人類胸苷酸激酶抑制劑的合成與鑑定

Abstract

在人體中，胸苷三磷酸(dTTP)的供給與生成對DNA的合成與修補來說佔有舉足輕重的地位。而在胸苷三磷酸的生成過程中，胸苷酸(dTMP)必須經由胸苷酸激酶(thymidylate kinase, TMPK)的磷酸化過程形成胸苷二磷酸(dTDP)，再透過核苷酸激酶的磷酸化進而產生胸苷三磷酸。干擾胸苷三磷酸的生成使細胞修復機制受損，已經是許多癌症化學治療藥劑發展的重要策略。在張智芬教授與胡春美博士的研究中顯示，以小片段干擾RNA的方式抑制胸苷酸激酶的表現，可有效降低胸苷三磷酸的含量並促使癌細胞敏感於基因毒化物的毒殺能力。但由於小片段干擾RNA的應用仍然受限於其遞送的效率，因此利用小分子去抑制胸苷酸激酶的活性應是較可行的策略。 在本篇論文中，我根據胡春美博士高效率藥物篩選的結果，針對一有效的前驅人類胸苷酸激酶抑制劑(YMU1)建立合成路徑，並在張智芬教授實驗團隊的幫助下，對其抑制劑作細胞與活鼠實驗，證實其化合物有效抑制人類胸苷酸激酶，並增加低劑量癌症藥物小紅莓(Doxorubicin)所誘導的細胞死亡。為了瞭解YMU1對胸苷酸激酶的抑制活性,並找尋更好的抑制劑，我設計並合成一系列YMU1的衍伸物，測試其結構與活性之間的關係。根據我們的研究結果，目前已有13個YMU1衍伸物已被證實具有與YMU1相同程度的抑制能力，並依所有44個YMU1衍伸物的結構與抑制活性的關係，推論出針對人類胸苷酸激酶有效抑制的化學結構，以利未來抑制劑的開發。

Human thymidylate kinase (hTMPK) plays an essential role in dTTP supplement by catalyzing the reversible phosphoryl transfer from a donor (preferably ATP) to the acceptor TMP. The process of dTTP biosynthesis is required for efficient DNA replication and repair in cells. Introduction of genotoxic insult has been a major chemotherapeutic dogma in cancer treatment; Hu and Chang have shown that blocking dTTP supply could amplify DNA damage signal in highly proliferating tumor cells, thereby sensitizing these cells to chemotherapeutic agent such as doxorubicin, a topoisomerase II inhibitor. In my research, I aim to find cell permeable small molecules as to block hTMPK function. Based on the luciferase-coupled TMPK assay, a heterocyclic compound, YMU1, was found to be an hTMPK inhibitor. Many YMU1 derivatives were synthesized, and their effects on TMPK inhibition were evaluated. Moreover, inhibition of TMPK enhanced tumor lethality when treated with a low dose of chemotherapeutic agent. The combined treatment is a potential novel chemotherapy against cancer cells. The general structural features of YMU1 derivatives include (1) a heterocycle H1 that may comprise 1–4 heteroatoms of N and O elements, (2) 1–3 substituents, G, on H1, (3) another heterocycle H2 in the linker, and (4) a library of R groups. According to our study, we have synthesized and identified other 13 compounds having comparable level of inhibitory activity against hTMPK like YMU1.