ccRCC Carcinogenesis Research Articles

Association of ATG7 Polymorphisms and Clear Cell Renal Cell Carcinoma Risk.

Kidney cancer is one of the most common cancers worldwide. Recent studies have suggested that single nucleotide polymorphisms (SNPs) in autophagy-related gene are associated with the risk of kidney cancer. This study was undertaken to investigate the association of autophagyrelated gene 7 (ATG7) polymorphisms with the risk of clear cell renal cell carcinoma (ccRCC) in the Chinese Han population. Blood samples were collected from 293 ccRCC patients and 297 healthy controls. Three ATG7 polymorphisms (rs1375206, rs2606736 and rs6442260) were genotyped by Agena MassARRAY. The association was estimated by genetic models and stratification analyses. A significant association was observed between allele A of rs6442260 and ccRCC risk (OR = 0.76, 95% CI: 0.58-0.99, p = 0.039). Genetic model analysis revealed that rs2606736 (OR = 0.57, 95% CI: 0.34-0.95, p = 0.031) and rs6442260 (OR = 0.44, 95% CI: 0.22-0.90, p = 0.021) were associated with decreased risk of ccRCC under recessive model. Age stratification analysis showed that rs2606736 (OR = 0.67, 95% CI: 0.46-0.98, p = 0.036) and rs6442260 (OR = 0.26, 95% CI: 0.07-0.89, p = 0.014) were significantly decreased risk of ccRCC under the log-additive model in age > 55 years old and ≤ 55 years old, respectively. This study indicated that ATG7 polymorphisms (rs2606736 and rs6442260) have a protective role for ccRCC risk. Further large sample size and functional assays are needed to confirm our findings and reveal the role of ATG7 polymorphisms in ccRCC carcinogenesis.

CLEC3B is downregulated and inhibits proliferation in clear cell renal cell carcinoma.

Dysregulation of C-Type Lectin Domain Family 3 Member B (CLEC3B) in serum or tumor tissues has been reported in patients with various cancer types. However, the expression and function of CLEC3B in clear cell renal cell carcinoma (ccRCC) remain unknown. To examine the function of CLEC3B in ccRCC, The Cancer Genome Atlas (TCGA) and Gene Expression Omnibus (GEO) databases were examined to determine the expression of CLEC3B at the transcriptional level and it was demonstrated that CLEC3B mRNA was significantly downregulated in ccRCC compared with normal tissues (P<0.0001 and P=0.0392 in TCGA and GEO databases, respectively). The downregulation of CLEC3B was further validated at the protein level in 78.9% of ccRCCs by immunohistochemistry. To investigate the potential genetic mechanism for CLEC3B downregulation in ccRCC, copy number analysis was performed by profiling the copy number variation data from the TCGA project and it was revealed that the copy number loss of CLEC3B was prevalent in up to 88.1% of patients with ccRCC. CLEC3B genetic deletion was coupled with the well-known genetic loss of the von Hippel-Lindau tumor suppressor, which is a characteristic oncogenic event during ccRCC carcinogenesis. The downregulation of CLEC3B was associated with tumor progression and predicted unfavorable prognostic outcomes in the TCGA cohort. Real-time cell analyzer system technology revealed that CLEC3B inhibited the proliferation of ccRCC cell lines in vitro and that the mitogen-activated protein kinase pathway may contribute to this process. CLEC3B demonstrated substantial positive associations with proliferation inhibitors, but inverse associations with proliferation inducers and markers in two large ccRCC cohorts, suggesting that CLEC3B was able to identify ccRCCs with a lower proliferation capacity. In conclusion, the results of the present study propose that CLEC3B is a promising target for therapeutic intervention in ccRCC.

Identification of potential crucial genes associated with carcinogenesis of clear cell renal cell carcinoma.

Clear cell renal cell carcinoma (ccRCC) is a common genitourinary malignancy with high mortality. However, the molecular pathogenesis of ccRCC remains unclear and effective biomarkers for daily practice are still limited. Thus, we aimed to identify the potential crucial genes and pathways associated with carcinogenesis of ccRCC and further analyze the molecular mechanisms implicated in tumorigenesis. In the present study, expression profiles GSE 66270, GSE 53757, GSE 36895, and GSE 76351 were downloaded from GEO database, including 244 matched primary and adjacent normal tissues, furthermore, the level 3 RNAseq dataset (RNAseqV2 RSEM) of KIRC was also downloaded from The Cancer Genome Atlas (TCGA), which consist of 529 ccRCC tumors and 72 normal tissues. Then, differentially expressed genes (DEGs) and pathway enrichment were analyzed by using R software. A total of 129 up- and 123 down-regulated genes were identified, which were aberrantly expressed both in GEO and TCGA data. Second, Gene ontology (GO) analyses revealed that most of the DEGs were significantly enriched in integral component of membrane, extracellular exosome, plasma membrane, cell adhesion, and receptor binding. Signaling pathway analyses indicated that DEGs had common pathways in signal transduction, metabolism, and immune system. Third, hub genes were identified with protein-protein interaction (PPI) network, including PTPRC, TGFB1, EGF, MYC, ITGB2, CTSS, FN1, CCL5, KNG1, and CD86. Additionally, sub-networks analyse was also performed by using MCODE plugin. In conclusion, the novel DEGs and pathways in ccRCC identified in this study may provide new insight into the underlying molecular mechanisms that facilitates RCC carcinogenesis.

Versican Promotes Tumor Progression, Metastasis and Predicts Poor Prognosis in Renal Carcinoma.

The proteoglycan versican (VCAN) promotes tumor progression and enhances metastasis in several cancers; however, its role in clear cell renal cell carcinoma (ccRCC) remains unknown. Recent evidence suggests that VCAN is an important target of chromosomal 5q gain, one of the most prevalent genetic abnormalities in ccRCC. Thus, we investigated whether VCAN expression is associated with the pathogenesis of ccRCC. VCAN expression was analyzed using three RCC and normal kidney cell lines as well as a clinical cohort of 84 matched ccRCC and normal renal tissues. Functional analyses on growth and progression properties were performed using VCAN-depleted ccRCC cells. Microarray expression profiling was employed to investigate the target genes and biologic pathways involved in VCAN-mediated ccRCC carcinogenesis. ccRCC had elevated VCAN expression in comparison with normal kidney in both cell lines and clinical specimens. The elevated expression of VCAN was significantly correlated with metastasis (P < 0.001) and worse 5-year overall survival after radical nephrectomy (P = 0.014). In vitro, VCAN knockdown significantly decreased cell proliferation and increased apoptosis in Caki-2 and 786-O cells, and this was associated with alteration of several TNF signaling-related genes such as TNFα, BID, and BAK Furthermore, VCAN depletion markedly decreased cell migration and invasion which correlated with reduction of MMP7 and CXCR4. These results demonstrate that VCAN promotes ccRCC tumorigenesis and metastasis and thus is an attractive target for novel diagnostic, prognostic, and therapeutic strategies.Implications: This study highlights the oncogenic role of VCAN in renal cell carcinogenesis and suggests that this gene has therapeutic and/or biomarker potential for renal cell cancer. Mol Cancer Res; 15(7); 884-95. ©2017 AACR.

Abstract 3362: PBRM1 regulates the transcription of cell adhesion genes in ccRCC

Abstract Advances in parallel sequencing have facilitated the recent identification of Polybromo-1 (PBRM1), a component of the PBAF (Polybromo-associated-BRG1- or BRM-associated factors) chromatin remodeling complex, as the second most frequently mutated gene in clear-cell renal cell Carcinoma (ccRCC). While several studies have described the diversity of PBRM1 mutations in ccRCC and established the mutation of PBRM1 as a “driver” of ccRCC carcinogenesis, little is known about the biological significance of PBRM1. With the intent of shedding light on the mechanistic roles of PBRM1, we have employed Next Generation Sequencing to delineate the transcriptional profile of cellular models of ccRCC with or without PBRM1 expression and identified genes associated with cell adhesion to be regulated by PBRM1 in 2D monolayer cultures. Since 2D cultures lack the architectural complexities to support studies pertaining to cellular adhesion, we evaluated the role of PBRM1 in 3D culture on Basement Membrane Matrix to provide a physiologically relevant analysis of gene expression and the resulting cellular phenotype. The results showed that of the 97 cell adhesion genes identified to be upregulated by PBRM1 in 2D cultures, 45 were also upregulated in 3D cultures and a subset of 32/45 genes underwent increased gene expression in 3D with respect to 2D cultures. The gene expression profile of candidate genes were verified by qPCR and Western Blotting. Mining The Cancer Genome Atlas (TCGA) publicly available data, we were able to correlate the gene expression profiles of cell adhesion genes identified in 3D cultures with those of ccRCC patients bearing at least 1 copy of the PBRM1 gene. Furthermore, we performed a PBRM1-ChIP-seq to map the genome-wide targets of PBRM1 and revealed the association of PBRM1 occupancy at proximal regulatory regions of 8/45 cell adhesion genes. All of these taken together, indicate a role for PBRM1 in regulating the gene expression of cell adhesion genes which act as important players in cellular morphogenesis and responsiveness to changes in the external environment. Disruption of cell adhesion is believed to affect signal transduction and pave the way facilitating metastasis in neoplastic cells. Currently we are investigating the effect of loss-of-PBRM1 on Epithelial to Mesenchymal Transition (EMT) and metastasis in ccRCC. Note: This abstract was not presented at the meeting. Citation Format: Basudev Chowdhury. PBRM1 regulates the transcription of cell adhesion genes in ccRCC [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 3362. doi:10.1158/1538-7445.AM2017-3362

VHL deficiency augments anthracycline sensitivity of clear cell renal cell carcinomas by down-regulating ALDH2

The von Hippel-Lindau (VHL) is deficient in ∼70% of clear-cell renal cell carcinomas (ccRCC), which contributes to the carcinogenesis and drug resistance of ccRCC. Here we show that VHL-deficient ccRCC cells present enhanced cytotoxicity of anthracyclines in a hypoxia-inducible factor-independent manner. By subtractive proteomic analysis coupling with RNAi or overexpression verification, aldehyde dehydrogenase 2 (ALDH2) is found to be transcriptionally regulated by VHL and contributes to enhanced anthracyclines cytotoxicity in ccRCC cells. Furthermore, VHL regulates ALDH2 expression by directly binding the promoter of −130 bp to −160 bp to activate the transcription of hepatocyte nuclear factor 4 alpha (HNF-4α). In addition, a positive correlation is found among the protein expressions of VHL, HNF-4α and ALDH2 in ccRCC samples. These findings will deepen our understanding of VHL function and shed light on precise treatment for ccRCC patients.

Genomic instability and DNA damage repair in clear cell renal cell carcinoma.

4581 Background: Kidney cancer accounts for 2-3% of all new cancers with clear cell renal cell carcinoma (ccRCC) the most common subtype. ccRCC is characterized by a high level of genomic instability, suggesting defective DNA damage repair (DDR). The most frequent genomic alteration in ccRCC involves loss of the 3p chromosomal arm which harbors the von Hippel Lindau gene ( VHL), in addition to nearby genes SETD2, BAP1, and PBRM. We hypothesized that VHL loss leads to defective DDR as an early event in ccRCC carcinogenesis, giving way to a mutator phenotype. We posited that assessment of very early ccRCC tumors would inform us regarding the core mutations required to drive tumorigenesis in ccRCC, and that we could confirm these findings in appropriate model systems. Methods: We performed whole-exome (WES) DNA sequencing on 11 early-stage ccRCC tumors from 5 individuals, along with their matched normal DNA. We then analyzed ccRCC samples with and without somatic VHL mutations from the Cancer Genome Atlas (TCGA) for mutational load. Finally we assessed DDR signaling activity in renal proximal tubular cell lines (RPTEC) with VHL/SETD2 knockdown and in murine embryo fibroblasts (MEFs) from Vhl and Setd2knockout mice treated with etoposide via γH2AX expression and direct repeat-green fluorescent protein reporter assay. Results: All 11 samples revealed loss of 3p with pathogenic germline or somatic mutation in remaining VHL allele. No mutations were found in genes frequently mutated in larger ccRCC, including PBRM1, BAP1 or SETD2. WES revealed ~100 mutations/tumor, with no shared mutations across samples, even within the same individual. TCGA analysis showed similar mutational loads across ccRCC samples. MEFs with biallelic loss of Vhl and monoallelic loss of Setd2 and RPTEC with VHL and SETD2knockdown displayed increased DNA damage with impaired homologous repair and increased non-homologous end joining (NHEJ). Conclusions: Early stage ccRCC tumors with loss of VHL and chr 3p demonstrate genomic instability and a mutator phenotype similar to more advanced ccRCC. Cell line models of early ccRCC show increased DNA damage with a greater reliance on error-prone NHEJ machinery. These defects could be targeted for synthetic lethal treatment strategies.

E2F3 upregulation promotes tumor malignancy through the transcriptional activation of HIF-2α in clear cell renal cell carcinoma.

The E2F3 transcriptional regulatory pathway plays a major part in multiple-cancer progression, but the specific contributions of this pathway to tumor formation and the progression of clear cell renal cell carcinoma (ccRCC) are not fully understood. Clinically, we demonstrated that E2F3 was overexpressed in advanced tumor features. Moreover, cytoplasmic restoration predicted the poor overall survival of ccRCC patients. As a remarkable oncogene for ccRCC, high HIF-2α levels closely correlated with E2F3 upregulation. We observed in vitro that E2F3 overexpression and knockdown regulated HIF-2α expression. Furthermore, we found that HIF-2α harbored multiple E2F3 binding sites in the promoters. Mechanistically, E2F3 acted to transactivate HIF-2α transcription, which in turn exerted a serial effect on the pivotal epithelial–mesenchymal transition-related genes. The RNA interference-mediated silencing of HIF-2α attenuated E2F3-enhanced cell migration and invasion in vitro and in vivo. Overall, our results identified HIF-2α as a direct target gene for E2F3 upregulation, which was critical for carcinogenesis and progression of ccRCC. Thus, targeting the E2F3–HIF-2α interaction may be a promising approach to ccRCC treatment.

RhoB Acts as a Tumor Suppressor That Inhibits Malignancy of Clear Cell Renal Cell Carcinoma.

This study aims to investigate the biological role of RhoB in clear cell renal cell carcinoma (ccRCC). The expression of RhoB was examined in specimens of patients and cell lines by Western blot and Immunohistochemistry. The correlation between RhoB expression and clinicopathologic variables was also analyzed. The effects of RhoB on cell proliferation, cell cycle, cell apoptosis, and invasion/migration were detected by over-expression and knockdown of RhoB level in ccRCC cells via plasmids and RNAi. The results showed that RhoB was low-expressed in ccRCC surgical specimens and cell lines compared with adjacent normal renal tissues and normal human renal proximal tubular epithelial cell lines (HKC), and its protein expression level was significantly associated with the tumor pathologic parameter embracing tumor size(P = 0.0157), pT stage(P = 0.0035), TNM stage(P = 0.0024) and Fuhrman tumor grade(P = 0.0008). Further, over-expression of RhoB remarkably inhibited the cancer cell proliferation, colony formation and promoted cancer cell apoptosis, and aslo reduced the invasion and migration ability of ccRCC cells. Interestingly, up-regulation of RhoB could induce cell cycle arrest in G2/M phase and led to cell cycle regulators(CyclineB1,CDK1) and pro-apoptotic protein(casp3,casp9) aberrant expression. Moreover, knockdown of RhoB in HKC cells promoted cell proliferation and migration. Taken together, our study indicates that RhoB expression is decreased in ccRCC carcinogenesis and progression. Up-regulation of RhoB significantly inhibits ccRCC cell malignant phenotype. These findings show that RhoB may play a tumor suppressive role in ccRCC cells, raising its potential value in futural therapeutic target for the patients of ccRCC.

Tumor suppressive microRNA‑429 regulates cellular function by targeting VEGF in clear cell renal cell carcinoma.

Clear cell renal cell carcinoma (ccRCC) is the predominant and most aggressive type of kidney malignancy, however, the mechanism underlying its carcinogenesis remains to be elucidated. The present study aimed to determine the expression and function of microRNA (miR)‑429 in ccRCC carcinogenesis. Reverse transcription‑quantitative polymerase chain reaction (RT‑qPCR) was used to detect the expression of miR‑429 in ccRCC specimens. Following transfection of miR‑429 synthetic mimics, the expression of miR‑429 was examined and cell proliferation, cell migration, apoptosis and luciferase assays were conducted in ccRCC cell lines. The results demonstrated that expression of miR‑429 was decreased in ccRCC cells. In addition, upregulation of miR‑429 by transfection of mimics reduced cellular proliferation and migration, and induced apoptosis in ACHN and 786‑0 cell lines. Furthermore, miR‑429 decreased the 3'UTR luciferase activity of vascular endothelial growth factor (VEGF) and c‑MYC, and RT‑qPCR analysis demonstrated that the cancer cells transfected with miR‑429 mimics exhibited decreased expression of VEGF, but not c‑MYC. To the best of our knowledge, the present study was the first to reveal that downregulated miR‑429 functioned as a tumor suppressor by restraining cellular proliferation and migration, and inducing apoptosis, as well as targeting VEGF in ccRCC cells.

Overexpression of Numb suppresses growth, migration, and invasion of human clear cell renal cell carcinoma cells.

The objective of the study was to investigate the impact of Numb on cell growth, cell migration, and invasion in human clear cell renal cell carcinoma (ccRCC). Endogenous expression of Numb was evaluated in the ccRCC cell lines (786-O, Caki-1, and Caki-2) and control reference human renal proximal tubular epithelial cells. Numb expression was decreased in the ccRCC cells compared with the control cells (P < 0.01). Then, 786-O and Caki-1 cells described as suitable transfection hosts were used in transfection to carry out biological function studies. The three experimental groups were as follows: Numb-ORF (transfected with Numb-ORF plasmid), blank-vector (transfected with pCMV6-entry), and cell-alone group (no DNA). Numb expression in the Numb-ORF groups was significantly higher than that in the controls (P < 0.01). Cell growth was remarkably reduced (P < 0.01), and the number of migrating or invading cells was reduced (P < 0.01) in the Numb-ORF groups compared with controls. Furthermore, the ratio of G0/G1 phase in the Numb-ORF group of 786-O cells was increased, and the S phase fraction and proliferation index was decreased (P < 0.01). Cyclin D1 and MMP-9 expression was reduced in the Numb-ORF groups compared with controls. Here, we have provided data for attenuated Numb expression in the ccRCC cells. Overexpression of Numb could induce G0/G1 phase arrest and inhibit cell proliferation, migration, and invasion. The suppressive effects might be due to downregulation of cyclin D1 or MMP-9 expression. Taken together, our data suggest that Numb may possibly function as a tumor suppressor involved in the carcinogenesis of ccRCC.

Mutational status of VHL gene and its clinical importance in renal clear cell carcinoma

The most common subtype of renal cell carcinoma is the clear cell type (ccRCC), accounting for 75 % of cases. Inactivation of VHL gene is thought to be an early event in ccRCC carcinogenesis. Our intention was to assess whether VHL mutational status might provide useful predictive or prognostic information in patients with ccRCC. VHL messenger RNA (mRNA) expression was analyzed by in situ hybridization and its protein by immunohistochemistry on a tissue microarray containing samples from 148 cases. This was validated by qRT-PCR on 62 cases, for which RNA was available. The mutation status was assessed in 91 cases by Sanger sequencing. VHL was found mutated in 57 % of cases, with missense mutations in 26 %, nonsense in 5 %, splice site in 13 %, deletions in 39 %, indels in 8 %, duplications in 8 %, and insertions in 2 % of the cases. The prevalence of mutations by exon was the following: exon 1, 47 %; exon 2, 27 %; and exon 3, 13 %. VHL protein was expressed in a high number of cases (80 %), but significant correlations were not found between protein expression, clinical data, and survival. Importantly, of the 91 samples evaluated by sequencing, 45 were mutated, and 87 % of those were strongly positive. We found 32 novel mutations in the VHL gene in ccRCC. The presence of mutations was not concordant with mRNA or protein expression. Nonsense mutations of the VHL gene appear to be related with poorer prognosis and survival.

Dysregulation of the beta-catenin complex as an independent predictor of oncological outcomes in patients with ccRCC.

493 Background: Epithelial to mesenchymal transition (EMT) is thought to play a crucial role in cancer progression and development of metastasis. Thus, we evaluated dysregulation of beta-catenin as a part of EMT and its clinical implications in patients with clear cell renal cell carcinoma (ccRCC). Methods: Immunohistochemical staining was performed for beta-catenin on tissue microarrays of patients with ccRCC. Membranous and cytoplasmatic beta-catenin expression patterns were assessed separately. Beta-catenin was considered normal if none or only one component was abnormal and was considered dysregulated if both components were abnormal. Differences in pathological characteristics between both groups were investigated. Differences in recurrence-free survival (RFS) and cancer-specific survival (CSS) were assessed with the Kaplan-Meier method. Uni- and multivariate Cox proportional hazard models were used to assess independent predictors of oncological outcomes. Results: 406 patients with a median follow-up of 58 months were included. Overall, 52 (12.8%) and 25 (6.2%) patients recurred and died of ccRCC. Beta-catenin was dysregulated in 70 (17.2%) patients. Dysregulation of beta-catenin was significantly associated with adverse pathologic features, such as higher T-stage, nodal positivity, higher grade, presence of tumor thrombus, sarcomatoid features, necrosis and LVI (all p&lt;0.001). Patients with dysregulated beta-catenin had inferior RFS and CSS (both p&lt;0.001). In multivariate analysis adjusting for tumor stage, nodal status and grade, dysregulation of beta-catenin was an independent predictor of RFS (HR 2.2, 95%CI 1.2-3.9, p=0.008) and CSS (HR 2.4, 95%CI 1.1-5.6, p=0.044). Conclusions: Our results indicate that dysregulation of beta-catenin may be an important phenomenon in ccRCC carcinogenesis. These findings support further study of beta-catenin and systematic assessment of EMT in ccRCC.

Activation of HIF2α in Kidney Proximal Tubule Cells Causes Abnormal Glycogen Deposition but not Tumorigenesis

Renal cell carcinoma (RCC) is the most common primary cancer arising from the kidney in adults, with clear cell renal cell carcinoma (ccRCC) representing approximately 75% of all RCCs. Increased expression of the hypoxia-induced factors-1α (HIF1α) and HIF2α has been suggested as a pivotal step in ccRCC carcinogenesis, but this has not been thoroughly tested. Here, we report that expression of a constitutively activated form of HIF2α (P405A, P530A, and N851A, named as HIF2αM3) in the proximal tubules of mice is not sufficient to promote ccRCC by itself, nor does it enhance HIF1αM3 oncogenesis when coexpressed with constitutively active HIF1αM3. Neoplastic transformation in kidneys was not detected at up to 33 months of age, nor was increased expression of Ki67 (MKI67), γH2AX (H2AFX), or CD70 observed. Furthermore, the genome-wide transcriptome of the transgenic kidneys does not resemble human ccRCC. We conclude that a constitutively active HIF2α is not sufficient to cause neoplastic transformation of proximal tubules, arguing against the idea that HIF2α activation is critical for ccRCC tumorigenesis.

Expression of CMTM3 and CMTM5 in clear cell renal cell carcinoma and its significance

Objective To investigate the expression of CKLF-like MARVEL transmembrane (CMTM)domain-containing family in clear cell renal cell carcinoma(ccRCC)and its significance.Methods Seventy-five samples of ccRCC were collected,including 50 males and 25 females,mean age (59 ± 10)years.There were 34 cases in clinical stage Ⅰ,23 cases in stage Ⅱ,14 cases in stage Ⅲ and 4 cases in stage Ⅳ.The pathological differentiation was 3 cases of grade Ⅰ,1 case of grade Ⅰ-Ⅱ,35 cases of grade Ⅱ,10 cases of grade Ⅱ-Ⅲ,18 cases of grade Ⅲ,3 cases of grade Ⅲ-Ⅳ and 5 cases of grade Ⅳ.The expression of CMTM3 and CMTM5 proteins in 75 cases of ccRCC and corresponding adjacent normal kidney tissues was detected by tissue microarray and immunohistochemistry.Results The positive expression rate of CMTM3 and CMTM5 was 98.7％,97.3％ in the adjacent normal kidney tissues,and 44.0％,68.0％ in ccRCC tissues(P ＜ 0.05).The expression of CMTM3 and CMTM5 had no correlation with the gender,age,clinical staging and pathological differentiation(P ＞ 0.05).Conclusion CMTM3 and CMTM5 could be ccRCC suppressor genes,and their mutation or methylation might be an early event in the carcinogenesis of ccRCC,thus promise them to be potential biomarkers in early diagnosis. Key words: CKLF-like MARVEL transmembrane domain-containing family; Clear cell renal cell carcinoma; Immunohistochemistry; Tissue microarray

Abstract LB-486: Overexpression of a mutated, constitutively active HIF2α promotes the carcinogenesis of TRACK mouse

Abstract Background: VHL disease patients have an increased risk of developing clear cell renal cell carcinomas (ccRCC). Increased expression of HIF1α and/or HIF2α has been proposed as a key step in ccRCC carcinogenesis. We recently reported a mouse model of VHL renal cancer, the TRACK model (Fu et al, Cancer research. 2011;71(21):6848-56.). In the TRACK model, proximal tubule (PT) cell overexpression of a triple mutant (P402A, P564A and N803A) HIF1α in the mouse mimics human VHL kidney disease. Methods: Here we report a mouse model expressing a triple mutant (P405A, P531A and N847A) HIF2α in PT cells. Mutant HIF2α was expressed in both WT and HIF1α-expressing C57BL/6 mice. Results: Transgenic (TG) mice expressing this HIF2α construct specifically in PT cells exhibit vacuolization consistent with glycogen accumulation and hydropic degeneration. The activation of HIF2α was confirmed by increased expression of HIF2α target genes, e.g. CA9. Neoplastic transformation was not observed in the kidneys of HIF2α TG+ mice. In HIF1α/HIF2α-expressing mice, disorganized PT cells mimicking in situ carcinoma was observed in 5 mo old mouse kidneys, which was seen only at 14 mo in mice expressing only mutant HIF1α. Conclusions: These data suggest HIF2α accelerates carcinogenesis in the mutant HIF1α TRACK model. These mouse models provide excellent models to study VHL renal disease and carcinogenesis, and provide an opportunity for chemoprevention studies. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr LB-486. doi:1538-7445.AM2012-LB-486

Integrated Profiling of MicroRNAs and mRNAs: MicroRNAs Located on Xq27.3 Associate with Clear Cell Renal Cell Carcinoma

BackgroundWith the advent of second-generation sequencing, the expression of gene transcripts can be digitally measured with high accuracy. The purpose of this study was to systematically profile the expression of both mRNA and miRNA genes in clear cell renal cell carcinoma (ccRCC) using massively parallel sequencing technology.MethodologyThe expression of mRNAs and miRNAs were analyzed in tumor tissues and matched normal adjacent tissues obtained from 10 ccRCC patients without distant metastases. In a prevalence screen, some of the most interesting results were validated in a large cohort of ccRCC patients.Principal FindingsA total of 404 miRNAs and 9,799 mRNAs were detected to be differentially expressed in the 10 ccRCC patients. We also identified 56 novel miRNA candidates in at least two samples. In addition to confirming that canonical cancer genes and miRNAs (including VEGFA, DUSP9 and ERBB4; miR-210, miR-184 and miR-206) play pivotal roles in ccRCC development, promising novel candidates (such as PNCK and miR-122) without previous annotation in ccRCC carcinogenesis were also discovered in this study. Pathways controlling cell fates (e.g., cell cycle and apoptosis pathways) and cell communication (e.g., focal adhesion and ECM-receptor interaction) were found to be significantly more likely to be disrupted in ccRCC. Additionally, the results of the prevalence screen revealed that the expression of a miRNA gene cluster located on Xq27.3 was consistently downregulated in at least 76.7% of ∼50 ccRCC patients.ConclusionsOur study provided a two-dimensional map of the mRNA and miRNA expression profiles of ccRCC using deep sequencing technology. Our results indicate that the phenotypic status of ccRCC is characterized by a loss of normal renal function, downregulation of metabolic genes, and upregulation of many signal transduction genes in key pathways. Furthermore, it can be concluded that downregulation of miRNA genes clustered on Xq27.3 is associated with ccRCC.

Histopathologic subtype-specific genomic profiles of renal cell carcinomas identified by high-resolution whole-genome single nucleotide polymorphism array analysis

To elucidate the novel and common genetic changes in histopathologic subtype-specific profiles of renal cell carcinomas (RCCs), a newly developed high-resolution whole-genome array analysis was applied. Human CNV370-Duo DNA Analysis BeadChip (genotype 370K) was used in a panel of 22 primary clear cell RCCs (ccRCCs), seven papillary RCCs (PRCCs) (six type II and one type I) and eight chromophobe RCCs (ChRCCs). In ccRCC, a chromosome 3p loss was identified in 95% of the carcinomas, suggesting that 3p loss is the first stage in ccRCC carcinogenesis. Other frequent changes included losses of 1p (23%), 3q (46%) and 8p (32%), and gains of 5q (32%), 7p (27%), 7q (27%) and 1q (23%). The most frequent chromosomal losses in PRCC (43%) were noted in 3p and 3q, followed by 29% of losses of 1p, 1q, 11q, 18q, 22p and 22q, and gains of 20q (57%), 20p (43%), 8q (43%) and 12q (43%). Loss of the entire chromosomes 1, 2, 6, 8, 10, 13 or 17 was noted in patients with ChRCC. A high-density single nucleotide polymorphism array analysis confirmed that partial chromosomal changes rarely occur in ChRCC. Additionally, 32 microdeletions and 10 microamplifications of less than 1 Mb were detected, which may represent potential candidate tumor suppressor genes and oncogenes, respectively.

Prognostic Significance of Gremlin1 ( GREM1) Promoter CpG Island Hypermethylation in Clear Cell Renal Cell Carcinoma

Gremlin1 (GREM1), a bone morphogenetic protein antagonist and putative angiogenesis-modulating gene, is silenced by promoter hypermethylation in human malignancies. Here we study GREM1 methylation in clear cell renal cell carcinoma (ccRCC) and its impact on tumor characteristics and clinical outcome. Three GREM1 promoter CpG island regions (i, ii, iii) were analyzed by methylation-specific PCR and/or bisulfite sequencing in ccRCC cell lines and ccRCCs from two independent patient series. Results were correlated with clinicopathological and angiogenic parameters. Bisulfite sequencing of ccRCC cell lines showed GREM1 methylation, associated with absence of GREM1 mRNA. GREM1 methylation prevalence in ccRCCs varied between regions: 55%, 24%, and 20% for regions i, ii, and iii, respectively. GREM1 region iii methylation was associated with increased tumor size (P = 0.02), stage (P = 0.013), grade (P = 0.04), tumor (P = 0.001), and endothelial cell (P = 0.0001) proliferation and decreased mean vessel density (P = 0.001) in a hospital-based ccRCC series (n = 150). In univariate analysis, GREM1 region iii methylated ccRCCs had a significant worse survival when compared with unmethylated ccRCCs (hazard ratio [HR] = 2.35, 95% confidence interval [CI]:1.29 to 4.28), but not in multivariate analysis (HR = 0.88, 95% CI: 0.45 to 1.74). In a population-based validation series (n = 185), GREM1 region iii methylation was associated with increased Fuhrman grade (P = 0.03) and decreased overall survival (P = 0.001) in univariate and multivariate analysis (HR = 2.32, 95% CI: 1.52 to 3.53 and HR = 2.27, 95% CI: 1.44 to 3.59, respectively). The strong correlation between GREM1 region iii promoter methylation and increased malignancy and its correlation with active angiogenesis indicates a role for GREM1 in ccRCC carcinogenesis and tumor angiogenesis.

Improved Identification of von Hippel-Lindau Gene Alterations in Clear Cell Renal Tumors

To provide a comprehensive, thorough analysis of somatic mutation and promoter hypermethylation of the von Hippel-Lindau (VHL) gene in the cancer genome, unique to clear cell renal cancer (ccRCC). Identify relationships between the prevalence of VHL gene alterations and alteration subtypes with patient and tumor characteristics. As part of a large kidney cancer case-control study conducted in Central Europe, we analyzed VHL mutations and promoter methylation in 205 well-characterized, histologically confirmed patient tumor biopsies using a combination of sensitive, high-throughput methods (endonuclease scanning and Sanger sequencing) and analysis of 11 CpG sites in the VHL promoter. We identified mutations in 82.4% of cases, the highest VHL gene mutation prevalence reported to date. Analysis of 11 VHL promoter CpG sites revealed that 8.3% of tumors were hypermethylated and all were mutation negative. In total, 91% of ccRCCs exhibited alteration of the gene through genetic or epigenetic mechanisms. Analysis of patient and tumor characteristics revealed that certain mutation subtypes were significantly associated with Fuhrman nuclear grade, metastasis, node positivity, and self-reported family history of RCC. Detection of VHL gene alterations using these accurate, sensitive, and practical methods provides evidence that the vast majority of histologically confirmed ccRCC tumors possess genetic or epigenetic alteration of the VHL gene and support the hypothesis that VHL alteration is an early event in ccRCC carcinogenesis. These findings also indicate that VHL molecular subtypes can provide a sensitive marker of tumor heterogeneity among histologically similar ccRCC cases for etiologic, prognostic, and translational studies.