探討類幾丁質酶在卵巢癌中扮演的角色:聚焦在癌症幹細胞

Abstract

類幾丁質酶（Chitinase-3-like 1或Chitinase-3-like protein 1）是一種分泌型的醣蛋白，與發炎反應、纖維化、氣喘、細胞外組織重塑和實質固態瘤有相關性。我們研究團隊之前已經發現了類幾丁質酶可能是上皮性卵巢癌的潛在預後生物標記。因此，為了評估類幾丁質酶對卵巢癌的生物學功能及可能的機轉，我設計並進行了以下實驗，包括對於卵巢癌細胞株與病人檢體使用即時聚合酶鏈鎖反應（Real-time-PCR）將類幾丁質酶定量比較，培養癌症幹細胞腫瘤球體形成，將卵巢癌細胞株進行細胞側群分析，Aldefluor測試和細胞凋亡測定，對病人腹水檢體使用酵素免疫分析法（ELISA），免疫墨點法和動物實驗。我首先發現類幾丁質酶在病人檢體中的大量表達與卵巢癌患者的較差的預後和較高化學治療藥物抗性有正相關。CA5171卵巢癌類幹細胞中類幾丁質酶的mRNA表現比原CA5171親代癌細胞株高3倍。類幾丁質酶促進卵巢癌類幹細胞的特性，包括在腫瘤細胞中產生更多和更大的癌症幹細胞腫瘤球體和更高百分比的醛去氫酶（ALDH+），並對細胞毒性藥物誘導的細胞凋亡產生抗性，也就是類幾丁質酶可以幫助癌細胞更容易形成癌症幹細胞腫瘤球體，形成此球體後，類癌症幹細胞數目整體上也會增加，因而造成病人產生更差的預後。類幾丁質酶可以活化Akt（必需)和Erk訊息傳遞路徑，然後增強beta鏈蛋白（beta-catenin）和SOX2蛋白的表現，最後促進癌症幹細胞腫瘤球體形成和卵巢癌類幹細胞的其他特性。大量表現類幾丁質酶的OVCAR3細胞的在動物體內更容易讓腫瘤形成，而CA5171 抑制類幾丁質酶後在動物體內就無法讓腫瘤形成。所以，我得出結論是類幾丁質酶可以極大地增強卵巢癌類幹細胞的特性，並且類幾丁質酶或類幾丁質酶調節的訊息傳導途徑和分子可能是卵巢癌的潛在治療靶點。

Chitinase-3-like 1or named Chitinase-3-like protein 1 (CHI3L1) is a secreted glycoprotein and associated with inflammation, fibrosis, asthma, extracellular tissue remodeling and solid tumors. The previous study of our research team showed that CHI3L1 could be a potential prognostic biomarker for epithelial ovarian cancer. Therefore, I performed the following experiments including the quantitation of CHI3L1 expression level by using Real-time polymerase chain reaction(Real-time-PCR), tumor spheroid formation, side-population assays for ovarian cancer cell lines, Aldefluor and apoptotic assays, Enzyme-Linked Immunosorbent Assay (ELISA) for ascites of cancer patients, immunoblotting, and animal experiments to evaluate the biological function of CHI3L1 on ovarian cancer and the possible mechanism(s). I first found that high expression of CHI3L1 was associated with poor outcome and chemoresistance in ovarian cancer patients. The mRNA expression of CHI3L1 in CA5171 ovarian cancer stem-like cells was 3-fold higher than in ovarian CA5171 parental cancer cells. CHI3L1 promoted the properties of ovarian cancer stem-like cells including generating more and larger tumor spheroids and a higher percentage of ALDH+ in tumor cells, and promoting resistance to cytotoxic drug-induced apoptosis. Hence, CHI3L1 could result in poor outcome of ovarian cancer patients by increasing the number of the cancer stem-like cells. CHI3L1 could induce both the Akt (essential) and Erk signaling pathways, then enhance expression of -catenin followed by SOX2, and finally promote tumor spheroid formation and other properties of ovarian cancer stem-like cells. OVCAR3 CHI3L1-overexpressing transfectants were more tumorigenic in vivo, whereas CA5171 CHI3L1-knockdown transfectants were not tumorigenic in vivo. I concluded that CHI3L1 critically enhances the properties of ovarian cancer stem-like cells. CHI3L1 or CHI3L1-regulated signaling pathways and molecules could be potential therapeutic targets in ovarian cancer.