CD133 has been reported to be associated with chemoresistance in various
cancer cells. The efficacy of
5-fluorouracil (5-FU), an important chemotherapeutic agent for advanced
gastric cancer (GC), is limited by
5-FU resistance. Hence, the present study investigated the function of CD133 in
5-FU resistance in human GC cells. We isolated CD133+ GC cells by immunomagnetic cell sorting and CD133 expression was modulated by transfection of CD133 gene or CD133 small interfering
ribonucleic acid. To assess the
5-FU cytotoxicity, Cell Counting Kit-8 was used. Expression of CD133,
P-glycoprotein (P-gp),
B-cell lymphoma 2 (Bcl‑2),
Bcl-2-associated X protein (Bax), phospho-Akt (p-Akt) and phospho-p70S6
kinase (p-p70S6K) were analyzed by western blotting. CD133, P-gp, Bcl-2 and Bax messenger
ribonucleic acids were evaluated using semi-quantitative
reverse transcriptase-polymerase chain reaction. Cell apoptosis was assessed by
Hoechst 33258 staining. CD133+ cells were more resistant to
5-FU than CD133- cells, and showed higher expression of P-gp and Bcl-2 with lower expression of Bax. Furthermore, CD133 silencing enhanced
5-FU cytotoxicity and apoptotic characteristics, whereas CD133 overexpression increased
5-FU resistance. CD133 silencing and activation directly decreased and increased the expression of P-gp, Bcl‑2, p-Akt and p-p70S6K, respectively. Notably, Akt inhibition by
LY294002 restored the
5-FU cytotoxicity suppressed by CD133 overexpression, while Akt activation by
epidermal growth factor reversed the
5-FU cytotoxicity enhanced by CD133 silencing. Therefore, CD133 may inhibit 5-FU-induced apoptosis by regulating the expression of P-gp and Bcl-2 family mediated by
phosphoinositide 3-kinase/Akt/
p70S6K pathway in GC cells.