Background and purpose: Multidrug resistance (MDR) is the dominating obstacle to the chemotherapy. There is strong evidence that the phosphoinositide 3-kinases (PI3Ks) signaling pathway is involved in MDR phenotype

however

the mechanism of MDR occurrence is still unknown. This study tended to investigate the regulating effect of PI3K/Akt signaling pathway and its downstream target genes in P-glycoprotein (P-gp) (ABCB1 gene encoding)-mediated MDR in human colon carcinoma HCT-116/L-OHP cells. Methods: Pretreatment with PI3K selective inhibitor LY294002 (20 μmol/L) for 2 h

the sensitivity of L-OHP was evaluated by the CCK-8 (cell counting kit-8) assay in HCT-116/L-OHP cells

and the expressions of P-gp

LRP

MRP-2

Akt

p-Akt

IκB and p-IκB were evaluated by Western blot. The activity of ABCB1 promoter was evaluated by chromatin immunoprecipitation analysis (CHIP). Results: After inhibiting the activity of PI3K/Akt signaling pathway

the IC50 value of L-OHP decreased from(157.48±16.73) μg/mL to (53.68±3.18) μg/mL in HCT-116/L-OHP cells

and the reversal index was 2.93 (P0.01). The expressions of P-gp

p-Akt and p-IκB were down-regulation compared with the concrol group (P0.01)

but the expressions of LRP

MRP-2

Akt and IκB didn't change significantly. CHIP result has confirmed that NF-κB protein could bind to the region of ABCB1 gene promoter in HCT116/L-OHP cells. Conclusion: Blocking of PI3K/Akt/NF-kB signal pathway could increase the drug sensitivity to MDR cells

inhibit the phosphorylation of p-Akt and p-IκB

and reversing ABCB1/P-glycoprotein–mediated multidrug resistance in colon carcinoma cells.