Improving Radiation Therapy For Pancreatic Cancer

 描述(申请人提供)：放射治疗在胰腺导管腺癌(PDAC)的治疗中起着关键作用。然而，由于胰腺癌干细胞(PCSC)对电离辐射具有抵抗力，它面临着挑战。此外，最近的一项发现表明，辐射可以将非干细胞癌细胞重新编程为癌症干细胞，这与我们的发现一致，即IPCSC。令人信服的证据表明，表达高水平乙醛脱氢酶1(ALDH1)的PDAC细胞是PCSC/IPCSC。在过去，我们证明了细胞毒性T细胞(CTL)在体外和体内都能特异性识别ALDH1A1亚型的表位，从而消除ALDHbright细胞。然而，过继T细胞免疫治疗的临床适用性受到HLAI类限制，需要使用各种方法体外扩增自体或同种异体T细胞。为了克服CTL靶向ALDHbright细胞的局限性，我们测试了使用双硫兰(DSF)靶向PCSC的新方法。DSF是一种二硫代氨基甲酸酯，是FDA批准的ALDH抑制剂，用于治疗酒精中毒。它对PDAC细胞的毒性已被证明是通过与必需的微量元素铜结合形成DSF/铜络合物而增强的。我们最近利用PDAC细胞株发现：i)PCSC在体外分次照射后两天增加；ii)DSF/Cu在治疗间隙期间耗尽PCSC，并在体外取消受照射细胞的球体形成；iii)DSF/Cu下调受照射的PDAC细胞中关键的肿瘤干细胞途径Wnt途径，以及iv)DSF/Cu阻断辐射诱导的干细胞干基因的重新表达。这些发现为我们的中心假设提供了理论基础，即DSF/Cu耗尽了先前存在的PCSC和辐射诱导的PCSC，从而导致放射治疗疗效的显着提高。在AIM1中，我们将确定DSF/Cu在体外和体内都能消除PCSC和IPCSC。在AIM2中，我们将检验RT联合DSF/Cu在新的佐剂环境中使用异种和同基因胰腺肿瘤可以有效地消除干细胞和非干细胞PDAC细胞。在AIM3中，我们将在异种和同基因-PDAC小鼠模型系统中比较DSF/Cu、RT和5-FU(5-FU)的组合与传统的由RT和5-FU组成的新辅助放化疗的疗效。在拟议的研究结束时，我们将评估DSF/Cu作为既有PSCs/IPSCs的细胞毒剂和IPCSC生成的阻滞剂，了解DSF/Cu提高放化疗疗效的机制(S)，并结合FDA批准的药物DSF和营养补充剂葡萄糖酸铜，为提高放化疗疗效的新型新辅助疗法奠定基础。

 DESCRIPTION (provided by applicant): Radiation therapy plays a key role in pancreatic ductal adenocarcinoma (PDAC) treatment. However, it faces challenges from the fact that pancreatic cancer stem cells (PCSC) are resistant to ionizing radiation. Moreover, a recent finding indicates that radiation can reprogram nonstem- cancer cells into cancer stem cells, which is in agreement with our finding, namely iPCSC. Compelling evidence show that PDAC cells in expressing elevated levels of aldehyde dehydrogenase 1 (ALDH1), ALDHbrightcells, are PCSC/iPCSC. In the past, we demonstrated that cytotoxic T cells (CTL) specifically recognizing an epitope from the ALDH1A1 isoform eliminate ALDHbright cells in vitro and in vivo. However, the clinical applicability of adoptive T cell-based immunotherapy is limited by HLA class I restriction and requires ex vivo expansion of autologous or allogeneic T cells using a variety of methodologies. To overcome the limitations of CTL-targeting of ALDHbright cells, we tested the novel approach of using disulfiram (DSF) to target PCSC. DSF is a dithiocarbamate and an FDA-approve inhibitor of ALDH for treatment of alcoholism. Its toxicity to PDAC cells has been shown to be enhanced by the binding of the essential trace element copper (Cu++) to form DSF/Cu complexes. We found recently using PDAC cell lines that: i) PCSC increased two days after in vitro fractionated irradiation; ii) DSF/Cu depleted PCSC during the treatment gap, and abolished in vitro sphere formation of irradiated cells; iii) DSF/Cu downregulated Wnt pathway, a key cancer stem cell pathway, in irradiated PDAC cells, and iv) DSF/Cu blocked radiation induced re-expressing mRNA of stemness genes. These findings provide the rationale for our central hypothesis that DSF/Cu depletes pre-existing PCSC and radiation-induced PCSC which results in significant increases in the efficacy of radiation therapy. In Aim1, we will determine that DSF/Cu eliminates both PCSC and iPCSC in vitro and in vivo. In Aim2, we will examine that RT combined with DSF/Cu can effectively eliminate stem- and nonstem- PDAC cells in a neoadjuvant setting using xeno- and syngeneic- pancreatic tumors in mice. In Aim3, we will compare the efficacy of combination of DSF/Cu, RT and 5-Fluorouracil (5-FU), a commonly used radiosensitizer for PDAC vs conventional chemoradiation consisting of RT and 5-FU in a neoadjuvant setting in xeno- and syngeneic- PDAC mouse model systems . At the conclusion of the proposed studies, we will have evaluated DSF/Cu as a cytotoxic agent of pre-existing PSCS/iPSCS and as a blocker of generation of iPCSC, obtained knowledge of the mechanism(s) by which DSF/Cu enhances efficacy of radiation and chemoradiation therapy, and formed the foundation of a novel neoadjuvant therapy for improved efficacy of radiation and chemoradiation by combination with a FDA approved drug DSF and a nutrition supplement Copper gluconate.