SLPI and cancer: Interestingly, CD133, also known as PROM1, is expressed at increased levels in acute myeloid leukaemia (AML) HSCs and has been documented as a marker of cancer stem cells (CSCs) in several human neoplasms, and its expression seems to predict unfavourable prognosis30, corroborating the hypothesis that increased SLPI may contribute to the leukaemogenesis process.