Biological purging of breast cancer cell lines using a replication-competent oncolytic virus in human stem cell autografts

Abstract

Summary:Autologous hematological stem cell transplantation (ASCT) is used for the treatment of many hematological and several solid cancers. ASCT, however, has proven disappointing as a therapeutic strategy for breast cancer. Our group and others have previously shown that breast cancer micrometastases found in patients' apheresis products (APs) predict shorter progression-free and overall survival. The implications of this finding are twofold: (i) contaminating tumor cells (CTCs) in AP reflect a higher systemic disease burden and/or (ii) reinfused CTCs contribute to relapse/progressive disease. To date, purging strategies have been disappointing. We have previously demonstrated the oncolytic properties of reovirus in in vitro, in vivo and ex vivo systems. In the present study, we tested the hypothesis that reovirus purges CTCs in a breast cancer cell line purging model. Reovirus-infected human breast cancer cell lines (HTB 133, HTB 132, SKBR3 and MCF7) exhibited cell death within days. Admixtures of AP with cells from breast tumor cell lines, which were then exposed to reovirus, showed complete purging of CTCs (assessed via flow cytometry/tumor cell outgrowth analysis) without deleterious effect on CD34 þ cells. Our results provide preclinical support for the ex vivo use of reovirus as a purging modality for breast cancer during ASCT.

Viral purging of haematological autografts: should we sneeze on the graft?

“…Table 2 summarizes the naturally occurring viruses or genetically engineered viral vectors that have been evaluated as purging agents over the past decade. [53][54][55][56][57][58][59][60][61][62][63][64][65][66][67][68] A large number of virally mediated approaches have been utilized ex vivo to purge contaminating tumour cells from autografts that report purging efficacies ranging from 2 to 6 log depletions of tumour cells (Table 2). Direct comparison of the purging efficacy of one purging strategy to another is difficult as both the methodology for MRD detection varies considerably between studies, that is, tumour cell outgrowth in methyl cellulose versus culture media; flow cytometry versus PCR (reverse transcriptase-PCR versus quantitative PCR) detection techniques.…”

Reovirus as a Viable Therapeutic Option for the Treatment of Multiple Myeloma

“…Previously, we have shown negligible adverse effects of reovirus on purified CD34þ human stem cells or AP under in vitro conditions (23,25). Human stem cells isolated from AP, treated with LV for 3 days, and transplanted into NOD/SCID mice showed similar re-population and lineage differentiation in comparison to the DV controls.…”

“…Harvested cells were assayed for viability and purity (CD34þ and CD45þ cells) using flow cytometry as previously described (23). We have previously shown no significant difference between DV and NV treatments (23,25) in different tumors as well as CD34þ stem cells and AP. Therefore, DV was selected as the most stringent control for all reovirus experiments.…”

Horizontal gene transfers and cell fusions in microbiology, immunology and oncology (Review)

“…Reoviral oncolysis is also effective in the case of certain malignant lymphoma cells (diffuse large B cell lymphoma), whereas other types of lymphoma cells are resistant (multiple myeloma, Burkitt's lymphoma, follicular lymphoma) (357). Stem cell preparations for transplants potentially contaminated with reovirussusceptible tumor cells could possibly be purged of contaminating tumor cells (358). In the mouse, a recombinant replicating VSV (rrVSV) targets HER2/neu + breast cancer peritoneal implants.…”