Effects Of PARP-1 Inhibitor PJ34 On The Proliferation And Cisplatin-resistance In Human Lung Adenocarcinoma A549/DDP Cells

Objective Lung cancer is the top threaten to residents’ health and life, non-small cell lung carcinoma(NSCLC) accounting for the vast majority of its histological type(about 75%-80%), and the majority of patients are diagnosed at an advanced stage(approximately 80%), chemotherapy has become the main treatment. Cisplatin(DDP) is the base of the standard first-line chemotherapy of NSCLC, and is the most commonly used anti-cancer drug in clinical currently. It is best known for its capacity to form intra- and interstrand DNA adducts,leading to the activatin of DNA damage. However,therapy induced resistance to cisplatin therapies has emerged as a major obstacle in the treatment of NSCLC. The mechanism of DDP-resistance has not been firmly established.Poly(ADP-ribose) polymerases(PARPs) are a family of enzymes. PARP-1 is the most abundant and best-characterized members of the family.Because of its key role in DNA damage repair,it has become the most promising approach to cancers in recent years. When PARP-1 is inhibited, DNA single strand breaks(SSBs) degenerate and accumulate, then transformed into a persistent DNA double strand break(DSBs), ultimately leading to cell death.PJ34 is a new competitive inhibitor of PARP-1, and hasshown significant anti-tumor effect in a variety of tumors. This study aim to investigate the effect of PARP-1 inhibitor PJ34 on the growth activity and DDP-resistance in the human lung adenocarcinoma A549/DDP cells.Methods 1.Cultured the human lung adenocarcinoma cells A549 and DDP-resistant cells A549/DDP in vitro. MTT method was used to determine the effects of DDP alone/combine with PJ34 on the proliferation and DDP-resistance of A549/DDP cells. 2.Flow cytometry was used to determine the effects of DDP alone/combine with PJ34 on the apoptosis ratios of A549/DDP cells.3. Western Blot was used to measure the expression levels of PARP-1 protein and MDR associated protein(LRP、GST-π) in DDP-sensitive cells A549 and DDP-resistant cells A549/DDP, and determine the effects of DDP alone/combine with PJ34 on the protein expression of A549/DDP cells.Results1.A549/DDP cell lines’ are more resistant to DDP than A549 cell lines, resistant fold is 10.5.2.PARP-1 inhibitor PJ34 could significantly inhibit the proliferation of A549/DDP cells alone. The non-toxic dose of PJ34(3 mg?L-1)could obviously resensitize A549/DDP cells to cisplatin, partly reverse DDP-resistance, decrease the IC50 of DDP from 26.14±0.62 mg?L-1 to 11.46 ± 0.92 mg?L-1.The reversal fold is 2.28.3. Flow cytometry revealed that: the non-toxic dose of PJ34(3 mg?L-1)combine with DDP(12 mg?L-1) could induce apoptotic significantly. Compared with DDP group, the apoptotic ratio is obviously increased at 33.2%.4. Western Blot analysis revealed that: compared with A549 cells, the expression of PARP-1 and resistance-associated protein LRP and GST-π in A549/DDP cells are obviously increased. Compared with DDP group and PJ34 group, PJ34 combine with DDP could remarkably lower the expression levels of PARP-1 and LRP 、GST-π.Conclusion1. PARP-1 inhibitor PJ34 could remarkably inhibit the proliferation of A549/DDP cells with a concentration-dependent manners.2. The non-toxic dose of PJ34(3 mg?L-1)could obviously resensitize A549/DDP cells to cisplatin, induce apoptotic,partly reverse DDP-resistance.3. The mechanism of the reversal of DDP-resistance by PJ34 was probably relating to the lowered expression of PARP-1 and resistance-associated protein LRP and GST-π.