THY1 and cancer: Increasing evidence denotes a minority population of cells within tumors, termed cancer stem cells (CSCs), as critical determinants in cancer recurrence, metastasis, and therapy resistance.10 CSCs have been identified by several cell surface markers, such as CD133,11 CD44,12 and CD90.13 However, neutralizing antibodies against these markers have proven insufficient in eradicating CSCs in preclinical studies, and identification of new therapeutic targets against CSCs is necessary.