Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0027651 (tumor)
 685,946 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The aim of our study was to find out if Photofrin II, a cytotoxic drug used routinely in photodynamic therapy (PDT), can induce immune responses in vitro, and to compare its effects with those of the protoporphyrin 9, hemin, which also has antitumor properties. We tested the effect of these porphyrins on lymphocyte proliferation and secretion of interleukin-2, interleukin-3, tumor necrosis factor alpha (TNFalpha) and interferon gamma (IFNgamma), by human or murine mononuclear cells (MNC) without an activating light. Both the Photofrin II- and hemin-treated cells showed a significant increase in cytokine secretion in the presence of suboptimal concentrations of mitogen. Moreover, Photofrin II and hemin significantly increased production of TNFalpha and IFNgamma even in the absence of mitogen. The cellular binding sites of Photofrin II and hemin to MNC were localized by electromicroscopy or fluorescence. Combined stimulation of cells by mitogens and porphyrins maintained optimal vital ionic balance of potassium, sodium and chlorine in the lymphocytes. In the cells thus treated there was a significant increase in intracellular calcium, a vital second messenger for lymphokine secretion. We demonstrate that the effect of Photofrin II on the immune system involves enhanced cytokine secretion which may account for the subsequent tumor eradication by PDT.
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PMID:Photofrin II induces cytokine secretion by mouse spleen cells and human peripheral mononuclear cells. 886 45

Photosensitizer is known to spread with vasogenic edema fluid arising from a cerebral lesion (Neurosurg 33:1075-1082, 1993), which may be essential for sensitizing malignant cells outside the main tumor mass. The present experiments seek to elucidate whether resultant necrosis of perifocal brain tissue after laser irradiation follows a corresponding time pattern and whether damage depends on the photosensitizer dose. Male Wistar rats were anaesthetized with chloralhydrate for venous cannulation, craniotomy and focal cold lesion in order to induce vasogenic edema. Simultaneously, Photofrin II (PF II) was administered at a dose of 5 mg kg-1. The animals were re-anaesthetized after either 4, 12 or 24 h for the irradiation of lesion and perifocal tissue with 200 J cm-2 of laser light (630 nm). The brains of other animals were irradiated 4 h after cold lesion with 200 J cm-2 after receiving either 0, 2.5 or 5 mg kg-1 PF II (all groups: n = 6). Resultant necrosis was assessed planimetrically in serial coronal cryosections of brains perfusion fixed 24 h after irradiation. Necrosis was significantly enhanced with irradiation 4 h after cold lesion and photosensitizer (avg. area +/- SD: 4.3 +/- 0.7 mm2) compared with lesion only (0.84 +/- 0.2 mm2). Maximal necrosis (6.3 +/- 1.6 mm2) occurred with irradiation 12 h after lesion, whereas necrosis was only slightly increased with irradiation at 24 h (2.8 +/- 0.4 mm2). Furthermore, the area of necrosis was dependent on the sensitizer dose (0 mg kg-1: 0.7 +/- 0.3 mm2, 2.5 mg kg-1: 2.09 +/- 0.2 mm2, 5 mg kg-1: 4.3 +/- 0.7 mm2; all differences p < 0.05). Therefore, to prevent unwanted side-effects such as necrosis of edematous but otherwise healthy, peritumoral tissue in the treatment of malignant cerebral tumors by PDT, tribute should be paid to the possibility of time and dose dependent sensitization of the perifocal tissue after i.v. administration of photosensitizer.
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PMID:Photodynamic therapy within edematous brain tissue: considerations on sensitizer dose and time point of laser irradiation. 900 56

Photodynamic therapy (PDT) has been considered as a potential therapy for superficial bladder carcinomas. Cutaneous photosensitivity and reduction of bladder capacity are the two well-known complications following systemic administration of the commonly used photosensitizer, Photofrin II (PII). The objective of the present study was to evaluate whether intravesical (i.b.) instillation of photosensitizers for PDT of bladder cancer might be a more suitable treatment method. Female Fischer rats were utilized to develop orthotopic and heterotopic bladder tumor models. Rats bearing orthotopic bladder tumors were treated either intravesically or intravenously with graded doses of 5-aminolevulinic acid (ALA) or PII. Normal rats received the same doses of ALA or PII. As well, rats bearing heterotopic tumor were studied for comparison. The biodistribution times (times allowed for tissue uptake and bioconversion following drug administration) were 2, 4 or 6 h. Porphyrin fluorescence intensities within tumor, urothelium, submucosa, bladder muscularis and abdominal muscle were quantitated by confocal laser scanning microscopy. Following intravenous (i.v.) injection of ALA, tumor protoporphyrin IX (PpIX) levels peaked at 4 h and diminished by 6 h. The PpIX ratios of tumor-to-bladder mucosa, submucosa and muscle layers were 3:1, 5:1 and 8:1, respectively, 4 h following 1000 mg/kg ALA injection. After ALA instillation, the optimal biodistribution time appeared to be 4 h. Bladder instillation provided comparable tumor labeling with the i.v. route, but lost selectivity of PpIX accumulation between tumor and normal urothelium. The PpIX ratio of tumor-to-bladder muscularis was 5:1. After i.b. instillation of PII, porphyrin fluorescence was detected only within tumor and urothelium, while porphyrin fluorescence was mainly located in bladder submucosa following i.v. injection. Intravesical administration of ALA or PII might be feasible for PDT of superficial bladder cancers.
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PMID:Biodistribution of Photofrin II and 5-aminolevulinic acid-induced protoporphyrin IX in normal rat bladder and bladder tumor models: implications for photodynamic therapy. 961 41

Pretreatment of EMT-6 murine tumor cells for 24 h with 10(-4) M 8-methoxypsoralen (8-MOP) increased the photocytotoxicity of Photofrin II (P2) after cell exposure to low doses (1-1.5 J/cm2) of UVA by two- to three-fold. 8-MOP alone had no cytotoxic action under these experimental conditions and did not significantly change the amount of P2 recovered in cells. 8-MOP enhanced the lipid peroxidation end product formation measured as thiobarbituric acid reactive substances (TBARS) during cell photosensitization by P2. The psoralen alone also slightly increased the TBARS level after UVA exposure. These results suggest that 8-MOP, albeit non-photocytotoxic by itself under our experimental conditions, could enhance the efficiency of P2 by increasing cellular lipid peroxidation following light exposure.
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PMID:8-Methoxypsoralen potentiates the photocytotoxic effect of Photofrin II towards EMT-6 murine tumor cells. 968 80

Tolyporphin (TP), a porphyrin extracted from cyanobacteria, was found to be a very potent photosensitizer of EMT-6 tumor cells grown both in vitro as suspensions or monolayers and in vivo in tumors implanted on the backs of C.B17/Icr severe combined immunodeficient mice. Thus, during photodynamic treatment (PDT) of EMT-6 tumor cells in vitro, the photokilling effectiveness of TP measured as the product of the reciprocal of D50 (the light dose necessary to kill 50% of cells) and the concentration of TP is approximately 5000 times higher than that of Photofrin II (PII), the only PDT photosensitizer thus far approved for clinical trials. TP almost exclusively localizes in the perinuclear region and specifically in the endoplasmic reticulum (ER), as shown by microspectrofluorometry on single living EMT-6 cells costained with the ER and/or Golgi fluorescent vital probes, 3,3'-dihexyloxacarbocyanine iodide and N-[4,4-difluoro-(5,7-dimethyl-BODIPY)-1-pentanoyl]-D-erythro-sphin gosine (Molecular Probes, Eugene, OR). As a result, the singlet oxygen-mediated photodynamic activity of TP induces an effective inactivation of the acyl CoA:cholesterol-O-acyltransferase, a sensitive marker of ER membrane integrity and alterations of the nuclear membrane. In vivo, with the EMT-6 mouse tumor model, an exceptional effectiveness is also observed as compared to that of PII and other second generation photosensitizers of the pheophorbide class, which are themselves much more potent than PII. The outstanding PDT activity of TP observed in vivo may be due to its unique biodistribution properties, in particular much less extraction by the liver, resulting in a higher delivery to other tissues, including tumor.
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PMID:Tolyporphin: a natural product from cyanobacteria with potent photosensitizing activity against tumor cells in vitro and in vivo. 972 63

Photofrin II is a photosensitizer frequently applied in photodynamic therapy. Light-induced tumor cell inactivation observed in the presence of this substance has been suggested to start with modifications at the level of cellular membranes. In the present study electrophysiological techniques are applied in order to investigate the action of photofrin II on functional properties of the plasma membrane of opossum kidney (OK) cells (as an epithelial model system) and of fibroblasts. Illumination of the cells in the presence of photofrin II (or Zn-phthalocyanine) leads to comparatively fast depolarization of the membrane potential. It is caused by a strong change of the membrane conductance which proceeds in two phases. Both phases contribute to a loss of ion selectivity of the plasma membrane between K+ and Na+. In the first phase, specific pathways for K+, which determine the resting potential under physiological conditions, are inactivated. The second phase is distinguished by a marked increase of a nonselective conductance. The increase of the latter - after light-induced initiation - continues in the dark. The conclusions are derived from light-induced, time-dependent changes of the membrane conductance and of the shape of the current-voltage relationship detected under different experimental conditions.
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PMID:Photofrin II sensitized modifications of ion transport across the plasma membrane of an epithelial cell line: I. Electrical measurements at the whole-cell level. 984 91

The sonodynamically induced antitumor effect of Photofrin II (PF), was evaluated in mice bearing colon 26 carcinoma. In order to find the optimum timing for ultrasonic exposure after the administration of PF, the PF concentrations in the plasma, skin, muscle, and tumor were measured. The antitumor effect was estimated by measuring the tumor size. Since the highest concentration of PF in the tumor was observed 24 h after administration, an ultrasonic exposure timing of 24 h after the intravenous administration of PF was chosen. When used alone, ultrasound showed a slight antitumor effect, which became increasingly significant as the dose of PF was increased, while use of PF alone showed no significant effect. From these results, it is concluded that PF significantly sensitizes solid tumors to ultrasound, demonstrating a synergistic antitumor effect.
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PMID:Sonodynamically induced antitumor effect of Photofrin II on colon 26 carcinoma. 1104 98

The reactive nature of species derived from oxygen, such as singlet oxygen and hydrogen peroxide, has been exploited in the clinical setting for targeting bacteria, viruses, and tumor cells by photodynamic excitation of a variety of chromophores. This modality, termed photodynamic therapy (PDT), is currently being used to treat some forms of cancer. However, the applicability of conventional PDT is limited due to the absolute dependence on simultaneous exposure of the target to the photoactive compound and light. In 1990, we demonstrated that the need for simultaneous exposure of the biological target to light and photosensitizer could be circumvented by prior exposure (activation) of the sensitizer molecule to light and its subsequent use as any other anti-cancer or anti-viral drug. By dint of the nature of the protocol, this process was termed preactivation. Since then, the generation of biologically active molecules in vitro by preactivation has been validated using a variety of chromophores, such as merocyanine 540, Photofrin II, and naphthalimide. Here we briefly review the role of reactive oxygen species in the photodynamic effect, and provide an explanation for the mechanism of preactivation. We propose that photo-oxidation not only provides a novel means for the generation of biologically active molecules, but could also explain, at least in part the mechanism of conventional PDT. It is likely that the light-dependent breakdown of the chromophore to generate novel active compounds, in addition to reactive oxygen species, also contributes to the photodynamic damage observed on simultaneous exposure of the chromophore and target tissue to light during PDT.-Pervaiz, S. Reactive oxygen-dependent production of novel photochemotherapeutic agents.
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PMID:Reactive oxygen-dependent production of novel photochemotherapeutic agents. 1125 79

In this study we set out to investigate the photodynamic efficacy of hypericin (Hyp), three other photosensitizers and 5-aminolevulinic acid-induced protoporphyrin IX in their ability to block the growth of rather aggressive tumor - Ehrlich ascites tumor in mice. Hypericin was found to exhibit the highest tumor growth inhibiting activity in treating Ehrlich ascites tumor by photodynamic therapy. The different photosensitizers were ranked as follows: Hypericin > hematoporphyrin dimethyl ether > Photofrin II > meso-tetra-(para-sulfophenyl) porphin > 5-aminolevulinic acid. Of importance, just after Hyp-based photodynamic therapy 75% of mice survived a 4-month period, and no recurrence of tumor within this period was detected in 25% of the treated mice. The clear cut correlation observed between tumor dye concentration in the tumor cells and efficiency of photodynamic therapy, supports the idea that the intracellular accumulation of the photosensitizer is one of the most important factors in determining the benefit of photodynamic therapy. Hence, the accumulation of the photosensitizer in the tumor cells should be considered as one of the prognostic factors for the determination of the therapeutic outcome.
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PMID:Hypericin as novel and promising photodynamic therapy tool: studies on intracellular accumulation capacity and growth inhibition efficiency. 1287 23

The biological effects of radiation affect both neoplastic and normal tissues. The nature and extent of such effects, however, depend on selected biological parameters (e.g., oxygen supply, cell cycle) and can be modified by chemical agents such as radiosensitizers, radioprotectors and chemotherapeutic agents. A precise control of the mode of action of the radiation is important in order to achieve the maximum effect on tumor tissue, while minimizing the effect on normal tissues. Most of the known and routinely used radiosensitizers are neither selective nor tumor specific. This article reviews a new selective and specific modality that increases the sensitivity of solid tumor tissue, especially of radio resistant, hypoxic tumor cells, to radiation. This modality is currently under early clinical evaluation and encompasses the application of Photofrin II, which is already used as a photosensitizer in photodynamic therapy (PDT) at predetermined times prior to irradiation.
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PMID:Porphyrins as radiosensitizing agents for solid neoplasms. 1452 13


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