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.

Ability of a specific ERK signal-pathway inhibitor to reverse P-glycoprotein-mediated vincristine resistance in colon cancer cell lines

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 CoLo205A/CR. Methods SW480/VCR and CoLo205/VCR cells were generated by exposuring SW480 and CoLo205 cells to vincristine (VCR) (30 ng/ml) for 72 h, which resulted in a comparatively higher level of P -gp expression. Western blotting was used to analyze P-gp, MRP, LRP, GST-π and TOPOII expression after exposuring the SW480 and CoLo205 cells to VCR (30 ng/ml) for 72 hrs. P-gp and pERK1/2 expressions was analyzed in SW480/VCR and CoLo205/VCR cells treated with or without the specific inhibitor of MEK, PD098059. The MTT assay was used to determine the susceptibility of SW480/VCR and CoLo205/VCR cells to VCR, treated with or without PD098059. Results The results showed that VCR induced a comparatively higher level of P-gp expression in the cell lines, but not that of MRP, LRP, GST-π or TOPOII. 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 and CoLo205/VCR cells exhibited a 2.16 and 2.03 -fold higher resistance compared 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 than the 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 be induced by exposuring cells to VCR, and that this induction can be reversed by inhibiting the ERK signaling pathway at the point of MEK by its specific inhibitor, PD098059. The ERK signal-transduction pathway may play a role in modulating mdr1 expression in colon cancer.