Project description:Gene expression data from VHL teratomas comparing genes differentially expressed based on apoptotic response to tumor microenvironment. Abstract BACKGROUND: The risk relevance of the P81S von Hippel-Lindau (VHL) gene hotspot mutation identified in clear cell renal cell carcinoma from individuals exposed occupationally to trichloroethylene (TCE) is not known. VHL mutations in hereditary VHL syndrome strongly correlate with phenotypic associations, but specific sporadic mutations in VHL that uniquely alter its protein function may provide a selective growth advantage for somatic cells harboring these mutations. METHODS: VHL deficient (Vhl -/- ) mouse embryonic stem cells were generated that stably express wild-type, P81S, or R167Q human VHL protein. Under hypoxic conditions, cell lines were examined for hypoxia-inducible transcription factor family (HIF) stabilization and E3-ubiquitin ligase complex interactions. In vivo, teratomas were examined for tumor size, proliferation, apoptosis, and immunohistochemistry and subjected to gene expression analysis. Wild-type, R167Q, and P81S VHL-expressing teratomas were also exposed to 5 Gy ionizing radiation to quantify apoptotic response. Proliferation and apoptosis and teratoma growth were analyzed by either Student t test or analysis of variance with Bonferroni correction. All statistical tests were two-sided. RESULTS: The P81S VHL mutation produces deregulation of HIF factors in cell culture but exhibits a growth advantage in the tumor microenvironment, in part because of suppression of apoptosis (P81S mean = 0.9%, 95% confidence interval = 0.6 to 1.2%; WT mean = 7.6%; 95% confidence interval = 6.4 to 8.8%; P < .001) coupled with sustained proliferation. Transcriptional analysis of P81S teratomas revealed the induction of metabolic pathways, antiapoptotic genes, and global suppression of key DNA damage response genes not observed in VHL wild-type or R167Q mutants. In vivo irradiation exposure showed that P81S mutant is resistant to ionizing radiation-induced apoptosis. CONCLUSIONS: The TCE-associated P81S VHL mutation can initiate a unique adaptive response required for selective tumor growth through pleiotropic effects on metabolic diversification, apoptosis suppression, and alteration of the DNA damage response. Three genotypes of VHL teratomas were examined: Three replicate wildtype VHL, Three replicate R167Q VHL, and Four replicate P81S VHL (representing two replicates of two different P81S clones)

Project description:Renal cancer accounts for 2% to 3% of all adult malignancies in the US. In 2011 more than 64,770 new cases and 13,000 deaths were reported and the incidence is steadily increasing by 2.5% per year. Clear cell renal carcinoma (ccRCC) represents the majority (85% to 90%) of adult kidney cancers and is the most malignant. This cancer is characterized by an early loss of the von Hippel-Lindau tumor suppressor (VHL) on short arm of chromosome 3 in the majority of tumors (80%). It is a classic knowledge that loss of VHL results in an increased accumulation and activity of the hypoxia-inducible transcription factor (HIF), which in turns activates expression of genes promoting tumor growth. In that respect, induction of angiogenic factors induces blood flow through the tumors and delivery of nutrients and oxygen to cancer cells, while induction of genes inducing anaerobic glycolysis supports adaptation to reduced nutrients availability and shifts towards metabolic pathways promoting tumor growth. Recently we have discovered another tumor suppressing pathway regulated by VHL. We found that VHL is a major regulator of the process of macroautophagy (autophagy) (ref). We identified that VHL induces expression of a microRNA, miR-204, which in turn inhibits activity of a major regulator required for the formation of autophagosome, LC3B. LC3B-mediated autophagy is necessary for the ccRCC tumor growth, and inhibition of this process by VHL and miR-204 significantly contributes to the tumor suppression. Most importantly, we discovered that VHL by inhibiting activity of HIF, induced expression and activity of an LC3B paralog, LC3C. In contrast to LC3B, LC3C acts as a tumor suppressor, indicating the specificity and complexity of different autophagic programs. Integrating these novel data with the established role of VHL in regulating angiogenesis produces a more global picture of VHL as a master tumor suppressor that regulates nutrient access for renal cancer cells from both extracellular and intracellular sources. In the process of searching for other genes induced by VHL that could participate in the tumor suppressing activity of VHL, we discovered that reconstitution of VHL in RCC cells induces enrichment of genes expressed from the Smith-Magenis locus (SM), located on the short arm of chromosome 17p11.2. Smith-Magenis syndrome is a complex neurobehevioural disorder, characterized by intellectual impairment, craniofacial and skeletal anomalies and sleep disturbance. Recently, deletions or mutations of one specific gene in the SM locus, RAI1, (retinoic acid induced 1), were shown to be responsible for the syndrome. Interestingly, this locus contains another kidney tumor suppressor gene, folliculin (FLCN), of which activity is lost in the genetic dominant disorder, Birt-Hogg-Dube syndrome (BHD). BHD is characterized by skin fibrofolliculomas, pulmonary cysts and spontaneous pneumothorax, as well as renal cancer of mixed histological types, including chromophobe, oncocytic, clear cell and papillary type. Here we show that VHL regulates expression of FLCN, and in turn FLCN contributes to the VHL-mediated suppression of tumor growth. Two-condition experiment, VHL(-) vs. VHL(+). 4 biological replicates in each group. Two dual-channel arrays with VHL(+) on Cy5 and VHL(-) on Cy3, and two dual-channel arrays with flipped samples.

Project description:Renal cancer accounts for 2% to 3% of all adult malignancies in the US. In 2011 more than 64,770 new cases and 13,000 deaths were reported and the incidence is steadily increasing by 2.5% per year. Clear cell renal carcinoma (ccRCC) represents the majority (85% to 90%) of adult kidney cancers and is the most malignant. This cancer is characterized by an early loss of the von Hippel-Lindau tumor suppressor (VHL) on short arm of chromosome 3 in the majority of tumors (80%). It is a classic knowledge that loss of VHL results in an increased accumulation and activity of the hypoxia-inducible transcription factor (HIF), which in turns activates expression of genes promoting tumor growth. In that respect, induction of angiogenic factors induces blood flow through the tumors and delivery of nutrients and oxygen to cancer cells, while induction of genes inducing anaerobic glycolysis supports adaptation to reduced nutrients availability and shifts towards metabolic pathways promoting tumor growth. Recently we have discovered another tumor suppressing pathway regulated by VHL. We found that VHL is a major regulator of the process of macroautophagy (autophagy) (ref). We identified that VHL induces expression of a microRNA, miR-204, which in turn inhibits activity of a major regulator required for the formation of autophagosome, LC3B. LC3B-mediated autophagy is necessary for the ccRCC tumor growth, and inhibition of this process by VHL and miR-204 significantly contributes to the tumor suppression. Most importantly, we discovered that VHL by inhibiting activity of HIF, induced expression and activity of an LC3B paralog, LC3C. In contrast to LC3B, LC3C acts as a tumor suppressor, indicating the specificity and complexity of different autophagic programs. Integrating these novel data with the established role of VHL in regulating angiogenesis produces a more global picture of VHL as a master tumor suppressor that regulates nutrient access for renal cancer cells from both extracellular and intracellular sources. In the process of searching for other genes induced by VHL that could participate in the tumor suppressing activity of VHL, we discovered that reconstitution of VHL in RCC cells induces enrichment of genes expressed from the Smith-Magenis locus (SM), located on the short arm of chromosome 17p11.2. Smith-Magenis syndrome is a complex neurobehevioural disorder, characterized by intellectual impairment, craniofacial and skeletal anomalies and sleep disturbance. Recently, deletions or mutations of one specific gene in the SM locus, RAI1, (retinoic acid induced 1), were shown to be responsible for the syndrome. Interestingly, this locus contains another kidney tumor suppressor gene, folliculin (FLCN), of which activity is lost in the genetic dominant disorder, Birt-Hogg-Dube syndrome (BHD). BHD is characterized by skin fibrofolliculomas, pulmonary cysts and spontaneous pneumothorax, as well as renal cancer of mixed histological types, including chromophobe, oncocytic, clear cell and papillary type. Here we show that VHL regulates expression of FLCN, and in turn FLCN contributes to the VHL-mediated suppression of tumor growth.

Project description:Altered metabolism is an important part of malignant transformation of tumor cells. Oncogenic transformation may reprogram tumor metabolism and render tumor cells addicted to extracellular nutrients. Such nutrient addictions associated with oncogenic mutations may offer therapeutic opportunities; however, it remains difficult to predict these nutrient addictions. Here, we performed a nutrigenetic screen to determine the phenotypes of isogenic pairs of clear-cell renal cancer cells (ccRCC) with or without VHL upon the deprivation of individual amino acids. We identified that cystine deprivation triggered rapid programmed necrosis in VHL-deficient RCC, but not in their VHL-restored counterparts. Similar cystine addiction was also observed in VHL-deficient primary RCC tumors cells. Blockage of cystine uptake significantly delayed xenograft growth of ccRCC. Importantly, cystine deprivation triggered similar metabolic changes regardless of VHL status. Therefore, metabolic differences due to cystine deprivation are not different enough to readily explain the distinct fate of life vs. death in VHL-deficient and restored cell.. Instead, we found that increased levels of TNFÎ± associated with VHL loss in the VHL-deficient RCC force them to rely on intact RIPK1 to inhibit apoptosis. However, this pre-existing elevated TNFÎ± in the VHL-deficient ccRCC renders these cells susceptible to the necrosis signaling triggered by cystine deprivation. In addition, we identified that cystine-deprived necrosis in VHL-deficient RCC depends on reciprocal amplification of the Src-p38-Noxa signaling and TNFÎ±-RIP1/3-MLKL necrosis pathways that culminate in MLKL oligomerization and programmed necrosis. Together, our data reveal that the contextual cystine-addictions in VHL-deficient ccRCC is dependent on activating pre-existing oncogenic pathways to trigger programmed necrosis. RNA was extracted by RNAeasy kits (Qiagen) from the RCC4 Vec and VHL-reconstituted cells which were exposed to the control full DMEM or cystine deprived DMEM media for 6 hours (three replicates in each condition).

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Pleiotropic Effects of the Trichloroethylene-Associated P81S VHL Mutation on Metabolism, Apoptosis and ATM-Mediated DNA Damage Response

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