The inventors have developed a metastatic 4T1 breast tumor model in BALB/c mice. They have shown that the vaccination with xenogeneic embryonic stem cells in combination with valproic acid (VPA) generates a higher anti-tumoral response against breast cancer and inhibits metastasis development. They established that these responses are achieved only by the addition of valproic acid in the therapeutic regimen in comparison to the use ESCs or iPSCs alone. Thus, the inventors provide a new therapeutic strategy to treat cancers expressing embryonic antigens. Accordingly, the present invention relates to i) a population of pluripotent cells and ii) a compound selected from a group which activates MHC expression, as a combined preparation for use in a method for treating a subject suffering from a cancer, comprising a step of administering simultaneously, separately or sequentially to said subject a therapeutically amount thereof.