['To evaluate the inhibitory effect of deuterium-depleted water (DDW) on the proliferation of nasopharyngeal carcinoma (NPC) cells in vitro and explore the possible mechanism.', 'The growth inhibition of NPC cells and preosteoblast MC3T3-E1 cells following DDW treatment was measured by MTT assay and plate colony formation assay. The changes in migration and invasion of NPC cells were evaluated using Transwell and boyden chamber assays. The protein expression of proliferating cell nuclear antigen (PCNA) was determined using Western blotting. Flow cytometry was employed to evaluate the changes in cell cycle distribution after DDW treatment.', 'DDW with deuterium concentrations of 100, 75 and 50 ppm significantly suppressed the cell proliferation  (P<0.05) and lowered colony formation capacity and invasiveness of the NPC cells (P<0.01). Western blotting demonstrated a down-regulated expression of PCNA in the cells by DDW. DDW also caused obvious cell cycle arrest in the NPC cells with reduced cells in S phase and significantly increased cells in G(1) phase (P<0.05). Rather than causing growth inhibition, DDW promoted the growth of normal control MC3T3-E1 cells.'] Does [ Deuterium-depleted water selectively inhibit nasopharyngeal carcinoma cell proliferation in vitro ]?