It has also become increasingly clear that soluble factors may not only directly stimulate the expansion of the tumor clone, e.g. BAFF, APRIL, IL-10, and IL-15 (39), but in some cases (bFGF, VEGF) they may also indirectly contribute to tumor growth by triggering angiogenesis and/or production of growth-promoting factors by the surrounding normal bone-marrow cells, i.e. osteoblasts, fibroblasts, and endothelial cells (40,41). The gene discussed is IL15; the disease is neoplasm.