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.

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

We analyzed the correlation between interferon-alpha (IFNalpha) response and gene expression profiles to predict IFNalpha sensitivity and identified key molecules regulating the IFNalpha response in renal cell carcinoma (RCC) cell lines. To classify eight RCC cell lines of the SKRC series into three subgroups according to IFNalpha sensitivity, that is, sensitive, resistant and intermediate group, responses to IFNalpha (300-3000 IU/mL) were quantified by WST-1 assay. Microarray, followed by supervised hierarchical clustering analysis, was applied to selected genes according to IFNalpha sensitivity. In order to find alteration of expression profiles induced by IFNalpha, sequential microarray analyses were performed at 3, 6, and 12 h after IFNalpha treatment of RCC cell lines and mRNA expression level was confirmed using quantitative real time polymerase chain reaction. According to the sequential microarray analysis between IFNalpha-sensitive and -resistant line, seven genes were selected as candidates for IFNalpha-sensitivity-related genes in RCC cell lines. Among these seven genes, we further developed a model to predict tumor inhibition with four genes, that is, adipose differentiation-related protein, microphthalmia associated transcription factor, mitochondrial tumor suppressor 1, and troponin T1 using multiple linear regression analysis (coefficient=0.948, P=0.0291) and validated the model using other RCC cell lines including six primary cultured RCC cells. The expression levels of the combined selected genes may provide predictive information on the IFNalpha response in RCC. Furthermore, the IFNalpha response to RCC might be modulated by regulation of the expression level of these molecules.

Gene expression profiles correlate with the morphology and metastasis characteristics of renal cell carcinoma cells.

Renal cell carcinoma (RCC) shows various clinical behaviors, and currently surgical modalities are the only effective therapy against this cancer. To discern the genomic background affecting clinical characteristics such as metastasis, we analyzed the gene expression profiles of the RCCs by DNA microarray using cell lines originating from primary or metastatic lesions. RNA was extracted from ten SKRC RCC cell lines and gene expression profiling was performed using a cDNA microarray of nearly 4,000 human cDNA clones. We compared the gene expression profiles between these SKRC cell lines and the normal renal proximal tubular cell line and among SKRC cell lines that showed different characteristics. The clustering of the selected 62 genes revealed similar profiling patterns between SKRC-17 and SKRC-29 cells that were derived from metastatic RCC lesions. Another cell line from a metastatic lesion, SKRC-52, with a unique spindle-shaped morphology, had a different pattern of expression profiling from the other cell lines. We found several genes up-regulated in the cell lines from metastatic lesions; transgelin, which is reportedly involved in cell proliferation and migration, was up-regulated in SKRC-52. The unique profiling pattern of gene expression clearly correlated with cell morphology and metastatic potential. Such profiling might contribute to identifying the genes involved in the clinical characteristics of RCC.

Telomerase is upregulated in irreversible preneoplastic lesions during bladder carcinogenesis in rats.

Multiple occurrence or recurrence after transurethral resection is an important characteristic of superficial bladder tumors. To study bladder carcinogenesis, we focused on detection of telomerase activation, which was investigated in several human cancers, including bladder tumors. We experimentally examined the telomerase activity during bladder carcinogenesis, especially in precancerous lesions, induced by N-butyl-N-(4-hydroxybutyl)nitrosamine (BBN) in rats. Male Wistar rats were given 0.05% BBN in water from the age of 8 weeks to 24 weeks. Subgroups were euthanized at 4, 8, 10, 12, 18, and 24 weeks after BBN administration. Using the stretch PCR method, telomerase activity was semiquantified in exfoliated bladder epithelial cells. In addition, telomere length in each subgroup was measured by southern hybridization for the terminal restriction fragment using a (TTAGGG)(4) probe. Statistical analyses were performed using analysis of variance and Fisher's PLSD test. Epithelial cells of normal bladder in the control groups and those of diffuse hyperplasia, which was a reversible change at 4 weeks, expressed no telomerase activity. In contrast, telomerase activity significantly increased in the stage after nodular hyperplasia, an irreversible change at 8 weeks, then elevated with carcinogenesis. However, telomere length was still preserved by the 12th week, and was shortened at 18 and 24 weeks. These results suggest that telomerase activation is probably induced independent of telomere shortening during bladder carcinogenesis in the rat, and might be a biological tumor marker of irreversible preneoplastic lesions, which evolve into bladder tumors in the rat.