Addressing Barriers to Effective Cancer Immunotherapy with Nanotechnology: Achievements, Challenges, and Roadmap to the Next Generation of Nanoimmunotherapeutics
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Advanced Drug Delivery Reviews 141 (2019) 3–22 Contents lists available at ScienceDirect Advanced Drug Delivery Reviews journal homepage: www.elsevier.com/locate/addr Addressing barriers to effective cancer immunotherapy with nanotechnology: achievements, challenges, and roadmap to the next generation of nanoimmunotherapeutics Enping Hong, Marina A. Dobrovolskaia ⁎ Nanotechnology Characterization Laboratory, Cancer Research Technology Program, Leidos Biomedical Research, Inc., Frederick National Laboratory for Cancer Research, Frederick, MD 21702 article info abstract Article history: Cancer is a complex systemic disorder that affects many organs and tissues and arises from the altered function of Received 5 October 2017 multiple cellular and molecular mechanisms. One of the systems malfunctioning in cancer is the immune system. Received in revised form 18 December 2017 Restoring and improving the ability of the immune system to effectively recognize and eradicate cancer is the main Accepted 11 January 2018 focus of immunotherapy, a topic which has garnered recent and significant interest. The initial excitement about Available online 12 January 2018 immunotherapy, however, has been challenged by its limited efficacy in certain patient populations and the devel- Keywords: opment of adverse effects such as therapeutic resistance and autoimmunity. At the same time, a number of ad- fi Nanoparticles vances in the eld of nanotechnology have sought to address the challenges faced by modern Vaccines immunotherapeutics and allow these therapeutic strategies to realize their full potential. This endeavour requires Adjuvant anunderstanding ofnotonlytheimmunologicalbarriersincancerbutalsothemechanismsbywhichmoderntech- Cell therapy nologies and immunotherapeutics modulate the function of the immune system. Herein, we summarize the major Drug delivery barriers relevant to cancer immunotherapy and review current progress in addressing these obstacles using vari- ous approaches and clinically approved therapies. We then discuss the remaining challenges and how they can be addressed bynanotechnology. Welay out translational considerationsrelevant to thetherapies describedand pro- pose a framework for the development of next-generation nanotechnology-enabled immunotherapies. © 2018 Published by Elsevier B.V. Contents 1. Introduction............................................................... 4 2. Barrierstoeffectiveanti-tumorimmunotherapy............................................... 5 2.1. Biochemicalmechanismsoftumorimmuneescape.......................................... 5 2.1.1. Dysfunctionofantigen-processingmachinery........................................ 5 2.1.2. InhibitoryligandsforthecontrolofT-cellfunction...................................... 5 2.1.3. Immunosuppressivecytokinesandmediators........................................ 5 2.2. Cellularmechanismsoftumorimmuneescape............................................ 5 2.2.1. DysregulationofDCfunction................................................ 5 2.2.2. Immunosuppressivecellpopulations............................................ 6 2.3. Vascular.............................................................. 6 3. Addressingbarrierswithconventionalimmunotherapies........................................... 6 3.1. Cytokinetherapy.......................................................... 6 3.2. AdoptiveT-cellimmunotherapy................................................... 7 3.3. Chimericantigenreceptor(CAR)-Tcelltherapy............................................ 7 3.4. Checkpointinhibitors........................................................ 8 3.5. Cancervaccines.......................................................... 9 4. Addressingbarrierswithnanotechnology.................................................. 9 4.1. Directstrategiestoaddressingbarrierstoimmunotherapy....................................... 9 4.1.1. Offsetting the immunosuppressive tumor microenvironment by tumor-specificdelivery..................... 9 ⁎ Corresponding author at: Frederick National Laboratory for Cancer Research, P.O. Box B, 1050 Boyles Street, Frederick, MD 21702-1201, USA. E-mail address: [email protected] (M.A. Dobrovolskaia). https://doi.org/10.1016/j.addr.2018.01.005 0169-409X/© 2018 Published by Elsevier B.V. 4 E. Hong, M.A. Dobrovolskaia / Advanced Drug Delivery Reviews 141 (2019) 3–22 4.1.2. Buildingmoreeffectivecancervaccineswithnanotechnology..................................10 4.1.3. Influenceofnanoparticlephysicochemicalcharacteristicsonlymphnodetargeting........................10 4.1.4. Adjuvantdeliverybynanoparticles..............................................10 4.1.5. Tunableantigendeliveryforcross-presentationandsustainedrelease..............................10 4.1.6. Nanoparticlesystemsforexternallyinducedimmunotherapy..................................11 4.2. Improvingconventionalimmunotherapies..............................................12 4.2.1. Nanoparticlesforphysiologicallyrelevantcytokinedelivery..................................12 4.2.2. Enhancingadoptiveimmunotherapy.............................................13 5. Translationalconsiderations........................................................14 5.1. Lessonslearnedfrombiotherapeutics.................................................14 5.2. Lessonslearnedfromtherapeuticoligonucleotides...........................................14 5.3. Lessonslearnedfromnanotechnology-basedcombinationproductsandcomplexdrugformulations....................15 5.4. Lessonslearnedfromconventionalimmunotherapy..........................................16 6. Roadmaptothenextgenerationofnanotechnology-enabledimmunotherapies.................................16 Acknowledgments...............................................................17 References...................................................................17 1. Introduction development of resistance to immunotherapy, toxicities associated with therapies such as cytokine or CAR-T cell infusion, and the limited A successful anti-tumor immune response consists of several com- efficacy of approaches such as cancer vaccines [4–7]. New generations ponents. First, tumor-associated antigens (TAAs) must be presented to of immunotherapies will have to address these challenges to achieve effector immune cells by antigen-presenting cells (APCs), which acti- broader applicability and better patient outcomes. vate the effector cells and prepare them for an immune response. Sec- Nanotechnology offers unique opportunities to tackle the clinical ond, effector immune cells must make their way to the tumor, challenges faced by current immunotherapies. Depending on their navigate the tumor vasculature, and penetrate the tumor tissue. Finally, physicochemical characteristics, nanoparticles can alter the pharmaco- these effector cells must bind to and recognize the TAAs on the tumor kinetics, biodistribution, and activity of the therapeutic agents that are surface and kill the tumor cells presenting these antigens. This process loaded within them. These properties allow investigators to engineer is cyclical, wherein cancer cell death can release more antigens for pro- specific nanotechnology-enabled strategies for improving the therapeu- cessing by APCs and activate effector cells, thereby enhancing subse- tic efficacy of anti-cancer drugs. Several nanoparticle drugs have already quent anti-tumor activity [1]. The anti-tumor immune response, been approved for cancer therapy, such as liposomal doxorubicin however, is dysfunctional in cancer. Tumors can induce immune toler- (Doxil), albumin-bound paclitaxel (Abraxane), and liposomal ance by avoiding or blocking the immune system from recognizing irinotecan (Onivyde). In recent years, nanotechnology-enabled strate- TAAs, or by actively suppressing activated effector T cells and natural gies for immunotherapy have been extensively investigated, yielding killer (NK) cells to prevent them from eliminating tumor cells [2, 3]. new strategies and insights for the development of more effective Cancer immunotherapy aims at restoring the proper function of the next-generation immunotherapies. anti-tumor immune response by overcoming mechanisms of tumor im- In this review, we summarize the barriers facing modern immuno- mune evasion or suppression. Recent advances in immunotherapy have therapy and examine the general cellular and biochemical barriers of invigorated the field by identifying and addressing the mechanisms by the tumor microenviroment, the ways they are addressed by modern which tumors avoid being cleared by the immune system. These recent immunotherapies, and the specific barriers facing particular immuno- clinical successes and the approval of several promising immunothera- therapeutic approaches. We also discuss how nanotechnology can di- peutic drugs have spurred substantial scientific and public interest in rectly address the general barriers to generating anti-tumor immunity the field. However, the clinical application of cancer immunotherapy and help overcome the specific barriers that limit current immunother- still faces an array of challenges, including the lack of response or apies. We summarize translational considerations and lessons learned Box 1 Barriers to effective immunotherapy. Problems Mechanisms/barriers Selected references Lack of tumor antigen processing and presentation – Downregulation or loss of class I MHC [10] – Disruption of antigen-processing machinery Disabling of antigen-presenting cells in the tumor – Prevention of DC maturation