METHODOLOGY/PRINCIPAL FINDING: We examined NPC2
protein expression in surgical samples of papillary tissues by immunohistochemical
stain, and all papillary tissues expressed NPC2
protein in the epithelium. To examine our hypothesis of NPC2
protein-mediated papillae formation, we carried out xenograft experiments using wild H460 cells (large cell lung
carcinoma cell line) that constitutively expressed abundant NPC2
protein and NPC2
protein-depleted H460 cells by NPC2
shRNA. The xenografts of wild H460 cells and empty
shRNA vector cells showed distinct papillae formation, whereas NPC2
protein-depleted H460 cells displayed markedly reduced or no papillae. Since all papillary tissues have open spaces we examined whether NPC2
protein might also contribute to the creation of open spaces. The TUNEL assay in the xenografts of wild and empty
shRNA vector H460 cells showed massive cell death, and NPC2
protein-depleted cells displayed minimal cell death. Measurement of
caspase 3/7 activities in cultured H460 cells supported NPC2
protein-mediated apoptotic cell death. The presence of excess NPC2
protein, however, did not always produce papillae as seen in the xenografts of CHO cells that were stably transfected with NPC2.
CONCLUSIONS/SIGNIFICANCE: