CD44 and cancer: The surviving fractions for the cancer stem-like CD44+/CD24- and non-cancer stem like CD44-/CD24- cells sorted from MDA-MB-231 irradiated with X-rays and carbon ion beams decreased exponentially with increasing doses, and CD44-/CD24- cells more significantly decreased compared to that of CD44+/CD24- cells after irradiation with either X-rays or carbon ion beams (Fig. 3a).