353 FROM DEVELOPMENT TO CANCER: INVOLVEMENT OF LIM-CLASS HOMEOBOX GENE LIM1 IN HUMAN RENAL CELL CARCINOMA

Article Outline

• INTRODUCTION AND OBJECTIVES
• METHODS
• RESULTS
• CONCLUSIONS
• Copyright

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INTRODUCTION AND OBJECTIVES 

Human renal cell carcinoma (RCC) remains resistant to therapies. The Lim1 transcription factor is required for normal organogenesis, including nephrogenesis, through the regulation of cell growth and differentiation. The hypothesis that signaling pathways and transcription factors acting normally during development are reactivated during tumorigenesis is more and more confirmed in various cancers. In the kidney it is for example the case for Pax2/8 transcription factors and Notch signaling. So far, no study has assessed whether the reactivation of Lim1 may be associated with kidney tumorigenesis.

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METHODS 

A panel of conventional RCC (CCC) cell lines expressing or not the von Hippel-Lindau (VHL) tumor suppressor gene as well as tumors and normal corresponding tissues from CCC patients were used. The activation of Lim1 in cells and tumor/normal pairs was investigated by real-time RT-PCR and Western blot. Lim1 was silenced using 3 different Lim1 targeting siRNAs. The effects of Lim1 silencing on cell proliferation, cell death, cell migration and senescence were measured by cell counting and BrdU incorporation studies, FACS analysis, wound assays and SA-βGal staining, respectively. The activation status of the tumorigenic signaling pathways PI3K/Akt, NF-kB and MAPK, as well as the interactions with the sonic hedgehog pathway was measured by Western blot and specific inhibitors. Human RCC tumor-bearing nude mice were treated during 3 weeks with siRNA targeting Lhx1. Tumor cell proliferation, death and vascularization were measured by Ki67, TUNEL and CD40 staining, respectively.

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RESULTS 

We show that Lim1 is specifically reexpressed in tumor cells and tumors compared to normal tissues. In cells transiently depleted in Lim1, proliferation and motility were both decreased by 60%. These observations were made independently of VHL expression. No differences in apoptosis or senescence were observed. The activation of MAPK pathway as well as the expression of Gli1 factor were shown to be linked to Lim1 expression. Cross-talk with additional oncogenic pathways as well as the in vivo effect of Lim1 silencing in nude mice are currently under investigation.

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CONCLUSIONS 

These findings show that the Lim1 is reexpressed in adult kidney tumor and that targeting this transcription factor may have therapeutic potential in human CCC.