Studies On Design,Synthesis And Antitumor Activity Of New Pt(Ⅳ) Prodrugs Based On HDAC Inhibitors

Aberrant epigenetic alterations of tumor suppressor genes have been recognized as a driving force in cancer.Histone deacetylases(HDACs),for example,are promising targets for cancer due to their crucial involvement in epigenetic and cellular signaling.HDACs modulate the expression and functions of DNA repair proteins which remove DNA interstrand crosslinks(ICLs)and control the accessibility of chromatin.Manipulating ICL repair with HDAC inhibition can provide an effective strategy for ICL-inducers,such as platinum-based agents.Herein,we report an asymmetrical Pt(Ⅳ)prodrug Ph B-Pt(Ⅳ)-18 C by combined HDAC inhibition,human serum albumin(HSA)binding,DNA cross-link-triggered apoptosis for synergistic chemotherapy and drug delivery.Ph B-Pt(Ⅳ)-18 C effectively kills cisplatin-resistant human lung cancer cells compared with CDDP and OXP.The presence of an octodecane tail can tune the cellular uptake and the cytotoxicity,and can allow binding with HSA for drug delivery.Additionally,Ph B-Pt(Ⅳ)-18 C can inhibit expression of HDAC,arrest cell cycle,and induce apoptosis.These results demonstrate the combination strategy to be a valuable route for additional preclinical studies.Object: To overcome the drawbacks of clinical platinum-based drugs,such as low cellular uptake and drug resistance,we used histone deacetylase inhibitor phenylbutyric acid(Ph B)and eighteen carbon isocyanate to modify the chemically inert Pt(Ⅳ)prodrug,which produced a class of asymmetric Pt(Ⅳ)prodrugs Ph B-Pt(Ⅳ)-18 C by combined HDAC inhibition,human serum albumin(HSA)binding,DNA cross-link-triggered apoptosis for synergistic chemotherapy and drug delivery.In addition,various cell biology and molecular biology methods were applied to explore the mechanism of Ph B-Pt(Ⅳ)-18 C,which can provide theoretical basis and practical experience for the development of safe and effective Pt-HDACis.Methods: First,histone deacetylase inhibitor phenylbutyric acid Ph B and lipophilic fatty chain group were asymmetrically conjugated with Pt(Ⅳ)prodrugs by multi-steps synthetic procedures.The chemical structures of the synthesized compounds were characterized by NMR and ESI-MS,and the purity of the compounds was determined by HPLC.We also used MTT assay,ICP-MS,Western blot,fluorescence in situ hybridization and immunofluorescence techniques to evaluate the antitumor activity and investigate the mechanism of actions.Results: Cytotoxicity evaluation of the compounds revealed that the synthesized Pt(Ⅳ)-HDACi prodrugs showed higher anticancer activities than clinically-used cisplatin and oxaliplatin in various cancer cell lines and cisplatin-resistant cancer cell lines,which suggests that Ph B-Pt(Ⅳ)-18 C could effectively overcome platinum drug resistance.In addition,the ICP-MS results showed that the presence of an octodecane tail can tune the cellular uptake and the cytotoxicity,and can allow binding with HSA for drug delivery.Additionally,Ph B-Pt(Ⅳ)-18 C can inhibit expression of HDAC,reduce the expression of DNA damage repair protein FANCD2 in the nucleus,and induce cell cycle arrest and apoptosis.Surprisingly,the oxaliplatin-type Ph B-Pt(Ⅳ)-18 C can induce nucleolar stress and ribosome stress,which was mechanistically distinct from cisplatin as well as the cisplatin-type Ph B-Pt(Ⅳ)-18 C compounds.Conclusions: 1)Based on the chemical inertness and prodrug properties of Pt(Ⅳ)compounds,histone deacetylase inhibitor phenylbutyric acid Ph B and lipophilic fatty chain group were asymmetrically conjugated with Pt(Ⅳ)-HDACi prodrugs by multi-steps synthetic procedures.This conjugation strategy can overcome the deficiency of current platinum drugs and significantly enhance the anticancer activity of platinum drugs in cancer cells,which in turn leads to the rapid cell death.2)This conjugation strategy can improve the water partition coefficient and solubility,and further tune the lipophilicity and redox potential of Pt(Ⅳ)-HDACi prodrugs with the aim of altering cellular uptake and the kinetics of reductive activation.3)We also present the development of a series of Pt(Ⅳ)complexes designed to exploit HSA as a vehicle for delivering platinum agents,which significantly enhanced the stability of Pt-HDACi and reduced the rate of reduction of the prodrug by ascorbate in plasma.It also may prevent Pt-HDACis from being released before them reaching the tumor tissue.