肺癌在全球排名都是名列前茅，死亡率在2013年統計位居第一名，肺癌致死率高，主要原因是肺癌發現時已經是晚期，而且肺癌治癒率低。在治療癌症的過程當中，不管是放射線治療或是化療，對於病人副作用很大並且預後差，為了克服這樣的困難，出現許多報導探討天然藥物。樺木酸經由白樺木樹皮被萃取出來，擁有五環三帖的結構，在1995年被發現它可以有效的抑制腫瘤的生長，在細胞實驗或是活體試驗都有被證實，並且樺木酸具有選擇性毒殺，對於癌細胞的敏感度大於正常細胞。樺木酸抑制腫瘤的機轉主要是透過細胞凋亡的內在路徑，誘導粒線體內的細胞色素C的釋放，活化caspase-3導致細胞的死亡。先前我們實驗室在動物實驗當中證實了樺木酸可以抑制肺癌的生長，作用機轉是透過Sp1的降解，抑制腫瘤形成。在我的研究當中我們嘗試樺木酸的衍生物，想要找尋到對於肺癌細胞的毒殺功能更強，而副作用低的化合物。首先我們利用計數細胞的方式篩選這些樺木酸的衍生物，結果篩選出七個樺木酸衍生物對於肺癌細胞的毒殺效果比樺木酸好。從七種樺木酸衍生物當中挑選三個(SYK010, SYK019, SYK023)做後續的動物實驗，由異種移植的免疫缺陷鼠證實SYK023的效果是當中最好的，之後由我們實驗室所建立的Kras誘導肺癌的基因轉殖鼠，探討SYK023是否可以影響肺癌的形成，結果顯示SYK023的確可以抑制肺癌的形成。我們想要了解SYK023是否有其他的副作用，結果顯示出SYK023並不會影響到心臟、肝臟以及腎臟的功能。進一步我們探討SYK023是透過什麼樣的機轉來抑制腫瘤的生成，首先我們先用了流式細胞儀發現到SYK023會引起細胞凋亡，使用的濃度比樺木酸更低就會引起凋亡的現象，而之後我們證實SYK023引起的cleavage caspase-3 的濃度比樺木酸更低。我們經由細胞型態發現處理SYK023的細胞會有液泡產生，隨之我們開始探討SYK023是否會引起內質網壓力，由結果顯示出SYK023會比較早就引起內質網壓力，活化GADD153誘導細胞的凋亡。另一方面我們也發現到SYK023會使甲型微管蛋白減少，是透過泛素化的降解。

Betulinic acid (BA) isolated from bark of white birch contains pentacyclic triterpenoid that exhibits potent anti-inflammatory, anti-malaria, anti-retroviral, and anti-tumor properties. BA could induce apoptosis by loss of mitochondrial potential, leading to cytochrome-c release, which in turn regulates the downstream caspase activation. Our recent study also show that BA could repress the cancer cells growth and reduce Sp1 protein stability. Herein we tried to increase the effect of BA in lung cancer therapy by modifying BA molecule. Therefore, more than thirty BA derivatives were used to evaluate their anti-cancer activity by cell number counting and MTT assays. Result indicated that several BA derivatives induced more cytotoxicity than BA itself in lung cancer cells. Subsequently, three more effective BA derivatives (SYK010, SYK019 and SYK023) were used for further study. At first, in these BA derivatives treated cells showed more Sub-G1 than BA treated cells, indicating these BA derivatives could induce more cell apoptosis than BA itself. Second, the effects of these BA derivatives were then evaluated in animal experiments including in Xenograph mice system and KrasG12D-induced lung cancer mice system. Results indicated that compound, SYK023, was more effective in preventing cancer formation than BA or SYK019 treatment. Finally, we found that BA and SYK023 treatments could induce ER stress, which might be related to the apoptosis. However, more direct evidence needs to be provided in the near future to support that SYK023 could induce an ER stress-mediated apoptosis, leading to the repression of cancer growth. Taken together, in this study, we found a novel BA derivative, SYK023, with more anti-cancer effect though inducing the ER stress-mediated apoptosis. The results showed the SYK023 increased Grp78 protein level more than BA, and it also increased the tubulin and total ubiquitination more than BA in lung cancer cells.

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