NGFR and neoplasm: Overall, the CD44+ cells had greater capacity to form xenograft tumors compared to the CD44− cells, but when low numbers of cells were injected, it was clear that the CD44+CD271+ cells had the greatest capacity to form tumors among these three populations (Table 2); The tumors that formed in mice implanted with the CD44+CD271+ cells recapitulated the heterogeneity seen in the parental tumor (Supplemental Figure 3).