Objective: To investigate the expressions of liver X receptor α (LXRα) and proteasome activator 28γ (PA28γ) in gastric cancer and their effects on the growth of gastric cancer cells. Methods: The mRNA and protein expressions of LXRα and PA28γ in 35 specimens of gastric cancer and paired adjacent tissue were determined by qRT-PCR and immunohistochemical staining. The relations of their protein expressions with the clinicopathologic factors of the patients, and their correlationship were analyzed. In gastric AGS cells after overexpression with LXRα, the changes in cell cycle, growth in nude mice and expressions of LXRα and that of PA28γ were analyzed by flow cytometry, qRT-PCR and Western blot, respectively. Results: Both mRNA and protein expressions of LXRα were significantly decreased, and both mRNA and protein expressions of PA28γ were significantly increased in gastric cancer tissue compared with adjacent tissue (all P<0.05); the expressions of either LXRα or PA28γ showed no significant associations with the main clinicopathologic factors of the gastric cancer patients (all P>0.05); there was a significant negative correlation between LXRα and PA28γ protein expressions in gastric cancer tissue (r=–0.452, P=0.006). In gastric AGS cells after overexpression with LXRα, the LXRα mRNA expression was significantly increased, while the mRNA and protein expressions of PA28γ were significantly reduced, the cell cycle process was significantly blocked, the growth in nude mice was significantly suppressed, with significantly up-regulated mRNA and protein expressions of LXRα and down-regulated mRNA and protein expressions of PA28γ in the tissue of the transplanted tumor (all P<0.05). Conclusion: LXRα expression is down-regulated in gastric cancer with synchronous up-regulated PA28γ expression, and their growth and decline may probably regulate the growth of gastric cancer cells through affecting the cell cycle process.