Moreover, they identified three populations in normal and cancer keratinocyte cultures: a small but constant pool of Rh123− (Rhodamine 123, a marker of side population) and EGFR− quiescent cells, a small but variable in size between normal and cancer cell cultures pool of Rh123− /EGFR+ (perhaps activated stem cells), and a third major pool of Rh123+ /EGFR+ transient amplifying cells. This evidence concerns the gene EGFR and cancer.