利用不同培養液和聚合物塗覆之基材培養大腸直腸癌細胞來增加或維持幹細胞的特性

Abstract

癌細胞內有一部分特異細胞具有自我更新的能力、有相對高的抗藥性和抗輻射能力，而且較容易形成腫瘤，它們被稱為癌症幹細胞，與一般幹細胞無異，能分化出比較下游的細胞。我們利用目前常用的幹細胞標誌表現來探討大腸直腸癌細胞的幹性，例如表面抗原標誌CD133、CD44以及與自我更新相關的轉錄因子Oct4、SOX2、Nanog。除此之外我們試著尋找特殊的細胞培養條件，期望能藉此增加幹細胞的表現量，培養條件分為兩類，一為使用不同的細胞培養液，加入生長因子bFGF和EGF；一為在細胞培養盤上塗覆不同之親水性聚合物基材，令細胞呈球狀聚集。然而雖然不同培養條件能有效改變各個幹細胞標誌的表現量，卻似乎沒有規律，只能得到培養環境對癌症細胞特性的影響扮演著重要角色。 一般幹細胞的特性認為其下游的細胞不容易反分化回幹細胞，但越來越多證據顯示，癌細胞內雖然有不同蛋白和基因表現的細胞，他們之間卻可以依照機率互相轉換，並在一段時間達成平衡，因此被用表面抗原標誌篩選出來的細胞，培養一段時間後應會達到一固定比例，因此我們利用不同的培養條件培養以CD133篩選出來的大腸直腸癌細胞，觀察是否能夠維持其表現量，發現無論何種條件均 會使得CD133表現量達到平衡狀態，只是平衡點不同，若以生長因子及球狀培養方式則能維持較高CD133表現，一般培養條件則否，而沒有表現CD133的細胞則會因為這兩種培養環境而增加其表現量，證明兩種細胞間能夠互相轉換，因此我們應用了數學上的馬可夫矩陣來描述細胞間的轉換機率，並預測未來表現量的變化，理論上，我們發現無論大腸直腸癌細胞的CD133表現比例多少，只要培養環境相同，就能夠達到一固定平衡，因此再次說明培養環境對癌症細胞特性的影響扮演著重要角色。

A growing body of observations indicate that, only a minority population of cells within a tumor possess the capacity to undergo self-renewal and to cause the heterogeneous linage of cancer cells that comprise the tumor. This functional subset of cells operationally defined as the cancer stem cell is reside at the apices of hierarchies and differentiate into non-stem progeny in a unidirectional manner. In our study, we chose CD133 and other stem cell markers, which are often been used to identified cancer stem cell on colorectal cancer to demonstrate the stemness of the cells. Additionally, we try to find out a condition to enhance the cancer stem cell properties. It seems that the conditions we used caused distinct alteration and still did not find out a rational conclusion in different cells Even though the definition of cancer stem cell described above. More and more studies stated that the cell-state of cancer can convert into each other randomly and can give rise to equilibrium over time after sorting. In our study, the expression level of surface marker, CD133, in human colorectal cancer can be modulated plastically in various cell culture conditions. We utilized Markov model to establish the transition probabilities between cells. The evidence demonstrates the probability for CD133 negative cells can convert into positive ones and will give rise to equilibrium over time. Moreover, we can use the transition probabilities and the population of cells in the beginning to predict cell-state dynamics over time. We find out that even if the population of CD133+ cells are different, it will give rise to the same equilibrium state, which means that the culture condition plays important role in cell properties.