Functional transformation of N-myc downstream-regulated gene 4 in gastric cancer cells under oxygen stress

Abstract

Objective To investigate the influence of hypoxia on the function of N-myc downstream-regulated gene 4 (NDRG4) in gastric cancer cells. Methods The hypoxia model in gastric cancer cells was constructed to investigate the effect of hypoxia on metastasis of gastric cancer cells using scratch healing assay and Transwell assay. The mRNA and protein expression levels of NDRG4 in gastric cancer cells subjected to hypoxia were also detected using Western blotting and reverse transcriptase-polymerase chain reaction (RT-PCR) respectively. NDRG4 overexpression was conducted in gastric cancer cells and the effect of NDRG4 on malignant phenotype of gastric cancer cells was explored through scratch healing assay, Transwell assay, cell growth curve and clone formation test under normoxic conditions. Results Hypoxia could obviously enhance the metastasis capability of gastric cancer cells. As compared with the normoxic state, the number of invasive cells in both BGC-823 and MGC-803 subjected to hypoxia for 24 h was notably increased (174.20±9.04 vs. 48.20±11.76, and 229.00±34.22 vs. 28.75±2.50, respectively, both P=0.000). Besides, hypoxia could also significantly increase the scratch healing rate in both BGC-823 and MGC-803 cells [(25.00±0.02)% vs. (15.69±0.04)%, and (32.03±0.04)% vs. (11.90±0.04)% respectively, P=0.025, 0.006 respectively]. Accompanied with enhanced metastasis potential of gastric cancer cells induced by hypoxia for 24 h, the protein level of NDRG4 was dramatically increased. However, the ectopic overexpression of NDRG4 could dramatically inhibit the metastasis capacity, sustain cell proliferation and decrease the clone-forming ability under the normoxic condition. Conclusion Upregulation of NDRG4 induced by hypoxia might play an important role during the progression of gastric cancer trigged by hypoxia. We suspected that abnormal accumulation and functional protein modification of NDRG4 induced by hypoxia maybe contribute to the function changes of NDRG4 under different oxygen concentrations. Key words: Gastric cancer; N-myc downstream-regulated gene 4; Hypoxia; Metastasis