在人類細胞中建立正向自我調節迴路以應用至抑制細胞分裂之癌症療法

對於末期癌症的治療中，化學治療和標靶治療扮演很重要的角色。雖然只針對癌症細胞中特定訊息傳遞路徑中的特定調控因子或是酵素的標靶治療已證實所帶來的副作用較少；但在另一方面，這種攻擊特定目標的專一性卻也會使得原本存在，讓細胞本身對藥物具有抗性的突變更容易被選擇出來，而後反而讓腫瘤細胞得以繼續大量繁衍，導致癌症快速的復發，對於整體存活率的提升有限。至於以抑制細胞分裂為對抗方式的化學治療，則會讓體內其他所有能夠不斷生長分裂的細胞都受到影響，像是骨髓的造血幹細胞，進而造成較多較大的副作用，例如白血球數量的低落，使病人的免疫力下降。因此，我們的研究就是希望在以抑制腫瘤細胞週期進行的治療方式為基礎，但於此同時又能讓骨髓幹細胞存活下來，繼續正常地分裂。我們使用合成生物學的方法，希望建構一個可以在人類細胞中表現的分子迴路，能夠具備此種分辨細胞種類及週期狀態的能力，可以更專一且更有效地殺死癌細胞。當中，我們設計了一個正向自我調節回饋迴路(positive auto-regulatory loop)，藉由四環素 (Tetracycline)調控轉錄活化的系統，以螢光蛋白作為播報因子，希望能在人類細胞內，產生一個雙峰分佈(bimodal distribution)。意即讓所有癌細胞在進入細胞分裂時，都能有效開啟基因迴圈，確保其大量表現引起細胞凋亡的蛋白質，而讓癌細胞無法逃過死劫；而反之，則正常細胞的蛋白表現量幾乎為零，因而都可存活下來。最終，希望這樣一個分子迴路的設計，對於未來的癌症基因治療上，能夠加以應用，有所助益。

關鍵字

癌症治療；抑制細胞分裂；合成生物學；正向自我調節回饋迴路；雙峰分佈

並列摘要

Among treatments for the advanced-stage cancers, chemotherapy and targeted therapy are the most common ones. The targeted therapies target a specific enzyme or regulator in a specific signaling pathway in cancer cells, which has been proved to have fewer side effects. But on the other hand, this specificity of targeting has been suggested to be prone to select for preexisting secondary mutations that enable cells resistant to the drug, and acquired resistance would result in rapid cancer recurrence, thus the elevation in overall survival is limited. As for anti-mitotic chemotherapy that blocks cell mitosis, would hence influence survival of other proliferating cells, such as hematopoietic stem cells in bone marrow, and then brings more and deeper side effects. A low blood cell count, for example, would threaten patients’ lives. Therefore, the aim of our research is to inhibit cell cycle for treatment of cancer, while sparing dividing bone marrow cells. With a “synthetic biology” approach, we would construct a cell cycle-targeted molecular device in human cells that is able to sense cell states and differentiate between cancer and normal cells, delivering more specific and effective killing. In this thesis, we designed a positive auto-regulatory loop through tetracycline-controlled transcriptional activation system, using fluorescence protein as reporters to visualize device performance, with hope to induce a bimodal distribution by tuning the circuit response. It means that all cancer cells will initiate this genetic circuit effectively upon entering mitosis, ensuring to express the desired toxic proteins, and go into apoptosis, whereas all normal cells lack toxic protein expression and are able to survive. Consequently, we hope this design of molecular circuit will be applicable to cancer gene therapy in the future.

並列關鍵字

cancer therapy ； synthetic biology ； positive auto-regulation ； bimodality

參考文獻

1. Kris M.G., Natale, R.B., et al. Efficacy of Gefitinib, an Inhibitor of the Epidermal Growth Factor Receptor Tyrosine Kinase, in Symptomatic Patients With Non– Small Cell Lung Cancer: A Randomized Trial. AMA 290, 2149-2158 (2003).

2. Jackson, J.R., Patrick, D.R., Dar, M.M. & Huang, P.S. Targeted anti-mitotic therapies: can we improve on tubulin agents? Nat Rev Cancer 7, 107-117 (2007).

3. Pao, W. & Chmielecki, J. Rational, biologically based treatment of EGFR-mutant non-small-cell lung cancer. Nat Rev Cancer 10, 760-774 (2010).

4. Sprinzak, D. & Elowitz, M.B. Reconstruction of genetic circuits. Nature 438, 443-448 (2005).

5. Eldar, A. & Elowitz, M.B. Functional roles for noise in genetic circuits. Nature 467, 167-173 (2010).

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在人類細胞中建立正向自我調節迴路以應用至抑制細胞分裂之癌症療法

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