Cytosolic Activation of Cathepsins Mediates Parvovirus H-1-Induced Killing of Cisplatin and TRAIL-Resistant Glioma Cells

Abstract

Gliomas are often resistant to the induction of apoptotic cell death as a result of the development of survival mechanisms during astrocyte malignant transformation. In particular, the overexpression of Bcl-2-family members interferes with apoptosis initiation by DNA-damaging agents (e.g., cisplatin) or soluble death ligands (e.g., TRAIL). Using low-passage-number cultures of glioma cells, we have shown that parvovirus H-1 is able to induce death in cells resistant to TRAIL, cisplatin, or both, even when Bcl-2 is overexpressed. Parvovirus H-1 triggers cell death through both the accumulation of lysosomal cathepsins B and L in the cytosol of infected cells and the reduction of the levels of cystatin B and C, two cathepsin inhibitors. The impairment of either of these effects protects glioma cells from the viral lytic effect. In normal human astrocytes, parvovirus H-1 fails to induce a killing mechanism. In vivo, parvovirus H-1 infection of rat glioma cells intracranially implanted into recipient animals triggers cathepsin B activation as well. This report identifies for the first time cellular effectors of the killing activity of parvovirus H-1 against malignant brain cells and opens up a therapeutic approach which circumvents their frequent resistance to other death inducers.

Activation of a glioma-specific immune response by oncolytic parvovirus Minute Virus of Mice infection

“…Caspase-3 activation was determined as previously described by Di Piazza et al 5 by adding 25 ml of whole-cell extract to caspase buffer (50 mM Hepes (pH 7.4), 150 mM NaCl, 0.1% CHAPS, 0.1% Triton X-100, 1 mM EDTA, 10% Glycerol, 10 mM DTT) supplemented with caspase 3 substrate (Ac-Asp-GluVal-Asp-AFC) at 1 mM concentration (Calbiochem, Darmstadt, Germany). The reaction was monitored for 1 h on a Fluoroscan (Thermo Labsystems Fluoroscan; Thermo Labsystems, Thermo Scientific, Erlangen, Germany) using excitation and emission wavelength of 390 and 510 nm, respectively.…”

“…4 In particular, the oncolytic rat H-1PV was shown to selectively target and kill cells derived from various cancer types, including cells originating from human gliomas. 5 The concept of H-1PV-based virotherapy of glioma was successfully tested in vivo, using rat (RG-2) and human (U87) glioma cell implants in immunocompetent and immunodeficient rat models, respectively. 6 It has to be stated that the therapeutic effect of the virus was more pronounced in immunocompetent animals.…”

Lysosomal membrane permeabilization in cell death

“…In addition, several viral proteins such as Nef from human immunodeficiency virus-1, protein U7 from human papillomavirus type-16, parvovirus H1 and herpes simplex virus infection induce LMP-and cathepsin-dependent cell death (Kaznelson et al, 2004;Di Piazza et al, 2007;Laforge et al, 2007). Cystatin C can block the enhanced CB activity observed in herpes simplex virus type-1-infected cells and concomitantly inhibits herpes simplex virus type-1 replication and host cell apoptosis (Peri et al, 2007).…”

Potential of tumour cells for delivering oncolytic viruses

“…19 In gliomas, furthermore, parvoviruses have been shown to induce a cathepsin-mediated cell death mechanism that might initiate maturation of antigen-presenting cells more effectively than physiological apoptosis of metastasizing cells. 20,21 (4) Another advantage worth mentioning is the possibility of using autologous tumour biopsies and derived ATCs to guide the choice of patient-tailored treatments. From a panel of potential candidates, it should be possible to select the most efficient OV against a given tumour.…”