Howard Shapiro

Improvement of Tumor Response by Manipulation of Tumor Oxygenation During Photodynamic Therapy

Abstract Photodynamic therapy (PDT) requires molecular oxygen during light irradiation to generate reactive oxygen species. Tumor hypoxia, either preexisting or induced by PDT, can severely hamper the effectiveness of PDT. Lowering the light irradiation dose rate or fractionating a light dose may improve cell kill of PDT-induced hypoxic cells but will have no effect on preexisting hypoxic cells. In this study hyperoxygenation technique was used during PDT to overcome hypoxia. C3H mice with transplanted mammary carcinoma tumors were injected with 12.5 mg/kg Photofrin® and irradiated with 630 nm laser light 24 h later. Tumor oxygenation was manipulated by subjecting the animals to 3 atp (atmospheric pressure) hyperbaric oxygen or normobaric oxygen during PDT light irradiation. The results show a significant improvement in tumor response when PDT was delivered during hyperoxygenation. With hyperoxygenation up to 80% of treated tumors showed no regrowth after 60 days. In comparison, when animals breathed room air, only 20% of treated tumors did not regrow. To explore the effect of hyperoxygenation on tumor oxygenation, tumor partial oxygen pressure was measured with microelectrodes positioned in preexisting hypoxic regions before and during the PDT. The results show that hyperoxygenation may oxygenate preexisting hypoxic cells and compensate for oxygen depletion induced by PDT light irradiation. In conclusion, hyperoxygenation may provide effective ways to improve PDT efficiency by oxygenating both preexisting and treatment-induced cell hypoxia.

Hyperoxygenation enhances the tumor cell killing of photofrin-mediated photodynamic therapy.

Abstract Tumor hypoxia, either preexisting or as a result of oxygen depletion during photodynamic therapy (PDT) light irradiation, can significantly reduce the effectiveness of PDT-induced cell killing. To overcome tumor hypoxia and improve tumor cell killing, we propose using supplemental hyperoxygenation during Photofrin-PDT. The mechanism for the tumor cure enhancement of the hyperoxygenation–PDT combination is investigated using an in vivo–in vitro technique. A hypoxic tumor model was established by implanting mammary adenocarcinoma in the hind legs of mice. Light irradiation (200 J/cm2 at either 75 or 150 mW/cm2), under various oxygen supplemental conditions (room air, carbogen, 100% normobaric or hyperbaric oxygen), was delivered to animals that received 12.5 mg/kg Photofrin 24 h before light irradiation. Tumors were harvested at various time points after PDT and grown in vitro for colony formation analysis. Treated tumors were also analyzed histologically. The results show that when PDT is combined with hyperoxygenation, the hypoxic condition could be improved and the cell killing rate at various time points after PDT could be significantly enhanced over that without hyperoxygenation, suggesting an enhanced direct and indirect cell killing associated with high-concentration oxygen breathing. This study further confirms our earlier observation that when a PDT treatment is combined with hyperoxygenation it can be more effective in controlling hypoxic tumors.

Effects of Pd-bacteriopheophorbide (TOOKAD)-Mediated Photodynamic Therapy on Canine Prostate Pretreated with Ionizing Radiation

Abstract Huang, Z., Chen, Q., Trncic, N., LaRue, S. M., Brun, P., Wilson, B. C., Shapiro, H. and Hetzel, F. W. Effects of Pd-bacteriopheophorbide (TOOKAD)-Mediated Photodynamic Therapy on Canine Prostate Pretreated with Ionizing Radiation. Radiat. Res. 161, 723–731 (2004). The aim of this study was to evaluate the effects of photodynamic therapy (PDT) using a novel palladium bacteriopherophorbide photosensitizer TOOKAD (WST09) on canine prostate that had been pretreated with ionizing radiation. To produce a physiological and anatomical environment in canine prostate similar to that in patients for whom radiotherapy has failed, canine prostates (n = 4) were exposed to ionizing radiation (54 Gy) 5 to 6 months prior to interstitial TOOKAD-mediated PDT. Light irradiation (763 nm, 50–200 J/cm at 150 mW/cm from a 1-cm cylindrical diffusing fiber) was delivered during intravenous infusion of TOOKAD at 2 mg/kg over 10 min. Interstitial measurements of tissue oxygen profile (pO2) and of local light fluence rate were also measured. The prostates were harvested for histological examination 1 week after PDT. The baseline pO2 of preirradiated prostate was in the range 10–44 mmHg. The changes in relative light fluence rate during PDT ranged from 12 to 43%. The acute lesions were characterized by hemorrhagic necrosis, clearly distinguishable from the radiotherapy-induced pre-existing fibrosis. The lesion size was correlated with light fluence and comparable to that in unirradiated prostate treated with a similar TOOKAD-PDT protocol. There was no noticeable damage to the urethra, bladder or adjacent colon. The preliminary results obtained from a small number of animals indicate that TOOKAD-PDT can effectively ablate prostate pretreated with ionizing radiation, and so it may provide an alternative modality for those prostate cancer patients for whom radiotherapy has failed.

Sequencing of combined hyperthermia and photodynamic therapy.

Photodynamic therapy (PDT) and hyperthermia are two alternative tumor treatment modalities currently being investigated in clinical trials. It has been suggested that, due to the differences in cell-killing mechanisms, synergetic tumor responses may be achieved if the two modalities are combined in appropriate sequences. This hypothesis is tested in the current study by delivering graded PDT doses during a transient tumor reoxygenation period after a hyperthermia treatment, or delivering graded hyperthermia doses when the tumor becomes acidic and hypoxic after a PDT treatment. The results indicate that the latter combination sequence has a profound effect on tumor response. While treating the tumors with PDT followed by hyperthermia evokes a synergetic tumor response, reversing the sequence results only in an additive effect. Possible mechanisms associated with tissue oxygenation are discussed.

Low albumin level in the emergency department: a potential independent predictor of delayed mortality in blunt trauma.

Albumin is an abundant plasma protein with multiple physiologic functions, and low serum albumin levels have been associated with increased mortality in hospitalized patients. In a retrospective matched-pair study, we investigated whether emergency department (ED) albumin levels predict delayed mortality for patients initially stabilized after blunt trauma. Fifty-one hospital non-survivors who died more than 24 h after admission to a trauma center ED were matched by Injury Severity Score, type and location of injury, age, and gender with 51 survivors. All patients had serum albumin levels determined upon arrival in the ED. The non-survivors had a significantly lower admission albumin of 3.1 g/dL compared to 3.5 g/dL for survivors. Patients with albumin levels < 3.4 g/dL were 2.5 times more likely to die compared to patients with normal albumin levels. These preliminary results indicate that initial hypoalbuminemia in blunt trauma patients is an independent predictor of delayed mortality, suggesting that these patients require continued clinical vigilance and an aggressive search for evolving complications.

Oxygen effect of photodynamic therapy

Photodynamic therapy (PDT) is rapidly becoming an accepted therapeutic modality for the treatment of some types of malignant tumors. An important feature of PDT is its absolute dependence on molecular oxygen during light irradiation.Hypoxic tumor cells, either pre-existing or photochemically depleted of their oxygen supply during light irradiation, are resistant to PDT treatment, and contribute to treatment failures. We hypothesize that tumor response to PDT can be improved by combining PDT with Hyper-oxygenation, which may simultaneously compensate for the oxygen depletion by PDT and increase oxygenation of the pre-existing hypoxic cells. The doubling time of mammary carcinoma tumors, implanted in either leg or flank of C3H mice, was evaluated after PDT treatment with/without addition of hyperoxygenation. By adding hyperoxygenation to a non- curative PDT dose, a further delay in the tumor regrowth was observed. For a sub-curative does PDT treatment, the addition of hyperoxygenation resulted in an increase in tumor cure. The results indicate that tumor response can be improved by combining PDT and hyperoxygenation.

Hyperoxygenation enhances the direct tumor cell killing of photofrin-mediated photodynamic therapy

Tumor hypoxia, either pre-existing or as a result of oxygen bleaching during Photodynamic Therapy (PDT) light irradiation, can significantly reduce the effectiveness of PDT induced cell killing. To overcome the effect of tumor hypoxia and improve tumor cell killing, we propose using supplemental hyperoxygenation during Photofrin PDT. Our previous study has demonstrated that, in an in vivo model, tumor control can be improved by normobaric or hyperbaric 100% oxygen supply. The mechanism for the tumor cure enhancement of the hyperoxygenation-PDT combined therapy is investigated in this study by using an in vivo/in vitro technique. A hypoxic tumor model was established by implanting mammary adenocarcinoma (MCA) in hind legs of C3H mice. Light irradiation (200 J/cm2 at either 75 or 150 mW/cm2), under various oxygen supplemental conditions (room air or carbogen or 100% normobaric or hyperbaric 100% oxygen), was delivered through an optical fiber with a microlens to animals who received 12.5 mg/kg Photofrin 24 hours prior to light irradiation. Tumors treated with PDT were harvested and grown in vitro for colony formation analysis. Treated tumors were also analyzed histologically. The results show that, when combined with hyperoxygenation, the cell killing rate immediately after a PDT treatment is significantly improved over that treated without hyperoxygenation, suggesting an enhanced direct cell killing. This study further confirms our earlier observation that when a PDT treatment is combined with hyperoxygenation, it can be more effective in controlling hypoxic tumors. H&E stain revealed that PDT induced tumor necrosis and hemorrhage. In conclusion, by using an in vivo/in vitro assay, we have shown that PDT combined with hyper-oxygenation can enhance direct cell killing and improve tumor cure.

Improvement of tumor response to photodynamic therapy by manipulation of tumor oxygenation in an in-vivo model system

Photodynamic therapy (PDT) requires molecular oxygen during light irradiation in order to generate reactive oxygen species. Tumor hypoxia, either pre-existing or induced by PDT, can severely hamper the effectiveness of PDT treatment. Lowering the light irradiation dose rate or fractionating a light dose may improve cell kill of PDT induced hypoxic cells, but will have no effect on pre-existing hypoxic cells. In this study, hyper-oxygenation technique was used during PDT to overcome hypoxia. C3H mice with transplanted mammary carcinoma tumors were injected with 12.5 mg/kg Photofrin and irradiated with 630 nm laser light 24 hours later. Tumor oxygenation was manipulated by subjecting the animals to 3 atp hyperbaric oxygen or normobaric oxygen during PDT light irradiation. The results show a significant improvement in tumor response when PDT was delivered during hyper-oxygenation. With hyper-oxygenation, up to 80% of treated tumors showed no re-growth after 60 days. In comparison, only 20% of tumors treated while animals breathed room air did not re-grow. To explore the effect of hyper-oxygenation on tumor oxygenation, tumor pO2 was measured with microelectrodes positioned in pre-existing hypoxic regions before and during the PDT. The results show that hyper-oxygenation may oxygenate pre-existing hypoxic cells and compensate for oxygen depletion induced by PDT light irradiation. In conclusion, hyper-oxygenation may provide effective ways to improve PDT treatment efficiency by oxygenating both pre-existing and treatment induced cell hypoxia.