Assessing p53 in clinical contexts: unlearned lessons and new perspectives

Abstract

There is compelling evidence for the central role of the p53 pathway in human neoplasia but, despite an enormous literature, the clinical utility of assessing this pathway remains ambiguous. Even simple questions about the assessment of p53 status in clinical samples remain unanswered and the literature is confusing and often contradictory. The p53 pathway is certainly complicated and the biochemical mechanisms for regulating the function of p53 and its downstream consequences are rabbinical in complexity. This perspective considers this complexity and the reasons why establishing the true utility of clinical assessment of p53 has proven to be so difficult. Indeed, recent observations regarding the existence of alternate splice variants of p53, the complexity of p53 regulation, and the existence of allelic variants of p53 and its regulators with distinct functionality makes the situation even more complex. Problems with the available assays are considered and the need to consider an array of methodological issues is emphasized. Newer strategies including analysis of the expression of downstream targets of p53 and the use of threshold strategies to measure p53 protein may provide more robust measures of the p53 pathway in clinical settings, perhaps coupled with cheap sequencing-based approaches for mutation (and polymorphism) detection. However, progress will only be made if these methodological issues are resolved and robust assays are performed in the context of appropriately powered studies in clinical trial settings.

HPV infection and immunochemical detection of cell-cycle markers in verrucous carcinoma of the penis

“…Furthermore, considering complexity of p53 pathway and its diverse regulatory mechanisms, any changes in physiological conditions within the tissue may greatly affect expression levels and activity of wild-type protein and its mutant forms at a given time. 38 Ideally, additional study of mutations within the p53 gene would confirm the mutational status of p53 in those samples.…”

Survivin is an independent predictor of short-term survival in poor prognostic breast cancer patients

“…There are several problems in using this technique for p53 that relate to a failure to detect all mutations plus assessment of what is positive (Hall and McCluggage, 2006) so the available evidence would favour the use of mutational analysis (Bergh et al, 1995;Aas et al, 1996;Berns et al, 2000). Phosphorylation of p53 at Ser 392 has been shown to be a frequent modification in tumours (Minamoto et al, 2001).…”

WRN promoter methylation possibly connects mucinous differentiation, microsatellite instability and CpG island methylator phenotype in colorectal cancer

“…37 p53 positivity was defined as 50% or more of tumor cells with unequivocal strong nuclear staining, as this high threshold considerably improved specificity in previous studies. 43,44 For p21 (CDKN1A/CIP1) immunohistochemistry, we incubated deparaffinized whole tissue sections in citrate buffer at high power in a microwave for 30 min (in a pressure cooker). Tissue sections were then incubated with 3% H 2 O 2 (10 min) to block endogenous peroxidase, and then incubated with protein block (Vector Laboratories, Burlingame, CA, USA) (10 min).…”