Silica's Silent Threat: Contributing to Skin Fibrosis in Systemic Sclerosis by Targeting the HDAC4/Smad2/3 Pathway.

Nowadays, silica products are widely used in daily life, especially in skin applications, which inevitably increases the risk of silica exposure in general population. However, inadequate awareness of silica's potential hazards and lack of self-protection are of concern. Systemic sclerosis (SSc) is characterized by progressive tissue fibrosis under environmental and genetic interactions. Silica exposure is considered an important causative factor for SSc, but its pathogenesis remains unclear. Within this study, we showed that lower doses of silica significantly promoted the proliferation, migration, and activation of human skin fibroblasts (HSFs) within 24 hours. Silica injected subcutaneously into mice induced and exacerbated skin fibrosis. Notably, silica increased histone deacetylase-4 (HDAC4) expression by inducing its DNA hypomethylation in normal HSFs. The elevated HDAC4 expression was also confirmed in SSc HSFs. Furthermore, HDAC4 was positively correlated with Smad2/3 phosphorylation and COL1, α-SMA, and CTGF expression. The HDAC4 inhibitor LMK235 mitigated silica-induced upregulation of these factors and alleviated skin fibrosis in SSc mice. Taken together, silica induces and exacerbates skin fibrosis in SSc patients by targeting the HDAC4/Smad2/3 pathway. Our findings provide new insights for evaluating the health hazards of silica exposure and identify HDAC4 as a potential interventional target for silica-induced SSc skin fibrosis.

Sirtuin 1 overexpression contributes to the expansion of follicular helper T cells in Systemic lupus erythematosus and serves as an easy-to-intervene therapeutic target.

OBJECTIVE: SIRT1, an NAD+-dependent deacetylase, is up-regulated in CD4+ T cells from SLE patients and MRL/lpr lupus-like mice. This study aimed to explore the role of SIRT1 in Tfh cell expansion and its potential value as a therapeutic target for SLE. METHODS: Frequencies of CD4+CXCR5+PD-1+ Tfh cells in peripheral blood from SLE patients and their expression of SIRT1 and BCL-6 were determined with flow cytometry. Naïve CD4+ T cells were transfected with SIRT1-expressing lentivirus and small interfering RNA (siRNA) targeting SIRT1, respectively, and then cultured in a Tfh-polarizing condition to study the impact of SIRT1 on Tfh cell differentiation. This impact was also evaluated in both CD4+ T cells and naïve CD4+ T cells by treatment with SIRT1 inhibitors (EX527 and nicotinamide) in vitro. MRL/lpr mice and pristane-induced lupus mice were treated with continuous daily intake of nicotinamide, and their lupus phenotypes including skin rash, arthritis, proteinuria and serum anti-dsDNA autoantibodies were compared with controls. RESULTS: Expression of SIRT1 was elevated in Tfh cells from SLE patients and positively correlated with Tfh cell frequencies. SIRT1 expression gradually increased during Tfh cell differentiation. Overexpression of SIRT1 by lentiviral vectors significantly promoted Tfh cell differentiation/proliferation. Reciprocally, suppressing expression of SIRT1 by siRNA and inhibiting SIRT1 activity by EX-527 or nicotinamide hindered Tfh cell expansion. Continuous daily intake of nicotinamide alleviated lupus-like phenotypes and decreased serum CXCL13 in the two mouse models. CONCLUSION: SIRT1 overexpression contributes to the expansion of Tfh cells in SLE and may serve as a potential target for treatment.

ATRA ameliorates fibrosis by suppressing the pro-fibrotic molecule Fra2/AP-1 in systemic sclerosis.

Systemic sclerosis (SSc) is an autoimmune connective tissue disease that leads to irreversible fibrosis of the skin and the internal organs. The etiology of SSc is complex, its pathophysiology is poorly understood, and clinical therapeutic options are restricted. Thus, research into medications and targets for treating fibrosis is essential and urgent. Fos-related antigen 2 (Fra2) is a transcription factor that is a member of the activator protein-1 family. Fra2 transgenic mice were shown to have spontaneous fibrosis. All-trans retinoic acid (ATRA) is a vitamin A intermediate metabolite and ligand for the retinoic acid receptor (RAR), which possesses anti-inflammatory and anti-proliferative properties. Recent research has demonstrated that ATRA also has an anti-fibrotic effect. However, the exact mechanism is not fully understood. Interestingly, we identified potential binding sites for the transcription factor RARα to the promoter region of the FRA2 gene through JASPAR and PROMO databases. In this study, the pro-fibrotic effect of Fra2 in SSc is confirmed. SSc dermal fibroblasts and bleomycin-induced fibrotic tissues of SSc animals exhibit increased levels of Fra2. Inhibition of Fra2 expression in SSc dermal fibroblasts with Fra2 siRNA markedly decreased collagen I expression. ATRA reduced the expressions of Fra2, collagen I, and α-smooth muscle actin(α-SMA) in SSc dermal fibroblasts and bleomycin-induced fibrotic tissues of SSc mice. In addition, chromatin immunoprecipitation and dual-luciferase assays demonstrated that retinoic acid receptor RARα binds to the FRA2 promoter and modulates its transcriptional activity. ATRA decreases collagen I expression both in vivo and in vitro via the reduction of Fra2 expression. This work establishes the rationale for expanding the use of ATRA in the treatment of SSc and indicates that Fra2 can be used as an anti-fibrotic target.

Activating Protein-1 (AP-1): A Promising Target for the Treatment of Fibrotic Diseases.

The fibrosis of tissues and organs occurs via an aberrant tissue remodeling process characterized by an excessive deposition of extracellular matrix, which can lead to organ dysfunction, organ failure, and death. Because the pathogenesis of fibrosis remains unclear and elusive, there is currently no medication to reverse it; hence, this process deserves further study. Activating protein-1 (AP-1)-comprising Jun (c-Jun, JunB, JunD), Fos (c-fos, FosB, Fra1, and Fra2), and activating transcription factor-is a versatile dimeric transcription factor. Numerous studies have demonstrated that AP-1 plays a crucial role in advancing tissue and organ fibrosis via induction of the expression of fibrotic molecules and activating fibroblasts. This review focuses on the role of AP-1 in a range of fibrotic disorders as well as on the antifibrotic effects of AP-1 inhibitors. It also discusses the potential of AP-1 as a new therapeutic target in conditions involving tissue and organ fibrosis.

UVA1 irradiation attenuates collagen production via Ficz/AhR/MAPK signaling activation in scleroderma.

Scleroderma is an autoimmune disease mainly characterized by progressive fibrosis of the skin. There are two types of scleroderma, namely localized scleroderma (LS) and systemic sclerosis (SSc); skin lesions in both types of scleroderma are histologically identical. Progressive skin sclerosis induces psychological and ecological burden for scleroderma patients. However, there is no effective treatment for scleroderma due to its unclear etiology. Aryl hydrocarbon receptor (AhR) is recognized as an environmental chemical effector that can respond to ultraviolet radiation, which has been demonstrated to participate in the pathogenesis of SSc in our previous study. In this study, we verify whether the anti-fibrosis effect of ultraviolet A1 (UVA1) phototherapy could be partially induced through Ficz/AhR/MAPK signaling activation for fibrotic lesions in both SSc and LS patients. This is the first study to show the association between the AhR pathway and the anti-fibrotic mechanism of UVA1 phototherapy, which provides additional evidence of the role of AhR in the fibrotic mechanism of systemic scleroderma from different perspectives. Ficz and other AhR agonists may replace UVA1 phototherapy as anti-fibrotic agents in scleroderma.

Overexpressed perforin contributes to the melanocyte destruction via epigenetic regulation in patients with vitiligo.

BACKGROUND: Perforin (PRF), a pivotal cytotoxic effector molecule of activated CD8+ T cells, has a crucial role in the pathogenesis of vitiligo. However, the mechanisms leading to the abnormal perforin expression remain poorly understood in the CD8+ T cells of vitiligo patients. OBJECTIVE: To investigate the contributions of DNA methylation to the abnormal expression of perforin in CD8+ T cells of vitiligo patients. METHODS: Skin samples and CD8+ T cells from peripheral blood were collected to detect the expression levels of perforin in vitiligo patients. The methylation status of the perforin promoter was investigated by bisulfite sequencing. The apoptosis of melanocytes co-cultured with CD8+ T cells was evaluated to determinate the cytotoxic role of perforin. RESULTS: Increased CD8+ and perforin+ cells were found in lesion of vitiligo patients. The expression levels of perforin were elevated in the CD8+ T cells from peripheral blood of vitiligo patients and their culture supernatants. The perforin promoter was hypomethylated in vitiligo CD8+ T cells. Treatment of normal CD8+ T cells with the DNA methylation inhibitor 5-Azacytidine (5-Azac) reduced the perforin methylation level and caused perforin overexpression. The methylation levels of perforin were inversely correlated with its mRNA expression in CD8+ T cells. The apoptosis rates of the melanocytes co-cultured with vitiligo- and 5-Azac-treated-normal CD8+ T cells were significantly increased compared with normal-untreated CD8+ T cells. And the apoptosis rates of melanocytes co-cultured with si-PRF-treated-vitiligo CD8+ T cells were significantly decreased compared with vitiligo-untreated CD8+ T cells. CONCLUSION: Hypomethylation of the perforin promoter contributes to its overexpression in CD8+ T cells from vitiligo patients, which then mediates the melanocyte destruction in vitiligo.

Bullous lichen sclerosus-generalized morphea overlap syndrome improved by tofacitinib.

We here report a case of a middle-aged man with an unusual case of bullous lichen sclerosus complicated with generalized morphea. He showed initial recurrent flaccid bullae, followed by ivory-white sclerotic plaques and extensive skin sclerosis, with additional walking disorder caused by knee-joint contracture, and ulcers on the lower extremities and back. The patient had no visceral involvement. After oral hydroxychloroquine and oral corticosteroids failed, the patient was given tofacitinib, which resolved his ulcers after 4 weeks and ameliorated his knee-joint contracture and skin sclerosis within 4 months. Owing to the occurrence of diffuse large B-cell lymphoma, he stopped using tofacitinib, and the ulcer and walking disorder reappeared. This is rare case of bullous lichen sclerosus-generalized morphea overlap syndrome. The patient recovered well after treatment with tofacitinib. His symptoms recurred after discontinuation of tofacitinib.

Overexpression of OASL upregulates TET1 to induce aberrant activation of CD4+ T cells in systemic sclerosis via IRF1 signaling.

BACKGROUND: Systemic sclerosis (SSc), an autoimmune disease with unknown etiology and pathogenesis, is characterized by abnormal autoimmunity, vascular dysfunction, and progressive fibrosis of skin and organs. Studies have shown that a key factor in the pathogenesis of SSc is aberrant activation of CD4+ T cells. Our previous studies have shown that a global hypomethylation state of CD4+ T cells is closely related to aberrant activation. However, the exact mechanism of hypomethylation in CD4+T cells is not yet clear. METHODS: Illumina HiSeq 2500 Platform was used to screen differentially expressed genes and explore the role of OASL, TET1, and IRF1 in the abnormal activation of CD4+T cells in SSc. Finally, double luciferase reporter gene experiments were used to analyze the interaction between IRF1 and TET1. RESULTS: OASL overexpression could upregulate TET1 to increase the hydroxymethylation levels of CD4+ T cells and induce high expression of functional proteins (CD40L and CD70), thus promoting CD4+T cell aberrant activation. Moreover, OASL upregulated TET1 via IRF1 signaling activation, and a double luciferase reporter gene experiment revealed that IRF1 can bind to the TET1 promoter region to regulate its expression. CONCLUSIONS: OASL participates in the regulation of abnormal hypomethylation of CD4+ T cells in SSc, which implies a pivotal role for IFN signaling in the pathogenesis of SSc. Regulating DNA methylation and IFN signaling may serve as therapeutic treatments in SSc.

Esomeprazole alleviates fibrosis in systemic sclerosis by modulating AhR/Smad2/3 signaling.

Systemic sclerosis (SSc) is a connective tissue disease with the involvement of complex signaling pathways, such as TGF-ß/Smad2/3. SSc can lead to severe multiple organ fibrosis, but no effective therapy is currently available because of its unclear pathogenesis. Exploring new treatments is the focus of recent research on SSc. Recent studies have implied a potential antifibrotic role of esomeprazole (ESO), but with currently unidentified mechanisms. Signaling of AhR, a ligand-dependent transcription factor, has been described as a key controller of fibrosis, tumorigenesis, and immune balance. Recently, it has been reported that ESO may be an exogenous agonist of AhR signaling, while no previous study has revealed the effects of ESO on SSc and its underlying mechanisms. In this study, we demonstrate that ESO suppresses the migration of SSc dermal fibroblasts, downregulates profibrotic markers, including COLIA1, α-SMA CTGF and MMP1, and limits collagen production potentially via the activation of AhR signaling. More importantly, ESO could block Smad2/3 phosphorylation concurrently with the reduction in collagen via AhR signaling. Moreover, our results from the bleomycin (BLM)-induced SSc model in skin and lung shows that ESO ameliorates fibrosis in vivo, which in keeping with our in vitro results. We conclude that ESO is a potential therapeutic drug for SSc fibrosis.

Characterizing DNA methylation signatures and their potential functional roles in Merkel cell carcinoma.

BACKGROUND: Merkel cell carcinoma (MCC) is a rare but aggressive skin cancer with limited treatment possibilities. Merkel cell tumors display with neuroendocrine features and Merkel cell polyomavirus (MCPyV) infection in the majority (80%) of patients. Although loss of histone H3 lysine 27 trimethylation (H3K27me3) has been shown during MCC tumorigenesis, epigenetic dysregulation has largely been overlooked. METHODS: We conducted global DNA methylation profiling of clinically annotated MCC primary tumors, metastatic skin tumors, metastatic lymph node tumors, paired normal tissues, and two human MCC cell lines using the Illumina Infinium EPIC DNA methylation BeadArray platform. RESULTS: Significant differential DNA methylation patterns across the genome are revealed between the four tissue types, as well as based on MCPyV status. Furthermore, 964 genes directly regulated by promoter or gene body DNA methylation were identified with high enrichment in neuro-related pathways. Finally, our findings suggest that loss of H3K27me3 occupancy in MCC is attributed to KDM6B and EZHIP overexpression as a consequence of promoter DNA hypomethylation. CONCLUSIONS: We have demonstrated specific DNA methylation patterns for primary MCC tumors, metastatic MCCs, and adjacent-normal tissues. We have also identified DNA methylation markers that not only show potential diagnostic or prognostic utility in MCC management, but also correlate with MCC tumorigenesis, MCPyV expression, neuroendocrine features, and H3K27me3 status. The identification of DNA methylation alterations in MCC supports the need for further studies to understand the clinical implications of epigenetic dysregulation and potential therapeutic targets in MCC.

High expression of VTRNA2-1 in systemic lupus erythematosus patients' B lymphocytes and its significance. / VTRNA2-1åœ¨ç³»ç»Ÿæ€§çº¢æ–‘ç‹¼ç–®æ‚£è€ Bç»†èƒžä¸­çš„é«˜è¡¨è¾¾åŠå ¶æ„ä¹‰.

OBJECTIVES: To investigate the expression of vault ribonucleic acid 2-1 (VTRNA2-1) in T or B lymphocytes in patients with systemic lupus erythematosus (SLE) from the perspective of epigenetic non-coding RNA, and to explore the preliminary pathogenesis of SLE. METHODS: CD4+ T lymphocytes from peripheral blood in 25 healthy controls and 32 SLE patients, CD19+ B lymphocytes from peripheral blood in 62 SLE patients (47 patients were active SLE and 15 patients were inactive) and 29 healthy controls were collected, and the expression levels of VTRNA2-1 were detected by real-time PCR. Co-immunoprecipitation assay was used to explore the direct-acting proteins of VTRNA2-1. RESULTS: Through the detection of VTRNA2-1 in peripheral blood T cells and B cells in the SLE patients and healthy controls, we have found that there was no significant difference in the expression of VTRNA2-1 in T cells between the SLE patients and the healthy controls (P>0.05). The expression of VTRNA2-1 in B cells in the active and inactive SLE patients was both higher than that in the healthy controls, with significant difference (P<0.01 and P<0.05, respectively). Co-immunoprecipitation assay confirmed that VTRNA2-1 exerted its biological function via specific binding with protein kinase R (PKR). CONCLUSIONS: VTRNA2-1 is highly expressed in B cells in the SLE patients, which may play a biological role by regulating PKR.

[Clinical analysis for 108 cases of dermatomyositis].

OBJECTIVE: To investigate the clinical characteristics of dermatomyositis, to investigate the types and clinical features of dermatomyositis complicated with malignant tumor, and to provide evidence for clinical diagnosis, treatment and prognostic evaluation.
 Methods: The clinical manifestations and laboratory test results for 108 cases of dermatomyositis with complications in the Second Xiangya Hospital of Central South University were analyzed.
 Results: Patients aged from 14 to 60 years accounted for 62.96%. The first symptom was single skin rash (54.63%), and the most characteristic cutaneous features were asymmetrical proximal myositis with various degrees (97.22%). The visceral involvement was as follows: the digestive tract (31.48%), the heart (19.44%), the lung (26.85%), and the thyroid damage (12.96%). Twelve (11.11%) patients were combined with malignant tumor. The positive rates for albumin (ALB), glutamic oxalacetic transaminase (AST), glutamic-pyruvic transaminase (ALT), lactate dehydrogenase (LDH), creatine kinase (CK), creatine kinase isoenzyme (CK-MB), erythrocyte sedimentation rate (ESR), anti Jo-1 antibody, anti ribonucleoprotein (RNP) antibody, and anti-topoisomerasel (Scl) antibody were 25.93%, 46.30%, 28.70%, 87.04%%, 51.85%, 26.85%, 55.56%, 2.27%, 8.99%, and 2.27%, respectively. The patients were divided into a tumor group and a non-tumor group. The chi-square test results from clinical symptoms and laboratory tests suggested that increase of ESR was a risk factor for dermatomyositis combining tumor. The main strategy of therapy was corticosteroids.
 Conclusion: Dermatomyositis possesses typical skin lesions and dermatitis is the most common initial symptom of dermatomyositis. In clinic, diagnosis of dermatomyositis should be timely combined with muscle enzymes test, electromyography and muscle biopsy. Dermatomyositis can easily involve many organs. Thus relevant examinations (such as chest X-ray and CT) should be done preventively. Rapid ESR is a risk factor for dermatomyositis complicated with malignant tumor and it can be used as an index to guide clinical diagnosis.

The role of microRNA-1246 in the regulation of B cell activation and the pathogenesis of systemic lupus erythematosus.

BACKGROUND: The pathogenesis of systemic lupus erythematosus (SLE) has not yet been completely elucidated. One of the hallmarks of SLE is the production of autoantibodies by uncontrolled over-activated B cells. Early B cell factor 1 (EBF1) contributes to the development, activation, and proliferation of B cells through activation of the AKT signaling pathway. Accumulating evidence has demonstrated that several microRNAs (miRNAs) contribute to the pathogenesis of autoimmune diseases through the regulation of B cells in SLE. We aim to investigate the expression patterns of miR-1246 in B cells and its contribution to pathogenesis of SLE. RESULTS: Our results showed that the expression of miR-1246 was significantly decreased in B cells from SLE patients. We verified that miR-1246 specifically targeted the EBF1 messenger RNA (mRNA) by interacting with its 3'-untranslated region (3'-UTR) and regulated the expression of EBF1. Transfection of miR-1246 inhibitors into healthy B cells upregulated the expression of EBF1, enhanced B cell function, and increased the production of B cell surface co-stimulatory molecules CD40, CD80, and CD86. We also observed that abnormal activation of the AKT signaling pathway was associated with decreased P53 expression, leading to the downregulation of the miR-1246 expression; and upregulation of the miR-1246 expression reversed the responsiveness of B cells by inhibiting EBF1 expression. CONCLUSIONS: Activated B cells in lupus could decrease the expression of miR-1246 through the AKT-P53 signaling pathway, which in turn enhances the expression of EBF1, thereby promoting further activation of B cells. Conversely, upregulation of miR-1246 could interrupt this amplification pathway. Our findings thus provide a theoretical framework towards the research of novel biological targets in SLE treatment.

Acquired hemophilia associated with bullous pemphigoid: a case report.

The development of factor VIII inhibitors in non-hemophilic patients is rare and may occur in healthy individuals, mostly elderly and women in postpartum period, and in patients with malignant neoplasia or autoimmune diseases, such as bullous pemphigoid. We described the case of a 60-year-old female patient who developed bullous pemphigoid for 3 month and presented with bleeding tendency and hematoma in the tongue. Therapy with methylprednisolone, cyclophosphamide, intravenous immunoglobulin and factor VIII reposition was instituted, resulting in a remission of the bleeding and negativity for antibodies against factor VIII titers. We concluded that, despite its rarity, the presence of acquired factor VIII inhibitors should be investigated when patients with autoimmune diseases develop bleeding manifestations.

Allelic methylation levels of the noncoding VTRNA2-1 located on chromosome 5q31.1 predict outcome in AML.

Deletions of chromosome 5q are associated with poor outcomes in acute myeloid leukemia (AML) suggesting the presence of tumor suppressor(s) at the locus. However, definitive identification of putative tumor suppressor genes remains controversial. Here we show that a 106-nucleotide noncoding RNA vault RNA2-1 (vtRNA2-1), previously misannotated as miR886, could potentially play a role in the biology and prognosis of AML. vtRNA2-1 is transcribed by polymerase III and is monoallelically methylated in 75% of healthy individuals whereas the remaining 25% of the population have biallelic hypomethylation. AML patients without methylation of VTRNA2-1 have a considerably better outcome than those with monoallelic or biallelic methylation (n = 101, P = .001). We show that methylation is inversely correlated with vtRNA2-1 expression, and that 5-azanucleosides induce vtRNA2-1 and down-regulate the phosphorylated RNA-dependent protein kinase (pPKR), whose activity has been shown to be modulated by vtRNA2-1. Because pPKR promotes cell survival in AML, the data are consistent with vtRNA2-1 being a tumor suppressor in AML. This is the first study to show that vtRNA2-1 might play a significant role in AML, that it is either mono- or biallelically expressed in the blood cells of healthy individuals, and that its methylation state predicts outcome in AML.

Creating a flexible multiple microRNA expression vector by linking precursor microRNAs.

MicroRNAs (miRNAs) are ∼22nt non-coding RNA molecules that usually function as endogenous repressors of target genes. Many biological processes depend on faithful miRNA expression and miRNA profiling has revealed dysregulation of many miRNAs in neurological, and cardiovascular diseases, and in cancer. Despite this finding, most studies have focused on the function of single miRNAs or miRNA clusters. To better address physiologically relevant collaborative miRNA interactions, we developed a simple and flexible platform which expresses several miRNAs that have different genomic locations from a single transcript using endogenous pre-miRNA sequences. As a proof of principle we cloned the miR-34 tumor suppressor family and showed that the miR-34a/34b/34c vector expresses each miRNA at similar levels to individual miRNA containing vectors. Moreover, the miR-34a/34b/34c vector suppressed cell growth more than the individual miRNA vectors. We expect that this platform will be invaluable as a tool to study the complex and synergistic interactions of aberrantly expressed miRNAs in human diseases and may have applications for use in gene therapy.

Equitoxic doses of 5-azacytidine and 5-aza-2'deoxycytidine induce diverse immediate and overlapping heritable changes in the transcriptome.

BACKGROUND: The hypomethylating agent 5-Azacytidine (5-Aza-CR) is the first drug to prolong overall survival in patients with myelodysplastic syndrome (MDS). Surprisingly, the deoxyribonucleoside analog 5-Aza-2'deoxycytidine (5-Aza-CdR) did not have a similar effect on survival in a large clinical trial. Both drugs are thought to exert their effects after incorporation into DNA by covalent binding of DNA methyltransferase (DNMT). While 5-Aza-CdR is incorporated into only DNA, 5-Aza-CR is also incorporated into RNA. Here, we have analyzed whether this difference in nucleic acid incorporation may influence the capacities of these drugs to regulate the expression of mRNA and microRNAs (miRNA), which may potentially affect the activities of the drugs in patients. METHODOLOGY/PRINCIPAL FINDINGS: A hematopoietic (HL-60; acute myeloid leukemia) and a solid (T24; transitional cell carcinoma) cancer cell line were treated with equitoxic doses of 5-Aza-CR and 5-Aza-CdR for 24 hrs, and the immediate (day 2) and lasting (day 8) effects on RNA expression examined. There was considerable overlap between the RNAs heritably upregulated by both drugs on day 8 but more RNAs were stably induced by the deoxy analog. Both drugs strongly induced expression of cancer testis antigens. On day 2 more RNAs were downregulated by 5-Aza-CR, particularly at higher doses. A remarkable downregulation of miRNAs and a significant upregulation of tRNA synthetases and other genes involved in amino acid metabolism was observed in T24 cells. CONCLUSIONS/SIGNIFICANCE: Overall, this suggests that significant differences exist in the immediate action of the two drugs, however the dominant pattern of the lasting, and possible heritable changes, is overlapping.

S110, a 5-Aza-2'-deoxycytidine-containing dinucleotide, is an effective DNA methylation inhibitor in vivo and can reduce tumor growth.

Methylation of CpG islands in promoter regions is often associated with gene silencing and aberrant DNA methylation occurs in most cancers, leading to the silencing of some tumor suppressor genes. Reversal of this abnormal hypermethylation by DNA methylation inhibitors is effective in reactivating methylation-silenced tumor suppressor genes both in vitro and in vivo. Several DNA methylation inhibitors have been well studied; the most potent among them is 5-aza-2'-deoxycytidine (5-Aza-CdR), which can induce myelosuppression in patients. S110 is a dinucleotide consisting of 5-Aza-CdR followed by a deoxyguanosine, which we previously showed to be effective in vitro as a DNA methylation inhibitor while being less prone to deamination by cytidine deaminase, making it a promising alternative to 5-Aza-CdR. Here, we show that S110 is better tolerated than 5-Aza-CdR in mice and is as effective in vivo in inducing p16 expression, reducing DNA methylation at the p16 promoter region, and retarding tumor growth in human xenograft. We also show that S110 is effective by both i.p. and s.c. deliveries. S110 therefore is a promising new agent that acts similarly to 5-Aza-CdR and has better stability and less toxicity.