Nanovectorized radiotherapy: a new strategy to induce anti-tumor immunity

The Chemical Scaffold of Theranostic Radiopharmaceuticals: Radionuclide, Bifunctional Chelator, and Pharmacokinetics Modifying Linker

Therapeutic radiopharmaceuticals have been researched extensively in the last decade as a result of the growing research interest in personalized medicine to improve diagnostic accuracy and intensify intensive therapy while limiting side effects. Radiometal-based drugs are of substantial interest because of their greater versatility for clinical translation compared to non-metal radionuclides. This paper comprehensively discusses various components commonly used as chemical scaffolds to build radiopharmaceutical agents, i.e., radionuclides, pharmacokinetic-modifying linkers, and chelators, whose characteristics are explained and can be used as a guide for the researcher.

Nanoparticle-Mediated Immunogenic Cell Death Enables and Potentiates Cancer Immunotherapy

Cancer immunotherapies that train or stimulate the inherent immunological systems to recognize, attack, and eradicate tumor cells with minimal damage to healthy cells have demonstrated promising clinical responses in recent years. However, most of these immunotherapeutic strategies only benefit a small subset of patients and cause systemic autoimmune side effects in some patients. Immunogenic cell death (ICD)-inducing modalities not only directly kill cancer cells but also induce antitumor immune responses against a broad spectrum of solid tumors. Such strategies for generating vaccine-like functions could be used to stimulate a "cold" tumor microenvironment to become an immunogenic, "hot" tumor microenvironment, working in synergy with immunotherapies to increase patient response rates and lead to successful treatment outcomes. This Minireview will focus on nanoparticle-based treatment modalities that can induce and enhance ICD to potentiate cancer immunotherapy.

Characterization of the distribution, retention, and efficacy of internal radiation of 188Re-lipid nanocapsules in an immunocompromised human glioblastoma model

Internal radiation strategies hold great promise for glioblastoma (GB) therapy. We previously developed a nanovectorized radiotherapy that consists of lipid nanocapsules loaded with a lipophilic complex of Rhenium-188 (LNC¹⁸⁸Re-SSS). This approach resulted in an 83 % cure rate in the 9L rat glioma model, showing great promise. The efficacy of LNC¹⁸⁸Re-SSS treatment was optimized through the induction of a T-cell immune response in this model, as it is highly immunogenic. However, this is not representative of the human situation where T-cell suppression is usually encountered in GB patients. Thus, in this study, we investigated the efficacy of LNC¹⁸⁸Re-SSS in a human GB model implanted in T-cell deficient nude mice. We also analyzed the distribution and tissue retention of LNC¹⁸⁸Re-SSS. We observed that intratumoral infusion of LNCs by CED led to their complete distribution throughout the tumor and peritumoral space without leakage into the contralateral hemisphere except when large volumes were used. Seventy percent of the ¹⁸⁸Re-SSS activity was present in the tumor region 24 h after LNC¹⁸⁸Re-SSS injection and no toxicity was observed in the healthy brain. Double fractionated internal radiotherapy with LNC¹⁸⁸Re-SSS triggered survival responses in the immunocompromised human GB model with a cure rate of 50 %, which was not observed with external radiotherapy. In conclusion, LNC¹⁸⁸Re-SSS can induce long-term survival in an immunosuppressive environment, highlighting its potential for GB therapy.

Dendrimers as Innovative Radiopharmaceuticals in Cancer Radionanotherapy

Radiotherapy is one of the most commonly used cancer treatments, with an estimate of 40% success that could be improved further if more efficient targeting and retention of radiation at the tumor site were achieved. This review focuses on the use of dendrimers in radionanotherapy, an emerging technology aimed to improve the efficiency of radiotherapy by implementing nanovectorization, an already established praxis in drug delivery and diagnosis. The labeling of dendrimers with radionuclides also aims to reduce the dose of radiolabeled materials and, hence, their toxicity and tumor resistance. Examples of radiolabeled dendrimers with alpha, beta, and Auger electron emitters are commented, along with the use of dendrimers in boron neutron capture therapy (BNCT). The conjugation of radiolabeled dendrimers to monoclonal antibodies for a more efficient targeting and the application of dendrimers in gene delivery radiotherapy are also covered.

Development of Biocompatible and Functional Polymeric Nanoparticles for Site-Specific Delivery of Radionuclides

Introduction

Encapsulation of biologically active molecules into nanoparticles (NPs), for site-specific delivery, is a fast growing area. These NPs must be biocompatible, non-toxic, and able to release their load in a controlled way. We have developed a series of NPs based on (bio)degradable and biocompatible poly(malic acid) derivatives, poly(benzyl malate) (PMLABe), with its PEG-grafted stealth analog and target-specific biotin-PEG-b-PMLABe one. A lipophilic radiotracer has then been encapsulated into these NPs.

Methods

Monomers were synthesized from dl-aspartic acid. PEG₄₂-b-PMLABe₇₃ and Biot-PEG₆₆-b-PMLABe₇₃ block copolymers were obtained by anionic ring-opening polymerization of benzyl malolactonate in presence of α-methoxy-ω-carboxy-PEG₄₂ and α-biotin-ω-carboxy-PEG₆₆ as initiators. NPs were prepared by nanoprecipitation. Size, polydispersity, and zeta potential were measured by dynamic light scattering (DLS) and zetametry. ^99mTc-SSS was prepared as previously described. Encapsulation efficacy was assessed by varying different parameters, such as encapsulation with preformed NPs or during their formation, influence of the solvent, and of the method to prepare the NPs. After decay, ^99mTc-loaded NPs were also analyzed by DLS and zetametry. NPs’ morphology was assessed by transmission electron microscopy.

Results

^99mTc-SSS was added during nanoprecipitation, using two different methods, to ensure good encapsulation. Radiolabeled NPs present increased diameters, with identical low polydispersity indexes and negative zeta potentials in comparison to non-radiolabeled NPs.

Conclusion

A radiotracer was successfully encapsulated, but some further optimization is still needed. The next step will be to modify these radiolabeled NPs with a hepatotrope peptide, and to replace ^99mTc with ¹⁸⁸Re for therapy. Our team is also working on drugs’ encapsulation and grafting of a fluorescent probe. Combining these modalities is of interest for combined chemo-/radiotherapy, bimodal imaging, and/or theranostic approach.

Mutations of the human interferon alpha-2b (hIFNα-2b) gene in cancer patients receiving radiotherapy

This research aimed to find out the impact of ionizing radiations on the hIFNα-2b gene of radiotherapy treated cancer patients. The gene hIFNα-2b synthesizes a protein which is an important anticancerous and antiviral protein. The cancer patients (breast, lung, thyroid, oral and prostate) who were undergoing a radiotherapy treatment were selected. A molecular analysis was performed for DNA isolation and gene amplification through PCR, to identify gene mutations. Further, by bioinformatics tools we concluded that how mutations identified in gene sequences have led to the alterations in the hINFα-2b protein in radiotherapy receiving cancer patients. The 32% mutations in the hINFα-2b gene were identified and all were frameshift mutations. Radiotherapy can impact the immune system and cancer patients may modulate their immunity. Understaning the mechanisms of radiotherapy-elicited immune response may be helpful in the development of those therapeutic interventions that can enhance the efficacy of radiotherapy.

Image-guided interventional therapy for cancer with radiotherapeutic nanoparticles

One of the major limitations of current cancer therapy is the inability to deliver tumoricidal agents throughout the entire tumor mass using traditional intravenous administration. Nanoparticles carrying beta-emitting therapeutic radionuclides that are delivered using advanced image-guidance have significant potential to improve solid tumor therapy. The use of image-guidance in combination with nanoparticle carriers can improve the delivery of localized radiation to tumors. Nanoparticles labeled with certain beta-emitting radionuclides are intrinsically theranostic agents that can provide information regarding distribution and regional dosimetry within the tumor and the body. Image-guided thermal therapy results in increased uptake of intravenous nanoparticles within tumors, improving therapy. In addition, nanoparticles are ideal carriers for direct intratumoral infusion of beta-emitting radionuclides by convection enhanced delivery, permitting the delivery of localized therapeutic radiation without the requirement of the radionuclide exiting from the nanoparticle. With this approach, very high doses of radiation can be delivered to solid tumors while sparing normal organs. Recent technological developments in image-guidance, convection enhanced delivery and newly developed nanoparticles carrying beta-emitting radionuclides will be reviewed. Examples will be shown describing how this new approach has promise for the treatment of brain, head and neck, and other types of solid tumors.