Conclusions
The significant association between elevated PLK1 and TP53 mutation in women with breast cancer is consistent with escape from repression of PLK1 expression by mutant p53. Tumours expressing elevated PLK1, but lacking functional p53, may be potential targets for novel anti-PLK1-targeted drugs.
Methods
Immunohistochemistry was performed using antibodies to PLK1, MDM2 and Ki67 on Tissue Micro-Array (TMA) slides of a cohort of 215 primary breast cancers. The TP53 gene (encoding p53) was sequenced in all tumour samples. Protein expression scored using the "Quickscore" method was compared with clinical and pathological data, including survival.
Results
Staining of PLK1 was observed in 11% of primary breast tumours and was significantly associated with the presence of TP53 mutation (P = 0.0063). Moreover, patients with both PLK1 expression and TP53 mutation showed a significantly worse survival than those with either PLK1 expression or TP53 mutation alone. There was also a close association of elevated PLK1 with triple negative tumours, considered to be poor prognosis breast cancers that generally harbour TP53 mutation. Further association was observed between elevated PLK1 levels and the major p53 negative regulator, MDM2. Conclusions: The significant association between elevated PLK1 and TP53 mutation in women with breast cancer is consistent with escape from repression of PLK1 expression by mutant p53. Tumours expressing elevated PLK1, but lacking functional p53, may be potential targets for novel anti-PLK1-targeted drugs.