Abstract 396: Reovirus successfully purges multiple myeloma ex vivo and does not affect human CD34+ cell engraftment in a murine transplantation model.
Authors: Thirukkumaran Chandini M. , Shi Zhong-Qiao , Luider Joanne , Stewart Douglas , Kopciuk Karen A. , Gao He , Morris Don 
Published: February 2011

Introduction: Multiple Myeloma (MM) is an incurable cancer that accounts for 10% of hematological malignancies. Stem cell rescue following high-dose chemotherapy with autologous or allogenic transplantation has become standard therapy for a subset of good performance patients. Previously we have shown that reovirus, a double stranded RNA virus can successfully purge the RPMI 8226 MM cell line, as well as a patient tumor specimen with no effect on stem cells (Thirukkumaran et al. 2004 : Blood. 102:377-387). In the present study we demonstrate 1) Efficient reovirus ex vivo purging of MM in a murine model of transplantation. 2) Reovirus purging does not affect human CD34+ stem cell repopulation or lineage differentiation.

Methods: RPMI 8226-GFP MM cell line was admixed with human apheresis cells (AP) to represent 1% tumor burden. Admixed products were purged with live (LV) or UV-inactivated (DV) reovirus at a multiplicity of infection (MOI) of 40 for 72 hours. To assess purging efficacy and stem cell repopulating ability, SCID/NOD mice were sublethally irradiated and intraperitoneally injected with anti-asialo antibody to eradicate NK cells. Mice were injected intravenously with either live or dead virus purged admixed apheresis cells. Mice showing symptoms of disease were sacrificed and subjected to whole body fluorescence imaging using a GFP Imaging System. Bone marrow cells were collected from mouse femurs and analyzed for CD38+/138+/GFP+ MM cells. Human CD34+ stem cells were isolated from AP cells using Robosep (Stem Cell technologies) and exposed to LV or DV for 72 hours. LV (n=8) and DV (n=5) virus purged stem cells were mixed with sublethally irradiated (2Gy) AP cells (5X 105) and injected into irradiated SCID/NOD mice. Mouse blood and bone marrow was harvested at days 25 or 35 and assessed for human stem cells (CD34+/ 45+), T cells (45+/3+), B cells (19+/45+), NK cells(45+/3-/16+/33+) and myeloid (45+/13+/33+) cells.

Results: 100% of LV purged animals (unlike DV purged) were devoid of MM and survived until being sacrificed arbitrarily at day 110 (Kaplan-Meier analysis: p&lt; 0.0012). Both LV and DV purged human stem cells showed re-population in mice and lineage differentiation illustrating a lack of viral effect.

Conclusions: The sensitivity of reovirus towards MM and its lack of effect on human stem cells highlight the potential of reovirus as an ex vivo purging agent during autologous hematopoietic stem cell transplants for MM. Currently, we are in the process of studying reovirus purging efficacy of ex vivo MM patient tumor in order to generate data for a future phase I clinical trial.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 396.