Non-tumor Kidney Tissues Research Articles

Mitochondrial DNA Variants at Low-Level Heteroplasmy and Decreased Copy Numbers in Chronic Kidney Disease (CKD) Tissues with Kidney Cancer.

The human mitochondrial genome (mtDNA) is a circular DNA molecule with a length of 16.6 kb, which contains a total of 37 genes. Somatic mtDNA mutations accumulate with age and environmental exposure, and some types of mtDNA variants may play a role in carcinogenesis. Recent studies observed mtDNA variants not only in kidney tumors but also in adjacent kidney tissues, and mtDNA dysfunction results in kidney injury, including chronic kidney disease (CKD). To investigate whether a relationship exists between heteroplasmic mtDNA variants and kidney function, we performed ultra-deep sequencing (30,000×) based on long-range PCR of DNA from 77 non-tumor kidney tissues of kidney cancer patients with CKD (stages G1 to G5). In total, this analysis detected 697 single-nucleotide variants (SNVs) and 504 indels as heteroplasmic (0.5% ≤ variant allele frequency (VAF) < 95%), and the total number of detected SNVs/indels did not differ between CKD stages. However, the number of deleterious low-level heteroplasmic variants (pathogenic missense, nonsense, frameshift and tRNA) significantly increased with CKD progression (p < 0.01). In addition, mtDNA copy numbers (mtDNA-CNs) decreased with CKD progression (p < 0.001). This study demonstrates that mtDNA damage, which affects mitochondrial genes, may be involved in reductions in mitochondrial mass and associated with CKD progression and kidney dysfunction.

Novel Diagnostic Value of Driver Gene Transcription Signatures to Characterise Clear Cell Renal Cell Carcinoma, ccRCC.

Routine molecular tumour diagnostics are augmented by DNA-based qualitative and quantitative molecular techniques detecting mutations of DNA. However, in the past decade, it has been unravelled that the phenotype of cancer, as it’s an extremely complex disease, cannot be fully described and explained by single or multiple genetic variants affecting only the coding regions of the genes. Moreover, studying the manifestation of these somatic mutations and the altered transcription programming—driven by genomic rearrangements, dysregulation of DNA methylation and epigenetic landscape—standing behind the tumorigenesis and detecting these changes could provide a more detailed characterisation of the tumour phenotype. Consequently, novel comparative cancer diagnostic pipelines, including DNA- and RNA-based approaches, are needed for a global assessment of cancer patients. Here we report, that by monitoring the expression patterns of key tumour driver genes by qPCR, the normal and the tumorous samples can be separated into distinct categories. Furthermore, we also prove that by examining the transcription signatures of frequently affected genes at 3p25, 3p21 and 9p21.3 genomic regions, the ccRCC (clear cell renal cell carcinoma) and non-tumorous kidney tissues can be distinguished based on the mRNA level of the selected genes. Our results open new diagnostics possibilities where the mRNA signatures of tumour drivers can supplement the DNA-based approaches providing a more precise diagnostics opportunity leading to determine more precise therapeutic protocols.

Long Non-Coding PROX1-AS1 Expression Correlates with Renal Cell Carcinoma Metastasis and Aggressiveness.

Long non-coding RNAs (lncRNAs) can be specifically expressed in different tissues and cancers. By controlling the gene expression at the transcriptional and translational levels, lncRNAs have been reported to be involved in tumor growth and metastasis. Recent data demonstrated that multiple lncRNAs have a crucial role in renal cell carcinoma (RCC) progression—the most common malignant urogenital tumor. In the present study, we found a trend towards increased PROX1 antisense RNA 1 (PROX1-AS1) expression in RCC specimens compared to non-tumoral margins. Next, we found a positive correlation between PROX1-AS1 expression and the occurrence of distant and lymph node metastasis, higher tumor stage (pT1 vs. pT2 vs. pT3–T4) and high-grade (G1/G2 vs. G3/G4) clear RCC. Furthermore, global demethylation in RCC-derived cell lines (769-P and A498) and human embryonic kidney 293 (HEK293) cells induced a significant increase of PROX1-AS1 expression level, with the most remarkable change in HEK293 cells. In line with this evidence, bisulfite sequencing analysis confirmed the specific demethylation of bioinformatically selected CpG islands on the PROX1-AS1 promoter sequence in the HEK293 cell line but not in the tumor cells. Additionally, the human specimen analysis showed the hemimethylated state of CG dinucleotides in non-tumor kidney tissues, whereas the tumor samples presented the complete, partial, or no demethylation of CpG-islands. In conclusion, our study indicated that PROX1-AS1 could be associated with RCC progression, and further investigations may define its role as a new diagnostic marker and therapeutic target.

Construction of a Novel Multigene Panel Potently Predicting Poor Prognosis in Patients with Clear Cell Renal Cell Carcinoma.

Simple SummaryClear cell renal cell carcinoma (ccRCC) is the predominant cause of kidney cancer death attributed to its prevalence (70%) and its nature being the most aggressive form of kidney cancer. Most ccRCC deaths are resulted from metastasis. It is essential to know which ccRCCs are at risk of metastasis and the development to lethal disease; however, our capacity for such analysis remains poor. To improve this diagnostic capacity, we have examined a comprehensive ccRCC dataset containing 512 patients and have produced a 9-gene signature. This signature is novel; all its 9 components genes are unknown to be related to ccRCC. Importantly, all 9 individual genes possess significant ability in diagnosis of ccRCC metastasis and fatality; the combination of these genes or this signature predicts deadly ccRCCs at an impressive efficiency. This research will open new avenues in ccRCC research and will have a major impact in reducing ccRCC-associated deaths.We observed associations of IQGAP1 downregulation with poor overall survival (OS) in clear cell renal cell carcinoma (ccRCC). Differentially expressed genes (DEGs, n = 611) were derived from ccRCCs with (n = 111) and without IQGAP1 (n = 397) reduction using the TCGA PanCancer Atlas ccRCC dataset. These DEGs exhibit downregulations of immune response and upregulations of DNA damage repair pathways. Through randomization of the TCGA dataset into a training and testing subpopulation, a 9-gene panel (SigIQGAP1NW) was derived; it predicts poor OS in training, testing, and the full population at a hazard ratio (HR) 2.718, p < 2 × 10−16, p = 1.08 × 10−5, and p < 2 × 10−16, respectively. SigIQGAP1NW independently associates with poor OS (HR 1.80, p = 2.85 × 10−6) after adjusting for a set of clinical features, and it discriminates ccRCC mortality at time-dependent AUC values of 70% at 13.8 months, 69%/31M, 69%/49M, and 75.3%/71M. All nine component genes of SigIQGAP1NW are novel to ccRCC. The inclusion of RECQL4 (a DNA helicase) in SigIQGAP1NW agrees with IQGAP1 DEGs enhancing DNA repair. THSD7A affects kidney function; its presence in SigIQGAP1NW is consistent with our observed THSD7A downregulation in ccRCC (n = 523) compared to non-tumor kidney tissues (n = 100). Collectively, we report a novel multigene panel that robustly predicts poor OS in ccRCC.

214P - Targeting epithelial-mesenchymal transition (EMT), novel strategy to delay resistance or re-sensitize renal cancer to Sunitinib

BackgroundEpithelial-Mesenchymal Transition (EMT) is a dynamic process hypothesized to occur in carcinoma during invasion and metastasis. Tyrosine Kinase Inhibitor Sunitinib stands as the main first-line treatment in metastatic renal clear cell carcinoma (mRCC). Activation of IGF and TGFβpathways are known to be associated with the acquisition of EMT and chemoresistance in cancer cells. Downregulation of EMT regulators is a promising therapeutic strategy to overcome resistance or resensitize RCC to Sunitinib therapy. Furthermore, indirect and specific inhibition of IGF axis by inhibition of PAPP-A, which regulates IGF signaling, represents a novel approach in mRCC treatment. MethodsRCC tumor tissues, primary and metastatic RCC cell lines (parental and Sunitinib resistant) were examined for EMT proteins (Ecad & Ncad), EMT regulators, TGFβ and IGF/PAPP-A axis by qRT-PCR and western blot. Analysis of TCGA transcriptome profiling dataset was performed. ResultsHigher expression of N cadherin and low expression of E cadherin indicating mesenchymal signature was noted in RCC patient tumors associated with significantly upregulated expression of known EMT inducers; TGFβ and IGF1R as compared to non-tumor adjacent kidney tissues. Expression of IGF1 axis components, EMT markers and TGFβ was confirmed via qRT-PCR in primary and metastatic RCC cell lines. Sunitinib-induced EMT was confirmed by upregulation of N cad and downregulation of Ecad in 786-O RCC cell line. Analysis of TCGA dataset revealed that IGF1R expression (n = 792, HR 1.45, p = 0.01) and TGFβ expression (n = 792, HR 2.14, p < 0.01) resulted in worse overall survival in mRCC patients, a non-significant trend towards worse survival was noted with PAPP-A expression (n = 792, HR 1.27, p = 0.1). ConclusionsOur data suggest that EMT may play a role in RCC progression and may be a mechanism of drug resistance to Sunitinib. TGFβ and IGF pathways are dysregulated in RCC, therefore direct or indirect targeting of these pathways may prove to be a novel strategy to delay resistance to Sunitinib or resensitize RCC to VEGF inhibitor therapy. Legal entity responsible for the studyFiona Elsey Cancer Research Institute. FundingFiona Elsey Cancer Research Institute. DisclosureAll authors have declared no conflicts of interest.

Simultaneous Extraction of RNA and Metabolites from Single Kidney Tissue Specimens for Combined Transcriptomic and Metabolomic Profiling.

Tissue analysis represents a powerful tool for the investigation of disease pathophysiology. However, the heterogeneous nature of tissue samples, in particular of neoplastic, may affect the outcome of such analysis and hence obscure interpretation of results. Thus, comprehensive isolation and extraction of transcripts and metabolites from an identical tissue specimen would minimize variations and enable the economic use of biopsy material which is usually available in limited amounts. Here we demonstrate a fast and simple protocol for combined transcriptomics and metabolomics analysis in homogenates prepared from one single tissue sample. Metabolites were recovered by protein precipitation from lysates originally prepared for RNA isolation and were analyzed by LC-QTOF-MS after HILIC and RPLC separation, respectively. Strikingly, although ion suppression was observed, over 80% of the 2885 detected metabolic features could be extracted and analyzed with high reproducibility (CV ≤ 20%). Moreover fold changes of different tumor and nontumor kidney tissues were correlated to an established metabolomics protocol and revealed a strong correlation ( rp ≥ 0.75). In order to demonstrate the feasibility of the combined analysis of RNA and metabolites, the protocol was applied to kidney tissue of metformin treated mice to investigate drug induced alterations.

Synergy Effect of Combining Fluorescence and Mid Infrared Fiber Spectroscopy for Kidney Tumor Diagnostics.

Matching pairs of tumor and non-tumor kidney tissue samples of four patients were investigated ex vivo using a combination of two methods, attenuated total reflection mid infrared spectroscopy and fluorescence spectroscopy, through respectively prepared and adjusted fiber probes. In order to increase the data information content, the measurements on tissue samples in both methods were performed in the same 31 preselected positions. Multivariate data analysis revealed a synergic effect of combining the two methods for the diagnostics of kidney tumor compared to individual techniques.

The role of Notch signaling pathway and Wnt signaling pathway in the pathogenesis of Wilm’s tumor

Objective To investigate the expression of Notch signal pathway and Wnt signaling pathway in the pathogenesis of Wilm’s tumor. Methods The samples of Wilm’s tumor and corresponding non-tumor kidney tissues were collected. The mRNA and protein expression levels of Notch1 and vascular endothelial growth factor (VEGF) were detected by real-time fluorescent quantitative polymerase chain reaction (FQ-PCR) and immunohistochemistry respectively. Human nephroblastoma cell lines (SK-NEP-1) were treated with Notch inhibitor γ-secretase Inhibitor (DAPT), and the signal pathways of Wnt and Notch were detected by Western blotting. Results Immunohistochemistry staining revealed that Notch1 protein expression in WT group with stages of 2, 3 and 4 was 0.519 3±0.008 6, 0.616 8±0.002 2, and 0.892 6±0.006 0respectively, which was significantly higher than in the control group (0.205 3±0.009 3, P<0.05). The mRNA expression of Notch1 and VEGF was higher in the observation group than that in the control group. After treatment of SK-NEP-1 cells with different concentrations of DAPT, the Notch1 and Jagged1 protein expression was significantly decreased as compared with ths in the control group, and the Wnt1 and β-catenin protein expression levels were also reduced apparently, and VEGF expression also significantly decreased. Conclusion Notch and Wnt signaling pathways participate in promoting the occurrence of Wilm’s tumor, and up-regulated Notch and Wnt protein levels may be associated with malignant degree of Wilm’s tumor. Key words: Notch signal pathway; Wnt signal pathway; Wilm’s tumor

Abstract 2463: PEGPH20 increases the anticancer activity of standard chemotherapy combinations, vincristine (VIN) and D actinomycin (DACT), in a Wilms’ xenograft model

Abstract Hyaluronan (HA), which accumulates in the tumor microenvironment of many solid tumors, is associated with tumor progression and negative clinical outcomes. Preclinical studies have demonstrated that PEGPH20-mediated HA removal from HA-rich xenograft tumors in mice decreases tumor interstitial fluid pressure and water content, resulting in decompression of tumor vasculature, increased tumor perfusion and enhanced chemotherapeutic activity. Accordingly, the HA degrading enzyme, pegylated recombinant human hyaluronidase PH20 (PEGPH20), is currently being evaluated in clinical trials with selected treatment regimens in several malignancies, including metastatic pancreatic adenocarcinoma, gastric cancer, breast cancer and non-small cell lung cancer. Advances in treatment for pediatric Wilms’ tumor patients have significantly increased survival, but salvage chemotherapy for relapsed pediatric patients remains challenging. To evaluate the role of HA in this disease, 19 Wilms’ tumor histological specimens were surveyed for HA status using a novel probe (Jadin 2014). 79% (15/19) of the samples stained strongly for HA when compared to non-tumor kidney tissue, prompting additional preclinical studies. In brief, a human Wilms’ tumor cell line, WT-CLS1, was transduced with hyaluronan synthase-3 (HAS3). The subsequent WT-CLS1/HAS3 cells produced more HA and WT-CLS1/HAS3 xenograft tumors grew significantly faster than parental WT-CLS1 tumors. To evaluate the efficacy of PEGPH20 in combination with Wilms’ tumor chemotherapy (CTX) combinations, WT-CLS1/HAS3 cells were inoculated adjacent to the tibial periosteum of nude mice and tumor growth was monitored via ultrasonography. When tumors reached ∼250 mm3, mice were staged into treatment groups: vehicle control, PEGPH20, vincristine (VIN) plus Dactinomycin (DACT), and PEGPH20+VIN+DACT at different dose/frequency combinations. Average tumor growth inhibition (TGI) and overall survival for PEGPH20+VIN+DACT-treated mice were superior to TGI and survival of VIN+DACT treatment alone. In separate studies WT-CLS1/HAS3 tumor-bearing mice were staged into three groups: vehicle control, low dose PEGPH20 (0.0375 mg/kg, iv) and high dose PEGPH20 (1 mg/kg, iv). Animals were administered the hypoxyprobe pimonidazole (60 mg/kg, ip) three hours prior to sacrifice, and whole tumors were removed and processed via immunofluorescence. High dose PEGPH20 reduced this measure of tumor hypoxia by 5% (p = 0.023). Taken together, these data demonstrate that HA accumulation in Wilms’ tumor is common, and treatment with PEGPH20 hyaluronidase can increase CTX efficacy and reduce tumor hypoxia in a preclinical model of this disease. These results support further studies with PEGPH20 in combination with chemotherapy in preclinical models of Wilms’ tumor and suggest investigation in this pediatric patient population may be warranted. Citation Format: Jessica Cowell, Susan J. Zimmerman, Mathieu Marrela, Ping Jiang, Peter J. Houghton, Michael J. LaBarre, Daniel C. Maneval, Curtis B. Thompson, Xiaoming Li. PEGPH20 increases the anticancer activity of standard chemotherapy combinations, vincristine (VIN) and D actinomycin (DACT), in a Wilms’ xenograft model. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 2463.

GSK-3 directly regulates phospho-4EBP1 in renal cell carcinoma cell-line: an intrinsic subcellular mechanism for resistance to mTORC1 inhibition.

BackgroundThe phosphoinositide 3-kinase (PI3K)/Akt/mammalian target of rapamycin 1 (mTORC1) signaling pathway is aberrantly activated in renal cell carcinoma (RCC). We previously demonstrated glycogen synthase kinase-3β (GSK-3β) positively regulated RCC proliferation. The aim of this study was to evaluate the role of GSK-3 in the PI3K/Akt/mTORC1 pathway and regulation of the downstream substrates, eukaryotic translation initiation factor 4E-binding protein 1 (4EBP1), ribosomal protein S6 kinase (S6K), and ribosomal protein S6 (S6RP).MethodsWe used human RCC cell lines (ACHN, Caki1, and A498) and, as normal controls, human renal proximal tubular epithelial cell (HRPTEpC) and non-tumorous kidney tissues that were obtained surgically for treatment of RCC patients. Rapamycin-resistant ACHN (ACHN/RR) cells were generated with chronic exposure of ACHN to rapamycin ranging from 1nM finally to 1 μM. Cell viability, cell cycling and direct interaction between GSK-3β and 4EBP1 were evaluated with MTS assay, flowcytometry and in vitro kinase assay with recombinant GSK-3β and 4EBP1products, respectively. Protein expression and phosphorylation of molecules associated with the PI3K/Akt/mTORC1 pathway were examined by immunoblotting. Effects of drug combination were determined as the combination index with CompuSyn software.ResultsOverexpression and phosphorylation of 4EBP1 and S6RP together with GSK-3 activation were observed in RCC cell lines, but not in human normal kidney cells and tissues. Cell proliferation, p4EBP1 and pS6RP were strongly suppressed by GSK-3 inhibition. Rapamycin and LY294002 sufficiently decreased pS6RP, but only moderately p4EBP1. In vitro kinase assays showed that recombinant GSK-3β phosphorylated recombinant 4EBP1, and the effect was blocked by GSK-3 inhibitors. Different from rapamycin, AR- A014418 remarkably inhibited cell proliferation, and rapidly suppressed p4EBP1 and pS6RP in ACHN and ACHN/RR (in 30 min to 1 h). AR- A014418 and rapamycin combination showed additivity at lower concentrations, but antagonism at higher concentrations.ConclusionsGSK-3β could directly phosphorylate 4EBP1 and activate the mTORC1 downstream signaling cascades to enhance protein biosynthesis and cell proliferation in RCC cell lines independent of rapamycin sensitivity. The direct GSK-3β/4EBP1 pathway might be an important subcellular mechanism as an inherent equipment for RCC cells to acquire clinical chemoresistance to mTORC1 inhibitors.Electronic supplementary materialThe online version of this article (doi:10.1186/s12885-016-2418-7) contains supplementary material, which is available to authorized users.

GFOD1 and peejar are promising markers for clear-cell renal cell carcinoma disease progression.

Clear cell renal cell carcinoma (ccRCC) is a common genitourinary malignancy. The molecular pathogenesis of ccRCC remains unclear and biomarkers for daily practice were still limited. We performed an integrative analysis of two public ccRCC microarray datasets, E-GEOD-22541 and E-MTAB-1050, The candidate differential expression genes (DEG) were then confirmed in the E-GEOD-53757 dataset. In addition, an independent cohort of 50 ccRCC and 36 non-tumor kidney tissues were analyzed to examine the selected DGEs by qRT-PCR. We identified and validated two DEGs, namely GFOD1 and peejar, which were significantly up-regulated in ccRCC compared with normal renal tissues (p < 0.001). Moreover, the expression of these two genes are related to histological grade and stage and decrease of their expression correlated with disease progression (p < 0.05). Furthermore, we found the expression of peejar was positively correlated with the expression of GFOD1 in ccRCC tissue, with Pearson correlation coefficiency reaching 0.939 (p < 0.001). GFOD1 and peejar were novel genes correlated with ccRCC disease progression and patients' poor prognosis.

Interstitial fibrosis in the renal inner medulla in humans is associated with up‐regulation of miR‐382 and down‐regulation of kallikrein 5

MicroRNAs are important post transcriptional regulators of gene expression. Our lab has identified microRNA miR-382 as a facilitating regulator of interstitial fibrosis in the renal medulla of mice and in cultured human kidney cells and determined that this regulation may be mediated by a suppression of kallikrein 5 (KLK5). KLK5 is a (chymo)trypsin like peptidase capable of degrading extracellular matrix proteins. The goal of this study was to determine if there is an association between the levels of interstitial fibrosis, miR-382 and KLK5 in human kidneys. Non-tumor kidney tissue samples were obtained from patients who underwent partial or complete nephrectomy to remove renal tumors (n=6). The renal cortex, outer medulla and inner medulla were evaluated for fibrosis, miR-382 expression and KLK5 expression using trichrome staining, in situ hybridization and immunohistochemistry, respectively. In the inner medulla miR-382 expression correlated positively with fibrosis (R2=0.75) and negatively with KLK5 expression (R2=0.52). A positive correlation between miR-382 and interstitial fibrosis was also detected in the outer medulla. These data indicate that alterations in miR-382 are consistent with contribution to interstitial fibrosis via KLK5 in the inner medulla of human kidney.

Prognostic significance of survivin expression in renal cell cancer and its correlation with radioresistance

Survivin, an important inhibitor of apoptosis, has been found to play an important role in the initiation, progression, and chemoradioresistance of human malignancies. Previously, we have reported that upregulation of survivin in oral squamous cell carcinoma correlates with poor prognosis and chemoresistance. The aim of this study was to assess prognostic significance of survivin protein expression in RCC and analyze its correlation with radiosensitivity of RCC cells. RT-PCR and Western blot assays were performed to detect survivin mRNA and protein expression in normal human kidney epithelial cell line (HKEC) or RCC cell lines. The expression of survivin mRNA in RCC and corresponding nontumor kidney tissues was also detected by RT-PCR. Immunohistochemistry was performed to determine survivin protein expression in 75 cases of RCC tissue samples. Moreover, the association of survivin protein expression with clinicopathogical factors and prognosis of RCC patients was statistically analyzed. Small interfering RNA was used to knockdown the endogenous survivin expression in RCC cell line (ACHN) and evaluate the effects of survivin knockdown on proliferation, apoptosis, and radiosensitivity of RCC cell line. RCC cells showed sufficient expression of survivin mRNA and protein, but the expression of survivin gene was not detected in normal HKEC. Moreover, the expression level of survivin mRNA in RCC tissues was significantly higher than that in corresponding nontumor kidney tissues. The immunostaining of survivin protein was mainly located in cytoplasm of RCC tumor cells. Tumor pathological stage (P = 0.028), grade (P = 0.004), and lymph node metastasis (P = 0.017) of RCC patients were significantly correlated with survivin protein expression. In addition, patients with high survivin levels had a significantly shorter overall survival than those with low levels (P < 0.001), and the expression of survivin protein was an independent prognostic factor for RCC patients (P = 0.008). The expression of survivin gene could be reduced in RCC cell line and survivin knockdown could inhibit growth and enhance in vivo radiosensitivity of RCC cell line by inducing apoptosis enhancement. Taken together, the status of survivin protein expression may be an independent factor for predicting the prognosis of RCC patients and tumor-specific survivin knockdown combined with radiotherapy will be a potential strategy for RCC therapy.

PP77 CPT1C, a promising anticancer target in the treatment of hypoxic brain tumours

Recruiting Akt to the membrane-bound phosphatidylinositol (3,4,5) trisphosphate (PIP3) is required for Akt activation. While PI3 kinase (PI3K) produces PIP3, PTEN dephosphorylates the 3-position phosphate from PIP3, thereby directly inhibiting Akt activation. PTEN is the dominant PIP3 phosphatase, as knockdown of PTEN results in increases in Akt activation in mice. The PTEN tumor suppressor gene is frequently mutated in a variety of human cancers, consistent with an inverse correlation between levels of the PTEN protein and Akt activation. We have examined PTEN expression and Akt activation in 35 primary clear cell renal cell carcinomas RCCs (ccRCCs) and 9 papillary RCCs (pRCCs) and their respective non-tumor kidney tissues. The PTEN protein was reduced in 16 ccRCCs (16/35 = 45.7%) and 8 pRCCs (8/9 = 88.9%). In these RCCs, 25.0% (4/16) of ccRCCs and 25.0% (2/8) of pRCCs expressed elevated Akt activation. 19 ccRCCc (19/35 = 54.3%) expressed comparable or higher levels of PTEN. Of these ccRCCs, 31.6% (6/19) showed increases in Akt activation. As PTEN dominantly inhibits Akt activation, the coexistence of high levels of the PTEN protein with enhanced Akt activation suggests the existence of novel mechanisms which attenuate PTEN function in ccRCC. These mechanisms may reduce PTEN function or increase PIP3 production.

Commentary on Specific reduction of Fas-associated protein with death domain (FADD) in clear cell renal cell carcinoma: Xu H, He L, Feng X, Kapoor A, Tang D, Department of Nephrology, Xiangya Hospital, Central South University, Changsha, Hunan, P.R. China

Fas-associated protein with death domain (FADD) plays a major role in the execution of apoptosis. Attenuation of apoptosis is a hallmark of cancer. Through systemic examination of FADD in renal cell carcinoma (RCC) and adjacent nontumor kidney tissues from 85 patients, we demonstrated a significant reduction of FADD in clear cell RCC (ccRCC) compared with the respective nontumor kidney tissues. In human kidney, FADD is expressed in both the proximal and distal tubules. As ccRCC originates from the proximal tubular epithelium, reduction of FADD in ccRCC indicates that FADD-mediated apoptosis may inhibit ccRCC tumorigenesis.

Specific Reduction of Fas-Associated Protein with Death Domain (FADD) in Clear Cell Renal Cell Carcinoma

Fas-associated protein with death domain (FADD) plays a major role in the execution of apoptosis. Attenuation of apoptosis is a hallmark of cancer. Through systemic examination of FADD in renal cell carcinoma (RCC) and adjacent nontumor kidney tissues from 85 patients, we demonstrated a significant reduction of FADD in clear cell RCC (ccRCC) compared to the respective nontumor kidney tissues. In human kidney, FADD is expressed in both the proximal and distal tubules. As ccRCC originates from the proximal tubular epithelium, reduction of FADD in ccRCC indicates that FADD-mediated apoptosis may inhibit ccRCC tumorigenesis.

Allelic loss and mutations in a new ETRG-1 gene are early events in diethylstilbestrol-induced renal carcinogenesis in Syrian hamsters

Diethylstilbestrol (DES) is a synthetic estrogen and well known human carcinogen, but the mechanism by which DES causes cancer is not clear. In this study, using AP-PCR method we have identified a genetic alteration that was common in DES-induced kidney tumors as well as in its surrounding non-tumor tissue. Further characterization of this genetically altered region revealed that it represents an uncharacterized novel gene. We have named this gene as Estrogen Target Rodent Gene-1 ( ETRG-1). Southern blot analysis revealed about 50% reduction in the ETRG-1 gene-specific hybridization signal, indicating genomic loss of one allele of ETRG-1 in DES-induced tumors as compared to its age-matched control. Sequence analysis of the remaining allele of ETRG-1 from tumor revealed point mutations and an insertion of 37 bp as compared to its normal allele from the age-matched control kidney tissue. The expression of ETRG-1 at transcript level was found to be extremely reduced or undetectable in DES-induced kidney tumors as compared to its age-matched control kidney tissue. Thus, the findings of this study suggest that (a) DES-induced allelic loss and mutations may be involved in DES-induced kidney carcinogenesis, (b) Constitutive expression of ETRG-1 in normal kidney tissue and decreased or undetectable expression in tumors, presumably as a result of allelic loss and mutational inactivation, suggest that it may be a tumor suppressor gene, and finally, (c) The identification of the allelic loss and mutations that were common in DES-exposed non-tumor kidney tissue, and in frank kidney tumors indicate that these genetic aberrations are early events in DES-induced kidney carcinogenesis and it may serve as biomarker for early detection of DES-induced cancer.

Co-existence of high levels of the PTEN protein with enhanced Akt activation in renal cell carcinoma

Recruiting Akt to the membrane-bound phosphatidylinositol (3,4,5) trisphosphate (PIP3) is required for Akt activation. While PI3 kinase (PI3K) produces PIP3, PTEN dephosphorylates the 3-position phosphate from PIP3, thereby directly inhibiting Akt activation. PTEN is the dominant PIP3 phosphatase, as knockdown of PTEN results in increases in Akt activation in mice. The PTEN tumor suppressor gene is frequently mutated in a variety of human cancers, consistent with an inverse correlation between levels of the PTEN protein and Akt activation. We have examined PTEN expression and Akt activation in 35 primary clear cell renal cell carcinomas RCCs (ccRCCs) and 9 papillary RCCs (pRCCs) and their respective non-tumor kidney tissues. The PTEN protein was reduced in 16 ccRCCs (16/35 = 45.7%) and 8 pRCCs (8/9 = 88.9%). In these RCCs, 25.0% (4/16) of ccRCCs and 25.0% (2/8) of pRCCs expressed elevated Akt activation. 19 ccRCCc (19/35 = 54.3%) expressed comparable or higher levels of PTEN. Of these ccRCCs, 31.6% (6/19) showed increases in Akt activation. As PTEN dominantly inhibits Akt activation, the coexistence of high levels of the PTEN protein with enhanced Akt activation suggests the existence of novel mechanisms which attenuate PTEN function in ccRCC. These mechanisms may reduce PTEN function or increase PIP3 production.

Concomitant deregulation of HIF1α and cell cycle proteins in VHL-mutated renal cell carcinomas

Renal cell carcinomas (RCCs) of the clear cell type are associated with alteration of the von Hippel-Lindau (VHL) tumour suppressor gene as well as subsequent stabilization and over-expression of hypoxia inducible factor (HIF), which causes up-regulation of cyclin D1. On the basis of their ability to interact with cyclin D1 we investigated a number of cell cycle proteins to shed further light on the downstream effects of HIF dysregulation. Expression of HIF1alpha, cyclin D1, cyclin-dependent kinase 4 and cyclin-dependent kinase inhibitors p16, p21 and p27 was studied by immunohistochemistry. Since NFkappaB1/RelA have been shown to bind to the cyclin D1 promoter, mRNA expression of these transcription factors was further analysed by quantitative PCR. In RCCs harbouring VHL mutations/hypermethylation, over-expression of HIF1alpha was parallelled by up-regulation of cyclin D1 and CDK4 and down-regulation of p21 and p27. Moreover, p27 expression was inversely correlated with tumour cell differentiation. Comparison of non-tumorous autologous kidney tissues revealed a significant down-regulation of NFkappaB1 mRNA expression in patients harbouring RCC with VHL mutations/hypermethylation. Our data support the notion of a link between VHL deficiency/HIF dysfunction and disturbances of cell cycle control in the tumorigenesis of VHL-negative RCC.

Glutathione S-transferase isoenzyme profile in non-tumor and tumor human kidney tissue.

Glutathione S-transferase (GST) isoenzyme profiles of non-tumor and tumor renal tissue of patients suffering from renal cell carcinoma (RCC) of the clear cell type were determined and compared to those of normal renal tissue. GST isoenzyme(s) were first separated on the basis of their affinity to glutathione sepharose 4B affinity column. Affinity-bound GSTs were further purified by anionic and cationic chromatofocusing. The results presented in this study show that non-tumor tissue distant from renal tumors and renal tumors have lower specific GST activity and a different isoenzyme profile than normal human kidney. Purification of normal kidney GSTs by affinity chromatography revealed the presence of two GST fractions: flow-through GST without affinity for glutathione affinity resin and GST fraction tightly bound to affinity matrix. In non-tumor kidney tissue of RCC patients, substantially less flow-through GST fraction was found, whereas renal tumors did not express flow-through GST at all. Isoelectric chromatofocusing indicated smaller numbers of GST isoenzymes in non-tumor and tumor kidney regions, with anionic forms dominating. It could be speculated that decreased expression of cationic GST isoenzymes (corresponding to class alpha) in non-tumor kidney tissue of RCC patients might be responsible for differences in sensitivity to specific carcinogens. The observations that RCCs are devoid of affinity flow-through GST and have small number of isoenzymes are further proof of low-level GST expression in RCC.