Induction of the metastatic phenotype by transfection of the nuclear oncogene p53: increases in cytoplasmic diacylglycerol levels and reduction in class I major histocompatibility antigen expression are not sufficient to explain the changes in metastatic capacities

p53 protein expression and prognosis in squamous cell carcinoma of the esophagus

BACKGROUND

The p53 gene product is known to regulate cell growth and proliferation. Whereas the wild-type p53 protein suppresses cell growth, the mutated p53 protein acts as an oncogene. Mutations in the p53 gene usually result in p53 protein stabilization and accumulation; so that the gene product can be detected by immunohistochemistry. Recently, the immunohistochemical detection of the p53 protein was associated with prognosis in breast, colorectal, and other types of cancer. However, its prognostic role in esophageal cancer remains to be elucidated.

METHODS

p53 expression in formalin fixed, paraffin embedded samples of 204 patients with primary squamous cell carcinoma of the esophagus, who underwent esophageal resection, were analyzed immunohistochemically with DO-1, a monoclonal antibody that detects wild-type and mutant forms of p53. The relationship between p53 immunoreactivity and prognostic factors was determined by the Chi-square test, and the prognostic impact of p53 protein expression was analyzed using univariate and multivariate survival analyses.

RESULTS

In 137 of 204 tumors (67.2%), nuclear immunoreactivity for the p53 protein was detected. There was no correlation with sex, age, pathologic tumor (pT) category, pathologic lymph node (pN) category, metastasis (M) category, residual cancer (R) category, histologic grade, or preoperative radiation therapy. In contrast to clinicopathologic parameters, p53 expression was not correlated with prognosis in univariate and multivariate survival analyses.

CONCLUSIONS

The p53 protein can be detected by immunohistochemistry in a high percentage of squamous cell carcinomas of the esophagus. However, the overexpression of the p53 gene product has no impact on the prognosis.

Critical review of the models to study the biologic progression of bladder cancer

For transitional cell carcinoma of the bladder, clinical data indicate that invasive, metastatic tumors can arise through at least two different progression pathways. The majority of invasive, metastatic bladder neoplasms clinically present de novo, i.e., the patients have no history of malignant bladder disease. This implies that the highly malignant tumor cells either arise de novo or have undergone a rapid progression. Alternatively, a considerable fraction of patients with superficial bladder cancer process to invasive disease after a history of relatively benign superficial TCC. The molecular and cell biological basis of tumor progression is only poorly understood. Clearly, a better understanding of this progress could have profound clinical implications, since patients with superficial TCC with a high risk for progression would have to be treated more aggressively. We discuss the problems that are associated with tumor biological studies on early steps in the progression of TCC, especially from a "model system point of view."

p53 expression and prognosis in gastric carcinoma

Abnormalities of the p53 gene have been identified in many malignancies, with reports of aberration in over half of colorectal, lung, breast and hepatocellular carcinoma cases. The normal gene acts as a recessive oncogene, while mutations change the apparent function to that of a dominant oncogene. In this investigation a 3-layered immunoperoxidase technique was applied to routinely fixed and paraffin-embedded tissue sections from 125 gastric carcinomas, using a polyclonal anti-p53 antibody (CM-I). We found that 57% of these carcinomas expressed high levels of p53 protein (positive nuclear staining). Survival analysis revealed a strong association between p53 status of the tumour and patient survival time after diagnosis (p = 0.02, Mantel-Cox Test); odds ratio of death, 2.09 (95% confidence interval 1.02 to 4.25). The 5-year survival of patients with p53-expressing tumours was 24%, compared with 56% for those non-p53-expressing tumours (the median survival times were 13 and 102 months, respectively).

Molecular oncogenetics of metastasis

Metastasis is a complex non-stochastic process that is most likely the result of genetic and epigenetic interactions of a wide variety of genes. The search for a single gene which can encompass such a pleiotropic response as to account for the observed phenotypic characteristics of metastatic tumour populations has been unsuccessful. Particular studies involving gene transfection, subtractive hybridisation and cell fusion are beginning to identify specific genes which contribute to metastasis in some cell types. However, such analyses are complicated by the inherent genetic instability and phenotypic heterogeneity present in tumour populations. A more detailed understanding of the metastatic process may require an abandoning of current generalised approaches to metastasis in favour of concentrating on key components of the metastatic cascade such as adhesion and invasion.