SELECTIVE INHIBITION OF KRAS SIGNALING BY COMBINATION OF LOW DOSE RAPAMYCIN AND PACLITAXEL IN VIVO

Background. Therapy with compounds potentially capable to block KRAS oncogene signaling pathway is perspective direction in modern oncopharmacology. The aim of current study was to investigate effects of the combined treatment with rapamycin (RAP) and paclitaxel (PAC) in transgenic zebrafish (Danio rerio) with constant expression of mutant KRASV12 oncogene conjugated to green fluorescent protein (GFP) in epidermal cells. This strain has a modified phenotype due to epidermal hyperplasia and expression of GFP reporter at skin of embryos and adult fish.

Materials and methods. Fish embryos 6 hpf were exposed to 0.1 % DMSO solution (control) and various doses of the drugs or combinations thereof. GFP expression in epidermal cells was morphometrically measured at 72 hpf.

Results. Dose-related decrease in phenotypic changes up to complete epidermal normalization under RAP 50–400 nM treatment was observed. Treatment with nontoxic for embryos doses of PAC 50–250 nM increased fluorescence level in a dose-dependent manner, indicating an activation of KRAS signaling. Using of lower doses of RAP (10 and 25 nM) or PAC (10 nM) had no statistically significant effect on expression of transformed phenotype. Whereas combined treatment (RAP 10–25 nM and PAC 10–50 nM) dramatically decreased level of epidermal fluorescence and completely normalized phenotype of transgenic fish.

Conclusions. Thus, mutual potentiating effect of RAP and PAC in low doses which leads to selective inhibition of the KRAS signaling pathway was revealed, indicating the prospect of further studies of these drugs combination for targeted cancer therapy.

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