Lack of deletions of the PTEN/MMAC1 and MXI1 loci in renal cell carcinoma by interphase cytogenetics

Non-canonical GLI1/2 activation by PI3K/AKT signaling in renal cell carcinoma: A novel potential therapeutic target

Renal cell carcinoma (RCC) is the most lethal urologic malignancy; however, the molecular events supporting RCC carcinogenesis and progression remain poorly understood. In this study, based on the analysis of gene expression profile data from human clear cell RCC (ccRCC) and the corresponding normal tissues, we discovered that Hedgehog (HH) pathway component genes GLI1 and GLI2 were significantly elevated in ccRCC. Survival analysis of a large cohort of ccRCC samples demonstrated that the expression of GLI1 and GLI2 was negatively correlated with patient overall survival. Clinical sample-based VHL mutation and cell model-based VHL manipulation studies all indicated that the activation of GLI1 and GLI2 was not affected by VHL status. Further signaling pathway dissections demonstrated that GLI1 and GLI2 were activated by the phosphoinositide 3-kinase (PI3K)/AKT pathway, but not mediated by the canonical HH/SMO/GLI signaling. Up-regulation of GLI1 and GLI2 promoted RCC proliferation and clonogenic ability, whereas, a combination of GLIs inhibitor Gant61 and AKT inhibitor Perifosine synergistically suppressed RCC growth and induced apoptosis in vitro and in vivo. Therefore, this study identifies that GLI1 and GLI2 are critical for RCC carcinogenesis, and also provides an alternative therapeutic strategy for RCC.

Overexpression of FABP7 promotes cell growth and predicts poor prognosis of clear cell renal cell carcinoma

OBJECTIVES

Renal cell carcinoma (RCC) is one of the most lethal urologic malignancies; however, the molecular events supporting RCC carcinogenesis remain poorly understood. The aim of the present study was to determine the differential expression of genes between normal kidney and clear cell RCC (ccRCC) samples and investigate the biological function of the most frequently altered gene in RCC cells.

MATERIALS AND METHODS

The gene expression profiles of 60 ccRCC and matched normal kidney samples from The Cancer Genome Atlas were analyzed. The altered genes were subjected to functional annotation clustering and integrative pathway analysis. The expression of one of the most frequently altered gene, fatty acid-binding protein (FABP) 7, in ccRCC and matched normal kidney samples was verified by immunohistochemistry and the association between FABP7 level and patient survival was investigated. Furthermore, FABP7 DNA copy number alteration, methylation, and mutation status in ccRCC from The Cancer Genome Atlas were analyzed. Finally, FABP7-overexpressing RCC cells were generated to determine the function of FABP7 in cell growth and the potential mechanisms of action.

RESULTS

FABP7 was significantly up-regulated in ccRCC, and the expression of FABP7 positively correlated with advanced clinical stage and poor survival of patients with ccRCC. FABP7 DNA copy number alteration was not frequently detected in ccRCC, and no mutation of FABP7 was found. FABP7 messenger RNA expression inversely correlated with its DNA methylation. Overexpression of FABP7 in RCC cells enhanced cell growth, clonogenicity, cell cycle progression and activated both extracellular-signal-regulated kinases (ERK) and signal transducer and activator of transcription 3 (Stat3) signaling.

CONCLUSION

FABP7 is overexpressed in ccRCC and promotes cell growth by the activation of ERK and Stat3 signaling pathways. Evidence from the clinical observations and experimental data suggests that FABP7 is a novel prognostic marker and potential therapeutic target for ccRCC.

The phosphoinositide 3-kinase/Akt pathway: a new target in human renal cell carcinoma therapy

Metastatic renal cell carcinoma is resistant to current therapies. The phosphoinositide 3-kinase (PI3K)/Akt signaling cascade induces cell growth, cell transformation, and neovascularization. We evaluated whether targeting this pathway could be of therapeutic value against human renal cell carcinoma. The activation of the PI3K/Akt pathway and its role in renal cell carcinoma progression was evaluated in vitro in seven human cell lines by Western blot, cell counting, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide, terminal deoxyribonucleotide transferase-mediated nick-end labeling assays, and fluorescence-activated cell sorting analysis, using two PI3K inhibitors, LY294002 and wortmannin, as well as by transfection with various Akt constructs and through Akt knockdown by small interfering RNA (siRNA). In vivo nude mice bearing human renal cell carcinoma tumor xenografts were treated with LY294002 (75 mg/kg/wk, 4 weeks, i.p.). Tumor growth was measured and tumors were subjected to Western blot and immunohistochemical analysis. Akt was constitutively activated in all cell lines. Constitutive phosphorylation of glycogen synthase kinase-3 (GSK-3) was observed in all cell lines, whereas forkhead transcription factor and mammalian target of rapamycin, although expressed, were not constitutively phosphorylated. Exposure to LY294002 or wortmannin decreased Akt activation and GSK-3 phosphorylation and reduced cell growth by up to 70% through induction of cell apoptosis. These effects were confirmed by transfection experiments with Akt constructs or Akt siRNA. Importantly, LY294002 induced up to 50% tumor regression in mice through tumor cell apoptosis. Tumor neovascularization was significantly increased by LY294002 treatment. Blood chemistries showed no adverse effects of the treatment. Our results suggest an important role of PI3K/Akt inhibitors as a potentially useful treatment for patients with renal cell carcinoma.

Allelic loss at 10q23.3 but lack of mutation of PTEN/MMAC1 in chromophobe renal cell carcinoma

Chromophobe renal cell carcinoma (RCC) is characterized by loss of multiple chromosomes including chromosome 10. This study was undertaken to determine the LOH at the PTEN/MMAC1 locus (chromosome band 10q23.3) and to search for gene mutations in 15 chromophobe, 50 conventional, and 10 papillary RCCs as well as in 10 renal oncocytomas. Loss of heterozygosity (LOH) wa seen at all informative loci in all chromophobe RCCs and in two conventional RCCs. We did not find mutations by analyzing exon 1 to 9 of the PTEN/MMAC1 gene using the PCR-SSCP technique in tumors with LOH at 10q23.3.