Patho-physiological Analysis of Radio-resistant Cancer Stem Cells

越来越多的证据表明，癌症含有自己的干细胞，称为癌症干细胞(CSCs)。一小部分细胞，称为侧群(SP)，已用流式细胞仪分析确定。SP细胞具有排除DNA结合染料Hcechst33342的能力，在许多正常组织中高度富含干细胞。因为肿瘤干细胞被认为是耐药的，癌症中的SP细胞可能含有肿瘤干细胞。我们最初检测了几个人甲状腺癌细胞系中SP细胞的存在。在ARO(0.25%)、FRO(0.1%)、NPA(0.06%)和WRO(0.02%)细胞中可见少量SP细胞，而TPC1细胞则未见。分选后，SP细胞在培养中同时产生SP细胞和非SP细胞。SP细胞的克隆形成能力明显高于非SP细胞。此外，SP的患病率依赖于培养中的细胞密度，这表明SP细胞在较低的细胞密度下优先存活。基因芯片实验显示不同的…与非SP细胞相比，SP细胞和非SP细胞之间的基因表达谱更高，与严厉相关的几个基因表达上调。然而，非SP细胞群中也含有在裸鼠体内致瘤的细胞，非SP细胞群产生了少量的SP细胞。这些结果表明，肿瘤干细胞样细胞部分但不完全富含SP群体。甲状腺激素受体(THR)广泛地调控细胞的生长、分化和代谢，其作用依赖于配体和辅因子来调节组织特异性基因的表达。鉴于THRs调控的基因种类繁多，以及THRs潜在影响的细胞过程的多样性，我们讨论了THRB(甲状腺激素受体β)在细胞辐射敏感性中的作用。另一方面，富含SP的细胞株THRB表达水平较低。通过腺病毒介导的基因传递，野生型和突变型THRB在几个细胞系中过表达，并在细胞暴露于伽马射线后检测它们的影响。野生型THRB降低内源性THRB低水平细胞系的克隆存活率，抑制其生长，并与辐射协同作用，降低增殖能力，促进细胞衰老。伴随这些变化的是细胞周期蛋白依赖蛋白的p21(CDKNIA、CIP1、WAF1)和p16(CDKN2A、TNK4a)抑制物的积聚和Rb(视网膜母细胞瘤蛋白)磷酸化的降低。突变型THRB具有辐射防护作用，可减轻辐射诱导的生长抑制和细胞衰老。这些结果提示THRB可能参与调节细胞的辐射敏感性和应激诱导的衰老，提示SP细胞的抗辐射特性与THRB的表达和功能有关。较少

There is increasing evidence that cancers contain their own stem-like cells called cancer stem cells(CSCs). A small subset of cells, termed side population(SP), has been identified using flow cytometric analysis. The SP cells have the ability to exclude the DNA binding dye, Hcechst33342, and are highly enriched for stem cells in many kinds of normal tissues. Because CSCs are thought to be drug resistant, SP cells in cancers might contain CSCs. We initially examined the presence of SP cells in several human thyroid cancer cell lines. A small percentage of SP cells were found in ARO(0.25%), FRO(0.1%), NPA(0.06%), and WRO(0.02%) cells but not TPC1 cells. After sorting, the SP cells generated both SP and non-SP cells in culture. The clonogenic ability of SP cells was significantly higher than that of non-SP cells. Moreover, the SP prevalence was dependent on cell density in culture, suggesting that SP cells preferentially survived at lower cell density. Microarray experiment revealed diffe … More rential gene expression profile between SP and non-SP cells, and several genes related to sternness were up-regulated. However, non-SP population also contained cells that were tumorigenic in nude mice, and non-SP cells generated a small number of SP cells. These results suggest that cancer stem-like cells are partly, but not exclusively, enriched in SP population.Thyroid hormone receptors(THRs) widely govern cell growth, differentiation and metabolism acting in a ligand-and cofactordependent manner to modulate tissue-specific gene expression. Given a large variety of genes regulated by THRs and multiplicity of cellular processes potentially influenced by THRs, we addressed the role of THRB(thyroid hormone receptor beta) in cellular radiosensitivity. On the other hand, SP-rich cell lines showed low level expression of THRB. Wild-type and mutant THRB were overexpressed in several cell lines using an adenovirus-mediated gene delivery and their effects were examined after cell exposure to gamma-rays. Wild-type THRB decreased clonogenic survival of the cell lines with low levels of endogenous THRB, retarded their growth and synergized with radiation in decreasing proliferative potential and promoting cellular senescence. These changes were accompanied by the accumulation of p21(CDKNIA, CIP1, WAF1) and p16(CDKN2A, TNK4a)inhibitors of cyclin-dependent kinases and by the decrease of Rb(retinoblastoma protein)phosphorylation. Mutant THRB produced a radioprotective effect, attenuated radiation-induced growth inhibition and cellular senescence. The results suggest that THRB may modulate cellular radiosensitivity and stress-induced senescence.These data is suggesting that radio-resistant property of SP cell is involved in THRB expression and its function. Less