p53 Mutation in bladder cancer patients in Japan and inhibition of growth by in vitro adenovirus-mediated wild-type p53 transduction in bladder cancer cells

Molecular and immunohistochemical analysis of the prognostic value of cell-cycle regulators in urothelial neoplasms of the bladder

OBJECTIVE

To evaluate the prognostic and predictive value of molecular and immunohistochemical markers related to cell-cycle control in terms of recurrence, progression, and survival in urothelial neoplasms of the bladder (UNB).

PATIENTS AND METHODS

Clinical and pathological findings of 84 patients with UNB were assessed. Homozygous deletion (HD) and promoter methylation of p14ARF, p15INK4B, p16INK4A, loss of heterozygosity of the locus 9p21, p53 mutations, and immunohistochemical expression of p53, p16, p14, p21, p27, pRb, Ki67, MDM2, and cyclin D1 proteins were evaluated in relation to overall survival (OS), recurrence-free survival (RFS), and progression-free survival (PFS).

RESULTS

In the univariate analysis, RFS was shorter in cases with p14ARF (p=0.006), p15INK4B (p=0.003), p16INK4A (p=0.03) HD, low p14 immunoreactivity index (IRI) (p=0.01) and high Ki67 IRI (p=0.04); HD of the 9p21 locus genes and p14 IRI remained as independent prognostic factors for early UNB recurrence (p=0.006) whereas tumour stage (p=0.00001) and cyclin D1 IRI (p=0.049) were related to worse PFS in the multivariate analysis. In the univariate analysis, IRI for Ki67 (p=0.002), cyclin D1 (p=0.06), p53 (p=0.00008), p16 (p=0.02), p27 (p=0.0005) MDM2 (p=0.01) and p53 mutations (p=0.03) were related to poor OS, and only the Ki67 IRI retained their independent value in the multivariate analysis.

CONCLUSION

9p21 HD and p14 IRI constitute independent predictive factors for UNB recurrence and cyclin D1 IRI and tumour stage for progression. In addition, Ki67 IRI and tumour stage are independent prognostic factors for overall survival in UNB.

Growth inhibition efficacy of an adenovirus expressing dual therapeutic genes, wild-type p53, and anti-erbB2 ribozyme, against human bladder cancer cells

The altered expression of both p53 and erbB2 is strongly related to the disease status and the outcome of bladder cancers. We examined the antitumor efficacy by the modulation of these genetic alterations with a newly designed dual-gene-expressing adenovirus (Ad-p53/erbB2Rz), which expresses p53 and anti-erbB2 ribozyme simultaneously in human bladder cancer cells. Cell growth inhibition efficacy along with biological responses of this virus was compared with other viral vectors (Ad-p53, which expresses wild-type p53 cDNA, and Ad-erbB2Rz, which expresses anti-erbB2 ribozyme, solely or in combination). Sufficient transgene expression in targeted cells and the altered expression of the targeted genes and their encoded proteins were obtained by each therapeutic vector. Each of the three therapeutic viral vectors inhibited bladder cancer cell growth, and the putative additive antitumor effect was shown by the combination of two of the therapeutic vectors. Furthermore, Ad-p53/erbB2Rz had superior therapeutic efficacy when the same titers of viruses were infected. Nonspecific vector-related toxicity was minimized by reducing the total amount of viral titers by using the dual-gene-expressing adenovirus. Modulation of multiple genetic abnormalities might enhance the therapeutic efficacy, and vector-related toxicity could be minimized when the total amount of viral titers are reduced.

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.