REGULATION OF PGP1 MRNA IN MULTIDRUG-RESISTANT CELLS

多药耐药（MDR）仍然是治疗肿瘤的主要障碍之一。 化疗成功虽然MDR的实验室研究和 在过去的几年里，临床上的进展速度令人印象深刻。 多年来，几个关键问题仍然没有答案。知之甚少 调节编码P-糖蛋白的基因的机制， 假定的药物外排泵，其过表达，至少部分， 负责抵抗性表型。我们的实验室正试图 在正常细胞发育过程中定义这些机制， 分化以及在发展和维护的过程中， 多药耐药表型。 我们建议研究这些机制， 首先仔细分析了 仓鼠pgp 1基因的组成型表达。我们最近 转录起始位点差异利用的鉴定 药物敏感细胞和耐药细胞之间的关系表明， 在没有基因扩增的情况下， 放线菌素D（ActD）选择的细胞;我们研究的长期目标是 定义这样的机制，并确定转录或后- pgp 1表达增加的转录因子 MDR细胞中的基因。 具体目标1中概述的实验旨在确定 DNA序列元件和蛋白质因子所需的组成 仓鼠pgp 1基因的表达。最后，我们希望能找出 参与组织特异性表达的DNA和蛋白质因子 pgp 1，使用仓鼠肝脏和肝细胞作为模型系统。 此外，委员会认为， 我们将研究差异利用的机制 pgp 1转录起始位点。在具体目标2中，我们将进一步 通过检测pgp 1基因的转录调控， 在无细胞转录系统中表达，其长期目标是 在体外重建组织特异性转录。在具体目标3中， 我们打算研究转录后机制在 在调节药物敏感性与药物敏感性中的pgp 1表达中起作用， 抗性细胞

Multidrug resistance (MDR) remains one of the major obstacles to successful chemotherapy. Although the study of MDR in the laboratory and in the clinic has progressed at an impressive rate within the past several years, several critical questions remain unanswered. Little is known about the mechanism(s) regulating the genes that encode P-glycoprotein, the putative drug efflux pump whose overexpression is, at least in part, responsible for the resistant phenotype. Our laboratory is attempting to define these mechanisms in normal cells during development and differentiation as well as during the development and maintenance of the multidrug-resistant phenotype. We propose to examine these mechanisms, beginning with a careful dissection of the components required for the constitutive expression of the hamster pgp1 gene. Our recent identification of a differential utilization of transcription start sites between drug-sensitive and drug-resistant cells suggests a mechanism for the overexpression of pgp1 in the absence of gene amplification in actinomycin D (ActD)-selected cells; a long-range goal of our studies is to define such a mechanism and determine the transcriptional or post- transcriptional factors underlying the increased expression of the pgp1 gene in MDR cells. The experiments outlined in Specific Aim 1 are directed at defining the DNA sequence elements and protein factors required for the constitutive expression of the hamster pgp1 gene. Ultimately, we hope to identify the DNA and protein factors involved in the tissue-specific expression of pgp1, using hamster liver and hepatocytes as a model system. Furthermore, we will investigate the mechanism underlying the differential utilization of pgp1 transcription initiation sites. In Specific Aim 2, we will further dissect the transcriptional regulation of the pgp1 gene by examining its expression in a cell-free transcription system, with a long-range goal of reconstituting tissue-specific transcription in vitro. In Specific Aim 3, we propose to investigate the role that post-transcriptional mechanisms play in the regulation of pgp1 expression in drug-sensitive vs. drug- resistant cells.