微小RNA与肿瘤干细胞耐药的研究进展

肿瘤干细胞（Cancer stem cells,CSCs）是肿瘤组织中一小部分具有自我更新和致瘤性的细胞,具有特殊的耐药机制,与肿瘤的复发和治疗失败关系密切。微小RNA（microRNAs,miRNAs）是一类长度约为19～25个核苷酸的内源性非编码单链RNA,能够通过调控相关靶基因的表达,参与调控肿瘤干细胞增殖、凋亡、上皮-间质转化等重要的生命过程,引起CSCs对化疗药物产生原发性多药耐药性。本论文就miRNAs在调控CSCs多药耐药性方面的研究进展作一综述。     

Chemical ionization mass spectrometric determination of acrolein in human breast cancer cells

A selected ion flow tube-chemical ionization mass spectrometric method is presented for the first determination of acrolein metabolically produced in biological tissues. Acrolein in aqueous samples (2.5 ml) is preconcentrated by distillation and directly analyzed using gas-phase proton transfer from H3O+. This method provides sensitive detection of acrolein with the method detection limit of 15 nM at the 99% confidence level. Detection is linear up to the highest concentration studied (13.5 microM, R2 = 0.998). Acrolein levels are determined in doxorubicin-sensitive (MCF-7) and doxorubicin-resistant (MCF-7/Adr) human breast cancer cells in vitro. The intracellular acrolein concentrations differ insignificantly: 0.61 microM for sensitive cells and 0.54 microM for resistant cells. Treatment with a physiological concentration of doxorubicin (0.5 microM) for 24 h at 37 degrees C increased acrolein levels by factors of 2.6 and 1.9 for MCF-7 and MCF-7/Adr cells, respectively. The differential enhancement observed is consistent with the lower levels of enzymes that neutralize oxidative stress in sensitive MCF-7 cells and overexpression of an active drug efflux pump P-170 glycoprotein in resistant MCF-7/Adr cells.     

Phosphorylation of EZH2 by CDK1 and CDK2

Histone H3 lysine 27 trimethylation (H3K27me3) catalyzed by the enzymatic subunit EZH2 in the Polycomb repressive complex 2 (PRC2) is essential for cells to ‘memorize’ gene expression patterns through cell divisions and plays an important role in establishing and maintaining cell identity during development. However, how the epigenetic mark is inherited through cell generations remains poorly understood. Recently, we and others demonstrate that CDK1 and CDK2 phosphorylate EZH2 at threonine 350 (T350) and that T350 phosphorylation is important for the binding of EZH2 to PRC2 recruiters, such as noncoding RNAs (ncRNAs) HOTAIR and XIST, and for the effective recruitment of PRC2 to EZH2 target loci in cells. These findings imply that phosphorylation of EZH2 by CDK1 and CDK2 may provide cells a mechanism that enhances EZH2 function during S and G2 phases of the cell cycle, thereby ensuring K27me3 on de novo synthesized H3 incorporated in nascent nucleosomes before sister chromosomes are divided into two daughter cells. Additionally, a potential role of T350 phosphorylation of EZH2 in differing EZH2 from its homolog EZH1 in catalyzing H3K27me3 as well as the interplay between phosphorylation at T350 and other residues (e.g. phosphorylation by p38 at threonine 372 (T372)) in governing EZH2 activity in proliferating versus non-dividing cells are also discussed. Together, CDK phosphorylation of EZH2 at T350 may represent a key regulatory mechanism of EZH2 function that is essential for the maintenance of H3K27me3 marks through cell divisions.     

Doxorubicin and 5-fluorouracil resistant hepatic cancer cells demonstrate stem-like properties

The efficacy of hepatocellular carcinoma (HCC) treatment is very low because of the high percentage of recurrence and resistance to anticancer agents. Hepatic cancer stem cells (HCSCs) are considered the origin of such recurrence and resistance. Our aim was to evaluate the stemness of doxorubicin and 5-fluorouracil resistant hepatic cancer cells and establish the new method to isolate the HCSCs from primary cultured HCC tumors. HCC biopsies were used to establish primary cultures. Then, primary cells were selected for HCSCs by culture in medium supplemented with doxorubicin (0, 0.1, 0.25, 0.5 or 1 μg/mL), 5-fluorouracil (0, 0.1, 0.25, 0.5 or 1 μg/mL) or their combination. Selection was confirmed by detection of HCSC markers such as CD133, CD13, CD90, and the side population was identified by rhodamine 123 efflux. The cell population with the strongest expression of these markers was used to evaluate the cell cycle, gene expression profile, tumor sphere formation, marker protein expression, and in vivo tumorigenesis. Selective culture of primary cells in medium supplemented with 0.5 μg/mL doxorubicin and 1 μg/mL 5-fluorouracil selected cancer cells with the highest stemness properties. Selected cells strongly expressed CD13, CD133, CD90, and CD326, efflux rhodamine 123 and formed tumor spheres in suspension. Moreover, selected cells were induced to differentiate into cells with high expression of CD19 and AFP (alpha-fetoprotein), and importantly, could form tumors in NOD/SCID mice upon injection of 1 × 10⁵ cells/mouse. Selective culture with doxorubicin and 5-fluorouracil will enrich HCSCs, is an easy method to obtain HCSCs that can be used to develop better therapeutic strategies for patients with HCC, and particularly HCSC-targeting therapy.     

肿瘤干细胞及其耐药机制

肿瘤干细胞是存在于造血系统肿瘤和一些实体瘤中具有干细胞特性的细胞。肿瘤干细胞假说认为,经药物治疗后肿瘤复发和转移与肿瘤干细胞残存有密切关系。其原因可能是肿瘤干细胞高表达ABC转运蛋白和Bcl-2抗凋亡蛋白,同时其本身又具有一些干细胞特性。对肿瘤干细胞耐药机制的研究,将有助于发现新的肿瘤治疗靶点和更好的抗癌策略。     

Understanding telomerase in cancer stem cell biology

Comment on: Vicente-Dueñas C, et al. Oncotarget 2012; Epub ahead of print; PMID:22408137.     

胃癌干细胞研究进展

胃癌是仅次于肺癌的第二大致死率癌症,尽管近年来对胃癌研究有了很大进展,但由于缺乏良好的动物模型,对胃癌的发病机理仍然不是很清楚.近年的研究表明,肿瘤组织不是由均一细胞构成的,其中存在一些少量细胞可以自我更新并可以分化为肿瘤组织的其他细胞,这类细胞具有类似成体组织干细胞（tissue stem cells）的特性称之为肿瘤干细胞（cancer stem cells）.肿瘤干细胞被认为在肿瘤的生长、转移、复发中发挥着重要作用.有证据表明在胃癌组织中存在胃癌干细胞（gastric cancer stem cells）,但是对胃癌干细胞的来源仍然不是十分明确.对肿瘤干细胞的研究有助于癌症的治疗,改变目前药物针对所有癌细胞的治疗策略.     

癌干细胞研究进展

关于肿瘤发生及发展的机制人们已探索多年,但由于肿瘤病因本身的复杂性、研究技术和知识积累不足等各种原因,研究进展缓慢。近些年来,癌干细胞的发现、确认和特性研究为肿瘤发病机制的揭示,乃至新型高效治疗策略的制定提出了新线索。许多研究成果显示,癌干细胞因具有自我更新和潜在的强增殖能力,在肿瘤发生发展、复发转移中均发挥着很重要的作用;肿瘤化疗的失败与肿瘤组织中癌干细胞的耐药性可能存在密切关系。本文就癌干细胞在这方面的研究进展及存在的问题作一综述。