Lin28B介导肝癌细胞中HBx相关Let-7沉默

目的:Let-7在多种肿瘤包括肝癌中低表达,扮演抑癌基因角色.我们的前期研究提示HBx(人乙肝病毒X蛋白)在肝癌细胞中显著下调Let-7表达,但内在机制有待进一步揭示.Lin28B能负调控Let-7的转录后加工成熟,这促使我们验证其是否介导了肝癌细胞中HBx相关的Let-7低表达.方法:qRT-PCR检测c-Myc和Lin28B特异siRNA转染HepG2-HBx细胞(HBx稳定转染的HepG2细胞)前后Let-7的表达变化,同时在肝癌细胞和或组织中验证HBx和Lin28B的表达相关性.最后,利用细胞周期及增殖实验检测Lin28B对HepG2细胞的生物学影响.结果:Lin28B高表达于HBx稳定/瞬时转染的HepG2肝癌细胞及HBV阳性的肝癌和肝硬化组织.Lin28B介导了HBx在HepG2肝癌细胞中对Let-7的抑制.Lin28B特异siRNAs可阻滞细胞周期进展进而抑制HepG2细胞生长.结论:HBx 在肝癌细胞中通过诱导Lin28B表达而抑制Let-7.Lin28B可能成为治疗HBV相关肝癌的新靶点.     

MicroRNA let-7 downregulates STAT3 phosphorylation in pancreatic cancer cells by increasing SOCS3 expression

Although dispensable for normal pancreatic function, STAT3 signaling is frequently activated in pancreatic cancers. Consistent downregulation of expression of microRNA let-7 is also characteristic of pancreatic ductal adenocarcinoma (PDAC) biopsy specimens. We demonstrate in this study that re-expression of let-7 in poorly-differentiated PDAC cell lines reduced phosphorylation/activation of STAT3 and its downstream signaling events and reduced the growth and migration of PDAC cells. Let-7 re-expression did not repress expression of STAT3 protein or its activator cytokine interleukin 6 (IL-6). However, let-7 re-expression enhanced cytoplasmic expression of suppressor of cytokine signaling 3 (SOCS3), which blocks STAT3 activation by JAK2. Our study thus identified a mechanism by which STAT3 signaling can be inhibited in pancreatic cancer cells by modifying let-7 expression.     

Lin28b Promotes Head and Neck Cancer Progression via Modulation of the Insulin-Like Growth Factor Survival Pathway

Lin28 is a developmentally regulated RNA binding protein which has recently emerged as key regulator in the biogenesis of the let-7 micro-RNA family. While the expression of Lin28b has been linked to advanced tumor stage, the precise molecular mechanism(s) by which Lin28b drives disease progression is still being unraveled. Herein, we generated a let-7-resistant Lin28b ORF, stably expressed in the FaDu head and neck cancer (HNC) cell line. FaDu-Lin28b cells exhibited enhanced tumor growth in vitro and in vivo. Global gene and micro-RNA expression analyses revealed significant enrichment in several pathways involved in cell migration, chromatin remodeling, and cellular stress response. Direct regulation of selected genes (HMGA2, CCND2, IGF1R, and IGF2BP2) via a let-7-Lin28b mechanism was validated. Notably, up-regulation of several genes in the IGF pathway in Lin28b-expressing cells was observed. Functional studies revealed significant increase in the survival of Lin28b-expressing cells when cultured under stress conditions, which was dependent on the presence of IGF1. Therefore, our data identified several novel gene targets for Lin28b-let7, and revealed a novel mechanism by which Lin28b promote tumorigenesis. Concordantly, clinical examinations of Lin28b, IGF2BP2 and IGF2 revealed a significant association between the expression of these genes with disease relapse, thereby corroborating the potential relevance for the Lin28b/IGF axis in HNC progression.     

Cancer stem cells,the epithelial to mesenchymal transition (EMT) and radioresistance: Potential role of hypoxia

Numerous studies have demonstrated the presence of cancer stem cells (CSCs) within solid tumors. Although the precursor of these cells is not clearly established, recent studies suggest that the phenotype of CSCs may be quite plastic and associated with the epithelial-to-mesenchymal transition (EMT). In patients, the presence of EMT and CSCs has been implicated in increased resistance to radiotherapy. Hypoxia, a negative prognostic factor for treatment success, is a potent driver of a multitude of molecular signalling pathways that allow cells to survive and thrive in the hostile tumor microenvironment and can induce EMT. Hypoxia also provides tumor cells with cues for maintenance of a stem-like state and may help to drive the linkage between EMT and CSCs. Understanding the biology of CSCs, the EMT phenotype and their implications in therapeutic relapse may provide crucial new approaches in the development of improved therapeutic strategies.     

MicroRNA let‐7b regulates genomic balance by targeting Aurora B kinase

The let‐7 microRNA (miRNA) family has been implicated in the regulation of diverse cellular processes and disease pathogenesis. In cancer, loss‐of‐function of let‐7 miRNAs has been linked to tumorigenesis via increased expression of target oncogenes. Excessive proliferation rate of tumor cells is often associated with deregulation of mitotic proteins. Here, we show that let‐7b contributes to the maintenance of genomic balance via targeting Aurora B kinase, a key regulator of the spindle assembly checkpoint (SAC). Our results indicate that let‐7b binds to Aurora B kinase 3′UTR reducing mRNA and protein expression of the kinase. In cells, excess let‐7b induced mitotic defects characteristic to Aurora B perturbation including increased rate of polyploidy and multipolarity, and premature SAC inactivation that leads to forced exit from chemically induced mitotic arrest. Moreover, the frequency of aneuploid HCT‐116 cells was significantly increased upon let‐7b overexpression compared to controls. Interestingly, together with a chemical Aurora B inhibitor, let‐7b had an additive effect on polyploidy induction in HeLa cells. In breast cancer patients, reduced let‐7b expression was found to be associated with increased Aurora B expression in grade 3 tumors. Furthermore, let‐7b was found downregulated in the most aggressive forms of breast cancer determined by clinicopathological parameters. Together, our findings suggest that let‐7b contributes to the fidelity of cell division via regulation of Aurora B. Moreover, the loss of let‐7b in aggressive tumors may drive tumorigenesis by up‐regulation of Aurora B and other targets of the miRNA, which further supports the role of let‐7b in tumor suppression.     

Targeting ornithine decarboxylase reverses the LIN28/Let-7 axis and inhibits glycolytic metabolism in neuroblastoma

LIN28 has emerged as an oncogenic driver in a number of cancers, including neuroblastoma (NB). Overexpression of LIN28 correlates with poor outcome in NB, therefore drugs that impact the LIN28/Let-7 pathway could be beneficial in treating NB patients. The LIN28/Let-7 pathway affects many cellular processes including the regulation of cancer stem cells and glycolytic metabolism. Polyamines, regulated by ornithine decarboxylase (ODC) modulate eIF-5A which is a direct regulator of the LIN28/Let-7 axis. We propose that therapy inhibiting ODC will restore balance to the LIN28/Let-7 axis, suppress glycolytic metabolism, and decrease MYCN protein expression in NB. Difluoromethylornithine (DFMO) is an inhibitor of ODC in clinical trials for children with NB. In vitro experiments using NB cell lines, BE(2)-C, SMS-KCNR, and CHLA90 show that DFMO treatment reduced LIN28B and MYCN protein levels and increased Let-7 miRNA and decreased neurosphere formation. Glycolytic metabolic activity decreased with DFMO treatment in vivo. Additionally, sensitivity to DFMO treatment correlated with LIN28B overexpression (BE(2)-C>SMS-KCNR>CHLA90). This is the first study to demonstrate that DFMO treatment restores balance to the LIN28/Let-7 axis and inhibits glycolytic metabolism and neurosphere formation in NB and that PET scans may be a meaningful imaging tool to evaluate the therapeutic effects of DFMO treatment.     

let-7在肿瘤中的研究进展

let-7是目前研究最为广泛的miRNA之一.在肿瘤中,let-7具有抑制细胞增殖、促进细胞分化和凋亡的多种生物学功能.同时在不同的人肿瘤组织和细胞中,let-7表达的下调伴随其靶基因的表达变化,表明let-7与肿瘤呈高度相关性.     

LIN28B suppresses microRNA let-7b expression to promote CD44+/LIN28B+ human pancreatic cancer stem cell proliferation and invasion

Although the highly proliferative, migratory, and multi-drug resistant phenotype of human pancreatic cancer stem cells (PCSCs) is well characterized, knowledge of their biological mechanisms is limited. We used CD44 and LIN28B as markers to screen, isolate, and enrich CSCs from human primary pancreatic cancer. Using flow cytometry, we identified a human primary pancreatic cancer cell (PCC) subpopulation expressing high levels of both CD44 and LIN28B. CD44+/LIN28B+ PCSCs expressed high levels of stemness marker genes and possessed higher migratory and invasive ability than CD44-/LIN28B- PCCs. CD44+/LIN28B+ PCSCs were more resistant to growth inhibition induced by the chemotherapeutic drugs cisplatin and gemcitabine hydrochloride, and readily established tumors in vivo in a relatively short time. Moreover, microarray analysis revealed significant differences between the cDNA expression patterns of CD44+/LIN28B+ PCSCs and CD44-/LIN28B- PCCs. Following siRNA interference of endogenous LIN28B gene expression in CD44+/LIN28B+ PCSCs, not only was their proliferation decreased, there was also cell cycle arrest due to suppression of cyclin D1 expression following the stimulation of miRNA let-7b expression. In conclusion, CD44+/LIN28B+ cells, which possess CSC characteristics, can be reliably sorted from human primary PCCs and represent a valuable model for studying cancer cell physiology and multi-drug resistance.     

联合检测LIN28B和HMGA2在子宫内膜病变中的表达及临床意义

目的:研究LIN28B和HMGA2在子宫内膜病变组织中的表达以探索子宫内膜癌的发病机制,并探讨联合检测两者在子宫内膜癌的诊断及评估中的临床价值。方法:用免疫组化法（SABC）检测正常子宫内膜36例做为对照组,非典型增生组21例,子宫内膜癌136例,共157例做为实验组,观察LIN28B和HMGA2在正常子宫内膜及不同子宫内膜病变组织中的阳性表达情况。结果:LIN28B和HMGA2在子宫内膜癌组织中的表达阳性率均较正常子宫内膜组织及非典型增生子宫内膜高(P<0.05),非典型增生子宫内膜组织中LIN28B和HMGA2的表达阳性率较正常子宫内膜组织高（P<0.05）。LIN28B的表达阳性率与手术病理分期有关,而与肌层浸润、分化程度、淋巴转移及患者绝经与否无关（P>0.05）。HMGA2的表达阳性率与手术病理分期有关（P<0.05）,可能与肌层浸润有关（P=0.0496）,而与分化程度、淋巴转移及患者绝经与否无关（P>0.05）。136例子宫内膜癌组织中LIN28B和HMGA2表达呈正相关（r=0.327,P<0.05）。结论:LIN28B和HMGA2与子宫内膜组织的异常增生及癌变密切相关。LIN28B可能通过某种途径上调HMGA2的表达,从而诱导子宫内膜癌的发生与发展。两者可能成为对于子宫内膜癌诊断及评估有一定参考价值的检测指标。     

Disrupting LIN28 in atypical teratoid rhabdoid tumors reveals the importance of the mitogen activated protein kinase pathway as a therapeutic target

Atypical teratoid rhabdoid tumor (AT/RT) is among the most fatal of all pediatric brain tumors. Aside from loss of function mutations in the SMARCB1 (BAF47/INI1/SNF5) chromatin remodeling gene, little is known of other molecular drivers of AT/RT. LIN28A and LIN28B are stem cell factors that regulate thousands of RNAs and are expressed in aggressive cancers. We identified high-levels of LIN28A and LIN28B in AT/RT primary tumors and cell lines, with corresponding low levels of the LIN28-regulated microRNAs of the let-7 family. Knockdown of LIN28A by lentiviral shRNA in the AT/RT cell lines CHLA-06-ATRT and BT37 inhibited growth, cell proliferation and colony formation and induced apoptosis. Suppression of LIN28A in orthotopic xenograft models led to a more than doubling of median survival compared to empty vector controls (48 vs 115 days). LIN28A knockdown led to increased expression of let-7b and let-7g microRNAs and a down-regulation of KRAS mRNA. AT/RT primary tumors expressed increased mitogen activated protein (MAP) kinase pathway activity, and the MEK inhibitor selumetinib (AZD6244) decreased AT/RT growth and increased apoptosis. These data implicate LIN28/RAS/MAP kinase as key drivers of AT/RT tumorigenesis and indicate that targeting this pathway may be a therapeutic option in this aggressive pediatric malignancy.     

High expression of Lin28 is associated with tumour aggressiveness and poor prognosis of patients in oesophagus cancer

Background:

Lin28 is a negative regulator of the tumour suppressor microRNA, let-7, suggesting its role in tumourigenesis. However, the clinical significance of Lin28 expression in oesophageal cancer has not been elucidated.

Methods:

Lin28 and Lin28B expression was examined by immunohistochemistry in 161 tissues from patients with oesophageal cancer who had undergone curative surgery. The relationship between the expressions of Lin28 and Lin28B and various clinicopathological factors was examined. In vitro assays were conducted to determine the role of Lin28 in aggressiveness of oesophageal cancers using oesophageal cancer cell line.

Results:

Lin28 and Lin28B were overexpressed in oesophageal cancer cells compared with non-cancerous epithelial cells, especially in the invasive front. High expression of Lin28 and Lin28B correlated significantly with lymph node metastasis and poor prognosis. High expression of Lin28B expression correlated significantly with low expression of let-7. Multivariate analysis also identified Lin28B expression as an independent prognostic factor. In vitro assays showed that the proliferative and invasive activities were significantly reduced in Lin28B-knockdown cells, compared with control cells.

Conclusion:

High expression of Lin28 is associated with poor prognosis and high tumour aggressiveness in oesophageal cancer and these effects are mediated through increased proliferation and invasiveness of oesophageal cancer cells.     

Breast cancer stem cells: Multiple capacities in tumor metastasis

Breast cancer is the leading cause of cancer death among women worldwide. Accumulating evidence indicates that the local recurrent and/or distant metastatic tumors, the major causes of lethality in the clinic, are related to the aggressive phenotype of a small fraction of cancer cells loosely termed as cancer stem cells (CSCs), tumor initiating cells (TICs), or cancer metastasis-initiating cells (CMICs). Breast cancer stem cells (BCSCs) are shown to exhibit unique growth abilities including self-renewal, differentiation potential, and resistance to most anti-cancer agents including chemo- and/or radiotherapy, all of which are believed to contribute to the development and overall aggressiveness of the recurrent or metastatic lesions. It is in the urgent need not only to further define the nature of heterogeneity in each tumor but also to characterize the precise mechanisms governing tumor–host cross-talk which is assumed to be initiated by BCSCs. In this review, we will focus on recently identified key factors, including the BCSCs among circulating tumor cells, interaction of BCSCs with the host, epithelial mesenchymal transition (EMT), tumor microenvironment, the intrinsic resistance due to HER2 expression, potential biomarkers of BCSCs and cancer cell immune signaling. We believe that new evidence coming from both bench and clinical research will help to develop more effective approaches to control or significantly reduce the aggressiveness of metastatic tumors.     

Blocking the formation of radiation–induced breast cancer stem cells

The goal of adjuvant (post-surgery) radiation therapy (RT) for breast cancer (BC) is to eliminate residual cancer cells, leading to better local tumor control and thus improving patient survival. However, radioresistance increases the risk of tumor recurrence and negatively affects survival. Recent evidence shows that breast cancer stem cells (BCSCs) are radiation-resistant and that relatively differentiated BC cells can be reprogrammed into induced BCSCs (iBCSCs) via radiation-induced re-expression of the stemness genes. Here we show that in irradiation (IR)-treated mice bearing syngeneic mammary tumors, IR-induced stemness correlated with increased spontaneous lung metastasis (51.7%). However, IR-induced stemness was blocked by targeting the NF-κB- stemness gene pathway with disulfiram (DSF)and Copper (Cu²⁺). DSF is an inhibitor of aldehyde dehydrogenase (ALDH) and an FDA-approved drug for treating alcoholism. DSF binds to Cu²⁺ to form DSF-Cu complexes (DSF/Cu), which act as a potent apoptosis inducer and an effective proteasome inhibitor, which, in turn, inhibits NF-κB activation. Treatment of mice with RT and DSF significantly inhibited mammary primary tumor growth (79.4%) and spontaneous lung metastasis (89.6%) compared to vehicle treated mice. This anti-tumor efficacy was associated with decreased stem cell properties (or stemness) in tumors. We expect that these results will spark clinical investigation of RT and DSF as a novel combinatorial treatment for breast cancer.     

A LIN28B polymorphism predicts for colon cancer survival

The pathogenesis of sporadic colorectal cancer involves distinct pathways, with characteristic genomic alterations. The first pathway, chromosome instability (CIN), is driven by APC mutations and is typified by Kras mutations, p53 mutation/loss of heterozygosity, and deletions at chromosome 18q. The second pathway is referred to as microsatellite instability (MSI), a genetic hallmark of the accumulated mutations that occur as a consequence of derangements in the mismatch repair genes. Finally, proximal colon cancers may involve methylation of a number of genes, which is frequently referred to as the CpG island methylator phenotype (CIMP), and are associated with B-raf mutations. The ability to stratify colorectal cancers by risk would be facilitated by the identification of polymorphisms that might be utilized as biomarkers. LIN28B is an RNA binding protein that is overexpressed in colon cancers. We find that LIN28B rs314277 is associated with significant recurrence of colorectal cancer in Stage II disease, which may have translational therapeutic implications.     

微RNAlet-7d抑制胶质瘤生长和侵袭

背景与目的：let-7d与胶质瘤的关系尚不清楚,本研究探讨let-7d在人脑胶质瘤组织中表达及其对人脑胶质瘤U87细胞生物学特征的影响。方法：原位杂交法检测let-7d在人脑胶质瘤组织和正常脑组织中的表达,利用脂质体将let-7d寡核苷酸转入U87细胞,观察各组细胞生长、凋亡、侵袭情况。结果：人脑胶质瘤组织中let-7d较正常人脑组织低表达,转入let-7d寡核苷酸的U87细胞,生长减缓,凋亡增加,侵袭力减低。结论：微RNAlet-7d在胶质瘤的发生发展中可能起抑制作用。     

microRNAs在肿瘤干细胞中的研究进展

microRNAs（miRNAs）是一类非编码的小RNA,在肿瘤发生发展及侵袭转移中发挥着至关重要的作用。肿瘤干细胞是导致恶性肿瘤复发、转移和耐药的主要根源。研究发现miRNAs可以促进或抑制肿瘤干细胞“干性”的维持,调控肿瘤干细胞的分化及自我更新,从而参与肿瘤的发生发展过程。本文详细介绍了肿瘤干细胞中miRNAs的表达情况及调控机制,阐述其在肿瘤诊断及治疗中的潜在作用。     

let-7与高迁移率族蛋白A在肿瘤中的研究进展

高迁移率族蛋白A(HMGA)在多种肿瘤的发生发展中起着重要的作用,其表达水平会随肿瘤恶性程度的增高或转移潜能的增大而异常增高.let-7是一类内源性非编码的微小RNA,可作为肿瘤抑制因子对HMGA基因进行负性调控.在对多种肿瘤的研究中已经观察到let-7表达水平的下降,并伴随HMGA表达水平的上升,这对肿瘤的早期诊断提...