Sarcoma | EPFL Graph Search

A sarcoma is a malignant tumor, a type of cancer that arises from transformed cells of mesenchymal (connective tissue) origin. Connective tissue is a broad term that includes bone, cartilage, fat, vascular, or hematopoietic tissues, and sarcomas can arise in any of these types of tissues. As a result, there are many subtypes of sarcoma, which are classified based on the specific tissue and type of cell from which the tumor originates. Sarcomas are primary connective tissue tumors, meaning that they arise in connective tissues. This is in contrast to secondary (or "metastatic") connective tissue tumors, which occur when a cancer from elsewhere in the body (such as the lungs, breast tissue or prostate) spreads to the connective tissue. Sarcomas are one of five different types of cancer, classified by the cell type from which they originate. The word sarcoma is derived from the Greek σάρκωμα sarkōma 'fle

On the replication of adeno-associated virus in the presence or absence of viral helper functions

Anika Ekrut

Adeno-associated virus (AAV) is a small non-enveloped virus and as a member of the parvovirus family, it contains a single stranded DNA genome. AAV's life cycle in vitro is strongly dependent not only on cellular factors but also on helper functions provided by other viruses, for example adenovirus, herpes virus and, to a certain extent, papillomavirus (HPV). Although AAVs are wide spread throughout the human population, no disease is yet associated with them. Accordingly, AAV became attractive as a vector for gene therapy studies, but even though the virus is well studied in vitro and now used in clinical trials as a vector, not much is known about AAV infection in vivo. AAV was initially isolated from humans together with its helper adenovirus. However, adenovirus-independent replication of AAV has been reported for a number of cellular situations, including differentiating keratinocytes with or without the presence of HPV, and in cells with an activated DNA damage response due to genotoxic agents. In the work reported here we have undertaken a systematic study of these alternative helper activities with a view to evaluating their contribution to natural infections by AAV. We used three different systems of cultured keratinocytes and showed that in each case in vitro differentiation was achieved. In two of these, the cells were from HPV-induced lesions. We found that AAV replicates efficiently in differentiating monolayer foreskin keratinocytes in the presence but not in the absence of adenovirus. Likewise naturally HPV-infected cervical keratinocytes only support the full life cycle of AAV if adenovirus is present. Even though HPV can provide certain helper functions, it is less efficient as a helper than adenovirus. We also exploited osteosarcoma cells, which are particularly well infected by AAV. Our results indicate that U2OS osteosarcoma cells are semi-permissive for AAV growth. Induction of a DNA damage response in these cells, or in HPV-containing keratinocytes, stimulates AAV genome amplification. Although AAV replication in the absence of helper virus can readily be demonstrated, this is either at a relatively low level or limited to part of the AAV growth cycle. We conclude that although these alternative helper systems can contribute to the natural history of AAV, the presence of an efficient helper virus seems likely to be needed for AAV to persist in the human population.

EPFL2009

Adeno-Associated Virus Activates an Innate Immune Response in Normal Human Cells but Not in Osteosarcoma Cells

Peter Martin Beard

Adeno-associated virus (AAV) is a small, DNA-containing dependovirus with promising potential as a gene delivery vehicle. Given the variety of applications of AAV-based vectors in the treatment of genetic disorders, numerous studies have focused on the immunogenicity of recombinant AAV. In general, AAV vectors appear not to induce strong inflammatory responses. We have found that AAV2, when it infects the osteosarcoma cells U2OS, can initiate part of its replicative cycle in the absence of helper virus. This does not occur in untransformed cells. We set out to test whether the cellular innate antiviral defenses control this susceptibility and found that, in nonimmune normal human fibroblasts, AAV2 induces type I interferon production and release and the accumulation of nuclear promyelocytic leukemia bodies. AAV fails to mobilize this defense pathway in the U2OS cells. This permissiveness is in large part due to impairment of the viral sensing machinery in these cells. Our investigations point to Toll-like receptor 9 as a potential intracellular sensor that detects AAV2 and triggers the antiviral state in AAV-infected untransformed cells. Efficient sensing of the AAV genome and the ensuing activation of an innate antiviral response are thus crucial cellular events dictating the parvovirus infectivity in host cells.

2011

Growth of osteosarcoma cells in a three-dimensional bone-like matrix alters their susceptibility to adeno-associated virus

Peter Martin Beard, Katarina Damjanovic, Sangeeta Dey, Martha Luise Müller

Osteosarcoma cells U2OS are partially susceptible to adeno-associated virus (AAV)-2 infection, allowing efficient synthesis of Rep proteins and, in a low percentage of cells, capsid production. It is not clear if this partial susceptibility to infection is due to the bone-cell-like nature of these cells or is a result of their transformed properties. Here, we grew osteosarcoma cells in a biomimetic three-dimensional bone-like matrix composed of calcium phosphate and chitosan, and tested whether this would increase or reduce their permissiveness to virus. The osteosarcoma cells grew in the matrix and began to express the alkaline phosphatase bone cell differentiation marker. This was accompanied by a block to their infection by AAV, as indicated by Rep and capsid production. Infection of cells growing in three-dimensional tissue-like matrices could be, in a wider context, a practical way to mimic in vivo conditions.

Soc General Microbiology2014

On the replication of adeno-associated virus in the presence or absence of viral helper functions

Anika Ekrut

EPFL2009