Since fibroblasts exhibiting high levels of PGE2 secretion also exhibited the most robust increase in cancer stem-like cells and promoted the largest MCF7 tumor formation, we reasoned that paracrine production of PGE2 by fibroblasts might be sufficient to expand CD44+/CD24−/EpCAM+ MCF7 stem-like cells. The gene discussed is CD44; the disease is neoplasm.