PTGS2 and squamous cell carcinoma: In the present model of squamous cell carcinoma, DMBA as an initiator is incorporated into LCs, and is metabolized to DMBA-3,4-diol-1,2-epoxide (DMBADE).(12) DMBADE is known to strongly induce keratinocytes during carcinogenesis.(12,23) We also showed that not only COX-2 but also mPGES-1 was overexpressed in squamous cell carcinoma of mouse skin, and they were co-localized in proliferated epidermal cancer cells.