AUTOACTIVATION OF COLON CANCER CELLS--TGF INTRACELL

在上一期对该项目的支持中，我们描述了一个 细胞内TGFα自分泌环路。细胞内有一个 转化生长因子α表达高水平的细胞内前体转化生长因子α 与其他细胞相比，处理速度异常缓慢。 因此，它们继续在细胞内表达高水平的 在非分割、非循环状态中的TGFα，例如静止状态 由营养和生长因子缺乏所产生。细胞内 自分泌活动的位置导致无法访问 这些细胞中的转化生长因子α对转化生长因子α的中和作用 抗体和EGFtau阻断抗体。然而，结构性的TGFAlpha 反义载体表达导致EGF依赖的获得。 反义转基因细胞不表达高水平的细胞内 TGFα和SHO降低非小鼠肾组织中TGFα的表达和转录 分裂的州。它们类似于分化良好的生长因子 在这方面依赖结肠癌细胞，因为这些细胞也需要 外源EGF用于克隆生长和从静止中释放。他们也 显示出细胞内低水平的转化生长因子α和表达减少的 非分裂状态下的TGFAlpha。 这些结果使我们假设TGFAlpha作为一种 帮助启动克隆生长或逃逸的自分泌因子 从结肠癌细胞的静止状态以及它在体内的位置 一些细胞提供了生长调节优势，因为不适当的 在静止期等非周期生长状态中高表达。它是 进一步假设该因子不具有刺激功能 对于指数级增长的细胞。此外，最近还发现了它 其他与EGF相关的多肽，双调节蛋白(AR)和Cripto(CR)，是 结肠癌中也存在自分泌调节因子。我们假设 这些因素将与TGFAlpha在控制 功能的表达和时间控制。这些假设将是 测试人员： 1.确定TGFα的指数自分泌函数和非指数自分泌函数 不同的增长监管州。 2.确定TGFα表达调控的相互关系， AR和CR。 3.确定AR的自分泌功能。 4.确定CR的自分泌功能。

In the previous period of support for this project we characterized an intracellular TGFalpha autocrine loop. Cells with an intracellular TGFalpha express high amounts of intracellular precursor TGFalpha which has an abnormally slow rate of processing relative to other cells. Consequently, they continue to express high intracellular levels of TGFalpha in non-dividing, non-cycling states such as the quiescent state generated by nutrient and growth factor deprivation. The intracellular location of the autocrine activity results in the inaccessibility of TGFalpha autocrine activity in these cells to TGFalpha neutralizing antibodies and EGFtau blocking antibodies. However, constitutive TGFalpha anti-sense vector expression results in the acquisition of EGF dependency. Anti-sense transfected cells do not express high levels of intracellular TGFalpha and show decreased TGFalpha expression and transcription in non- dividing states. They are similar to well-differentiated, growth factor dependent colon carcinoma cells in this regard as these cells also require exogenous EGF for clonal growth and release from quiescence. They also show low levels of intracellular TGFalpha and reduced expression of TGFalpha in non-dividing states. These results have led us to hypothesize that TGFalpha acts as an autocrine factor to aid in the initiation of clonal growth or the escape from quiescence in colon carcinoma cells and that its internal location in some cells provides a growth regulatory advantage due to inappropriately high expression in non-cycling growth states such as quiescence. It is further hypothesized that the factor does not have a stimulatory function for exponentially growing cells. Moreover, it has recently been found that other EGF related peptides, amphiregulin (AR), and cripto (CR), are also autocrine regulatory factors in colon cancer. We hypothesize that these factors will interrelate with TGFalpha in terms of control of expression and temporal control of function. These hypothesizes will be tested by: 1. Determining the autocrine function of TGFalpha in exponential and non- dividing growth regulatory states. 2. Determine interrelationship of control of expression among TGFalpha, AR and CR. 3. Determine the autocrine function of AR. 4. Determine the autocrine function of CR.