UVC-Emitting LuPO4:Pr3+ Nanoparticles Decrease Radiation Resistance of Hypoxic Cancer Cells

Lanthanide conjugate Pr-MPO elicits anti-cancer activity by targeting lysosomal machinery and inducing zinc-dependent cataplerosis

Acquired drug resistance is a major challenge in the management of cancer, which underscores the need for discovery and development of novel therapeutic strategies. We report here the mechanism of the anti-cancer activity of a small coordinate complex composed of the rare earth metal praseodymium (Pr) and mercaptopyridine oxide (MPO; pyrithione). Exposure of cancer cells to relatively low concentrations of the conjugate Pr-MPO (5 µM) significantly impairs cell survival in a p53-independent manner and irrespective of the drug resistant phenotype. Mechanistically, Pr-MPO-induced cell death is caspase-independent, not inhibitable by necrostatin, but associated with the appearance of autophagy markers. However, further analysis revealed incomplete autophagic flux, thus suggesting altered integrity of lysosomal machinery. Supporting the lysosomal targeting activity are data demonstrating increased lysosomal Ca2+ accumulation and alkalinization, which coincides with cytosolic acidification (drop in pHc from 7.75 to 7.00). In parallel, an increase in lysosomal activity of glycosidase alpha acid (GAA), involved in passive glycogen breakdown, correlates with rapid depletion of glucose stores upon Pr-MPO treatment. This is associated with swift cataplerosis of TCA cycle intermediates, loss of NAD+/NADH and increase in pyruvate dehydrogenase (PDH) activity to compensate for pyruvate loss. Addition of exogenous pyruvate rescued cell survival. Notably, lysosomal impairment and metabolic catastrophe triggered by Pr-MPO are suggestive of Zn2+-mediated cytotoxicity, which is confirmed by the ability of Zn2+ chelator TPEN to block Pr-MPO-mediated anti-tumor activity. Together, these results highlight the ability of the small molecule lanthanide conjugate to target the cells' waste clearing machinery as well as mitochondrial metabolism for Zn2+-mediated execution of cancer cells, which could have therapeutic potential against cancers with high metabolic activity.

Ultraviolet (UV) radiation: a double-edged sword in cancer development and therapy

It has long been widely acknowledged that ultraviolet (UV) light is an environment risk factor that can lead to cancer, particularly skin cancer. However, it is worth noting that UV radiation holds potential for cancer treatment as a relatively high-energy electromagnetic wave. With the help of nanomaterials, the role of UV radiation has caught increasing attention in cancer treatment. In this review, we briefly summarized types of UV-induced cancers, including malignant melanoma, squamous cell carcinoma, basal cell carcinoma, Merkel cell carcinoma. Importantly, we discussed the primary mechanisms underlying UV carcinogenesis, including mutations by DNA damage, immunosuppression, inflammation and epigenetic alterations. Historically limited by its shallow penetration depth, the introduction of nanomaterials has dramatically transformed the utilization of UV light in cancer treatment. The direct effect of UV light itself generally leads to the suppression of cancer cell growth and the initiation of apoptosis and ferroptosis. It can also be utilized to activate photosensitizers for reactive oxygen species (ROS) production, sensitize radiotherapy and achieve controlled drug release. Finally, we comprehensively weigh the significant risks and limitations associated with the therapeutic use of UV radiation. And the contradictory effect of UV exposure in promoting and inhibiting tumor has been discussed. This review provides clues for potential clinical therapy as well as future study directions in the UV radiation field. The precise delivery and control of UV light or nanomaterials and the wavelength as well as dose effects of UV light are needed for a thorough understanding of UV radiation.

Application of nano-radiosensitizers in non-small cell lung cancer

Radiotherapy stands as a cornerstone in the treatment of numerous malignant tumors, including non-small cell lung cancer. However, the critical challenge of amplifying the tumoricidal effectiveness of radiotherapy while minimizing collateral damage to healthy tissues remains an area of significant research interest. Radiosensitizers, by methods such as amplifying DNA damage and fostering the creation of free radicals, play a pivotal role in enhancing the destructive impact of radiotherapy on tumors. Over recent decades, nano-dimensional radiosensitizers have emerged as a notable advancement. Their mechanisms include cell cycle arrest in the G2/M phase, combating tumor hypoxia, and others, thereby enhancing the efficacy of radiotherapy. This review delves into the evolving landscape of nanomaterials used for radiosensitization in non-small cell lung cancer. It provides insights into the current research progress and critically examines the challenges and future prospects within this burgeoning field.

Combining Pr3+-Doped Nanoradiosensitizers and Endogenous Protoporphyrin IX for X-ray-Mediated Photodynamic Therapy of Glioblastoma Cells

Glioblastoma multiforme is an aggressive type of brain cancer with high recurrence rates due to the presence of radioresistant cells remaining after tumor resection. Here, we report the development of an X-ray-mediated photodynamic therapy (X-PDT) system using NaLuF₄:25% Pr³⁺ radioluminescent nanoparticles in conjunction with protoporphyrin IX (PPIX), an endogenous photosensitizer that accumulates selectively in cancer cells. Conveniently, 5-aminolevulinic acid (5-ALA), the prodrug that is administered for PDT, is the only drug approved for fluorescence-guided resection of glioblastoma, enabling dual detection and treatment of malignant cells. NaLuF₄:Pr³⁺ nanoparticles were synthesized and spectroscopically evaluated at a range of Pr³⁺ concentrations. This generated radioluminescent nanoparticles with strong emissions from the ¹S₀ excited state of Pr³⁺, which overlaps with the Soret band of PPIX to perform photodynamic therapy. The spectral overlap between the nanoparticles and PPIX improved treatment outcomes for U251 cells, which were used as a model for the thin tumor margin. In addition to sensitizing PPIX to induce X-PDT, our nanoparticles exhibit strong radiosensitizing properties through a radiation dose-enhancement effect. We evaluate the effects of the nanoparticles alone and in combination with PPIX on viability, death, stress, senescence, and proliferation. Collectively, our results demonstrate this as a strong proof of concept for nanomedicine.

Targeted Endoradiotherapy with Lu2O3-iPSMA/-iFAP Nanoparticles Activated by Neutron Irradiation: Preclinical Evaluation and First Patient Image

Prostate-specific membrane antigen (PSMA) is expressed in a variety of cancer cells, while the fibroblast activation protein (FAP) is expressed in the microenvironment of tumors. Previously, we reported the ability of iPSMA and iFAP ligands to specifically target PSMA and FAP proteins, as well as the preparation of stable 177Lu2O3 nanoparticles (<100 nm) functionalized with target-specific peptides. This research aimed to evaluate the dosimetry and therapeutic response of Lu2O3-iPSMA and Lu2O3-iFAP nanoparticles activated by neutron irradiation to demonstrate their potential for theranostic applications in nuclear medicine. The biokinetic behavior, radiation absorbed dose, and metabolic activity ([18F]FDG/micro-PET, SUV) in preclinical tumor tissues (athymic mice), following treatment with 177Lu2O3-iPSMA, 177Lu2O3-iFAP or 177Lu2O3 nanoparticles, were assessed. One patient with multiple colorectal liver metastases (PSMA-positive) received 177Lu2O3-iPSMA under a “compassionate use” protocol. Results indicated no significant difference (p < 0.05) between 177Lu2O3-iPSMA and 177Lu2O3-iFAP, regarding tumor radiation absorbed doses (105 ± 14 Gy, 99 ± 12 Gy and 58 ± 7 Gy for 177Lu2O3-iPSMA, 177Lu2O3-iFAP, and 177Lu2O3, respectively) and tumor metabolic activity (SUV of 0.421 ± 0.092, 0.375 ± 0.104 and 1.821 ± 0.891 for 177Lu2O3-iPSMA, 177Lu2O3-iFAP, and 177Lu2O3, respectively) in mice after treatment, which correlated with the observed therapeutic response. 177Lu2O3-iPSMA and 177Lu2O3-iFAP significantly inhibited tumor progression, due to the prolonged tumor retention and a combination of 177Lu radiotherapy and iPSMA or iFAP molecular recognition. There were negligible uptake values in non-target tissues and no evidence of liver and renal toxicity. The doses received by the patient’s liver metastases (42−210 Gy) demonstrated the potential of 177Lu2O3-iPSMA for treating colorectal liver metastases.

UV emitting nanoparticles enhance the effect of ionizing radiation in 3D lung cancer spheroids

PURPOSE

Radiation therapy for cancer is limited by damage to surrounding normal tissues, and failure to completely eradicate a tumor. This study investigated a novel radiosensitizer, composed of lutetium phosphate nanoparticles doped with 1% praseodymium and 1.5% neodymium cations (LuPO₄:Pr³⁺,Nd³⁺). During X-ray exposure, the particles emit UVC photons (200-280 nm), resulting in increased tumor cell death, by oxygen-independent UVC-induced damage.

METHODS AND MATERIALS

Specially designed LuPO₄:Pr³⁺,Nd³⁺ nanoscintillator particles were characterized by dynamic light scattering, TEM and emission spectroscopy upon excitation. Cell death was determined by reduction in tumor spheroid growth over a 3-week period using a 3D A549 lung cancer model. Cell cycle was evaluated by flow cytometry and cell death pathways were assessed by Annexin V/PI stain as well as quantify apoptotic bodies.

RESULTS

Lung cancer cells expressed no long-term or non-specific toxicity when incubated with LuPO₄:Pr³⁺,Nd³⁺ nanoscintillators. In contrast, there was significant growth inhibition of cell spheres treated with 2.5 mg/ml LuPO₄:Pr³⁺,Nd³⁺ in combination with ionizing radiation (4 or 8 Gy X-ray), compared to radiation alone. A homogeneous distribution of small NPs throughout the entire sphere resulted in more pronounced lethality and growth inhibition, compared to particle distribution limited to the outer cell layers. Growth inhibition after the combined treatment was caused by necrosis, apoptosis and G₂/M cell cycle arrest.

CONCLUSIONS

Newly designed UVC-emitting nanoscintillators (LuPO₄:Pr³⁺,Nd³⁺) in combination with ionizing radiation cause tumor sphere growth inhibition by inducing cell cycle arrest, apoptosis and necrosis. UVC-emitting nanoparticles offer a promising new strategy for enhancing local tumor response to ionizing radiation treatment.

On a local (de-)trapping model for highly doped Pr3+ radioluminescent and persistent luminescent nanoparticles

Trivalent praseodymium exhibits a wide range of luminescent phenomena when doped into a variety of different materials. Herein, radioluminescent NaLuF4:20%Pr3+ nanoparticles are studied. Four different samples of this composition were prepared ranging from 400-70 nm in size. Kinetic studies of radioluminescence as a function of X-ray irradiation time revealed a decrease in the emissions originating from the 1S0 level, due to the formation or optical activation of defects during excitation, and a simultaneous increase in the visible emissions resulting from the lower optical levels. Thermoluminescence measurements elucidated that a local de-trapping mechanism was responsible for the increase in steady state emission and persistent luminescence originating from the lower optical levels. The results and mechanism described through this study serve to provide a novel nanoparticle composition with versatile luminescent properties and provides experimental evidence in favor of a local trapping model.