Mouse oocyte maturation and embryo development after exposure to Vemurafenib (plx4032), an anti-melanoma B-RafV600E inhibitor

Vemurafenib is a selective B-RafV600E inhibitor in melanoma targeted therapy which also inhibits the wild type B- and C-Raf. In oocyte maturation, the C-Raf/MAPK pathway acts as an important self-enhancing and promoting system, whereas in embryo development, the C-Raf/MAPK pathway participates in pre- and post- implantation embryo proliferation and differentiation.;The hypothesis: Vemurafenib has detrimental effects on oocyte maturation and/or embryo development. Mouse oocytes and one cell (1C) mouse embryos were tested by ex vivo culturing with Vemurafenib in serial dilution. Oocytes were evaluated by cell cycle morphology, spindle formation and chromosomal alignment by immunofluorescence (IF) staining as well as DNA integrity by Terminal Transferase dUTP Nick End Labeling. Embryo development was evaluated by morphological changes and the C-Raf bioactivity via a p-Mek 1/2 IF assay. In vivo exposure and subsequent morphological evaluation of ex vivo two-cell (2C) embryo development was conducted by pre-injections of Vemurafenib (10 mg/kg).;Ten microM or above produced oocyte toxicity, spindle formation disturbance, chromosome misalignment and DNA damage, whereas the therapeutic Vemurafenib concentration 1 microM did not display significant oocyte morphological toxicity to ex vivo oocyte maturation, spindle formation, chromosome alignment and DNA integrity.;Ten .tM and 100 .tM showed phosphorylation inhibition of embryo Mek 1/2, decreased C-Raf activity and obvious toxicity to 1C to 2C transition. However, the 1 microM Vemurafenib was not shown to have significant ex vivo preimplantation 1C embryo development toxicity on the 1C to 2C transition and no effect on C-Raf activity.;Ten mg/kg Vemurafenib pre-injections demonstrated only a mild delayed toxic influence throughout the embryo development. However, the majority of embryos progressed to normal blastocysts and did not show significant in vivo degenerative preimplantation embryotoxicity.;Thus Vemurafenib, at its therapeutic concentration, was free of ex vivo oocyte and embryo morphological toxicity, but in vivo toxicity needs further clarification on mechanisms and survivability of collapsed unhatched embryos.