乳癌石蠟包埋組織於人身鑑別的可適用性

Abstract

'鑑定'是法醫的主要工作，然而法醫學的鑑定不是局限在死因之鑑定，在司法領域中尚有許多和法醫有相關的鑑定工作，例如：親子鑑定、血緣鑑定也稱人身鑑別、物證鑑定、傷痕鑑定，在面對種種來源的證物、血斑、精斑、唾液斑、汗斑、皮膚、毛髮、指甲，甚至牙齒、骨骼等組織檢體，大部份都是仰賴DNA的鑑定技術。其中組織包埋在石蠟中理論上其相對DNA是呈穩定狀態被貯存的，而且從石蠟中去萃取組織DNA來當作鑑定已不是困難的事，不過，值得探討的是，假如使用的蠟塊包埋組織來源是癌症組織，是否有可能因有基因突變(癌症細胞增生)而造成與本來個體之正常組織的DNA不一樣了呢？而它能否可用來當成作鑑定的標準？ 本文的研究利用在一年期間，2007年8月~2008年6月搜集了50個外科切除的乳癌病患之癌組織來供作研究中的實驗組，並同時研究病人身體的其他正常組織如靜脈血液當對照組。在石蠟組織的 DNA萃取，只有36個達到可分析的量，另外有14位病人的石蠟組織的DNA萃取的STR (short Tandem Repeats 短串聯重複序列)表現不完全，所以剔除在本分析之外，故可分析率是72% ( 36/50) ，血液的DNA萃取則全數成功。結果發現有92 ﹪(33/36)其癌組織STR 15 基因座與其血液是完全相匹配，而有3人的蠟塊包埋組織發現有突變，突變率是8.% ( 3/36), 3位突變均只發生在單一個基因座上( single locus )，在血緣鑑定中，以STR分型來評量，只發生單一基因座的突變並不足以用來排除二者非來自於同一個體，必須有二個或以上的位點不一樣 才能懷疑來自不同個體。 所以藉由本研究結果， 似乎至少證明大部份癌變組織中的DNA與未發生癌變的同一人身上其他正常組織的DNA是相同的，或許在沒有其他可比對的情況下石蠟包埋癌症組織仍可以提供作為DNA鑑定及人身鑑別的輔助來源或參考。

“Investigation” is the major work of Forensic Medicine. The forensic identification is not only restricted to realize the reason of death, but also involves a lot of judicial investigations, such as parentage analysis, paternity test or personal identification and biological evidence examination. Most of the forensic evidence examination, for example, blood, sperm, sweat, skin, hair, nail and even teeth and bone, relies on DNA analysis technology. Short tandem repeat (STR) system is one of the main methodologies used in criminal investigation activities. Evidences have shown that DNA in paraffin-embedded tissues is relatively stable, and it is not difficult to extract DNA from paraffin-embedded tissues. Furthermore, it has been proved that cancer is induced by accumulation of genetic mutations. Thus, it is worthy to consider that if the paraffin-embedded cancer tissues could provide a model of forensic identification. In this study, we assayed 50 paraffin-embedded breast cancer tissues, which were collected from August 2007 to June 2008, and their counterpart blood specimens as control groups. The extraction rates of DNA were 72% (36/50) in paraffin and 100% in blood specimens, respectively. We revealed that 92 % (33/36) of 15 STR loci polymorphism in cancer tissues was perfectly matched with blood samples. The rest of 3 paraffin-embedded specimens DNA were found to be mutated from control group, which the mutation rate was approximately 8% (3/36). In addition, we also discovered that these 3 tissues have the same single locus mutation. Using STR system to evaluate the parentage relationship, single locus mutation is not enough to exclude the possibility that the two specimens are from the identical source. More than two loci of different are needed. Thus, these results demonstrate that DNA in most of cancer tissues is not mutated from normal parts, indicating that in some circumstances, paraffin-embedded cancer tissues might provide usefulness source of DNA analysis and forensic personal identification.