Targeting glioblastoma stem cells: The first step of photodynamic therapy

Imaging of heterogeneity in 3D spheroids of U87MG glioblastoma cells and its implications for photodynamic therapy

BACKGROUND

In recent years, pharmacology and toxicology have emphasised the intention to move from in vivo models to simplified 3D objects represented by spheroidal models of cancer. Mitochondria are one of the subcellular organelles responsible for cell metabolism and are often a lucrative target for cancer treatment including photodynamic therapy (PDT).

METHODS

Hanging droplet-grown glioblastoma cells were forced to form spheroids with heterogeneous environments that were characterised by fluorescence microscopy and flow cytometry using fluorescent probes sensitive to oxidative stress and apoptosis. PDT was induced with hypericin at 590 nm.

RESULTS

It was found that the metabolic activity of the cells in the periphery and core of the spheroid was different. Higher oxidative stress and induction of caspase-3 were observed in the peripheral layers after PDT. These parts were more destabilised and showed higher expression of LC3B, an autophagic marker. However, the response of the whole system to the treatment was controlled by the cells in the core of the spheroids, which were hardly affected by the treatment. It has been shown that the depth of penetration of hypericin into this system is an important limiting step for PDT and the induction of autophagy and apoptosis.

CONCLUSIONS

In this work, we have described the fluorescence imaging of vital mitochondria, caspase-3 production and immunostaining of autophagic LC3B in cells from glioblastoma spheroids before and after PDT. Overall, we can conclude that this model represents an in vitro and in vivo applicable alternative for the study of PDT in solid microtumours.

A Review on Gold Nanoclusters for Cancer Phototherapy

Cancer phototherapy, including photodynamic therapy (PDT) and photothermal therapy (PTT), has been extensively studied in recent years because of its noninvasive properties, high efficiency, improved selectivity, and reduced side effects. Gold nanoclusters (AuNCs) have the advantages of high biocompatibility, high biosafety, excellent photoresponse, and high tumor penetration ability. This review analyzes the use of AuNCs in tumor phototherapy in recent years from three aspects, namely, AuNCs in PDT, AuNCs in PTT, and AuNCs in combination therapy, and presents the high potential of AuNCs in cancer phototherapy. This review aims to provide readers with the unique advantages, diversified application approaches, and bright application prospects of AuNCs in phototherapy and to provide insights into strategies for applying AuNCs to tumor phototherapy.

Photodynamic therapy in cancer stem cells - state of the art

Despite significant efforts to control cancer progression and to improve oncology treatment outcomes, recurrence and tumor resistance are frequently observed in cancer patients. These problems are partly related to the presence of cancer stem cells (CSCs). Photodynamic therapy (PDT) has been developed as a therapeutic approach for solid tumors; however, it remains unclear how this therapy can affect CSCs. In this review, we focus on the effects of PDT on CSCs and the possible changes in the CSC population after PDT exposure. Tumor response to PDT varies according to the photosensitizer and light parameters employed, but most studies have reported the successful elimination of CSCs after PDT. However, some studies have reported that CSCs were more resistant to PDT than non-CSCs due to the increased efflux of photosensitizer molecules and the action of autophagy. Additionally, using different PDT approaches to target the CSCs resulted in increased sensitivity, reduction of sphere formation, invasiveness, stem cell phenotype, and improved response to chemotherapy. Lastly, although mainly limited to in vitro studies, PDT, combined with targeted therapies and/or chemotherapy, could successfully target CSCs in different solid tumors and promote the reduction of stemness, suggesting a promising therapeutic approach requiring evaluation in robust pre-clinical studies.

Preclinical Studies with Glioblastoma Brain Organoid Co-Cultures Show Efficient 5-ALA Photodynamic Therapy

BACKGROUND

The high recurrence of glioblastoma (GB) that occurs adjacent to the resection cavity within two years of diagnosis urges an improvement of therapies oriented to GB local control. Photodynamic therapy (PDT) has been proposed to cleanse infiltrating tumor cells from parenchyma to ameliorate short long-term progression-free survival. We examined 5-aminolevulinic acid (5-ALA)-mediated PDT effects as therapeutical treatment and determined optimal conditions for PDT efficacy without causing phototoxic injury to the normal brain tissue.

METHODS

We used a platform of Glioma Initiation Cells (GICs) infiltrating cerebral organoids with two different glioblastoma cells, GIC7 and PG88. We measured GICs-5-ALA uptake and PDT/5-ALA activity in dose-response curves and the efficacy of the treatment by measuring proliferative activity and apoptosis.

RESULTS

5-ALA (50 and 100 µg/mL) was applied, and the release of protoporphyrin IX (PpIX) fluorescence measures demonstrated that the emission of PpIX increases progressively until its stabilization at 24 h. Moreover, decreased proliferation and increased apoptosis corroborated the effect of 5-ALA/PDT on cancer cells without altering normal cells.

CONCLUSIONS

We provide evidence about the effectiveness of PDT to treat high proliferative GB cells in a complex in vitro system, which combines normal and cancer cells and is a useful tool to standardize new strategic therapies.

Most recent update of preclinical and clinical data on radioresistance and radiosensitivity of high-grade gliomas-a radiation oncologist's perspective

PURPOSE

This review article discusses the studies concerning advances in radiotherapy of high-grade gliomas published in the second half of 2021.

METHODS

A literature search was performed in PubMed using the terms ("gliom* and radio*") and time limits 1 July 2021-31 December 2021. The articles were then manually selected for relevance to the analyzed topics.

RESULTS

Considerable progress has been made in the preclinical field on the mechanisms of radioresistance and radiosensitization of high-grade gliomas (HGG). However, fewer early-phase (I/II) clinical trials have been performed and, of the latter, even fewer have produced results that justify moving to phase III. In the 6‑month period under consideration, no studies were published that would lead to a change in clinical practice and the overall survival (OS) of patients remained similar to that of 2005, the year in which it increased significantly for the last time thanks to introduction of the alkylating agent temozolomide.

CONCLUSION

After 17 years of stalemate in improving the OS of patients with HGG, an in-depth analysis of the causes should be carried out in order to identify whether the research efforts conducted so far, including in the radiotherapeutic field, have been the most effective or require improvement. In our opinion, in addition to the therapeutic difficulties related to the biology of HGG tumors (e.g., high infiltrating capacity, multiple resistance mechanisms, blood-brain barrier), some public research policy choices may also play a role, especially in consideration of the limited interest of the pharmaceutical industry in the field of rare cancers.

Development of WRAP5 Peptide Complexes for Targeted Drug/Gene Co-Delivery toward Glioblastoma Therapy

Despite the great progress over the past few decades in both the diagnosis and treatment of a great variety of human cancers, glioblastoma remains the most lethal brain tumor. In recent years, cancer gene therapy focused on non-viral vectors which emerged as a promising approach to glioblastoma treatment. Transferrin (Tf) easily penetrates brain cells of the blood–brain barrier, and its receptor is highly expressed in this barrier and glioblastoma cells. Therefore, the development of delivery systems containing Tf appears as a reliable strategy to improve their brain cells targeting ability and cellular uptake. In this work, a cell-penetrating peptide (WRAP5), bearing a Tf-targeting sequence, has been exploited to condense tumor suppressor p53-encoding plasmid DNA (pDNA) for the development of nanocomplexes. To increase the functionality of developed nanocomplexes, the drug Temozolomide (TMZ) was also incorporated into the formulations. The physicochemical properties of peptide/pDNA complexes were revealed to be dependent on the nitrogen to phosphate groups ratio and can be optimized to promote efficient cellular internalization. A confocal microscopy study showed the capacity of developed complexes for efficient glioblastoma cell transfection and consequent pDNA delivery into the nucleus, where efficient gene expression took place, followed by p53 protein production. Of promise, these peptide/pDNA complexes induced a significant decrease in the viability of glioblastoma cells. The set of data reported significantly support further in vitro research to evaluate the therapeutic potential of developed complexes against glioblastoma.