Combined p53 and MDM2 biomarker analysis shows a unique pattern of expression associated with poor prognosis in patients with renal cell carcinoma undergoing radical nephrectomy.

OBJECTIVE: To resolve much debated issues surrounding p53 function, expression and mutation in renal cell carcinoma (RCC), we performed the first study to simultaneously determine p53/MDM2 expression, TP53 mutational status (in p53-positive patients) and outcome in RCC. PATIENTS AND METHODS: In total, 90 specimens obtained from patients with RCC, who were treated by radical nephrectomy, were analyzed by immunohistochemistry for p53 and MDM2 on a tissue microarray, and p53 was functionally and genetically analyzed in p53 positive samples. Outcome analysis was by the Kaplan-Meier method and univariate analysis was used to identify variables for subsequent multivariate analysis of correlations between clinical parameters and biomarker expression. RESULTS: Up-regulation of p53 in RCC is strongly linked with MDM2 up-regulation (P < 0.001). Increased coexpression of p53 and MDM2 identifies those patients with a significantly reduced disease-specific survival by univariate (P= 0.036) and Cox multiple regression analysis (P= 0.027; relative risk, 3.20). Functional (i.e. functional analysis of separated alleles in yeast) and genetic analysis of tumours with increased p53 expression shows that most patients (86%) retain wild-type p53. CONCLUSIONS: Coexpression of p53/MDM2 identifies a subset of patients with poor prognosis, despite all of them having organ-confined disease. Up-regulated p53 is typically wild-type and thus provides a mechanistic explanation for the association between p53 and MDM2 expression: up-regulated wild-type p53 likely promotes the observed MDM2 coexpression. The results obtained in the present study suggest that the p53 pathway is altered in a tissue/disease-specific manner and that therapeutic strategies targeting this pathway should be investigated to determine whether the tumour suppressive function of p53 can be rescued in RCC.

Loss of MTBP expression is associated with reduced survival in a biomarker-defined subset of patients with squamous cell carcinoma of the head and neck.

BACKGROUND: Recent genetic studies have implicated p53 mutation as a significant risk factor for therapeutic failure in squamous cell carcinoma of the head and neck (SCCHN). However, in a recent meta-analysis in the literature of p53 from major anatomical subsites (larynx, oral cavity, oropharynx/hypopharynx), associations between patient survival and p53 status were ambiguous. METHODS: The authors examined a cohort of SCCHNs using a previously developed biomarker combination that likely predicts p53 status based on p53/MDM2 expression levels determined by immunohistochemistry (IHC). In addition, the authors generated and validated an antibody to MTBP (an MDM2 binding protein that alters p53/MDM2 homeostasis and may contribute to metastatic suppression) and have incorporated data for MTBP expression into the current analyses. RESULTS: Analysis of expression data for p53 and MDM2 in 198 SCCHN patient samples revealed that the biomarker combination p53 + ve/MDM2-low (likely indicative of p53 mutation) was significantly associated with reduced overall survival (log-rank P = .035) and was an independent prognostic factor (P = .013; HR, 1.705; 95% CI, 1.12-2.60); thus, these data were compatible with earlier genetic analyses. By using IHC for p53 and MDM2 to dichotomize patients, the authors found that loss of MTBP expression was significantly associated with reduced survival (log-rank P = .004) and was an independent prognostic factor (P = .004; HR, 2.78; 95% CI, 1.39-5.54) in p53 + ve/MDM2-low patients. CONCLUSIONS: These results represent the first examination of MTBP expression in human tissues and provide evidence for a p53 status-dependent role for MTBP in suppressing disease progression in SCCHN patients as well as confirming a role for p53 pathway function in delaying disease progression.

Low molecular weight heat shock protein HSP27 is a prognostic indicator in rectal cancer but not colon cancer.

OBJECTIVE: There are currently no biomarkers in routine clinical use for determining prognosis in rectal cancer. In a preliminary proteomic study, variation in the levels of heat shock protein 27 (HSP27) in colorectal cancer samples was observed. The expression of HSP27 in a cohort of 404 patients with colorectal cancer with a predominantly poor prognosis was characterised and an investigation was undertaken of whether the differences were related to clinical outcome. HSP27 levels in diagnostic rectal biopsies were compared with matched surgical samples to determine whether changes in expression occurred in the time between biopsy and surgery and to investigate whether preoperative radiotherapy affected expression. Finally, the relationship between HSP27 expression and outcome was examined in an independent cohort of 315 patients with a predominantly good prognosis. METHODS: HSP27 levels were determined using combined two-dimensional gel electrophoresis and tandem mass spectrometry (12 cases) and by immunohistochemistry using tissue microarrays of colorectal cancers sampled at surgery and 80 diagnostic rectal biopsies. RESULTS: HSP27 overexpression was strongly associated with poor cancer-specific survival in rectal cancer (n=205, p=0.0063) but not colon cancer (n=199, p=0.7385) in the cohort with a poor prognosis. Multivariate Cox regression confirmed nodal metastases (p=0.0001) and HSP27 expression (p=0.0233) as independent markers of survival in rectal cancer. HSP27 levels remained unchanged in the majority of cases (65/80, 81%) between diagnostic biopsies and matched surgical samples, regardless of whether patients had undergone preoperative radiotherapy. In the cohort with a good prognosis the association between HSP27 and survival was not observed in patients with either rectal (n=115; p=0.308) or colon cancer (n=200; p=0.713). CONCLUSION: In a large cohort of patients with a poor prognosis, HSP27 is an independent marker of poor outcome in rectal cancer; its expression is not altered by neoadjuvant radiotherapy. This finding requires validation in an independent similar cohort of patients with rectal cancer. HSP27 levels merit evaluation as a stratification factor for treatment of rectal cancer.