大腸直腸癌是在台灣的癌症中，發生率排名第三位的癌症，由於細胞中的miRNA 表現量是診斷及癒後的重要的指標之一，因此探討 miRNA 在細胞的功能是很重要的。從過去的文獻報導指出，在大腸直腸癌中，microRNA 181b (miR-181b) 在惡化的細胞中有高度表現的情形；而且 miR-181b 表現量較高的病患對藥物的反應不佳，且較易繼續惡化，這些結果顯示在大腸直腸癌中，miR-181b可能是一個癒後較差的因子。由於 microRNA 會負向調控基因表現，因此我們利用 miRTarBase 搜尋 miR-181b可能會調控的腫瘤抑制因子，Nemo-like kinase (NLK) 便是其中之一。由於在大腸直腸癌中，高達70% 的病患，其APC基因會產生突變，進而使Wnt pathway在其中持續活化；此外，在過去的文獻中指出，NLK 會藉由阻斷 β-catenin 與 TCF 的結合，達到抑制 Wnt pathway 的效果。因此本篇藉由研究 miR-181b 調控 NLK 來探討其在大腸直腸癌中所扮演的角色，以提出一個在治療大腸直腸癌症上的新指標。我們分析從同個病人在不同癌化時期所取出的癌細胞株，SW480 與 SW620，發現較惡化的 SW620 的 miR-181b 的確表現較高、而且其 NLK 的表現較低；此外，在SW480的細胞內表現 miR-181b 後，NLK 的表現也會跟著下降；從 reporter assay 的實驗中也顯示miR-181b會影響NLK 3’-untranslated region (3’UTR) 中帶有 miR-181b 結合位的片段。最後從病人檢體中觀察NLK mRNA及miR-181b的表現，我們認為NLK可能在癌化過程中會被負向調控的因子之一，而 miR-181b 是其中一個調控者，而且由於 miR-181b 在復發的病人表現量亦較高，因此將可進一步探討其與術後復發的關聯性。

Colorectal cancer (CRC) has the third incident rate in Taiwan. Because microRNAs are good biomarkers for diagnosis, it is important to study the functional roles of miRNAs. Previous clinical studies reported that microRNA 181b (miR-181b) is highly expresses in tumor tissues that compared with normal tissues in clinical samples. In addition, it also reported that patients with higher miR-181b in tumor had bad response to chemotherapy. It implies that miR-181b is a poor prognostic factor in CRCs. Because microRNAs repress gene translation, we investigated the possible tumor suppressed targets of miR-181b by miRTarBase, and NLK (Nemo-like kinase) is one of candidates. In colorectal cancer, up to 70% patients have APC gene mutation; therefore, it caused Wnt pathway constantly activation. NLK has reported that it inhibits Wnt pathway by blocking the interaction between β-catenin and T cell factor (TCF). In this study, we would like to validate the functional role of miR-181b in CRCs. The SW480 and SW620 cell lines which derived from the primary tumor and a lymph node metastasis are used in this study, respectively, and we found SW620 cell line has higher expression of miR-181b but lower NLK expression. In addition, over-expressed miR-181b in SW480 cell would decrease NLK level, and the reporter assay data showed miR-181b could regulate gene by targeting to NLK 3'UTR. Finally, we investigated miR-181b and NLK mRNA expression in clinical samples, and the result implies NLK down-regulated in tumorigenesis and miR-181b is one of regulators. In addition, miR-181b is higher in recurrence patients, so cancer recurrence would be a new aspect to study.

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