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Prostate cancer consists of secretory cells and a population of immature cells. The function of immature cells and their mutual relation with secretory cells are still poorly understood. Immature cells either have a hierarchical relation to secretory cells (stem cell model) or represent an inducible population emerging upon appropriate stimulation of differentiated cells. Hepatocyte Growth Factor (HGF) receptor c-MET is specifically expressed in immature prostate cells. Our objective is to determine the role of immature cells in prostate cancer by analysis of the HGF/c-MET pathway.Gene-expression profiling of DU145 prostate cancer cells stimulated with HGF revealed induction of a molecular signature associated with stem cells, characterized by up-regulation of CD49b, CD49f, CD44 and SOX9, and down-regulation of CD24 (‘stem-like signature’). We confirmed the acquisition of a stem-like phenotype by quantitative PCR, FACS analysis and Western blotting. Further, HGF led to activation of the stem cell related Notch pathway by up-regulation of its ligands Jagged-1 and Delta-like 4. Small molecules SU11274 and PHA665752 targeting c-MET activity were both able to block the molecular and biologic effects of HGF. Knock-down of c-MET by shRNA infection resulted in significant reduction and delay of orthotopic tumour-formation in male NMRI mice. Immunohistochemical analysis in prostatectomies revealed significant enrichment of c-MET positive cells at the invasive front, and demonstrated co-expression of c-MET with stem-like markers CD49b and CD49f.In conclusion, activation of c-MET in prostate cancer cells induced a stem-like phenotype, indicating a dynamic relation between differentiated and stem-like cells in this malignancy. Its mediation of efficient tumour-formation in vivo and predominant receptor expression at the invasive front implicate that c-MET regulates tumour infiltration in surrounding tissues putatively by acquisition of a stem-like phenotype.

We have isolated genomic clones from several members of the UV and TPA inducible human spr2 gene-family in order to analyse the regulation of these genes at a molecular level. From one of these members, the spr2-1 gene, we have identified and sequenced the regulatory region. By using CAT fusion plasmids and a liposome mediated transfection procedure we show that the isolated promoter region contains all the cis-elements necessary for induced expression after UV irradiation or phorbolester treatment of cultured human keratinocytes. Additionally the spr2-1 promoter is shown to be regulated aswell during the normal process of keratinocyte differentiation. This makes the spr2-1 promoter sequence an ideal tool to study the molecular mechanisms by which environmental agents such as UV radiation and chemical tumor promoters interfere with normal gene expression during cell proliferation and differentiation.

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By cytogenetic analysis, structural and numerical aberrations of chromosomes 1, 7, 8, 10, 16, and Y~ were identified in about 25% of the prostate carcinomas (PCs) studied. However, this figure is probably an underestimation of the true extent of the aberrations. This is because of selective isolation and preferential in vitro growth of nonmalignant prostate epitheliumY The use of interphase cytogenetic techniques for characterization of uncultured PC material has been stimulated by these findings. Application of in situ hybridization with centromere-specific DNA probes to fixed sections of PC has shown numerical aberrations for chromosomes 1,7,8,10,12,17,18, X, and y4~7 The finding of numerical aberrations in different chromosomes is not surprising because about 50% of the PCs have an aneuploid DNA content. 8 In the present study, the authors investigated numerical changes of chromosomes 1,7,8,10,18, and Y using fluorescence in situ hybridization (FISH) with centromere-specific DNA probes on nuclear suspensions of fresh tissue samples from 11 benign prostatic hyperplasia (BPH) and 43 PC patients. Selection of this chromosome panel was based on evidence from the literature and previous studies 9-a2 that these chromosomes were possibly implicated in PC development or progression. Study of recurring patterns of specific chromosomal aberrations might provide new information about the genetic events involved in these processes.The BPH specimens showed no deviation fromFrom the