肿瘤干细胞及肝癌肿瘤干细胞

肿瘤干细胞理论认为只有存在于肿瘤中的少量干细胞性质的细胞群体对肿瘤发生和发展起着决定作用,肿瘤是由干细胞突变积累而形成的无限增殖的异常组织,这一理论的提出使人们对肿瘤发生机制的认识上升到了一个新的高度,也引起了研究者的广泛关注;肝癌是我国常见的恶性肿瘤之一,我国肝癌死亡率居世界之首,目前对肝癌的研究是我国恶性肿瘤防治的重点工作,现对当前肿瘤干细胞与肝癌肿瘤干细胞相关方面的最新研究进展作一概述。     

间充质干细胞通过分解代谢糖酵解促进肺癌细胞生长（英文）

存在于骨髓中的间充质干细胞(bone marrow mesenchymal stem cells,BMSCs,也称为间充质基质细胞)可以被募集到肿瘤部位并构成肿瘤微环境。细胞代谢在癌症进展中起重要作用。在癌症微环境中间充质细胞和肿瘤细胞发生代谢方式的转变。然而,尚不清楚肿瘤细胞和BMSCs细胞的相互作用如何影响细胞代谢和肿瘤进展。在本研究中,通过将BMSCs和小鼠肺癌细胞LLC细胞共同注射到C57BL/6小鼠,构建了皮下瘤模型;随后在原位瘤分离BMSCs和LLC细胞,进行RNA测序,以获得肿瘤微环境下BMSCs和LLC细胞的转录组。结果显示BMSCs中上调的基因富集于代谢途径。进一步根据差异表达的分子构建相互作用网路,发现BMSCs网络中的核心预测途径是代谢途径、MAPK信号通路和HIF-1信号通路。然而,在肿瘤微环境中LLC细胞的代谢途径受到抑制。体内动物实验证实抑制糖酵解可以减少荷瘤小鼠肿瘤的生长。以上结果提示,BMSCs增加了糖酵解,通过反式Warburg效应促进癌细胞的生长,在肿瘤微环境下BMSCs的代谢重编程影响肿瘤细胞的转归。     

GFP Stable Transfection Facilitated the Characterization of Lung Cancer Stem Cells

Cancer stem cells (CSCs) are a subset of cancer cells that play key roles in metastasis and cancer relapse. The elimination of CSCs is very important during cancer therapy. To develop drugs that target CSCs, the isolation and identification of putative CSCs are required. Some of the characteristics of CSCs are assessed by cell survival assays. In such experiments, the density of the cells seeded on the plates may affect the experimental results, leading to potentially inaccurate conclusions. In this study, a new assay to facilitate the characterization of CSCs has been developed by stable transfection of GFP, using the A549 lung cancer cell line as a model. A putative CSC line, A549 sphere cells, was obtained by culturing A549 cells in ultra-low dishes in serum-free medium. To ensure that the putative CSCs were grown under the same conditions as the A549–GFP cells and were not affected by the number of cells seeded, A549 sphere cells were mixed with GFP stably transfected A549 (A549–GFP) cells. The mixture was subjected to flow cytometry assay and inverted fluorescence microscopy to detect changes in the proportion of GFP-positive cells after treatment. A549 sphere cells had a slower proliferation rate and an improved chemoresistance. They also showed differentiation ability. This work suggests that mixing GFP stably transfected cancer cells with putative CSCs may facilitate the identification of CSCs, making it convenient for studies of targeted CSCs.     

癌、干细胞和癌干细胞共同拥有的信号传导通路

干细胞（SC）是具有无限自我更新和分化能力的细胞,随着对SC研究的不断深入,人们发现SC与肿瘤细胞有许多共性,如无限增生能力、迁移能力及在某些条件下能相互转化,故提出了肿瘤起源于SC的学说。探讨癌、SC和癌干细胞（CSC）之间可能存在的共同信号传导通路,以便发现治疗CSC的靶位。     

肺脏干细胞研究进展

肺脏干细胞是一类重要的成体干细胞,对于维持肺脏稳态、肺损伤后的修复发挥关键的作用。作者总结了现有采用流式细胞分选和小鼠的谱系追踪模型,在成年肺的不同解剖位置鉴定不同的肺干/祖细胞亚群的最新进展,对于更进一步了解肺损伤后的修复、肺疾病的发病机制以及鉴定肿瘤的来源细胞至关重要的意义。本文指出:从肺的发育角度研究肺的再生和激活肺损伤后修复的相关信号通路将为加深对肺干/祖细胞的认识,促进再生医学发展具有十分重要的意义。     

Identification and Characterization of Cells with Cancer Stem Cell Properties in Human Primary Lung Cancer Cell Lines

Lung cancer (LC) with its different subtypes is generally known as a therapy resistant cancer with the highest morbidity rate worldwide. Therapy resistance of a tumor is thought to be related to cancer stem cells (CSCs) within the tumors. There have been indications that the lung cancer is propagated and maintained by a small population of CSCs. To study this question we established a panel of 15 primary lung cancer cell lines (PLCCLs) from 20 fresh primary tumors using a robust serum-free culture system. We subsequently focused on identification of lung CSCs by studying these cell lines derived from 4 representative lung cancer subtypes such as small cell lung cancer (SCLC), large cell carcinoma (LCC), squamous cell carcinoma (SCC) and adenocarcinoma (AC). We identified a small population of cells strongly positive for CD44 (CD44^high) and a main population which was either weakly positive or negative for CD44 (CD44^low/−). Co-expression of CD90 further narrowed down the putative stem cell population in PLCCLs from SCLC and LCC as spheroid-forming cells were mainly found within the CD44^highCD90⁺ sub-population. Moreover, these CD44^highCD90⁺ cells revealed mesenchymal morphology, increased expression of mesenchymal markers N-Cadherin and Vimentin, increased mRNA levels of the embryonic stem cell related genes Nanog and Oct4 and increased resistance to irradiation compared to other sub-populations studied, suggesting the CD44^highCD90⁺ population a good candidate for the lung CSCs. Both CD44^highCD90⁺ and CD44^highCD90⁻ cells in the PLCCL derived from SCC formed spheroids, whereas the CD44^low/− cells were lacking this potential. These results indicate that CD44^highCD90⁺ sub-population may represent CSCs in SCLC and LCC, whereas in SCC lung cancer subtype, CSC potentials were found within the CD44^high sub-population.     

肿瘤干细胞研究进展及临床应用前景

肿瘤干细胞是肿瘤中具有自我更新能力和分化潜能,能产生异质性细胞的细胞。我们简要阐述了肿瘤干细胞存在的证据、分离技术及来源,并对以肿瘤干细胞为靶标的肿瘤治疗途径、临床应用前景和问题进行了综述。     

microRNAs参与肿瘤干细胞的调节

肿瘤干细胞存在于多种类型肿瘤中,并与肿瘤的发生发展密切相关。肿瘤干细胞和胚胎干细胞在生物学特征上存在许多共同点,如自我更新,多潜能性分化等等。然而,肿瘤干细胞和胚胎干细胞又存在很大差异,主要表现在耐药性、致瘤力和转移活性上。肿瘤干细胞在临床研究中具有不可替代的重要性,然而其分子水平上的调节机制尚未被完整揭示。作为内源性非编码小RNA的一部分,miRNAs在细胞发生发展的调节过程中扮演着重要角色。大量研究表明,miRNAs参与肿瘤干细胞的调节,并参与肿瘤的发生与进展。探索miRNAs在肿瘤干细胞基因表达调控中的作用及作用机制,有助于肿瘤特异性生物学标志物及治疗靶点的确定。本文就miRNAs与肿瘤干细胞调节的相关研究进展进行综述。     

肿瘤研究的金钥匙:肿瘤干细胞

“肿瘤干细胞学说”认为肿瘤组织不是均一的,其中只有一小部分肿瘤干细胞具有诱发并维持肿瘤恶性表达的能力。这一概念的提出为肿瘤真正意义上的靶向治疗找到了良方妙药,即选择性杀伤肿瘤干细胞从而治愈肿瘤。找到肿瘤干细胞并了解其生物学特性对我们真正理解肿瘤的发生、发展和转归机制,根治肿瘤并防止肿瘤的转移和复发具有积极意义。本文概述对人淋巴细胞白血病、乳腺肿瘤、脑部肿瘤及其他肿瘤的肿瘤干细胞及其相关机制的研究进展。     

Cancer Stem Cells Sensitivity Assay (STELLA) in Patients with Advanced Lung and Colorectal Cancer: A Feasibility Study

Background

Cancer stem cells represent a population of immature tumor cells found in most solid tumors. Their peculiar features make them ideal models for studying drug resistance and sensitivity. In this study, we investigated whether cancer stem cells isolation and in vitro sensitivity assay are feasible in a clinical setting.

Methods

Cancer stem cells were isolated from effusions or fresh cancer tissue of 23 patients who progressed after standard therapy failure. Specific culture conditions selected for immature tumor cells that express markers of stemness. These cells were exposed in vitro to chemotherapeutic and targeted agents.

Results

Cancer stem cells were extracted from liver metastases in 6 cases (25%), lung nodules in 2 (8%), lymph node metastases in 3 (12.5%) and pleural/peritoneal/pericardial effusion in 13 (54%). Cancer stem cells were successfully isolated in 15 patients (63%), including 14 with lung cancer (93.3%). A sensitivity assay was successfully performed in 7 patients (30.4%), with a median of 15 drugs/combinations tested (range 5-28) and a median time required for results of 51 days (range 37-95).

Conclusion

The approach used for the STELLA trial allowed isolation of cancer stem cells in a consistent proportion of patients. The low percentage of cases completing the full procedure and the long median time for obtaining results highlights the need for a more efficient procedure.

Trial Registration

ClinalTrials.gov NCT01483001     

Cancer Stem Cells Persist in Many Cancer Cell Lines

Both stem cells and cancer cells are thought to be capable of unlimited proliferation. Paradoxically, however, some cancers seem to contain stem-like cells (cancer stem cells). To help resolve this paradox, we investigated whether established malignant cell lines, which have been maintained over years in culture, contain a subpopulation of stem cells. We have shown that four cancer cell lines contain a small side population (SP), which, in many normal tissues, is enriched for stem cells of the tissue. We have also shown that SP cells in C6 glioma cell line, but not non-SP cells, can generate both SP and non-SP cells in culture and are largely responsible for the in vivo malignancy of this cell line. We propose that many cancer cell lines contain a minor subpopulation of stem cells that is enriched in a SP, can be maintained indefinitely in culture, and is crucial for their malignancy.     

Evolution and Phenotypic Selection of Cancer Stem Cells

Cells of different organs at different ages have an intrinsic set of kinetics that dictates their behavior. Transformation into cancer cells will inherit these kinetics that determine initial cell and tumor population progression dynamics. Subject to genetic mutation and epigenetic alterations, cancer cell kinetics can change, and favorable alterations that increase cellular fitness will manifest themselves and accelerate tumor progression. We set out to investigate the emerging intratumoral heterogeneity and to determine the evolutionary trajectories of the combination of cell-intrinsic kinetics that yield aggressive tumor growth. We develop a cellular automaton model that tracks the temporal evolution of the malignant subpopulation of so-called cancer stem cells(CSC), as these cells are exclusively able to initiate and sustain tumors. We explore orthogonal cell traits, including cell migration to facilitate invasion, spontaneous cell death due to genetic drift after accumulation of irreversible deleterious mutations, symmetric cancer stem cell division that increases the cancer stem cell pool, and telomere length and erosion as a mitotic counter for inherited non-stem cancer cell proliferation potential. Our study suggests that cell proliferation potential is the strongest modulator of tumor growth. Early increase in proliferation potential yields larger populations of non-stem cancer cells(CC) that compete with CSC and thus inhibit CSC division while a reduction in proliferation potential loosens such inhibition and facilitates frequent CSC division. The sub-population of cancer stem cells in itself becomes highly heterogeneous dictating population level dynamics that vary from long-term dormancy to aggressive progression. Our study suggests that the clonal diversity that is captured in single tumor biopsy samples represents only a small proportion of the total number of phenotypes.     

Clinical Implications and Future Perspectives of Circulating Tumor Cells and Biomarkers in Clinical Outcomes of Colorectal Cancer

Colorectal cancer (CRC) is a major public health problem. Early CRC detection, pretherapeutic responsiveness prediction, and postoperative micrometastasis monitoring are the hallmarks for successful CRC treatment. Here, the methodologies used for detecting circulating tumor cells (CTCs) from CRC are reviewed. In addition to the traditional CRC biomarkers, the persistent presence of posttherapeutic CTCs indicates resistance to adjuvant chemotherapy and/or radiotherapy; hence, CTCs also play a decisive role in the subsequent relapse of CRC. Moreover, the genetic and phenotypic profiling of CTCs often differs from that of the primary tumor; this difference can be used to select the most effective targeted therapy. Consequently, studying CTCs can potentially individualize treatment strategies for patients with CRC. Therefore, CTC detection and characterization may be valuable tools for refining prognosis, and CTCs can be used in a real-time tumor biopsy for designing individually tailored therapy against CRC.     

Genomic Instability in Pluripotent Stem Cells: Implications for Clinical Applications

Human pluripotent stem cells (hPSCs) are known to acquire genomic changes as they proliferate and differentiate. Despite concerns that these changes will compromise the safety of hPSC-derived cell therapy, there is currently scant evidence linking the known hPSC genomic abnormalities with malignancy. For the successful use of hPSCs for clinical applications, we will need to learn to distinguish between innocuous genomic aberrations and those that may cause tumors. To minimize any effects of acquired mutations on cell therapy, we strongly recommend that cells destined for transplant be monitored throughout their preparation using a high-resolution method such as SNP genotyping.