Transport of trans-activator of transcription (TAT) peptide in tumour tissue model: evaluation of factors affecting the transport of TAT evidenced by flow cytometry

Abstract

Abstract Objectives Trans-activator of transcription (TAT), a cell penetrating peptide, has been explored to overcome resistance to penetration and transport inside the cell, therefore, suggested to be used as drug delivery vector into drug-resistant tumours. The generosity of this study was to evaluate modifiable factors (concentration, temperature, incubation time and spheroid age) on the penetration of TAT. Methods Multicellular tumour spheroids (MCTS) used as tumour tissue models to mimic some characteristics with in-vivo tumors. Cell monolayer and 3-, 5-, 7-day-old MCTS were incubated with TAT and effects of modifiable factors were determined quantitatively through flow cytometry, based on TAT-positive cell count (%) and mean fluorescence intensity. Key findings Enhancing TAT concentration (1, 5 and 25 µm), transport significantly increased (ANOVA, P < 0.0001) in cell monolayer and spheroids. However, rising temperature from 7 to 37°C (t, P > 0.05) and increasing incubation time; 20 min, 1 h and 3 h; (ANOVA, P > 0.05) were statistically non-significant. Moreover, TAT penetration declines as spheroids get older (ANOVA, P < 0.01). Conclusion While exploiting MCTS as tumour tissue model, older spheroids could be preferred to target penetration-resistant cells and mimic the in-vivo microenvironment.