Therapy with transcutaneous administration of imiquimod combined with oral administration of sorafenib suppresses renal cell carcinoma growing in an orthotopic mouse model

Imiquimod is an imidazoquinoline immune response modifier that is used in antiviral and antiallergic creams. Combination therapy using transcutaneous imiquimod and oral sorafenib was previously demonstrated to reduce the tumor burden of renal cell carcinoma growing cutaneously in a mouse model. In the present study, an orthotopic mouse model was used to investigate whether combined treatment with oral sorafenib and transcutaneous imiquimod inhibited renal cell carcinoma growing in the kidney. Kidneys of female BALB/c mice were orthotopically implanted with RENCA mouse kidney cancer cells, and the mice were transcutaneously treated with cream containing imiquimod and/or with orally administered sorafenib 5 days following cell implantation. Tumor burden and incidence were determined 28 days following the start of therapy. Splenocyte activity was quantified using the ⁵¹Cr release assay and the fluorescence-activated cell sorting assay with cluster of differentiation (CD) 4 and CD8 antibodies. Imiquimod, sorafenib and combination therapy were tolerated well. A combination of transcutaneous imiquimod and oral sorafenib inhibited the growth of RENCA tumors in the kidney significantly compared with the control. The ⁵¹Cr release assay demonstrated that transcutaneous imiquimod therapy significantly induced the release of ⁵¹Cr from RENCA cells compared with the control. The fluorescence-activated cell sorting assay demonstrated that transcutaneous imiquimod therapy induced CD8⁺ and CD4^- splenocytes compared with the control. In summary, the results of the present study demonstrated that combined treatment with transcutaneous imiquimod and oral sorafenib may be a promising strategy for the treatment of patients with renal cell carcinoma.