A Modified Extraction Method of Circulating Free DNA for Epidermal Growth Factor Receptor Mutation Analysis

PURPOSE: Circulating free DNA (cfDNA) in plasma is promising to be a surrogate for tumor tissue DNA. However, not all epidermal growth factor receptor (EGFR) mutations in tumor tissue DNA has been detected in matched cfDNA, at least partly due to inefficient cfDNA extraction method. The purpose of this study was to establish an efficient plasma cfDNA extraction protocol. MATERIALS AND METHODS: The yield of plasma cfDNA extracted by our modified phenol-chloroform (MPC) method from non-small-cell lung cancer (NSCLC) patients was compared with that by QIAamp MinElute Virus Spin kit (Qiagen kit) as control, using the Wilcoxon rank-sum test. TaqMan quantitative polymerase chain reaction (qPCR) assays were used to quantify the plasma cfDNA extracted. Both Mutant-enriched PCR (ME-PCR) coupled sequencing and DxS EGFR mutation test kit were used to evaluate the impact of extraction method on EGFR mutation analysis. RESULTS: MPC method extracted more plasma cfDNA than Qiagen kit method (p=0.011). The proportion of longer fragment (> or =202 bp) in cfDNA extracted by MPC method was significantly higher than by Qiagen kit method (p=0.002). In the sequencing maps of ME-PCR products, a higher mutant peak was observed on plasma cfDNA extracted by MPC method than by Qiagen kit method. In DxS EGFR mutation test kit results, plasma cfDNA extracted by MPC method contained more tumor-origin DNA than by Qiagen kit method. CONCLUSION: An improved plasma cfDNA extraction method of MPC is provided, which will be beneficial for EGFR mutation analysis for patients with NSCLC.

Delineation of chromosome translocations by fluorescence in situ hybridization / 第二军医大学学报

Objective:To delineate the G-banding-sug gested chromosome translocations by fluorescence in situ hybridization (FISH ) technique. Methods: Locus-specific probes, generated by degen erate oligonucleotide-primed PCR (DOP-PCR) technique from yeast artificial chr omosomes (YACs) mapping the regions in question, were used for FISH tests. Results: Among the 2 cases unresolved by G-banding, FISH confirm ed that one had a balanced translocation between chromosome 11 and chromosome 13 , the other had an unbalanced translocation between chromosome 6 and chromosome X.Conclusion: Because of its high sensitivity and specificity, FISH technique is a powerful adjunct to chromosome banding techniques, particula rly for the delineation of subtle chromosome rearrangement(s) and the origin of segment(s).