大腸直腸癌生物分子標幟之研究

Abstract

大腸直腸癌一直是許多西方工業化國家中常見的癌症之一，在許多國家中，以美國為例，近幾年來大腸直腸癌均居於所有致死癌病中的第二位，估計在美國每年有 15 萬人以上得此病症。西風東漸，西式飲食的盛行，導致台灣地區大腸直腸癌發生率有日益升高的趨勢，根據衛生署的統計，大腸直腸癌的發生率由 1980 年每十萬人口中之 5. 95 人，增加至 1990 年的 12.29 人，而至 1997年公佈的大腸直腸癌發生率，己攀升至 13.2人。 一般認為大腸直腸癌的發生與飲食、遺傳等因素均有關係，其預防之道乃在於早期發現早期施於治療，其存活率仍極高。隨著生物醫學及分子生物技術的日新月異，對大腸直腸癌癌化的分子機轉有更多的認識，但仍難以一窺全貌。雖截至目前為止己有許多與大腸直腸癌相關的基因被報告出來，如: C-myc、ras、DCC、MCC、P53等；此些因可能是產生突變或具有差異表現，但相信有更多的基因參與癌症發生的過程，根據文獻報告在正常與癌症組織之間約有百分之一的基因具有差異表現，即大約 2000 個基因左右。因此探求其他參與大腸直腸癌癌化基因,對於了解致癌的過程能有更進一步暸解，相信對於大腸直腸癌的診斷、預防及治療會有所幫助。 本論文實驗第一部份乃承先前利用差異表現法,研究分化型與未分化型甲狀腺癌細胞株，發現一具差異表現的基因- Matrix Gla protein，推測此基因亦可能在大腸直腸癌中參與癌化過程或分化程度或轉移之可能。因此，以此基因為探針利用 Northern blo t的方法進行大腸直腸癌組織與正常組織對的篩檢。結果發現在80組檢體中有76%，其癌組織之MGP 之mRNA 表現量下降，甚至不表現的情形。 另外，以cDNA Microarray此項技術研究正常組織與癌組織及原位癌的大腸直腸癌細胞株與轉移性的大腸直腸癌細胞株，基因的差異表現情形，發現在588個己知與癌症相關的基因中：在組織檢體的研究結果方面，有11個基因在癌組織有超量表現的情形，另有55個基因在正常組織在超量表現。在癌細胞株的研究中有36個基因在轉移癌細胞株(CoLo 205)有超量表現；有50個基因在原位癌細胞株(CoLo 320DM)有超量表現。

Colorectal cancer has been listed as the major cause of death among cancers for most western development nations, and as the top three in Taiwan area in 1997. If diagnosed at its early staging, the 5-year survival rates will be higher than 50%. However, the lack of an effective early-detection screening methods is the major barrier to improve the treatment of patients with colorectal cancer. For of reason of this searching for biomarkers and under-standing the more molecular biological information about colorectal cancer has become the most important issue now, since such markers will useful and helpful on early diagnosis, treatment and prognosis of this disease. Although several genes have been reported to be mutated or differentially expressed in colorectal cancer, a much larger number of genes are likely to be involved in the transformation of colorectal epithelial cells. In this study, Part1:we use the matrix Gla protein MGP gene as a probe to analysis the expression volume of the RNA level in colorectal cancer, in the present study we found that the MGP expression is down regulated in 75% of colorectal cancer compared with their pair normal tissue. This finding suggest that the loss of MGP expression may be associated with tumor progression and metastasis. Part 2:Using the technique of differential hybridization of AtlasTM Human Cancer cDNA expression array to study the differences in gene expression between difference biological conditions. Auto-radiographic analysis showed that of the 588 genes analyzed, 55 are over-expressed in normal colorectal tissue and 14 in Duke*s A tumor tissue. 40 are over-expressed in Duke*s B tumor tissue and 40 in Duke*s C Tumor tissue. 36 are over-expressed in CoLo 205 cell line and 48 in CoLo 320DM cell line.