Motexafin gadolinium enhances the efficacy of aminolevulinic acid mediated-photodynamic therapy in human glioma spheroids

Photodynamic therapy and associated targeting methods for treatment of brain cancer

Brain tumors, including glioblastoma multiforme, are currently a cause of suffering and death of tens of thousands of people worldwide. Despite advances in clinical treatment, the average patient survival time from the moment of diagnosis of glioblastoma multiforme and application of standard treatment methods such as surgical resection, radio- and chemotherapy, is less than 4 years. The continuing development of new therapeutic methods for targeting and treating brain tumors may extend life and provide greater comfort to patients. One such developing therapeutic method is photodynamic therapy. Photodynamic therapy is a progressive method of therapy used in dermatology, dentistry, ophthalmology, and has found use as an antimicrobial agent. It has also found wide application in photodiagnosis. Photodynamic therapy requires the presence of three necessary components: a clinically approved photosensitizer, oxygen and light. This paper is a review of selected literature from Pubmed and Scopus scientific databases in the field of photodynamic therapy in brain tumors with an emphasis on glioblastoma treatment.

Understanding the glioblastoma tumor biology to optimize photodynamic therapy: From molecular to cellular events

Photodynamic therapy (PDT) has recently gained attention as an alternative treatment of malignant gliomas. Glioblastoma (GBM) is the most prevalent within tumors of the central nervous system (CNS). Conventional treatments for this CNS tumor include surgery, radiation, and chemotherapy. Surgery is still being considered as the treatment of choice. Even so, the poor prognosis and/or recurrence of the disease after applying any of these treatments highlight the urgency of exploring new therapies and/or improving existing ones to achieve the definitive eradication of tumor masses and remaining cells. PDT is a therapeutic modality that involves the destruction of tumor cells by reactive oxygen species induced by light, which were previously treated with a photosensitizing agent. However, in recent years, its experimental application has expanded to other effects that could improve overall performance against GBM. In the current review, we revisit the main advances of PDT for GBM management and also, the recent mechanistic insights about cellular and molecular aspects related to tumoral resistance to PDT of GBM.

Interventional MRI-guided local delivery of agents into swine bile duct walls using MR-compatible needle-integrated balloon catheter system

The purpose of this study was to investigate the feasibility of interventional MRI-guided local agent delivery into pig common bile duct (CBD) walls using a newly designed MR-compatible, needle-integrated balloon catheter system. We first designed a needle-integrated balloon catheter system that comprised of a 22 G MR-compatible Chiba biopsy needle and a conventional 12 mm × 2 cm balloon catheter. Under fluoroscopy guidance, a custom needle-balloon system was positioned in the target CBD via a transcholecystic access. T1-weighted MRI was used to localize and reposition the needle-balloon system in the target. A 0.5 mL mixture of motexafin gadolinium (MGd) and trypan blue dye as well as 5-fluorouracil was delivered into the CBD wall through the needle-balloon system. Post-infusion T1-weighted MRI was obtained and contrast-to-noise ratios (CNRs) of CBD walls of pre- and post-MGd-blue infusions were compared by a paired t-test. In addition, post-infusion x-ray cholangiography was achieved to evaluate the potential injuries of CBDs by the needle-balloon system. Subsequent histologic analysis was performed to correlate and confirm the imaging findings. A post-infusion cholangiogram did not show any extravasation of contrast agent, indicating no procedure-related damage to the CBDs. MRI demonstrated clear enhancement of the target bile duct walls infused with MGd-trypan blue dye with average penetration depth of 4.7 ± 1.2 mm and an average MGd perfusion length of 21 ± 1.5 mm in the bile ducts and their surrounding tissues. The average CNR of the post-infusion bile ducts was significant higher than that of the pre-infusion bile ducts (110.6 ± 22 versus 5.7 ± 2.8, p < 0.0001). Histology depicted the blue dye staining and red fluorescence of MGd through the target CBD walls, which was well correlated with the imaging findings. It is feasible to use the new MR-compatible, needle-integrated balloon catheter system for intrabiliary local agent delivery into CBD walls under MRI guidance, which may open new avenues for efficient management of pancreatobiliary malignancies using MR-guided interventional oncology.

Tetra-sulfonate phthalocyanine zinc-bovine serum albumin conjugate-mediated photodynamic therapy of human glioma

Background

Glioma is the most common brain malignancy with poor prognosis. The current treatments for gliomas are mainly based on surgery, chemotherapy, and radiotherapy, which exhibit limited efficacy. Photodynamic therapy (PDT) using photosensitizers has been applied to glioma therapy. However, different photosensitizers usually lead to different therapeutic effects and adverse reactions.

Objective

This study investigates the anti-tumor effect of photosensitizer ZnPcS4-BSA in xenograft glioma tumors.

Methods

The xenograft glioma tumor model was established by inoculating nude mice with U251 cells. Tumor growth was evaluated by tumor volume, weight, and inhibition rate. Cell apoptosis was evaluated using TUNEL staining. Vascular endothelial growth factor (VEGF) expression and microvessel density were measured by immunohistochemistry.

Results

Significant decreases in tumor volume and weight as well as significant increases in tumor inhibition rate, cell apoptosis, VEGF expression, and microvessel density were observed in mice in the low- and high-dose PDT groups compared to the control, irradiation alone, and photosensitizer alone groups. No significant difference in cytotoxicity was observed between control group and photosensitizer alone group. Photosensitizer ZnPcS4-BSA significantly inhibited xenograft glioma tumor growth through induction of apoptosis.

Conclusion

PDT using ZnPcS4-BSA may be effective for the therapy of gliomas.

Increased expression of ABCB6 enhances protoporphyrin IX accumulation and photodynamic effect in human glioma

BACKGROUND

Glioma recurrence usually occurs close to the tumor resection margins as a result of residual infiltrating glioma cells. 5-aminolevulinic acid (ALA) fluorescence-guided resection of gliomas has been demonstrated to enhance discrimination of tumor tissue and to improve survival. ALA-based photodynamic therapy is an effective albeit still experimental adjuvant treatment option for gliomas. However, insufficient protoporphyrin IX (PpIX) accumulation may limit the benefits of fluorescence-guided resection and photodynamic therapy.

METHODS

We investigated the expression of the ATP-binding cassette transporter ABCB6, which regulates porphyrin synthesis, in surgical specimens from human gliomas and manipulated ABCB6 in human glioma cell lines.

RESULTS

Our findings demonstrated that expression levels of ABCB6 were greatly elevated in human gliomas compared with normal brain tissues and correlated with World Health Organization histologic grade. A previously undescribed finding was that ABCB6 mRNA expression in solidly fluorescing tumor tissues was higher than that in vaguely fluorescing tumors, suggesting that ABCB6 may be at least in part responsible for PpIX accumulation in glioma cells. Accordingly, ABCB6 overexpression in glioma cell lines caused a marked increase in intracellular levels of PpIX, and was more sensitive to ALA-induced photodynamic therapy-events that could be prevented by silencing ABCB6 via siRNA treatment.

CONCLUSIONS

Our findings indicate a crucial role of ABCB6 in ALA metabolism and accumulation of PpIX in glioma. ABCB6 overexpression is a potential approach to enhance accumulation of PpIX for optimizing the subjective discrimination of vague fluorescence and improving the efficacy of ALA-based photodynamic therapy.

Photodynamic therapy for malignant pleural mesothelioma: the future of treatment?

Malignant pleural mesothelioma is a deadly incurable cancer, with a median survival of approximately 9 months. The best available chemotherapy, arguably the standard of care, only yields a 40% response rate and an 11-week extension in median survival. Surgery, the modality most likely to be associated with prolonged remission, remains investigational and must always be combined with other modalities in an effort to treat the microscopic disease that will remain even after the most aggressive operations. One such modality, photodynamic therapy, is a light-based cancer treatment that has features making it particularly well suited as a component of a surgery-based multimodal treatment plan. Utilizing intraoperative photodynamic therapy has enabled development of a less drastic surgical procedure that is also yielding some encouraging survival results. A unique aspect of photodynamic therapy is its stimulation of a tumor-directed immune response, a feature that offers promise for designing future treatments.

Silencing of ferrochelatase enhances 5-aminolevulinic acid-based fluorescence and photodynamic therapy efficacy

Background:

Recurrence of glioma frequently occurs within the marginal area of the surgical cavity due to invading residual cells. 5-Aminolevulinic acid (5-ALA) fluorescence-guided resection has been used as effective therapeutic modalities to improve discrimination of brain tumour margins and patient prognosis. However, the marginal areas of glioma usually show vague fluorescence, which makes tumour identification difficult, and the applicability of 5-ALA-based photodynamic therapy (PDT) is hampered by insufficient therapeutic efficacy in glioma tissues.

Methods:

To overcome these issues, we assessed the expression of ferrochelatase (FECH) gene, which encodes a key enzyme that catalyses the conversion of protoporphyrin IX (PpIX) to heme, in glioma surgical specimens and manipulated FECH in human glioma cell lines.

Results:

Prominent downregulation of FECH mRNA expression was found in glioblastoma tissues compared with normal brain tissues, suggesting that FECH is responsible for PpIX accumulation in glioblastoma cells. Depletion of FECH by small interference RNA enhanced PpIX fluorescence after exposure to 5-ALA concomitant with increased intracellular PpIX accumulation in glioma cells. Silencing of FECH caused marked growth inhibition and apoptosis induction by PDT in glioma cells.

Conclusion:

These results suggest that knockdown of FECH is a potential approach to enhance PpIX fluorescent quality for optimising the subjective discrimination of vague fluorescence and improving the effect of 5-ALA-PDT.