A Neat target of p53

p53 protein expression affected by TP53 polymorphism is associated with the biological behavior and prognosis of low rectal cancer

Low rectal cancer is a subtype of colorectal cancer at a special anatomic site with distinct biological behavior. TP53 is one of the most important cancer suppressor genes, and its structural variation and abnormal expression has been revealed to be associated with multiple cancer types. However, to the best of our knowledge, the association of p53 protein expression with its gene polymorphism, biological behavior and prognosis in low rectal cancer has not been clarified. Therefore, the current study aimed to explore these associations. In the present study, 347 patients with low rectal cancer and 353 controls were enrolled. Kompetitive Allele-Specific Polymerase Chain Reaction was used to detect five polymorphic sites of the TP53 gene (rs1042522, rs12947788, rs1625895, rs2909430 and rs12951053), while immunohistochemistry was used to detect the protein expression of TP53. The associations between p53 protein expression and TP53 polymorphism, biological behavior and prognosis in low rectal cancer were systematically analyzed. In low rectal cancer, p53 protein expression was markedly higher in TP53 rs1042522 mutant carriers compared with that in other genotypes where expression was higher in poorly differentiated, III-IV phase and T3-4 phase tumors, and in III-IV phase female patients. The survival time of patients with low p53 protein expression was evidently longer in females, non-smokers and patients >60 years old. In summary, p53 protein expression was identified to be affected by TP53 rs1042522 polymorphism, and was associated with the biological behavior and prognosis of low rectal cancer. TP53 rs1042522 and the associated protein expression could be used as indicators for biological behavior and prognosis in low rectal cancer.

Analysis of the cytotoxic, genotoxic, mutagenic, and pro-oxidant effect of synephrine, a component of thermogenic supplements, in human hepatic cells in vitro

Thermogenic supplements containing synephrine (SN) are widely used to weight loss. SN is a proto-alkaloid naturally found in the bark of immature fruits of Citrus aurantium (bitter orange) that has been added to thermogenic supplements due to its chemical and pharmacological similarity with adrenergic amines, such as ephedrine and amphetamines. Although orally ingested SN is mainly metabolized in the liver, it remains unclear whether it affects the redox status and genetic material of human hepatic cells. The present study aims to examine whether SN affects cell viability, cell cycle, redox balance, genomic stability, and expression of the DNA damage response (DDR)-related genes ATM, ATR, CHEK1, CHECK2, TP53, and SIRT1 in HepG2 cells - used as in vitro hepatocyte model. SN induced overproduction of intracellular reactive oxygen species (ROS) after 6 h of treatment with the three concentrations tested (2, 20 and 200 μM). After 24 h of treatment, SN at 200 μM induced intracellular ROS overproduction and exerted cytostatic effects, while SN at 20 and 200 μM increased the levels of GPx and GSH. SN was not cytotoxic (2-5000 μM), genotoxic, and mutagenic and did not alter the expression of DDR-related genes (2-200 μM), indicating that the fast/specific SN metabolization and upregulation of antioxidant defense components to detoxify intracellular ROS were sufficient to prevent intracellular damage in HepG2 cells. In conclusion, SN showed no cytotoxic, genotoxic, and mutagenic potential at relevant concentrations for thermogenic users in human hepatic cells in vitro, although, it plays pro-oxidative action, and cytostatic effects. Taken together, our results suggest that other investigations about the hazard absence of this thermogenic compound should be performed.

Mathematical model identifies effective P53 accumulation with target gene binding affinity in DNA damage response for cell fate decision

Functional p53 signaling is essential for appropriate responses to diverse stimuli. P53 dynamics employs the information from the stimulus leading to selective gene expression and cell fate decision. However, the decoding mechanism of p53 dynamics under DNA damage challenge remains poorly understood. Here we mathematically modeled the recently dual-phase p53 dynamics under doxorubicin treatment. We found that p53 could perform sequential pulses followed by a high-amplitude terminal pulse at relatively low doxorubicin treatment, whereas p53 became steadily accumulated when damage level was high. The effective p53 integral above a threshold but not the absolute accumulation of p53 precisely discriminated survival and death. Silencing negative regulators in p53 network might promote the occurrence of terminal pulse. Furthermore, lower binding affinity and degradation rate of p53 target genes could favorably discriminate high and low dose doxorubicin treatment. Grouping by temporal profiles suggested that the p53 dynamics rather than the doxorubicin doses could better discriminate cellular outcomes and confer less variation for effective p53 integral reemphasizing the importance of p53 level regulation. Our model has established a theoretical framework that p53 dynamics can work cooperatively with its binding affinity to target genes leading to cell fate choice, providing new clues of optimized clinical design by manipulating p53 dynamics.