Synthesis,Transmembrane Anion Transport And Antitumor Activity Of Bisbenzimidazolyl-based Anionophores

The balance of normal anion concentrations in cells provides basis for maintaining normal cellular morphology and function.Small-molecule organic compounds with transmembrane anion transport activity,namely anion transporters have high potentials as a new class of anti-tumor drugs.This is because such compounds are able to trigger the apoptosis of tumor cells by disturbing the balance of normal intracellular and extracellular concentrations of anions,in particular chloride anions.Though some anion transporters exhibit good anti-tumor activity,the correlation between the anti-tumor activity and anion transport remains to be established.In addition,systematic study on the probable anti-tumor mechanism of anion transporters 1s at a relatively early stage.To address these issues and drive forward the potential application of anion transporters in the discovery of new drugs for cancers,in this dissertation a series of bisbenzimidazolyl-based anion transporters were designed and synthesized,and their liposomal and in vitro anion transport,anti-proliferative activity and the probable mechanism of biological action were systematically studied.As such,this dissertation consists of three chapters.In Chapter 1,the latest advances in the in vitro anion transport and anti-txmor activity of anion transporters during the past ten years were reviewed.The strategies that have been used to optimize the anion transport activity were also summarized.The design principle and the significance of this research were briefly described.In Chapter 2,the in vitro anion transport,anti-tumor activity and probable anti-tumor mechanism of biological action of 1,3-bis(benzimidazol-2-yl)benzene and its derivatives were systematically studied,with the aim to elucidate the correlation between the anion transport activity and anti-tumor activity.Firstly,the inhibitory activity of these compounds toward cancer cells was tested by means of MTT-based assays.The results showed that l,3-bis(benzimidazol-2-yl)benzene and most of its derivatives showed effective anti-proliferation activity.MQAE and acridine oragne(AO)staining experiments based on HeLa cells indicate that these compounds are able to facilitae the influx of chloride anions into live cells and alkalize acidic organelles.More interestingly,their in vitro chloride transport activity parallels their anion transport efficiency in liposomal models.In addition,extracellular chloride anions play a crucial role in the cytotoxic effects of these compounds.The nuclear chromatin pyknosis and the decrease of mitochondrial membrane potential suggest that the anti-tumor mechanism of these compounds may be apoptosis.In Chapter 3,to optimize the anion transport and anti-tumor activity of bisbenzimidazolyl-based anion transporters,two series of fluorinated 1,3-bis(benzimidazol-2-yl)benzene derivatives were designed and synthesized.As a consequence,the introduction of fluorine atoms into the central phenyl ring could not only improve the chloride anion transport activity,but also significantly enhances the anti-tumor proliferation activity.The total number of fluornne atoms on the benzimidazolyl subunits can significantly improve the chloride anion transport activity,but has little effect on the anti-tumor activity.Although the location of fluorine atoms on the benzimidazolyl subunits has limited effect on the chloride anion transport activity,it has obvious impact on the cytotoxicity.In addition,MQAE and acridine oragne(AO)staining experiments based on HeLa cells suggest that l,3-bis[(4,5,6,7-tetrafluoro-benzimidazol)-2-yl]-5-fluorobenzene could not only disturb the balance of intracellular and extracellular chloride anions,but also alkalize lysosomes.The nuclear chromatin pyknosis and the decrease of mitochondrial membrane potential suggest that this compound exerts its anti-tumor activity through an apoptotic pathway.In summary,the above-mentioned results indicate that the synthsized bisbenzimidazolyl-based anion transporters exert promising antitumor activity most probably through apoptotic pathway by disturbing the balance of anions in cells,and the anion transport and antitumor activity may be optimized by means of fluorination.The present findings may provide useful guidance for the rational design of novel small-molecule anti-tumor drugs that function by disrupting the anionic homeostasis in cells.