The invention provides isolated cell populations comprising placental stem cells, wherein said placental stem cells (a) adhere to a substrate, (b) express specific cells markers, and (c) detectably suppress proliferation of a plurality of tumor cells, as compared to a plurality of tumor cells not contacted with placental stem cells. Methods of producing a cell population comprising placental stem cells, compositions comprising the isolated placental stem cell population, and the isolated placental stem cell population for use in a method for treatment of an individual having tumor are also provided.
