 staining was negative in 8.4%, very weak in 15.4%, weak in 55.3%, strong in 4.7%, and very strong in 16.2% cancers. p53 negative (potentially p53 null phenotype), strong, and very strong p53 positivity increased from pTaG2 low-grade to pTaG3 high-grade tumors (p < .0001) and from pTaG3 to pT2-4 cancers (p = .0007). p53 staining was largely unrelated to histopathological parameters or patient prognosis among pT2-4 carcinomas, except of p53 strong/very strong immunostaining. p16 expression predominated in tumors with very strong, strong, and negative p53 staining and the combination of p53 negative/p16 strongly positive cancers was linked to features of tumor aggressiveness.

CONCLUSION

Aberrant p53 and p16 immunostaining increases during grade and stage progression although p53 negative and p16 positive immunostaining lack prognostic significance in pT2-4 carcinomas. Potential diagnostic features are that high level p16 expression is limited to neoplastic urothelium and p53 null phenotype to aggressive cancers (grade 3 and invasive).

Biomarkers in bladder cancer: translational and clinical implications

Bladder cancer is associated with high recurrence and mortality rates. These tumors show vast heterogeneity reflected by diverse morphologic manifestations and various molecular alterations associated with these disease phenotypes. Biomarkers that prospectively evaluate disease aggressiveness, progression risk, probability of recurrence and overall prognosis would improve patient care. Integration of molecular markers with conventional pathologic staging of bladder cancers may refine clinical decision making for the selection of adjuvant and salvage therapy. In the past decade, numerous bladder cancer biomarkers have been identified, including various tumor suppressor genes, oncogenes, growth factors, growth factor receptors, hormone receptors, proliferation and apoptosis markers, cell adhesion molecules, stromal factors, and oncoproteins. Recognition of two distinct pathways for urothelial carcinogenesis represents a major advance in the understanding and management of this disease. Nomograms for combining results from multiple biomarkers have been proposed to increase the accuracy of clinical predictions. The scope of this review is to summarize the major biomarker findings that may have translational and clinical implications.

Trimodality Treatment and Selective Organ Preservation for Bladder Cancer

Standard treatment for muscle-invasive bladder cancer is cystectomy. Trimodality treatment, including transurethral resection of the bladder tumor (TURBT), radiation therapy and chemotherapy, has been shown to produce survival rates comparable to those of cystectomy. With these programs, cystectomy has been reserved for patients with incomplete response or local relapse. During the past 15 years, organ preservation by trimodality treatment has been investigated in prospective series from single centers and cooperative groups, with more than 1,000 patients included. Five-year overall survival rates in the range of 50% to 60% have been reported, and approximately three quarters of the surviving patients maintained their bladder. Clinical criteria helpful in determining ideal patients for bladder preservation include early tumor stage (including high-risk T1 disease), a visibly complete TURBT, and absence of ureteral obstruction. Close coordination among all disciplines is required to achieve optimal results. Future investigations will focus on (1) optimizing radiation techniques and incorporating more effective systemic chemotherapy, and (2) the proper selection of patients based on molecular makers.

Prognostic markers for bladder cancer: International Consensus Panel on bladder tumor markers

The International Consensus Panel on cytology and bladder tumor markers evaluated markers that have the ability to predict tumor recurrence, progression, development of metastases, or response to therapy or patient survival. This article summarizes those findings. The panel mainly reviewed articles listed in PubMed on various prognostic indicators for bladder cancer. Based on these studies, most of which were case-control retrospective studies, various prognostic indicators were classified into 6 groups: (1) microsatellite-associated markers, (2) proto-oncogenes/oncogenes, (3) tumor suppressor genes, (4) cell cycle regulators, (5) angiogenesis-related factors, and (6) extracellular matrix adhesion molecules. The panel concluded that although certain markers, such as Ki-67 and p53, appear to be promising in predicting recurrence and progression of bladder cancer, the data are still heterogeneous. The panel recommends that identifying definitive criteria for test positivity, a clearly defined patient population, standardization of techniques used to evaluate markers, and clearly specified endpoints and statistical methods will help to bring accurate independent prognostic indicators into the clinical management of patients with bladder cancer.

The p53 tumor suppressor gene and nuclear protein: basic science review and relevance in the management of bladder cancer

PURPOSE

An extensive body of literature regarding p53 has accumulated during the last 2 decades. The cellular mechanisms of p53 are complex yet well-defined, whereas its clinical usefulness in the management of bladder cancer remains controversial. We outline the basic constitutive functions of p53 and summarize its current role in the management of transitional cell carcinoma of the bladder.

MATERIALS AND METHODS

We conducted a MEDLINE based literature review concerning the fundamental mechanisms of p53 and its role in the management of bladder cancer.

RESULTS

The p53 gene is a tumor suppressor gene that acts as "guardian of the genome." Many diverse cellular events, including DNA damage and hypoxia, activate the p53 gene. The p53 protein functions as a transcription factor, regulating downstream genes involved in cell cycle arrest, DNA repair and programmed cell death. Loss of p53 function confers genomic instability, impaired apoptosis and diminished cell cycle restraint. Therefore, p53 mutations select for certain critical features of malignancy. Alteration of P53 is the most common mutation in human cancer. Roughly half of all human malignancies, including many urological cancers, exhibit p53 mutations. In bladder cancer p53 mutations have been associated with higher tumor grade and advanced stage, as well as progression of superficial disease to muscle invasion. Moreover, p53 nuclear over expression appears to be an independent predictor of disease progression and decreased survival after cystectomy.

CONCLUSIONS

The importance of p53 mutation in tumor cell biology is irrefutable. Wild-type p53 mediates imperative functions such as regulation of the cell cycle and programmed cell death. Deficiency of p53 function by mutation or inactivation abrogates normal cell cycle checkpoints and apoptosis, generating a favorable milieu for genomic instability and carcinogenesis. However, despite the manifest importance of p53 in human malignancy, its current role in the management of bladder cancer appears somewhat limited. A multitude of retrospective studies have associated p53 mutations with adverse outcomes in superficial and muscle invasive disease. Nonetheless, randomized prospective studies are needed to determine the potential clinical implications of p53 in bladder cancer.

[Molecular biology in bladder cancer]

Progress of molecular biology with regard to etiopathogeny of tumours in general, and cancer of the bladder in particular, is taking place at such a vertiginous pace that practising urologists find themselves overwhelmed in terms of their ability to learn and keep updated in so complex a subject. The understanding of certain molecular factors with critical influence on the formation, growth and progression of a tumour of the bladder, is forcing us to make unbiased assessments on the role they will play in the evolution and survival of this neoplasia. It is anticipate they will be much more reliable than traditionally established morphological factors such as grade and stage. We also include a literature review with an analysis and elucidation of the role played by oncogenes, tumor suppressor genes, vascular density markers, telomerase etc., in the formation and growth of cancer of the bladder and their likely relationships with already established clinico-pathological factors.

Apoptosis, p53, bcl-2, and Ki-67 in invasive bladder carcinoma: possible predictors for response to radiochemotherapy and successful bladder preservation

PURPOSE

Several groups have reported the value of bladder preservation by a combined treatment protocol, including transurethral resection (TUR-B) and radiochemotherapy (RCT). As more experience is acquired with organ-sparing treatment, patient selection should be optimized. The purpose of this study was to investigate the role of several biologic markers that may predict response to RCT in muscle-invasive bladder carcinoma.

METHODS AND MATERIALS

The apoptotic index (AI), Ki-67, p53, and bcl-2 were evaluated by immunohistochemistry on pretreatment biopsies from 70 patients treated for invasive bladder cancer by TUR-B and RCT. Expression of each marker was correlated with initial response, local control, and cancer-specific survival with preserved bladder. An exploratory multivariate analysis was also performed that included clinical and immunohistochemical variables.

RESULTS

A high AI (> median = 1.6%) and a high Ki-67 index (> median = 8.8%), but not the p53- and bcl-2 expression, were significantly related to initial complete response (CR) and local control with preserved bladder after 5 years. When the AI and Ki-67 expression were considered simultaneously, the association with initial CR (p < 0. 001), local control (p = 0.0002), and cancer-specific survival with preserved bladder (p = 0.008) was highly significant. In an exploratory multivariate analysis (final model), only AI, Ki-67, and the combined AI/Ki-67 variable retained significance for local control with preserved bladder at 5 years.

CONCLUSION

Patients with a high spontaneous AI and a high pretreatment Ki-67 index should be considered preferentially for treatment with RCT, whereas tumors with low proliferation and low levels of apoptosis are less likely to respond to RCT.

Radiotherapy in bladder cancer

In the present review, we have evaluated the outcome of radiotherapy in patients with bladder cancer. The exact value of radical radiotherapy is difficult to establish because changes in treatment techniques and selection of patients have biased the results. The 5-year survival rates are reported to be 35-71% in T1 tumors, 27-59% in T2 tumors, 10-38% in T3 tumors and 0-16% in T4 tumors. Several other factors, like performance status and hemoglobin level, are important for the outcome. Morbidity of radical radiotherapy depends on several treatment and patient related factors, but 50-75% experience acute intestinal or urological symptoms and 10-20% may develop severe late toxicity, depending on the kind of registration. The importance of field size or overall treatment time cannot be established from available data. Hyperfractionation with dose escalation has proven effective in one study. Preoperative radiotherapy with cystectomy has not proven better than cystectomy alone or better than radiotherapy alone. The addition of systemic chemotherapy has increased disease-free survival, but has not significantly reduced the rate of distant metastases or improved overall survival. Presently, the standard radiation regimen is a conventional dose and fractionation schedule to a total dose of 60-66 Gy with a three- or four-field technique covering the bladder and tumor. The efficacy of additional irradiation of regional lymph nodes is questionable. New treatment possibilities with advanced techniques of radiotherapy, hyperfractionation and dose escalation and/or the addition of systemic chemotherapy may improve outcome. These options should be further explored in clinical trials.

Expressions of p53 and PCNA do not correlate with the international index or early response to chemotherapy in non-Hodgkin's lymphoma

The expression of p53 and PCNA on deparaffinized sections of tumor was assessed in relation to the International Index and response to chemotherapy. Thirty-five non-Hodgkin's lymphoma (NHL) patients were divided into three groups: aggressive NHL, mantle cell lymphoma (MCL), and low-grade NHL. None of the expressions correlated with the International Index or early response to chemotherapy in any group. In low-grade NHL, none of the patients expressed p53. Only one of three patients with overexpression of p53 showed conformational change and alteration of sequence in exon 7 by PCR-SSCP and DNA sequencing. The results showed that p53 and PCNA staining were not useful for predicting early response to chemotherapy, and that their expressions had no correlation with the International Index.