External radiotherapy is extensively used in clinic to destruct tumors by locally applied ionizing-radiation beams. However, the efficacy of radiotherapy is usually limited by tumor hypoxia-associated radiation resistance. Moreover, as a local treatment technique, radiotherapy can hardly control tumor metastases, the major cause of cancer death. Herein, core-shell nanoparticles based poly(lactic-co-glycolic) acid (PLGA) are fabricate, by encapsulating water-soluble catalase (Cat), an enzyme that can decompose H2 O2 to generate O2 , inside the inner core, and loading hydrophobic imiquimod (R837), a Toll-like-receptor-7 agonist, within the PLGA shell. The formed PLGA-R837@Cat nanoparticles can greatly enhance radiotherapy efficacy by relieving the tumor hypoxia and modulating the immune-suppressive tumor microenvironment. The tumor-associated antigens generated postradiotherapy-induced immunogenic cell death in the presence of such R837-loaded adjuvant nanoparticles will induce strong antitumor immune responses, which together with cytotoxic T-lymphocyte associated protein 4 (CTLA-4) checkpoint blockade will be able to effectively inhibit tumor metastases by a strong abscopal effect. Moreover, a long term immunological memory effect to protect mice from tumor rechallenging is observed post such treatment. This work thus presents a unique nanomedicine approach as a next-generation radiotherapy strategy to enable synergistic whole-body therapeutic responses after local treatment, greatly promising for clinical translation.

Nanoparticle-Enhanced Radiotherapy to Trigger Robust Cancer Immunotherapy.

Radiation therapy for cancer can lead to off-target toxicity and can be ineffective against hypoxic solid tumours and distant metastases. Here, we show that intratumoral injection, in mouse and rabbit xenografts and in patient-derived mouse xenografts, of a sodium alginate formulation containing catalase (Cat) labelled with the therapeutic 131I radioisotope enables long-term relief of tumour hypoxia and complete tumour elimination at low radioactivity doses. On injection, the soluble polysaccharide rapidly transforms into a hydrogel in the presence of endogenous Ca2+, fixing 131I-Cat within the tumours. We also show that local radiotherapy with a formulation that includes the immunostimulatory CpG oligonucleotide combined with systemic checkpoint-blockade therapy using an anti-CTLA-4 antibody leads to metastasis inhibition and protection against tumour rechallenge. The local therapy, which uses only biocompatible components, might enable new strategies for local tumour treatments that can be combined with systemic therapeutic responses, for the inhibition of tumour metastasis and the prevention of tumour recurrence in patients with advanced-stage cancer.

Combined local immunostimulatory radioisotope therapy and systemic immune checkpoint blockade imparts potent antitumour responses

A novel type of bio-nanoreactor with catalase loaded inside TaOx hollow nanoshells is fabricated via a mild one-step method. Such bio-nanoreactors could efficiently improve the tumor oxygenation by supplying oxygen via decomposition of endogenic H2 O2 in a tumor microenvironment, and thus synergistically enhance the efficacy of cancer radiotherapy by both depositing radiation energy within the tumor and overcoming hypoxia-induced radiotherapy resistance.

Catalase-Loaded TaOx Nanoshells as Bio-Nanoreactors Combining High-Z Element and Enzyme Delivery for Enhancing Radiotherapy.

Photodynamic therapy (PDT) is an oxygen-dependent light-triggered noninvasive therapeutic method showing many promising aspects in cancer treatment. For effective PDT, nanoscale carriers are often needed to realize tumor-targeted delivery of photosensitizers, which ideally should further target specific cell organelles that are most vulnerable to reactive oxygen species (ROS). Second, as oxygen is critical for PDT-induced cancer destruction, overcoming hypoxia existing in the majority of solid tumors is important for optimizing PDT efficacy. Furthermore, as PDT is a localized treatment method, achieving systemic antitumor therapeutic outcomes with PDT would have tremendous clinical values. Aiming at addressing the above challenges, we design a unique type of enzyme-encapsulated, photosensitizer-loaded hollow silica nanoparticles with rationally designed surface engineering as smart nanoreactors. Such nanoparticles with pH responsive surface coating show enhanced retention responding to the acidic tumor mi...

L. Góth

Papers

A simple method for determination of serum catalase activity and revision of reference range