BackgroundPTTG1-interacting protein (PTTG1IP) is an oncogenic protein, which participates in metaphase-anaphase transition of the cell cycle through activation of securin (PTTG1). PTTG1IP promotes the shift of securin from the cell cytoplasm to the nucleus, allowing the interaction between separase and securin. PTTG1IP overexpression has been previously observed in malignant disease, e.g. in breast carcinoma. However, the prognostic value of PTTG1IP in breast carcinoma patients has not previously been revealed.MethodsA total of 497 breast carcinoma patients with up to 22-year follow-up were analysed for PTTG1IP and securin immunoexpression. The results were evaluated for correlations with the clinical prognosticators and patient survival.ResultsIn our material, negative PTTG1IP immunoexpression predicted a 1.5-fold risk of breast cancer death (p = 0.02). However, adding securin immunoexpression to the analysis indicated an even stronger and independent prognostic power in the patient material (HR = 2.5, p < 0.0001). The subcellular location of securin was found with potential prognostic value also among the triple-negative breast carcinomas (n = 96, p = 0.052).ConclusionsPTTG1IP-negativity alone and in combination with high securin immunoexpression indicates a high risk of breast cancer death, resulting in up to 14-year survival difference in our material.

Background:Cancer cell proliferation is a critical feature in classifying and predicting the outcome of breast carcinoma. Separase has a central role in cell cycle progression in unleashing sister-chromatids at anaphase onset. Abnormally functioning separase is known to lead to chromosomal instability.Methods:The study comprises 349 breast carcinoma patients treated in Central Hospital of Central Finland. The prognostic value, role as a proliferation marker and regulatory interactions of separase are evaluated by immunohistochemical and double- and triple-immunofluorescence (IF) detections based on complete clinical data and >22-year follow-up of the patient material.Results:In our material, abnormal separase expression predicted doubled risk of breast cancer death (P<0.001). Up to 11.3-year survival difference was observed when comparing patients with and without separase expressing cancer cell mitoses. Particularly, abnormal separase expression predicted impaired survival for luminal breast carcinoma (P<0.001, respectively). In multivariate analyses, abnormal separase expression showed independent prognostic value. The complex inhibitory interactions involving securin and cyclin B1 were investigated in double- and triple-IFs and revealed patient subgroups with aberrant regulation and expression patterns of separase.Conclusions:In our experience, separase is a promising and clinically applicable proliferation marker. Separase expression shows strong and independent prognostic value and could be developed into a biomarker for treatment decisions in breast carcinoma, particularly defining prognostic subgroups among luminal carcinomas.

Our data indicate that securin expression may serve as a strong and independent prognosticator of breast cancer outcome and that a cytoplasmic localization of the protein may provide additional prognostic information, particularly in the biologically and clinically challenging subgroup of triple-negative breast carcinomas. The sub-cellular localization of securin appears to reflect the expression of PTTG1IP, CDC20 and BUBR1, which may participate in the regulation of securin activity and, ultimately, in the survival of breast cancer patients.