Department of Biosciences, Bioanalytical Research Labs, University of Salzburg, A-5020 Salzburg, Austria.
Department of Biosciences, Cancer Cluster Salzburg, Molecular Cancer and Stem Cell Research, University of Salzburg, A-5020 Salzburg, Austria.
Cells. 2020 Jun 3;9(6):1397. doi: 10.3390/cells9061397.
Cancer stem cells (CSCs), a small subset of the tumor bulk with highly malignant properties, are deemed responsible for tumor initiation, growth, metastasis, and relapse. In order to reveal molecular markers and determinants of their tumor-initiating properties, we enriched rare stem-like pancreatic tumor-initiating cells (TICs) by harnessing their clonogenic growth capacity in three-dimensional multicellular spheroid cultures. We compared pancreatic TICs isolated from three-dimensional tumor spheroid cultures with nontumor-initiating cells (non-TICs) enriched in planar cultures. Employing differential proteomics (PTX), we identified more than 400 proteins with significantly different expression in pancreatic TICs and the non-TIC population. By combining the unbiased PTX with mRNA expression analysis and literature-based predictions of pro-malignant functions, we nominated the two calcium-binding proteins S100A8 (MRP8) and S100A9 (MRP14) as well as galactin-3-binding protein LGALS3BP (MAC-2-BP) as putative determinants of pancreatic TICs. In silico pathway analysis followed by candidate-based RNA interference mediated loss-of-function analysis revealed a critical role of S100A8, S100A9, and LGALS3BP as molecular determinants of TIC proliferation, migration, and in vivo tumor growth. Our study highlights the power of combining unbiased proteomics with focused gene expression and functional analyses for the identification of novel key regulators of TICs, an approach that warrants further application to identify proteins and pathways amenable to drug targeting.
癌症干细胞（CSCs）是肿瘤中具有高度恶性特性的一小部分，被认为是肿瘤起始、生长、转移和复发的原因。为了揭示其肿瘤起始特性的分子标志物和决定因素，我们利用三维多细胞球体培养中的克隆生长能力，富集了罕见的干细胞样胰腺起始肿瘤细胞（TICs）。我们将从三维肿瘤球体培养中分离出的胰腺 TIC 与在平面培养中富集的非起始肿瘤细胞（非-TICs）进行比较。采用差异蛋白质组学（PTX），我们在胰腺 TIC 和非 TIC 群体中鉴定了超过 400 种表达差异显著的蛋白质。通过将无偏见的 PTX 与 mRNA 表达分析和基于文献的促恶性功能预测相结合，我们提名两种钙结合蛋白 S100A8（MRP8）和 S100A9（MRP14）以及半乳糖结合蛋白 LGALS3BP（MAC-2-BP）作为胰腺 TIC 的潜在决定因素。随后进行的基于通路的分析和基于候选的 RNA 干扰介导的功能丧失分析表明，S100A8、S100A9 和 LGALS3BP 作为 TIC 增殖、迁移和体内肿瘤生长的分子决定因素具有重要作用。我们的研究强调了结合无偏见蛋白质组学与重点基因表达和功能分析以鉴定 TIC 的新关键调节因子的强大功能，这种方法值得进一步应用以鉴定可用于药物靶向的蛋白质和途径。
