Figure 1.

Effect of poly (ADP‐ribose) polymerase inhibitors (PARPi) in the tumor microenvironment. A, Although PARPi might cause initial tumor shrinkage, they could promote epithelial‐mesenchymal transition (EMT) with minimal cytotoxicity against cancer stem cells (CSCs), leading to CSC enrichment. Poly (ADP‐ribose) polymerase inhibitors might also upregulate checkpoint protein expression, such as programmed cell death ligand‐1 (PD‐L1). B, T cells are inhibited by tumor‐T cell interactions by overexpressed checkpoint proteins, for example, PD‐L1‐programmed cell death‐1 interactions. C, Accelerated epithelial‐mesenchymal transition and enrichment of CSCs with impaired immunogenic cell death leads to cancer progression and metastasis