Background: Interferon (IFN) alpha is one of the central agents in immunotherapy for renal cell carcinoma (RCC). It acts by binding to the IFN-alpha receptor (IFNAR). We previously reported that increased tumor expression of IFNAR2 mRNA was associated with the metastatic potential and progression of RCC, as well as with a poor response of metastatic RCC to IFN-alpha therapy. This study investigated the influence of serum IFNAR2 in RCC patients.
Methods: We measured serum IFNAR2 mRNA levels and quantified IFNAR mRNA expression in paired tumor and non-tumor tissues from the surgical specimens of 66 consecutive RCC patients by the real-time reverse transcription polymerase chain reaction (RT-PCR). We also measured phosphorylated Akt (Ser-473) and phosphorylated-S6 ribosomal protein (Ser-235/236) proteins levels in paired tumor and non-tumor tissues of patients with metastatic RCC by Western blotting.
Results: The serum level of IFNAR2 mRNA was not associated with its tumor tissue level. Serum IFNAR2 mRNA was positively correlated with tumor size (P < 0.05), but not with tumor grade, pT stage, metastasis, microscopic vascular invasion, or serum C-reactive protein. Serum levels of IFNAR2 mRNA were significantly higher in patients with a good response to IFN-alpha ± sorafenib than in those with a poor response (P < 0.0001). Tumor tissue IFNAR2 mRNA levels and phosphorylated-S6 ribosomal protein (Ser-235/236) levels were associated with metastatic potential (P < 0.001 and P < 0.01, respectively), and patients with a low IFNAR2 mRNA level and low phosphorylated Akt (Ser-473) protein level in the primary tumor showed a good response to IFN-α ± sorafenib (IFN-α ± Sor: CR-PR) (P < 0.01 and P < 0.05, respectively). Kaplan-Meier survival analysis showed that a higher serum IFNAR2 mRNA level was associated with longer overall survival of treated patients (P < 0.05), while a higher tumor tissue IFNAR2 mRNA level was related to shorter overall survival (P < 0.01).
Conclusions: Our findings suggest that a high serum level of IFNAR2 mRNA may be a useful marker for predicting the response of metastatic RCC to IFN-alpha ± sorafenib therapy.