Multipotent mesenchymal stem cell-like cells in pancreatic tumorigenesis

描述（由申请人提供）：在过去的几年中，正常宿主细胞在功能上促进肿瘤的发生和发展已经变得很明显。虽然已经有大量的研究表明骨髓来源的祖细胞和支持细胞是肿瘤血管生成和进展的关键贡献者，但几乎没有任何关于潜在驻留在肿瘤内的干细胞群的功能意义的研究。我们最近在正常胰岛和转基因小鼠模型Rip1Tag2的胰岛肿瘤中发现了一个多能间充质干细胞样细胞（MPMSCs）群体。这种细胞表现出间充质表面标记物的表达，并且在悬浮生长时具有高度的自我更新能力——这种能力只有干细胞才具备。MPMSC细胞在体外可分化为周细胞、内皮细胞和神经元。有趣的是，我们发现MPMSCs并非来自骨髓，而是可能存在于胰岛中，并在胰腺肿瘤进展过程中被激活。我推测，虽然MPMSC细胞在正常组织中表现出多能性，但它们可能在肿瘤环境中被引导主要产生血管细胞（周细胞和内皮细胞），以支持新血管的形成，并抑制其他细胞类型（如神经元）的形成。Rip1Tag2转基因小鼠模型提供了一个独特的平台来研究不同疾病进展阶段的MPMSCs，因为它从朗格汉斯胰岛的正常β细胞开始，经过两个不同的癌前阶段到高度血管化的大腺瘤和浸润性癌的多步骤途径发展为胰岛细胞癌。由于高胰岛素血症和肿瘤负荷的共同作用，小鼠在14到15周之间死亡。为了验证假设，我建议从胰岛癌变的不同阶段分离MPMSCs，检测它们在肿瘤发生发展过程中是否被激活、数量增加并优先分化为周细胞和内皮细胞。我还将在两种小鼠肿瘤模型的肿瘤增殖过程中，用荧光跟踪MPMSCs进一步评估这些表型。我将MPMSC细胞与肾包膜下的2TC3细胞（从Rip1Tag2小鼠中分离的肿瘤细胞）和真皮内的黑色素瘤（B16细胞）共同注射。此外，我打算确定在正常胰岛和胰腺肿瘤发生过程中决定MPMSCs分化命运的潜在信号通路。虽然有许多信号通路和因素值得评估，但我决定将重点放在PDGFR2和CD271/p75作为MPMSC向周细胞分化的潜在调节因子上。

DESCRIPTION (provided by applicant): Over the past several years it has become evident that normal host cells functionally contribute to tumor initiation and progression. While there has been a wealth of studies eliciting bone marrow-derived progenitor and support cells as critical contributors to tumor angiogenesis and progression, hardly anything is known about the functional significance of stem cell populations that potentially reside within the tumor. We recently discovered a population of multipotent mesenchymal stem cell-like cells (MPMSCs) in normal pancreatic islets as well as in pancreatic islet tumors of the transgenic mouse model Rip1Tag2. This cells display expression of mesenchymal surface markers and have high self-renewal capacity as they grow in suspension as spheres - the abilities which only stem cells posses. Also MPMSC cells can differentiate in vitro into pericytes, endothelial cells and neurons. Interestingly, we found that MPMSCs recruited to tumor not from bone marrow, but probably reside within pancreatic islets and become activated during pancreas tumor progression. I hypothesized that while MPMSC cells exhibit multipotentiality in normal tissue, they might be steered to predominantly produce vascular cells (pericytes and endothelial cells) in a tumor setting to support neovascularization and repress the formation of other cell types such as neurons. The Rip1Tag2 transgenic mouse model provides a unique platform to study MPMSCs at distinct stages of disease progression as it develops pancreatic islet cell carcinomas in a multi-step pathway arising from normal beta cells in the islets of Langerhans through two distinct premalignant stages to highly vascularized large adenomas and invasive carcinomas. The mice die between 14 and 15 weeks as a combined effect of hyperinsulinemia and tumor burden. In order to test hypothesis I propose to isolate MPMSCs from different stages of pancreatic islet carcinogenesis and test whether they become activated, increase their numbers and preferentially differentiate into pericytes and endothelial cells during the course of tumor development and progression. I will also further assess these phenotypes with fluorescently-tracked MPMSCs during tumor propagation of two mice tumor models. I will co-inject MPMSC cells with 2TC3 cells (tumor cells isolated from Rip1Tag2 mice) under the kidney capsule and with melanoma (B16 cells) into dermic. Also I intended to identify the underlying signaling circuit that determines the differentiation fate of MPMSCs in normal pancreatic islets and during pancreatic tumorigenesis. While there are many signaling pathways and factors that would be worthwhile and important to assess, I decided to focus on PDGFR2 and CD271/p75 as a potential regulators of MPMSC differentiation into pericytes.