In this study we have found that when injected into the yolk sac there is a sudden reduction in the total number of tumor cells starting at 5 dpf, right after detection of the genes encoding T cell receptor subunit in the thymus and elevation of the recombination activation gene 1 (Rag-1) at 4 dpf 20, 21, consistent with the notion that the removal of these xenografted mouse tumor cells is a result of the immune response, possibly triggered by phosvitin in the yolk sac38. This evidence concerns the gene CSNK2B and neoplasm.