Induction Of Long-term Survival Research Articles

Combining DC-mediated immunotherapy with oncolytic virotherapy in the treatment of HGG

Oncolytic viruses (OV) are either naturally selective for neoplastic cells or are engineered to be so. Whereas conservative therapies use the unspecific genome vulnerability of highly proliferating cells to target malignancies, OV have the advantage of often being extremely specific in infecting tumor cells. This (intrinsic) selectivity combined with the demonstrated safety and lack of host toxicity in phase I clinical studies make OV very appealing as novel cancer therapeutics. Recently, Alkassar et al. have shown in vitro and in vivo that naturally occurring Reovirus, Parvovirus and Newcastle disease virus (NDV) strains mediate strong anti-tumoral effects on glioblastoma. We hypothesize that upon combining a systemic immunotherapy approach with preceding oncolytic virotherapy (OVT), as a means of lowering the tumor viability and volume and altering the local micro environment within the tumor, a better immune control can be induced. In the immunotherapy field, it is known that the immunosuppressive microenvironment induced by the tumor can profoundly suppress the antitumor immunity and therefore inhibit vaccine efficacy. Viral presence within the tumor does the opposite; acting as a danger signal to alert and activate the immune system, it can reduce or eliminate the tumor induced immune suppression. Furthermore, the direct tumor cell killing effects of OV can lower tumor burden prior to immunotherapy. Both active specific immunotherapy and OVT have shown promising results in preclinical and clinical studies but the possible additive or synergistic effects of these treatment strategies have not been studied. We aim to combine OVT with dendritic cell (DC)-mediated immunotherapy in a preclinical murine glioma model to demonstrate additive or synergistic effects. Our initial results show good susceptibility of the murine GL261 glioma cell line to cytotoxic killing by oncolytic Reovirus, Parvovirus and NDV in vitro. The strains were also combined to exploit the synergism recently demonstrated by Alkassar et al. Results indicate increased cytotoxic effects when Reovirus was combined with NDV or when Reovirus was combined with Parvovirus. GL261 cell infection capacity of the viruses was quantified by immunofluorescence imaging. In vivo, intracranial injection of Reovirus, Parvovirus, NDV or combinations of two viruses in healthy mice led to signs of inflammation in the brain, as visualized by MR imaging. Infiltration of inflammatory cells will be confirmed by histology. In tumor-bearing mice, prolonged survival and induction of long term survival was seen when mice were treated intra tumorally with Reovirus, Parvovirus or a combination of both. Similar results were found when tumor-bearing mice were treated with NDV and/or Reovirus. Toxicity of the viruses will be analyzed by histological analysis of brain and other vital organs.

A short course of high-dose cyclophosphamide induces long-term survival of intestinal allografts in mice.

Several transplant programs have recently added cyclophosphamide (CyP) to their immune suppression protocols in an attempt to reduce intestinal graft rejection rates. The present study was undertaken to confirm the benefits of this drug in a murine small bowel transplant model. A short course of monotherapy with CyP 20 mg/kg per dose resulted in a mean survival time (MST) of 17.5 +/- 3.6 days, compared with a MST of 7.5 +/- 0.7 days in the untreated controls (P < 0.01). Cyclosporin A (CsA) 30 mg/kg per day produced comparable survival rates when used as monotherapy (MST: 14.2 +/- 1.3 days) or in combination with CyP 20 mg/kg per dose (MST: 21.3 +/- 5.1 days). Treatment with high dose CyP (40 mg/kg per dose) completely prevented graft loss in 8 of 10 animals (MST: 72.5 +/- 5.3 days, P < 0.01). However, adding CsA abrogated the induction of long-term survival achieved by CyP alone (MST: 23 +/- 0.4 days). These data have important implications for the use of CyP in clinical transplantation.

Doxorubicin plus tumor necrosis factor alpha combination treatments in EL4-lymphoma-bearing C57BL/6 mice.

The therapeutic efficacy of a total of 42 single-agent or combination protocols involving doxorubicin (Adriamycin, ADM) and tumor necrosis factor alpha (TNFalpha) were evaluated in the syngeneic murine lymphoma model, C57BL/6-EL4. Combination treatments were the most effective and the therapeutic effects were schedule-dependent; e.g. it was generally advantageous for ADM to precede TNFalpha administration. Two protocols selected for further study were 4 mg/kg ADM i.v. on days 1 and 8 plus TNFalpha, i.v., at either 16000 U (7 microg)/injection, on days 1 and 8 or 4000 U (1.7 microg)/injection, on days 11-15. Survival of mice bearing one of four EL4 sublines having different in vitro drug sensitivities was assessed. These sublines were E10 (ADM-sensitive/TNFalpha-resistant), E16 (sensitive/sensitive), ER2 (ADM-resistant/TNFalpha-sensitive) and ER13 (resistant/resistant). Between 80% and 100% long-term survivors (i.e. tumor free on day 60) were obtained with the two treatments in mice bearing ADM-sensitive sublines, even though one of these sublines, E10, was resistant to TNFalpha in vitro. Induction of long-term survival appeared, therefore, to correlate with in vitro defined sensitivity/resistance to ADM, but not to TNFalpha Treatment-induced modulations of tumoricidal immune effector functions were also examined. Taken together, the results indicated that induction of long-term survival involved complex interactions of: (1) ADM-induced tumor modifications, including, but not limited to, tumor debulking, (2) combination-treatment-induced modifications of splenic cytolytic T cell and macrophage activities, and (3) the restoration of thymus cellularity. Finally, when long-term survivors resulting from treatment of E10- or E16-bearing mice were implanted with ER2 on day 120, the majority survived, indicating that long-term immune memory, capable of recognizing drug resistant variants, had been established.