Interestingly, the percentage of IGF-1R+ cells (4.3%) in the single tumor derived from the sh-IGF-1R group was significantly less than that from the sh-Luc group (35.2%), whereas the percentage of CD24-CD44+ cells was similar between the two groups (34.9% and 37.2% in the sh-IGF-1R group and sh-Luc group, respectively) (see Figure S4D in Additional file 1). Here, CD24 is linked to neoplasm.