Correlation between PARP-1 immunoreactivity and cytomorphological features of parthanatos, a specific cellular death in breast cancer cells

In parthanatos, a PARP-1 (poly (ADP-ribose) polymerase 1)-mediated cell death, dissipation of mitochondrial membrane potential, large-scale DNA fragmentation and chromatin condensation were observed. In contrast to apoptosis, it does not cause apoptotic bodies formation. Although PARP-1-mediated cell death presents loss of membrane integrity similar to necrosis, it does not induce cell swelling. The purpose of the study was to correlate the immunohistochemical parameters of PARP-1 reactivity and the selected cytomorphological features of parthanatos: the lack of apoptotic bodies and the absence of necrosis in breast cancer (BC) specimens. Immunohistochemistry for PARP-1 was performed on 83 BC specimens. Correlations between parameters of PARP-1 expression and sub-cellular localisation and the presence of apoptotic bodies and necrosis were evaluated. High expression of PARP-1 (ImmunoReactive Score ≥6) was associated with the lack of apoptotic bodies (P=0.013) and with the absence of necrosis (P=0.002). The presence of apoptotic bodies was correlated with re-distribution of PARP-1 from the nucleus to cytoplasm in BC cells (P=0.029). Additionally, a tendency was observed between necrosis and loss of nuclear PARP-1 expression (P=0.049). Our study suggests that PARP-1 may play a crucial role in induction and regulation of specific type of cellular death called parthanatos.