Effect of mitogen-activated protein kinase signal transduction pathway on multidrug resistance induced by vincristine in gastric cancer cell line MGC803

AIM:To investigate the correlation between mitogen-activated protein kinase (MAPK) signal transduction pathway and multidrug resistance (MDR) in MGC803 cells.METHODS:Western blot was used to analyze the expression of MDR associated gene in transient vincristine (VCR) induced MGC803 cells, which were treated with or without the specific inhibitor of MAPK, PD098059.Morphologic analysis of the cells treated by VCR with or without PD098059 was determined by Wright-Giemsa staining. The cell cycle analysis was performed by using flow cytometric assay and the drug sensitivity of MGC803 cells which were exposed to VCR with or without PD098059 was tested by using MTT assay.RESULTS:Transient exposure to VCR induced P-gp butnot MRP1 or GST-π expression in MGC803 cells and the expression of P-gp was inhibited by PD098059.Apoptotic bodies were found in the cells treated with VCR or VCR+PD098059. FCM results indicated that more MGC803 cells showed apoptotic phenotype when treated by VCR and PD098059 (rate:31.23%) than treated by VCR only (rate:18.42%) (P<0.05).The IC50(284±13.2 μg/L) of MGC803 cells pretreated with VCR was 2.24-fold as that of negative control group (127±17.6μg/L) and 1.48-fold as that of the group treated with PD098059 (191±27.9μg/L).CONCLUSION:This study shows that the expression of P-gp can be induced by transient exposure to VCR and this induction can be prevented by PD098059, which can block the activity of MAPK. MAPK signal transduction pathway may play some roles in modulating MDR1 expression in gastric cancer.

Ability of a Specific ERK Signal-Pathway Inhibitor to Reverse P-Glycoprotein- Mediated Vincristine Resistance in Colon Cancer Cell Unes

OBJECTIVE To investigate the effect of a specific inhibitor PD098059 of the extracellular-signal regulated protein kinase (ERK) pathway on the P-glycoprotein (P-gp)-mediated resistance of colon cancer cell lines SW480/VCR and CoLo205NCR.METHODS SW480NCR and CoLo205NCR cells were generated byexposuring SW480 and CoLo205 cells to vincristine (VCR) (30 ng/ml) for 72h, which resulted in a comparatively higher level of P-gp expression.Western blotting was used to analyze P-gp, MRP, LRP, GST-'rr and TOPOIIexpression after exposuring the SW480 and CoLo205 cells to VCR (30 ng/ml)for 72 hrs. P-gp and pERK1/2 expressions was analyzed in SW480NCR andCoLo205/VCR cells treated with or without the specific inhibitor of MEK,PD098059. The MTT assay was used to determine the susceptibility ofSW480NCR and CoLo205NCR cells to VCR, treated with or withoutPD098059.I^F.SULI"S The results showed that VCR induced a comparatively higher levelof P-gp expression in the cell lines, but not that of MRP, LRP, GST-n- orTOPOII. P-gp expression levels were depressed significantly in SW480/VCR and COLO205/VCR cells by the specific inhibitor of MEK, PD098059.The IC50 (248 +19.6 and 215 +10.7 ng/ml) to VCR of SW480/VCR andCoLo205/VCR cells exhibited a 2.16 and 2.03-fold higher resistancecompared to the negative control group (SW480 and CoLo205 cells)(115+15.6 and 106 +11.9 ng/ml), but a 1.35 and 1.21 -fold higher resistance thanthe group treated with VCR (30 ng/ml)+ PD098059 (184 + 21.8 and 177+19.4 ng/ml).CONCLUSION This study shows that the expression of P-gp can beinduced by exposuring cells to VCR, and that this induction can be reversedby inhibiting the ERK signaling pathway at the point of MEK by its specificinhibitor, PD098059. The ERK signal-transduction pathway may play a rolein modulating mdrl expression in colon cancer.