ABCC2 (MRP2, cMOAT) Localized in the Nuclear Envelope of Breast Carcinoma Cells Correlates with Poor Clinical Outcome

Nuclear expression of ABCC2 can be specific for lower differentiated cells and stem cells. The study aimed at examination of ABCC2 expression in breast cancers. The immunohistochemical analyses were performed on 70 samples of breast cancer. We have also studied prognostic value of the ABCC2 mRNA expression using the KM plotter which assessed the effect of 22,277 genes on survival in 1809 breast cancer patients. Immunohistochemical studies demonstrated that ABCC2 expression may be manifested in nuclear envelope of neoplastic cells (ABCC2n) as well as in their cell membrane and cytoplasm (ABCC2c). The univariate and multivariate analyses showed that higher expression of ABCC2n and ABCC2c was typical for cases of a shorter overall survival time. Higher ABBC2n expression was also typical for cases of a shorter disease-free survival and a shorter progression-free time. The KM plotter analysis of the prognostic value of ABCC2 mRNA expression showed that elevated ABCC2 expression was specific for cases of a shorter relapse-free survival only in the estrogen receptor-negative subgroup. The study demonstrated hat breast cancers manifest ABCC2 expression and that it is linked to a less favourable prognosis. Our results suggested that immunohistochemical tests represent a reliable way to detect prognostic value of ABCC2 expression, allowing to demonstrate differences related to subcellular localization of the protein. Cases with nuclear expression of ABCC2 manifested a more aggressive clinical course, which might reflect a less advanced differentiation of neplastic cells, resistance to the applied cytostatic drugs and tamoxifen.