Killing of p53-deficient hepatoma cells by parvovirus H-1 and chemotherapeutics requires promyelocytic leukemia protein.

Aim: To evaluate the synergistic targeting and killing of human hepatocellular carcinoma (HCC) cells lacking p53 by the oncolytic autonomous parvovirus (PV) H-1 and chemotherapeutic agents and its dependence on functional promyelocytic leukemia protein (PML).

Methods: The role of p53 and PML in regulating cytotoxicity and gene transfer mediated by wild-type (wt) PV H-1 were explored in two pairs of isogenic human hepatoma cell lines with different p53 status. Furthermore, H-1 PV infection was combined with cytostatic drug treatment.

MCP-3 (CCL7) delivered by parvovirus MVMp reduces tumorigenicity of mouse melanoma cells through activation of T lymphocytes and NK cells.

Monocyte chemotactic protein 3 (MCP-3/CCL7), a CC chemokine able to attract and activate a large panel of leukocytes including natural killer cells and T lymphocytes, could be beneficial in antitumor therapy. Vectors were constructed based on the autonomous parvovirus minute virus of mice (MVMp), carrying the human (MCP-3) cDNA. These vectors were subsequently evaluated in the poorly immunogenic mouse melanoma model B78/H1.

Humoral immune responses against minute virus of mice vectors.

Background: Owing to their oncolytic properties, autonomous rodent parvoviruses and derived vectors constitute potential anti-tumor agents.

Methods: Humoral immune responses to minute virus of mice (MVMp) were characterized. In particular, the generation of neutralizing antibodies on subsequent therapeutic virus applications was evaluated in a mouse melanoma model.

Parvovirus H-1-induced tumor cell death enhances human immune response in vitro via increased phagocytosis, maturation, and cross-presentation by dendritic cells.

Oncotropic and oncolytic viruses have attracted high attention as antitumor agents because they preferentially kill cancer cells in vitro and reduce the incidence of spontaneous, induced, or implanted animal tumors. Some autonomous parvoviruses (H-1, minute virus of mice) and derived recombinant vectors are currently under preclinical evaluation. Still not fully understood, their antitumor properties involve more than just tumor cell killing.

The infectivity and lytic activity of minute virus of mice wild-type and derived vector particles are strikingly different.

Gene therapy vectors have been developed from autonomous rodent parvoviruses that carry a therapeutic gene or a marker gene in place of the genes encoding the capsid proteins. These vectors are currently evaluated in preclinical experiments. The infectivity of the vector particles deriving from the fibroblastic strain of minute virus of mice (MVMp) (produced by transfection in human cells) was found to be far less (approximately 50-fold-less) infectious than that of wild-type virus particles routinely produced by infection of A9 mouse fibroblasts.

Cancer gene therapy through autonomous parvovirus--mediated gene transfer.

Parvoviruses are small nuclear replicating DNA viruses. The rodent parvoviruses are usually weakly pathogenic in adult animals, bind to cell surface receptors which are fairly ubiquitously expressed on cells, and do not appear to integrate into host chromosomes during either lytic or persistent infection. The closely related rodent parvoviruses MVM, H-1 and LuIII efficiently infect human cell lines.

Vectors based on autonomous parvoviruses: novel tools to treat cancer?

Autonomous parvoviruses are small nuclear-replicating DNA viruses. The rodent parvoviruses usually are non- or weakly pathogenic in adult animals, bind to surface receptors which are expressed on most cells, and do not appear to integrate into host chromosomes during either lytic or persistent infections. Interestingly, malignant transformation of the target cells was often found to correlate with an increase in their capacity for amplifying and/or expressing the incoming parvoviral DNA, and is associated with oncolysis, i.

Parvovirus H-1 infection of human glioma cells leads to complete viral replication and efficient cell killing.

The extremely poor prognosis of malignant gliomas requires the investigation of other than standard therapies, i.e., the application of oncolytic viruses.

Oncolytic parvovirus H1 induces release of heat-shock protein HSP72 in susceptible human tumor cells but may not affect primary immune cells.

Certain autonomous parvoviruses preferentially replicate in and kill in vitro-transformed cells and may reduce the incidence of spontaneous and implanted tumors in animals. Hence, these viruses and their derivatives are currently under evaluation as antitumor vectors. However, the mechanisms underlying their tumor-suppressing properties are not yet understood.

Production of recombinant H1 parvovirus stocks devoid of replication-competent viruses.

Vector and helper plasmids for the production of recombinant H1 (rH1) parvovirus, an oncolytic virus and candidate vector for cancer gene therapy, were constructed with the aim of reducing the contamination of these preparations with replication-competent viruses (RCV). Split-helper plasmids were constructed by manipulating the splicing signals for the capsid proteins such that VP1 and VP2 were expressed from separate plasmids. H1 vectors with similarly mutated splice sites were packaged, using the split-helper plasmids, and the resulting recombinant H1 viruses were completely free of RCV because the generation of recombinants expressing both capsid proteins was prevented.

Suppression of metastatic hemangiosarcoma by a parvovirus MVMp vector transducing the IP-10 chemokine into immunocompetent mice.

We have previously shown that the growth of human tumor xenografts in immunodeficient mice can be efficiently suppressed upon infection with the autonomous parvovirus H-1 or with cytokine-transducing derivatives thereof. To further evaluate the benefits of implementing parvoviruses in cancer gene therapy, we have created a new recombinant vector, MVMp/IP-10, transducing the immunoactive, antiangiogenic chemokine IP-10, and used this virus to treat syngeneic tumors grown in immunocompetent mice. Intratumoral/intraperitoneal administration of only 3 x 10(7) replication units of MVMp/IP-10 per animal strongly inhibited the progression of established H5V cell-induced vascular tumors, a highly malignant mouse model for human cavernous hemangioma and Kaposi's sarcoma.