平行演化癌細胞之紡錘絲長度演變與適應

Abstract

癌症的起源在癌症研究中一直是尚未被釐清的一個問題。目前癌症被認為是由一個擁有不正常突變基因的細胞分裂而來，因為突變使這些細胞更容易從原位轉移或侵略到身體的其他組織或器官。基因突變帶來性狀改變，其中存在對癌細胞分裂與擴散有益的突變，擁有有益突變的癌細胞相較於其他沒有此突變基因的癌細胞，會更容易在整體的癌細胞族群中分裂與擴散，因此此突變基因便會在整個演化過程中被保留下來。 基於癌細胞的基因不穩定性，有研究指出癌細胞也如同自然界的其他個體會進行演化。肺腺癌細胞 CL1-0和CL1-5為一對有名的癌症演化案例，CL1-0取自病人腫瘤檢體，經過實驗室侵略試驗篩選出惡化程度更高的子細胞株CL1-5。CL1-5無論在細胞型態或是基因層級上都與CL1-0其母細胞株有所不同，CL1-5細胞內的紡錘絲型態也和CL1-0之間存在差異，且發現其紡錘絲長度與其細胞大小呈正相關。 在這本論文中，我們討論了紡錘絲型態是否會隨著癌症細胞演化而跟著演化，我們在不同的癌細胞株中平行地進行侵略試驗（如HeLa, U2OS, HCT116和A549），將每次篩選到的細胞保存以進行後續代數之間的比較。我們發現紡錘絲在某些經過演化的癌細胞株中有延長的趨勢，動力蛋白相關基因如KIF11也有較高的表現。但我們同時發現癌細胞間的異質性非常高，另外，篩選出的惡性子細胞株其紡錘絲也會隨著時間慢慢回到原本的長度，這部分尚需要更多的實驗去驗證許多可能的假設。

In cancer literature, the origin of cancer has long been an issue for scientists to elucidate. To date, consensus is that cancer arose from an ancestral cell that bore abnormal mutation in its genome. This led to dramatic change like higher migration or invasiveness ability. Those mutations, so called beneficial mutations, let ancestral cell in population outcompeted others and thus developed into tumor mass. It has also been found that cancer cells could evolve as other individuals in nature. A well-known example is CL series cell lines, lung adenocarcinoma cells derived from patient’s tumor and formed stable CL1-0 cell line, then followed by invasion assay to select more metastatic subclones within original cell line. In the comparison of CL1-0 and more metastatic CL1-5 subclone cell line, it showed both morphological and genomic differences. Spindles had been found distinguished between these two cell lines, in which spindles were lengthened in CL1-5 and proportional to its cell size. In this thesis, we argued that whether spindle lengthening in metastatic cells is a general phenomenon among multiple cancer cell lines. By applying invasion assay on cell lines, like HeLa, U2OS, HCT116 and A549, we parallelly evolved cancer cells and froze cells in time series for further investigation. Spindles have lengthened in some cancer cell lines after repeated selection process, and gene expression like KIF11, encoding for motor protein, has also elevated in evolved sub-cell-lines. However, we figured that heterogeneity is high among cancer cells. Lengthened spindles in metastatic cells would gradually shrink to its original length with time. There are many possibilities that lead to this situation which need further experiments and research to clarify.