Dysfunctional p53 deletion mutants in cell lines derived from Hodgkin's lymphoma

Abstract

Classical Hodgkin's lymphoma (cHL) is a distinct malignancy of the immune system. Despite the progress made in the understanding of the pathology of cHL, the transforming events remain to be elucidated. It has been proposed that mutations in the TP53 gene in biopsy material as well as cell lines derived from cHL are rare and therefore not notably involved in the pathogenesis of the malignant H&RS cells. Re-evaluating the expression in cHL-derived cell lines, we found that in 3/6 of these cell lines, TP53 transcripts are characterized by deletions within exon 4 (L428 cells) and nearly a complete loss of exons 10 – 11 (L1236) or exons 8 – 11 (HDLM-2), respectively. These changes were found in otherwise rarely mutated regions of TP53. Cell lines L1236 and HDLM-2 harbour fusions with alu-repeats in their TP53 mRNA 3′-ends, resulting in the carboxyterminal truncation and loss of the transcriptional activity of p53. Transcriptional inactivity was also found for p53 in L428 cells. This study characterizes mutations in TP53 transcripts within cHL cell lines with associated functional defects in the resulting p53 proteins and therefore reintroduces the concept that mutations of TP53 might be involved in the pathogenesis of Hodgkin's lymphoma.