P22-7 Evaluate the effect of nasopharyngeal carcinoma 3D spheroid cell density on Hexyl-ALA induced PpIX accumulation

Abstract

3D spheroid culture model provides a more physiologically relevant model compared with 2D cell model. The utilization of 3D spheroid culture model become increasing important for anti-tumor drug efficacy evaluation as its architecture provided more accurate evaluation on anti-tumor drug accumulation. Although there are several methods available for developing the 3D cell spheroids, there is lacking information on how the spheroid cell size affects the photosensitizers (PS) accumulation, particularly on NPC 3D spheroids. Therefore, in this study, NPC/C666-1 cells with different initial cell density were used to develop 3D spheroids for Hexyl-ALA induced PpIX uptake evaluation. 3D spheroids were generated using agarose base hydrogel method with initial cell density ranged from 5000 to 60000 cells. 3D cell size and morphology were measured from day 0 to day 5. Cell spheroids obtained on day 3 with initial cell density 10000, 30000 and 60000 were used for the subsequent PS uptake study using flow cytometry. Cells started to cluster and loosely aggregated to form spheroids at day 2. However, the spheroids were more compact, rigid and spherically shaped with higher initial cell density used. The 3D spheroids generated with 10000, 30000 and 60000 cells uptake Hexyl-ALA at 0 to 16 hours with an increased in intracellular PpIX accumulation. Interestingly, the accumulation pattern of PpIX induced by Hexyl-ALA was cell mass independent, with optimum PpIX accumulation obtained in 30000 cells. PpIX accumulation was found higher in 30000 cells compared with 10000 cells but with no difference with 60000 cells. This is the first report on the effect of 3D spheroid cell sizes on Hexyl-ALA PDT uptake efficacy evaluation. Further investigation is needed on the phototoxic effect and bio-mechanisms of Hexyl-ALA mediated PDT in NPC 3D spheroids.