Objective: The tumor suppressor p53 generates the N-terminally truncated isoforms Δ40p53 and Δ133p53 that possess the ability to modulate p53 function in vitro. The aim of the present study was to evaluate the clinical relevance of p53 isoforms in the main histological subtypes of ovarian cancer.
Methods: Δ40p53, Δ133p53, and full-length p53 (FLp53) expression was determined in 45 mucinous, 30 endometrioid, and 91 serous ovarian cancer specimens as well as 42 normal ovarian tissues using reverse transcriptase-quantitative polymerase chain reaction. In a subgroup of mucinous ovarian cancer cases, Δ40p53 expression was examined using Western blot analysis. A functional yeast-based assay and subsequent sequencing were performed to analyze the p53 mutational status.
Results: In endometrioid cancer specimens, Δ133p53 expression was significantly lower than in mucinous and serous cases (P = 0.016) or in normal tissues (P = 0.004). Mucinous cancer samples showed elevated Δ40p53 expression as compared with normal ovarian tissues (P = 0.003). In addition, high Δ40p53 expression constituted an independent prognostic marker for recurrence-free but not for overall survival in patients with mucinous ovarian cancer (hazard ratio, 0.267; 95% confidence interval, 0.094-0.756 [P = 0.013]; hazard ratio, 0.453, 95% confidence interval, 0.193-1.064 [P = 0.069]). Western blot analysis confirmed the presence of p53β and Δ40p53α in a subset of patients with mucinous ovarian cancer. Expression of p53 isoforms was not associated with p53 mutational status or clinicopathologic parameters.
Conclusions: We show that expression of p53 isoforms differs in histological subtypes, thus supporting the hypothesis that histological subtypes represent distinct disease entities. In addition, we provide first evidence for a favorable role of Δ40p53 in patients with mucinous ovarian cancer.