POU5F1 and pachyonychia congenita: In the present work, PC cells derived from 5-FU treated tumorspheres were enriched in Notch (Notch1+, Notch3+ and Notch4+), PCSC (CD24+CD44+ESA+ and c-Met+), pluripotency (Oct-4+, SOX-2+, Nanog+) and EMT (N-cadherin+) markers, which are features associated with highly aggressive PC tumors [55].