AUTOACTIVATION OF COLON CANCER CELLS--TGF INTRACELL

在支持该项目的前一阶段，我们描述了 细胞内TGF α自分泌环。 具有细胞内 TGF α表达大量的细胞内前体TGF α， 相对于其他细胞，其处理速度异常缓慢。 因此，它们继续表达高细胞内水平的 非分裂、非循环状态下的TGF α，如静止状态 是由营养和生长因子缺乏引起的。 细胞内 自分泌活动的位置导致无法进入 这些细胞中的TGF α自分泌活性对TGF α中和 抗体和EGFtau阻断抗体。 然而，组成型TGF α 反义载体表达导致获得EGF依赖性。 反义转染的细胞不表达高水平的细胞内 TGF α表达和转录降低， 分裂国家。 它们类似于分化良好的生长因子 依赖性结肠癌细胞，因为这些细胞还需要 外源EGF用于克隆生长和从静止释放。 他们还 显示低水平的细胞内TGF α和降低的 非分裂状态下的TGF α。 这些结果使我们假设TGF α作为一种 自分泌因子，以帮助克隆生长或逃逸的启动 从静止期结肠癌细胞和它的内部位置， 一些细胞由于不适当地调节细胞的生长而提供生长调节优势， 在非周期性生长状态如静止期高表达。 是 进一步假设该因子不具有刺激功能 为指数增长的细胞。 此外，最近还发现， 其他EGF相关肽，双调蛋白（AR）和cripto（CR）， 也是结肠癌中的自分泌调节因子。 我们假设 这些因素将与TGF α在控制 功能的表达和时间控制。 这些假设将是 测试人： 1. 确定指数和非指数型中TGF α的自分泌功能 划分增长监管国家。 2. 确定TGF α， AR和CR。 3. 测定AR的自分泌功能。 4. 测定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.