A preformed
gelatin matrix containing adherent rat colon
carcinoma cells was transplanted subcutaneously into rats to analyze the outgrowth of the
tumor and the inflammatory response. The
gelatin matrix simplifies the precise localization of the
tumor cells early after implantation and allows the
gelatin piece with a growing
tumor to be dissected for analysis in vitro, after various times in vivo. The immortalized mesenchymal progenitor cell line MPC1cE was cocultured with rat colon
carcinoma cells in vivo in
gelatin matrix. The mesenchymal progenitor cells inhibited the outgrowth of the rat colon
carcinoma and a complete inhibition was seen if the number of mesenchymal progenitor cells were at least equal to the number of
tumor cells. The mixture of
tumor cells and mesenchymal progenitor cells induced more infiltration of monocytes and granulocytes than
tumor cells or mesenchymal progenitor cells alone. Infiltration of T cells and CD31+ endothelial cells correlated to the presence of
tumor cells and not to mesenchymal progenitor cells. These findings suggest that
tumor cell culture in vivo in a
gelatin matrix is effective for early localization of
tumor cells in vivo and that mesenchymal progenitor cells effectively inhibit the growth of the
tumor cells in vivo.