Promoter methylation of the RGC32 gene in nonsmall cell lung cancer

RGC-32 mediates proinflammatory and profibrotic pathways in immune-mediated kidney disease

Systemic lupus erythematosus is an autoimmune disease that results in immune-mediated damage to kidneys and other organs. We investigated the role of response gene to complement-32 (RGC-32), a proinflammatory and profibrotic mediator induced by TGFβ and C5b-9, in nephrotoxic nephritis (NTN), an experimental model that mimics human lupus nephritis. Proteinuria, loss of renal function and kidney histopathology were attenuated in RGC-32 KO NTN mice. RGC-32 KO NTN mice displayed downregulation of the CCL20/CCR6 and CXCL9/CXCR3 ligand/receptor pairs resulting in decreased renal recruitment of IL-17+ and IFNγ+ cells and subsequent decrease in the influx of innate immune cells. RGC-32 deficiency attenuated renal fibrosis as demonstrated by decreased deposition of collagen I, III and fibronectin. Thus, RGC-32 is a unique mediator shared by the Th17 and Th1 dependent proinflammatory and profibrotic pathways and a potential novel therapeutic target in the treatment of immune complex mediated glomerulonephritis such as lupus nephritis.

Regulator of Cell Cycle Protein (RGCC/RGC-32) Protects against Pulmonary Fibrosis

Some previous studies in tissue fibrosis have suggested a profibrotic contribution from elevated expression of a protein termed either RGCC (regulator of cell cycle) or RGC-32 (response gene to complement 32 protein). Our analysis of public gene expression datasets, by contrast, revealed a consistent decrease in RGCC mRNA levels in association with pulmonary fibrosis. Consistent with this observation, we found that stimulating primary adult human lung fibroblasts with transforming growth factor (TGF)-β in cell cultures elevated collagen expression and simultaneously attenuated RGCC mRNA and protein levels. Moreover, overexpression of RGCC in cultured lung fibroblasts attenuated the stimulating effect of TGF-β on collagen levels. Similar to humans with pulmonary fibrosis, the levels of RGCC were also decreased in vivo in lung tissues of wild-type mice challenged with bleomycin in both acute and chronic models. Mice with constitutive RGCC gene deletion accumulated more collagen in their lungs in response to chronic bleomycin challenge than did wild-type mice. RNA-Seq analyses of lung fibroblasts revealed that RGCC overexpression alone had a modest transcriptomic effect, but in combination with TGF-β stimulation, induced notable transcriptomic changes that negated the effects of TGF-β, including on extracellular matrix-related genes. At the level of intracellular signaling, RGCC overexpression delayed early TGF-β-induced Smad2/3 phosphorylation, elevated the expression of total and phosphorylated antifibrotic mediator STAT1, and attenuated the expression of a profibrotic mediator STAT3. We conclude that RGCC plays a protective role in pulmonary fibrosis and that its decline permits collagen accumulation. Restoration of RGCC expression may have therapeutic potential in pulmonary fibrosis.

Targeting the Complement Pathway in Malignant Glioma Microenvironments

Malignant glioma is a highly fatal type of brain tumor, and its reoccurrence is largely due to the ordered interactions among the components present in the complex microenvironment. Besides its role in immune surveillance and clearance under physiological conditions, the complement system is expressed in a variety of tumor types and mediates the interactions within the tumor microenvironments. Recent studies have uncovered the broad expression spectrum of complement signaling molecules in the tumor microenvironment and various tumor cells, in particular, malignant glioma cells. Involvement of the complement system in tumor growth, immunosuppression and phenotype transition have also been elucidated. In this review, we enumerate the expression and function of complement molecules in multiple tumor types reported. Moreover, we elaborate the complement pathways in glioma cells and various components of malignant glioma microenvironments. Finally, we summarize the possibility of the complement molecules as prognostic factors and therapeutic targets in the treatment of malignant glioma. Specific targeting of the complement system maybe of great significance and value in the future treatment of multi-type tumors including malignant glioma.

Response gene to complement-32 promotes cell survival via the NF-κB pathway in non-small-cell lung cancer

Response gene to complement (RGC)-32 regulates the cell cycle in response to complement activation. The present study demonstrated that the expression level of RGC-32 is higher in human non-small-cell lung cancer (NSCLC) tissues compared with health controls. Overexpressing RGC-32 induced p65 nucleus translocation, significantly increased nuclear p65 levels and promoted the proliferation of A549 cells. Knockdown of RGC-32 by short hairpin RNA decreased the expression level of nuclear p65 and inhibited cell proliferation. The increase in cell proliferation induced by RGC32 could be abolished by the NF-κB inhibitor pyrrolidine dithiocarbamate. Mechanistic studies indicated that RGC32 mediated NF-κB downstream genes, including vascular cell adhesion protein 1, interleukin-6, cyclin dependent kinase inhibitor 2C, testin and vascular endothelial growth factor A. In summary, the present study demonstrated a novel role of RGC-32 in the progression of NSCLC via the NF-κB pathway and p65. Therefore, RGC-32 could be a potential therapeutic target for NSCLC.

Role of C5b-9 and RGC-32 in Cancer

The complement system represents an effective arsenal of innate immunity as well as an interface between innate and adaptive immunity. Activation of the complement system culminates with the assembly of the C5b-9 terminal complement complex on cell membranes, inducing target cell lysis. Translation of this sequence of events into a malignant setting has traditionally afforded C5b-9 a strict antitumoral role, in synergy with antibody-dependent tumor cytolysis. However, in recent decades, a plethora of evidence has revised this view, highlighting the tumor-promoting properties of C5b-9. Sublytic C5b-9 induces cell cycle progression by activating signal transduction pathways (e.g., Gi protein/ phosphatidylinositol 3-kinase (PI3K)/Akt kinase and Ras/Raf1/ERK1) and modulating the activation of cancer-related transcription factors, while shielding malignant cells from apoptosis. C5b-9 also induces Response Gene to Complement (RGC)-32, a gene that contributes to cell cycle regulation by activating the Akt and CDC2 kinases. RGC-32 is expressed by tumor cells and plays a dual role in cancer, functioning as either a tumor promoter by endorsing malignancy initiation, progression, invasion, metastasis, and angiogenesis, or as a tumor suppressor. In this review, we present recent data describing the versatile, multifaceted roles of C5b-9 and its effector, RGC-32, in cancer.

Loss of Response Gene to Complement 32 (RGC-32) in Diabetic Mouse Retina Is Involved in Retinopathy Development

Diabetic retinopathy (DR) is a severe and recurrent microvascular complication in diabetes. The multifunctional response gene to complement 32 (RGC-32) is involved in the regulation of cell cycle, proliferation, and apoptosis. To investigate the role of RGC-32 in the development of DR, we used human retinal microvascular endothelial cells under high-glucose conditions and type 2 diabetes (T2D) mice (+Lepr^db/ + Lepr^db, db/db). The results showed that RGC-32 expression increased moderately in human retinal endothelial cells under hyperglycemic conditions. Histopathology and RGC-32 expression showed no significant changes between T2D and control mice retina at 16 and 24 weeks of age. However, RGC-32 expression was significantly decreased in T2D mouse retina compared to the control group at 32 weeks of age, which develop features of the early clinical stages of DR, namely reduced retinal thickness and increased ganglion cell death. Moreover, immunohistochemistry showed that RGC-32 was predominantly expressed in the photoreceptor inner segments of control mice, while the expression was dramatically lowered in the T2D retinas. Furthermore, we found that the level of anti-apoptotic protein Bcl-2 was decreased (approximately 2-fold) with a concomitant increase in cleaved caspase-3 (approximately 3-fold) in T2D retina compared to control. In summary, RGC-32 may lose its expression in T2D retina with features of DR, suggesting that it plays a critical role in DR pathogenesis.

RGC-32 (Response Gene to Complement 32) Deficiency Protects Endothelial Cells From Inflammation and Attenuates Atherosclerosis

OBJECTIVE

The objective of this study is to determine the role and underlying mechanisms of RGC-32 (response gene to complement 32 protein) in atherogenesis.

APPROACH AND RESULTS

RGC-32 was mainly expressed in endothelial cells of atherosclerotic lesions in both ApoE^-/- (apolipoprotein E deficient) mice and human patients. Rgc-32 deficiency (Rgc32^-/-) attenuated the high-fat diet-induced and spontaneously developed atherosclerotic lesions in ApoE^-/- mice without affecting serum cholesterol concentration. Rgc32^-/- seemed to decrease the macrophage content without altering collagen and smooth muscle contents or lesional macrophage proliferation in the lesions. Transplantation of WT (wild type) mouse bone marrow to lethally irradiated Rgc32^-/- mice did not alter Rgc32^-/--caused reduction of lesion formation and macrophage accumulation, suggesting that RGC-32 in resident vascular cells, but not the macrophages, plays a critical role in the atherogenesis. Of importance, Rgc32^-/- decreased the expression of ICAM-1 (intercellular adhesion molecule-1) and VCAM-1 (vascular cell adhesion molecule-1) in endothelial cells both in vivo and in vitro, resulting in a decrease in TNF-α (tumor necrosis factor-α)-induced monocyte-endothelial cell interaction. Mechanistically, RGC-32 mediated the ICAM-1 and VCAM-1 expression, at least partially, through NF (nuclear factor)-κB signaling pathway. RGC-32 directly interacted with NF-κB and facilitated its nuclear translocation and enhanced TNF-α-induced NF-κB binding to ICAM-1 and VCAM-1 promoters.

CONCLUSIONS

RGC-32 mediates atherogenesis by facilitating monocyte-endothelial cell interaction via the induction of endothelial ICAM-1 and VCAM-1 expression, at least partially, through NF-κB signaling pathway.

Correlation between the methylation of the FUT1 promoter region and FUT1 expression in the duodenum of piglets from newborn to weaning

Alpha-(1,2)-fucosyltransferase (FUT1) gene has some influence on economically important traits and disease resistance. DNA methylation plays an important role in human diseases but is relatively poorly studied in pigs by regulating the mRNA expression of genes. The aim of this study was to analyze the influence of promoter methylation on the expression of FUT1 gene. We used bisulfite sequencing PCR (BSP) and qPCR to analyze the methylation of the FUT1 5'-flanking region and FUT1 mRNA expression in the duodenum of Sutai piglets from newborn to weaning. FUT1 contains three CpG islands upstream of the start codon, of which two are located in the putative promoter region containing multiple promoter elements and transcription factor binding sites, such as CpG islands, a CAAT box, SP1, and EARLY-SEQ 1. The CpG island between nucleotides -1762 and -580 had a low degree of methylation, and its methylation level was significantly lower in 35-day-old piglets than 8- and 18-day-old piglets (P < 0.05). FUT1 mRNA expression was significantly higher in 35-day-old piglets than 8- and 18-day-old piglets (P < 0.05). Pearson's correlation analysis showed that the methylation of the CpG island between nucleotides -1762 and -580 of FUT1 was significantly, negatively correlated with FUT1 mRNA expression (P < 0.05). These results demonstrate that differential methylation of CpG islands negatively regulates the expression of FUT1 in the porcine duodenum, suggesting a probable influence on the resistance of piglets to infection with ETEC F18.

RGC32 induces epithelial-mesenchymal transition by activating the Smad/Sip1 signaling pathway in CRC

Response gene to complement 32 (RGC32) is a transcription factor that regulates the expression of multiple genes involved in cell growth, viability and tissue-specific differentiation. However, the role of RGC32 in tumorigenesis and tumor progression in colorectal cancer (CRC) has not been fully elucidated. Here, we showed that the expression of RGC32 was significantly up-regulated in human CRC tissues versus adjacent normal tissues. RGC32 expression was significantly correlated with invasive and aggressive characteristics of tumor cells, as well as poor survival of CRC patients. We also demonstrated that RGC32 overexpression promoted proliferation, migration and tumorigenic growth of human CRC cells in vitro and in vivo. Functionally, RGC32 facilitated epithelial-mesenchymal transition (EMT) in CRC via the Smad/Sip1 signaling pathway, as shown by decreasing E-cadherin expression and increasing vimentin expression. In conclusion, our findings suggested that overexpression of RGC32 facilitates EMT of CRC cells by activating Smad/Sip1 signaling.

Promoter Methylation and mRNA Expression of Response Gene to Complement 32 in Breast Carcinoma

Background. Response gene to complement 32 (RGC32), induced by activation of complements, has been characterized as a cell cycle regulator; however, its role in carcinogenesis is still controversial. In the present study we compared RGC32 promoter methylation patterns and mRNA expression in breast cancerous tissues and adjacent normal tissues. Materials and Methods. Sixty-three breast cancer tissues and 63 adjacent nonneoplastic tissues were included in our study. Design. Nested methylation-specific polymerase chain reaction (Nested-MSP) and quantitative PCR (qPCR) were used to determine RGC32 promoter methylation status and its mRNA expression levels, respectively. Results. RGC32 methylation pattern was not different between breast cancerous tissue and adjacent nonneoplastic tissue (OR = 2.30, 95% CI = 0.95–5.54). However, qPCR analysis displayed higher levels of RGC32 mRNA in breast cancerous tissues than in noncancerous tissues (1.073 versus 0.959; P = 0.001), irrespective of the promoter methylation status. The expression levels and promoter methylation of RGC32 were not correlated with any of patients' clinical characteristics (P > 0.05). Conclusion. Our findings confirmed upregulation of RGC32 in breast cancerous tumors, but it was not associated with promoter methylation patterns.

RGC-32 Deficiency Protects against Hepatic Steatosis by Reducing Lipogenesis

Hepatic steatosis is associated with insulin resistance and metabolic syndrome because of increased hepatic triglyceride content. We have reported previously that deficiency of response gene to complement 32 (RGC-32) prevents high-fat diet (HFD)-induced obesity and insulin resistance in mice. This study was conducted to determine the role of RGC-32 in the regulation of hepatic steatosis. We observed that hepatic RGC-32 was induced dramatically by both HFD challenge and ethanol administration. RGC-32 knockout (RGC32(-/-)) mice were resistant to HFD- and ethanol-induced hepatic steatosis. The hepatic triglyceride content of RGC32(-/-) mice was decreased significantly compared with WT controls even under normal chow conditions. Moreover, RGC-32 deficiency decreased the expression of lipogenesis-related genes, sterol regulatory element binding protein 1c (SREBP-1c), fatty acid synthase, and stearoyl-CoA desaturase 1 (SCD1). RGC-32 deficiency also decreased SCD1 activity, as indicated by decreased desaturase indices of the liver and serum. Mechanistically, insulin and ethanol induced RGC-32 expression through the NF-κB signaling pathway, which, in turn, increased SCD1 expression in a SREBP-1c-dependent manner. RGC-32 also promoted SREBP-1c expression through activating liver X receptor. These results demonstrate that RGC-32 contributes to the development of hepatic steatosis by facilitating de novo lipogenesis through activating liver X receptor, leading to the induction of SREBP-1c and its target genes. Therefore, RGC-32 may be a potential novel drug target for the treatment of hepatic steatosis and its related diseases.

RGC32 deficiency protects against high-fat diet-induced obesity and insulin resistance in mice

Obesity is an important independent risk factor for type 2 diabetes, cardiovascular diseases and many other chronic diseases. Adipose tissue inflammation is a critical link between obesity and insulin resistance and type 2 diabetes and a contributor to disease susceptibility and progression. The objective of this study was to determine the role of response gene to complement 32 (RGC32) in the development of obesity and insulin resistance. WT and RGC32 knockout (Rgc32(-/-) (Rgcc)) mice were fed normal chow or high-fat diet (HFD) for 12 weeks. Metabolic, biochemical, and histologic analyses were performed. 3T3-L1 preadipocytes were used to study the role of RGC32 in adipocytes in vitro. Rgc32(-/-) mice fed with HFD exhibited a lean phenotype with reduced epididymal fat weight compared with WT controls. Blood biochemical analysis and insulin tolerance test showed that RGC32 deficiency improved HFD-induced dyslipidemia and insulin resistance. Although it had no effect on adipocyte differentiation, RGC32 deficiency ameliorated adipose tissue and systemic inflammation. Moreover, Rgc32(-/-) induced browning of adipose tissues and increased energy expenditure. Our data indicated that RGC32 plays an important role in diet-induced obesity and insulin resistance, and thus it may serve as a potential novel drug target for developing therapeutics to treat obesity and metabolic disorders.

DNA methylation biomarkers: cancer and beyond

Biomarkers are naturally-occurring characteristics by which a particular pathological process or disease can be identified or monitored. They can reflect past environmental exposures, predict disease onset or course, or determine a patient's response to therapy. Epigenetic changes are such characteristics, with most epigenetic biomarkers discovered to date based on the epigenetic mark of DNA methylation. Many tissue types are suitable for the discovery of DNA methylation biomarkers including cell-based samples such as blood and tumor material and cell-free DNA samples such as plasma. DNA methylation biomarkers with diagnostic, prognostic and predictive power are already in clinical trials or in a clinical setting for cancer. Outside cancer, strong evidence that complex disease originates in early life is opening up exciting new avenues for the detection of DNA methylation biomarkers for adverse early life environment and for estimation of future disease risk. However, there are a number of limitations to overcome before such biomarkers reach the clinic. Nevertheless, DNA methylation biomarkers have great potential to contribute to personalized medicine throughout life. We review the current state of play for DNA methylation biomarkers, discuss the barriers that must be crossed on the way to implementation in a clinical setting, and predict their future use for human disease.

Role of C5b-9 complement complex and response gene to complement-32 (RGC-32) in cancer

Complement system activation plays an important role in both innate and acquired immunity, with the activation of complement and the subsequent formation of C5b-9 terminal complement complex on cell membranes inducing target cell death. Recognition of this role for C5b-9 leads to the assumption that C5b-9 might play an antitumor role. However, sublytic C5b-9 induces cell cycle progression by activating signal transduction pathways and transcription factors in cancer cells, indicating a role in tumor promotion for this complement complex. The induction of the cell cycle by C5b-9 is dependent upon the activation of the phosphatidylinositol 3-kinase (PI3K)/Akt/FOXO1 and ERK1 pathways in a Gi protein-dependent manner. C5b-9 also induces response gene to complement (RGC)-32, a gene that plays a role in cell cycle promotion through activation of Akt and the CDC2 kinase. RGC-32 is expressed by tumor cells and plays a dual role in cancers, in that it has both a tumor suppressor role and tumor-promoting activity. Thus, through the activation of tumor cells, the C5b-9-mediated induction of the cell cycle plays an important role in tumor proliferation and oncogenesis.

Overexpression of response gene to complement 32 (RGC32) promotes cell invasion and induces epithelial-mesenchymal transition in lung cancer cells via the NF-κB signaling pathway

Response gene to complement 32 (RGC32) is a novel cellular protein that has been reported to be expressed aberrantly in multiple types of human tumors. However, the role of RGC32 in cancer is still controversial, and the molecular mechanisms by which RGC32 contributes to the development of cancer remain largely unknown. In the present study, we constructed a recombinant expression vector pCDNA3.1-RGC32 and transfected it into human lung cancer A549 cells. Stable transformanted cells were identified by real-time PCR and Western blot analysis. Functional analysis showed that forced overexpression of RGC32 increased invasive and migration capacities of lung cancer cells in vitro, and induced the acquisition of epithelial-mesenchymal transition (EMT) phenotype, as demonstrated by the spindle-like morphology, downregulation of E-cadherin, and upregulation of Vimentin, Fibronectin, Snail and Slug. Also, overexpression of RGC32 increased expression and activities of matrix metalloproteinase (MMP)-2 and MMP-9 in A549 cells. Furthermore, the downregulation of E-cadherin induced by RGC32 was remarkably attenuated by nuclear factor-κB (NF-κB) inhibitor BAY 11-7028 and small interfering RNA targeting NF-κB p65, suggesting a role of the NF-κB signaling pathway in RGC32-induced EMT. Taken together, our data suggest that RGC32 promotes cell migration and invasion and induces EMT in lung cancer cells via the NF-κB signaling pathway.

Upregulation of the cell-cycle regulator RGC-32 in Epstein-Barr virus-immortalized cells

Epstein-Barr virus (EBV) is implicated in the pathogenesis of multiple human tumours of lymphoid and epithelial origin. The virus infects and immortalizes B cells establishing a persistent latent infection characterized by varying patterns of EBV latent gene expression (latency 0, I, II and III). The CDK1 activator, Response Gene to Complement-32 (RGC-32, C13ORF15), is overexpressed in colon, breast and ovarian cancer tissues and we have detected selective high-level RGC-32 protein expression in EBV-immortalized latency III cells. Significantly, we show that overexpression of RGC-32 in B cells is sufficient to disrupt G2 cell-cycle arrest consistent with activation of CDK1, implicating RGC-32 in the EBV transformation process. Surprisingly, RGC-32 mRNA is expressed at high levels in latency I Burkitt's lymphoma (BL) cells and in some EBV-negative BL cell-lines, although RGC-32 protein expression is not detectable. We show that RGC-32 mRNA expression is elevated in latency I cells due to transcriptional activation by high levels of the differentially expressed RUNX1c transcription factor. We found that proteosomal degradation or blocked cytoplasmic export of the RGC-32 message were not responsible for the lack of RGC-32 protein expression in latency I cells. Significantly, analysis of the ribosomal association of the RGC-32 mRNA in latency I and latency III cells revealed that RGC-32 transcripts were associated with multiple ribosomes in both cell-types implicating post-initiation translational repression mechanisms in the block to RGC-32 protein production in latency I cells. In summary, our results are the first to demonstrate RGC-32 protein upregulation in cells transformed by a human tumour virus and to identify post-initiation translational mechanisms as an expression control point for this key cell-cycle regulator.