Roles of miR-129 in colorecal cancer

 描述(申请人提供)：结直肠癌是美国男性和女性癌症死亡的第三大原因。对氟尿嘧啶类药物(如5-氟尿嘧啶/奥沙利铂/亚叶酸钙)化疗耐药是晚期结直肠癌治疗失败的主要原因之一。肿瘤细胞在基因毒性应激后缺乏凋亡能力是导致这种耐药机制的关键因素之一。越来越多的证据表明，非编码microRNAs(MiRNAs)是基因表达的重要调节因子，特别是在急性遗传毒性应激下。然而，仍然有 对miRNAs在结直肠癌细胞凋亡中的作用了解有限。我们最近的研究发现了miR-129通过抑制抗凋亡蛋白Bcl2的表达而介导细胞凋亡的新机制。除Bcl2外，miR-129还抑制5-氟尿嘧啶(5-FU)靶蛋白胸苷合成酶(TS)和细胞周期调控基因E2F3的表达。异位表达miR-129在体内外均通过抑制Bcl2和致敏结肠癌细胞对5-FU的处理恢复了结肠癌细胞系的凋亡。我们进一步证明，在结直肠癌患者中，miR-129的表达缺失是疾病进展过程中的一个关键事件。更重要的是，我们能够用miR-129逆转结肠癌干细胞的化疗耐药性。基于此，进一步研究miR-129的调控机制及其在结直肠癌中的临床意义和影响具有重要意义。在拟议的项目中，我们将检验miR-129确实是结直肠癌的肿瘤抑制因子和对5-FU治疗的化疗敏感性的新调节剂的假设。在特定的目标1中，我们将检验这一假设，即调节miR-129的表达可以是恢复结肠癌干细胞凋亡、细胞周期控制和逆转化疗耐药的有效途径。具体目的2，我们将使用不同的结肠癌小鼠模型和患者标本来检验miR-129在结直肠癌中的临床相关性。具体目标3，我们将通过充分了解miR-129的主要靶点和途径的机制来检验miR-129是一种肿瘤抑制因子的假设。这项拟议的研究将进一步了解miR-129在结直肠癌进展和对以5-FU为基础的化疗的反应中的作用。它有可能开发新的治疗方法来提高5-FU的疗效，使患者受益。

 DESCRIPTION (provided by applicant): Colorectal cancer is the third leading cause of cancer mortality in both men and women in the United States. Resistance to fluoropyrimidine-based (e.g. 5-fluorouracil/Oxaliplatin/Leucovorin) chemotherapy is one of the major reasons for the failure of treating advanced colorectal cancer. The lack of ability for tumor cells to undergo apoptosis after genotoxic stress is one of the key contributors to such resistant mechanism. Mounting evidence has demonstrated that non- coding microRNAs (miRNAs) are crucial regulators of gene expression, in particular, under acute genotoxic stress. However, there is still limited knowledge about the role of miRNAs in apoptosis in colorectal cancer. Our recent studies discovered a novel mechanism of miR-129 mediated apoptosis by suppressing the expression of anti-apoptotic protein Bcl2. In addition to Bcl2, miR-129 also suppresses the expression of 5-fluorouracil (5-FU) target protein thymidylate synthase (TS) and cell cycle control gene E2F3. Ectopic expression of miR-129 restored apoptosis in colon cancer cell lines by suppressing Bcl2 and sensitized colon cancer cells to 5- FU treatment both in vitro and in vivo. We further demonstrated that the loss of miR-129 expression in colorectal cancer patients is a critical event during disease progression. More importantly, we were able to reverse the chemoresistance in colon cancer stem cells with miR- 129. Based on these, it is important to further investigate the regulatory mechanism of miR-129 and its clinical relevance and impact in colorectal cancer. In the proposed project, we will test the hypothesis that miR-129 is indeed a tumor suppressor of colorectal cancer and a novel modulator of chemosensitivity to 5-FU based treatment. In Specific Aim 1, we will test the hypothesis that modulating miR-129 expression can be an effective approach to restore apoptosis, cell cycle control, and reverse chemoresistance in colon cancer stem cells. Specific Aim 2, we will test the clinical relevance of miR-129 in colorectal cancer using various colon cancer mouse models and patient specimens. Specific Aim 3, we will test the hypothesis the miR-129 is a tumor suppressor by fully understanding the mechanism of its major targets and pathways. The proposed investigation will provide further understanding of miR-129 in colorectal cancer progression and response to 5-FU based chemotherapy. It has the potential to develop novel therapeutic approaches to enhance 5-FU efficacy to benefit patients.