Parvovirus Host Cell Interactions
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Summary
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- Identification of potential marker/functions promoting neoplastic transformation. In naturally permissive cells, rodent PVs stimulate the PDK1/PKB/PKC signalling cascade to counteract stress responses and to ensure productive infection and spreading. Upon host switch to human cells, PVs strongly depend on this signalling pathway to be activated. This makes cancer cells ideal hosts for PV. Complementarities between PV interference in natural host cells and factors promoting permissiveness in human cancer cells are thought to serve as markers for neoplastic transformation.
- By studying molecular mechanisms of PV induced egress and oncolysis we intend to design novel PV-derived oncotoxins to arm heterologous viruses for Virotherapy of Cancer and to improve the induction of a bystander effect by inducing an anti-tumor immune response.
To generate a portfolio of self-propagating oncolytic (parvo)viruses for a virotherapy of cancer aiming to provide a panel of therapeutics for patient-tailored and to establish pre-treatment diagnostics.
Current and future projects
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PV Interference with intracellular signalling cascades
Regulation of the PV non-structural protein NS1 is strongly dependent on the PDK1/PKC/PKB signalling cascade. Conversely PVs, particularly MVM was shown to interfere with this pathway, leading to activation of PDK1 and its downstream targets PKCλ the short-lived PKCη and PKB/Akt1 [1]. In addition we found that ERM family proteins (mediators between actin cytoskeleton and membranes) play essential roles in the virus cycle, particularly at late stages of infection ensuring virus egress and cytolysis. Thus, radixin, in conjunction with PKCη was shown to modulate NS1 and capsid phosphorylation [2]. Moreover, we were able to show that Rdx/PKCη-complex targets PDK1 for phosphorylation and activation not only in MVM-infected A9 cells but constitutes an internal loop-back activation mechanisms in highly aggressive cancer cells such as glioblastoma multiforma, rendering PDK1 activity independent of its cofactor PIP3 and, hence growth factor signalling through PI3-kinase [3]. Currently we are aiming to determine PV-induced activation of the PDK1-downstream survival-kinase PKB/Akt1 and its action on PV-late functioning for progeny particle egress and spreading.
Cytotoxicity, Vesicular egress of progeny virions and oncolytic activity
During PV-infection oncolysis appears to be a tightly regulated process associated with the transport of progeny virions from the nuclear periphery to the plasma membrane. This pathway through ER and Golgi involves COPII vesicles and is necessary to introduce post-assembly modification leading to the maturation of progeny particles and induction of cell lysis ([9,10]). Besides progeny particles, intracellular vesicles contain viral and cellular polypeptides, which become exposed at the cell surface during the budding process (Steinfass et al., in prep.) and might be involved in cell lysis (Bretscher et al., in preparation). This is of interest, since intracellular tumor-associated antigens (TAAs) are transported as “co-cargoes” to the cellular periphery and might serve, together with viral antigens as DAMPs and PAMPs in order to attract the host immune system after oncolysis. In collaboration with Prof. Dr. Jörg Huwyler (Pharmaceutical Institute University Basel) these findings will be applied for the generation of PV-derived oncotoxins, allowing to mimic PV-induced oncolysis/induction of anti-tumor immune responses, independent of viral infections [11]. In order to obtain more insight into the mechanisms of PV-induced immune-activation, we are in close cooperation with Prof. Dr. Nathalia Giese, Uni HD [12], Dr. Laurent Daeffler (INSERM) and Prof. Markus Möhler, Uni Mainz to improve PV-associated cancer therapies through anti-tumor immune-activation.
(Parvo)Virotherapy of Cancer
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Tackling Safety Issues: Recently, genetic screens have identified human Protoparvoviruses, close relatives to the rodent species currently under evaluation for cancer therapies. So far, little is known about these viruses. However, we might obtain valuable information from these potential human pathogens about their life cycle and persistence in humans. Investigations about the properties of these viruses will be achieved in collaboration with Prof. Dr. Maria Söderlund-Venermo (University of Helsinki), allowing us to identify potential pitfalls, but also new avenues for targeting specific diseased tissues.
Significant Accomplishments
- Identification of activated PDK1 as a mediator of PV (onco) tropism
- Identification of phosphoPDK1 as a diagnostic/prognostic marker in human glioma
- Generation of new oncotoxins on the base of NS1 induced cytolysis
- Characterization of vesicular egress of PV through ER and Golgi
- Generation of H-1PV variants surpassing the wild type virus in anti-cancer activity
- Establishment of replication-competent molecular clones for KRV, H3, TVX, and X14.