The biology of Kaposi sarcoma is poorly understood because the dominant cell type in Kaposi sarcoma lesions is not known 1-4. We show by gene expression microarrays that neoplastic cells of Kaposi sarcoma are closely related to lymphatic endothelial cells (LECs) and that Kaposi sarcoma herpesvirus (KSHV) 5,6 infects both LECs and blood vascular endothelial cells (BECs) in vitro. The gene expression microarray profiles of infected LECs and BECs show that KSHV induces transcriptional reprogramming of both cell types. The lymphangiogenic molecules VEGF-D and angiopoietin-2 were elevated in the plasma of individuals with acquired immune deficiency syndrome and Kaposi sarcoma. These data show that the gene expression profile of Kaposi sarcoma resembles that of LECs, that KSHV induces a transcriptional drift in both LECs and BECs and that lymphangiogenic molecules are involved in the pathogenesis of Kaposi sarcoma. The cellular origin of the spindle cells of Kaposi sarcoma lesions is poorly defined 3,7. Kaposi sarcoma spindle cells express endothelial cell markers but also have features of other cell lineages, including fibroblasts, macrophages and smooth muscle cells 1-3. Kaposi sarcoma could be a tumor originating from LECs, as spindle cells ubiquitously express VEGFR-3 and podoplanin and stain with the antibody D2-40 recognizing LECs 4,8. But these markers can also be expressed on angiogenic blood vessels, or on other cell types 9. Furthermore, some BEC markers (e.g., CD34) are expressed in all Kaposi sarcoma spindle cells 1. KSHV is the infectious cause of Kaposi sarcoma 5,6. In vitro, KSHV can infect both micro-and macrovascular endothelial cells, and these cells are useful to study the role of KSHV in the pathogenesis of Kaposi sarcoma 10-12 .

Kaposi's sarcoma (KS)-associated herpesvirus (KSHV) is the infectious cause of KS and is also linked to the pathogenesis of certain lymphoproliferations (4,14). It is proposed that KSHV latent proteins are directly involved in modulating signal transduction pathways and cellular circuits leading to uncontrolled cell proliferation (2).At the far right-hand end of the KSHV genome, open reading frame (ORF) K15 encodes a putative transmembrane protein in the same genomic location as the Epstein-Barr virus (EBV) latent membrane protein 2A (LMP2A) (5,7,12,39). K15 resembles LMP2A not only in genomic location but also in its splicing pattern and predicted protein structure. Two highly divergent forms of K15 have been identified: the predominant (P) and minor (M) forms (5, 12, 39). These two alleles possess only 33% amino acid identity yet retain 12 membrane-spanning domains and a putative cytoplasmic signal-transducing carboxyl terminus (C terminus) (5). The C terminus of K15 has potential signaling motifs, including Src homology 2 and 3 binding domains (SH2-B and SH3-B, respectively) (12). A CD8-K15 C-terminal chimeric protein was shown to be constitutively tyrosine phosphorylated within the SH2-B motif (5). Like LMP2A, this CD8-K15 chimeric protein modulates B-cell receptor (BCR) signal transduction. The mechanism(s) of signal transduction is unknown but appears to be distinct from that of LMP2A and does not involve intracellular free calcium mobilization (5).In addition, the C terminus of K15 has sequences similar to those found in EBV LMP1, including a putative tumor necrosis factor receptor-associated factor (TRAF) binding site. K15 therefore appears to be a hybrid of a distant evolutionary relative of both EBV LMP1 and LMP2A (13). The putative C terminus of K15 has been shown to interact with the TRAFs (12), and we have also shown that K15 can indeed activate NF-B via this putative TRAF binding site (unpublished data). By way of activating NF-B, LMP1 of EBV plays an essential role in EBV-induced transformation of B lymphocytes (3,16,21). NF-B activation also appears to be essential for the proliferation potential of KSHV positive primary effusion lymphoma (PEL) cells (22), but whether all of this NF-B activity in PEL cells is due to K15 expression is not yet known.Although K15 mRNA has been demonstrated in PEL cells (5, 12, 39), it is not known whether the K15 protein is actually expressed in latently infected tumor cells. The size of endogenous protein, its exact subcellular localization, and its cellular binding partners have not previously been determined.We generated a monoclonal antibody (MAb) against K15 and show here that when K15 cDNA is ectopically expressed we detect the predicted 50-kDa form as well as a series of smaller proteolytically cleaved forms, of which the 35-and 23-kDa species are predominant. Deletion of the initiator AUG of the K15 ORF abolished protein expression, suggesting that the 50-kDa form of K15 is a precursor which is subsequently proteolytically processed into smaller species. We ...

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Mesenchymal stem cells (MSCs) are promising tools for the treatment of diseases such as infarcted myocardia and strokes because of their ability to promote endogenous angiogenesis and neurogenesis via a variety of secreted factors. MSCs found in the Wharton’s jelly of the human umbilical cord are easily obtained and are capable of transplantation without rejection. We isolated MSCs from Wharton’s jelly and bone marrow (WJ-MSCs and BM-MSCs, respectively) and compared their secretomes. It was found that WJ-MSCs expressed more genes, especially secreted factors, involved in angiogenesis and neurogenesis. Functional validation showed that WJ-MSCs induced better neural differentiation and neural cell migration via a paracrine mechanism. Moreover, WJ-MSCs afforded better neuroprotection efficacy because they preferentially enhanced neuronal growth and reduced cell apoptotic death of primary cortical cells in an oxygen-glucose deprivation (OGD) culture model that mimics the acute ischemic stroke situation in humans. In terms of angiogenesis, WJ-MSCs induced better microvasculature formation and cell migration on co-cultured endothelial cells. Our results suggest that WJ-MSC, because of a unique secretome, is a better MSC source to promote in vivo neurorestoration and endothelium repair. This study provides a basis for the development of cell-based therapy and carrying out of follow-up mechanistic studies related to MSC biology.

We have investigated the expression and function of a novel protein encoded by open reading frame (ORF) K7 of Kaposi's sarcoma-associated herpesvirus (KSHV). Computational analyses revealed that K7 is structurally related to survivin-DEx3, a splice variant of human survivin that protects cells from apoptosis by an unde®ned mechanism. Both K7 and survivinDEx3 contain a mitochondrial-targeting sequence, an N-terminal region of a BIR (baculovirus IAP repeat) domain and a putative BH2 (Bcl-2 homology)-like domain. These suggested that K7 is a new viral antiapoptotic protein and survivin-DEx3 is its likely cellular homologue. We show that K7 is a glycoprotein, which can inhibit apoptosis and anchor to intracellular membranes where Bcl-2 resides. K7 does not associate with Bax, but does bind to Bcl-2 via its putative BH2 domain. In addition, K7 binds to active caspase-3 via its BIR domain and thus inhibits the activity of caspase-3. The BH2 domain of K7 is crucial for the inhibition of caspase-3 activity and is therefore essential for its anti-apoptotic function. Furthermore, K7 bridges Bcl-2 and activated caspase-3 into a protein complex. K7 therefore appears to be an adaptor protein and part of an anti-apoptotic complex that presents effector caspases to Bcl-2, enabling Bcl-2 to inhibit caspase activity. These data also suggest that survivin-DEx3 might function by a similar mechanism to that of K7. We denote K7 as vIAP (viral inhibitorof-apoptosis protein).

Background: Fusion transcripts are formed by either fusion genes (DNA level) or trans-splicing events (RNA level). They have been recognized as a promising tool for diagnosing, subtyping and treating cancers. RNA-seq has become a precise and efficient standard for genome-wide screening of such aberration events. Many fusion transcript detection algorithms have been developed for paired-end RNA-seq data but their performance has not been comprehensively evaluated to guide practitioners. In this paper, we evaluated 15 popular algorithms by their precision and recall trade-off, accuracy of supporting reads and computational cost. We further combine top-performing methods for improved ensemble detection.Results: Fifteen fusion transcript detection tools were compared using three synthetic data sets under different coverage, read length, insert size and background noise, and three real data sets with selected experimental validations. No single method dominantly performed the best but SOAPfuse generally performed well, followed by FusionCatcher and JAFFA. We further demonstrated the potential of a meta-caller algorithm by combining top performing methods to re-prioritize candidate fusion transcripts with high confidence that can be followed by experimental validation.Conclusion: Our result provides insightful recommendations when applying individual tool or combining top performers to identify fusion transcript candidates.

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LIM domains-containing protein 1 (LIMD1) is encoded at chromosome 3p21.3, a region commonly deleted in many solid malignancies. However, the function of LIMD1 is unknown. Here we show that LIMD1 specifically interacts with retinoblastoma protein (pRB), inhibits E2F-mediated transcription, and suppresses the expression of the majority of genes with E2F1-responsive elements. LIMD1 blocks tumor growth in vitro and in vivo and is down-regulated in the majority of human lung cancer samples tested. Our data indicate that LIMD1 is a tumor-suppressor gene, the protein product of which functionally interacts with pRB and the loss of which promotes lung carcinogenesis.lung cancer ͉ retinoblastoma