HOXA5 inhibits keratinocytes growth and epidermal formation in organotypic cultures in vitro and in vivo.
ABSTRACT Homeobox transcription factors play important roles in epidermal renewal. Among them HOXA5 emerges as a promising member. However, its direct effect on epidermal biology, either to promote or to inhibit growth, is still controversial.
We proposed to unravel the role of HOXA5 in modulating keratinocytes growth and epidermal formation in organotypic cultures both in vitro and in vivo.
We transfected HaCaT cells with lentivirual vectors which over-expressed either wild-type or mutant HOXA5 cDNAs with deleted homeodomain. Subsequently we propagated the cells in organotypic cultures (OTCs) and then transplanted them into nude mice. Cell proliferation and cell cycle progression were detected. Epidermal morphogenesis and stratification were investigated by immunohistochemistry and immunofluorescence staining of a series of epidermal markers.
HaCaT cells transfected with HOXA5 cDNAs displayed lower growth rate and delayed G1-S transition. HOXA5-transfected OTC exhibited an aberrantly organized epithelium with significantly increased TUNEL staining as well as decreased PCNA and K5 staining, while expression of differentiation markers as K10, involucrin and filaggrin were somewhat enhanced. However, under in vivo environment in nude mice which had great paracrine regulatory mechanisms, the aberrant phenotype was ameliorated as shown by a more regular tissue organization and normal expression of PCNA and K5. Inversely, cells transfected with the homeodomain-deleted protein exhibited accelerated growth and produced a more proliferative and better-orchestrated epidermis, as shown by well-expressed proliferation and differentiation markers.
HOXA5 can suppress keratinocytes growth and epidermal formation. It probably activated antagonist genes against growth factors release, which depends on its homeodomain.
- SourceAvailable from: Caroline Schild-Poulter[show abstract] [hide abstract]
ABSTRACT: RanBPM is a ubiquitous protein that has been reported to regulate several cellular processes through interactions with various proteins. However, it is not known whether RanBPM may regulate gene expression patterns. As it has been shown that RanBPM interacts with a number of transcription factors, we hypothesized that it may have wide ranging effects on gene expression that may explain its function. To test this hypothesis, we generated stable RanBPM shRNA cell lines to analyze the effect of RanBPM on global gene expression. Microarray analyses were conducted comparing the gene expression profile of Hela and HCT116 RanBPM shRNA cells versus control shRNA cells. We identified 167 annotated genes significantly up- or down-regulated in the two cell lines. Analysis of the gene set revealed that down-regulation of RanBPM led to gene expression changes that affect regulation of cell, tissue, and organ development and morphology, as well as biological processes implicated in tumorigenesis. Analysis of Transcription Factor Binding Sites (TFBS) present in the gene set identified several significantly over-represented transcription factors of the Forkhead, HMG, and Homeodomain families of transcription factors, which have previously been demonstrated as having important roles in development and tumorigenesis. In addition, the combined results of these analyses suggested that several signaling pathways were affected by RanBPM down-regulation, including ERK1/2, Wnt, Notch, and PI3K/Akt pathways. Lastly, analysis of selected target genes by quantitative RT-qPCR confirmed the changes revealed by microarray. Several of the genes up-regulated in RanBPM shRNA cells encode proteins with known oncogenic functions, such as the RON tyrosine kinase, the adhesion molecule L1CAM, and transcription factor ELF3/ESE-1, suggesting that RanBPM functions as a tumor suppressor to prevent deregulated expression of these genes. Altogether, these results suggest that RanBPM does indeed function to regulate many genomic events that regulate embryonic, tissue, and cellular development as well as those involved in cancer development and progression.American journal of cancer research. 01/2012; 2(5):549-65.