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 intermediate endpoint biomarker for chemoprevention. Oral epithelial cells were cultured under three conditions to identify a spectral pattern for epithelial differentiation: cells maintained in serum-free keratinocyte growth medium were the least differentiated (KGM cells); cells switched to DMEM/F12 plus 10% FCS were intermediate in differentiation (DMEM/F12/FCS cells); DMEM/F12/FCS cells switched to serum-free DMEM/F12 plus 0.8 M NaCl to induce cornified envelopes were the most differentiated (DMEM/F12/NaCl cells). The differentiation status was characterized 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, lambda 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 vivo mucosal differentiation.