Post-translational modifications of the Retinoblastoma Protein (pRB) induced by in vitro administration of Zebrafish Embryonic extracts on Human Kidney Adenocarcinoma Cell Line

The in vitro administration of embryonic extracts to tumour cells is known to induce a slowing down of the proliferation rate. In this work, implications of this effect at a molecular level were considered, investigating the role of the Retinoblastoma protein (pRb). A kidney adenocarcinoma cell line, ACHN, was tested with extracts of zebrafish embryos taken during a differentiative stage of development. Whole cell lysates were analysed by immunodecoration with a specific -pRb monoclonal antibody after SDS-PAGE and Western Blotting. Antibody staining showed that cells subjected to 48 hours treatment had a remarkably altered pRb phosphorylation profile, the hypo- and unphosphorylated forms being predominant to hyperphosphorylated pRb. At functional level, unphosphorylated pRb keeps cells in an non-proliferative state by inactivating transcriptional factors of G1-S transition, in agreement with the observed slowing down of the proliferation rate. This is an evidence of direct action of embryonic factors on important regulators of the cell cycle, enforcing our view of a promising chance for a “physiological gene therapy” of cancer.