普通甲醛固定石蜡包埋组织DNA提取方法的探讨

背景与目的:在国内,几乎所有的医院和科研机构均应用普通甲醛固定手术标本,但因为普通甲醛固定石蜡包埋组织中的DNA降解相对严重,从这些蜡块中提取高质量的DNA非常困难。本研究的目的是寻找从普通甲醛固定石蜡包埋组织中提取DNA的理想方法。方法:取我院2000年甲醛固定石蜡包埋的手术切除食管癌标本15例,分别以蛋白酶K消化和不同pH值下加热两种裂解方法裂解细胞,以酚氯仿抽提法提取其DNA;并在蛋白酶K消化法进行DNA提取的过程中,应用交叉设计对二戊烯或二甲苯脱蜡、37℃或56℃消化48h或72h、氯化钠盐析或酚氯仿抽提4种参数进行研究,所得DNA质量以电泳分析和PCR扩增结果判断。结果:蛋白酶K消化酚氯仿抽提法所得DNA产量(平均值为17.88μg)和质量均高于pH值为7～12条件下的加热提取法(P<0.05)。56℃消化所得的DNA质量明显优于37℃,而消化72h的DNA亦明显优于48h者。不同脱蜡方法和抽提方法对DNA的产量和质量影响不大,结论:以蛋白酶K消化氯化钠盐析法,从普通甲醛固定石蜡包埋组织中提取DNA质量较可靠。并且,应用蛋白酶K于56℃消化3天更能获得高质量和高产量的DNA。

A study on the method of DNA extraction from unbuffered formalin-fixed and paraffin-embedded samples

BACKGROUND & OBJECTIVE: Unbuffered formalin is widely used to fix resected specimens in China. The DNA in unbuffered formalin-fixed and paraffin-embedded tissues is usually degraded seriously, so the extraction of DNA from these samples is difficult. This study was conducted to seek an optimal method to extract DNA from these samples. METHODS: Fifteen blocks of esophageal carcinoma resected in Fourth Hospital of Hebei Medical University in 2000 were selected. The cells were lyzed by proteinase K digestion or heating under different pH values, then DNA was extracted by phenol:chloroform. After that, four parameters (deparaffined by xylene or histolene; digested for 48 h or 72 h at 37 degrees C or 56 degrees C; extracted by salting-out or phenol:chloroform) were optimized according to the principle of cross design. At last, the quality of obtained DNA was analyzed with electrophoresis and PCR amplification. RESULTS: The quality and quantity of DNA obtained by proteinase K digestion (the average yield is 17.88 microg) were better than that of heating under different pH (7-12)(P< 0.05). The quality and quantity of DNA digested at 56 degrees C were better than that at 37 degrees C, and similarly, digestion for 72 hours was better than that for 48 hours. The methods of deparaffin and extraction had no obvious influence on the quality and quantity of DNA. CONCLUSION: By means of NaCl salting-out after proteinase K digestion, more reliable quality of DNA can be obtained from unbuffered formalin-fixed and paraffin-embedded samples. Furthermore,digestion for three days at 56 degrees C is more likely to obtain DNA with high quality and quantity.