Demethylating Agent 5-Aza-2′-Deoxycytidine Enhances Susceptibility of Renal Cell Carcinoma to Paclitaxel

Synergistic Inhibitory Effects of 5-Aza-2'-Deoxycytidine and Cisplatin on Urothelial Carcinoma Growth via Suppressing TGFBI-MAPK Signaling Pathways

This study is to reveal the gene transcriptional alteration, possible molecular mechanism, and pathways involved in the synergy of 5-aza-2'-deoxycytidine (DAC) and CDDP in UC. Two UC cell lines, 5637 and T24, were used in the study. A cDNA microarray was carried out to identify critical genes in the synergistic mechanism of both agents against UC cells. The results showed that several key regulatory genes, such as interleukin 24(IL24), fibroblast growth factor 1(FGF1), and transforming growth factor beta-induced (TGFBI), were identified and may play critical roles in the synergy of DAC and CDDP in UC. Pathway enrichment suggested that many carcinogenesis-related pathways, such as ECM-receptor interaction and MAPK signaling pathways, may participate in the synergy of both agents. Our results suggested that TGF-β1 stimulates the phosphorylation levels of ERK1/2 and p38 via increasing TGFBI expression, TGFBI-MAPK signaling pathway plays an important role in the synergy of DAC and CDDP against UC. Therefore, we revealed the synergistic mechanism of DAC and CDDP in UC, several key regulatory genes play critical roles in the synergy of combined treatment, and TGFBI-MAPK signaling pathway may be an important potential target of these two agents.

Carbon Nanotube- and Asbestos-Induced DNA and RNA Methylation Changes in Bronchial Epithelial Cells

Carbon nanotubes (CNTs) are nanoscale tube-shaped carbon materials used in many industrial areas. Their fiber shape has caused concerns about their toxicity given their structural similarity with asbestos. The aim here was to elucidate the effect of CNTs and asbestos exposure on global DNA and RNA methylation and the methylation of genes associated with cell cycle, inflammation, and DNA damage processes in human lung cells. Human bronchial epithelial cells (16HBE14o-) were exposed for 24 h to 25 and 100 μg/mL CNTs (single-walled CNTs [SWCNTs] and multiwalled CNTs [MWCNTs]) and 2.5 μg/mL asbestos (chrysotile, amosite, and crocidolite). Global DNA and RNA (hydroxy)methylation to cytosines was measured by a validated liquid chromatography tandem-mass spectrometry method. Global RNA methylation to adenines was measured by a colorimetric ELISA-like assay. Gene-specific DNA methylation status at certain cytosine-phosphate-guanine (CpG) sites of cyclin-dependent kinase inhibitor 1A ( CDKN1A), serine/threonine kinase ( ATM), and TNF receptor-associated factor 2 ( TRAF2) were analyzed by using bisulfite pyrosequencing technology. Only MWCNT-exposed cells showed significant global DNA hypomethylation of cytosine and global RNA hypomethylation of adenosine. SWCNT, MWCNT, and amosite exposure decreased DNA methylation of CDKN1A. ATM methylation was affected by chrysotile, SWCNT, and MWCNT. However, SWCNT exposure led to DNA hypermethylation of TRAF2. These findings contribute to further understanding of the effect of CNTs on different carcinogenic pathways.

Targeting DNA Methyltranferases in Urological Tumors

Urological cancers are a heterogeneous group of malignancies accounting for a considerable proportion of cancer-related morbidity and mortality worldwide. Aberrant epigenetic traits, especially altered DNA methylation patterns constitute a hallmark of these tumors. Nonetheless, these alterations are reversible, and several efforts have been carried out to design and test several epigenetic compounds that might reprogram tumor cell phenotype back to a normal state. Indeed, several DNMT inhibitors are currently under evaluation for therapeutic efficacy in clinical trials. This review highlights the critical role of DNA methylation in urological cancers and summarizes the available data on pre-clinical assays and clinical trials with DNMT inhibitors in bladder, kidney, prostate, and testicular germ cell cancers.

Expression and proliferation-promoting role of lymphoid enhancer-binding factor 1 in human clear cell renal carcinoma

Lymphoid enhancer-binding factor 1 (LEF1) has been regarded as an important gene for carcinogenesis in many malignancies, however, the role of LEF1 in the progression of human renal cell carcinoma (RCC) has not been well studied. In this study, we investigated the expression of LEF1 in human RCC and the effect on proliferative ability of RCC cells. RCC samples from 138 patients who underwent radical nephrectomy were used in this study, the expression of LEF1 protein was determined by immunohistochemistry and Western blot, mRNA expression was analyzed by RT-PCR and real-time PCR. To investigate the effect of LEF1 on the proliferation of RCC cells, a LEF1 vector was transfected into RCC cells and LEF1 expression was also decreased by using siRNA. Proliferative ability of RCC cells was examined by WST-1 assay and a xenograft study with BALB/C nude mice. Our results indicated that LEF1 expression was significantly increased in stage III, IV and grade 3 RCC than in normal kidney, however, decreased LEF1 expression was found in low-stage and grade RCC compared to that in normal kidney, the expression of LEF1 was correlated to tumor stages, histologic grade, and tumor sizes in RCC. The effect of LEF1 on the proliferation in RCC was also analyzed, our results suggested that RCC cells expressing high levels of LEF1 had significantly increased proliferative ability compared to control cell lines, in contrast, RCC cells with a low LEF1 expression had lower proliferative ability. Moreover, LEF1 promoted proliferation of RCC cells depending on suppressing G2/M cell-cycle arrest. Our study demonstrated that the expression of LEF1 is associated with the progression of RCC and that LEF1 maybe involved in the development of RCC, these suggested LEF1 play a key role and might serve as a therapeutic target in treating advanced RCC.

Gene expression profiling of the synergy of 5-aza-2'-deoxycytidine and paclitaxel against renal cell carcinoma

Background

Renal cell carcinoma (RCC) is one of the most common kidney cancers and is highly resistant to chemotherapy. We previously demonstrated that 5-aza-2^′-deoxycytidine (DAC) could significantly increase the susceptibility of renal cell carcinoma (RCC) cells to paclitaxel (PTX) treatment in vitro, and showed the synergy of DAC and PTX against RCC. The purpose of this study is to investigated the gene transcriptional alteration and investigate possible molecular mechanism and pathways implicated in the synergy of DAC and PTX against RCC.

Methods

cDNA microarray was performed and coupled with real-time PCR to identify critical genes in the synergistic mechanism of both agents against RCC cells. Various patterns of gene expression were observed by cluster analysis. IPA software was used to analyze possible biological pathways and to explore the inter-relationships between interesting network genes.

Results

We found that lymphoid enhancer-binding factor 1 (LEF1), transforming growth factor β-induced (TGFBI), C-X-C motif ligand 5 (CXCL5) and myelocytomatosis viral related oncogene (c-myc) may play a pivotal role in the synergy of DAC and PTX. The PI3K/Akt pathway and other pathways associated with cyclins, DNA replication and cell cycle/mitotic regulation were also associated with the synergy of DAC and PTX against RCC.

Conclusion

The activation of PI3K/Akt-LEF1/β-catenin pathway could be suppressed synergistically by two agents and that PI3K/Akt-LEF1/β-catenin pathway is participated in the synergy of two agents.

5-aza-2'-deoxycytidine enhances susceptibility of renal cell carcinoma to paclitaxel by decreasing LEF1/phospho-β-catenin expression

We investigated the molecular mechanisms by which 5-aza-2'-deoxycytidine (DAC) and paclitaxel (PTX) use lymphoid enhancer-binding factor 1 (LEF1) and the Wnt/β-catenin pathway to synergistically interact against renal cell carcinoma (RCC). LEF1 expression was examined by real-time PCR and immunohistochemistry. The regulation of LEF1/β-catenin protein expression by DAC and/or PTX was examined by Western blot and immunoprecipitation. To analyze the effect of LEF1 on the proliferative ability of RCC cells and the synergy of DAC and PTX against RCC cells, an expression vector containing the full-length cDNA for LEF1 was transfected into RCC cells, and LEF1 expression was also decreased using siRNA technology. Our results confirmed that DAC and PTX synergistically decreased the expression of LEF1 in vivo and in vitro. Moreover, treatment of RCC cell lines with the combination of DAC and PTX caused a synergistic decrease in LEF1/phospho-β-catenin. Our study also demonstrated a negative correlation between LEF1 expression and the proliferative ability of RCC cells. Although interfering with LEF1 expression did not abolish the synergy between the two agents, RCC cells expressing high levels of LEF1 displayed an increased synergistic effect compared with RCC cells expressing low levels of LEF1. This study suggests that LEF1 can enhance the proliferation of RCC cells and that the LEF1/β-catenin complex plays an important role in the synergy of DAC and PTX against RCC cells. Moreover, the synergy between DAC and PTX may be more effective in RCC cells expressing high levels of LEF1.

Silibinin inhibits the invasion and migration of renal carcinoma 786-O cells in vitro, inhibits the growth of xenografts in vivo and enhances chemosensitivity to 5-fluorouracil and paclitaxel

Silibinin is a flavonoid antioxidant that is widely used for its anti-hepatotoxic properties. It exerts a dose-dependent inhibition on the invasion and migration of 786-O renal cell carcinoma (RCC) cells in the absence of cytotoxicity. 786-O cells were treated with silibinin at various concentrations, up to 50 µM, for a defined period and then subjected to gelatin zymography, casein zymography, and Western blot to investigate the impacts of silibinin on metalloproteinase (MMP) -2, -9, urokinase plasminogen activator (u-PA), and MAPK pathway signaling proteins, respectively. The results showed that silibinin decreased MMP-2, MMP-9, u-PA, p-p38, and p-Erk1/2 expressions in a concentration-dependent manner. The reduced expressions of MMP-2 and u-PA, as well as inhibition of cell invasion were obtained in the cultures pre-treated with PD98059 (Erk1/2 inhibitor) and SB203580 (p38 inhibitor). An in vivo anti-tumor study with a nude mice xenograft model by a subcutaneous inoculation of 786-O cells demonstrated small solid tumors after eight days following cell inoculation. There was a 70.1% reduction in tumor volume and 69.7% reduction in tumor weight by silibinin feeding on day 44, compared to those of controls. Moreover, combination treatment with silibinin and 5-fluorouracil, paclitaxel, vinblastine, or RAD-001 enhanced the chemosensitivity of 5-fluorouracil and paclitaxel. In conclusion, silibinin inhibits the invasion and migration of 786-O cells in vitro, inhibits the growth of xenografts in vivo, and enhances chemosensitivity to 5-fluorouracil and paclitaxel. © 2011 Wiley-Liss, Inc.

Additive effects of 5-aza-2'-deoxycytidine and irradiation on clonogenic survival of human medulloblastoma cell lines

BACKGROUND AND PURPOSE

In recent years, epigenetic modulators were introduced into tumor therapy. Here, the authors investigated the antitumor effect of 5-aza-2'-deoxycytidine-(5-aza-dC-)induced demethylation combined with irradiation on human medulloblastoma (MB) cells, which form the most common malignant brain tumor in children.

MATERIAL AND METHODS

Three MB cell lines were treated with 5-aza-dC in a low-dose (0.1 microM, 6 days) or high-dose (3/5 microM, 3 days) setting and irradiated with 2, 4, 6, or 8 Gy single dose on an X-ray unit. Methylation status and mRNA expression of three candidate genes were analyzed by methylation-specific PCR (polymerase chain reaction) and quantitative real-time RT-PCR. Cell survival and mortality were determined by trypan blue exclusion test. Proliferation was analyzed by BrdU incorporation assay, and long-term cell survival was assessed by clonogenic assay.

RESULTS

5-aza-dC treatment resulted in partial promoter demethylation and increased expression of hypermethylated candidate genes. A significant decrease of vital cell count, proliferation inhibition and increase of mortality was observed in 5-aza-dC-treated as well as in irradiated MB cells, whereby combination of both treatments led to additive effects. Although high-dose 5-aza-dC treatment was more effective in terms of demethylation, clonogenic assay revealed no differences between high- and low-dose settings indicating no relevance of 5-aza-dC-induced demethylation for decreased cell survival. MB cells pretreated with 5-aza-dC showed significantly lower plating efficiencies than untreated cells at all irradiation doses investigated. Analysis of surviving curves in irradiated MB cells, however, revealed no significant differences of alpha-, beta-values and 2-Gy surviving fraction with or without 5-aza-dC treatment.

CONCLUSION

5-aza-dC did not enhance radiation sensitivity of MB cells but significantly reduced the clonogenicity versus irradiation alone, which merits further investigation of its potential clinical application in MB possibly by combination with other chemotherapeutic agents.

5-Aza-2'-deoxycytidine reactivates expression of RUNX3 by deletion of DNA methyltransferases leading to caspase independent apoptosis in colorectal cancer Lovo cells

The DNA methylation inhibitor 5-Aza-2'-deoxycytidine (5-Aza-CdR) has therapeutic value for the treatment of cancer. However, the mechanism by which 5-Aza-CdR induces antineoplastic activity is an important unresolved question. In this study, we found that 5-Aza-CdR at limited concentrations induced inhibition of colorectal cancer Lovo cell proliferation as well as increased apoptosis caused by DNA damage, which was independent of the caspase pathway. Regarding the mechanisms, for the first time, we examined that cytotoxicity against Lovo cells was regulated via down-regulation of DNA methyltransferase 3a, DNMT3b and then reactivated the expression of RUNX3. We therefore conclude that RUNX3 is a relevant target for methyltransferases dependent effects of 5-Aza-CdR on colorectal cancer Lovo cells.

Genetics and epigenetics of renal cell cancer

Renal cell carcinoma (RCC) is not a single disease, but comprises a group of tumors of renal epithelial origin, each with a different histology, displaying a different clinical course and caused by different genetic alterations. Since cure rates are inversely associated with stage and response to the available treatment regimes is limited to a subgroup of patients, diagnostic methods facilitating early detection and new therapeutic modalities are necessary. Increased knowledge of the underlying pathophysiology of RCC has resulted in the identification of genetic alterations involved in renal cell cancer carcinogenesis. Promising agents to target these pathways, especially the angiogenesis pathway, are being developed, some of which are already standard of care. In addition to genetics, knowledge on epigenetics in the process of renal tumorigenesis has been significantly increased in the last decades. Epigenetics will play an increasing role in the development of new therapeutic modalities and may deliver new prognostic and early diagnostic markers. In this review we discuss the background of RCC and the clinical applications of RCC genetics and epigenetics.