Effects and Mechanism of Dihydroartemisinin on Malignant Behavior of Cisplatin-Resistant Gastric Cancer Cells

Background: Studies showed that dihydroartemisinin (DHA) has significant antitumor effects. However, there have been no relevant reports on gastric cancer resistance to DHA. Aim: To investigate the influence of DHA on the malignant behavior of cisplatin (DDP)-resistant gastric cancer cells SGC7901/DDP and the possible molecular mechanism. Methods: The IC50 of DHA against SGC7901/DDP cells at 48 h was obtained with CCK-8. DHA was used against SGC7901/DDP, with IC50 concentration at 0 µmol/L, 0.5-fold, onefold, and twofold respectively. Then the proliferation activity of SGC7901/DDP from day 1 to day 5 was detected by CCK-8. At 48 h after DHA treatment, we observed apoptosis, invasion, and migration, evaluated autophagy, and detected the expression level of protein related to the regulation of autophagy, apoptosis, angiogenesis and lymphangiogenesis with Western blot. The influence of DHA on cisplatin resistance of SGC7901/DDP was detected through sensitization test and the evaluation of p-gp expression level. Results: The IC50 concentration of DHA against SGC7901/DDP cells at 48 h is 70 µmol/L. DHA significantly inhibited the proliferation of SGC7901/DDP, which was time- and concentration-dependent (all P < 0.05). After having been treated for 48 h by increasing concentrations of DHA (0, 35, 70 and 140 µmol/L), the apoptosis rate increased and the penetrating cell number and scratch healing rate significantly decreased (all P < 0.05). The expression levels of Beclin1 and LC3-II/LC3-I which were corrected with autophagy, and the formation of autophagosomes and autophagous vacuoles increased in a concentration-dependent manner (all P < 0.05). The total PI3K, Akt, and mTOR expression levels did not significantly change, but their phosphorylated products (PI3P, p-Akt [Ser473], and p-mTOR) showed concentration-dependent decreases (all P < 0.05). The expression of caspases-8/9/3 protein significantly increased while the expression of VEGF-A、VEGF-C protein decreased (all P < 0.05). DHA could reverse the resistance of SGC7901/DDP cells to cisplatin after DHA treatment at a nontoxic dose (15.23 µg/mL) with a reversal rate of 2.95. After DHA treatment at different concentrations for 48 h, the expression of p-gp was significantly reduced in a concentration-dependent manner ( P < 0.05). Conclusion: DHA significantly inhibited proliferation, promoted programmed death, and had anti-invasion and antimetastatic effects on SGC7901/DDP cells, probably by upregulating autophagy-related Beclin1 and LC3-II expression and by inhibiting the antiautophagy signaling pathway PI3K/AKT/mTOR, thus promoting autophagic death. In addition, DHA induced caspase-dependent and mitochondrial pathway apoptosis in SGC7901/DDP cells, and reduced VEGF-A and VEGF-C activity to promote antiangiogenesis and antilymphangiogenesis. Furthermore, DHA effectively reversed the cisplatin resistance of gastric cancer cell by inhibiting p-gp expression.