Activity of phthalocyanine photosensitizers against human glioblastoma in vitro

Co-Administered Polymeric Nano-Antidotes for Improved Photo-Triggered Response in Glioblastoma

Polymer-based nanoparticles (NPs) are useful vehicles in treating glioblastoma because of their favorable characteristics such as small size and ability to cross the blood–brain barrier, as well as reduced immunogenicity and side effects. The use of a photosensitizer drug such as Verteporfin (BPD), in combination with a pan-vascular endothelial growth factor receptor (VEGFR) tyrosine kinase inhibitor (TKI), Cediranib (CED), encapsulated in NPs will provide the medical field with new research on the possible ways to treat glioblastoma. Concomitant administration of BPD and CED NPs have the potential to induce dual photocytotoxic and cytostatic effects in U87 MG cells by (1) remotely triggering BPD through photodynamic therapy by irradiating laser at 690 nm and subsequent production of reactive oxygen species and (2) inhibiting cell proliferation by VEGFR interference and growth factor signaling mechanisms which may allow for longer progression free survival in patients and fewer systemic side effects. The specific aims of this research were to synthesize, characterize and assess cell viability and drug interactions for polyethylene-glycolated (PEGylated) polymeric based CED and BPD NPs which were less than 100 nm in size for enhanced permeation and retention effects. Synergistic effects were found using the co-administered therapies compared to the individual drugs. The major goal of this research was to investigate a new combination of photodynamic-chemotherapy drugs in nano-formulation for increased efficacy in glioblastoma treatment at reduced concentrations of therapeutics for enhanced drug delivery in vitro.

Phthalocyanine photosensitizers for the treatment of brain tumours

In vitro and in vivo studies were undertaken utilizing an established rat glioma cell line (C6) to compare the phototoxicity characteristics of aluminium tetrasulfonated phthalocyanine (AlSPc), zinc tetrasulfonated phthalocyanine (ZnSPc) and haematoporphyrin derivative (HpD). AlSPc and ZnSPc were inherently less cytotoxic in the dark compared to HpD with 50% colony survival at 275, 355 and 14 mug/ml respectively. An in vitro phototoxicity study at equimolar concentrations demonstrated a 50% reduction of colony survival after exposure to white light at 1 minute for HpD, 10 minutes for AlSPc and 12 minutes for ZnSPc. The presence of fetal bovine serum (FBS) in the medium resulted in reduced in vitro uptake of AlSPc and increased cellular retention which was determined quantitatively by a fluorescence assay following extraction. This assay was also used to determine the in vivo uptake of AlSPc, which was maximal in the intracerebral C6 glioma model at 6 hours (12.3 mug/g tissue) post-intravenous administration of a 1 mg/kg dose of AlSPc, corresponding to a tumour: normal brain ratio of 22:1.

New light on the brain: The role of photosensitizing agents and laser light in the management of invasive intracranial tumors

Invasive intracranial tumors, particularly malignant gliomas, are very difficult to eradicate surgically and carry a dismal prognosis. The vast majority relapse locally indicating that their cure is dependent on radical and complete local excision. However, their ability to invade and hide among normal brain tissue, our inability to visualize and detect them, the low tolerance of brain tissue to ionizing radiation and the presence of the blood brain barrier are the main causes of our failure to eradicate them. Photodynamic detection with 100% specificity and more than 80% sensitivity offers an excellent chance of visualizing camouflaged tumor nests. Also, photodynamic therapy offers a very good chance of targeted destruction of the remaining tumor cells safely following surgical excision and may double the survival of patients harboring these awful tumors. More work needs to be done to refine this promising technology to exploit it to its full potential.

Chelation with metal is not essential for antitumor photodynamic activity of sulfonated phthalocyanines

It is generally assumed that a central metal is essential for the efficiency of phthalocyanines in photodynamic therapy (PDT) of cancer. Contrary to the set opinion, the results of the present study indicate that the metal-free sulfonated phthalocyanines (H2PcSn, where n is the number of sulfonate groups per molecule) possess a considerable photoactivity. The relative phototoxicities of H2PcS1.5, H2PcS2.4, H2PcS3.1 and H2PcS3.8 on HEp2 human epidermoid carcinoma cells were 3.3, 20, 3.3 and 1, respectively, thus demonstrating dependence of the activity on the sulfonation degree, known for metallo-PcSn. A significant delay in tumor growth and a decrease in tumor regrowth rate were observed in mice after PDT with H2PcS2.4. The antitumor effect declined in the order H2PcS2.4 > H2PcS3.1 > H2PcS1.5 and vanished for H2PcS3.8. We demonstrate here that the high photodynamic activity of H2PcS2.4 can be explained by its physicochemical properties in living cells and tissues. Thus, H2PcSn (n is about 2) can be considered as a new alternative in PDT of light-accessible neoplasms and further clinic-oriented studies are warranted.

Photodynamic therapy of brain tumors

Photodynamic therapy (PDT) for the treatment of a variety of brain tumors, particularly gliomas, has been extensively investigated in laboratory studies and has been studied in clinical trials. The main advantage of PDT lies in its ability to select out tumor cells that are infiltrating brain parenchyma and that are responsible for local tumor recurrence, the major therapeutic dilemma in the treatment of gliomas. PDT has been shown to be safe clinically but adequate trials have yet to be undertaken to prove its efficacy and much work remains to be done to optimize treatment. The laboratory studies and clinical trials involving PDT in the treatment of cerebral tumors, particularly the commonest brain tumors, gliomas, are discussed.

The role of photodynamic therapy in posterior fossa brain tumors. A preclinical study in a canine glioma model

Photodynamic therapy was studied in dogs with and without posterior fossa glioblastomas. This mode of therapy consisted of intravenous administration of Photofrin-II at doses ranging from 0.75 to 4 mg/kg 24 hours prior to laser light irradiation in the posterior fossa. Tissue levels of Photofrin-II were four times greater in the tumor than in the surrounding normal brain. Irradiation was performed using 1 hour of 500 mW laser light at a wavelength of 630 nm delivered through a fiberoptic catheter directly into the tumor bed via a burr hole. All animals receiving a high dose (4 or 2 mg/kg) of Photofrin-II developed serious brain-stem neurotoxicity resulting in death or significant residual neurological deficits. A lower dose (0.75 mg/kg) of Photofrin-II produced tumor kill without significant permanent brain-stem toxicity in either the control animals or the animals with cerebellar brain tumors receiving photodynamic therapy.

Laser-induced fluorescence: experimental intraoperative delineation of tumor resection margins

The ability of laser-induced fluorescence spectroscopy to delineate tumor margins intraoperatively was studied using a rat intracerebral glioma model. A fluorescent dye, chloro-aluminum phthalocyanine tetrasulfonate (ClAlPcS4), was injected intravenously 24 hours before tumor resection. The animals underwent tumor resection under the operating microscope, guided by laser-induced fluorescence measurement in one group (Group 1) and visual assessment in the other (Group 2). The Group 1 rats had a significantly reduced volume of residual tumor following resection (0.5 +/- 0.2 cu mm vs. 13.7 +/- 4.0 cu mm, mean +/- standard error of the mean, p less than 0.02). Three of the nine animals in Group 1 were tumor-free at 2 weeks following resection, compared with none of the 10 rats in Group 2 (p less than 0.05). Interference from brain autofluorescence was minimized using spectrally resolved detection and the ClAlPcS4 dye, which has a 680-nm fluorescence peak significantly higher than the 470-nm autofluorescence peak of normal brain. Contrast ratios of up to 40:1 were found for glioma:normal brain fluorescence signals. Spatially-resolved spectra were acquired in approximately 5 seconds using a fiberoptic probe. This study demonstrates the ability of an intraoperative laser-induced fluorescence system to detect tumor margins that could not be identified with the operating microscope.

An in vitro study of the effect of photodynamic therapy on human meningiomas

Despite being benign CNS tumours, meningiomas are not always curable and the likelihood of recurrence depends upon the completeness of initial removal. Adjuvant therapy for incompletely resected meningiomas is generally unsatisfactory and such lesions continue to pose difficult management problems. Photodynamic therapy (PDT) has been employed in the management of recurrent cerebral gliomas but its activity against meningiomas has not been specifically studied. An in vitro study of the effects of PDT against a variety of meningiomas was therefore conducted. It was found that PDT using haematoporphyrin derivative as a photosensitizing drug showed dose-dependent activity against a variety of histological subtypes of meningioma. The activity of PDT against meningiomas should be investigated further and may eventually provide a useful form of adjuvant therapy for incompletely resected lesions.

Laser-induced photodynamic therapy with aluminum phthalocyanine tetrasulfonate as the photosensitizer: differential phototoxicity in normal and malignant human cells in vitro

Photodynamic therapy (PDT) involves the use of laser or noncoherent light energy with photosensitizing dyes to induce a cytotoxic reaction in the target cells, resulting in cell injury and/or death. In this study, we have examined laser-induced phototoxicity in normal human skin fibroblasts and HT-1080 fibrosarcoma cells incubated with aluminum phthalocyanine tetrasulfonate (AlPcS) in vitro. The culture, laser, and photosensitizer parameters were varied in attempts to establish the conditions for differential cytotoxicity between normal and malignant human fibroblasts. Biochemical assays, as a measure of cytotoxicity, included [3H]thymidine incorporation (an index of DNA replication), [35S]methionine incorporation (a measure of protein synthetic activity), and the MTT assay (an indirect index of mitochondrial activity). In the absence of laser irradiation, AlPcS was non-toxic to both cell lines in concentrations up to 25 micrograms/ml. Laser light alone at 675 nm (the absorption maximum of AlPcS) had no effect on the cells at energy densities up to 16 J/cm2. In the presence of 3 or 10 micrograms/ml of AlPcS, both cell lines demonstrated marked energy-dependent toxicity. If an 8-h or a 24-h "efflux" period in AlPcS-free medium was allowed to take place prior to laser irradiation, normal fibroblasts were much less sensitive to PDT, whereas fibrosarcoma cells still exhibited a marked degree of toxicity. The results indicate that, under appropriate treatment conditions, AlPcS is capable of preferentially sensitizing a malignant mesenchymal cell line, while sparing its non-malignant normal cell counterpart.

A review of photoradiation therapy in the management of central nervous system tumours

Photoradiation therapy depends on the selective retention of a photosensitizer within the tumour followed by activation of the sensitizer by irradiating the tumour with light of the appropriate wavelength. The present methods of treatment of cerebral glioma are inadequate and the possible benefit of utilizing photoradiation therapy to obtain improved local control of the tumour has been studied in the laboratory and in clinical trials. The biological basis for photoradiation therapy and the laboratory studies and clinical trials involving the use of photoradiation therapy to treat cerebral tumours are discussed.