CD44 and neoplasm: FACS analyses, performed one week later, demonstrated that neither the CD44+/β1+ phenotype nor the CD44+/CD24low/− phenotype were fully retained; only a small fraction of the tumor cells remained CD44+/β1+ or CD44+/CD24low/− (2.0 ± 0.2% and 2.9 ± 1.6%, respectively; Table 1A), demonstrating that with time, the TME-enriched cell populations undergoes a phenotypic drift.