Photochemical disruption of endocytic vesicles before delivery of drugs: a new strategy for cancer therapy

Abstract

The development of methods for specific delivery of drugs is an important issue for many cancer therapy approaches. Most of macromolecular drugs are taken into the cell through endocytosis and, being unable to escape from endocytic vesicles, eventually are degraded there, which hinders their therapeutic usefulness. We have developed a method, called photochemical internalization, based on light-induced photochemical reactions, disrupting endocytic vesicles specifically within illuminated sites e.g. tumours. Here we present a new drug delivery concept based on photochemical internalization-principle -photochemical disruption of endocytic vesicles before delivery of macromolecules, leading to an instant endosomal release instead of detrimental stay of the molecules in endocytic vesicles. Previously we have shown that illumination applied after the treatment with macromolecules substantially improved their biological effect both in vitro and in vivo. Here we demonstrate that exposure to light before delivery of protein toxin gelonin improves gelonin effect in vitro much more than light after. However, in vitro transfection with reporter genes delivered by non-viral and adenoviral vectors is increased more than 10-and six-fold, respectively, by both photochemical internalization strategies. The possible cellular mechanisms involved, and the potential of this new method for practical application of photochemical internalization concept in cancer therapy are discussed.

Transgene expression is increased by photochemically mediated transduction of polycation-complexed adenoviruses

“…Subjecting HeLa cells to light prior to infection with Ad and Ad/PLL mixtures enabled transduction levels superior to those obtained in cells that were light exposed after infection. The mechanism of PCI-treating cells prior to gene transfer assays is not fully understood, but a thorough discussion on this matter can be found in Prasmickaite et al, 25 where the photochemical treatment of THX malignant melanoma cells before or after Ad infection enabled similar amounts of transgene expression. However, the fact that illuminating cells prior to infection seem to be at least as efficient as illuminating cells after infection, and that the increase in transduction was almost equal comparing Ad/PLL samples to uncomplexed samples for the two treatment modes (light before and light after infection), indicate that the photochemical treatment neither damages the CAR receptor nor attenuates the first steps of viral vector uptake (ie binding to CAR and a v -integrins followed by cell entry).…”

“…21 The mechanism and benefit of the technology has earlier been documented for nonviral vectors. [22][23][24][25] In this work, the effect of photoactivation of the photosensitizer TPPS 2a (meso-tetraphenylporphine with two sulfonate groups on adjacent phenyl rings) on adenoviral transduction in the presence of the polycationic agents poly-L-lysine (PLL) and SuperFectt is investigated. Our results show that the combined use of polycations and photochemical treatment greatly enhance transduction, especially in cells expressing moderate to low levels of CAR.…”

Prolonged gene silencing by combining siRNA nanogels and photochemical internalization

“…This results in the emergence of reactive oxygen species (ROS), predominantly singlet oxygen ( 1 O 2 ) that may catalyze the oxidation of amino acids, unsaturated fatty acids and cholesterol. Due to its short diffusion range (~10-20 nm) and its short lifetime (0.01-0.04 µs), singlet oxygen initiates oxidation reactions mainly in the local production area [23][24][25][26]. This oxidative damage eventually breaks down the endosomal barrier, allowing the transition of internalized nanosized matter into the cytoplasm.…”

Photochemically enhanced gene transfection increases the cytotoxicity of the herpes simplex virus thymidine kinase gene combined with ganciclovir

“…When such photosensitizers are activated by light, induced photochemical reactions rupture the membranes of endocytic vesicles so that the vesicular constituents are released into the cytosol of the illuminated cells. 7 In general, endosomedisruptive strategies are of great importance for realizing the full potential of macromolecular drugs. Most macromolecules, including gene/vector complexes, are taken into the cell via endocytosis and often stay trapped in the endocytic vesicles being unable to reach therapeutic targets in other places in the cell.…”