This notion is derived from the observations that tumor growth in WT mice transplanted with Pld2−/− bone marrow cells was slower than that in Pld2−/− mice transplanted with Pld2−/− bone marrow cells, and that tumor growth in Pld2−/− mice transplanted with WT bone marrow cells tended to be stimulated compared with that in WT mice transplanted with WT bone marrow cells (Fig. 3b). The gene discussed is PLD2; the disease is neoplasm.