The side population of human pancreatic cancer expresses cancer stem cell-associated genes

Purpose: To explore the side population (SP) in pancreatic ductal adenocarcinoma (PDAC) for its gene expression profile and its association to cancer stem cells (CSC) and to evaluate the value of genes from its gene signature on patient survival. Experimental design: Side and main population (MP) cells were isolated from 11 human PDAC resection specimens using fluorescence-activated cell sorting (FACS) after Hoechst incubation. Total RNA was extracted for whole-genome analysis. A gene signature for the purified SP (pSP; depleted from immune/endothelial CD45+/CD31+ cells) was developed and validated with the nCounter system on expression data of 78 primary PDAC using Cox regression analyses for disease-free and overall survival. Results: An SP was identified in all PDAC samples. Whole-genome expression profiling of pSP revealed upregulation of genes related to therapy-resistance and of CSC-associated genes and pathways. A pSP signature of 32 up- or downregulated genes was capable of discriminating SP from MP in an independent set of 10 PDAC samples, and some contributing genes had a prognostic value in a separate series of 78 patients who underwent surgery for PDAC. Conclusion: Pancreatic cancer contains an SP with chemo-resistant and CSC-associated molecular characteristics. Genes from a newly defined pSP gene signature are related to survival of patients who undergo surgical resection for pancreatic cancer, and might therefore represent potential therapeutic targets. Microarray analysis was performed on SP and MP samples from 11 different human PDAC samples.

研究目的：探究胰腺导管腺癌（pancreatic ductal adenocarcinoma, PDAC）中侧群细胞（side population, SP）的基因表达谱，及其与癌症干细胞（cancer stem cells, CSC）的关联，并评估该细胞的基因特征中相关基因对患者生存的预测价值。实验设计：经Hoechst染色孵育后，采用荧光激活细胞分选术（fluorescence-activated cell sorting, FACS）从11例人类PDAC手术切除标本中分离侧群细胞与主群细胞（main population, MP）。提取总RNA进行全基因组表达分析，并采用微阵列分析（microarray analysis）技术完成相关检测。构建纯化后侧群细胞（purified SP, pSP，已去除免疫/内皮源性CD45+/CD31+细胞）的基因特征，随后采用nCounter系统，通过Cox回归分析对78例原发性PDAC患者的表达数据进行无病生存期与总生存期分析，以验证该基因特征。实验结果：所有PDAC样本中均检测到侧群细胞。pSP的全基因组表达谱分析显示，与治疗耐药相关的基因及癌症干细胞相关基因、信号通路均呈上调表达。本研究构建的含32个差异表达基因的pSP特征模型，可在10例独立PDAC样本队列中有效区分SP与MP，且部分特征基因在78例行PDAC手术切除的患者队列中具有预后预测价值。研究结论：胰腺癌中存在具有化疗耐药及癌症干细胞相关分子特征的侧群细胞。本研究新定义的pSP基因特征中的相关基因与胰腺癌手术切除患者的生存情况显著相关，有望成为潜在的治疗靶点。