These findings suggest that upstream signalling elements of ERK1/2, including gatekeeper mutations of PDGFRα, are not involved in the activation of ERK1/2 in pazopanib-resistant SS cells, and pazopanib-resistant clones are resistant to pazopanib inhibition of ERK1/2 phosphorylation. The gene discussed is MAPK3; the disease is synovial sarcoma.