PARP1 and esophageal cancer: Further study is necessary to determine (i) why in esophageal cancer, YM155 initiates PARP-1 hyperactivation-mediated Parthanatos cell death as opposed to caspase-dependent apoptosis; (ii) how poly-ADP in the cytosol induces a death-signaling cascade and executes biological functions in the PARP-1-mediated pathway and; (iii) the identity of proteins targeted by PAR to explore the complex pathway from nuclear to mitochondria during the process of parthanatos.