CD24 and neoplasm: When the number of the injected cells was increased to 8 × 106/mouse, MCF-7 and SK-BR-3 that had the lowest CD44/CD24 ratio still could not form tumors, while tumor growth was observed for mice injected with MDA-MB-468 cells bearing the moderate CD44/CD24 ratio, though the tumor growth was much slower than MDA-MB-231 ones: the size of the generated tumor reached 93.21 mm3 for MDA-MB-468 after 48 days, compared to 670 mm3 for MDA-MB-231 at the same stage (Supplementary Figure S2B, S2C).