Delivery Of Paraptosis Inducing 8-hydroxyquinoline Copper Complex For Treatment Of Drug-resistant Tumors

Chemotherapy has proven to be an effective method for cancer treatment by inducing cancer cell apoptosis to inhibit cancer growth.However,cancer cells inherently have and develop many anti-apoptosis mechanisms,thus causing cancer drug resistance and poor prognosis.Overcoming multi-drug resistance is urgently needed in the war against cancer.Hence,we proposed that high curative effect on drug-resistant tumors could be achieved by inducing non-apoptotic cancer cell death to circumvent apoptosis-based resistance.Recent researches revealed that Cu(HQ)2 complex of 8-hydroxyquinoline(HQ)with copper(Ⅱ)could induce quick paraptotic cancer cell death instead of apoptosis,and it is very toxic to many cancer cell lines.However,the solubility of Cu(HQ)2 is poor and can not be used in clinics.Furthermore,many cancer patients exhibit increased intratumoral copper and/or altered systemic copper distribution.As copper serves as a promotor in tumor initiation,angiogenesis,progression,and metastasis.Therefore,we proposed a nanocarrier that can deliver HQ to tumor site so that the HQ can complex with intratumoral copper and in situ form highly toxic Cu(HQ)2 to induce paraptotic cancer cell death,overcoming apoptosis-based resistance,and effectively inhibiting the growth of drug-resistant tumors.In the first part of this thesis,we designed an HQ-based copper-responsive polymer PEG-PHQMA that could self-assemble into stable micelles.Copper(Ⅱ)catalyzed the hydrolysis of the HQ-conjugate linker and subsequently formed Cu(HQ)2,which did not activate caspase but strongly inhibited proteasome activity,significantly elevated intracellular ROS level,caused endoplasmic reticulum and mitochondria swelling,and thus effectively induced paraptosis of drug-resistant tumor cells.In vivo studies showed PEG-PHQMA micelles had long circulation profiles and could effectively accumulate in tumor via the EPR effect.At the very begining,the intratumoral copper level could efficiently catalyze the release of HQ.However,the in-situ copper was quickly consumed and became insufficient to maintain a sustained antitumor effect.By supplementing exogenous copper ions,we could enhance the antitumor effect of PEG-PHQMA micelles and effectively inhibit the growth of drug-resistant MCF-7/ADR tumors.Considering the insufficient in-situ copper in tumor tissue,we further designed a nanocarrier that delivered Cu(HQ)2 complex without injecting extrinsic copper ion.In the second part,we designed a nanogel formed by 5-aminomethyl-8-hydroxyquinoline(QN)containing-PEG block polymer that could further complex with copper(II)to form Cu-nanogel with a diameter of 40 nm.However,the Cu-nanogel could not release the expected copper complex in cancer cells,leading to low cytotoxicity.To this end,we further designed a 2-formyl-8-hydroxyquinoline(FQ)containing block polymer.The polymer could self-assemble into micelles with a diameter of 25 nm that could be further stabilized by incorporating copper(II).The acidic pH in tumor cells efficiently catalyzed the hydrolysis of Schiff’s base bonds in the core of the micelles,quickly realeasing Cu(FQ)2 complex to effectively inhibit the growth of a variety of cancer cell lines.This pH-responsive micelle is a promising nanocarrier that can deliver copper complex to tumor site without injecting exogenous copper ion.