Evaluation and statistical optimization of a method for methylated cell-free fetal DNA extraction from maternal plasma

Purpose: Methylated cell-free fetal DNA (cffDNA) in maternal plasma can potentially be used as a biomarker for accurate noninvasive prenatal testing (NIPT) of fetal disorders. Recovery and purification of cffDNA are key steps for downstream applications. In this study, we aimed to developed and evaluated different aspects of an optimized method and compared its efficiency with common methods used for extraction of methylated cffDNA. Methods: Single factor experiments, Plackett-Burman (PB) design, and response surface methodology (RSM) were conducted for conventional Triton/Heat/Phenol (cTHP) method optimization. The total cell-free DNA (cfDNA) was extracted from pooled maternal plasma using the optimized method called the Triton/Heat/Phenol/Glycogen (THPG), cTHP method, a column-based kit, and a magnetic bead-based kit. In the next step, methylated cfDNA from the extracted total cfDNA was enriched using a methylated DNA immunoprecipitation (MeDIP) kit. Real-time quantitative polymerase chain reaction was performed on the RASSF1 gene and hyper region to determine the genomic equivalents per milliliter (GEq/ml) values of the methylated cfDNA and cffDNA, respectively. Results: The optimum values of the significant factors affecting cfDNA extraction from 200 μl of plasma were 3% SDS, 1% Triton X-100, 0.9 μg/μl glycogen, and 0.3 M sodium acetate. The GEq/ml values of methylated cffDNA extracted using the THPG method were significantly higher than for the tested extraction methods (p < 0.001). Conclusions: Our results indicate that the THPG method is more efficient than the other tested methods for extraction of low copy number methylated cffDNA from a small volume of maternal plasm

Sildenafil enhances cisplatin-induced apoptosis in human breast adenocarcinoma cells

Introduction: Cyclic nucleotide phosphodiesterase (PDE) enzymes are a large superfamily of enzymes that catalyze the conversion reaction of cyclic adenosine monophosphate (AMP) and cyclic guanosine monophosphate (GMP) to AMP and GMP, respectively. In some cancer cells, PDE-5 has been shown to be overexpressed in multiple human carcinomas. It seems that the inhibition of PDE-5 may has anticancer effects. Cisplatin is one of the prevalent chemo-agents to treat solid tumors. However, its clinical usefulness is hindered by dose-limiting toxicities, especially on the kidneys (nephrotoxicity) and ears (ototoxicity). In this study, the antitumor activity of the sildenafil as a PDE-5 inhibitor alone and in combination with cisplatin on human mammary adenocarcinomas and MCF-7 and MDA-MB-468 was assessed. Materials and Methods: Sildenafil as PDE type 5 (PDE5) inhibitor is the drugs that we combined with the cisplatin (chemotherapeutic agent), in vitro. Human mammary adenocarcinomas and MCF-7 and MDA-MB-468 cell lines were cultured in standard conditions. At time point, following 24 h and 48 h incubation, the cell lines were treated by cisplatin in the presence/absence of sildenafil. Cell viability, apoptosis, and reactive oxygen species (ROS) were measured using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay, real-time polymerase chain reaction, and Western blot; and fluorimetric methods, respectively. Statistical analysis was performed using SPSS software SPSS (SPSS Inc., Chicago, IL, USA). Results: In MCF-7 cell line, following 24 h incubation, combinations of sildenafil with cisplatin (P < 0.001) showed decreased cell viability when compared to sildenafil and cisplatin alone. Moreover in MDA-MB-468 cell line, following 24 h incubation, data did not show any significant changes on cell viability when treated with cisplatin, in the presence or absence of sildenafil. However, following 48 h incubation, combinations of cisplatin with sildenafil (P < 0.001) were showed decreased cell viability when compared to cisplatin and sildenafil alone in both MCF-7 and MDA-MB-468 cell lines. Concerning the ROS production and apoptosis, data showed that both processes increase significantly in the presence of the sildenafil in comparison absent it. Conclusion: Our data showed that the combination of sildenafil with cisplatin can improve cell toxicity and anticancer effect of cisplatin. And also sildenafil as a PDE-5 inhibitor could be used as additive treatment in combination with cisplatin to make a reduction in cisplatin dosage and its side effects. © 2020 Journal of Cancer Research and Therapeutics | Published by Wolters Kluwer - Medknow