Fumarylacetoacetate, the metabolite accumulating in hereditary tyrosinemia, activates the ERK pathway and induces mitotic abnormalities and genomic instability

Patients suffering from the metabolic disease hereditary tyrosinemia type I (HT1), caused by fumarylacetoacetate hydrolase deficiency, have a high ris k of developing liver cancer. We report that a sub-apoptogenic dose of fuma rylacetoacetate (FAA), the mutagenic metabolite accumulating in HT1, induce s spindle disturbances and segregational defects in both rodent and human c ells. Mitotic abnormalities, such as distorted spindles, lagging chromosome s, anaphase/telophase chromatin bridges, aberrant karyokinesis/cytokinesis and multinucleation were observed. Some mitotic asters displayed a large pe ricentriolar material cloud and/or altered distribution of the spindle pole -associated protein NuMA. FAA-treated cells developed micronuclei which wer e predominantly CREST-positive, suggesting chromosomal instability. The Gol gi complex was rapidly disrupted by FAA, without evident microtubules/ tubu lin alterations, and a sustained activation of the extracellular signal-reg ulated protein kinase (ERK) was also observed. Primary skin fibroblasts der ived from HT1 patients, not exogenously treated with FAA, showed similar mi totic-derived alterations and ERK activation. Biochemical data suggest that FAA causes ERK activation through a thiol-regulated and tyrosine kinase-de pendent, but growth factor receptor- and protein kinase C-independent pathw ay. Pre-treatment with the MEK inhibitor PD98059 and the Ras farnesylation inhibitor B581 decreased the formation of CREST-positive micronuclei by sim ilar to 75%, confirming the partial contribution of the Ras/ERK effector pa thway to the induction of chromosomal instability by FAA. Replenishment of intracellular glutathione (GSH) with GSH monoethylester abolished ERK activ ation and reduced the chromosomal instability induced by FAA by 80%. Togeth er these results confirm and extend the previously reported genetic instabi lity occurring in cells from HT1 patients and allow us to speculate that th is fumorigenic-related phenomenon may rely on the biochemical/cellular effe cts of FAA as a thiol-reacting and organelle/mitotic spindle-disturbing age nt.