Photodynamic Therapy Systemic Toxicity in Mice ...

Systemic Toxicity in Mice Induced by Localized Porphyrin Photodynamic Therapy Angela Ferrario and Charles J. Gomer Cancer Res 1990;50:539-543. Published online February 1, 1990.

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[CANCER RESEARCH 50, 539-543. February 1, 1990]

Systemic Toxicity in Mice Induced by Localized Porphyrin Photodynamic Therapy1 Angela Ferrarlo and Charles J. Corner2 Clayton Ocular Oncology Center [A. F., C. J. G.Â¡,Children! Hospital of Los Angeles, and Departments of Pediatrics fC. J. GJ and Radiation Oncology [C. J. G.J, University of Southern California School of Medicine, Los Angeles, California 90027

ABSTRACT

response. This observation was unexpected in that: (a) the PDT doses that were used (10 mg/kg Photofrin II, 200-500 J/cm2)

An unexpected high level of acute lethality has been documented following Photofrin H-mediated photodynamic therapy (PDT) treatments which were localized to the hind leg of normal and tumor-bearing mice. Doses of PDT which induced lethality (10 mg/kg Photofrin II, 200-500 J/cm2) were in the range of doses required to obtain murine tumor cures. The percentage of lethality was proportional to the total light dose but was inversely proportional to the dose rate of delivered light. Comparable levels of acute toxicity were observed in four pigmented mouse strains (C57BL/6J, C3H/HeJ, DBA/1, and DBA/2) and in two albino mouse strains (BALB/c and Swiss Webster). Decreased sensitivity to PDTinduced lethality was observed in two pigmented mouse strains (B,,,D,/ OSN and Bi0D2/NSN). The administration of warfarin, aspirin, indomethacin, or antihistamine had significant protective effects in terms of decreasing PDT-induced lethality. However, injection of cobra venom factor (to deplete C3 and C5 of the complement system) did not alter the lethality mediated by PDT. Histological profiles obtained 24 h following PDT demonstrated vascular congestion in the liver, kidney, lung, and spleen. Significant decreases in removable blood volume, core tempera ture, and spleen weight were also observed within 24 h of localized PDT treatment. These results indicate that PDT-induced lethality is consistent with a traumatic shock syndrome and suggest that endogenous vasoactive mediators of shock such as prostaglandins, thromboxanes, and histamine are associated with the lethality induced by localized PDT in mice.

were comparatively low and were in the range of doses required to produce tumor cures in mice (9); and (b) the area of light treatment was specifically localized to the hind leg in order to eliminate light exposure to all vital organs and structures. Lethal toxicity induced by various photosensitizers has been documented as early as 1911 (reviewed in Ref. 10), and systemic toxicity has been reported following whole body and abdominal light exposure of porphyrin PDT in mice (11). In this report, we describe the clinical, hematological, and histopathological responses of acute toxicity induced by Photofrin II-mediated PDT as a function of various treatment parameters and mouse strains. MATERIALS

INTRODUCTION Photodynamic therapy is the generalized term for the treat ment of solid malignancies by using tissue-penetrating visible light following the administration of a tumor localizing photosensitizer such as hematoporphyrin derivative or its purified component Photofrin II (1, 2). The combination of drug uptake in malignant tissue and selective delivery of laser-generated light provides for an effective therapy with efficient tumor cytotoxicity and minimal normal tissue damage (3, 4). The photochemical generation of singlet oxygen and possibly other reactive oxygen species is responsible for the cytotoxicity in duced by PDT3 (5, 6). Information regarding the biochemical, cellular, and preclinical parameters associated with PDT has recently been reviewed (6, 7). The clinical efficacy of PDT is currently being evaluated in Phase III trials for obstructive and partially obstructive carcinoma of the bronchus and esophagus as well as for transitional cell carcinoma of the bladder (8). In addition, PDT is being used on a limited basis to treat malig nancies of the head and neck, skin, cervix, eye, and brain (2, 8). Recently, we encountered high levels of acute lethality in mice treated with Photofrin II-mediated PDT during experi ments designed to evaluate effects of light dose rate on tumor Received 8/21/89; revised 10/24/89; accepted 10/27/89 The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked advertisement in accordance with 18 U.S.C. Section 1734 solely to indicate this fact. 1This investigation was performed in conjunction with the Clayton Foundation for Research and was supported in part by USPHS Grants R37-CA-31230 and R01-CA-44733 awarded by the National Cancer Institute, Department of Health and Human Resources. Presented in part at the European Photobiology Meeting, Padova, Italy, September 6-10, 1987, and at the SPIE Conference on Photody namic Therapy Mechanisms, January 19-20, 1989, Los Angeles, CA. 2To whom requests for reprints should be addressed, at Childrens Hospital of Los Angeles, 4650 Sunset Boulevard, Los Angeles, CA 90027. 3 The abbreviation used is: PDT, photodynamic therapy.

AND METHODS

Drugs. Photofrin II (dihematoporphrin-ether) was obtained from Photomedica, Inc., Raritan, NJ, as a sterile solution at a concentration of 2.5 mg/ml. The drug was diluted with saline to obtain a working concentration of I mg/ml. A 10-mg/kg dose of Photofrin II was administered by i.p. injection 24 h prior to localized laser irradiation in PDT experiments. Sodium warfarin (Coumadin, DuPont Pharma ceuticals, Inc., Wilmington, DE), indomethacin (Indocin, Merck Sharp & Dohme, Inc., West Point, PA), and aspirin (acetylsalicyclic acid, Sigma Chemical Co., St. Louis, MO) were administered in the drinking water of test mice. The concentration of warfarin was 5 mg/liter and mice were administered the drug from day â€”¿3 to day â€”¿1 prior to PDT light treatment (12, 13). Indomethacin was dissolved in 95% ethanol at a concentration of 10 mg/ml, and was then added to the drinking water for a final concentration of 20 mg/liter in 0.25% ethanol (14, 15). Indomethacin was administered to test mice from day -4 to day +2. Aspirin was added to the drinking water at a concentration of 625 mg/liter and was administered to mice from day â€”¿4 to day +2 (16). The antihistamine pyrilamine malÃ©ate(Histavet-P, Schering Corp., Kenilworth, NJ) was delivered to test mice by i.m. injection. A 0.5-mg/ kg dose of antihistamine was administered immediately following PDT to the hind leg not involved in the PDT treatment (17). Cobra venom factor was obtained from Cordis Laboratory, Inc., Miami, FL, as a lyophilized powder. The drug was dissolved in water and administered by i.v. injection at a dose of 250 units/kg on day -2 (18). Animals. Eight strains of female mice (8 to 12 weeks old) were utilized in various experiments. Pigmented mice included: C57BL/6J, C3H/HeJ (endotoxin resistant), DBA/U (C5 proficient), DBA/2J (C5 deficient), B10D2/OSN (C5 deficient) and B10D2/NSN (C5 proficient). Albino mouse strains used in this study included Swiss Webster and BALB/c. All mice were purchased from The Jackson Laboratory, Bar Harbor, ME. Tumor Models. Pigmented and nonpigmented B16 melanomas were used during initial experiments in this study (9). The tumors were originally obtained from the NIH Tumor Repository and they were maintained by serial passage in the hind flank of C57BL/6J mice. A 1mm3 piece of tumor was transplanted s.c. via trochar injection in the shaved hind right leg of mice. Tumor volumes were determined 3 times/ week and mice with tumors measuring 25-35 mm3 were entered into PDT experiments. Photodynamic Therapy Protocols. An i.p. injection of Photofrin II (10 mg/kg) was administered 24 h prior to light treatment (19). A 1cm diameter spot localized to the hind right leg was used as the treatment area for all light exposures. Red light at 630 nm was gener ated by an argon pumped dye laser (Spectra-Physics, Inc., Mountain-

539


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SYSTEMIC TOXICITV

view, Ã‡A).A 400-Mtn diameter quartz fiber was interfaced to the output of the dye laser and a microlens was attached to the distal tip of the fiber for uniform light delivery. The wavelength of delivered light was documented with a spectroscope (Cooper Lasersonics, Inc., Santa Clara, CA) and a power meter (Coherent Radiation, Palo Alto, CA) was used to measure light intensity. All mice undergoing PDT were restrained in holders without anesthesia. HistolÃ³gica!and Hematological Evaluation. Acute histological speci mens were obtained for C57BL/6J mice by sacrificing the animals 24 h following PDT (10 mg/kg Photofrin II, 150 mW/cm2, 500 J/cm2).

to the fact that the first group of treated mice had tumors. The percentage of lethality described in Table 2 is documented as a function of both total light dose and light dose rate. The percentage of lethality was again observed to be directly pro portional to the total light dose and inversely proportional to the dose rate of delivered light. Light exposure without prior administration of Photofrin II did not induce any lethality even though local temperature rises of 6Â°C(150 mW/cm2) and 21Â°C (600 mW/cm2) were produced at the site of light exposure.

Samples from the liver, spleen, lung, kidney, and skin were obtained and placed in 10% buffered formalin. The specimens were embedded in paraffin, sectioned, and processed by using hematoxylin-eosin stain ing or periodic acid-Schiff staining. An electronic blood cell counter (ELT-8/DS, Orthodiagnostics Sys tems, Inc.) was used to obtain quantitative values for hematocrits, platelets, and WBC from C57BL/6J mice treated with PDT (10 mg/ kg, 500 J/cm2, 150 mW/cm2). Blood samples were collected by heart puncture at the completion of the PDT light treatment (0 h) and at 1, 2, and 4 h, and 1, 3, 7, and 14 days. Control mice received either saline or Photofrin II (without light). Statistical Analysis. The x2 test was used to evaluate mouse lethality responses and the Student's t test was used to evaluate the mean values

The effects of localized PDT on different strains of mice are documented in Table 3. The PDT parameters (10 mg/kg, 150 mW/cnr, 500 J/cm2) were comparable to dose parameters

for hematological determinations.

RESULTS The percentage of acute lethality induced by localized PDT in C57BL/6J mice with either pigmented or nonpigmented B16 melanomas is shown in Table 1. PDT-induced lethality is documented as a function of both total light dose (200-500 J/ cm2) and dose rate of delivered light (150 or 600 mW/cm2). In all cases, the site of light exposure covered the tumor and was confined to a 1-cm-diameter spot on the hind right leg. An increase in total light dose corresponded to a concomitant increase in the percentage of PDT-induced deaths for both mouse-tumor models. However, increasing the dose rate of delivered light produced a decrease in lethality for mice treated at equal total light doses. Acute lethality in normal C57BL/6J mice following localized PDT directed to the hind leg is summarized in Table 2. These experiments were performed to determine whether the high degree of PDT-mediated lethality described in Table 1 was due

C57BL/6J

Table 3 PDT-induced lethality as a function of mouse strain'

of mice strainC57BL/6C3H/HeJ*B,0D2/OSNCB.oDj/NSN''DBA/2JCDBA/U''BALB/cfSwiss Mouse treated261020209101010%of lethality76.9270.0020.000.0077.7880.0

Webster'No. * The PDT treatment consisted of a 10 mg/kg i.p. injection of Photofrin II

% of lethality PDT dose (J/cm2)

reduction in lethality was approximately 50%. These drugs (which function by inhibiting cyclooxygenase, histamine, and coagulation) were administered by using previously reported protocols (12-18). Cobra venom factor (which depletes C3 and C5 of the complement system) did not alter the lethality induced by PDT. Experiments described in Tables 3 and 4 were per formed approximately 3 months apart and therefore separate groups of positive controls (PDT, 500 J/cm2, 150 mW/cm2) were used. Histological profiles obtained from PDT-treated

Table 1 Lethality in C57BL/6J mice following PDT localized to the hind legfor the treatment ofB16 melanoma"

Nonpigmented melanoma 150mW/cm2 600 mW/cm2

required to achieve cures in most mouse tumor models. Similar levels of PDT-induced lethality were observed in all mouse strains except for the B10D2/OSN and B,0D2/NSN strains, which exhibited significantly decreased lethality following PDT. Table 4 describes the effect of various pharmacological agents on the lethality induced by PDT in normal C57BL/6J mice. The combination of PDT and either warfarin, aspirin, indomethacin, or antihistamine produced a protective effect in terms of decreased lethality and the protection was observed at all light doses analyzed (300-500 J/cm2) and in each case the

administered 24 h prior to localized hind leg exposure to 630 nm light at a dose of 500 J/cm2 and delivered at a light dose rate of 150 mW/cm2. Lethality was observed within 2 days of PDT treatment. * Endotoxin resistant. ' C5 deficient. d C5 proficient. ' Albino.

Pigmented melanoma 150 mW/cm2 600 mW/cm2

20030040050016.67(12)*52.38(21)54.54

(22)76.74 (43)21.43(14)23.08(13)16.67(12)54.54 (22)0(10)33.33(15)41.18(17)59.26 (27)0(12)0(11)9.10(11)42.86(21) Table 4 " Photofrin II was administered as an i.p. injection (10 mg/kg) 24 h prior to Lethality in C57BL/6J mice treated with exogenous pharmacological agents" light treatment. Lethality was observed within 48 h of PDT treatment. * Numbers in parentheses, number of mice. % of lethality treatmentPDT Drug

Table 2 Lethality induced by PDT in normal C5 7BL/6 mice as a function of light dose rate' PDT dose (J/cm2)300

J/cm244.44

J/cm261.00(31) J/cm288.89

(36)* alone (54) PDT + warfarin 30.00 (20) 50.00 (20) 40.00 (20) PDT + indomethacin 5.00 (20) 35.00 (20) 40.00 (20) PDT + aspirin 20.00 (20) 30.00 (20) 40.00 (20) PDT + antihistamine 15.62(32) 15.00(20) 35.00 (20) NDC400 PDT + cobra venom factor300 ND500 100.00(10) Â°The PDT treatment consisted of a 10 mg/kg i.p. injection of Photofrin II administered 24 h prior to localized hind leg exposure to 630 nm light (300-500 J/cm2) delivered at a dose rate of 150 mW/cm2. Doses and administration schedules of the various exogenous drugs are described in "Materials and Meth ods." * Numbers in parentheses, number of mice. c ND, not determined.

lethality150mW/cm212.00(25)* of mW/cm20(12)

40.48 (42) 12.00(25) 64.00 (25) 12.00(25) 69.75 (32) 47.37(19) 600 600 (light alone)% 0(5)600 0(5) a Photofrin II was administered as a 10 mg/kg i.p. injection 24 h prior to light treatment. Lethality was observed within 2 days of PDT treatment. * Numbers in parentheses, number of mice. 400500

540


PDT-INDUCED

SYSTEMIC TOXICITY

mice were consistent with responses seen during a systemic shock reaction (20). Vascular congestion was present in the liver, kidney, lung, and spleen 24 h following PDT (data not shown). Hematological profiles (WBC, platelets, and hematocrit) in C57BL/6J mice following PDT are shown in Figs. 1-3 for time periods ranging from l h to 14 days following treat ment. Fig. 1 shows that the WBC initially increased from a base-line level of 10,000/mm3 to over 40,000/mm3 during the first 4 h following PDT. The WBC values were still over 30,000/ mm3 at 24 h posttreatment. However, by 3 days posttreatment the WBC levels had decreased to 2,900/mm3 which was signif icantly below control levels (P < 0.01). Animals surviving the PDT treatment had WBC levels which returned to control values by 7 days posttreatment. Platelet levels in PDT-treated mice were lower than control values for the initial 24 h following treatment as shown in Fig. 2. The platelet count increased to levels significantly higher than control levels (P < 0.01) at 7 and 14 days posttreatment. Hematocrit levels are shown in Fig.

85 -i

85 75 65 -

75 -

55 -

(E O O

45 -' 35

65 -

012345 UJ

Z I-

HOURS AFTER TREATMENT

z LU o oc Ul o.

55 -

45

35 1 5

DAYS AFTER TREATMENT

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E E

Fig. 3. Hematocrit levels in C57BL/6J mice as a function of time after treatment with PDT (10 mg/kg Photofrin II. 500 J/cm2, 150 mW/cm2) (El), Photofrin II without light (*), or normal saline (D). Points, mean for 10 mice; bars, SE.

o o.

Table 5 Removable blood volume, core body temperature, spleen weight, and liver weight in normal C57BL/6J mice determined 24 h following localized leg PDTÂ°

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m M


Treatment conditionControl*

volume (ml)0.63

temperature CO35.6

wt (mg)76.6

wt (g)1.05

O Photofrin II*

o m

76.4 1.06 0.65 35.5 PDTBlood 0.18Core 25.8Spleen 48.0Liver 0.83 Â°The PDT treatment consisted of a 10 mg/kg i.p. injection of Photofrin II administered 24 h prior to a 500-J/cm2 dose of 630 nm light localized to the hind leg. Data points are the average values for 5 mice. * Controls received an i.p. injection of saline and the Photofrin II group received a 10-mg/kg i.p. injection of the drug (without light treatment).

10

1O

DAYS AFTER TREATMENT Fig. 1. WBC Â¡nC57BL/6J mice as a function of time after treatment with PDT ( 10 mg/kg Photofrin II, 500 J/cm2,150 mW/cm2) (ET),Photofrin II without light (*), or normal saline (D). Points, mean for 10 mice; bars, SE.

1600-, E E 3 O

1600 -

1400 1200 1400 -

1000 800-

I 1200 M â€¢¿o

400

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C

ni m

600-

3 O

1000

Cfl

800

3 and values were similar for control and PDT-treated mice at all time points analyzed. The removable blood volume, spleen and liver weights, and core body temperature in C57BL/6J mice at 24 h following PDT (10 mg/kg, 150 mW/cm2, 500 J/cm2) are shown in Table 5. The removable blood volume (using heart puncture) was 0.63-0.65 ml/mouse for controls and only 0.18 ml for PDTtreated mice. Spleen and liver weights were also decreased in PDT-treated mice. Spleen weights averaged 0.076 g for controls and 0.048 g following PDT, while liver weights averaged 1.0481.058 g for controls and 0.83 g for PDT-treated mice. A drop in core body temperature from a control average of 35Â°Cdown to 25.8Â°Cwas also observed 24 h following PDT.


DISCUSSION Results from this study demonstrate that systemic toxicity in the form of acute lethality is induced following Photofrin IImediated PDT in both normal and tumor-bearing mice. The phenomenon of acute toxicity (lethality) in experimental ani mals following photosensitizer-initiated photodynamic action 400 has been reported previously (10, 11), but there have not been any prior reports on lethality induced by porphyrin PDT asso ciated with localized tumor treatments. The PDT dose response DAYS AFTER TREATMENT experiments (combining various pharmacological agents), to Fig. 2. Platelet values in C57BL/6J mice as a function of time after treatment gether with the histopathological observations and hematologwith PDT (10 mg/kg Photofrin II, 500 J/cm2, 150 mW/cm2) (H), Photofrin II without light (4), or normal saline (O). Points, mean for 10 mice; bars, SE. ical responses obtained in this study, strongly suggest that 541

Ul


PDT-INDUCED

SYSTEMIC TOXICITY

localized PDT elicits systemic toxicity in the form of a trau matic shock syndrome (20). Traumatic shock can be produced by tissue injury which in turn leads to inadequate peripheral perfusion. Despite a wide variety of inducers of shock, the final pathway appears to be circulatory collapse (20). The etiology of irreversible shock includes induction of significant levels of ischemia or hypoxemia, the release of prostaglandins and kinins, as well as production of large amounts of cell necrosis. Indomethacin and aspirin are antiinflammatory agents which can inhibit cyclooxygenase and therefore decrease prostaglandin and thromboxane synthesis. Warfarin acts as an anticoag ulant and antihistamine actions are primarily related to antag onizing the effects of histamine. Each of these agents can reduce the action of endogenous mediators of microcirculatory disrup tion which is characteristic of traumatic shock. Our observa tions are therefore in agreement with previous reports describ ing the generation of eicosanoids and antihistamine following porphyrin photosensitization (17, 21). A separate study has also shown that inhibitors of cyclooxygenase (indomethacin and aspirin) can significantly reduce the vasoconstriction and vascular stasis induced by PDT (22). It is significant to note that the doses of PDT used in the current study were comparable to those used previously in tumor cure experiments (20). Equally important is the fact that the site of PDT treatment in the current set of experiments was specifically limited to the hind leg in order to avoid illumination of all vital organs. Interestingly, the lethality observed in mice following PDT is not unique to Photofrin II. We have observed comparable effects with chlorin photosensitizers4 and other

pharmacokinetics in the B,oD2 mouse strains which could influ ence the degree of systemic toxicity observed following PDT but this has not yet been evaluated. It is also unknown whether the B,0D2 mouse strains are inherently more resistant to trau matic shock than the other mouse strains used in this study. The inverse relationship between PDT-induced lethality and the dose rate of delivered light was unexpected but may be associated with physical and/or physiological properties of the treatment. The highest light dose rate (600 mW/cnr) produced a 21Â°Clocalized temperature rise 1 mm below the surface at the treatment site. This thermal condition could have induced a complete and localized vascular closure with a concomitant decrease in the release to prostaglandins or other endogenous toxic substances. In addition, the volume of blood flowing through the PDT treatment area would be 4 times lower for exposures performed at 600 mW/cm2 compared to those per formed at 150 mW/cm2. Nevertheless, it is apparent that the addition of local hyperthermia did not potentiate PDT-induced lethality even though heat has been shown to enhance PDTinduced tumor destruction (6, 26). Results from this study indicate that PDT-induced lethality in mice will have to be taken into account when screening new tumor photosensitizers. Quantitative dose response experi ments (using tumor cure as an end point) may be extremely difficult to complete as a consequence of the high level of lethality which may accompany the treatment. In addition, possible systemic factors involved with tumor responses in PDT-treated mice (i.e., ecosonoid and/or cytokin release as well as physiological factors involved with shock induction) may not be relevant in PDT treatment in larger animals or in humans. The positive effects that indomethacin, aspirin, war farin, and antihistamine had on reducing PDT-associated le thality strongly suggest that endogenously produced vasoactive mediators can influence generalized PDT responses. The doses of PDT currently used in larger animals and humans (2) do not elicit any observable systemic toxicity, and therefore it is pos sible that systemic factors associated with PDT in mice will be greatly reduced or eliminated following treatment in larger animals and humans. In summary, the PDT-induced lethality documented in the current study appears to be comparable to a traumatic shock syndrome and is associated only with small animal models. The acute lethality observed in mice does not appear to be clinically relevant but the phenomenon should be taken into account during the in vivo screening of new tumor photosensitizers using mouse models.

investigators have observed lethality following PDT by using phthalocyanines.5 Fortunately, the type of acute systemic shock reaction described in this study has not been observed in humans undergoing clinical PDT. In addition, larger animals (rats and rabbits) treated with the highest doses of Photofrin II-mediated PDT used in the current study did not exhibit any systemic toxic reaction (data not shown). These observations would suggest that the relationship of PDT treatment area to total body area may be an important parameter in the induction of acute lethality. The lethality induced in mice by localized PDT appears to be a generalized phenomenon and not limited to tumor-bearing mice (which may have compromised immune systems) or to any one particular strain of mouse. In our study, similar levels of PDT-induced lethality were observed for pigmented and albino mice as well as for mice with transplanted melanomas. The only exception to the high level of PDT-induced lethalityoccurred in the two Bi0D2 mouse strains. It is currently unclear why these two mouse strains exhibited resistance to PDTinduced lethality. However, the resistance does not appear to be related to complement activation since both C5-proficient and CS-deficient strains of B,0D2 mice were resistant to the toxic effects of PDT. Interestingly, these two strains were produced by an initial cross between C57BL/10 mice and DBA/ 2 mice (23). The C57BL mouse is proficient for C5 while the DBA/2 mouse lacks C5 and yet both C57BL and DBA/2 mice exhibited high levels of PDT-induced lethality. In previous studies, cutaneous phototoxicity was shown to be associated with a decrease in total complement activity and the phototoxic reaction was suppressed in complement-depleted animals (24, 25). In the current study, the administration of cobra venom factor (to deplete C3 and C5) had no effect on PDT lethality in C57BL mice. However, there may be differences in porphyrin

ACKNOWLEDGMENTS We thank Dr. John Spikes for discussions regarding the history of photosensitizer-mediated toxicity.

REFERENCES 1. Comer. C. J. (ed.) Photodynamic therapy. Photochem. Photobiol., 46: 561952. 1987. 2. Dougherty, T. J. Photodynamic therapy (PDT) of malignant tumors. CRC Crit. Rev., 2:83-116. 1984. 3. Gomer, C. J., and Dougherty. T. J. Determination of 3H and 14C hematoporphyrin derivative distribution in malignant and normal tissue. Cancer Res., 39: 146-151. 1979. 4. Wilson. B. C., and Patterson, M. S. The physics of photodynamic therapy. Phys. Med. Biol.. 316: 297-303, 1986. 5. Weishaupt, K. R.. Gomer, C. J.. and Dougherty. T. J. Identification of singlet oxygen as the cytotoxic agent in photoinactivation of a murine tumor. Cancer Res., 36: 2326-2329. 1976. 6. Gomer, C. J., Ferrano, A., Hayashi, N., Szirth. B. C.. and Murphree, A. L. Molecular, cellular and tissue responses following photodynamic therapy.

' Unpublished data. 5J. van Lier, personal communication. 542


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17. Lim, H. W., Young, L., Hagan, M., and Gigli, I. Delayed phase of hematoporphyrin-induced phototoxicity: modulation by complement, leukocytes and antihistamines. J. Invest. Dermatol., 84: 114-117, 1985. 18. Cochrane, C. G., MÃ¼ller-Eberhard, H. J., and Aikin, B. S. Depletion of plasma complement in vivo by a protein of cobra venom: its effect on various immunological reactions. J. Ininnino I.. 705: 55-61, 1970. 19. Gomer, C. J., Ferrano, A., and Murphree, A. L. The effect of localized porphyrin photodynamic therapy on the induction of tumor metastasis. Br. J. Cancer, 56:27-32, 1987. 20. Miller, H. I., and Whidden, S. J. Burns and Trauma. In: Altura et al. (eds.), Handbook of Shock and Trauma, Vol. 1, pp. 413-424. New York: Raven Press, 1983. 21. Lim, H. W. Role of mediators of inflammation in cells on porphyrin induced phototoxicity. SPIE Proc., 1065: 28-33, 1989. 22. Wieman, T. J., and Fingar, V. H. Microvascular effects of photodynamic therapy. SPIE Proc., 1065: 11-27, 1989. 23. Kaliss, N., Bailey, D. W., and Shin, H. S. Histocompatability between the B10D2/n and B10D2/O strains of mice. Transplantation (Baltimore). 14: 523-525, 1972. 24. Lim, H. W., and Gigli, I. Role of complement in porphyrin induced photosensitization. J. Invest. Dermatol., 76: 4-9, 1981. 25. Lim, H. W., Hagan, M., and Gigli, I. Phototoxicity induced by hematoporphyrin derivative in C5-deficient, mast cell deficient and leukopenic mice. Photochem. Photobiol., 44:175-180, 1986. 26. Waldow, S. M., and Dougherty, T. J. Interaction of hyperthermia and photoradiation therapy. RadiÃ¢t.Res., 97: 380-385, 1984.

Lasers Surg. Med., 8: 450-463, 1988. 7. Jori, G., and Spikes, J. D. In: K. C. Smith (ed.), Photobiochemistry of porphyrins. Topics in Photomedicine, pp. 183-318. New York: Plenum Press, 1984. 8. Comer, C. J., Rucker, N.. Ferrano, A., and Wong, S. Properties and appli cations of photodynamic therapy. RadiÃ¢t.Res., 720: 1-18, 1989. 9. Gomer, C. J., Hayashi, N., and Murphree, A. L. The influence of sodium pentobarbital anesthesia on in vivo photodynamic therapy. Photochem. Photobiol., 46: 843-846, 1987. 10. Blum, H. F. Photodynamic Action and Diseases Caused by Light, pp. 103107. New York: Hafner Publishing Co., 1964. 11. Dougherty, T. J. Photosensitizers: therapy and detection of malignant tu mors. Photochem. Photobiol., Â¥5:879-889, 1987. 12. Ryan, J. J. Warfarin treatment of mice bearing autochthonous tumors; effect on spontaneous mÃ©tastases.Science (Wash. DC), 162: 1493-1495, 1968. 13. Brown, J. M. A study of the mechanisms by which anti-coagulation with warfarin inhibits blood-borne mÃ©tastases.Cancer Res., 33:1217-1224, 1973. 14. Fulton. A. M. In vivo effects of indomethacin on the growth of murine mammary tumors. Cancer Res., 44:2416-2420, 1984. 15. Fulton, A. M.. and Heppner, G. H. Relationships of prostaglandin E and natural killer sensitivity to metastatic potential in murine mammary adenocarcinomas. Cancer Res., 45: 4779-4784, 1985. 16. Carmel, R. J., and Brown, J. M. The effect of cyclophosphamide and other drugs on the incidence of pulmonary mÃ©tastasesin mice. Cancer Res., 37: 145-151, 1977.

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