Prediction of in vitro response to interferon-alpha in renal cell carcinoma cell lines

Interferon-α induces G1 cell-cycle arrest in renal cell carcinoma cells via activation of Jak-Stat signaling

The purpose of this study was to clarify the mechanism of IFN-α resistance in RCC. The effects of IFN-α on induction of apoptosis and cell-cycle arrest were analyzed by flow cytometric analysis. Jak-Stat pathway components induced by IFN-α was evaluated using Western blotting. The results suggested that IFN-α caused growth inhibition of RCC cell lines via arrest in the G1 phase without inducing apoptosis. The resistance of RCC to IFN-α was associated with the low expression of Stat1. This study indicated that the Jak-Stat pathway should be considered a primary target for improving the response of RCC to IFN-α treatment.

Low expression of microphthalmia-associated transcription factor, a potential molecular target for interferon-alpha susceptibility, is associated with metastasis in renal cell carcinoma

We previously reported that microarray expression profiling identified several candidate genes in association with interferon-alpha (IFN-alpha) response in renal cell carcinoma (RCC) cell lines (Cancer Sci 2007; 98: 529). Among them, we focused on microphthalmia-associated transcription factor (MITF), because its expression profile correlated well with IFN-alpha-response status. In addition, we investigated the clinical significance of the expression level of MITF using surgical specimens. RNA was extracted from 14 RCC cell lines and 65 RCC samples and was used in this study. Transfection of MITF cDNA into IFN-alpha-resistant RCC cell lines resulted in elevation of MITF expression and acquisition of IFN-alpha-sensitivity by quantitative PCR and WST-8 assay, respectively. Statistical analysis revealed that low MITF mRNA expression in RCC samples was significantly correlated with the presence of metastasis and poor survival of the patient. However, the correlation between MITF expression and IFN-alpha response was not obvious in the clinical cases. MITF gene transfection elevated IFN-alpha-sensitivity in RCC cell lines, suggesting that this gene is a target molecule for modulation of the IFN-alpha response. Quantification of MITF mRNA expression might be clinically useful to predict metastasis and survival of patients with RCC.

Defective Jak-Stat activation in renal cell carcinoma is associated with interferon-alpha resistance

Chemotherapy is ineffective against metastatic renal cell carcinoma (RCC). Interferon (IFN)-alpha has become the most common agent used in clinical therapy to overcome this malignant tumor, although a satisfactory response has not been achieved and the mechanism of resistance of RCC to IFN-alpha remains unclear. The purpose of the present study was to evaluate the susceptibility of RCC cells to IFN-alpha and clarify the mechanism of IFN-alpha resistance in RCC. Six RCC cell lines and three types of IFN-alpha were used, and the expression, activation and effects of transfection of possible proteins or factors reported to be involved in IFN-alpha signaling were examined to clarify the mechanism of resistance. The results suggest that the resistance of RCC to IFN-alpha is associated with the lack of Jak1, Tyk2 and Stat1 expression and defective Jak-Stat activation, but not with a lack of IFN-alpha receptor, suppressors of cytokine signaling induction or other factors examined. Moreover, phosphorylation of Jak-Stat pathway components and reversion of IFN-alpha resistance in RCC were observed upon transfection with Jak1, Tyk2 or Stat1 vector. These results suggest that restoring the expression of Jak or Stat1 might strikingly increase the susceptibility of RCC to IFN-alpha and may be a new strategy for improving the response of RCC to IFN-alpha treatment. The Jak-Stat pathway should therefore be an appropriate target for the treatment of RCC.