Epigenetic inactivation of the p53-induced long noncoding RNA TP53 target 1 in human cancer.

Long noncoding RNAs (lncRNAs) are important regulators of cellular homeostasis. However, their contribution to the cancer phenotype still needs to be established. Herein, we have identified a p53-induced lncRNA, TP53TG1, that undergoes cancer-specific promoter hypermethylation-associated silencing. In vitro and in vivo assays identify a tumor-suppressor activity for TP53TG1 and a role in the p53 response to DNA damage. Importantly, we show that TP53TG1 binds to the multifaceted DNA/RNA binding protein YBX1 to prevent its nuclear localization and thus the YBX1-mediated activation of oncogenes. TP53TG1 epigenetic inactivation in cancer cells releases the transcriptional repression of YBX1-targeted growth-promoting genes and creates a chemoresistant tumor. TP53TG1 hypermethylation in primary tumors is shown to be associated with poor outcome. The epigenetic loss of TP53TG1 therefore represents an altered event in an lncRNA that is linked to classical tumoral pathways, such as p53 signaling, but is also connected to regulatory networks of the cancer cell.

Mutations in JMJD1C are involved in Rett syndrome and intellectual disability.

PURPOSE: Autism spectrum disorders are associated with defects in social response and communication that often occur in the context of intellectual disability. Rett syndrome is one example in which epilepsy, motor impairment, and motor disturbance may co-occur. Mutations in histone demethylases are known to occur in several of these syndromes. Herein, we aimed to identify whether mutations in the candidate histone demethylase JMJD1C (jumonji domain containing 1C) are implicated in these disorders. METHODS: We performed the mutational and functional analysis of JMJD1C in 215 cases of autism spectrum disorders, intellectual disability, and Rett syndrome without a known genetic defect. RESULTS: We found seven JMJD1C variants that were not present in any control sample (~ 6,000) and caused an amino acid change involving a different functional group. From these, two de novo JMJD1C germline mutations were identified in a case of Rett syndrome and in a patient with intellectual disability. The functional study of the JMJD1C mutant Rett syndrome patient demonstrated that the altered protein had abnormal subcellular localization, diminished activity to demethylate the DNA damage-response protein MDC1, and reduced binding to MECP2. We confirmed that JMJD1C protein is widely expressed in brain regions and that its depletion compromises dendritic activity. CONCLUSIONS: Our findings indicate that mutations in JMJD1C contribute to the development of Rett syndrome and intellectual disability.Genet Med 18 1, 378-385.

Regulation of SNAIL1 and E-cadherin function by DNMT1 in a DNA methylation-independent context.

Mammalian DNA methyltransferase 1 (DNMT1) is essential for maintaining DNA methylation patterns after cell division. Disruption of DNMT1 catalytic activity results in whole genome cytosine demethylation of CpG dinucleotides, promoting severe dysfunctions in somatic cells and during embryonic development. While these observations indicate that DNMT1-dependent DNA methylation is required for proper cell function, the possibility that DNMT1 has a role independent of its catalytic activity is a matter of controversy. Here, we provide evidence that DNMT1 can support cell functions that do not require the C-terminal catalytic domain. We report that PCNA and DMAP1 domains in the N-terminal region of DNMT1 are sufficient to modulate E-cadherin expression in the absence of noticeable changes in DNA methylation patterns in the gene promoters involved. Changes in E-cadherin expression are directly associated with regulation of ß-catenin-dependent transcription. Present evidence suggests that the DNMT1 acts on E-cadherin expression through its direct interaction with the E-cadherin transcriptional repressor SNAIL1.

Antitumor activity of fibroblast growth factor receptor 3-specific immunotoxins in a xenograft mouse model of bladder carcinoma is mediated by apoptosis.

Human single-chain Fv directed against fibroblast growth factor receptor 3 (FGFR3) have been shown to block proliferation of RT112 bladder carcinoma cells in vitro. Here, we examined the ability of the recombinant gelonin toxin (rGel) to enhance this inhibitory effect in vitro and in vivo on the bladder cancer cell line RT112 and the corresponding xenografts. Immunotoxins were genetically engineered by fusing FGFR3-specific Fv fragments (3C) to the NH(2) terminus of rGel and expressed as a soluble protein in Escherichia coli. The 3C/rGel fusion construct showed an IC(50) of 200 nmol/L against log-phase RT112 cells compared with 1,500 nmol/L for free rGel. Immunofluorescence studies showed that the 3C/rGel construct internalized rapidly into the cytoplasm of RT112 cells within 1 h of exposure. The mechanism of immunotoxin-induced cell death was found to be mediated by apoptosis. RT112 tumor xenografts in severe combined immunodeficient mice treated with 50 mg/kg 3C/rGel exhibited considerable growth delay relative to control tumors and a significant reduction of 55% to 70% in mean tumor size. Immunohistochemical analysis showed that tumors from mice treated with 3C/rGel displayed considerable apoptotic damage compared with control groups. Subcellular location of FGFR3 in immunotoxin-treated tumors indicated a translocation of FGFR3 to the nuclear membrane in contrast to tumors from saline-treated controls. These results show that FGFR3-driven immunotoxins may be an effective therapeutic agent against human bladder and other tumor types overexpressing FGFR3.

Dynamic clonal remodelling in breast cancer metastases is associated with subtype conversion.

BACKGROUND: Changes in the clinical subtype (CS) and intrinsic subtype (IS) between breast cancer (BC) metastases and corresponding primary tumours have been reported. However, their relationship with tumour genomic changes remains poorly characterised. Here, we analysed the association between genomic remodelling and subtype conversion in paired primary and metastatic BC samples. METHODS: A total of 57 paired primary and metastatic tumours from GEICAM/2009-03 (ConvertHER, NCT01377363) study participants with centrally assessed CS (n = 57) and IS (n = 46) were analysed. Targeted capture and next-generation sequencing of 202 genes on formalin-fixed paraffin-embedded samples was performed. The cancer cell fraction (CCF) of mutations in primary and metastatic pairs was estimated as a surrogate of tumour clonal architecture. Changes in mutation CCF between matched primary and metastatic tumours were analysed in the presence or absence of subtype conversion. FINDINGS: CS conversion occurred in 24.6% and IS conversion occurred in 36.9% of metastases. Primary tumours and metastases had a median of 11 (range, 3-29) and 9 (range, 1-38) mutations, respectively (P = 0.05). Overall, mutations in metastases showed a higher estimated CCF than in primary tumours (median CCF, 0.51 and 0.47, respectively; P = 0.042), consistent with increased clonal homogeneity. The increase in mutation CCF was significant in CS-converted (P = 0.04) but not in IS-converted (P = 0.48) metastases. Clonal remodelling was highest in metastases from hormone receptor-positive and human epidermal growth factor 2 (HER2)-positive tumours (P = 0.006). CONCLUSIONS: Mutations in BC metastases showed significantly higher estimated CCF than primary tumours. CCF changes were more prominent in metastases with CS conversion. Our findings suggest that changes in BC subtypes are linked to clonal remodelling during BC evolution.

Epigenetic loss of the endoplasmic reticulum-associated degradation inhibitor SVIP induces cancer cell metabolic reprogramming.

The endoplasmic reticulum (ER) of cancer cells needs to adapt to the enhanced proteotoxic stress associated with the accumulation of unfolded, misfolded and transformation-associated proteins. One way by which tumors thrive in the context of ER stress is by promoting ER-Associated Degradation (ERAD), although the mechanisms are poorly understood. Here, we show that the Small p97/VCP Interacting Protein (SVIP), an endogenous inhibitor of ERAD, undergoes DNA hypermethylation-associated silencing in tumorigenesis to achieve this goal. SVIP exhibits tumor suppressor features and its recovery is associated with increased ER stress and growth inhibition. Proteomic and metabolomic analyses show that cancer cells with epigenetic loss of SVIP are depleted in mitochondrial enzymes and oxidative respiration activity. This phenotype is reverted upon SVIP restoration. The dependence of SVIP hypermethylated cancer cells on aerobic glycolysis and glucose was also associated with sensitivity to an inhibitor of the glucose transporter GLUT1. This could be relevant to the management of tumors carrying SVIP epigenetic loss, because these occur in high-risk patients who manifest poor clinical outcomes. Overall, our study provides insights into how epigenetics helps deal with ER stress and how SVIP epigenetic loss in cancer may be amenable to therapies that target glucose transporters.

CHL1 hypermethylation as a potential biomarker of poor prognosis in breast cancer.

The CHL1 gene encodes a cell-adhesion molecule proposed as being a putative tumour-suppressor gene in breast cancer (BC). However, neither the underlying molecular mechanisms nor the clinical value of CHL1 downregulation in BC has been explored. The methylation status of three CpG sites in the CHL1 promoter was analysed by pyrosequencing in neoplastic biopsies from 142 patients with invasive BC and compared with that of non-neoplastic tissues. We found higher CHL1 methylation levels in breast tumours than in non-neoplastic tissues, either from mammoplasties or adjacent-to-tumour, which correlated with lower levels of protein expression in tumours measured by immunohistochemistry. A panel of five BC cell lines was treated with two epigenetic drugs, and restoration of CHL1 expression was observed, indicating in vitro dynamic epigenetic regulation. CHL1 was silenced by shRNA in immortalized but non-neoplastic mammary cells, and enhanced cell proliferation and migration, but not invasion, were found by real-time cell analysis. The prognostic value of CHL1 hypermethylation was assessed by the log-rank test and fitted in a Cox regression model. Importantly, CHL1 hypermethylation was very significantly associated with shorter progression-free survival in our BC patient series, independent of age and stage (p = 0.001). In conclusion, our results indicate that CHL1 is downregulated by hypermethylation and that this epigenetic alteration is an independent prognostic factor in BC.

Targeting the extracellular domain of fibroblast growth factor receptor 3 with human single-chain Fv antibodies inhibits bladder carcinoma cell line proliferation.

PURPOSE: Previous gene expression studies have shown that fibroblast growth factor receptor 3 (FGFR3) is overexpressed in early stages of bladder cancer. To study the potential use of therapeutic antibodies against FGFR3, we have produced a collection of human single-chain Fv (scFv) antibody fragments by using phage display libraries. EXPERIMENTAL DESIGN: Two "naïve" semi-synthetic human scFv libraries were used to select antibodies against the extracellular domain of FGFR3alpha(IIIc). The reactivity of the selected scFvs with a recombinant FGFR3 was characterized by an enzyme immunoassay and surface plasmon resonance analysis and with RT112 bladder carcinoma cells by a fluorescence-activated cell sorter. The capacity of the selected scFvs to block RT112 cell proliferation was determined. RESULTS: We have isolated six human scFv antibody fragments directed against FGFR3. These human scFvs specifically bound FGFR3, but not the homologous molecule FGFR1. Biacore analysis was used to determine the affinity constants, which ranged from 12 to 40 nmol/L. Competition analysis showed that the FGF9 ligand was able to block the binding of two scFvs, 3C and 7D, to FGFR3, whereas FGF1 only blocked 7D. Immunoprecipitation and flow cytometric analysis confirmed the specificity of the antibodies to native membrane FGFR3. Two scFvs, 3C and 7D, gave an strong immunofluorescence staining of RT112 cells. Moreover, they recognized equally well wild-type and mutant FGFR3 containing the activating mutation S249C. Furthermore, they blocked proliferation of RT112 cells in a dose- and FGF-dependent manner. CONCLUSION: Our results suggest that these human anti-FGFR3 scFv antibodies may have potential applications as antitumoral agents in bladder cancer.

Epigenetic activation of a cryptic TBC1D16 transcript enhances melanoma progression by targeting EGFR.

Metastasis is responsible for most cancer-related deaths, and, among common tumor types, melanoma is one with great potential to metastasize. Here we study the contribution of epigenetic changes to the dissemination process by analyzing the changes that occur at the DNA methylation level between primary cancer cells and metastases. We found a hypomethylation event that reactivates a cryptic transcript of the Rab GTPase activating protein TBC1D16 (TBC1D16-47 kDa; referred to hereafter as TBC1D16-47KD) to be a characteristic feature of the metastatic cascade. This short isoform of TBC1D16 exacerbates melanoma growth and metastasis both in vitro and in vivo. By combining immunoprecipitation and mass spectrometry, we identified RAB5C as a new TBC1D16 target and showed that it regulates EGFR in melanoma cells. We also found that epigenetic reactivation of TBC1D16-47KD is associated with poor clinical outcome in melanoma, while conferring greater sensitivity to BRAF and MEK inhibitors.

A DERL3-associated defect in the degradation of SLC2A1 mediates the Warburg effect.

Cancer cells possess aberrant proteomes that can arise by the disruption of genes involved in physiological protein degradation. Here we demonstrate the presence of promoter CpG island hypermethylation-linked inactivation of DERL3 (Derlin-3), a key gene in the endoplasmic reticulum-associated protein degradation pathway, in human tumours. The restoration of in vitro and in vivo DERL3 activity highlights the tumour suppressor features of the gene. Using the stable isotopic labelling of amino acids in cell culture workflow for differential proteome analysis, we identify SLC2A1 (glucose transporter 1, GLUT1) as a downstream target of DERL3. Most importantly, SLC2A1 overexpression mediated by DERL3 epigenetic loss contributes to the Warburg effect in the studied cells and pinpoints a subset of human tumours with greater vulnerability to drugs targeting glycolysis.

Proteomics-based validation of genomic data: applications in colorectal cancer diagnosis.

Multiple factors are involved in the translation of functional genomic results into proteins for proteome research and target validation on tumoral tissues. In this report, genes were selected by using DNA microarrays on a panel of colorectal cancer (CRC) paired samples. A large number of up-regulated genes in colorectal cancer patients were investigated for cellular location, and those corresponding to membrane or extracellular proteins were used for a non-biased expression in Escherichia coli. We investigated different sources of cDNA clones for protein expression as well as the influence of the protein size and the different tags with respect to protein expression levels and solubility in E. coli. From 29 selected genes, 21 distinct proteins were finally expressed as soluble proteins with, at least, one different fusion protein. In addition, seven of these potential markers (ANXA3, BMP4, LCN2, SPARC, SPP1, MMP7, and MMP11) were tested for antibody production and/or validation. Six of the seven proteins (all except SPP1) were confirmed to be overexpressed in colorectal tumoral tissues by using immunoblotting and tissue microarray analysis. Although none of them could be associated to early stages of the tumor, two of them (LCN2 and MMP11) were clearly overexpressed in late Dukes' stages (B and C). This proteomic study reveals novel clues for the assembly of a robust and highly efficient high throughput system for the validation of genomic data. Moreover it illustrates the different difficulties and bottlenecks encountered for performing a quick conversion of genomic results into clinically useful proteins.