Everolimus combined with 5-aza-2-deoxycytidine generated potent anti-tumor effects on ovarian clear cell cancer stem-like/spheroid cells by inhibiting the COL6A3-AKT-mTOR pathway

Ovarian clear cell cancer stem-like/spheroid cells (OCCCSCs) were associated with recurrence, metastasis, and chemoresistance in ovarian clear cell carcinoma (OCCC). We evaluated the anti-tumor effects of 5-aza-2-deoxycytidine (5-aza-dC) combined with everolimus (RAD001) on human OCCC. We investigated parental OCCCSCs and paclitaxel-resistant cell lines derived from OCCCSCs in vitro and in vivo. A Western blot analysis showed that the 5-aza-dC and RAD001 combination therapy was associated with the COL6A3-AKT-mTOR pathway. The OCCCSCs expressed high levels of stemness markers: CD117, ALDH1, NANOG, OCT4, and CD133. The 5-aza-dC and RAD001 combination inhibited proliferation and survival with up to 100-fold more potency in OCCCSCs compared to OCCC cells. This combination showed significant anti-tumor activity; it preferentially diminished OCCCSC stemness levels and spheroid numbers in vitro. Limiting dilution assays showed that OCCCSCs possessed tumor-initiating capacity. The 5-aza-dC and RAD001 combination significantly enhanced the inhibition of tumor growth compared to the 5-aza-dC or RAD001 alone. OCCCSCs showed higher expression levels of COL6A3, phospho-AKT, phospho-mTOR, and phospho-Rictor compared to OCCCs. Silencing COL6A3 or abolishing the phospho-AKT-mTOR-Rictor pathway with 5-aza-dC and RAD001 treatment further enhanced OCCCSC apoptosis and reduced OCCCSC stemness. In conclusion, 5-aza-dC combined with RAD001 effectively controlled OCCC and OCCCSC growth by inhibiting the COL6A3-AKT-mTOR pathway.

DNA methylation determines the regulation of pregnane X receptor on CYP3A4 expression

The expression and activity of CYP3A4 vary among individuals. With the development of epigenetics, it is now possible to elucidate interindividual differences in drug-metabolizing enzymes. Here, we aimed to explore the potential relationship between DNA methylation and CYP3A4 expression. We analyzed the effect of a DNA methylation inhibitor, 5-aza-2-deoxycytidine, on pregnane X receptor (PXR) and CYP3A4 expression in HepG2 cells. In addition, pCpGL-CYP3A4-promoter and pCpGL-CYP3A4-enhancer plus promoter plasmids were constructed, methylated, and transfected. We found that treatment with 5-aza-2-deoxycytidine significantly increased the expression of PXR and CYP3A4 in a concentration- and time-dependent manner. In addition, CYP3A4 expression was significantly enhanced by overexpressing PXR via transfection of pSG5-PXR plasmids. Methylation of CYP3A4 enhancer inhibited CYP3A4 transcriptional activity mediated through PXR and inhibited the binding of PXR and CYP3A4 promoter. We also observed that when the promoter and enhancer of CYP3A4 were methylated, CYP3A4 expression did not increase after treatment with rifampicin. In conclusion, the investigation demonstrates that DNA methylation of CYP3A4 enhancer significantly inhibits CYP3A4 expression, mediated through PXR, which is not influenced by rifampicin.

5-Aza-2-deoxycytidine Enhances the Sensitivity of 5-Fluorouracil by Demethylation of the Thymidine Phosphorylase Promoter

BACKGROUND/AIM

5-Aza-2-deoxycytidine (5-Aza-CdR) enhances the sensitivity to 5-fluorouracil (5-FU), but the molecular mechanism is not fully understood. The aim of this study was to investigate the molecular mechanism that enhances the sensitivity to 5-FU treated with 5-Aza-CdR via thymidine phosphorylase (TP).

MATERIALS AND METHODS

The sensitivity to drugs was determined on several cancer cell lines by the MTT assay. Protein and mRNA levels were examined by immunoblot and RT-PCR, respectively. Gene silencing, binding of Sp1 to DNA and methylation of DNA was performed by siRNA, ChIP assay and sodium bisulfate genomic sequencing, respectively.

RESULTS

Sp1-binding sites in the TP promoter were methylated in epidermoid carcinoma. 5-Aza-CdR demethylated Sp1-binding sites and enhanced sensitivity to 5-FU.

CONCLUSION

Demethylation of Sp1-binding sites by 5-Aza-CdR was a key factor enhancing 5-FU sensitivity, which may enable more effective treatments for cancer patients with the combination of 5-Aza-CdR and 5-FU.

Epigenetic Changes of the Immune System with Role in Tumor Development

Tumor development is closely related to chronic inflammation and to evasion of immune defense mechanisms by neoplastic cells. The mediators of the inflammatory process as well as proteins involved in immune response or immune response evasion can be subject to various epigenetic changes such as methylation, acetylation, or phosphorylation. Some of these, such as cytokine suppressors, are undergoing repression through epigenetic changes, and others such as cytokines or chemokines are undergoing activation through epigenetic changes, both modifications having as a result tumor progression. The activating changes can affect the receptor molecules involved in immune response and these promote inflammation and subsequently tumor development while the inactivating changes seem to be related to the tumor regression process. The proteins involved in antigen presentation, and, therefore in immune response escape, such as classical HLA proteins and related APM (antigen presentation machinery) with their epigenetic changes contribute to the tumor development process, either to tumor progression or regression, depending on the immune effector cells that are in play.

Everolimus following 5-aza-2-deoxycytidine is a promising therapy in paclitaxel-resistant clear cell carcinoma of the ovary

Our previous study showed that 5-aza-2-deoxycytidine (5-aza-dC) could inhibit tumor growth by enhancing the susceptibility of ovarian clear cell carcinoma (OCCC) to paclitaxel through decreasing AKT/mTOR expressions. The objective of the study is to evaluate the antitumor efficacy of everolimus (RAD001) and 5-aza-2-deoxycytidine (5-aza-dC) by targeting AKT/mTOR and EZH2 in OCCC. Paclitaxel-sensitive and resistant OCCC cell lines were established. In vitro proliferative and apoptotic assays and flow cytometry were performed. The expressions of EZH2, PIK3IP1, phospho-AKT, phospho-mTOR and phospho-Rictor in the OCCC cell lines were evaluated by Western blotting. In vivo animal experiments with RAD001 and 5-aza-dC were performed. RAD001 alone showed significant in vitro antitumor activity and inhibited in vivo tumor growth in paclitaxel-sensitive and resistant OCCC cells. In addition, 5-aza-dC enhanced the antitumor effects when combined with paclitaxel or RAD001 in both paclitaxel-sensitive and resistant tumors. Activation of phospho-AKT ser473 and PIK3IP1 was observed in RAD001-treated paclitaxel-sensitive and resistant OCCC cells. In contrast, inhibition of phospho-AKT ser473 and EZH2 was observed with RAD001 following 5-aza-dC treatment of paclitaxel-sensitive and resistant OCCC cells. Furthermore, RAD001 following 5-aza-dC enhanced apoptosis of paclitaxel-sensitive and resistant OCCC cells. RAD001 following 5-aza-dC may be a promising treatment strategy for the treatment of both chemo-sensitive and resistant OCCC. Further clinical studies are warranted.

Inhibition of DNA and Histone Methylation by 5-Aza-2'-Deoxycytidine (Decitabine) and 3-Deazaneplanocin-A on Antineoplastic Action and Gene Expression in Myeloid Leukemic Cells

Epigenetic alterations play an important role in the development of acute myeloid leukemia (AML) by silencing of genes that suppress leukemogenesis and differentiation. One of the key epigenetic changes in AML is gene silencing by DNA methylation. The importance of this alteration is illustrated by the induction of remissions in AML by 5-aza-2′-deoxycytidine (5-AZA-CdR, decitabine), a potent inhibitor of DNA methylation. However, most patients induced into remission by 5-AZA-CdR will relapse, suggesting that a second agent should be sought to increase the efficacy of this epigenetic therapy. An interesting candidate for this purpose is 3-deazaneplanocin A (DZNep). This analog inhibits EZH2, a histone methyltransferase that trimethylates lysine 27 histone H3 (H3K27me3), a marker for gene silencing. This second epigenetic silencing mechanism also plays an important role in leukemogenesis as shown in preclinical studies where DZNep exhibits potent inhibition of colony formation by AML cells. We reported previously that 5-AZA-CdR in combination with DZNep exhibits a synergistic antineoplastic action against human HL-60 AML cells and the synergistic activation of several tumor suppressor genes. In this report, we showed that this combination also induced a synergistic activation of apoptosis in HL-60 cells. The synergistic antineoplastic action of 5-AZA-CdR plus DZNep was also observed on a second human myeloid leukemia cell line, AML-3. In addition, 5-AZA-CdR in combination with the specific inhibitors of EZH2, GSK-126, or GSK-343, also exhibited a synergistic antineoplastic action on both HL-60 and AML-3. The combined action of 5-AZA-CdR and DZNep on global gene expression in HL-60 cells was investigated in greater depth using RNA sequencing analysis. We observed that this combination of epigenetic agents exhibited a synergistic activation of hundreds of genes. The synergistic activation of so many genes that suppress malignancy by 5-AZA-CdR plus DZNep suggests that epigenetic gene silencing by DNA and histone methylation plays a major role in leukemogenesis. Targeting DNA and histone methylation is a promising approach that merits clinical investigation for the treatment of AML.

Genome-wide methylation analysis demonstrates that 5-aza-2-deoxycytidine treatment does not cause random DNA demethylation in fragile X syndrome cells

Background

Fragile X syndrome (FXS) is caused by CGG expansion over 200 repeats at the 5′ UTR of the FMR1 gene and subsequent DNA methylation of both the expanded sequence and the CpGs of the promoter region. This epigenetic change causes transcriptional silencing of the gene. We have previously demonstrated that 5-aza-2-deoxycytidine (5-azadC) treatment of FXS lymphoblastoid cell lines reactivates the FMR1 gene, concomitant with CpG sites demethylation, increased acetylation of histones H3 and H4 and methylation of lysine 4 on histone 3.

Results

In order to check the specificity of the 5-azadC-induced DNA demethylation, now we performed bisulphite sequencing of the entire methylation boundary upstream the FMR1 promoter region, which is preserved in control wild-type cells. We did not observe any modification of the methylation boundary after treatment. Furthermore, methylation analysis by MS-MLPA of PWS/AS and BWS/SRS loci demonstrated that 5-azadC treatment has no demethylating effect on these regions. Genome-wide methylation analysis through Infinium 450K (Illumina) showed no significant enrichment of specific GO terms in differentially methylated regions after 5-azadC treatment. We also observed that reactivation of FMR1 transcription lasts up to a month after a 7-day treatment and that maximum levels of transcription are reached at 10–15 days after last administration of 5-azadC.

Conclusions

Taken together, these data demonstrate that the demethylating effect of 5-azadC on genomic DNA is not random, but rather restricted to specific regions, if not exclusively to the FMR1 promoter. Moreover, we showed that 5-azadC has a long-lasting reactivating effect on the mutant FMR1 gene.

Electronic supplementary material

The online version of this article (doi:10.1186/s13072-016-0060-x) contains supplementary material, which is available to authorized users.

Inhibition of DNA methylation enhances HLA-G expression in human mesenchymal stem cells

Mesenchymal stem cells (MSCs) are immunosuppressive multipotent cells under investigation for potential therapeutic applications in regenerative medicine and prevention of graft-versus-host disease. Human leukocyte antigen (HLA)-G contributes to the immunomodulatory properties of MSCs. HLA-G expression in MSCs is very low and diminishes during in vitro expansion. Epigenetic regulation activates HLA-G expression in some cancer cell lines but not in MSCs. In the present study, adipose- and bone marrow-derived MSCs were exposed to the DNA demethylating agent 5-aza-2-deoxycytidine (5-aza-dC) and histone deacetylase inhibitor valproic acid (VPA) and HLA-G mRNA levels assessed using semi-quantitative reverse-transcription PCR. Exposure to 5-aza-dC resulted in HLA-G1 and -G3 upregulation in both early and late passage MSCs. VPA treatment did not induce HLA-G expression in both bone marrow and adipose derived MSCs. Our results provide the first evidence that HLA-G3 could be expressed in MSCs and that methylation-mediated repression is partly responsible for the observed low levels of HLA-G expression in MSCs. Our findings provide insight that treatment of MSCs with specific epigenetic regulatory modulators may improve their immunoregulatory capability for therapeutic applications.

Epigenetic inactivation of KLF4 is associated with urothelial cancer progression and early recurrence

PURPOSE

KLF4 is a transcription factor with divergent functions in different malignancies. We analyzed KLF4 expression and DNA methylation, and their clinical relevance and biological function in urothelial cancer.

MATERIALS AND METHODS

Immunohistochemistry and Sequenom™ MassARRAY® were done to detect the expression and promoter methylation of KLF4 in urothelial cancer tissues. The association of the recurrence-free survival rate and decreased KLF4 or KLF4 methylation status was analyzed by the Kaplan-Meier method, Cox regression analysis and ROC assay. Lentivirus based KLF4 over expression and dsRNA mediated knockdown were used to detect KLF4 functions in urothelial cancer in vitro and in vivo.

RESULTS

KLF4 was down-regulated in urothelial cancer due to promoter hypermethylation. Each correlated with recurrence-free survival in patients with nonmuscle invasive bladder cancer after transurethral resection of bladder cancer, which potentiates them as valuable predictive biomarkers for early recurrence. Moreover, in and ex vivo experiments showed that KLF4 suppressed urothelial cancer cell growth, migration and invasion inhibited the epithelial-to-mesenchymal transition.

CONCLUSIONS

KLF4 may function as a tumor suppressor gene in urothelial cancer since down-regulation of KLF4 by promoter hypermethylation would promote cancer progression. In addition, decreased expression of KLF4 or its promoter hypermethylation may have predictive value for early recurrence in patients with nonmuscle invasive bladder cancer.

Effects of 5-aza-2-deoxycytidine and trichostatin A on biological behavior in MGC-803 cells

AIM: To explore the effects of 5-aza-2-deoxycytidine (5-Aza-CdR) and trichostatin A (TSA) on biological behavior in MGC-803 Cells.

METHODS: MGC-803 cells were cultured in RPMI 1640 culture medium containing 100 g/L fetal calf serum. The cells in experiment were at logarithmic phase, and the number of viable cells was 95%-98%. The trial consisted of five groups. (1) Blank control group: there was only culture medium and no cells or drugs; (2) Negative control group: there were cells, culture medium and no drugs; (3) 5-Aza-CdR group: 24 h after inoculation, MGC-803 cells were treated with 10.0 μmol/L 5-Aza-CdR; (4) TSA group: 24 h after inoculation, MGC-803 cells were treated with 300 μg/L TSA;. (5) 5-Aza-CdR+TSA group: 24 h after inoculation, MGC-803 cells were treated with 10.0 μmol/L 5-Aza-CdR, and then treated with 300 μg/L TSA after 24 h. After MGC-803 cells were treated with different concentrations of 5-Aza-CdR and TSA for different cultural time, the expression of Runx3 mRNA in different groups for 72 h was detected by RT-PCR, and the cell proliferation in different groups for 24, 48, 72 h was determined using MTT colorimetry.

RESULTS: When MGC-803 cells were treated with 5-Aza-CdR and TSA alone for 72 h, the relative expression of Runx3 mRNA was increased. It was significantly increased in combination group, and compared with 5-Aza-CdR group and TSA group (0.883 ± 0.025 vs 0.760 ± 0.286, 0.735 ± 0.018, both P < 0.05). The cell growth inhibition rate increased with the time prolonging in the same group and there was a positive relationship (r = 0.738, P < 0.05). The cell growth inhibition rate increased more significantly in combination group compared with 5-Aza-CdR group and TSA group in the same time (24 h: 57.3% vs 40.4%, 39.0%; 48 h: 70.0% vs 56.0%, 51.3%; 72 h: 86.3% vs 68.0%, 65.8%, all P < 0.05). There were significant differences between drug group and control group in relative expression of Runx3 mRNA and cell growth inhibition rate (P < 0.05).

CONCLUSION: Compared with 5-Aza-CdR or TSA alone, combination of the two drugs can significantly induce Runx3 mRNA expression and inhibit cell proliferation.