David Momier

Preventive Cancer Stem Cell‐Based Vaccination Reduces Liver Metastasis Development in a Rat Colon Carcinoma Syngeneic Model

Cancer stem cells (CSCs) represent a minor population of self‐renewing cancer cells that fuel tumor growth. As CSCs are generally spared by conventional treatments, this population is likely to be responsible for relapses that are observed in most cancers. In this work, we analyzed the preventive efficiency of a CSC‐based vaccine on the development of liver metastasis from colon cancer in a syngeneic rat model. We isolated a CSC‐enriched population from the rat PROb colon carcinoma cell line on the basis of the expression of the aldehyde dehydrogenase‐1 (ALDH1) marker. Comparative analysis of vaccines containing lysates of PROb or ALDHhigh cells by mass spectrometry identifies four proteins specifically expressed in the CSC subpopulation. The expression of two of them (heat shock protein 27‐kDa and aldose reductase) is already known to be associated with treatment resistance and poor prognosis in colon cancer. Preventive intraperitoneal administration of vaccines was then performed before the intrahepatic injection of PROb cancer cells. While no significant difference in tumor occurrence was observed between control and PROb‐vaccinated groups, 50% of the CSC‐based vaccinated animals became resistant to tumor development. In addition, CSC‐based vaccination induced a 99.5% reduction in tumor volume compared to the control group. To our knowledge, this study constitutes the first work analyzing the potential of a CSC‐based vaccination to prevent liver metastasis development. Our data demonstrate that a CSC‐based vaccine reduces efficiently both tumor volume and occurrence in a rat colon carcinoma syngeneic model. STEM CELLS2013;31:423–432

RANKL Treatment Releases the Negative Regulation of the Poly(ADP-Ribose) Polymerase-1 on Tcirg1 Gene Expression During Osteoclastogenesis†

The Tcirg1 gene encodes the osteoclast‐specific a3 isoform of the V‐ATPase a subunit. Using the mouse osteoclastic model RAW264.7 cells, we studied Tcirg1 gene expression, and we identified PARP‐1 as a transcriptional repressor negatively regulated by RANKL during osteoclastogenesis.

Differential binding of poly(ADP-ribose) polymerase-1 and JunD/Fra2 accounts for RANKL-induced Tcirg1 gene expression during osteoclastogenesis

We studied Tcirg1 gene expression on RANKL‐induced osteoclastic differentiation of the mouse model RAW264.7 cells. We identified a mechanism involving PARP‐1 inhibition release and JunD/Fra‐2 binding, which is responsible for Tcirg1 gene upregulation.

Poly(adp‐ribose) Polymerase‐1 Regulates Tracp Gene Promoter Activity During RANKL‐Induced Osteoclastogenesis

The Tracp gene encodes an acid phosphatase strongly upregulated during osteoclastogenesis on RANKL treatment. Using the mouse osteoclastic model RAW264.7, we studied Tracp gene expression, and we identified PARP‐1 as a transcriptional repressor negatively regulated by RANKL during osteoclastogenesis.

Tumor microenvironment modifications induced by soluble VEGF receptor expression in a rat liver metastasis model

Vascular endothelial growth factor is a potent pro-angiogenic growth factor which is also known to alter tumor microenvironment by inhibiting dendritic cell differentiation and promoting accumulation of myeloid-derived suppressor cells. In the present study, we analyzed the modifications induced by intratumoral expression of sFLT-1, a soluble VEGF receptor, in a rat metastatic colon carcinoma model. We generated colon cancer cell lines stably expressing sFLT-1 or a mock construct. Human umbilical vein endothelial cells cultured with conditioned medium from sFLT-1-expressing tumor cells exhibit a significantly decreased survival, demonstrating the functionality of the secreted sFLT-1. Invivo, sFLT-1 expression induced a 30% decrease in microvessel density in 15-day old experimental liver metastasis from colon carcinoma. Tumor growth was inhibited by 63% and 52% in left and right liver lobes respectively within 25days. In these tumors, sFLT-1 expression was associated with a decreased myeloid cell infiltration and a modification in the expression of several cytokines/chemokines. Altogether, these results suggest that VEGF trapping by sFLT-1 intratumoral expression results in reduced vascularization, tumor growth inhibition and modification of immune tumor microenvironment.

Monocytes differentiation upon treatment with a peptide corresponding to the C-terminus of activated T cell-expressed Tirc7 protein

Atp6v0a3 gene encodes for two alternative products, Tirc7 and a3 proteins, which are differentially expressed in activated T cells and resorbing osteoclasts, respectively. Tirc7 plays a central role in T cell activation, while a3 protein is critical for osteoclast‐mediated bone matrix resorption. Based on the large body of evidences documenting the relationships between T cells and osteoclasts, we hypothesized that the extracellular C‐terminus of Tirc7 protein could directly interact with osteoclast precursor cells. To address this issue, we performed the molecular cloning of a mouse Atp6v0a3 cDNA segment encoding the last 40 amino acids of Tirc7 protein, and we used this peptide as a ligand added to mouse osteoclast precursor cells. We evidenced that Tirc7‐Cter peptide induced the differentiation of RAW264.7 cells into osteoclast‐like cells, stimulated an autocrine/paracrine regulatory loop potentially involved in osteoclastic differentiation control, and strongly up‐regulated F4/80 protein expression within multinucleated osteoclast‐like cells. Using a mouse bone marrow‐derived CD11b+ cell line, or total bone marrow primary cells, we observed that similarly to Rankl, Tirc7‐Cter peptide induced the formation of TRACP‐positive large multinucleated cells. At last, using mouse primary monocytes purified from total bone marrow, we determined that Tirc7‐Cter peptide induced the appearance of small multinucleated cells (3–4 nuclei), devoid of resorbing activity, and which displayed modulations of dendritic cell marker genes expression. In conclusion, we report for the first time on biological effects mediated by a peptide corresponding to the C‐terminus of Tirc7 protein, which interfere with monocytic differentiation pathways. J. Cell. Physiol. 227: 3088–3098, 2012.