Blockage of Nrf2 suppresses the migration and invasion of esophageal squamous cell carcinoma cells in hypoxic microenvironment

Abstract

Nuclear factor erythroid-2-related factor 2 (Nrf2) is a critical cell protector by inducing phase two detoxifying and anti-oxidant enzymes in normal cells. But recently, numerous evidence show Nrf2 may play the same beneficial roles toward the cancer cells. Nrf2 is found upexpressed in lots of cancers and promote the proliferation and drug resistance. But studies about the role of Nrf2 in the metastases are few. It has been testified that the tumor cells are under hypoxic conditions. As an important anti-oxidant element, the expression of Nrf2 may be upregulated, which in turn promotes the tumor invasion and metastases in the hypoxic microenvironment. Our team found the expression of Nrf2 correlated with the lymph node metastasis of esophageal squamous cell carcinoma by pathological sections of esophageal carcinoma patients. Further, the mechanism beneath it was studied in this paper. It was hypothesized that the hypoxia microenvironment transformed Nrf2 a friend to a foe. First, Eca-109 cells were treated with different concentration of CoCl2 . Western blot and quantitative reverse transcription-polymerase chain reaction showed that with the increase of the concentration of CoCl2 , the expression levels of Nrf2 and hypoxia-inducible factor-1 (HIF-1) alpha were upregulated simultaneously. By analyzing the data, a significant correlation between Nrf2 and HIF-1 alpha in the protein levels was found. Further, blockage of Nrf2 mediated by shRNA suppressed the expression of HIF-1 alpha, hemeoxygenase-1 (HO-1), and matrix metalloproteinase 2 but enhanced the expression of E-cadherin. In addition, the results of wound healing and invasion assay-verified blockage of Nrf2 suppressed the migration and invasion. So it was suggested that blockage of Nrf2 repressed the migration and invasion of esophageal squamous cell carcinoma cells in the hypoxic microenvironment. HIF-1 alpha might be one of the downstream genes of Nrf2 regulated through Nrf2/HO-1 axis in the CoCl2 model. Nrf2 inhibition suppressed matrix metalloproteinase 2 and enhanced E-cadherin partly through HIF-1 alpha way.