Difference of PDT induced apoptotic gene expression in 2D and 3D nasopharyngeal carcinoma cell models

Abstract

Abstract Background Nasopharyngeal Carcinoma (NPC) is one of the top 10 cancers in Hong Kong. Photodynamic Therapy (PDT) is an alternative treatment approach to NPC. We previously reported that PDT induced both apoptosis and necrosis in 2D and 3D NPC models but in different manners, yet the underline biological mechanism is still unknown. In this pilot study we measured 3 apoptotic related gene expression, including c-Myc, p53 and Notch-1 genes using 2D and 3D EBV+ c666-1 cell models at pre- and post- FosPeg (FP) PDT treatment. Methods Total 5 x 105 cells were used for 2D and 3D multicellular layer cell models. Cells were activated with laser at 20J/cm2 after 24 hours FP incubation. Total RNA were obtained using high pure RNA isolation kit (Roche) and were converted to cDNA. 20ng cDNA were used for qPCR (Light Cycler 480). Results Results revealed that 2D and 3D models expressed different mRNA levels of c-Myc, p53 and Notch-1 gene, in both control cells and PDT treated cells. Results indicated that there were 0.3 to 1.2 fold difference in mRNA expression between 2D and 3D cell models among the tested apoptotic genes. 2D model was found more susceptible to PDT inducing mRNA expression than 3D model. The difference could be explained by: 1) light and drug delivery variation; 2) intracellular oxygen difference; and 3) cell to cell communication difference in 2D and 3D cell models. Conclusion 2D and 3D cell models behave differently at both molecular and cellular levels. These differences may due to different PDT responses in 2D and 3D models. 3D cell models were found to be more suitable for PDT pharmacokinetic studies. Further investigation is needed on PDT mediated molecular changes (protein expression) in 3D models. Acknowledgement The work described in this paper was fully supported by a grant from the Research Grants Council of the Hong Kong Special Administrative Region, China (project no.:2015-00-74-RGC150201).