{F18}paclitaxel: an in vivo marker for MDR in tumors

描述（由申请人提供）： 膜泵P-糖蛋白（Pgp）的过度表达导致多药耐药（MDR），这是癌症治疗失败的常见原因。Pgp能主动将药物从肿瘤细胞中清除。紫杉醇是一种常用的化疗药物，MDR通常使其使用复杂化。NIH的PET部门已经开发出一种有效的放射合成[18 F]紫杉醇（FPAC），这是Pgp泵的底物。由于[18 F]是正电子发射体，[18 F]FPAC的体内动力学可以使用正电子发射断层扫描（PET）测量。预期通过测量FPAC在肿瘤中的动力学，可以估计Pgp在体内的功能。该提案旨在获得初步证据，证明[18 F]FPAC PET生物分布和PET动力学成像参数对应于小鼠异种移植模型中测量的Pgp表达。在两种人上皮癌细胞系（一种药物敏感，另一种药物耐药）中进行的细胞存活研究将用于确定细胞对紫杉醇的反应。然后将进行FPAC流入和流出研究，以在这些细胞系中建立体外FPAC动力学。这些相同的细胞系将用于在裸鼠中建立双侧胁腹肿瘤异种移植模型。使用该小鼠异种移植模型，将进行FPAC生物分布和PET动力学成像研究。将对Pgp进行免疫组织化学（IHC）染色，以定量这些肿瘤中的Pgp蛋白量。由于Pgp的存在并不意味着功能性，因此有必要确定FPAC的肿瘤外排是否也对应于MDR表型。这将通过在用未标记治疗剂量的紫杉醇治疗之前和之后在小鼠异种移植物模型中进行FPAC PET成像和生物分布研究来完成。将测量处理后异种移植物大小的变化，并与FPAC PET成像和生物分布结果进行比较。由于MDR是可诱导的，因此宿主与异种移植物的相互作用或暴露于紫杉醇或FPAC可能导致MDR表达，这将混淆上述研究的结果。其他ATP结合盒（ABC）转运蛋白也可能导致MDR。将对所有肿瘤标本进行专门的ABC微阵列技术分析。该微阵列探测48个ABC转运蛋白的基因表达。微阵列结果将与上述结果结合使用，为FPAC用作Pgp引起的MDR的体内标记物提供初步证据。

DESCRIPTION (provided by applicant): Over-expression of the membrane pump P-glycoprotein (Pgp) results in multidrug resistance (MDR), a common cause of cancer treatment failure. Pgp actively removes drugs from the tumor cells. Paclitaxel is a commonly used chemotherapeutic agent, and MDR often complicates its use. The PET department at the NIH has developed an efficient radiosynthesis for [18F] paclitaxel (FPAC), which is a substrate of the Pgp pump. Because [18F] is a positron emitter, the in vivo kinetics of [18F]FPAC can be measured using positron emission tomography (PET). It is expected that, by measuring the kinetics of FPAC in tumors, the function of Pgp in vivo can be estimated. This proposal intends to obtain preliminary evidence that [18F]FPAC PET biodistribution and PET kinetic imaging parameters correspond to the measured expression of Pgp in a mouse xenograft model. Cell survival studies in two human epithelial cancer cell lines, one drug sensitive and the other drug resistant, will be used to determine the cellular response to paclitaxel. FPAC influx and efflux studies will then be performed to establish in vitro FPAC kinetics in these cell lines. These same cell lines will be used to establish a bilateral flank tumor xenograft model in nude mice. Using this mouse xenograft model, FPAC biodistribution and PET kinetic imaging studies will be performed. Immunohistochemical (IHC) staining for Pgp will be performed to quantitate the amount of Pgp protein in these tumors. Since the presence of Pgp does not imply functionality, it is necessary to determine if tumor efflux of FPAC also corresponds to MDR phenotype. This will be done by performing FPAC PET imaging and biodistribution studies in the mouse xenograft model before and after treatment with unlabeled therapeutic doses of paclitaxel. The change in xenograft size following treatment will be measured and compared to the FPAC PET imaging and biodistribution results. Because MDR is inducible, it is possible that host interaction with the xenograft or exposure to paclitaxel or FPAC may result in MDR expression that will confound the results of the above studies. Other ATP binding cassette (ABC) transporters may also be responsible for MDR. A dedicated ABC microarray-technology analysis will be performed on all tumor specimens. This microarray probes for the gene expression of 48 ABC transporters. Microarray results will be used in combination with those described above to provide preliminary evidence for FPAC's use as an in vivo marker for MDR caused by Pgp.