MicroRNAs (miRNAs) are small noncoding RNA molecules that regulate protein expression by targeting the mRNA of proteincoding genes for either cleavage or repression of translation. The roles of miRNAs in lineage determination and proliferation as well as the location of several miRNA genes at sites of translocation breakpoints or deletions has led to the speculation that miRNAs could be important factors in the development or maintenance of the neoplastic state. Here we show that the highly malignant human brain tumor, glioblastoma, strongly overexpresses a specific miRNA, miR-21. Our studies show markedly elevated miR-21 levels in human glioblastoma tumor tissues, early-passage glioblastoma cultures, and in six established glioblastoma cell lines (A172, U87, U373, LN229, LN428, and LN308) compared with nonneoplastic fetal and adult brain tissues and compared with cultured nonneoplastic glial cells. Knockdown of miR-21 in cultured glioblastoma cells triggers activation of caspases and leads to increased apoptotic cell death. Our data suggest that aberrantly expressed miR-21 may contribute to the malignant phenotype by blocking expression of critical apoptosis-related genes. (Cancer Res 2005; 65(14): 6029-33)

The ageing of the human brain is a cause of cognitive decline in the elderly and the major risk factor for Alzheimer's disease. The time in life when brain ageing begins is undefined. Here we show that transcriptional profiling of the human frontal cortex from individuals ranging from 26 to 106 years of age defines a set of genes with reduced expression after age 40. These genes play central roles in synaptic plasticity, vesicular transport and mitochondrial function. This is followed by induction of stress response, antioxidant and DNA repair genes. DNA damage is markedly increased in the promoters of genes with reduced expression in the aged cortex. Moreover, these gene promoters are selectively damaged by oxidative stress in cultured human neurons, and show reduced base-excision DNA repair. Thus, DNA damage may reduce the expression of selectively vulnerable genes involved in learning, memory and neuronal survival, initiating a programme of brain ageing that starts early in adult life.

Hepatocellular carcinoma (HCC) is a highly heterogeneous disease, and prior attempts to develop genomics-based classification for HCC have yielded highly divergent results, indicating difficulty to identify unified molecular anatomy. We performed a meta-analysis of gene expression profiles in datasets from 8 independent patient cohorts across the world. In addition, aiming to establish the real world applicability of a classification system, we profiled 118 formalin-fixed, paraffin-embedded tissues from an additional patient cohort. A total of 603 patients were analyzed, representing the major etiologies of HCC (hepatitis B and C) collected from Western and Eastern countries. We observed 3 robust HCC subclasses (termed S1, S2, and S3), each correlated with clinical parameters such as tumor size, extent of cellular differentiation, and serum alpha-fetoprotein levels. An analysis of the components of the signatures indicated that S1 reflected aberrant activation of the WNT signaling pathway, S2 was characterized by proliferation as well as MYC and AKT activation, and S3 was associated with hepatocyte differentiation. Functional studies indicated that the WNT pathway activation signature characteristic of S1 tumors was not simply the result of beta-catenin mutation, but rather was the result of TGF-beta activation, thus representing a new mechanism of WNT pathway activation in HCC. These experiments establish the first consensus classification framework for HCC based on gene-expression profiles, and highlight the power of integrating of multiple datasets to define a robust molecular taxonomy of the disease.

Background-It is a challenge to identify patients who, after undergoing potentially curative treatment for hepatocellular carcinoma, are at greatest risk for recurrence. Such high-risk patients could receive novel interventional measures. An obstacle to the development of genome-based predictors of outcome in patients with hepatocellular carcinoma has been the lack of a means to carry out genomewide expression profiling of fixed, as opposed to frozen, tissue.

Aberrant activation of the canonical Wnt/β-catenin pathway occurs in almost all colorectal cancers and contributes to their growth, invasion and survival. Although dysregulated β-catenin activity drives colon tumorigenesis, additional genetic perturbations are required to elaborate fully malignant disease. To identify genes that both modulate β-catenin activity and are essential for colon cancer cell proliferation, we conducted two loss-of-function screens in human colon cancer cells and compared genes identified in these screens with an analysis of copy-number alterations in colon cancer specimens. One of these genes, CDK8, which encodes a member of the mediator complex, is located at 13q12.13, a region of recurrent copy number gain in a substantial fraction of colon cancers. Suppression of CDK8 expression inhibited proliferation in colon cancer cells characterized by high levels of CDK8 and β-catenin hyperactivity. CDK8 kinase activity was necessary for β-catenin driven transformation and expression of several β-catenin transcriptional targets. Together these observations suggest that therapeutic interventions targeting CDK8 may confer clinical benefit in β-catenin-driven malignancies.Correspondence and Requests for materials should be addressed to W.C.H. (Email: william_hahn@dfci.harvard.edu).. The Wnt/β-catenin pathway is implicated in over 90% of colon cancers and in a fraction of other human malignancies. Loss of the tumor suppressor APC or activating CTNNB1 (β-catenin) mutations results in constitutive activity of the β-catenin-T cell factor (TCF) transcriptional complex, which drives adenoma formation 1,2 . Although mutations in TP53 or K-RAS cooperate with dysregulated β-catenin signaling to program a fully malignant phenotype 3 , these mutations are found in less than half of β-catenin-driven colon cancers 4 . NIH Public AccessTo identify oncogenes that modulate β-catenin-dependent transcription and regulate colon cancer cell proliferation, we conducted two RNAi-based loss-of-function screens. We engineered DLD1 colon cancer cells, which harbor APC deletions and depend on β-catenin for proliferation 5 , to stably express "TOPFLASH" β-catenin-luciferase and "FOPFLASH" mutant-Renilla reporter constructs 6,7 (DLD1 Rep ). Suppression of β-catenin expression in DLD1 Rep cells by three β-catenin-specific short hairpin RNAs (shRNA) markedly reduced the TOPFLASH/FOPFLASH ratio (Fig. 1a), confirming that reporter activity requires β-catenin expression. We then screened DLD1 Rep cells with a shRNA library containing 4849 shRNAs that target 1000 genes, including 95% of the human kinome 6 . We found 34 genes whose expression was necessary for β-catenin activity, including two known β-catenin regulators, CSNK1G3 8 and CSNK1E 9 ( Fig. 1b and Supplementary Table 1).In parallel, we performed an arrayed, kinase-enriched shRNA screen in another β-catenindependent colon cancer cell line, HCT116, to identify genes essential for cancer cell proliferation. We identified 166 candidate genes necessary for proliferatio...

Recreational physical activity after the diagnosis of stages I to III colorectal cancer may reduce the risk of colorectal cancer-specific and overall mortality.

The vast majority of brain tumors in adults exhibit glial characteristics. Brain tumors in children are diverse: Many have neuronal characteristics, whereas others have glial features. Here we show that activation of the Gi protein-coupled receptor CXCR4 is critical for the growth of both malignant neuronal and glial tumors. Systemic administration of CXCR4 antagonist AMD 3100 inhibits growth of intracranial glioblastoma and medulloblastoma xenografts by increasing apoptosis and decreasing the proliferation of tumor cells. This reflects the ability of AMD 3100 to reduce the activation of extracellular signal-regulated kinases 1 and 2 and Akt, all of which are pathways downstream of CXCR4 that promote survival, proliferation, and migration. These studies (i) demonstrate that CXCR4 is critical to the progression of diverse brain malignances and (ii) provide a scientific rationale for clinical evaluation of AMD 3100 in treating both adults and children with malignant brain tumors.

Neuroendocrine tumors (NETs) are a heterogeneous group of tumors originating in various anatomic locations. The management of this disease poses a significant challenge because of the heterogeneous clinical presentations and varying degree of aggressiveness. The recent completion of several phase III trials, including those evaluating octreotide, sunitinib, and everolimus, demonstrate that rigorous evaluation of novel agents in this disease is possible and can lead to practice-changing outcomes. Nevertheless, there are many aspects to the treatment of NETs that remain unclear and controversial. The North American Neuroendocrine Tumor Society (NANETS) published a set of consensus guidelines in 2010 which provided an overview for the treatment of patients with these malignancies. Here, we present a set of consensus tables intended to complement these guidelines and serve as a quick, accessible reference for the practicing physician.