The microtubule-destabilizing
protein stathmin is highly expressed in several types of
tumor, thus deserving the name of
oncoprotein 18. High levels of
stathmin expression and/or activity favor the metastatic spreading and mark the most aggressive
tumors, thus representing a realistic marker of poor prognosis.
Stathmin is a downstream target of many signaling pathways, including Ras-MAPK, PI3K and p53, involved in both
tumor onset and progression. We thus hypothesized that
stathmin could also play a role during the early stages of
tumorigenesis, an issue completely unexplored. In order to establish whether
stathmin expression is necessary for
tumor initiation, we challenged wild type (WT),
stathmin heterozygous and
stathmin knock-out (KO) mice with different
carcinogens. Using well-defined mouse models of
carcinogenesis of skin, bladder and muscle by the means of 7,12-dimethylbenz[α]antracene (DMBA)/12-O-tetradecanoylphorbol-13-
acetate (TPA), N-butyl-N-(4-hydroxybutyl)
nitrosamine (BBN) and
3-methylcholanthrylene (3MC) treatments, respectively, we demonstrated that knock-out of
stathmin has no impact on the onset of
cancer in mice. No significant difference was noticed either when the Ras oncogene was mutated (skin
carcinogenesis model) or when the p53 pathway was inactivated (bladder
carcinomas and
fibrosarcomas). Finally, we concomitantly impinged on p53 and Ras pathways, by generating WT and
stathmin KO mouse embryo fibroblasts transformed with
papilloma virus
large T antigen (LgTAg) plus the K-Ras(G12V) oncogene. In vivo growth of xenografts from these transformed fibroblasts did not highlight any significant difference depending on the presence or absence of
stathmin. Overall, our work demonstrates that
stathmin expression is dispensable for
tumor onset, at least in mice, thus making
stathmin a virtually exclusive marker of aggressive disease and a promising therapeutic target for advanced
cancers.