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BACKGROUND: Recent data suggest that cancer stem cells (CSCs) play an important role in cancer,as these cells possess enhanced tumor-forming capabilities and are responsible for relapses after apparently curative therapies have been undertaken. Hence,novel cancer therapies will be needed to test for both tumor regression and CSC targeting. The use of oncolytic vaccinia virus (VACV) represents an attractive anti-tumor approach and is currently under evaluation in clinical trials. The purpose of this study was to demonstrate whether VACV does kill CSCs that are resistant to irradiation and chemotherapy. METHODS: Cancer stem-like cells were identified and separated from the human breast cancer cell line GI-101A by virtue of increased aldehyde dehydrogenase 1 (ALDH1) activity as assessed by the ALDEFLUOR assay and cancer stem cell-like features such as chemo-resistance,irradiation-resistance and tumor-initiating were confirmed in cell culture and in animal models. VACV treatments were applied to both ALDEFLUOR-positive cells in cell culture and in xenograft tumors derived from these cells. Moreover,we identified and isolated CD44(+)CD24(+)ESA(+) cells from GI-101A upon an epithelial-mesenchymal transition (EMT). These cells were similarly characterized both in cell culture and in animal models. RESULTS: We demonstrated for the first time that the oncolytic VACV GLV-1h68 strain replicated more efficiently in cells with higher ALDH1 activity that possessed stem cell-like features than in cells with lower ALDH1 activity. GLV-1h68 selectively colonized and eventually eradicated xenograft tumors originating from cells with higher ALDH1 activity. Furthermore,GLV-1h68 also showed preferential replication in CD44(+)CD24(+)ESA(+) cells derived from GI-101A upon an EMT induction as well as in xenograft tumors originating from these cells that were more tumorigenic than CD44(+)CD24(-)ESA(+) cells. CONCLUSIONS: Taken together,our findings indicate that GLV-1h68 efficiently replicates and kills cancer stem-like cells. Thus,GLV-1h68 may become a promising agent for eradicating both primary and metastatic tumors,especially tumors harboring cancer stem-like cells that are resistant to chemo and/or radiotherapy and may be responsible for recurrence of tumors. View Publication

Breast cancer is a heterogenous disease,composed of tumour cells with differing gene expressions and phenotypes. Very few antigens have been identified and a better understanding of tumour initiating-cells as targets for therapy is critically needed. Recently,a rare subpopulation of cells within tumours has been described with the ability to: (i) initiate and sustain tumour growth; (ii) resist traditional therapies and allow for secondary tumour dissemination; and (iii) display some of the characteristics of stem cells such as self-renewal. These cells are termed tumour-initiating cells or cancer stem cells,or alternatively,in the case of breast cancer,breast cancer stem cells. Previous studies have demonstrated that breast cancer stem cells can be enriched for in tumoursphere" culture. Proteomics represents a novel way to investigate protein expression between cells. We hypothesise that characterisation of the proteome of the breast cancer line MCF-7 tumourspheres compared to adherent/differentiated cells identifies proteins of novel interest for further isolating or targeting breast cancer stem cells. We present evidence that: (i) the proteome of adherent cells is different to the proteome of cells grown in sphere medium from either early passage (passage 2) or late passage (passage 5) spheres; (ii) that spheres are enriched in expression of a variety of tumour-relevant proteins (including MUC1 and Galectin-3); and (iii) that targeting of one of these identified proteins (galectin-3) using an inhibitor (N-acetyllactosamine) decreases sphere formation/self-renewal of MCF-7 cancer stem cells in vitro and tumourigenicity in vivo. Hence� View Publication

Most forms of chemotherapy employ mechanisms involving induction of oxidative stress,a strategy that can be effective due to the elevated oxidative state commonly observed in cancer cells. However,recent studies have shown that relative redox levels in primary tumors can be heterogeneous,suggesting that regimens dependent on differential oxidative state may not be uniformly effective. To investigate this issue in hematological malignancies,we evaluated mechanisms controlling oxidative state in primary specimens derived from acute myelogenous leukemia (AML) patients. Our studies demonstrate three striking findings. First,the majority of functionally defined leukemia stem cells (LSCs) are characterized by relatively low levels of reactive oxygen species (termed ROS-low"). Second� View Publication

The development of effective cancer vaccines remains an urgent,but as yet unmet,clinical need. This deficiency is in part due to an incomplete understanding of how to best invoke dendritic cells (DC) that are crucial for the induction of tumor-specific CD8(+) T cells capable of mediating durable protective immunity. In this regard,elevated expression of the transcription factor X box-binding protein 1 (XBP1) in DC appears to play a decisive role in promoting the ability of DC to cross-present Ags to CD8(+) T cells in the therapeutic setting. Delivery of DNA vaccines encoding XBP1 and tumor Ag to skin DC resulted in increased IFN-? production by plasmacytoid DC (pDC) from skin/tumor draining lymph nodes and the cross-priming of Ag-specific CD8(+) T cell responses associated with therapeutic benefit. Antitumor protection was dependent on cross-presenting Batf3(+) DC,pDC,and CD8(+) T cells. CD103(+) DC from the skin/tumor draining lymph nodes of the immunized mice appeared responsible for activation of Ag-specific naive CD8(+) T cells,but were dependent on pDC for optimal effectiveness. Similarly,human XBP1 improved the capacity of human blood- and skin-derived DC to activate human T cells. These data support an important intrinsic role for XBP1 in DC for effective cross-priming and orchestration of Batf3(+) DC-pDC interactions,thereby enabling effective vaccine induction of protective antitumor immunity. View Publication