Overexpression of stathmin in breast carcinomas points out to highly proliferative tumours

We recently discovered that stathmin was overexpressed in a subgroup of hum an breast carcinomas. Stathmin is a cytosolic phosphoprotein proposed to ac t as a relay integrating diverse cell signalling pathways, notably during t he control of cell growth and differentiation. it may also be considered as one of the key regulators of cell division for its ability to destabilize microtubules in a phosphorylation-dependent manner. To assess the significa nce of stathmin overexpression in breast cancer, we evaluated the correlati on of stathmin expression, quantified by reverse transcription polymerase c hain reaction. with several disease parameters in a large series of human p rimary breast cancer (n = 133), obtained in strictly followed up women, who se clinico-pathological data were fully available. In agreement with our pr eliminary survey, stathmin was found overexpressed in a subgroup of tumours (22%). in addition, overexpression was correlated to the loss of steroid r eceptors (oestrogen, P = 0.0006; progesterone, P = 0.008), and to the Scarf f-Bloom-Richardson histopathological grade III (P = 0.002), this latter bei ng ascribable to the mitotic index component (P = 0.02). Furthermore studie s at the DNA level indicated that stathmin is overexpressed irrespective of its genomic status. Our findings raise important questions concerning the causes and consequences of stathmin overexpression, and the reasons of its inability to counteract cell proliferation in the overexpression group. (C) 2000 Cancer Research Campaign.