MAPK3 and renal cell carcinoma: However, the role of ERK1/2 in the response to Sorafenib in RCC has been studied only in co-culturing resistant models for Sorafenib or Sunitinib [20,21], and no definitive conclusion about the role of MAPK in the primary response or in de novo resistance to Sorafenib in RCC has been established so far.