KRT14 and skin squamous cell carcinoma: While there was no difference in expression of K1 between cSCC tumors in Flii genetic mice, overexpression of Flii resulted in significantly increased levels of K14, a known marker of poorly differentiated keratinocytes and late-stage metastatic cSCC cells [32], in keratin pearls of cSCC tumors of FliiTg/Tg mice (Figure 5A,C,D), suggesting Flii promotion of metastatic progression in murine cSCC.