CD44 and neoplasm: The impact of fibroblasts became stronger at higher densities, i.e., a CD44+ LS1034 fraction of about 10% was observed after 4 days of co-culturing when (1.2-1.3)×104 fibroblasts per cm2 culture surface were seeded 24 h prior to the addition of the same number of tumor cells (Figure 7C, Table 1).