SLC1A5 Silencing Inhibits Esophageal Cancer Growth via Cell Cycle Arrest and Apoptosis

Abstract

Background/aims: Solute-linked carrier family A1 member 5 (SLC1A5), which has high affinity to neutral amino acids, is essential for glutamine transport and amino acid metabolism in various cancers. However, the role of SLC1A5 in esophageal cancer has not been reported.

Methods: SLC1A5 expression in esophageal cancer tissues was detected by immunohistochemistry and western blotting. The effects of SLC1A5 knockdown on the growth, cell cycle, viability, and glutamine metabolism of esophageal cancer cells were investigated with flow cytometry and western blotting. Furthermore, the consequences of SLC1A5 knockdown on tumor growth and survival were also evaluated in vivo using mice carrying esophageal cancer xenografts.

Results: SLC1A5 was expressed in 86.5% (32/37) of the cancer tissues from esophageal cancer patients. Moreover, SLC1A5 expression in the cancerous tissues was significantly higher than that in the paired adjacent normal tissues. SLC1A5 knockdown with siRNA (PZ siRNA) in TE-1 cells in vitro significantly decreased cell growth and reduced both leucine and glutamine transport, leading to inhibition of mTORC1 signaling. Additionally, siRNA-mediated SLC1A5 knockdown resulted in cell cycle arrest and apoptosis of TE-1 cells. The survival rate of athymic (nu/nu) male nude mice carrying tumors formed from TE-1 cells transfected with SLC1A5 siRNA (PZ siRNA) was also significantly improved compared with mice carrying tumors formed from TE-1 cells transfected with control siRNA. Tumor size/weight was also significantly lower for the former mice group of mice.

Conclusion: Our data indicate that SLC1A5 plays an important role in esophageal cancer both in vivo and in vitro. The inhibition of esophageal cancer growth by targeting SLC1A5 could, therefore, be used as a preoperative therapy for esophageal cancer.

Keywords: Esophageal cancer; Glutamine; MTORC1; Slc1a5.