Nuclear inclusion bodies of mutant and wild-type p53 in cancer: a hallmark of p53 inactivation and proteostasis remodeling by p53 aggregation

摘要

Although p53 protein aggregates have been observed in cancer cell lines and tumour tissue, their impact in cancer remains largely unknown. Here, we extensively screened for p53 aggregation phenotypes in tumour biopsies and identified nuclear inclusion bodies (nIBs) of transcriptionally inactive mutant or wild-type p53 as the most frequent aggregation-like phenotype across six different cancer types. p53-positive nIBs co-stained with nuclear aggregation markers and shared molecular hallmarks of nIBs commonly found in neurodegenerative disorders. In cell culture, tumour-associated stress was a strong inducer of p53 aggregation and nuclear inclusion body formation. This was most prominent for mutant p53, but could also be observed in wild-type p53 cell lines for which nIB formation correlated to the loss of p53s transcriptional activity. Importantly, protein aggregation also fueled the dysregulation of the proteostasis network in the tumour cell by inducing a hyper-activated, oncogenic heat-shock response to which tumours are commonly addicted, and by overloading the proteasomal degradation system, an observation that was most pronounced for structurally destabilized mutant p53. Patients exhibiting tumours with p53-positive nIBs suffered from a poor clinical outcome similar to loss-of-p53-expression, and tumour biopsies displayed a differential proteostatic expression profile associated to p53-nIBs. p53-positive nIBs therefore highlight a malignant state of the tumour that results from the interplay between (i) the functional inactivation of p53 through mutation and/or aggregation and (ii) microenvironmental stress, a combination that catalyses proteostatic dysregulation. This study highlights several unexpected clinical, biological and therapeutically unexplored parallels between cancer and neurodegeneration.