Suppression of SOCS3 increases susceptibility of renal cell carcinoma to interferon-α.

Interferon (IFN)-α is one of the most commonly used agents in immunotherapy for patients with advanced stage renal cell carcinoma. However, because of the drug resistance to IFN-α, its benefits are limited. In this study, we examined whether repression of suppressor of cytokine signaling (SOCS) proteins, which are involved in the IFN-induced signaling pathway, can overcome the IFN resistance of renal cell carcinoma. The effect of IFN-α on SOCS3 expression and cell proliferation was examined using IFN-resistant 786-O and IFN-sensitive ACHN cell lines. The effects of SOCS3-targeted siRNA on 786-O xenografts were determined by SOCS3 expression, morphological observation, and tumor volume. The SOCS3 mRNA expression level was significantly increased by IFN-α stimulation in 786-O, but not in ACHN cells. The overexpression of SOCS3 by gene transfection in ACHN cells significantly inhibited the growth-inhibitory effect of IFN-α. Suppression of SOCS3 expression in 786-O cells by siRNA activated the IFN signaling pathway through signal transducer and activator of transcription 1 phosphorylation and recovered sensitivity to IFN-α. An in vivo study indicated that co-administration of SOCS3-targeted siRNA promoted IFN-α-induced cell death and growth suppression in 786-O cell xenograft in nude mice. Morphological observation of the tumors revealed the inhibition of SOCS3-induced apoptosis, invasion of inflammatory cells and fibrosis. SOCS3 could be a key component in the resistance to IFN treatment of renal cell carcinoma. Silencing SOCS3 gene expression could be an effective strategy to enhance the antitumor effect of IFN in human renal cell carcinoma cells.

Humanised antihuman IL-6R antibody with interferon inhibits renal cell carcinoma cell growth in vitro and in vivo through suppressed SOCS3 expression.

Interleukin-6 (IL-6), one of the proinflammatory cytokines, is considered to be one of the factors associated with poor prognosis of patients with renal cell carcinoma (RCC). Suppressor of cytokine signalling-3 (SOCS3) is rapidly up-regulated by IL-6 and a negative regulator of cytokine signalling. SOCS3 not only suppresses cytokine-mediated JAK/STAT signalling, but also sustains MAPK pathways. In our study, among the RCC cell lines, IL-6 mRNA expression was the highest in the 786-O cells, which also showed the highest level of SOCS3 mRNA expression under the condition of interferon stimulation. In contrast, ACHN cells had the lowest expression of both IL-6 and SOCS3 mRNA under the same condition. Our study is undertaken to evaluate the effect of humanised antihuman IL-6 receptor (IL-6R) antibody, which completely neutralises IL-6 activity, in RCC cell proliferation and its effect on signalling pathways. IL-6R antibody, tocilizumab, significantly suppressed cell proliferation in 786-O cells with interferon stimulation. Western blot analysis revealed that the tocilizumab enhanced the interferon-induced phosphorylation of STAT1 and inhibited SOCS3 expression and the phosphorylation of both STAT3 and ERK. In contrast, the IL-6 inhibited STAT1 phosphorylation, enhanced STAT3 phosphorylation and accelerated cell proliferation in ACHN cells. The in vivo effects of combination therapy with tocilizumab and interferon showed significant suppression of 786-O tumour growth in a xenograft model. Morphological observation of the tumours revealed the apoptosis, invasion of inflammatory cells and fibrosis. These findings suggest that combination therapy using an antihuman IL-6R antibody with interferon may represent a novel therapeutic approach for the treatment of RCC.