Peroxiredoxin I is important for cancer-cell survival in Ras-induced hepatic tumorigenesis

Peroxiredoxin I (Prx I), an antioxidant enzyme, has multiple functions in human cancer. However, the role of Prx I in hepatic tumorigenesis has not been characterized. Here we investigated the relevance and underlying mechanism of Prx I in hepatic tumorigenesis. Prx I increased in tumors of hepatocellular carcinoma (HCC) patients that aligned with overexpression of oncogenic H-ras. Prx I also increased in H-ras^G12V transfected HCC cells and liver tumors of H-ras^G12V transgenic (Tg) mice, indicating that Prx I may be involved in Ras-induced hepatic tumorigenesis. When Prx I was knocked down or deleted in HCC-H-ras^G12V cells or H-ras^G12V Tg mice, cell colony or tumor formation was significantly reduced that was associated with downregulation of pERK pathway as well as increased intracellular reactive oxygen species (ROS) induced DNA damage and cell death. Overexpressing Prx I markedly increased Ras downstream pERK/FoxM1/Nrf2 signaling pathway and inhibited oxidative damage in HCC cells and H-ras^G12V Tg mice. In this study, we found Nrf2 was transcriptionally activated by FoxM1, and Prx I was activated by the H-ras^G12V/pERK/FoxM1/Nrf2 pathway and suppressed ROS-induced hepatic cancer-cell death along with formation of a positive feedback loop with Ras/ERK/FoxM1/Nrf2 to promote hepatic tumorigenesis.

Expression of cyclooxygenase-2, peroxiredoxin I, peroxiredoxin 6 and nuclear factor-κB in oral squamous cell carcinoma

Tumor development and progression are multistep processes that involve local tumor growth and invasion, followed by metastasis. The aggressiveness of the tumor is the major determinant of the mortality of oral cancer patients. The present study investigates whether the expression levels of cyclooxygenase-2 (COX-2), nuclear factor-κB (NF-κB), peroxiredoxin 1 (PRDX1) and PRDX6 are associated with the development, proliferation, differentiation and recurrence of oral squamous cell carcinoma (OSCC). The mRNA expression levels of COX-2, NF-κB, PRDX1 and PRDX6 were examined in 50 OSCC specimens and 19 normal oral mucosae by quantitative polymerase chain reaction (qPCR). qPCR analysis showed that the mRNA levels of COX-2 in OSCC were significantly higher than those in the normal oral mucosae (P=0.021). The expression levels of PRDX1 in high-stage tumors (T3 and T4) were significantly elevated compared with those in low-stage tumors (T1) (P=0.047). Additionally, the expression levels of NF-κB in the high-grade tumor were significantly elevated compared with those in the low-grade tumors (P=0.030). Overall, it was indicated that the expression of COX-2 is strongly associated with the development of OSCC. Moreover, the enhanced expression of PRDX1 and NF-κB may function in the progression of OSCC, which serves as a useful marker for prognosis in patients with oral cancer.