Inhibition of DNA methyltransferase induces G2 cell cycle arrest and apoptosis in human colorectal cancer cells via inhibition of JAK2/STAT3/STAT5 signalling

The role of suppressor of cytokine signaling 3 in inflammatory bowel disease and its associated colorectal cancer

Inflammatory bowel disease (IBD) and colorectal cancer (CRC), as two of the major human intestinal diseases, provide challenges for the medical field. Suppressor of cytokine signaling 3 (SOCS3), a protein molecule that negatively regulates cytokine signaling through multiple pathways, is involved in the regulation of various inflammatory diseases and tumors. In IBD, SOCS3 acts on a variety of cells to repair mucosal damage and balance the immune response, including epithelial cells, macrophages, dendritic cells, neutrophils, and T cells. In CRC, SOCS3 is inextricably linked to tumor cell proliferation, invasion, metastasis, and drug resistance. Therefore, it is crucial to systematically investigate the pathogenic involvement of SOCS3 in IBD and CRC. This article reviews the mechanisms and pathways by which SOCS3 is involved in the inhibition of IBD and the mitigation of CRC, and details the therapeutic options for targeting SOCS3.

Prognostic value and immune infiltration of a tumor microenvironment-related PTPN6 in metastatic melanoma

BACKGROUND

Cutaneous melanoma is one of the most invasive and lethal skin malignant tumors. Compared to primary melanoma, metastatic melanoma (MM) presents poorer treatment outcomes and a higher mortality rate. The tumor microenvironment (TME) plays a critical role in MM progression and immunotherapy resistance. This study focuses on the role of the TME-related gene PTPN6 in the prognosis and immunotherapy response of MM.

METHODS

This study analyzed the RNA-seq and clinical data of MM patients from public databases, employing the ESTIMATE algorithm and bioinformatics tools to identify differentially expressed genes in the TME. PTPN6 was identified as a prognostic biomarker. Its expression and function were validated using in vitro and in vivo experiments. The role of PTPN6 in immune cell infiltration and its association with the JAK2-STAT3 pathway and immunotherapy response were also evaluated.

RESULTS

PTPN6 expression was significantly lower in MM and associated with poor prognosis. In vitro, Overexpression of PTPN6 inhibited proliferation, migration, and invasion, while knockdown reversed these effects. In vivo, PTPN6 overexpression reduced tumor growth. Mechanistically, PTPN6 suppressed JAK2-STAT3 signaling pathway activation. High PTPN6 expression was positively associated with immune cell infiltration, improved immunotherapy response, and reduced PD-L1 expression.

CONCLUSION

The gene PTPN6, associated with the tumor microenvironment, may serve as a promising prognostic biomarker and therapeutic target for MM.

Unveiling the impact of DNA methylation machinery: Dnmt1 and Dnmt3a in orchestrating oocyte development and cellular homeostasis

DNA methylation can be considered the most prominent in controlling the gene expression responsible for the balance between cell proliferation and cell death. In this study, we aimed to analyze the distinct contributions of Dnmt1 and Dnmt3a enzymes in oocyte maturation, survival, autophagy, reactive oxygen species (ROS) production, and compensation capacity of Dnmt3b and Dnmt3l enzymes in mouse oocytes. Following confirming the suppression of Dnmt1or Dnmt3a through siRNA application, the assessment involved immunofluorescence staining for Dnmts, 5mC, p62, and ROS levels. Cell death rates showed a noticeable increase while oocyte maturation rates exhibited significant reduction. Global DNA methylation showed a decline, concomitant with elevated p62 and ROS levels upon Dnmt1 or Dnmt3a knockdown. Remarkably, silencing of Dnmt1 led to an upsurge in Dnmt3a expression, whereas Dnmt3a knockdown triggered an increase in Dnmt1 levels. Furthermore, Dnmt3l expression exhibited a notable decrease after silencing of either Dnmt1 or Dnmt3a, while Dnmt3b levels remained comparable between control and siRNA-treated groups. Collectively, this study underscores the pivotal roles of Dnmt1 and Dnmt3a in orchestrating various facets of oocyte development, encompassing maturation, survival, autophagy, and ROS production. These findings offer valuable insights into the intricate regulatory network governed by DNA methylation machinery within the context of oocyte physiology.

STAT3 as a newly emerging target in colorectal cancer therapy: Tumorigenesis, therapy response, and pharmacological/nanoplatform strategies

Colorectal cancer (CRC) ranks as the third most aggressive tumor globally, and it can be categorized into two forms: colitis-mediated CRC and sporadic CRC. The therapeutic approaches for CRC encompass surgical intervention, chemotherapy, and radiotherapy. However, even with the implementation of these techniques, the 5-year survival rate for metastatic CRC remains at a mere 12-14%. In the realm of CRC treatment, gene therapy has emerged as a novel therapeutic approach. Among the crucial molecular pathways that govern tumorigenesis, STAT3 plays a significant role. This pathway is subject to regulation by cytokines and growth factors. Once translocated into the nucleus, STAT3 influences the expression levels of factors associated with cell proliferation and metastasis. Literature suggests that the upregulation of STAT3 expression is observed as CRC cells progress towards metastatic stages. Consequently, elevated STAT3 levels serve as a significant determinant of poor prognosis and can be utilized as a diagnostic factor for cancer patients. The biological and malignant characteristics of CRC cells contribute to low survival rates in patients, as the upregulation of STAT3 prevents apoptosis and promotes pro-survival autophagy, thereby accelerating tumorigenesis. Furthermore, STAT3 plays a role in facilitating the proliferation of CRC cells through the stimulation of glycolysis and promoting metastasis via the induction of epithelial-mesenchymal transition (EMT). Notably, an intriguing observation is that the upregulation of STAT3 can mediate resistance to 5-fluorouracil, oxaliplatin, and other anti-cancer drugs. Moreover, the radio-sensitivity of CRC diminishes with increased STAT3 expression. Compounds such as curcumin, epigallocatechin gallate, and other anti-tumor agents exhibit the ability to suppress STAT3 and its associated pathways, thereby impeding tumorigenesis in CRC. Furthermore, it is worth noting that nanostructures have demonstrated anti-proliferative and anti-metastatic properties in CRC.

Thymoquinone Enhances Apoptosis of K562 Chronic Myeloid Leukemia Cells through Hypomethylation of SHP-1 and Inhibition of JAK/STAT Signaling Pathway

The epigenetic silencing of tumor suppressor genes (TSGs) is critical in the development of chronic myeloid leukemia (CML). SHP-1 functions as a TSG and negatively regulates JAK/STAT signaling. Enhancement of SHP-1 expression by demethylation provides molecular targets for the treatment of various cancers. Thymoquinone (TQ), a constituent of Nigella sativa seeds, has shown anti-cancer activities in various cancers. However, TQs effect on methylation is not fully clear. Therefore, the aim of this study is to assess TQs ability to enhance the expression of SHP-1 through modifying DNA methylation in K562 CML cells. The activities of TQ on cell cycle progression and apoptosis were evaluated using a fluorometric-red cell cycle assay and Annexin V-FITC/PI, respectively. The methylation status of SHP-1 was studied by pyrosequencing analysis. The expression of SHP-1, TET2, WT1, DNMT1, DNMT3A, and DNMT3B was determined using RT-qPCR. The protein phosphorylation of STAT3, STAT5, and JAK2 was assessed using Jess Western analysis. TQ significantly downregulated the DNMT1 gene, DNMT3A gene, and DNMT3B gene and upregulated the WT1 gene and TET2 gene. This led to hypomethylation and restoration of SHP-1 expression, resulting in inhibition of JAK/STAT signaling, induction of apoptosis, and cell cycle arrest. The observed findings imply that TQ promotes apoptosis and cell cycle arrest in CML cells by inhibiting JAK/STAT signaling via restoration of the expression of JAK/STAT-negative regulator genes.

The Effect of 5-aza,2'-deoxyCytidine (5 AZA CdR or Decitabine) on Extrinsic, Intrinsic, and JAK/STAT Pathways in Neuroblastoma and Glioblastoma Cells Lines

Epigenetic changes such as histone deacetylation and DNA methylation play to regulate gene expression. DNA methylation plays a major role in cancer induction via transcriptional silencing of critical regulators such as tumor suppressor genes (TSGs). One approach to inhibit TSGs inactivation is to use chemical compounds, DNA methyltransferase inhibitors (DNMTIs). Previously, we investigated the effect of 5-aza-2'-deoxycytidine (5 AZA CdR or decitabine) on colon cancer and hepatocellular carcinoma cell lines. The present study aimed to investigate the effect of 5 AZA CdR on extrinsic (DR4, DR5, FAS, FAS-L, and TRAIL genes), intrinsic [pro- (Bax, Bak, and Bim) and anti- (Bcl-2, Bcl-xL, and Mcl-1) apoptotic genes], and JAK/STAT (SOCS1, SOCS3, JAK1, JAK2, STAT3, STAT5A, and STAT5B genes) pathways in neuroblastoma (IMR-32, SK-N-AS, UKF-NB-2, UKF-NB-3, and UKF-NB-4) and glioblastoma (SF-767, SF-763, A-172, U-87 MG, and U-251 MG) cell lines.

MATERIALS AND METHODS

The neuroblastoma and glioblastoma cells were cultured and treated with 5 AZA CdR. To determine cell viability, cell apoptosis, and the relative gene expression level, MTT assay, flow cytometry assay, and qRT-PCR were done respectively.

RESULTS

5 AZA CdR changed the expression level of the genes of the extrinsic, intrinsic, and JAK/STAT pathways by which induced cell apoptosis and inhibited cell growth in neuroblastoma and glioblastoma cell lines.

CONCLUSION

5 AZA CdR can play its role through extrinsic, intrinsic, and JAK/STAT pathways to induce cell apoptosis.

Reactivation of oncogenes involved in G1/S transcription and apoptosis pathways by low dose decitabine promotes HT29 human colon cancer cell growth in vitro

BACKGROUND

To examine the effects of low-dose decitabine (DAC) on the proliferation of HT-29 cell lines, and to explore the central mechanism by which low-dose DAC affects HT-29 cell proliferation using a systematic biological approach.

METHODS

First, we examined the global effects of DAC on cell proliferation, the cell cycle, and apoptosis in HT29 colon cancer cells. Then, a series test of cluster (STC) analysis and weighted gene coexpression network analysis (WGCNA) were employed to identify critical pathways involved in the response to DAC treatment using 3 datasets from the GEO database. Finally, the expression changes and promoter methylation levels of hub genes were further confirmed by in vitro experiments.

RESULTS

Low-dose DAC (less than 1 µM) promoted the proliferation and colony formation ability of HT-29 cell lines. The results of the system-level analysis, including STC analysis, WGCNA, and Gene set variation analysis (GSVA), showed that DAC modulated 3 critical pathways: G1/S-specific transcription involved in E2F-mediated regulation of Cyclin E-associated events, apoptosis pathways, and EMT pathways. Subsequent in vitro experiments showed that low-dose DAC (0.1 µM) promoted G1/S-specific transcription and decreased apoptosis rates. Then, several regulatory hub oncogenes in these 3 pathways, CCNE1, E2F1, BCL2, PCNA, FOXC1, VIM, CXCL1, and VCAM1, were further confirmed to be activated by DAC at either the mRNA or protein level. We chose the oncogene BCL2 as an example and detected its methylation status and the effect of low-dose DAC on BCL2 expression. Data from TCGA and Oncomine databases demonstrated that BCL2 was decreased in colon cancer compared with normal mucosa. Further analysis showed that BCL2 had an increased degree of promoter methylation in 12 methylated sites in colon cancer compared with normal colon tissues. Bisulfite sequencing PCR showed that low-dose DAC decreased the methylation rate at the BCL2 promoter region.

CONCLUSIONS

We concluded that low-dose DAC treatment resulted in a cancer-promoting effect in HT29 cell lines. Mechanistically, high methylation levels at the promoter region of oncogenes with dominant effects in CRC, such as BCL2 in HT29, might play a role in suppressing CRC by inhibiting oncogene expression. Low-dose DAC treatment triggered BCL2 expression by decreasing its promoter methylation level, thereby resulting in cancer promotion.

Enzyme-mediated depletion of serum l-Met abrogates prostate cancer growth via multiple mechanisms without evidence of systemic toxicity

Extensive studies in prostate cancer and other malignancies have revealed that l-methionine (l-Met) and its metabolites play a critical role in tumorigenesis. Preclinical and clinical studies have demonstrated that systemic restriction of serum l-Met, either via partial dietary restriction or with bacterial l-Met-degrading enzymes exerts potent antitumor effects. However, administration of bacterial l-Met-degrading enzymes has not proven practical for human therapy because of problems with immunogenicity. As the human genome does not encode l-Met-degrading enzymes, we engineered the human cystathionine-γ-lyase (hMGL-4.0) to catalyze the selective degradation of l-Met. At therapeutically relevant dosing, hMGL-4.0 reduces serum l-Met levels to >75% for >72 h and significantly inhibits the growth of multiple prostate cancer allografts/xenografts without weight loss or toxicity. We demonstrate that in vitro, hMGL-4.0 causes tumor cell death, associated with increased reactive oxygen species, S-adenosyl-methionine depletion, global hypomethylation, induction of autophagy, and robust poly(ADP-ribose) polymerase (PARP) cleavage indicative of DNA damage and apoptosis.

Investigation of the Effect of Zebularine in Comparison to and in Combination with Trichostatin A on p21Cip1/Waf1/ Sdi1, p27Kip1, p57Kip2, DNA Methyltransferases and Histone Deacetylases in Colon Cancer LS 180 Cell Line

BACKGROUND

The heart of the cell cycle regulatory machine is a group of enzymes named cyclin-dependent kinases (Cdks). The active form of these enzymes includes a kinase and its partner, a cyclin. The regulation of cyclin-Cdk complexes is provided by Cdk inhibitors (CKIs) such as Cip/Kip family comprising p21Cip1/Waf1/Sdi1, p27Kip1, and p57Kip2. The hypermethylation and deacetylation of Cip/Kip gene family seem to be frequent in numerous cancers. It has been indicated that increased expression of DNMTs and HDACs contributes to cancer induction. Previously, we reported the effect of DNA demethylating agents and histone deacetylase inhibitors on histone deacetylase 1, DNA methyltransferase 1, and CIP/KIP family in colon cancer. The current study was designed to evaluate the effect of zebularine in comparison to and in combination with trichostatin A (TSA) on p21Cip1/Waf1/Sdi1, p27Kip1, p57Kip2, DNA methyltransferases (DNMT1, 3a and 3b) and histone deacetylases (HDAC1, 2, and 3) genes expression, cell growth inhibition and apoptosis induction in colon cancer LS 180 cell line.

MATERIALS AND METHODS

The colon cancer LS 180 cell line was cultured and treated with zebularine and TSA. To determine cell viability, apoptosis, and the relative expression level of the genes, MTT assay, cell apoptosis assay, and qRT-PCR were done respectively.

RESULTS

Both compounds significantly inhibited cell growth, and induced apoptosis. Furthermore, both compounds increased p21Cip1/Waf1/Sdi1, p27Kip1, and p57Kip2 significantly. Additionally, zebularine and TSA decreased DNMTs and HDACs gene expression respectively.

CONCLUSION

The zebularine and TSA can reactivate the CIP/KIP family through inhibition of DNMTs and HDACs genes activity.
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Epigenetics/epigenomics and prevention by curcumin of early stages of inflammatory-driven colon cancer

Colorectal cancer (CRC) is associated with significant morbidity and mortality in the US and worldwide. CRC is the second most common cancer-related death in both men and women globally. Chronic inflammation has been identified as one of the major risk factors of CRC. It may drive genetic and epigenetic/epigenomic alterations, such as DNA methylation, histone modification, and non-coding RNA regulation. Current prevention modalities for CRC are limited and some treatment regimens such as use the nonsteroidal anti-inflammatory drug aspirin may have severe side effects, namely gastrointestinal ulceration and bleeding. Therefore, there is an urgent need of developing alternative strategies. Recently, increasing evidence suggests that several dietary cancer chemopreventive phytochemicals possess anti-inflammation and antioxidative stress activities, and may prevent cancers including CRC. Curcumin (CUR) is the yellow pigment that is found in the rhizomes of turmeric (Curcuma longa). Many studies have demonstrated that CUR exhibit strong anticancer, antioxidative stress, and anti-inflammatory activities by regulating signaling pathways, such as nuclear factor erythroid-2-related factor 2, nuclear factor-κB, and epigenetics/epigenomics pathways of histones modifications, and DNA methylation. In this review, we will discuss the latest evidence in epigenetics/epigenomics alterations by CUR in CRC and their potential contribution in the prevention of CRC.

Effect of 5-Aza-2'-Deoxycytidine in Comparison to Valproic Acid and Trichostatin A on Histone Deacetylase 1, DNA Methyltransferase 1, and CIP/KIP Family (p21, p27, and p57) Genes Expression, Cell Growth Inhibition, and Apoptosis Induction in Colon Cancer SW480 Cell Line

BACKGROUND

Cancer initiation and progression depends on genetic and epigenetic alterations such as DNA methylation and histone modifications. Hypermethylation and deacetylation of the CIP/KIP family (p21, p27, and p57) lead to tumorigenesis. Our previous study indicated that DNA methyltransferase (DNMT) inhibitor and histone deacetylase (HDAC) inhibitors can inhibit cell growth and induce apoptosis. The aim of the present study was to investigate the effect of 5-Aza-2'-deoxycytidine (5-Aza-CdR) in comparison to valproic acid (VPA) and trichostatin A (TSA) on HDAC1, DNMT1, and CIP/KIP family (p21, p27, and p57) genes expression, cell growth inhibition, and apoptosis induction in colon cancer SW480 cell line.

MATERIALS AND METHODS

The effect of the compounds on the cell viability was measured by MTT assay. The expression of HDAC1, DNMT1, and CIP/KIP family (p21, p27, and p57) genes was evaluated by real-time quantitative reverse transcription-polymerase chain reaction (RT-PCR). For the detection of cell apoptosis, apoptotic cells were examined by the Annexin V-FITC/PI detection kit.

RESULTS

The results of MTT assay indicated that 5-Aza-CdR, VPA, and TSA significantly inhibited cell growth (P < 0.002, P < 0.001, and P < 0.001, respectively). The results of real-time RT-PCR demonstrated that all compounds significantly down-regulated DNMT1 and HDAC1, and up-regulated p21, p27, and p57 genes expression. The result of flow cytometry assay revealed that all agents induced apoptosis significantly.

CONCLUSION

5-Aza-CdR, VPA, and TSA can significantly downregulate DNMT1 and HDAC1 and up-regulate p21, p27, and p57 genes expression through which enhance cell apoptosis and cell growth inhibition in colon cancer.

Potassium bisperoxo (1,10-phenanthroline) oxovanadate suppresses proliferation of hippocampal neuronal cell lines by increasing DNA methyltransferases

Bisperoxo (1,10-phenanthroline) oxovanadate (BpV) can reportedly block the cell cycle. The present study examined whether BpV alters gene expression by affecting DNA methyltransferases (DNMTs), which would impact the cell cycle. Immortalized mouse hippocampal neuronal precursor cells (HT22) were treated with 0.3 or 3 μM BpV. Proliferation, morphology, and viability of HT22 cells were detected with an IncuCyte real-time video imaging system or inverted microscope and 3-(4,5-dimethylthiazol-2-yl)-5(3-carboxymethonyphenol)-2-(4-sulfophenyl)-2H-tetrazolium, respectively. mRNA and protein expression of DNMTs and p21 in HT22 cells was detected by real-time polymerase chain reaction and immunoblotting, respectively. In addition, DNMT activity was measured with an enzyme-linked immunosorbent assay. Effects of BpV on the cell cycle were analyzed using flow cytometry. Results demonstrated that treatment with 0.3 μM BpV did not affect cell proliferation, morphology, or viability; however, treatment with 3 μM BpV decreased cell viability, increased expression of both DNMT3B mRNA and protein, and inhibited the proliferation of HT22 cells; and 3 μM BpV also blocked the cell cycle and increased expression of the regulatory factor p21 by increasing DNMT expression in mouse hippocampal neurons.

Epigenetic-based therapy for colorectal cancer: Prospect and involved mechanisms

Epigenetic modifications are heritable variations in gene expression not encoded by the DNA sequence. According to reports, a large number of studies have been performed to characterize epigenetic modification during normal development and also in cancer. Epigenetics can be regarded more widely to contain all of the changes in expression of genes that make by adjusted interactions between the regulatory portions of DNA or messenger RNAs that lead to indirect variation in the DNA sequence. In the last decade, epigenetic modification importance in colorectal cancer (CRC) pathogenesis was demonstrated powerfully. Although developments in CRC therapy have been made in the last years, much work is required as it remains the second leading cause of cancer death. Nowadays, epigenetic programs and genetic change have pivotal roles in the CRC incidence as well as progression. While our knowledge about epigenetic mechanism in CRC is not comprehensive, selective histone modifications and resultant chromatin conformation together with DNA methylation most likely regulate CRC pathogenesis that involved genes expression. Undoubtedly, the advanced understanding of epigenetic-based gene expression regulation in the CRC is essential to make epigenetic drugs for CRC therapy. The major aim of this review is to deliver a summary of valuable results that represent evidence of principle for epigenetic-based therapeutic approaches employment in CRC with a focus on the advantages of epigenetic-based therapy in the inhibition of the CRC metastasis and proliferation.

Inhibition of STAT3 in gastric cancer: role of pantoprazole as SHP-1 inducer

Background

We investigated the inhibitory effect of pantoprazole on signal transducer and activator of transcription 3 (STAT3) activity and invasiveness of gastric adenocarcinoma cells, and the role of SH2-containing protein tyrosine phosphatase 1 (SHP-1) in mediating role.

Methods

We used AGS and MKN-28 cells because of reduced SHP-1 and preserved p-STAT3 expression. Western blot, wound closure assay, Matrigel invasion assay and 3-D culture invasion assay were performed. Pharmacologic inhibitor of SHP-1 and siRNA were used for validation of the role of SHP-1.

Results

We observed that pantoprazole at 40, 80, and 160 μg/ml upregulated SHP-1 and downregulated p-STAT3 expression in a dose-dependent manner in AGS and MKN-28 cells. Furthermore, pantoprazole significantly downregulated mesenchymal markers (Snail1 and vimentin), upregulated epithelial marker (E-cadherin), and inhibited migration and invasion of AGS and MKN-28 cells. To validate the role of SHP-1 in inhibition of STAT3 activity by pantoprazole in gastric cancer cells, we performed pharmacologic inhibition (pervanadate) or knockdown of SHP-1 before pantoprazole treatment, which significantly attenuated the suppression of p-STAT3 and anti-migration and invasion effect by pantoprazole in AGS cells. In xenograft tumor model, tumor volume was significantly reduced by intraperitoneal injection of pantoprazole, with upregulation of SHP-1 and downregulation of p-STAT3, which were attenuated by concomitant injection of pervanadate.

Conclusion

Our data suggest that the inhibitory effect of pantoprazole on cellular migration and invasion might be through inducing SHP-1 in gastric cancer cells.

Effects and mechanism of STAT3 silencing on the growth and apoptosis of colorectal cancer cells

Signal transducer and activator of transcription 3 (STAT3) have roles in various cellular processes, including angiogenesis, apoptosis, cell cycle progression, cell migration and drug resistance. To clarify the effects of STAT3 in colorectal cancer (CRC) cells and the underlying molecular mechanisms, STAT3 was directly silenced, and the effects of STAT3 silencing on cell proliferation, apoptosis and growth with phenotype-associated molecules were examined.pSH1-Si-STAT3 was successfully transfected into the CRC HCT-116 and SW480 cell lines, which was verified by GFP tagging under a fluorescence microscope. An MTT assay revealed that the proliferation of both cell lines that were transfected with pSH1-Si-STAT3 was significantly suppressed in comparison with the control and mock (P<0.05). Acridine orange/ethidium bromide staining and flow cytometry indicated that the transfected cell lines had a significantly higher rate of apoptosis than the control- and mock-treated cells (P<0.05). STAT3-silienced cells were also significantly arrested at the G₂/M stage compared with the cells that were transfected with control and mock plasmids (P<0.05). At the mRNA level, the expression of STAT3 and survivin was significantly downregulated (P<0.05), but p53 and caspase-3 were significantly upregulated (P<0.05). The significantly different patterns of expression were observed in western blot analysis (P<0.05). The findings of the present study indicate that STAT3 silencing may suppress the proliferation and growth of CRC cells, and induce their apoptosis by upregulating the expression of survivin, p53 and caspase-3. Therefore, STAT3 may be a good candidate for CRC gene therapy.

Epigenetic regulation of NFE2 overexpression in myeloproliferative neoplasms

The transcription factor "nuclear factor erythroid 2" (NFE2) is overexpressed in the majority of patients with myeloproliferative neoplasms (MPNs). In murine models, elevated NFE2 levels cause an MPN phenotype with spontaneous leukemic transformation. However, both the molecular mechanisms leading to NFE2 overexpression and its downstream targets remain incompletely understood. Here, we show that the histone demethylase JMJD1C constitutes a novel NFE2 target gene. JMJD1C levels are significantly elevated in polycythemia vera (PV) and primary myelofibrosis patients; concomitantly, global H3K9me1 and H3K9me2 levels are significantly decreased. JMJD1C binding to the NFE2 promoter is increased in PV patients, decreasing both H3K9me2 levels and binding of the repressive heterochromatin protein-1α (HP1α). Hence, JMJD1C and NFE2 participate in a novel autoregulatory loop. Depleting JMJD1C expression significantly reduced cytokine-independent growth of an MPN cell line. Independently, NFE2 is regulated through the epigenetic JAK2 pathway by phosphorylation of H3Y41. This likewise inhibits HP1α binding. Treatment with decitabine lowered H3Y41ph and augmented H3K9me2 levels at the NFE2 locus in HEL cells, thereby increasing HP1α binding, which normalized NFE2 expression selectively in JAK2V617F-positive cell lines.

Cryptotanshinone induces ROS-mediated apoptosis in human gastric cancer cells

Cryptotanshinone (CT), isolated from the plant Salvia miltiorrhiza Bunge, has been reported to have potential anticancer effects on human prostate and breast cancer cells. However, the mechanisms of action of CT on gastric cancer (GC) cells are not well understood. Here we investigated the antitumor effects of CT on GC cells and its possible molecular mechanism. We found CT suppressed viability of twelve GC cell lines in a dose-dependent manner. CT induced cell cycle arrest at the G2/M phase and mitochondrial apoptosis accompanying the accumulation of reactive oxygen species (ROS). Pretreatment with ROS inhibitor N-acetyl-L-cysteine (NAC) blocked CT-induced apoptosis. CT increased p-JNK and p-p38, and decreased p-ERK and p-STAT3 protein expression, these effects were prevented by NAC. Furthermore, a xenograft assay showed that CT significantly inhibited MKN-45 cell-induced tumor growth in vivo by increasing expression of pro-apoptotic proteins (p-JNK, p-38 and cleaved-caspase-3) and reducing expression of anti-apoptotic proteins (p-ERK and p-STAT3) without adverse effects on nude mice weight. In conclusion, CT induced apoptosis and cell cycle arrest in GC cells via ROS-mediated MAPK and AKT signaling pathways, and this CT may be a useful compound for the developing anticancer agents for GC.

5-Aza-2'-deoxycytidine, a DNA methylation inhibitor, induces cytotoxicity, cell cycle dynamics and alters expression of DNA methyltransferase 1 and 3A in mouse hippocampus-derived neuronal HT22 cells

Epigenetic processes such as DNA methylation are essential for processes of gene expression in normal mammalian development. DNA methyltransferases (DNMT) are responsible for initiating and maintaining DNA methylation. It is known that 5-Aza-CdR, an inhibitor of DNMT induces cytotoxicity by reducing DNMT activity in various tumor cell lines. However, disturbances in neuronal DNA methylation may also play a role in altered brain functions. Thus, it was of interest to determine whether alterations in DNA methylation might be associated with neuronal functions by using 5-Aza-CdR, on mouse hippocampus-derived neuronal HT22 cell line. In particular, the aim of this study was to investigate the effects of 5-Aza-CdR on cell growth inhibition, cell cycle arrest, apoptosis as well as the expression levels of DNMT in HT22 cells. HT22 cells were incubated with 5 or 20 μmol/L 5-Aza-CdR for 24 h. Data showed that 5-Aza-CdR at both concentrations significantly inhibited proliferation of HT22 cells and exacerbated cytoplasmic vacuolization. Flow cytometry analysis demonstrated that 5-Aza-CdR treatment at both concentrations decreased early apoptosis but enhanced late apoptosis. Cell cycle analysis illustrated that 5-Aza-CdR treatment induced S phase arrest. Further, incubation with 5-Aza-CdR produced a down-regulation in expression of mRNA and protein DNMT1 and 3A but no marked changes were noted in DNMT 3B and p21 expression. In addition, DNMT1 activity was significantly decreased at both 5-Aza-CdR concentrations. Evidence indicates that 5-Aza-CdR induced cytotoxicity was associated with altered mRNA and protein expression of DNMT 1 and 3A associated with reduced DNMT1 activity in HT22 cells which might affect brain functions.

Methylation of mitochondrial DNA displacement loop region regulates mitochondrial copy number in colorectal cancer

It is not established whether de-methylation of the displacement loop (D-loop) region if mitochondrial DNA (mtDNA) directly influences mtDNA copy number and further alters the cell cycle, apoptosis and cell proliferation in colorectal cancer. The current study employed cell viability assays, cell cycle analysis, and mtDNA methylation analysis using 5 colorectal cancer cell lines. The present results demonstrated that 5-aza-2′-deoxycytidine (5-AZA), a DNA hypomethylating agent, significantly increased proliferation of Lovo and Colo-205 colorectal cancer cell lines. In Colo-205 cells, the proportion of G₀/G₁ phase cells was increased following 5-AZA treatment. Additionally, the apoptosis rate in Colo-205 cells was decreased by 5-AZA treatment. Compared with their controls, a significantly higher mtDNA copy number was observed in Colo-205 and Lovo cells following 5-AZA treatment. Notably, the Colo-205 and Lovo cells had relatively higher methylation levels at the 4 and 6th/7th CpG sites of D-loop region, respectively, compared with the levels at the corresponding sites following 5-AZA treatment. However, in HCT116, SW480, LS-174T, and HT-29 cells, 5-AZA treatment did not induce a significant change in proliferation, cell cycle, apoptosis and mtDNA copy number. Demethylation at the 4 and 6th/7th CpG sites of the D-loop region of HCT116, SW480, LS-174T and HT-29 cells was not observed following 5-AZA treatment. In conclusion, de-methylation of specific sites on CpG islands of D-loop promoter may lead to the elevation of mtDNA copy number in colorectal cancer, triggering alterations in biological behaviors, including increased cell proliferation, reduced apoptosis and a relative cell cycle arrest in G₀/G₁ phase.

B7-H3 is related to tumor progression in ovarian cancer

B7-H3, a co-stimulatory molecule, has been found expressed in ovarian cancer, but its role and mechanism is not clear. In this study, we further verified the expression of B7-H3 in ovarian carcinoma and normal epithelial ovarian tissues. Three ovarian cancer cell lines, A2780, SKOV3 and HO8910 were selected to explore the effects of B7-H3 on proliferation, apoptosis, migration and invasion. We found that B7-H3 was mainly located in the cytoplasm of ovarian cancer cells as determined by immunofluorescence staining. The ability of cell invasion, migration, proliferation decreased after silencing B7-H3 whereas the apoptosis increased, which was related to the upregulation of Bax, caspase-8, cleaved caspase-8 and the downregulation of Bcl-2, Bcl-xl, matrix metalloproteinase-2 (MMP2) by western blotting. In addition, B7-H3 enhanced the H08910 cell capacities in invasion, migration and proliferation. Expression of the phosphorylation signal transducer and activator of transcription 3 (pStat3) molecules and their upstream molecules phosphorylation Janus kinase 2 (pJak2) were significantly increased. In order to investigate whether B7-H3 plays a role in this pathway, we treated the overexpressed HO8910 cells with AG490 (inhibitors of Jak2). Our findings revealed that B7-H3 affect ovarian cancer progression through the Jak2/Stat3 pathway, indicating that B7-H3 has the potential to be a useful prognostic marker.

Demethylating agent decitabine disrupts tumor-induced immune tolerance by depleting myeloid-derived suppressor cells

PURPOSE

The immunoregulatory effect of demethylating agent decitabine (DAC) has been recognized recently. However, little is known about its impact on immune tolerance. In this study, we aimed to determine the impact of DAC on the immune tolerance induced by tumor cells.

METHODS

The effects of DAC on immune cells in vivo were measured by flow cytometry. Myeloid-derived suppressor cells (MDSCs) were sorted using magnetic beads and cultured in vitro. The mixed lymphocyte reaction was used to determine the immunoregulatory effect of DAC in vitro. An adoptive transfusion mouse model was established to evaluate the effect in vivo.

RESULTS

We found that DAC treatment significantly depleted MDSCs in vivo by inducing MDSCs apoptosis. When given at a low dose, the immune effector cells were less affected by the treatment, except for MDSCs. The mixed lymphocyte reaction in vitro showed that T-cell responses were enhanced when MDSCs were depleted. Supplementation of MDSCs would attenuate this T-cell activation effect. Using an adoptive transfusion mouse model, we further demonstrated in vivo that DAC treatment could induce autologous anti-tumor immune response by depleting MDSCs.

CONCLUSIONS

This study is the first to illustrate DAC's immunoregulatory effect on immune tolerance. The disruption of immune tolerance is due to MDSCs depletion that induces an autologous immune response in vivo. By depleting MDSCs, DAC treatment removes one of the obstacles affecting anti-tumor immune activation and warrants further experimental and clinical studies to explore its potential utility in combination with various anti-tumor immunotherapies in the future.

Bioactive Potential of Marine Macroalgae from the Central Red Sea (Saudi Arabia) Assessed by High-Throughput Imaging-Based Phenotypic Profiling

Marine algae represent an important source of novel natural products. While their bioactive potential has been studied to some extent, limited information is available on marine algae from the Red Sea. This study aimed at the broad discovery of new bioactivities from a collection of twelve macroalgal species from the Central Red Sea. We used imaging-based High-Content Screening (HCS) with a diverse spectrum of cellular markers for detailed cytological profiling of fractionated algal extracts. The cytological profiles for 3 out of 60 algal fractions clustered closely to reference inhibitors and showed strong inhibitory activities on the HIV-1 reverse transcriptase in a single-enzyme biochemical assay, validating the suggested biological target. Subsequent chemical profiling of the active fractions of two brown algal species by ultra-high resolution mass spectrometry (FT-ICR-MS) revealed possible candidate molecules. A database query of these molecules led us to groups of compounds with structural similarities, which are suggested to be responsible for the observed activity. Our work demonstrates the versatility and power of cytological profiling for the bioprospecting of unknown biological resources and highlights Red Sea algae as a source of bioactives that may serve as a starting point for further studies.

Enhancing SHP-1 expression with 5-azacytidine may inhibit STAT3 activation and confer sensitivity in lestaurtinib (CEP-701)-resistant FLT3-ITD positive acute myeloid leukemia

Background

Tumor-suppressor genes are inactivated by methylation in several cancers including acute myeloid leukemia (AML). Src homology-2 (SH2)-containing protein-tyrosine phosphatase 1 (SHP-1) is a negative regulator of the JAK/STAT pathway. Transcriptional silencing of SHP-1 plays a critical role in the development and progression of cancers through STAT3 activation. 5-Azacytidine (5-Aza) is a DNA methyltransferase inhibitor that causes DNA demethylation resulting in re-expression of silenced SHP-1. Lestaurtinib (CEP-701) is a multi-targeted tyrosine kinase inhibitor that potently inhibits FLT3 tyrosine kinase and induces hematological remission in AML patients harboring the internal tandem duplication of the FLT3 gene (FLT3-ITD). However, the majority of patients in clinical trials developed resistance to CEP-701. Therefore, the aim of this study, was to assess the effect of re-expression of SHP-1 on sensitivity to CEP-701 in resistant AML cells.

Methods

Resistant cells harboring the FLT3-ITD were developed by overexposure of MV4-11 to CEP-701, and the effects of 5-Aza treatment were investigated. Apoptosis and cytotoxicity of CEP-701 were determined using Annexin V and MTS assays, respectively. Gene expression was performed by quantitative real-time PCR. STATs activity was examined by western blotting and the methylation profile of SHP-1 was studied using MS-PCR and pyrosequencing analysis. Repeated-measures ANOVA and Kruskal–Wallis tests were used for statistical analysis.

Results

The cytotoxic dose of CEP-701 on resistant cells was significantly higher in comparison with parental and MV4-11R-cep + 5-Aza cells (p = 0.004). The resistant cells showed a significant higher viability and lower apoptosis compared with other cells (p < 0.001). Expression of SHP-1 was 7-fold higher in MV4-11R-cep + 5-Aza cells compared to parental and resistant cells (p = 0.011). STAT3 was activated in resistant cells. Methylation of SHP-1 was significantly decreased in MV4-11R-cep + 5-Aza cells (p = 0.002).

Conclusions

The restoration of SHP-1 expression induces sensitivity towards CEP-701 and could serve as a target in the treatment of AML. Our findings support the hypothesis that, the tumor-suppressor effect of SHP-1 is lost due to epigenetic silencing and its re-expression might play an important role in re-inducing sensitivity to TKIs. Thus, SHP-1 is a plausible candidate for a role in the development of CEP-701 resistance in FLT3-ITD+ AML patients.

Epigenetic regulation and anti-tumorigenic effects of SH2-containing protein tyrosine phosphatase 1 (SHP1) in human gastric cancer cells

SH2-containing protein tyrosine phosphatase 1 (SHP1) is an important negative regulator in cytokine-mediated signal transduction and cell cycling. Recent studies have demonstrated that SHP1 promoter methylation is frequently observed in gastric adenocarcinoma tissues. In this in vitro study, we attempted to reveal promoter hypermethylation and to investigate effects of SHP1 in gastric carcinoma cell lines. We observed that both gene and protein expression of SHP1 were negative in 8 of 10 gastric cancer cell lines (SNU-1, SNU-5, SNU-16, SNU-638, SNU-719, MKN-28, MKN-45, AGS). Methylation-specific PCR (MSP) showed a methylation-specific band only in the 10 gastric cancer lines. Bisulfite pyrosequencing in AGS, MKN-28, and SNU-719 cells indicated that methylation frequency was as high as 94.4, 92.6, and 94.5 %, respectively, in the three cell lines. Treatment of SNU-719, MKN-28, and AGS cells with 5-Aza-2'-deoxycytidine (5-Aza-dc) led to re-expression of SHP1 in these cells. Introduction of exogenous SHP1 in SNU-719 and MKN-28 cells by transient transfection substantially downregulated protein expression of constitutive phosphor-Janus kinase 2 (JAK2) (tyrosine 1007/1008) and phosphor-signal transducers and activators of transcription 3 (STAT3) (tyrosine 705), which in turn decreased expression of STAT3 target genes including those encoding cyclin D1, MMP-9, VEGF-1, and survivin. Induction of SHP1 significantly inhibited cell proliferation, migration and invasion in SNU-719 and MKN-28 cells. Taken together, epigenetic silencing of SHP1 is frequently caused by promoter hypermethylation in gastric carcinoma cells. Overexpression of SHP1 downregulates the JAK2/STAT3 pathway to modulate various target genes and inhibit cell proliferation, migration, and invasion in gastric cancer cells.

Antitumorigenic effect of plumbagin by induction of SH2-containing protein tyrosine phosphatase 1 in human gastric cancer cells

A recent study reported that plumbagin downregulated the activity of Janus kinase 2 (JAK2)-signal transducer and activator of transcription 3 (STAT3) pathway to show various antitumor effects in multiple myeloma cells. We aimed in this in vitro study to demonstrate the inhibition of JAK2/STAT3 pathway by plumbagin through inducing SH2-containing protein tyrosine phosphatase 1 (SHP1) expression in the MKN-28 gastric cancer cell line. We performed western blot analysis to measure SHP1, phosphor-JAK2/STAT3 level, and observed that plumbagin induced SHP1 expression and simultaneously downregulated phosphor-JAK2/STAT3 in MKN-28 cells, with negative SHP1 expression. This effect was consistent when JAK2/STAT3 signaling was activated by interleukin-6 (IL-6), and ameliorated when cells were treated with prevanadate, a protein tyrosin phosphatase inhibitor. Furthermore, plumbagin significantly reduced gene expression of cyclin D1, vascular endothelial growth factor (VEGF)-1, Bcl-xL, survivin and matrix metalloproteinase-9 (MMP-9), known target products of STAT3 activation in gastric carcinogenesis by reverse transcription-polymerase chain reaction (RT-PCR). Several functional studies such as water soluble tetrazolium salt-1 (WST-1) assay, wound closure assay, Matrigel invasion assay and Annexin V assay were also performed, and we validated the functional effect of plumbagin for inhibition of cell proliferation, migration and invasion, and induction of apoptosis. Collectively, our findings suggest that plumbagin is a potential regulator of cellular growth, migration, invasion and apoptosis by inhibiting both constitutive and inducible STAT3 activity through induction of SHP1 in gastric cancer cells.

Protein expression under sustained activation of signal transducer and activator of transcription-3 in diethylnitrosamine-induced rat liver carcinogenesis

The aim of the present study was to investigate the expression of proteins associated with the sustained activation of the signal transducer and activator of transcription (STAT)-3 pathway during diethylnitrosamine (DEN)-induced rat liver carcinogenesis. DEN was intermittently administered to rats to induce liver cancer, and light and electron microscopy were used to observe the morphological changes in the liver during carcinogenesis. Western blotting and quantitative polymerase chain reaction (qPCR) were used to detect the expression of STAT-3, phosphorylated (p)-STAT-3, matrix metalloproteinase (MMP)-10, vascular endothelial growth factor (VEGF), kinase insert domain receptor (KDR), hypoxia inducible factor (HIF)-1α, basic fibroblast growth factor (bFGF) and interleukin (IL)-10, in order to investigate the association between STAT-3 and p-STAT-3 expression and MMP-10, VEGF, KDR, HIF-1α, bFGF and IL-10. The western blotting and qPCR results revealed that the expression of STAT-3, p-STAT-3, MMP-10, VEGF, KDR, HIF-1α, bFGF and IL-10 proteins gradually increased during carcinogenesis. Furthermore, the STAT-3 and p-STAT-3 levels were found to positively correlate with MMP-10, VEGF, KDR, HIF-1α, bFGF and IL-10 protein expression. During DEN-induced rat liver carcinogenesis, STAT-3 protein continually activated MMP-10, VEGF, KDR, HIF-1α, bFGF and IL-10, and its expression was found to positively correlate with the expression of these proteins.

Inhibition of STAT3 reduces astrocytoma cell invasion and constitutive activation of STAT3 predicts poor prognosis in human astrocytoma

Astrocytoma cells characteristically possess high invasion potentials. Recent studies have revealed that knockdown of signal transducers and activators of transcription 3 (STAT3) expression by RNAi induces apoptosis in astrocytoma cell. Nevertheless, the distinct roles of STAT3 in astrocytoma's invasion and recurrence have not been elucidated. In this study, we silenced STAT3 using Small interfering RNAs in two human glioblastoma multiforme (GBM) cell lines (U251 and U87), and investigated the effect on GBM cell adhesion and invasion. Our results demonstrate that disruption of STAT3 inhibits GBM cell's adhesion and invasion. Knockdown of STAT3 significantly increased E-cadherin but decreased N-cadherin, vascular endothelial growth factor, matrix metalloproteinase 2 and matrix metalloproteinase 9. Additionally, expression of pSTAT3(Tyr705) correlates with astrocytoma WHO classification, Karnofsky performance status scale score, tumor recurrence and survival. Furthermore, pSTAT3(Tyr705) is a significant prognostic factor in astrocytoma. In conclusion, STAT3 may affect astrocytoma invasion, expression of pSTAT3(Tyr705) is a significant prognostic factor in tumor recurrence and overall survival in astrocytoma patients. Therefore, STAT3 may provide a potential target for molecular therapy in human astrocytoma, and pSTAT3(Tyr705)could be an important biomarker for astrocytoma prognosis.

The JAK2/STAT3 and mitochondrial pathways are essential for quercetin nanoliposome-induced C6 glioma cell death

The formulation of quercetin nanoliposomes (QUE-NLs) has been shown to enhance QUE antitumor activity in C6 glioma cells. At high concentrations, QUE-NLs induce necrotic cell death. In this study, we probed the molecular mechanisms of QUE-NL-induced C6 glioma cell death and examined whether QUE-NL-induced programmed cell death involved Bcl-2 family and mitochondrial pathway through STAT3 signal transduction pathway. Downregulation of Bcl-2 and the overexpression of Bax by QUE-NL supported the involvement of Bcl-2 family proteins upstream of C6 glioma cell death. In addition, the activation of JAK2 and STAT3 were altered following exposure to QUE-NLs in C6 glioma cells, suggesting that QUE-NLs downregulated Bcl-2 mRNAs expression and enhanced the expression of mitochondrial mRNAs through STAT3-mediated signaling pathways either via direct or indirect mechanisms. There are several components such as ROS, mitochondrial, and Bcl-2 family shared by the necrotic and apoptotic pathways. Our studies indicate that the signaling cross point of the mitochondrial pathway and the JAK2/STAT3 signaling pathway in C6 glioma cell death is modulated by QUE-NLs. In conclusion, regulation of JAK2/STAT3 and ROS-mediated mitochondrial pathway agonists alone or in combination with treatment by QUE-NLs could be a more effective method of treating chemical-resistant glioma.

BAK and NOXA are critical determinants of mitochondrial apoptosis induced by bortezomib in mesothelioma

Based on promising preclinical efficacy associated with the 20S proteasome inhibitor bortezomib in malignant pleural mesothelioma (MPM), two phase II clinical trials have been initiated (EORTC 08052 and ICORG 05–10). However, the potential mechanisms underlying resistance to this targeted drug in MPM are still unknown. Functional genetic analyses were conducted to determine the key mitochondrial apoptotic regulators required for bortezomib sensitivity and to establish how their dysregulation may confer resistance. The multidomain proapoptotic protein BAK, but not its orthologue BAX, was found to be essential for bortezomib-induced apoptosis in MPM cell lines. Immunohistochemistry was performed on tissues from the ICORG-05 phase II trial and a TMA of archived mesotheliomas. Loss of BAK was found in 39% of specimens and loss of both BAX/BAK in 37% of samples. However, MPM tissues from patients who failed to respond to bortezomib and MPM cell lines selected for resistance to bortezomib conserved BAK expression. In contrast, c-Myc dependent transactivation of NOXA was abrogated in the resistant cell lines. In summary, the block of mitochondrial apoptosis is a limiting factor for achieving efficacy of bortezomib in MPM, and the observed loss of BAK expression or NOXA transactivation may be relevant mechanisms of resistance in the clinic.

Zebularine inhibits the growth of A549 lung cancer cells via cell cycle arrest and apoptosis

Zebularine (Zeb) is a DNA methyltransferase (DNMT) inhibitor to that has an anti-tumor effect. Here, we evaluated the anti-growth effect of Zeb on A549 lung cancer cells in relation to reactive oxygen species (ROS) levels. Zeb inhibited the growth of A549 cells with an IC50 of approximately 70 µM at 72 h. Cell cycle analysis indicated that Zeb induced an S phase arrest in A549 cells. Zeb also induced A549 cell death, which was accompanied by the loss of mitochondrial membrane potential (MMP; ΔΨm ), Bcl-2 decrease, Bax increase, p53 increase and activation of caspase-3 and -8. In contrast, Zeb mildly inhibited the growth of human pulmonary fibroblast (HPF) normal cells and lead to a G1 phase arrest. Zeb did not induce apoptosis in HPF cells. In relation to ROS level, Zeb increased ROS level in A549 cells and induced glutathione (GSH) depletion. The well-known antioxidant, N-acetyl cysteine (NAC) prevented the death of Zeb-treated A549 cells. Moreover, Zeb increased the level of thioredoxin reductase 1 (TrxR1) in A549 cells. While the overexpression of TrxR1 attenuated death and ROS level in Zeb-treated A549 cells, the downregulation of TrxR1 intensified death and ROS level in these cells. In conclusion, Zeb inhibited the growth of A549 lung cancer cells via cell cycle arrest and apoptosis. The inhibition was influenced by ROS and TrxR1 levels.

Cytotoxicity of 5-Aza-2'-deoxycytidine against gastric cancer involves DNA damage in an ATM-P53 dependent signaling pathway and demethylation of P16(INK4A)

The DNA methylation inhibitor 5-Aza-2'-deoxycytidine (5-Aza-CdR) has increasingly attracted worldwide attention for its antineoplastic potential. The cytotoxitic mechanisms, however, especially, the relative contribution of silenced genes reactivation by demethylation and enzyme-DNA adduct formation to the efficacy of 5-Aza-CdR is still a crucial unresolved question. In this investigation, we demonstrated that 5-Aza-CdR treatment resulted in growth suppression in a concentration and time-dependent manner and G2 phrase arrest - hallmarks of a DNA damage response in gastric cancer AGS cells. Formation of DNA double-strand breaks, as monitored by comet assay was examined in an ATM (ataxia-telangiectasia mutated)-dependent manner based on the fact that PI3K inhibitor Wortmannin abolished the action of cytotoxicity of 5-Aza-CdR. Upon treatment with 5-Aza-CdR, ATM activation was clearly associated with P53 phosphorylation at Ser(15), which was directly responsible for 5-Aza-CdR modified P21(Waf1/Cip1) expression. Further exploration revealed that demethylation of P16(INK4A) correlated with the strikingly down-regulated expressions of DNA methyltransferase 3A as well as 3B was, at least in part, attributed to the cytotoxicity of 5-Aza-CdR in AGS cells. Conclusively, these results greatly enhance our understanding of the mechanisms of cytotoxicity of 5-Aza-CdR and strongly provide the preclinical rationale for an assessment of 5-Aza-CdR to ameliorate patient outcome with gastric cancer.

The role of DNA methyltransferase 3b in esophageal squamous cell carcinoma

BACKGROUND

The identification of potential tumor markers can improve therapeutic planning and patient management. The objective of this study was to highlight the role of DNA methyltransferase 3b (DNMT3b) in esophageal squamous cell carcinoma (SCC).

METHODS

One hundred seventy-three esophageal SCC samples were analyzed using immunohistochemical staining to correlate the expression of DNMT3b with clinical outcome. Furthermore, a human esophageal SCC cell line, CE81T, was selected for cellular and animal experiments to investigate changes in tumor behavior and treatment response after the manipulation of DNMT3b expression.

RESULTS

The incidence of nuclear DNMT3b immunoreactivity in esophageal cancer specimens was significantly higher than in nonmalignant epithelium, and this incidence was linked positively to developing distant metastasis (56% in localized disease vs 80% in distant metastasis; P = .002). Furthermore, increased expression of DNMT3b was linked significantly to lower treatment response rates (P = .002) and reduced survival rates (P = .000). Inhibition of DNMT3b expression resulted in slower cellular proliferation, increased cell death, a less invasive capacity, and less epithelial-mesenchymal-transition changes. Moreover, DNMT3b silencing vectors sensitized esophageal cancer cells to irradiation and cisplatin treatment. The current results also indicated that constitutional activation of signal transducer and activator of transcription 3 (STAT3) signaling associated with inhibited expression of suppressor of cytokine signaling 3 (SOCS3) may be the mechanism underlying more aggressive tumor growth in DNMT3b-positive esophageal cancer.

CONCLUSIONS

DNMT3b was linked significantly to a poor prognosis for patients with esophageal cancer. Moreover, the current results indicated that targeting this enzyme may be a promising strategy for treating esophageal cancer, as evidenced by inhibited aggressive tumor behavior and treatment resistance.

Zebularine inhibits the growth of HeLa cervical cancer cells via cell cycle arrest and caspase-dependent apoptosis

Zebularine (Zeb) as a DNA methyltrasferase (DNMT) inhibitor has various cellular effects such as cell growth inhibition and apoptosis. In the present study, we evaluated the effects of Zeb on the growth and death of HeLa cervical cancer cells. Zeb inhibited the growth of HeLa cells with an IC(50) of approximately 130 μM at 72 h in a dose-dependent manner. DNA flow cytometric analysis indicated that Zeb induced an S phase arrest of the cell cycle, which was accompanied by the increased levels of cdk2 and cyclin A proteins. This agent also induced apoptosis, which was accompanied by the loss of mitochondrial membrane potential (Ψ(m)), PARP-1 cleavage and the activation of caspase-3, -8 and -9. All of the tested caspase inhibitors significantly rescued some cells from Zeb-induced HeLa cell death. In relation to reactive oxygen species (ROS) and glutathione (GSH) levels, O (2) (•-) level was significantly increased in 100 μM Zeb-treated HeLa cells and caspase inhibitors reduced O (2) (•-) level in these cells. Zeb induced GSH depletion in HeLa cells, which was attenuated by caspase inhibitors. In conclusion, this is the first report that Zeb inhibited the growth of HeLa cells via cell cycle arrest and apoptosis.

Constitutive activation of STAT3 is predictive of poor prognosis in human gastric cancer

Abnormalities in signal transducer and activator of transcription (STAT) signaling, especially STAT3 and STAT5, are involved in the oncogenesis of several human cancers, including gastric cancer (GC). However, the downstream targets of STAT3 and STAT5 are not fully identified, and the precise roles and the prognostic value of STAT3 and STAT5 in GC have not been fully characterized. In this study, we used ChIP-on-chip to identify STAT3 and STAT5 target genes on a whole genome scale in AGS cells, a human GC cell line. A total of 2,514 and 1,314 genes were identified as STAT3 and STAT5 target genes, which were mainly related to cell growth, metabolism, differentiation, adhesion, immune response, and stress response. Furthermore, we depleted STAT3 and STAT5 with a small interfering RNA, respectively. Our results demonstrate that STAT3, but not STAT5, is involved in GC cell growth and cell cycle progression through regulation of gene expression, such as Bcl-2, p16(ink4a) and p21(waf1/cip1). Moreover, expression of pSTAT3(Tyr705) correlates with TNM stage, differentiation and survival, and is a significant prognostic factor in GC. Therefore, our findings provide novel evidence that STAT3 may be a potential therapeutic target for GC treatment and pSTAT3(Tyr705) expression can predict prognosis in GC.

A46, a benzothiophene-derived compound, suppresses Jak2-mediated pathologic cell growth

Hyperkinetic Jak2 tyrosine kinase signaling has been implicated in several hematological disorders, including myeloproliferative neoplasms. Effective Jak2 inhibitors can have significant therapeutic potential. Here, using structure-based virtual screening, we identified a benzothiophene-derived Jak2 inhibitor named A46. We hypothesized that this compound would inhibit Jak2-V617F-mediated pathologic cell growth. To test this, A46 was analyzed for its ability to inhibit recombinant Jak2 protein catalysis; suppress Jak2-mediated pathogenic cell growth in vitro; inhibit the aberrant ex vivo growth of Jak2-V617F-expressing primary human bone marrow cells; and inhibit Jak2-mediated pathogenesis in vivo. To this end, we found that A46 selectively inhibited Jak2-V617F protein when compared to wild-type Jak2 protein. The drug also selectively inhibited the proliferation of Jak2-V617F-expressing cells in both a time- and dose-dependent manner, and this correlated with decreased Jak2 and signal transducers and activators of transcription 5 phosphorylation within treated cells. The Jak2-V617F cell growth inhibition correlated with an induction of cell cycle arrest and promotion of apoptosis. A46 also inhibited the pathologic growth of primary Jak2-V617F-expressing bone marrow cells ex vivo. Lastly, using a mouse model of Jak2-V617F-mediated myeloproliferative neoplasia. A46 significantly reduced the splenomegaly and megakaryocytic hyperplasia in the spleens of treated mice and the levels of interleukin-6 in the plasma. Collectively, our data demonstrate that the benzothiophene-based compound, A46, suppresses Jak2-mediated pathogenesis, thereby making it a potential candidate drug against Jak2-mediated disorders.

Trichostatin A, a histone deacetylase inhibitor, suppresses JAK2/STAT3 signaling via inducing the promoter-associated histone acetylation of SOCS1 and SOCS3 in human colorectal cancer cells

Aberrant janus kinase/signal transducers and activators of transcription (JAK/STAT) signaling is involved in the oncogenesis of several cancers. Suppressors of cytokine signaling (SOCS) genes and SH2-containing protein tyrosine phosphatase 1 (SHP1) proteins, which are negative regulators of JAK/STAT signaling, have been reported to have tumor suppressor functions. However, in colorectal cancer (CRC) cells, the mechanisms that regulate SOCS and SHP1 genes, and the cause of abnormalities in the JAK/STAT signaling pathway, remain largely unknown. The present study shows that trichostatin A (TSA), a histone deacetylase (HDAC) inhibitor, leads to the hyperacetylation of histones associated with the SOCS1 and SOCS3 promoters, but not the SHP1 promoter in CRC cells. This indicates that histone modifications are involved in the regulation of SOCS1 and SOCS3. Moreover, upregulation of SOCS1 and SOCS3 expression was achieved using TSA, which also significantly downregulated JAK2/STAT3 signaling in CRC cells. We also demonstrate that TSA suppresses the growth of CRC cells, and induces G1 cell cycle arrest and apoptosis through the regulation of downstream targets of JAK2/STAT3 signaling, including Bcl-2, survivin and p16(ink4a) . Therefore, our data demonstrate that TSA may induce SOCS1 and SOCS3 expression by inducing histone modifications and consequently inhibits JAK2/STAT3 signaling in CRC cells. These results also establish a mechanistic link between the inhibition of JAK2/STAT3 signaling and the anticancer action of TSA in CRC cells.

Expression of phosphorylated Stat5 predicts expression of cyclin D1 and correlates with poor prognosis of colonic adenocarcinoma

PURPOSE

Constitutive activation of signal transducer and activator of transcription-5 (Stat5) was recently found to be associated with tumor progression through stimulating cell proliferation and preventing apoptosis. However, it is not clear how activated Stat5 is expressed in colon cancer. We aimed to investigate the correlation between phosphorylated Stat5 (p-Stat5) expression and cell cycle regulators (cyclin D1) expression in colonic adenocarcinoma and the relationship between expression of these two proteins and various clinicopathological parameters, including overall survival.

METHODS

P-Stat5 and cyclin D1 expression were determined by immunohistochemical staining from 169 cases of resected colonic adenocarcinoma specimens.

RESULTS

P-Stat5 expression correlated with cyclin D1 expression (r = 0.250, P = 0.001). P-Stat5-positive staining was associated with the depth of tumor invasion (P = 0.002). Univariate survival analysis showed that lymph node metastasis, distant metastasis, TNM stage (all P < 0.0001), T stage (P = 0.024), p-Stat5-positive expression (P = 0.002), and cyclin D1-positive expression (P = 0.039) were associated with shorter survival in patients with colonic adenocarcinoma. Multivariate survival analysis showed that only distant metastasis (P < 0.001; hazard ratio [HR] = 4.96), TNM stage (P < 0.001; HR = 9.80), and p-Stat5 overexpression (P = 0.020; HR = 1.84) were independent predictors of poor prognosis.

CONCLUSIONS

Our findings provide the first evidence that p-Stat5 may play an important role in cyclin D1 overexpression and contribute to colonic adenocarcinoma progression.