Cultured normal human oral kera tinocyte(NHOK) & inunortalized human oral keratinocyte(IHOK) provide a valuable model in ce llular proliferation and differentiation after proper stimulation , And it is interesting to study these estab lished cell lines esca ping normal control on their growth and differentiation, SPRR1 is induced during t erminal differ entiation 0 1' human epiderma l kerat inocytes but is rarely in anaplastic cells of keratinocyte origin, But SPR1 expression has not yet been explained during differ entiation uf NHOK and Lransformed oral keraLinocyLes , The purpose of this study were to examine mHNA and protein expression of SPR1 in response to a known differentiation signal, calcium conc in NHOK, lHOK a nd oral SCC ce ll line(HN 4) , and to apply these results for investigating the molecular mecha nisms of tra nsformed cellular differentiation , Primary cultured NHOK, established IHOK and HN 4 cell line were cul tured in KBM bullet kit Preconfluency of NHOK as control group was used Under O, 15mM Ca++ conc(Precon, Postcon) , and 1, 2mM Ca++ conc(Pos tcon)‘ the insoluble final pellets were measured fo1' cornified cell envelope measurements, and RT- PCR for SPRR1 mRNA meas urement, and immunoblotting for SPRR1 protein measurements in tripli cate , resp ectively , The terminal different ia tion of cu ltured NHOK and IHOK was depend on calcium concentration, while HN4 cell line was not SPRR1 mRNA and protein expression of cultured NHOK showed the highest among cultured IHOK & HN 4 cell line in hi gher ca lcium condition , SPRR1 mRNA and protein expression of cultured IHOK showed higher‘ than tha t of HN 4 cell line in hjgher cacium condi tion , SPRH1 was expressed in differentiation of NHOK and IHOK t ransfected by E6/E7 genes but ra rely expressed in malignant oral keratinocytes , It suggested that SPRR1 ex pression as kera tinocyte terminal diff‘erent ia tion marker involved in cellular cornification would be differentially effected by immorta li zation and ca rcinogenic transforma tion