利用DNA烷化試劑以及其衍生物標的BRCA基因缺陷癌細胞

Abstract

去氧核醣核酸 (DNA) 之間的鏈間交聯 (interstrand cross-link, ICL) 是一種極具細胞毒性的DNA損傷。當雙股DNA被相互嵌合無法解開時，容易影響後續DNA複製、轉錄等重要細胞生理現象，最終導致DNA的雙股斷裂 (double-strand break, DSB)。氮芥類化合物 (nitrogen mustard) 藉由與DNA烷化反應造成鏈間交聯，如今被廣泛運用在癌症的化療藥物上。在此研究中我分析由陳昭岑教授實驗室所合成的新興烷化試劑COOH-SW相關細胞實驗，並且發現當同源修復 (homology-directed repair, HDR) 的相關重要基因如BRCA1與BRCA2缺陷時，細胞會對於COOH-SW更加敏感。 除此之外，陳昭岑教授實驗室更進一步合成COOH-SW的衍生物：BMVC-SW，其含有兩個攻擊端 (warhead)，一個是承接COOH-SW的烷化攻擊端，另一個則是一種鳥嘌呤四聯體 (G-quadruplex, G4) 的配體 (ligand) BMVC (3,6-bis (1-methyl-4-vinylpyridinium iodide) carbazole)。在BMVC-SW的相關細胞實驗分析中，利用螢光顯微鏡觀察到BMVC-SW可以穩定地嵌合在細胞核內的DNA上。在許多種癌症細胞毒性測試中，發現BMVC-SW相較於COOH-SW、BMVC以及兩者共同混合皆具有更高的細胞毒性。最重要的是BMVC-SW也和COOH-SW相似，當細胞同源修復缺陷時會對於BMVC-SW更為敏感。整體來說，在與陳昭岑教授實驗室的合作研究中，我們發現BMVC-SW比個別烷化攻擊端更具有細胞毒性，而且可以針對性地毒殺BRCA基因缺陷 (BRCA-deficient, BRCAness) 相關癌症細胞，並期望有未來更深廣的臨床相關應用。

DNA interstrand cross-link (ICL) is one of the most cytotoxic lesions among many kinds of DNA damages. ICLs block essential cellular processes such as DNA replication and transcription, and thus generate DNA double-strand breaks (DSBs). It has been well documented that nitrogen mustards induce ICLs by DNA alkylation on both strands. Here we introduced a new DNA alkylating agent COOH-SW, generated by Professor Chao-Tsen Chen’s lab. Interestingly, my cell-based studies showed that cancer cells defective in a homology-directed repair (HDR), such as BRCA1/2-deficient cells, are sensitive to COOH-SW. Furthermore, Professor Chen’s lab further synthesized a novel DNA alkylator that combines alkylating warhead of COOH-SW and G-quadruplex (G4) ligand 3,6-bis (1-methyl-4-vinylpyridinium iodide) carbazole (BMVC) named BMVC-SW. Cell-based fluorescent images evidenced that BMVC-SW steadily bound to nucleus DNA. Moreover, I found BMVC-SW had more cytotoxicity than COOH-SW, BMVC, and combination treatment of both together in different types of cancers. Importantly, similar to COOH-SW, my cell-based studies showed that cancer cells defective in a homology-directed repair are sensitive to BMVC-SW. Thus, our collaborative research demonstrated BMVC-SW possesses more cytotoxicity than DNA alkylator alone and reveals novel selective chemicals toward BRCA-deficient (BRCAness) cancers.