Erk1 and Erk2 are central mediators of MAPK signaling pathway which plays a key role in proliferation and chemoresistance of cancer cells. However, the effect of Erk1 and Erk2 in these processes may not be the same. The aim of this study was to investigate differential effect of Erk1 and Erk2 down-regulation on chemoresistance in human hepatocellular carcinoma cells. Expression level and relative expression analysis in HepG2 cells were performed using RT-PCR and qRT-PCR, respectively.Phosphorylated-Erk1/2 and apoptosis analysis was performed by flow-cytometry technique.
The results showed a higher expression level of Erk2 relative to Erk1 in HepG2 cells(p<0.01). A significant decrease in phosphorylated-Erk1/2 and a compensational response was observed after Erk1 and/or Erk2 silencing using specific siRNAs (p<0.01). Furthermore, 5-FU chemotherapy following siRNA-mediated knockdown lead to a significant enhancement of chemosensitivity with a higher rate of early apoptosisin Erk2 silencing relative to that ofErk1) +9%, p<0.01). 5-FU treatment afterdual knockdown of Erk1/2 showed higherrate of early apoptosis relative to single Erk1 silencing(+9.25%, p<0.01) andalso higher rate of late apoptosiscompared to single Erk1 and Erk2 silencing(+4.96% and +4.66%, p<0.01).
Our data shows that liposomal siRNA-mediated down-regulation of Erk1/2 can lead to potent chemosensitizing effects in HepG2 cells. Moreover, a higher chemosensitivity following Erk2 downregulation than Erk1 downregulation may be associated with the higher expression of Erk2 in human hepatocellular carcinoma.
Dr.Amir Mehdizadeh