The invention relates to a device for selecting stem cells with a serum free medium for amplification of stem cells. The invention also relates to a method of treating or preventing diseases caused by cancer-related stem cells. The invention further provides a method of enhancing radiosensitivity of cancer-related stem cells comprising radiotherapy with resveratrol, and the cancer-related stem cell has stronger drug resistance. The present invention further provides that resveratrol promotes differentiation and inhibits teratoma/tumor formation in induced pluripotent stem cells (iPS) and embryonic stem cells.
