NATIVE CELLULAR FLUORESCENCE IDENTIFIES TERMINAL SQUAMOUS DIFFERENTIATION OF NORMAL ORAL EPITHELIAL-CELLS IN CULTURE - A POTENTIAL CHEMOPREVENTION BIOMARKER

Native cellular fluorescence (NCF) is being investigated as an interme diate endpoint biomarker for chemoprevention, Oral epithelial cells we re cultured under three conditions to identify a spectral pattern for epithelial differentiation: cells maintained in serum-free keratinocyt e growth medium were the least differentiated (KGM cells); cells switc hed to DMEM/F12 plus 10% FCS were intermediate in differentiation (DME M/F12/FCS cells); DMEM/F12/FCS cells switched to serum-free DMEM/F12 p lus 0.8 M NaCl to induce cornified envelopes were the most differentia ted (DMEM/F12/NaCl cells); The differentiation status was characterize d using immunohistochemistry and electron microscopy. NCF analysis was able to distinguish terminally differentiated epithelial cells (DMEM/ F12/NaCl) from those less differentiated cells (KGM, DMEM/F12/FCS) in several emission (lambda(ex) 340 nm, lambda(em) 360-660 nm; lambda(ex) 365 nm, lambda(em) 400-700 nm; lambda(ex) 420 nm, lambda(em) 440-800 nm) and excitation scans (lambda(ex) 200-360 nm; lambda(em) 380 nm, la mbda(ex) 240-430 nm; lambda(em) 450 nm, lambda(ex) 250-460 nm, lambda( em) 480 nm; lambda(ex) 270-500 nm, lambda(em) 520 nm). The ability to discriminate terminal differentiation in this in vitro model supports the concept of using NCF as an intermediate biomarker to monitor in vi vo mucosal differentiation.