Self-Renewal and Pluripotency Acquired through Somatic Reprogramming to Human Cancer Stem Cells

Human induced pluripotent stem cells (iPSCs) are reprogrammed by transient expression of transcription factors in somatic cells. Approximately 1% of somatic cells can be reprogrammed into iPSCs, while the remaining somatic cells are differentially reprogrammed. Here, we established induced pluripotent cancer stem-like cells (iCSCs) as self-renewing pluripotent cell clones. Stable iCSC lines were established from unstable induced epithelial stem cell (iESC) lines through re-plating followed by embryoid body formation and serial transplantation. iCSCs shared the expression of pluripotent marker genes with iPSCs, except for REX1 and LIN28, while exhibited the expression of somatic marker genes EMP1 and PPARγ. iESCs and iCSCs could generate teratomas with high efficiency by implantation into immunodeficient mice. The second iCSCs isolated from dissociated cells of teratoma from the first iCSCs were stably maintained, showing a gene expression profile similar to the first iCSCs. In the first and second iCSCs, transgene-derived Oct4, Sox2, Klf4, and c-Myc were expressed. Comparative global gene expression analyses demonstrated that the first iCSCs were similar to iESCs, and clearly different from human iPSCs and somatic cells. In iCSCs, gene expression kinetics of the core pluripotency factor and the Myc-related factor were pluripotent type, whereas the polycomb complex factor was somatic type. These findings indicate that pluripotent tumorigenicity can be conferred on somatic cells through up-regulation of the core pluripotency and Myc-related factors, prior to establishment of the iPSC molecular network by full reprogramming through down-regulation of the polycomb complex factor.

人类诱导多能干细胞（human induced pluripotent stem cells，iPSCs）可通过在体细胞中瞬时表达转录因子实现重编程。仅约1%的体细胞可被重编程为iPSCs，其余体细胞则发生异常重编程。本研究中，我们构建了诱导多能癌干细胞样细胞（induced pluripotent cancer stem-like cells，iCSCs），其为可自我更新的多能细胞克隆。稳定的iCSC细胞系可从不稳定的诱导上皮干细胞（induced epithelial stem cell，iESC）细胞系中获得：先进行细胞再接种，随后形成拟胚体，再经连续移植。iCSCs与iPSCs共享多能标志物基因的表达谱，仅REX1与LIN28除外；同时，iCSCs可表达体细胞标志物基因EMP1与PPARγ。iESCs与iCSCs均可通过植入免疫缺陷小鼠体内，高效形成畸胎瘤。从第一代iCSCs形成的畸胎瘤解离细胞中分离得到的第二代iCSCs可稳定传代，其基因表达谱与第一代iCSCs相似。在第一代与第二代iCSCs中，均表达转基因来源的Oct4、Sox2、Klf4及c-Myc。全基因表达谱比较分析显示，第一代iCSCs与iESCs相似，且与人类iPSCs及体细胞存在显著差异。在iCSCs中，核心多能性因子与Myc相关因子的基因表达动力学呈多能型，而多梳复合体因子则呈体细胞型。上述研究结果表明：在通过下调多梳复合体因子完成完全重编程以建立iPSCs分子网络之前，可通过上调核心多能性因子与Myc相关因子，使体细胞获得多能性致瘤性。