Analysis of the regulation of fatty acid binding protein 7 expression in human renal carcinoma cell lines

Naohisa Takaoka,Seiichiro Ozono,Takayuki Sugiyama,Soichi Mugiya,Tatsuya Takayama,Takumi Teratani

doi:10.1186/1471-2199-12-31

Abstract

BackgroundImproving the treatment of renal cell carcinoma (RCC) will depend on the development of better biomarkers for predicting disease progression and aiding the design of appropriate therapies. One such marker may be fatty acid binding protein 7 (FABP7), also known as B-FABP and BLBP, which is expressed normally in radial glial cells of the developing central nervous system and cells of the mammary gland. Melanomas, glioblastomas, and several types of carcinomas, including RCC, overexpress FABP7. The abundant expression of FABP7 in primary RCCs compared to certain RCC-derived cell lines may allow the definition of the molecular components of FABP7's regulatory system.ResultsWe determined FABP7 mRNA levels in six RCC cell lines. Two were highly expressed, whereas the other and the embryonic kidney cell line (HEK293) were weakly expressed FABP7 transcripts. Western blot analysis of the cell lines detected strong FABP7 expression only in one RCC cell line. Promoter activity in the RCC cell lines was 3- to 21-fold higher than that of HEK293. Deletion analysis demonstrated that three FABP7 promoter regions contributed to upregulated expression in RCC cell lines, but not in the HEK293 cell. Competition analysis of gel shifts indicated that OCT1, OCT6, and nuclear factor I (NFI) bound to the FABP7 promoter region. Supershift experiments indicated that BRN2 (POU3F2) and NFI bound to the FABP7 promoter region as well. There was an inverse correlation between FABP7 promoter activity and BRN2 mRNA expression. The FABP7-positive cell line's NFI-DNA complex migrated faster than in other cell lines. Levels of NFIA mRNA were higher in the HEK293 cell line than in any of the six RCC cell lines. In contrast, NFIC mRNA expression was lower in the HEK293 cell line than in the six RCC cell lines.ConclusionsThree putative FABP7 promoter regions drive reporter gene expression in RCC cell lines, but not in the HEK293 cell line. BRN2 and NFI may be key factors regulating the expression of FABP7 in certain RCC-derived cell lines.

Highlights

Improving the treatment of renal cell carcinoma (RCC) will depend on the development of better biomarkers for predicting disease progression and aiding the design of appropriate therapies
Two RCC cell lines (OS-RC-2 and TUHR14TKB) exhibited strong fatty acid binding protein 7 (FABP7) expression, in contrast to four other RCC cell lines (769-P, 786-O, ACHN and Caki-1) and a human embryonic kidney cell line (HEK293). These results differ from our analysis of primary RCCs, which expressed FABP7 at high frequency (80%) [7]
There was an inverse correlation between FABP7 promoter activity (Figure 1B) and BRN2 mRNA expression (Figure 7A), in HEK293s and RCCs

Summary

Introduction

Improving the treatment of renal cell carcinoma (RCC) will depend on the development of better biomarkers for predicting disease progression and aiding the design of appropriate therapies. One such marker may be fatty acid binding protein 7 (FABP7), known as B-FABP and BLBP, which is expressed normally in radial glial cells of the developing central nervous system and cells of the mammary gland. The abundant expression of FABP7 in primary RCCs compared to certain RCC-derived cell lines may allow the definition of the molecular components of FABP7’s regulatory system.

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Results

Discussion

Conclusion