ABSTRACT
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 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. In addition, mtp53 creates a dependency on the nucleoside salvage pathway enzyme deoxycytidine kinase for the maintenance of a proper balance in dNTP pools required for proliferation. These data indicate that mtp53-harbouring 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.
Subject(s)
Brain Neoplasms/genetics , Breast Neoplasms/genetics , Gene Expression Regulation, Neoplastic/genetics , Nucleotides/metabolism , Tumor Suppressor Protein p53/genetics , Animals , Blotting, Western , Brain Neoplasms/secondary , Breast Neoplasms/metabolism , Cell Cycle , Cell Line, Tumor , Cell Proliferation/genetics , Deoxycytidine Kinase , Female , Gene Knockdown Techniques , Guanosine Triphosphate , Humans , Immunoprecipitation , Kaplan-Meier Estimate , Mice , Mutation , Neoplasm Invasiveness/genetics , Neoplasm Transplantation , Nucleosides/metabolism , Prognosis , Promoter Regions, Genetic , Proportional Hazards Models , Tumor Stem Cell Assay , Tumor Suppressor Protein p53/metabolismABSTRACT
We sought to determine whether motor and cognitive deficits associated with cassava (food) cyanogenic poisoning were associated with high concentrations of F2-isoprostanes, well-established indicators of oxidative damage. Concentrations of serum F2-isoprostanes were quantified by LC-MS/MS and anchored to measures of motor proficiency and cognitive performance, which were respectively assessed through BOT-2 (Bruininks/Oseretsky Test, 2nd Edition) and KABC-II (Kaufman Assessment Battery for Children, 2nd edition) testing of 40 Congolese children (21 with konzo and 19 presumably healthy controls, overall mean age (SD): 9.3 (3.2) years). Exposure to cyanide was ascertained by concentrations of its main metabolite thiocyanate (SCN) in plasma and urine. Overall, SCN concentrations ranged from 91 to 325 and 172 to 1032 µmol/l in plasma and urine, respectively. Serum isoprostanes ranged from 0.1 to 0.8 (Isoprostane-III), 0.8 to 8.3 (total Isoprostane-III), 0.1 to 1.5 (Isoprostane-VI), 2.0 to 9.0 (total Isoprostane-VI), or 0.2 to 1.3 ng/ml (8,12-iso-iPF2α-VI isoprostane). Children with konzo poorly performed at the BOT-2 and KABC-II testing relative to presumably healthy children (p<0.01). Within regression models adjusting for age, gender, motor proficiency, and other biochemical variables, 8,12-iso-iPF2α-VI isoprostane was significantly associated with the overall cognitive performance (ßâ=â-32.36 (95% CI: -51.59 to -13.03; P<0.001). This model explained over 85% of variation of the KABC-II score in children with konzo, but was not significant in explaining the motor proficiency impairment. These findings suggest that cognitive deficits and, possibly, brain injury associated with cassava poisoning is mediated in part by oxidative damage in children with konzo. 8,12-iso-iPF2α-VI isoprostane appears to be a good marker of the neuropathogenic mechanisms of konzo and may be used to monitor the impact of interventional trials to prevent the neurotoxic effects of cassava cyanogenic poisoning.
