H2BC21 and melanoma: Using an inducible H2B-GFP system to trace the cell divisional history in vitro, we identified quiescent/slow-cycling GFPhigh label-retaining CSCs in melanoma cell lines and showed that transient and chronic TNF suppresses melanoma SC differentiation while enriching for a GFPhigh melanosphere-initiating CSC subpopulation many generations after TNF withdrawal.