Oct4在干细胞和肿瘤细胞中的表达

干细胞按分化能力分为全能性、多能性和专能性干细胞。Oct4是全能性或多能性干细胞标记物,在胚胎干细胞、胚胎生殖细胞和胚胎／生殖细胞肿瘤中阳性表达,但在分化的组织中均表达降低或消失,提示其在胚胎干细胞、生殖细胞和胚胎／生殖肿瘤中的表达与这些细胞的多能性分化特性密切相关。在成体组织和体细胞肿瘤中亦发现Oct4阳性表达。迄今为止,Oct4在成体组织中的表达主要局限于具有干细胞特性的细胞,如皮肤基底细胞层中的个别细胞、乳腺干细胞和胃干细胞等。本文简要综述Oct4在胚胎干／生殖细胞、成体和肿瘤组织中表达的研究现状,并对其在成体肿瘤中的表达及与肿瘤干细胞的关系进行讨论。     

Enrichment of Oct3/4‐positive cells from a human bronchial epithelial cell line

Most adult stem cells are in the G0 phase of the cell cycle, accounting for only a small percentage of the cells in the tissue. Thus, isolation of stem cells from tissues for further study represents a major challenge. The anti‐tumor drug 5‐fluorouracil (5‐FU) selectively kills proliferating cells, sparing cells in the G0 phase. Thus, the objective of this study was to determine whether 5‐FU can be used to enrich stem cells in a human bronchial epithelial (HBE) cell population in vitro. Side population (SP) cells were isolated from untreated HBE cells or HBE cells treated with 5‐FU, and the resulting cells were subjected to colony formation assays, culturing of cell spheres, and tumorigenicity assays. Expression of Oct3/4, Sox2, PCK, and β‐catenin were examined by Western blot analysis and immunofluorescence. Treatment with 5‐FU increased the percentage of SP cells from 0.3% to 1.5%, and the clonogenic ability of 5‐FU‐treated cells was more than twofold higher than that of HBE cells. Cells that survived after 5‐FU treatment exhibited a higher capacity for sphere formation. Furthermore, spheres formed from 5‐FU‐treated cells possessed the capacity to generate differentiated progenies. Cells treated with 5‐FU also exhibited tumorigenic potential, based on tumor formation assays in nude mice, and Oct3/4‐positive cell aggregates were identified in the resulting tumors. In this study, we have shown that 5‐FU treatment enriched the population of cells expressing the putative embryonic markers Oct3/4 and Sox2 and exhibiting nuclear accumulation of β‐catenin. Furthermore, 5‐FU‐treated cells expressed low levels of the epithelial differentiation marker PCK. Analysis of epigenetic modifications suggested that Oct3/4‐positive cells possessed characteristics of stem cells. These results demonstrate that treatment with 5‐FU can enrich the stem cell population present in a human bronchial epithelial cell line, and implicate combined treatment with 5‐FU and serum‐free medium as a new method for isolation of stem‐like cells from the HBE cell line.     

Selective anticancer effects of a synthetic flavagline on human Oct4-expressing cancer stem-like cells via a p38 MAPK-dependent caspase-3-dependent pathway

Cancer stem cells (CSCs) are considered as the initiators of the carcinogenic process and are therefore emerging targets for innovative anticancer therapies. In order to evaluate the anticancer chemopreventive activity of flavagline derivatives, we used the pluripotent teratocarcinomal cell as a model of Oct4-expressing cancer stem-like cell and determined the underlying cellular and molecular mechanisms induced by a synthetic flavagline. We precisely investigated the effects of the flavagline derivative FL3 on the human embryonal carcinoma (EC) cell line NT2/D1 and compared the responses to those of a normal more restrictive pluripotent stem cell line (i.e. BJ fibroblast cell line). FL3 selectively inhibited the proliferation of NT2/D1 cells by inducing G₁ phase cell cycle arrest in a dose-dependent manner. Moreover, FL3 treatment specifically triggered apoptosis in association with an induction of the phosphorylation of p38 mitogen-activated protein kinase (MAPK) and caspase-3 activation followed by a drastic downregulation of the master regulator of stemness Oct4. Forced inhibition of p38 MAPK activity by the specific pharmacological inhibitor SB203580 or by p38 MAPK gene knockdown using small-interfering RNA (siRNA) counteracted the effects of FL3, demonstrating that its chemopreventive action is related to growth inhibition and a p38-dependent caspase-3-dependent induction of apoptosis in Oct4-expressing CSCs. This study also shows that FL3 selectively kills poorly differentiated and highly aggressive carcinomal cells, but has little effect on normal stem-like cells. Thus FL3 offers great promise for cancer treatment since it is able to target the carcinogenic process without affecting normal cells.     

干细胞转录因子Oct4和CD133蛋白在肝外胆管癌组织中的表达及临床意义

目的:探讨干细胞转录因子Oct4(Oct4)和CD133蛋白在肝外胆管癌(EHCC)中的表达及临床意义。方法:应用免疫组化方法检测50例EHCC、30例癌旁胆管组织(TAC)和20例正常胆管组织(NBDT)中Oct4和CD133蛋白表达水平,并结合临床病理特征进行分析。结果:在EHCC中Oct4和CD133蛋白阳性表达率分别为62.0%(31/50)和68.0%(36/50)。EHCC中Oct4和CD133表达阳性率显著高于TAC和NBDT(P0.05)。Oct4和CD133的表达与EHCC的TNM分期、分化程度和转移相关(P0.05),且两者表达呈正相关(r=0.33,P0.05)。结论:检测Oct4和CD133基因蛋白表达可作为评估EHCC生物学行为和预后的参考指标。