Abstract B59: Induction of TXNIP in response to metabolic changes associated with loss of p53

Abstract

Abstract The understanding of the function of p53 has expanded beyond its role as a master cell cycle regulator. Recent findings connect p53 to cellular metabolism in that it suppresses anaerobic metabolism, the preferred mode of ATP production of most transformed cells. Interestingly, the p53-inducible genes that modulate metabolism also alter production or scavenging of reactive oxygen species (ROS). To better understand the metabolic changes that occur in response to p53-deficiency, we compared the expression of genes related to oxidative stress in the mammary fat pad of p53 +/+ and p53 +/− female mice. From a qPCR array that measured the expression of 85 genes, thioredoxin-interacting protein (TXNIP) levels were markedly increased in the p53 +/− mice compared to p53 +/+ mice (n = 3/group). This gene is of particular interest because TXNIP expression is increased by glucose flux and binds reduced thioredoxin, resulting in accumulation of ROS which has been shown to activate p53. To validate this finding, qPCR was performed (n=6/group) and TXNIP mRNA expression was increased 2.6 ± 0.2 fold (p < 0.001) in the mammary fat pad of p53 +/− mice compared to p53 +/+ mice. Importantly, the p53 +/− mice exhibited significantly lower fasting glucose levels than 53 +/+ mice (104.2 ± 7.0 versus 128.5 ± 3.1 mg/dL, p <0.01). We hypothesized that induction of TXNIP is in response to metabolic changes occurring with loss of p53. Using siRNA to knockdown p53, we tested this hypothesis and found that TXNIP mRNA expression increased 2.4 ± 0.3 fold (p < 0.01) 72 hours after p53 knockdown compared to control cells receiving scrambled siRNA. Furthermore, this increase was preceded by a spike in glucose consumption and lactate production. From these data, we conclude that TXNIP, in the absence of p53, is responding to changes in cellular metabolism. Current experiments are aimed at determining the effect of TXNIP induction in MCF7 cells on proliferation and glucose metabolism. Citation Information: Cancer Prev Res 2010;3(1 Suppl):B59.