Purpose: The aim of our study was to assess if the sodium salt of cobaltabis(dicarbollide) and its di-iodinated derivative (Na[o-COSAN] and Na[8,8′-I₂-o-COSAN]) could be promising agents for dual anti-cancer treatment (chemotherapy + BNCT) for GBM. Methods: The biological activities of the small molecules were evaluated in vitro with glioblastoma cells lines U87 and T98G in 2D and 3D cell models and in vivo in the small model animal Caenorhabditis elegans (C. elegans) at the L4-stage and using the eggs. Results: Our studies indicated that only spheroids from the U87 cell line have impaired growth after treatment with both compounds, suggesting an increased resistance from T98G spheroids, contrary to what was observed in the monolayer culture, which highlights the need to employ 3D models for future GBM studies. In vitro tests in U87 and T98G cells conclude that the amount of ¹⁰B inside the cells is enough for BNCT irradiation. BNCT becomes more effective on T98G after their incubation with Na[8,8′-I₂-o-COSAN], whereas no apparent cell-killing effect was observed for untreated cells. Conclusions: These small molecules, particularly [8,8′-I₂-o-COSAN]⁻, are serious candidates for BNCT now that the facilities of accelerator-based neutron sources are more accessible, providing an alternative treatment for resistant glioblastoma.

Despite some progress, the overall survival of patients with glioblastoma (GBM) remains extremely poor. In this context, there is a pressing need to develop innovative therapy strategies for GBM, namely those based on nanomedicine approaches. Towards this goal, we have focused on nanoparticles (AuNP-SP and AuNP-SPTyr8) with a small gold core (ca. 4 nm), carrying DOTA chelators and substance P (SP) peptides. These new SP-containing AuNPs were characterized by a variety of analytical techniques, including TEM and DLS measurements and UV-vis and CD spectroscopy, which proved their high in vitro stability and poor tendency to interact with plasma proteins. Their labeling with diagnostic and therapeutic radionuclides was efficiently performed by DOTA complexation with the trivalent radiometals ⁶⁷Ga and ¹⁷⁷Lu or by electrophilic radioiodination with ¹²⁵I of the tyrosyl residue in AuNP-SPTyr8. Cellular studies of the resulting radiolabeled AuNPs in NKR1-positive GBM cells (U87, T98G and U373) have shown that the presence of the SP peptides has a crucial and positive impact on their internalization by the tumor cells. Consistently, ¹⁷⁷Lu-AuNP-SPTyr8 showed more pronounced radiobiological effects in U373 cells when compared with the non-targeted congener ¹⁷⁷Lu-AuNP-TDOTA, as assessed by cell viability and clonogenic assays and corroborated by Monte Carlo microdosimetry simulations.

Although ^99mTc is not an ideal Auger electron (AE) emitter for Targeted Radionuclide Therapy (TRT) due to its relatively low Auger electron yield, it can be considered a readily available “model” radionuclide useful to validate the design of new classes of AE-emitting radioconjugates. With this in mind, we performed a detailed study of the radiobiological effects and mechanisms of cell death induced by the dual-targeted radioconjugates ^99mTc-TPP-BBN and ^99mTc-AO-BBN (TPP = triphenylphosphonium; AO = acridine orange; BBN = bombesin derivative) in human prostate cancer PC3 cells. ^99mTc-TPP-BBN and ^99mTc-AO-BBN caused a remarkably high reduction of the survival of PC3 cells when compared with the single-targeted congener ^99mTc-BBN, leading to an augmented formation of γH2AX foci and micronuclei. ^99mTc-TPP-BBN also caused a reduction of the mtDNA copy number, although it enhanced the ATP production by PC3 cells. These differences can be attributed to the augmented uptake of ^99mTc-TPP-BBN in the mitochondria and enhanced uptake of ^99mTc-AO-BBN in the nucleus, allowing the irradiation of these radiosensitive organelles with the short path-length AEs emitted by ^99mTc. In particular, the results obtained for ^99mTc-TPP-BBN reinforce the relevance of targeting the mitochondria to promote stronger radiobiological effects by AE-emitting radioconjugates.

Despite being standard tools in research, the application of cellular and animal models in drug development is hindered by several limitations, such as limited translational significance, animal ethics, and inter-species physiological differences. In this regard, 3D cellular models can be presented as a step forward in biomedical research, allowing for mimicking tissue complexity more accurately than traditional 2D models, while also contributing to reducing the use of animal models. In cancer research, 3D models have the potential to replicate the tumor microenvironment, which is a key modulator of cancer cell behavior and drug response. These features make cancer 3D models prime tools for the preclinical study of anti-tumoral drugs, especially considering that there is still a need to develop effective anti-cancer drugs with high selectivity, minimal toxicity, and reduced side effects. Metallodrugs, especially transition-metal-based complexes, have been extensively studied for their therapeutic potential in cancer therapy due to their distinctive properties; however, despite the benefits of 3D models, their application in metallodrug testing is currently limited. Thus, this article reviews some of the most common types of 3D models in cancer research, as well as the application of 3D models in metallodrug preclinical studies.

Objective. Glioblastoma multiforme (GBM) is the most diagnosed primary brain tumor in adults and remains associated with a poor prognosis due to its aggressive nature. As tumor recurrence is often observed after standard radiation treatment, the use of gold nanoparticles (AuNPs) to improve radiotherapy effectiveness has been proposed as an advanced treatment strategy for this condition. Toward this goal, we investigated the radiosensitizing potential of gastrin releasing peptide receptor (GRPR)-targeted gold nanoparticles (AuNP-BBN) carrying a bombesin peptide (BBN) in glioblastoma cells, when combined with γ and x-ray radiation and in comparison with their non-targeted counterpart (AuNP-DOTA). Approach. Radiation response of U373 and U87 glioblastoma cells was studied upon exposure to Co-60 γ radiation or 160 kVp x-rays and U373 cells were subjected to combined treatment with the AuNPs using the same radiation qualities. The radiobiological effects were assessed via cell viability, clonogenic survival and DNA damage assays, including the determination of the sensitization enhancement ratio (SER). To rationalize the experimental results, Monte Carlo (MC) simulations were performed based on realistic microscopy-based glioblastoma cell models. Main results. U373 and U87 cells proved to be more sensitive to x-rays than to γ radiation. Incubation with AuNP-BBN caused a dose enhancement effect when combined with kilovoltage x-rays but not with Co-60 γ radiation, resulting in reduced U373 cell viability, impaired proliferation and DNA damage. This outcome was not observed in cells treated with the non-targeted AuNP-DOTA, showing that the incorporation of the BBN was crucial for the radiosensitization of GRPR-positive GBM cells. MC simulated radiobiological outcomes were consistent with experimental findings. Significance. GRPR-targeted AuNP-BBN are promising nanotools for developing novel treatment strategies for GBM, acting as local and cell-specific radiotherapy enhancers. Their radiosensitizing effects were accurately predicted using an alternative MC simulation method based on realistic microscopy-based cell phantoms.