大腸直腸癌K-ras突變基因影響臨床預後之機轉研究

研究背景:在台灣地區，大腸直腸癌(Colorectal cancer, CRC)位居癌症死亡原因的第三位，且自2008年起其發生率一直居所有癌症中的第一位。在新診斷的病例中，約有20-25%的患者為疾病晚期，併有遠處轉移，即使在接受治癒性切除後，約30%的晚期CRC患者仍會復發， Normanno ( 2009)證實，k-ras基因突變與轉移性CRC患者的標靶治療抗藥性有關，而k-ras基因會誘導核醣核苷酸還原酶M2(ribonucleotide reductase M2, RRM2)的表現，因此RRM2和p53R2的表現與腫瘤惡性程度及數種癌症的進展可能有關。本研究目的在確定p53R2 / RRM2與上游之miR-211表現、p53、APC和k-ras基因狀態與CRC患者臨床結果的關係。研究方法:本研究共收集192個大腸直腸癌腫瘤組織樣本，利用免疫組織化學染色法及DNA直接定序法分析腫瘤組織中的p53R2/ RRM2蛋白表現及p53/APC/k-ras基因突變，並透過即時定量聚合酶鏈鎖反應(real-time polymerase chain reaction)檢測miR-211的表現量。研究結果:結果發現相較於無淋巴結及遠處轉移的早期CRC患者，有淋巴結轉移及遠處轉移的晚期CRC患者出現較低量的p53R2表現及較高量的RRM2表現。RRM2的高量表現與CRC患者的整體存活期(overall survival, OS)及無病生存期(disease-free survival, DFS)呈負相關。腫瘤組織中的RRM2高表現與k-ras基因突變有關。CRC患者腫瘤組織中RRM2的表現與上游的miR-211呈負相關，且miR-211的表現與k-ras突變患者的存活與腫瘤復發相關。結論:根據上述研究成果推測CRC患者腫瘤組織中miR-211的調降和RRM2的過度表現可用於預測腫瘤轉移和疾病預後，特別是對有k-ras基因突變的患者。

Background: Colorectal cancer (CRC) ranks as the third-leading cause of cancer-related deaths in Taiwan. The expression of ribonucleotide reductase M2 (RRM2) and p53R2 is correlated with tumoral malignancy and progression in several types of cancer. Methods: The aim of this study was to determine the association of p53R2/RRM2 with upstream expression of miR-211 and the association of expression levels of p53, APC, and k-ras with clinical outcomes in CRC patients. The study consisted of 192 tumor tissue samples obtained from CRC patients. Immunohistochemistry and DNA direct sequencing were performed to analyze p53R2/RRM2 protein expression and p53/APC/k-ras gene mutations in these samples. The expression level of miR-211 was detected by the real-time polymerase chain reaction (PCR). Results: The results showed that the expression of p53R2 was lower and that of RRM2 was higher in patients with lymph node metastasis, distant metastasis, and late-stage CRC as compared to patients without lymph node metastasis, distant metastasis, and early-stage CRC. High expression of RRM2 in patients had a negative impact on overall survival (OS) and disease-free survival (DFS) in CRC. The expression of RRM2 in tumor tissues was positive and correlated with that of the k-ras gene mutation. Upstream miR-211 expression was negatively correlated with RRM2 expression in tumor tissues of CRC patients, and it was correlated with patient survival and tumoral recurrence in patients with k-ras mutations.Conclusion: We suggest that downregulation of miR-211 and overexpression of RRM2 in tumor tissues of CRC patients could be used to predict metastases and disease prognosis, especially in patients with k-ras gene mutations.