Dissecting the impact of mutant p53 in life-death decisions of cancer cells exposed to microenvironmental stress

Cancer cells within tumor masses are chronically exposed to stress caused by nutrient deprivation, oxygen limitation, and high metabolic demand. They also accumulate hundreds of mutations, potentially generating aberrant proteins that cannot properly fold and cause proteotoxic stress. Finally, cancer cells are exposed to multiple damages during chemotherapy. In a growing tumor, transformed cells eventually adapt to these conditions, eluding the death-inducing outcomes of signaling cascades triggered by chronic stress. Notably, activation of stress-related pathways may actually promote cancer progression, by inducing epithelial- mesenchymal transition (EMT), stimulating angiogenesis, and supporting tumor dormancy. Thus, understanding the genetic determinants that enable adaptation of cancer cells to stress is critical to improve treatment efficacy. Missense mutations in the TP53 gene are extremely frequent in human cancers and give rise to mutant p53 proteins (mutp53) that lose tumor suppressive activities. Various evidences suggest that cancer cells acquire selective advantages by retaining mutant forms of the protein; in fact, p53 mutant proteins can display powerful oncogenic activities, defined as Gain of Function, that promote tumor progression and resistance to treatments. Recent studies suggest that mutant p53 proteins play a peculiar role in supporting cancer cell homeostasis, by modulating inflammatory pathways, proteasome activity, folding of N-glycosylated proteins, and the response to ER stress. Based on these premises, we propose to study the impact of p53 mutations in the adaptation of cancer cells to stress; specifically focusing on the unfolded protein response (UPR) and ferroptotic cell death. In fact, we have preliminary evidence that the response to ER stress and sensitivity to ferroptosis are genetically linked to each other, and may be related to crucial cancer phenotypes such as cell motility, invasiveness, and chemoresistance. To this aim, we will analyze a panel of breast, prostate and pancreatic cancer cell lines with diverse missense p53 mutations. We will systematically test their response to ER stress and ferroptotic stimuli to evaluate how expression of mutp53 – or specific p53 mutations – correlates with resistance or sensitivity. Next, we will investigate the specific role of mutp53 in this phenotype, by performing broad transcriptomic approaches and conducting specific functional studies. Finally, we aim to define the mechanism by which mutp53 may affect the response to ER stress or ferroptosis by discovering key molecular partners or target genes involved in the phenotype. This study aims to improve our knowledge on the mechanisms that allow cancer cells to adapt and survive under chronic stress in a growing tumor, and in particular on the role played by specific TP53 mutations, hopefully finding novel potential targets for therapy and additional elements to guide the choice of treatment.