Regulation of nucleotide metabolism by mutant p53 contributes to its gain-of-function activities

Abstract

SUMMARY Mutant p53 (mtp53) is an oncogene that drives cancer cell proliferation. Here we report that mtp53 associates with the promoters of numerous nucleotide metabolism genes (NMG). Mtp53 knockdown reduces NMG expression and substantially depletes nucleotide pools, which attenuates GTP dependent protein (GTPase) activity and cell invasion. Addition of exogenous guanosine or GTP restores the invasiveness of mtp53 knockdown cells, suggesting that mtp53 promotes invasion by increasing GTP. Additionally, mtp53 creates a dependency on the nucleoside salvage pathway enzyme deoxycytidine kinase (dCK) for the maintenance of a proper balance in dNTP pools required for proliferation. These data indicate that mtp53 harboring cells have acquired a synthetic sick or lethal phenotype relationship with the nucleoside salvage pathway. Finally, elevated expression of NMG correlates with mutant p53 status and poor prognosis in breast cancer patients. Thus, mtp53’s control of nucleotide biosynthesis has both a driving and sustaining role in cancer development.

Molecularly targeted therapies for p53-mutant cancers

“…Several studies demonstrated that gain-of-function (GOF) p53 mutants regulate cellular and nucleotide metabolism (148–150). Using a three-dimensional (3D) culture model, Freed-Pastor et al discovered that breast cancer cell lines expressing either p53 R273H or p53 R280K disrupted acinar morphology through upregulation of the mevalonate pathway, which is responsible for cholesterol synthesis (148).…”

“…Given that wildtype p53 could activate AMPK activity through transcriptional activation of the gene encoding β subunit of AMPK (152), these results strongly support a transcription-independent mechanism by which mutant p53 promotes tumor progression by activating cancer cell metabolism. Regulation of nucleotide metabolism by mutant p53 was recently found to be functionally important for GOF activities (150). CHIP-seq analysis of mutant p53 knockdown breast cancer cells demonstrated that loss of mutant p53 reduced many nucleotide metabolism genes (NMGs) and substantially depleted nucleotide pools, which attenuated GTP-dependent protein activity and cell invasion (150).…”

“…Regulation of nucleotide metabolism by mutant p53 was recently found to be functionally important for GOF activities (150). CHIP-seq analysis of mutant p53 knockdown breast cancer cells demonstrated that loss of mutant p53 reduced many nucleotide metabolism genes (NMGs) and substantially depleted nucleotide pools, which attenuated GTP-dependent protein activity and cell invasion (150). The reduction of invasion by mutant p53 knockdown was rescued by addition of exogenous GTP, suggesting that mutant p53 promotes invasion by increasing GTP.…”

“…The reduction of invasion by mutant p53 knockdown was rescued by addition of exogenous GTP, suggesting that mutant p53 promotes invasion by increasing GTP. Mutant p53 appears to depend on deoxycytidine kinase, a nucleoside salvage pathway enzyme, to maintain a proper balance of the dNTP pools required for cell proliferation (150). These data reveal the mechanism underlying the lethal genetic interaction between mutant p53 and deoxycytidine kinase.…”

Characterization of cancer-associated missense mutations in MDM2

“…28 More than 50% of human tumors have a mutated form of p53 (mtp53) that is more stable and has gain-of-function activities such as promoting cell growth, chemotherapy resistance, angiogenesis, and metastasis. 29,30 An alternative mechanism by which p53 is thought to be inactivated in human cancers is through increased expression of MDM2. To date, there are 92 mutations in the MDM2 gene reported in the Catalog of Somatic Mutations in Cancer (COSMIC) website.…”