Suppression of HSF1 activity by wildtype p53 creates a driving force for p53 loss-of-heterozygosity

Tamara Isermann,Jinyu Li,Adrian Stender,Özge Çiçek Şener,Luisa Klemke,Ramona Schulz-Heddergott,Nadine Winkler,Florian Wegwitz,Albrecht Neesse,Ute M Moll

doi:10.1038/s41467-021-24064-1

Tamara Isermann, Jinyu Li + Show 8 more

Open Access

https://doi.org/10.1038/s41467-021-24064-1

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Abstract

The vast majority of human tumors with p53 mutations undergo loss of the remaining wildtype p53 allele (loss-of-heterozygosity, p53LOH). p53LOH has watershed significance in promoting tumor progression. However, driving forces for p53LOH are poorly understood. Here we identify the repressive WTp53–HSF1 axis as one driver of p53LOH. We find that the WTp53 allele in AOM/DSS chemically-induced colorectal tumors (CRC) of p53R248Q/+ mice retains partial activity and represses heat-shock factor 1 (HSF1), the master regulator of the proteotoxic stress response (HSR) that is ubiquitously activated in cancer. HSR is critical for stabilizing oncogenic proteins including mutp53. WTp53-retaining CRC tumors, tumor-derived organoids and human CRC cells all suppress the tumor-promoting HSF1 program. Mechanistically, retained WTp53 activates CDKN1A/p21, causing cell cycle inhibition and suppression of E2F target MLK3. MLK3 links cell cycle with the MAPK stress pathway to activate the HSR response. In p53R248Q/+ tumors WTp53 activation by constitutive stress represses MLK3, thereby weakening the MAPK-HSF1 response necessary for tumor survival. This creates selection pressure for p53LOH which eliminates the repressive WTp53-MAPK-HSF1 axis and unleashes tumor-promoting HSF1 functions, inducing mutp53 stabilization enabling invasion.

Highlights

The vast majority of human tumors with p53 mutations undergo loss of the remaining wildtype p53 allele. p53LOH has watershed significance in promoting tumor progression
heat-shock factor 1 (HSF1), the master transcription factor of the cytoprotective inducible heat-shock stress response (HSR), governs the expression of stress-induced chaperones, including HSP90, HSP70, and HSP40 and is the major proteotoxic defense in tumors, preventing aberrant oncoproteins from aggregation[41,42,43]
We identify that the remaining WTp53 allele in p53R248Q/+ tumors, despite a partial dominant-negative effect (DNE) by the Q allele, still represses the HSF1 chaperone axis, thereby preventing mutp53R248Q stabilization, GOF, and invasion

Summary

Results

P53LOH is a prerequisite for mutp[53] stabilization and invasion in colorectal cancer. In HSF1-overexpressing HCT116 clones cell cycle inhibition by Palbociclib (like Nutlin) repressed pSer326-HSF1 levels (Fig. 4g) and HSF1 target gene expression (Supplementary Fig. 4e). After an initial cell death wave due to Nutlin-activated WTp53 (Supplementary Fig. 7f), many organoids—those that had undergone p53LOH (Fig. 7h, bottom) and reduced p53 target gene expression (Supplementary Fig. 7g)—were able to regrow and showed invasive morphologic structures with branchings and protrusions (Supplementary Fig. 7f). They exhibit upregulation of HSF1 targets (Fig. 7i), EMT markers (Fig. 7j), and Stat[3] targets (Supplementary Fig. 7h). These data further support that p53LOH-mediated HSF1 activation causes mutp[53] stabilization and enables invasiveness

Discussion

Findings

Methods