The epigenetic mechanisms underlying chemoresistance in cancer cells resulting from drug-induced reversible senescence are poorly understood. Chemoresistant ESC-like embryonal carcinoma PA1 cells treated with etoposide (ETO) were previously found to undergo prolonged G2 arrest with transient p53-dependent upregulation of opposing fate regulators, p21CIP1 (senescence) and OCT4A (self-renewal). Here we report on the analysis of the DNA methylation state of the distal enhancer (DE) and proximal enhancer (PE) of the Oct4A gene during this dual response. When compared to non–treated controls the methylation level increased from 1.3% to 12.5% and from 3% to 19.4%, in the DE and PE respectively. It included CpG and non-CpG methylation, which was not chaotic but presented two patterns in each enhancer. Discorrelating with methylation of enhancers, the transcription of Oct4A increased, however, a strong expression of the splicing form Oct4B was also induced, along with down-regulation of the Oct4A partners of in the pluripotency/self-renewal network Sox2 and Lin28. WB demonstrated disjoining of the OCT4A protein from the chromatin-bound fraction. In survival clones, methylation of the DE was considerably erased, while some remnant of methylation of the PE was still observed. The alternative splicing for Oct4B was reduced, Oct4A level insignificantly decreased, while the expression of Sox2 and Lin28 recovered, all three became proportionally above the control. These findings indicate the involvement of the transient patterned methylation of the Oct4A enhancers and alternative splicing in the adaptive regulation of cell fate choice during the p53-dependant dual state of reversible senescence in ESC-like cancer stem cells.
CCR2 is the cognate receptor to the chemokine CCL2. CCR2–CCL2 signaling mediates cancer progression and metastasis dissemination. However, the role of CCR2–CCL2 signaling in pathogenesis of B-cell malignancies is not clear. Previously, we showed that CCR2B was upregulated in ex vivo peripheral blood B cells upon Epstein‒Barr virus (EBV) infection and in established lymphoblastoid cell lines with the EBV latency III program. EBV latency III is associated with B-cell lymphomas in immunosuppressed patients. The majority of EBV-positive Burkitt lymphoma (BL) tumors are characterized by latency I, but the BL cell lines drift towards latency III during in vitro culture. In this study, the CCR2A and CCR2B expression was assessed in the isogenic EBV-positive BL cell lines with latency I and III using RT-PCR, immunoblotting, and immunostaining analyses. We found that CCR2B is upregulated in the EBV-positive BL cells with latency III. Consequently, we detected the migration of latency III cells toward CCL2. Notably, the G190A mutation, corresponding to SNP CCR2-V64I, was found in one latency III cell line with a reduced migratory response to CCL2. The upregulation of CCR2B may contribute to the enhanced migration of malignant B cells into CCL2-rich compartments.
Small-scale plasmid DNA preparation or miniprep is a fundamental technique in estimation cloning experiments and is widely used for DNA methylation analysis in epigenetic research. Current plasmid DNA minipreps use the alkali-SDS-based method in a three-solution format and require spin column-based purification steps. This procedure requires the vortexing or pipetting of pelleted bacteria by centrifugation and manual mixing of the solutions. Here, we describe a centrifuge/mixer-based instrument with the ability to perform centrifugation, vibration, and rotor oscillation in order to perform all steps of plasmid DNA isolation by device only. We found that by applying rotor oscillation-driven mixing of solutions added in the lysis and neutralization steps, homogeneous mixing was achieved within 5 s at a rotor oscillation amplitude of 45° and oscillation frequency of 400 ± 30 rpm, yielding the maximal quantity and quality of plasmid DNA. No increase in host chromosome presence purified by this approach occurs for high-copy-number plasmids compared to manually performed miniprep, and indeed, there is a significant decrease in the presence of the chromosomal fraction in low-copy-number plasmids. The supercoiled form of plasmid DNA purified at a rotor oscillation amplitude of 45° does not turn into an open circular (OC) isoform when the plasmid is stored for 1 year at plus four degrees, in contrast to the plasmid purified with rotor oscillation amplitudes of 270°, 180° and 90°. The programmed time-work-efficient protocol of plasmid miniprep installed in the device gives the extreme simplicity of plasmid minipreps speeding up and facilitating the isolation of plasmid DNAs.
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