Objective：Transcriptional coactivator p300 has been shown to play a variety of roles in the transcription process and mutation of p300 has been found in certain types of human cancers.However,the expression dynamics of p300 in breast cancer （BC） and its effect on BC patients＇ prognosis are poorly understood.Methods：In the present study,the methods of tissue microarray and immunohistochemistry （IHC） were used to investigate the protein expression of p300 in BCs.Receiver operating characteristic （ROC） curve analysis,Spearman＇s rank correlation,Kaplan-Meier plots and Cox proportional hazards regression model were utilized to analyze the data.Results：Based on the ROC curve analysis,the cutoff value for p300 high expression was defined when the H score for p300 was more than 105.High expression of p300 could be observed in 105/193 （54.4%） of BCs,in 6/25 （24.0%） of non-malignant breast tissues,respectively （P=0.004）.Further correlation analysis showed that high expression of p300 was positively correlated with higher histological grade,advanced clinical stage and tumor recurrence （P0.05）.In univariate survival analysis,a significant association between high expression of p300 and shortened patients＇ survival and poor progression-free survival was found （P0.05）.Importantly,p300 expression was evaluated as an independent prognostic factor in multivariate analysis （P0.05）.Conclusion：Our findings provide a basis for the concept that high expression of p300 in BC may be important in the acquisition of a recurrence phenotype,suggesting that p300 high expression,as examined by IHC,is an independent biomarker for poor prognosis of patients with BC.
