Tumor Hypoxic Microenvironment Interference-mediated Synergistic Cancer Therapy

Hypoxia is a common feature of solid tumors and one of the hallmarks of tumor microenvironment（TME）.Various studies have indicated that hypoxia can facilitate the proliferation of tumor cells and significantly promote the malignant transformation and metastasis of tumors,while decreasing the sensitivity of malignant tumors to multiple therapeutic modalities,especially oxygen-dependent cancer therapeutic strategies,like radiotherapy（RT）,chemotherapy,nanodynamic therapy（NDT）,immune therapy,and so on.Therefore,it is particularly important to explore and develop safety and highly efficient tumor oxygenation strategies to enhance oxygen-dependent cancer therapeutic effects.In this work,photosynthetic cyanobacteria（Cyan）and catalase（CAT）with high hydrogen peroxide（H₂O₂）catalytic efficiency can be served as oxygen supplier,respectively,and three micro-nanotherapeutic systems with good biosafety to alleviate hypoxic TME have been constructed via inducing in-suit oxygen generation to augment the effect of hypoxic tumor therapy.This thesis not only provides a tool for tumor in situ oxygen generation to improve tumor oxygenation,but presents a new strategy to tumor hypoxic microenvironment interference-mediated cancer synergistic therapy.The major work on this paper is outlined below:1.Combination photosynthetic cyanobacteria with MnO_xnanospikes for augmented tumor nanodynamic therapy.Nanodynamic therapy（NDT）based on reactive oxygen species（ROS）generation including singlet oxygen（¹O₂）,hydroxyl radical（·OH）et.al has been envisioned as a distinct modality for efficient cancer treatment.However,insufficient ROS generation and partial ROS consumption frequently limit the therapeutic effect and outcome of NDT owing to the low oxygen（O₂）level and high glutathione（GSH）level in TME.In this work,the capability of alleviating tumor hypoxia was evaluated via laser-irradiated photosynthesis of cyanobacteria（Cyan）,which could induce amount of oxygen generation in vitro and in vivo.In addition,the biosafety of Cyan was systematically evaluated via in vitro and vivo experiments.Based on this,a high-efficient and biodegradable synergistic therapeutic system was proposed via combination GSH-depletion Mn（Ⅲ）-riched manganese oxide nanospikes（MnO_x NSs）with the photosynthetic Cyan to reshape TME by simultaneously increasing oxygen content and decreasing GSH level.Specifically,Mn（Ⅲ）-riched MnO_x NSs were prepared via a facile directly reducing potassium permanganate（KMnO₄）approach.Under the trigger of acidic TME,MnO_x NSs reacted with photosynthetic oxygen could generate toxic singlet oxygen（¹O₂）.Additionally,MnO_x NSs also significantly reduced intracellular GSH and further amplificated oxidative stress,inducing apoptosis of tumor cells.Consequently,this combined strategy based on coadministration with Cyan and MnO_x NSs demonstrated the superior antitumor efficacy in 4T1 tumor-bearing mice for synergetic oxygen-augmented nanodynamic therapy.The related research results have been published in Biomaterials（2022,287,121688）.2.Engineered cyanobacteria sonosensitizer for augmented sonodynamic therapy of hypoxic tumors.In this work,an oxygen self-sufficient hybrid sonosensitizer on the basis of photosynthetic microorganisms Cyan integrated with ultrasmall oxygen-deficient bimetallic oxide Mn_1.4WO_x nanosonosensitizers,termed as M@C,is designed and engineered to overcome the critical issue of hypoxia-induced tumor resistance and improve the SDT effect.Firstly,Cyan in M@C could continuously and controllably produce amount oxygen and further relieve tumor hypoxia via laser-mediated photosynthesis.Secondly,under ultrasound（US）stimulation,the sustained photosynthetic-O₂ was activated to generate ¹O₂ via Mn_1.4WO_x sonosensitizer loaded on M@C surface.The results showed that this cascade process could produce more ROS in vitro and in vivo to suppress cancer cells,improve and enhance the efficacy of sonodynamic therapy,and thus effectively inhibit hypoxic tumors growth,proving the proof of concept of microbial nanomedicine for photosynthetic-assisted sonodynamic therapy.The related research results have been published in Advanced Healthcare Materials（2022,11,e2102135）.3.Tumor oxygenation nanoliposome synergistic hypoxia-inducible-factor-1 inhibitor enhanced Iodine-125 seed brachytherapy for esophageal cancer.In the process of ¹²⁵I seed irradiation,similar radioresistance phenomenon will also appear as that of external radiotherapy,in which tumor hypoxia and HIF-1 signaling pathway activation are the main causes of radioresistance.In this work,an innovative strategy was proposed to alleviate radioresistance of brachytherapy by co-encapsulating catalase（CAT）and HIF-1 inhibitor-acriflavine（ACF）into the hydrophilic cavities of liposome,termed as“ACF-CAT@Lipo”.On the one hand,under overexpressed H₂O₂ stimulation in the tumor region,the fabricated ACF-CAT@Lipo can generate an amount of O₂ and alleviate tumor hypoxia in vitro and in vivo.On the other hands,cooperating with the release of ACF,the expression of hypoxia-related protein（e.g.HIF-1α,VEGF,MMP-2）are obviously decreased.Consequently,the copious oxygenation and the significant inhibition expression of HIF-1αcan further improve the radiosensitivity of ¹²⁵I brachytherapy and finally kill tumor cells and inhibit the growth of hypoxic tumor in vivo.The related research results have been published in Biomaterials（2022,289,121801）.