Gastric cancer is a common
tumor of the digestive system, which can occur in any part of the stomach.
Kallikrein 6 (KLK6) is a
trypsin-like serine protease and has been found to be involved in extracellular matrix remodeling,
tumor invasion and nervous system plasticity. Our previous study reported that KLK6 suppressed HGC-27
gastric cancer cell growth by inhibiting epithelial-mesenchymal transition; however, the mechanism of action underlying the effect of KLK6 still remains unclear. The aim of the present study was to investigate the effect and the underlying mechanism of KLK6 on stem cell-like properties and metabolism in gastric
carcinoma cells. The HGC-27 cell line was transfected with KLK6 overexpression (OV-KLK6) and interference (short hairpin-KLK6) vectors, then the transfection efficiency was confirmed using western blot analysis and reverse transcription-quantitative PCR. The percentage of CD133+ and CD44+ cells was detected using flow cytometry, while the
protein expression levels of the stem-associated genes, Nanog, Oct-4, SOX2 and Notch1, the metabolic markers,
hexokinase (HK)1, HK2, GLUT1, and the
proteins within the PI3K signaling pathway, phosphorylated (p)-PI3K, p-AKT and p-mTOR, were determined using western blot analysis. Biochemical kits were used to measure
ATP production,
lactic acid content and
glucose uptake. A tumorigenicity assay was performed with nude mice to detect gastric
tumor volume, and the
protein expression level of Oct-4, Nanog, HK1, HK2 and GLUT1, and the
mRNA expression level of KLK6 was also determined in gastric
tumor tissues of mice. Compared with that in the control group, KLK6
protein and
mRNA expression levels were significantly decreased in the four sh-
RNA groups (P<0.05). Among them, sh-RNA-3 induced the lowest KLK6 expression and was used to silence KLK6 in subsequent experiments. Compared with that in the control and negative control groups, the percentage of CD133+ and CD44+ cells, the
protein expression level of Oct-4, Nanog, HK1, HK2, GLUT1, p-PI3K, p-AKT and p-mTOR, and
ATP content,
lactic acid production,
glucose uptake and gastric
tumor volume were significantly decreased by sh-KLK6 (P<0.05), whereas KLK6 overexpression induced the opposite effect (P<0.05). In conclusion, KLK6 modulated stemness properties and cell metabolic profile in gastric
carcinoma cells and the mechanism may be associated with the PI3K/AKT/mTOR signaling pathway.