VEGFA and nonpapillary renal cell carcinoma: Furthermore, we found that the serum sIL-2R level remained nearly constant when RCC showed a good response to IFN-alpha with sequential VEGF-targeting therapy, while sIL-2R began to increase when resistance to therapy developed, indicating that monitoring serum sIL-2R may help to assessing tumor activity (at least in patients with ccRCC).