POU5F1 and cancer: In this study, we show that among HIV-PIs, lopinavir (LPV), one of the most widely used HIV-PIs, efficiently distinguishes CSCs among cancer cells and selectively reduces proliferation and self-renewal of Oct-4-expressing CSCs isolated from different types of solid tumor.14 Hence, both the total population of cancer cells from the same tumor and healthy stem cells are only affected at higher drug concentrations.