EXPLORING HIV-1 TAT PENETRABILITY IN TUMOR SPHEROIDS THROUGH CONFOCAL MICROSCOPY: A CELL LINES BASED STUDY

Deficient vascular supply, intracellular matrix and hypoxia in solid tumor offer  hindrance to penetration of drugs into desired site of action. HIV-1 TAT (Human Immunodiffiency Virus type-1 Transactivation of Transcription) peptide reported to penetrate in all stages of cell cycle, and therefore, could be exploited as potential drug carrier to overcome the penetratibility hindrance into resistant tumor tissues. Multicellular tumor spheroids (MCTS) is an in-vitro tumor model to measure the penetration of TAT to mimic with in-vivo tumors. The current study involves  investigation of the penetration rate, penetration depth, peptide accummulation, and extent of TAT penetration in MCTS at 4°C and 37°C for an incubation time of  1.5 hours. Observations were taken at 10 minutes  interval, from spheroid surface to the deeper layers through 3µm continous laser sectioning. TAT-labelled fluorescence accumulated approximately at the same rate at each observed depth of MCTS. Moreover, higher accummulation in three-day old spheroids was observed, that could be due to loose packed cells, more ratio of extracellular volume, and more number of live proliferating cells as compared to five-day old spheroids. Detection of penetration and fluorescence accummulation decreased as spheroids get older, that dependent on multifunctional characteristic along age/duration of cell culture.