Our goal was to demonstrate the in vivo
tumor specific accumulation of
crotamine, a natural
peptide from the
venom of the South American rattlesnake Crotalus durissus terrificus, which has been characterized by our group as a
cell penetrating peptide with a high specificity for actively proliferating cells and with a concentration-dependent cytotoxic effect.
Crotamine cytotoxicity has been shown to be dependent on the disruption of lysosomes and subsequent activation of intracellular
proteases. In this work, we show that the cytotoxic effect of
crotamine also involves rapid intracellular
calcium release and loss of mitochondrial membrane potential as observed in real time by confocal microscopy. The intracellular
calcium overload induced by
crotamine was almost completely blocked by
thapsigargin. Microfluorimetry assays confirmed the importance of internal organelles, such as lysosomes and the endoplasmic reticulum, as contributors for the intracellular
calcium increase, as well as the extracellular medium. Finally, we demonstrate here that
crotamine injected intraperitoneally can efficiently target remote subcutaneous
tumors engrafted in nude mice, as demonstrated by a noninvasive optical imaging procedure that permits in vivo real-time monitoring of
crotamine uptake into
tumor tissue. Taken together, our data indicate that the cytotoxic
peptide crotamine can be used potentially for a dual purpose: to target and detect growing
tumor tissues and to selectively trigger
tumor cell death.