Patients suffering from the
metabolic disease hereditary tyrosinemia type I (HT1), caused by
fumarylacetoacetate hydrolase deficiency, have a high risk of developing
liver cancer. We report that a sub-apoptogenic dose of
fumarylacetoacetate (FAA), the mutagenic metabolite accumulating in HT1, induces spindle disturbances and segregational defects in both rodent and human cells. Mitotic abnormalities, such as distorted spindles, lagging chromosomes, anaphase/telophase
chromatin bridges, aberrant karyokinesis/cytokinesis and multinucleation were observed. Some mitotic asters displayed a large pericentriolar material cloud and/or altered distribution of the spindle pole-associated
protein NuMA. FAA-treated cells developed micronuclei which were predominantly CREST-positive, suggesting
chromosomal instability. The Golgi complex was rapidly disrupted by FAA, without evident microtubules/
tubulin alterations, and a sustained activation of the extracellular signal-regulated
protein kinase (ERK) was also observed. Primary skin fibroblasts derived from HT1 patients, not exogenously treated with FAA, showed similar mitotic-derived alterations and ERK activation. Biochemical data suggest that FAA causes ERK activation through a
thiol-regulated and
tyrosine kinase-dependent, but
growth factor receptor- and
protein kinase C-independent pathway. Pre-treatment with the
MEK inhibitor
PD98059 and the Ras farnesylation inhibitor
B581 decreased the formation of CREST-positive micronuclei by approximately 75%, confirming the partial contribution of the Ras/ERK effector pathway to the induction of
chromosomal instability by FAA. Replenishment of intracellular
glutathione (GSH) with GSH monoethylester abolished ERK activation and reduced the
chromosomal instability induced by FAA by 80%. Together these results confirm and extend the previously reported genetic instability occurring in cells from HT1 patients and allow us to speculate that this tumorigenic-related phenomenon may rely on the biochemical/cellular effects of FAA as a
thiol-reacting and organelle/mitotic spindle-disturbing agent.