CD44 and neoplasm: CD44+ positive cells were isolated from primary tumor cell cultures (Figure 1a) (i.e., separated from the remaining CD44− cells) by a magnetic-activated cell sorting (MACS) system, and the further expanded (Figure 1b,c) MACS isolated cells were validated by flow-cytometry, resulting in over 92% of the population expressing CD44 (the data are not shown).