SPECIFIC T CELL IMMUNITY TO MUTATED RAS PROTEIN

ras原癌基因的体细胞突变发生在大约20%的 人类恶性肿瘤 突变涉及单核苷酸交换 在密码子12或61内，其导致p21ras蛋白的表达 在残基12或61处具有单个取代的氨基酸。 初步 在小鼠中的研究已经表明，p21ras可以通过以下方式变得对T细胞具有免疫原性： 这是由于单个取代的氨基酸。 因此，p21ras蛋白 代表与转化相关的潜在肿瘤特异性抗原 事件，并被许多人分享。 在类似的研究中，我们已经表明，嵌合体的连接区， p210bcr-abl蛋白在慢性粒细胞白血病中表达， 同样具有免疫原性。 因此，通过表达的蛋白质的免疫原性可以降低。 异常癌基因不限于p21ras。 主要的感知问题 利用p21ras、p21ras、p210bcr-abl或其它类似蛋白作为靶点 它们是细胞内部的蛋白质。 t细胞并 不对整个蛋白质产生反应，而是对加工肽产生反应， 与MHC分子结合。 初步数据证实， p21ras蛋白片段可被抗原提呈细胞加工 (APC)并由II类MHC分子呈递，从而对 CD4 + T细胞。 CD4 + T细胞的体内治疗功效要求， p21 ras在肿瘤环境中被APC摄取，加工， 以足够的浓度提供，以刺激近端免疫 T细胞分泌参与直接和/或间接细胞溶解的细胞因子 机制等 目前，这些严格的条件已经在两个 p21ras特异性T细胞的鼠模型已被证明是 有效防止ras阳性肿瘤的生长。 突变的p21ras是肿瘤特异性抗原的观察结果提供了一个新的证据。 启动人类研究以确定是否 RAS特异性应答可以产生并在治疗上用于 治疗或预防ras阳性恶性肿瘤的复发。 第一 目的是确定携带ras阳性的患者是否 恶性肿瘤存在对异常p21ras的免疫应答。 最终，可能有必要对患者进行免疫接种， ras特异性T细胞。 目前的拨款建议进行研究 在进行人类免疫研究之前， 本建议的具体目标是：（1）确定是否 ras异常阳性肿瘤患者存在CD8 + T细胞 p21ras蛋白的异常启动;（2）确定患者是否 在异常ras阳性肿瘤中，存在针对 （3）检测正常人T细胞是否存在p21ras蛋白异常; 可以检测对异常p21ras具有潜在反应性的个体， 体外激活和扩增;以及（4）确定是否患有 异常ras阳性肿瘤产生特异性体液反应， 异常p21ras蛋白

Somatic mutations of ras proto-oncogenes occur in approximately 20% of all human malignancies. The mutations involve a single nucleotide exchange within codons 12 or 61 which result in the expression of a p21ras protein with a single substituted amino acid at residues 12 or 61. Preliminary studies in mice have shown that p21ras can become immunogenic to T cells by virtue of the single substituted amino acid. Thus, p21ras protein represents a potential tumor-specific antigen related to the transforming events and shared by many individuals. In similar studies, we have shown that the joining region of a chimeric protein (p210bcr-abl) which is expressed in chronic myelogenous leukemia is likewise immunogenic. Thus, the immunogenicity of proteins expressed by aberrant oncogenes is not limited to p21ras. The major perceived problem of using p21ras, p21ras, p210bcr-abl or other similar proteins as targets for T cell attack is that they are internal cellular proteins. T cells do not respond to whole protein, but rather respond to processed peptides bound to MHC molecules. Preliminary data validated that the mutated segment of p21ras protein can be processed by antigen presenting cells (APC) and presented by class II MHC molecules and thereby is immunogenic to CD4+ T cells. In vivo therapeutic efficacy of CD4+ T cells requires that p21ras be taken up by APC in the environment of tumor, processed and presented in sufficient enough concentration to stimulate proximate immune T cells to secrete cytokines involved in direct and/or indirect cytolytic mechanisms. At present, these stringent conditions have been met in two murine models in which p21ras specific T cells have been shown to be effective at preventing the growth of ras-positive tumors. The observation that mutated p21ras is a tumor-specific antigen provides a strong impetus for initiating human studies to determine whether ras-specific responses can be generated and utilized therapeutically to treat or prevent the recurrence of ras-positive malignancies. The first objective is to determine whether patients bearing ras-positive malignancies have existent immune responses to aberrant p21ras. Ultimately, it might be necessary to immunize patients to elicit ras-specific T cells. The current grant proposes to perfom the studies necessary prior to embarking upon human immunization studies. The specific aims of the current proposal are: (1) to determine whether patients with aberrant ras-positive tumors have existent CD8+ T cells primed to the aberrant p21ras protein; (2) to determine whether patients with aberrant ras-positive tumors have existent CD8+ T cells primed to the aberrant p21ras protein; (3) to determine whether T cells from normal individuals with potential reactivity to aberrant p21ras can be detected, activated and expanded in vitro; and (4) to determine whether patients with aberrant ras-positive tumors develop specific humoral responses to the aberrant p21ras protein.