PARP1 and neoplasm: Aside from less PS accumulation or reduction on ROS generation, the tumor molecular adaptation regarding signaling pathways (e.g. MAPK/JNK/p38α, AMPK, and AKT/mTOR) have also provided PDT-resistance with crosstalk between apoptotic machinery (e.g. BCL-2, BCL-xL, survivin, caspases, and PARP1) and autophagy, as summarized in Figure 2 (60, 74, 76, 100–103).