Hematoporphyrin derivative photocytotoxicity of human glioblastoma in cell culture

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.

Hyperthermic sensitization by hematoporphyrin on glioma cells

This study investigated: (1) the effect of Hp as a hyperthermic sensitizer on glioma cells; and (2) the possible mechanism of hyperthermic sensitization by Hp using an exogenous scavenger specific to a particular reactive oxygen species. Hp at nontoxic doses at 37 degrees C significantly enhanced thermal cell damage at 41.5 degrees C and above in a dose-dependent manner. Thermal cell damage enhancement by HP was effectively suppressed by the addition of beta-carotene, a singlet oxygen scavenger, or SOD, a superoxide scavenger, but not by the addition of mannitol or catalase. These results support the following hypothesis: The generation of superoxide is increased in cells treated with Hp in combination with hyperthermia. Thermal cell damage enhancement by Hp is probably mediated by singlet oxygen generated via superoxide in an alternative pathway different from that of photosensitization. Hp has potential as a hyperthermic sensitizer because of the following advantages: (1) its dose-dependent enhancement of thermal cell damage; and (2) the lack of toxicity at physiological temperature at doses of Hp required for hyperthermic sensitization of tumour cells.

Influence of epidermal growth factor on photodynamic therapy of glioblastoma cells in vitro

Photodynamic therapy (PDT) could be a useful adjuvant in glioblastoma treatment. The fact that epidermal growth factor (EGF) and its receptor are involved in glioblastoma growth control led us to investigate the relationships between EGF and PDT with respect to three different glioma cell lines (C6, T98 G, U87 MG) responsive to growth stimulation by EGF. Flow cytometric analysis revealed that each cell line expressed EGF receptors. PDT was then applied to the cells using haematoporphyrin derivative (HPD) as photosensitizer and argon laser irradiation. When cells were incubated for 2 h with HPD (0.1-10 micrograms/ml) and then laser-irradiated (lambda = 514 nm; energy density 25 J/cm2), all three cell lines showed photosensitivity. The median lethal dose was respectively 3, 4.5 and 2.7 micrograms/ml for C6, T98 G and U87 MG. EGF (2-50 ng/ml) had no effect on HPD- and laser-induced toxicity when added to cells before PDT, whereas toxicity decreased for all three cell lines when EGF was added after PDT. HPD (1-2 micrograms/ml, incubation times 30-180 min) also induced an increase in EGF receptor expression for the C6 line.

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.

Photodynamic therapy of brain tumors

Photodynamic therapy (PDT) is a binary treatment modality suitable for various malignant tumors including brain. It involves the selective uptake of a photosensitizer into tumor followed by intraoperative irradiation of the tumor with light of an appropriate wavelength to cause activation of the sensitizer and subsequent selective tumor destruction. PDT has been extensively investigated in laboratory studies and has been used in clinical trials to treat a variety of brain tumors, particularly gliomas. The main advantage of PDT lies in its ability to select out infiltrating tumor cells that are responsible for local tumor recurrence. The therapy 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 biological basis, laboratory studies, and clinical trials involving PDT in the treatment of cerebral tumors are discussed.

Photodynamic therapy for intracranial neoplasms. Literature review and institutional experience

Primary malignant glial neoplasms of the central nervous system have a dismal 2-yr prognosis. An innovative approach to these formidable lesions is photodynamic therapy that employs a chemotherapeutic photosensitizing agent in combination with wavelength specific light to produce cytotoxic reactions capable of destroying neoplastic tissues. Animal and initial clinical studies of the application of photodynamic therapy to intracranial neoplasms have been promising. Parameters to optimize the efficacy of this treatment are under investigation. A review of the preclinical and clinical studies of photodynamic therapy for intracranial neoplasms is described.

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.

Photodynamic therapy for intracranial neoplasms: development of an image-based computer-assisted protocol for photodynamic therapy of intracranial neoplasms

Photodynamic therapy is being studied as an adjuvant therapy for malignant gliomas. Therapeutic efficacy is based on photosensitizer uptake kinetics and the ability to deliver adequate light doses to an appropriate treatment volume at the optimal time. Our laboratory has developed an image-based, computer-assisted treatment-planning protocol to study the treatment variables leading to optimizing photodynamic therapy for intracranial neoplasms. Fifteen patients with recurrent malignant glial tumors underwent 16 treatments in the developmental phase of the project in which light treatment volume was progressively expanded. Group I (n = 4) received postresection intracavitary photoillumination only, Group II (n = 3) received limited interstitial/intracavitary photoillumination, and Group III (n = 9) received multiple interstitial/intracavitary photoillumination. Between 3 and 18 interstitial fiber probes were placed through optically lucent tumor access catheters. Computed three-dimensional image-based treatment planning provided reproducible data-based tumor volumes, treatment volumes, and stereotactic accuracy for tumor volume resection and interstitial light fiber insertion. Initial observations include: 1) treatment failures occur outside of the effective light treatment volumes; 2) effective light volumes can be expanded safely with multiple stereotactically implanted interstitial light fibers; and 3) optimal treatment involves individualized tailoring of light dose volume and geometry. This protocol allows standardized scientific study of the variables affecting the application of photodynamic therapy for intracranial neoplasms.

Effect of argon laser and Photofrin II on murine neuroblastoma cells

Laser-induced fluorescence (LIF) of photosensitizers is used to detect cancer. The effect of argon laser light with an average irradiance of 31 mW cm-2 and Photofrin II (Dihematoporphyrin ether, DHE) at concentrations of 1.0 and 5.0 micrograms ml-1 on C1300 murine neuroblastoma cells (MNB, NB41A3) in vitro was investigated. Growth curves and cell viability (trypan blue dye exclusion) were determined at 1, 24, 96, and 144 hr post-irradiation. Light doses of 1.8 and 9.0 J cm-2 combined with 5.0 micrograms DHE ml-1 decreased both cell numbers and viability, immediately and up to 144 hr postirradiation. Argon laser light alone at a fluence of 9.0 J cm-2 caused reversible injury to the cells. This in vitro study shows that both low energy argon laser light and low dose DHE are cytocidal to C1300 MNB cells. LIF promises to aid in the detection and destruction of neuroblastoma. Surgeons should be aware that tissue irreversible damage is likely to occur when performing LIF detection of neuroblastoma. The doses of laser light and of Photofrin II found to be toxic to neuroblastoma cells in culture may provide guidelines for photodynamic therapy ablation of neuroblastoma clinically.

An improved photochemical model of embolic cerebral infarction in rats

To provide further evidence that the multiple cerebral infarcts found in rats following photochemical damage to the carotid artery are caused by emboli and to eliminate the systemic hypotension and heating of the blood reported with the previous photochemical embolic stroke model (rose bengal and a green laser), I have modified the photochemical technique. Brain pathology was studied in 18 Wistar rats following carotid artery irradiation with a red laser (632 nm) at powers ranging from 100 to 800 mW/cm2 for 10 or 20 minutes following the injection of the photosensitizing dye Photofrin II. Multiple cerebral arterioles were occluded by platelet aggregates containing frequent erythrocytes and leukocytes, identical to the thrombotic material in the carotid artery but different from the platelet aggregates seen in the carotid artery and the brain in the rose bengal model. Eighty infarcts were distributed randomly throughout the brain ipsilateral to the nonocclusive carotid thrombus. Significant heating (0.5 degree C or more) of the blood occurred only with laser powers higher (1,600 mW/cm2) or laser irradiations longer (25 minutes) than those used in the improved model of embolic stroke. This model mimics one mechanism of stroke in humans and provides a means to study systematically the morphological evolution of small cerebral infarcts.

Photodynamic therapy for rat pituitary tumor in vitro and in vivo using pheophorbide-a and white light

This is the first report on the use of photodynamic therapy (PDT) for rat pituitary tumor in vivo. Rat pituitary tumor (GH3) cells were cultured, GH3 tumor was subcutaneously implanted in nude mice, and pheophorbide-a (Ph-a) and white light were prepared. Photocytotoxicity proportional to Ph-a concentration, intensity of irradiation, and incubation time was observed in vitro. Despite the delay in the disappearance of Ph-a from the tumor, Ph-a in the pituitary gland rapidly decreased after intravenous administration in vivo. Through PDT, the tumor grossly disappeared, the plasma levels of rat growth hormone secreted from the tumor also remarkably decreased, and the development of giantism was inhibited. These results indicate that PDT is effective against rat pituitary tumor.

Photoradiation therapy and its potential in the management of neurological tumors

Photoradiation therapy is a form of local treatment that depends on the selective retention of a photosensitizer, such as hematoporphyrin derivative (HpD), by the tumor followed by treatment with light of an appropriate wavelength to activate the sensitizer in the tumor. The selective uptake of HpD by cerebral tumors has been demonstrated both in laboratory animal model studies and in clinical studies, and selective destruction of intracerebral tumors has been demonstrated in animal glioma models. The biological basis for photoradiation therapy and, in particular, the mechanisms for the selective uptake of the sensitizer into the tumor and the destruction of tumor with photoradiation therapy are discussed. Current evidence suggests that singlet oxygen is the major intermediary leading to cell damage, although other radicals such as hydrogen peroxide and hydroxyl radicals may be involved. Other studies suggest that the initial damage is to the blood vessels, and the tumor subsequently undergoes ischemic changes. Sixty-four patients treated with photoradiation therapy have been reported in the literature. The initial clinical studies were disappointing in their therapeutic effect but these studies often included treatment of recurrent gliomas and low doses of light were used. Technical advances, particularly in laser technology, have enabled more effective photoradiation therapy and the clinical trials are reviewed.