Effects of 5‑fluorouracil and class III phosphoinositide 3‑kinase small interfering RNA combination therapy on SGC7901 human gastric cancer cells.
The aim of the present study was to investigate the effects of small interfering RNA‑mediated inhibition of Class III phosphoinositide 3‑kinase (PI3K) signal transduction on the proliferation, apoptosis and autophagy of SGC7901 gastric cancer cells. The present study also aimed to examine the contribution of autophagic inhibition to the antitumor effects of 5‑fluorouracil (5‑FU). A PI3K(III)‑RNA interference (i)‑green fluorescent protein (GFP) recombinant replication adenovirus (AD) and the negative control (NC)‑RNAi‑GFP control AD were constructed and infected into SGC7901 cells. A methyl thiazolyl tetrazolium assay was used to determine the growth rate of the SGC7901 cells. Immunofluorescent staining was used to detect microtubule‑associated protein 1 light chain 3 expression. The mitochondrial membrane potential was measured using the JC‑1 fluorescent probe. Autophagic expression was monitored with MDC staining and transmission electron microscopy. The results revealed that following combination treatment of the SGC7901 gastric cancer cells with 5‑FU + PI3K(III)‑RNAi‑AD, the optical density absorbance values at 24, 48 and 72 h were 0.17 ± 1.64, 0.13 ± 4.64 and 0.11 ± 3.56%, respectively, with cell viability inhibition ratios of 45.89 ± 6.67, 72.57 ± 9.48 and 87.51 ± 4.65%, respectively. As compared with the other treatment groups, the inhibition rate in the combined treatment group was significantly higher (P<0.05). The percentages of the cells with green fluorescence in the combined treatment group were 74.4 ± 3.86 (24 h), 82.3 ± 1.84 (48 h) and 92.5 ± 1.1% (72 h), which were larger than those of the other groups. The percentage of cells with green fluorescence became larger, which indicated that the mitochondrion membrane potential had been reduced to a greater extent. MDC staining revealed that the number of autophagic vacuoles in the cells (measured at 24, 48 and 72 h) decreased gradually with time, with more autophagic vacuoles observed in the cells in the control group at 24 h than those in the other treatment groups. Fewest autophagic vacuoles were identified in the combined treatment group. Using a fluorescence microscope, the immune fluorescence expression of microtubule‑associated proteins 1A/1B light chain 3A, which is the specific protein of autophagy, in the combined treatment group was observed to be significantly downregulated, as compared with the other groups. As determined by transmission electron microscopic observation of the SGC7901 gastric cancer cells, the degree of autophagy in the combined treatment group was significantly reduced, as compared with that of the other treatment groups. In conclusion, following combined treatment with 5‑FU and an inhibitor of class III PI3K signal transduction, the proliferation of SGC7901 cells was significantly suppressed, the mitochondrion membrane potentials were significantly reduced and the expression levels of autophagic markers were significantly downregulated.
Department of General Surgery, The Second Affiliated Hospital, Soochow University, Suzhou, Jiangsu 215004, P.R. China.
Bao-Song
BS
Zhu
Department of General Surgery, The First Changshu Affiliated Hospital, Soochow University, Changshu, Jiangsu 215500, P.R. China.
Jia-Lei
JL
Sun
Department of General Surgery, The Second Affiliated Hospital, Soochow University, Suzhou, Jiangsu 215004, P.R. China.
Wei
W
Gong
Cyrus Tang Hematology Center, Soochow University, Suzhou, Jiangsu 215123, P.R. China.
Xing-Ding
XD
Zhang
Department of General Surgery, The Second Affiliated Hospital, Soochow University, Suzhou, Jiangsu 215004, P.R. China.
Yong-You
YY
Wu
Department of General Surgery, The Second Affiliated Hospital, Soochow University, Suzhou, Jiangsu 215004, P.R. China.
Chun-Gen
CG
Xing
D000256:Adenoviridae / Q000235:genetics; D000964:Antimetabolites, Antineoplastic / Q000008:administration & dosage / Q000494:pharmacology*; D001343:Autophagy / Q000187:drug effects / Q000235:genetics; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D002470:Cell Survival; D005472:Fluorouracil / Q000008:administration & dosage / Q000494:pharmacology*; D015870:Gene Expression; D005822:Genetic Vectors / Q000235:genetics; D006801:Humans; D008869:Microtubule-Associated Proteins / Q000235:genetics / Q000378:metabolism; D008928:Mitochondria / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D019869:Phosphatidylinositol 3-Kinases / Q000235:genetics*; D034622:RNA Interference; D012333:RNA, Messenger / Q000235:genetics*; D034741:RNA, Small Interfering / Q000235:genetics*; D013274:Stomach Neoplasms / Q000235:genetics* / Q000378:metabolism*; D014161:Transduction, Genetic; D014162:Transfection
D000964:Antimetabolites, Antineoplastic; D005472:Fluorouracil; D008869:Microtubule-Associated Proteins; D019869:Phosphatidylinositol 3-Kinases; D012333:RNA, Messenger; D034741:RNA, Small Interfering; C477012:MAP1LC3A protein, human