Methylation of the p73 gene in patients with myelodysplastic syndromes: correlations with apoptosis and prognosis

Thymoquinone Is a Multitarget Single Epidrug That Inhibits the UHRF1 Protein Complex

Silencing of tumor suppressor genes (TSGs) through epigenetic mechanisms, mainly via abnormal promoter DNA methylation, is considered a main mechanism of tumorigenesis. The abnormal DNA methylation profiles are transmitted from the cancer mother cell to the daughter cells through the involvement of a macromolecular complex in which the ubiquitin-like containing plant homeodomain (PHD), and an interesting new gene (RING) finger domains 1 (UHRF1), play the role of conductor. Indeed, UHRF1 interacts with epigenetic writers, such as DNA methyltransferase 1 (DNMT1), histone methyltransferase G9a, erasers like histone deacetylase 1 (HDAC1), and functions as a hub protein. Thus, targeting UHRF1 and/or its partners is a promising strategy for epigenetic cancer therapy. The natural compound thymoquinone (TQ) exhibits anticancer activities by targeting several cellular signaling pathways, including those involving UHRF1. In this review, we highlight TQ as a potential multitarget single epidrug that functions by targeting the UHRF1/DNMT1/HDAC1/G9a complex. We also speculate on the possibility that TQ might specifically target UHRF1, with subsequent regulatory effects on other partners.

A comparison of therapeutic dosages of decitabine in treating myelodysplastic syndrome: a meta-analysis

Decitabine is used to treat myelodysplastic syndrome (MDS). This meta-analysis evaluated the efficacy and safety of different dosing regimens of decitabine in treating intermediate and/or high-risk MDS. Medline, Cochrane, EMBASE, and Google Scholar databases were searched up to October 23, 2015. Randomized controlled trials, prospective, cohort, and case series studies were included. Fifteen studies were included with a total of 1378 patients. The decitabine 100 mg/m²/course dosing regimen had a greater overall response rate than the 60-75 mg/m²/course (51 vs. 25%; P = 0.003). It also had higher complete response rate compared with the 135 mg/m²/course regimen (24.2 vs.13.7%; P = 0.016). The three dosing regimens were similar with respect to bone marrow complete response and partial response and hematologic improvement (P values > 0.05). Decitabine 135 mg/m²/course regimen had similar hematologic improvement as best supportive care (P = 0.066). The incidence of neutropenia, thrombocytopenia, infections, and anemia was similar across treatment groups (range, 31 to 38%; P values ≥ 0.899). The 100 mg/m²/course decitabine regimen showed benefit with respect to overall response rate compared with the 60-75 mg/m²/course regimen, as well as greater improvement in complete response rate compared with the 135 mg/m²/course regimen. All three dosing regimens had similar frequency of adverse events.

PLK2 phosphorylates and inhibits enriched TAp73 in human osteosarcoma cells

TAp73, a member of the p53 tumor suppressor family, can substitute for p53 function, especially in p53‐null and p53‐mutant cells. However, TAp73 enrichment and phosphorylation change its transcriptional activity. Previously, we found that the antitumor function of TAp73 was reactivated by dephosphorylation. Polo‐like kinase 2 (PLK2) plays an important role in bone development. Using a biological information database and phosphorylation prediction software, we hypothesized that PLK2 phosphorylates TAp73 and inhibits TAp73 function in osteosarcomas. Actually,we determined that PLK2 physically binds to and phosphorylates TAp73 when TAp73 protein abundance is up‐regulated by cisplatin. PLK2‐phosphorylated TAp73 at residue Ser48 within the TA domain; phosphorylation of TAp73 was abolished by mutating this residue. Moreover, PLK2 inhibition combined with cisplatin treatment in osteosarcoma Saos2 cells up‐regulated p21 and puma mRNA expression to a greater extent than cisplatin treatment alone. Inhibiting PLK2 in TAp73‐enriched Saos2 cells resulted in inhibited cell proliferation, increased apoptosis, G1 phase arrest, and decreased cell invasion. However, these changes did not occur in TAp73 knockdown Saos2 cells. In conclusion, these findings reveal a novel PLK2 function in the phosphorylation of TAp73, which prevents TAp73 activity in osteosarcoma cells. Thereby, this research provides an insight into the clinical treatment of malignant tumors overexpressing TAp73.

Effect of combined 5-aza-2'deoxycytidine and cisplatin treatment on the P15 lung adenocarcinoma cell line

Aberrant promoter hypermethylation resulting in the epigenetic silencing of apoptosis-associated genes is a key process in the chemotherapeutic treatment of cancer. The nucleoside analog, 5-aza-2'deoxycytidine (DAC), inhibits the activity of DNA methyltransferase enzymes and is able to restore the expression levels of genes that have been silenced by aberrant DNA methylation. The aim of the present study was to investigate the effect of combined treatment with DAC and cisplatin (CDDP) on the lung adenocarcinoma cell line, P15. Growth inhibition was examined using a clone formation assay and growth inhibitory activities by cell counting during treatment with DAC alone, CDDP alone or DAC followed by CDDP. In addition, changes in the mRNA expression levels of various apoptosis-associated genes following treatment with increasing concentrations of DAC were determined using reverse transcription-polymerase chain reaction. Furthermore, terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) analysis was used to detect the number of apoptotic P15 tumor cells following treatment with DAC and/or CDDP. The results indicated that DAC treatment alone restored the mRNA expression levels of p73, p16^INK4a , B-cell lymphoma (Bcl)-2-associated agonist of cell death and Bcl-2-associated X protein. In addition, combined therapy with DAC and CDDP was found to significantly suppress the growth of P15 tumor cells compared with DAC or CDDP treatment alone. In conclusion, DAC may enhance the chemosensitivity of the P15 cell line to treatment with CDDP.

Comparison between decitabine and azacitidine for the treatment of myelodysplastic syndrome: a meta-analysis with 1,392 participants

The hypomethylating agents decitabine and azacitidine have been found to improve the outcome of patients with myelodysplastic syndrome (MDS); however, the clinical choice between them is controversial. Therefore, this meta-analysis was performed to compare the efficacy, toxicity, and survival advantage of decitabine and azacitidine in patients with MDS. Eleven trials with a total of 1392 patients with MDS (decitabine, n = 768; azacitidine, n = 624) were included for analysis. The pooled estimates of partial response, hematologic improvement, and overall response rates for azacitidine were significantly higher than for decitabine. There were no differences between these 2 drugs regarding complete response, red blood cell transfusion-independent rates, and grade 3 or 4 hematologic toxicity. When compared with best supportive care, azacitidine significantly improved overall survival (hazard ratio [HR], 0.69; 95% CI, 0.54-0.87) and time to acute myeloid leukemia transformation (HR, 0.51; 95% CI, 0.35-0.74). But these benefits were not found with decitabine. Among patients with higher risk (International Prognostic Scoring System value of 3) or older than 75 years, treatment with azacitidine was a favorable factor, whereas decitabine showed no advantage. Therefore, with higher overall response rates and better survival benefits, azacitidine is recommended as the first-line hypomethylating agent for MDS, especially in elderly patients or those with high risk.

Pathway landscapes and epigenetic regulation in breast cancer and melanoma cell lines

BACKGROUND

Epigenetic variation is a main regulation mechanism of gene expression in various cancer histotypes, and due to its reversibility, the potential impact in therapy can be very relevant.

METHODS

Based on a selected pair, breast cancer (BC) and melanoma, we conducted inference analysis in parallel on a few cell lines (MCF-7 for BC and A375 for melanoma). Starting from differential expression after treatment with a demethylating agent, the 5-Aza-2'-deoxycytidine (DAC), we provided pathway enrichment analysis and gene regulatory maps with cross-linked microRNAs and transcription factors.

RESULTS

Several oncogenic signaling pathways altered upon DAC treatment were detected with significant enrichment. We represented the association between these cancers by depicting the landscape of common and specific variation affecting them.

Downregulation of p21 in myelodysplastic syndrome is associated with p73 promoter hypermethylation and indicates poor prognosis

OBJECTIVES

p21 Can both promote and inhibit tumorigenic processes. We explored the role of p21 in myelodysplastic syndrome (MDS).

METHODS

In this study, we analyzed p21 expression and p73 methylation in 88 patients with de novo MDS.

RESULTS

We found decreased expression of the p21 gene in higher-risk MDS compared with lower-risk groups or healthy controls (P < .05). Patients with p73 methylation had lower p21 than those in the unmethylated group (P < .001). Moreover, there was a significantly positive correlation between p73 and p21 expression in MDS (r = 0.436, P < .001). In vitro assays further confirm the role of p73 methylation in p21 expression. Compared with patients with normal expression levels of p21, patients with lower p21 expression levels experienced much higher rates of transformation to acute myeloid leukemia and lower overall survival both in univariate as well as multivariate analyses.

CONCLUSIONS

Our results suggest p21 expression may serve as a new biomarker to predict clinical outcome in patients with MDS.