title: Microwave heating of long-term formalin-fixed surgical pathology specimens improves quality of extracted DNA.
abstract: A large amount of DNA of high quality is essential for molecular analysis. The amount of DNA in routine paraffin sections is small. Surgical specimens retained in formalin for the long-term (several months) left over from the sampling required for wax embedding can be referred to as "long-term formalin-fixed" specimens, and clearly this material is a rich source of DNA; however, it is difficult to extract. In the current study, we designed a microwave-heating method for DNA extraction from these specimens. We found that the heating procedure achieved greater DNA yields than a common nonheating method used for comparison (DNA contents mean±SD, heating 2.16±0.95 μg/μL vs. common 1.75±0.90 μg/μL, P<0.05). Fluorescence multiplex polymerase chain reaction-capillary electrophoresis successfully detected microsatellite instability (MSI) in the DNA samples derived from this heating procedure (98.4%, 689 of 700 sample tests), at significantly higher levels than from the conventional method (82.3%, 247 of 300 sample tests, P<0.05). We identified 10 (14.3%) MSI with high frequency and 6 (8.6%) MSI with low frequency colorectal cancers. MSI with high frequency cancers showed distinct clinicopathologic features including higher incidence of right-sided location, high histologic grade, mucin-production, and prominent intraepithelial lymphocyte infiltration. We concluded that the microwave-heating method was efficient for DNA isolation from long-term formalin-fixed tissue samples. The successful fluorescence multiplex polymerase chain reaction-capillary electrophoresis analysis in these samples might facilitate MSI detection in clinical practice.
authors.affiliation: Department of Oncology, Quzhou Municipal Hospital, Quzhou, Zhejiang Province, PR China.
authors.forename: Shanshui
authors.initials: S
authors.lastname: Wu
authors.forename: Xin
authors.initials: X
authors.lastname: Qian
authors.forename: Xinchun
authors.initials: X
authors.lastname: Yu
authors.forename: Hongqiang
authors.initials: H
authors.lastname: Sheng
authors.forename: Bingjian
authors.initials: B
authors.lastname: Lü
mesh_terms: D000368:Aged; D001706:Biopsy; D015179:Colorectal Neoplasms / Q000737:chemistry* / Q000175:diagnosis* / Q000473:pathology; D004273:DNA, Neoplasm / Q000302:isolation & purification*; D019075:Electrophoresis, Capillary; D005260:Female; D005404:Fixatives; D005453:Fluorescence; D005557:Formaldehyde; D006361:Heating; D006801:Humans; D059627:Liquid Phase Microextraction; D008297:Male; D053842:Microsatellite Instability; D008872:Microwaves; D008875:Middle Aged; D060885:Multiplex Polymerase Chain Reaction; D016612:Paraffin Embedding; D010340:Pathology, Surgical
chemical_list: D004273:DNA, Neoplasm; D005404:Fixatives; D005557:Formaldehyde