Navigation

Canine Cancer Symptoms

Preclinical Studies in Normal Canine Prostate of a Novel Palladium-Bacteriopheophorbide (WST09) Photosensitizer for Photodynamic Therapy of Prostate Cancer (para)

ABSTRACT

Photodynamic therapy (PDT) uses light to activate a photosensitizer to achieve localized tumor control. In this study, PDT mediated by a second-generation photosensitizer, palladium-bacteriopheophorbide WST09 (Tookad) was investigated as an alternative therapy for prostate cancer. Normal canine prostate was used as the animal model. PDT was performed by irradiating the surgically exposed prostate superficially or interstitially at 763 nm to different total fluences (100 or 200 J/cm^sup 2^; 50, 100 or 200 J/cm) at 5 or 15 min after intravenous administration of the drug (2 mg/kg). Areas on the bladder and colon were also irradiated. The local light fluence rate and temperature were monitored by interstitial probes in the prostate. All animals recovered well, without urethral complications. During the 1 week to 3 month posttreatment period, the prostates were harvested for histopathological examination. The PDT-induced lesions showed uniform hemorrhagic necrosis and atrophy, were well delineated from the adjacent normal tissue and increased linearly in diameter with the logarithm of the delivered light fluence. A maximum PDT-induced lesion size of over 3 cm diameter could be achieved with a single interstitial treatment. There was no damage to the bladder or rectum caused by scattered light from the prostate. The bladder and rectum were also directly irradiated with PDT. At 80 J/cm^sup 2^, a full-depth necrosis was observed but resulted in no perforation. At 40 J/cm2, PDT produced minimal damage to the bladder or rectum. On the basis of optical dosimetry, we have estimated that 20 J/cm^sub 2^ is the fluence required to produce prostatic necrosis. Thus, the normal structure adjacent to the prostate can be safely preserved with careful dosimetry. At therapeutic

PDT levels, there was no structural or functional urethral damage even when the urethra was within the treated region. Hence, Tookad-PDT appears to be a promising candidate for prostate ablation in patients with recurrent, or possibly even primary, prostate cancer.

Abbreviations: Deff, effective attenuation depth; H&E, hematoxylin and eosin; HIFU, high-intensity focused ultrasound; i.v., intravenous; PDT, photodynamic therapy; SQ, subcutaneous; Tookad, palladium-bacteriopheophorbide, WST09.

INTRODUCTION

In the United States, prostate cancer is the most common cancer in men, and the second leading cause of cancer death among them (1). Although there are only palliative treatments for metastatic prostate cancer, early-stage prostate cancer is often confined within the organ and is treated with curative intent by surgery, radiation therapy (brachytherapy, external beam or a combination of both), or by both surgery and radiation, which offer a cure rate ranging from 50% to 70% (2-4). Significant side effects are reported to be associated with these current therapies. Approximately half of the patients suffer from impotency after either radiation or surgery (4,5). Other severe complications include urinary incontinence and injuries to nearby structures after radical prostatectomy (surgical removal of prostate), and bladder and bowel dysfunction after radiation therapy. Hyperthermia has been used in both benign hyperplasia and cancer of the prostate, primarily to relieve the urinary symptoms. The outcomes of the treatments appear to be modest (6). The primary limitation of hyperthermia is the difficulty in achieving a temperature (in the prostatic tissue) high enough to cause direct cell killing, using current technologies for energy delivery devices. Other drawbacks are that several sessions are required to provide even temporary relief of the symptoms, and there is the potential to develop prostatorectal fistula (6). Image-guided cryotherapy provides another option for the treatment of primary prostate cancer. But available data indicate that the results of cryotherapy are comparable with those of both radiotherapy and radical prostatectomy (7). High-intensity focused ultrasound (HIFU) is a minimally invasive technique and can induce thermal lesions at depths >10 cm. Preliminary results showed that transrectal HIFU could induce partial ablation with high rates of negative biopsies, low prostate-specific antigen and a low complication rate, although some patients might need transurethral debris resection (8). There is still a need for an alternative or adjunctive therapy to treat localized prostate cancer, either as a primary modality or as a postradiation failure.

Photodynamic therapy (PDT) is an evolving cancer treatment modality. The procedure involves administration of a light-sensitive drug (photosensitizer). A time is allowed for the drug to be taken up in the target tissue that is then irradiated with light of appropriate wavelength to activate the photosensitizer. This initiates a sequence of photochemical, chemical and biological reactions, which ultimately lead to cell death (9). PDT using the first-generation photosensitizer Photofrin (Axcan, Montreal, Canada) has been approved by the U.S. Food and Drug administration for treatment of selected types of tumors such as esophageal and lung cancers. The feasibility of using PDT on animal models to treat prostate cancer has been investigated in this laboratory as well as in several others. There are several reports of PDT in a rat prostate tumor model, which indicate that PDT can effectively kill prostate tumors (10-14). Canine prostate has been used as an animal model for studying PDT in prostate because of its resemblance both in physical size and in anatomical structure to that of humans. In vivo optical properties of canine prostate have been studied for Photofrin-mediated PDT in this laboratory and were found to be similar to those of in vivo human prostate (15-17). Canine prostate tissue responses to PDT mediated by various photosensitizing agents were investigated (18-22), and the general consensus is that, given a fixed optical dose, the volume of tissue damage is rather unpredictable.

The present work is a pilot study using a second-generation photosensitizer, palladium-bacteriopheophorbide, WST09 (Tookad; Steba Biotech, Toussus-Le-Noble, France), to ablate prostatic tissue. Tookad is a novel and pure palladium-substituted bacteriochlorophyll derivative (Fig. 1). It has a maximum absorption wavelength in the near-infrared (763 nm) with a high extinction coefficient (epsilon = 10^sup 5^ mol^sub -1^ cm-^sup -1^ in chloroform [23]). The drug has extremely fast pharmacokinetics-cleared rapidly from the circulation (95% in 15 min in mice) and from other tissue in the order of a few hours (A. Scherz, personal communication). Its effectiveness on human prostatic small-cell carcinoma has been demonstrated on a mouse xenografts model (Y. Salomon, personal communication).

The objectives of this study were to (1) demonstrate that Tookad-PDT can destroy a clinically significant volume of prostate tissue; (2) determine the optimum drug-light time interval; (3) assess the dependence of the size of the PDT lesion on the light dose; and (4) determine the potential phototoxic damage to adjacent tissues and normal prostatic structures, including the bladder, rectum and urethra, and thereby evaluate the potential effectiveness and morbidity of the treatment. Because the ultimate clinical objective requires that the whole prostate be treated because of the poor differentiation from normal tissue and the multinodular nature of prostate cancer, it was critical for this study to use a large-animal model in which the size of the prostate is similar to that in humans. Hence, canines were selected. The limitation is that there is no readily available prostate cancer model in the canine (other than serendipitous spontaneous disease). Hence, the study reports only on the response of normal prostate tissue. But there are reports indicating that, if all other treatment parameters are identical, PDT is likely to be equally effective in destroying normal tissue and the embedded cancerous tissue from the same tissue origin (24-29). Again, given that the selective destruction of tumor is not an absolute prerequisite for PDT to be applied successfully in patients, the results obtained are directly useful for the design of clinical trials.

DISCUSSION

For early-stage cancer confined within the prostate, standard therapy such as ionizing radiation or surgical prostatectomy does not differentiate between normal and cancerous prostate tissue. Rather, the goal is to ablate the entire organ. Thus, the ultimate goal of PDT in the management of prostate cancer is likely to be total ablation of the gland (15). Hence, the observations here are directly relevant to assessing the likely clinical utility of Tookadbased PDT of prostate cancer, assuming that the response of the malignant tissue will not be less than that of normal prostate. The high vascularity of tumor tissue makes it a good target for Tookad-PDT because the effects are believed to be primarily vascular (32). Furthermore, in locally recurrent cancer after radical radiation therapy, the normal prostate tissue becomes relatively avascular (33,34), which may confer some selective sensitivity of the neovascularized tumor.

It has been demonstrated in different tissues that PDT, in general, destroys glandular tissue (normal or neoplastic), yet has little effect on connective tissue. This is not completely true when a prostate is treated with Tookad-PDT; even if it largely retained its anatomical shape and structure. As shown with collagen staining, the healing process of normal prostate after Tookad-PDT is largely because of resolving and shrinking of necrotic tissue and rapid fibrosis, so that there should be minimal side effects compared with, for example, radical prostatectomy. Three months after PDT, small areas of glandular regeneration surrounded by bands of dense collagen were observed, indicating glandular cell proliferation from unaffected regions.

The potential of Tookad for this application of PDT is partly attributable to its being activated at a relatively long wavelength, with corresponding greater light penetration depth in the tissue. For example, compared with Photofrin-PDT, which we have investigated previously (6), for which Deff averaged 1.6 turn in normal prostate, the value found here at 763 nm was 4 mm. The deeper light penetration combined with the apparent high photodynamic effectiveness of Tookad means that much larger lesions than we were able to obtain previously with Photofrin-PDT at 630 nm (typically I cm diameter) can be produced. For example, lesions >3 cm diameter were obtained with a single interstitial diffusing fiber and a total light fluence of 100-200 J/cm. Such light fluences can be delivered in a time short enough to activate the drug while it is still in the vasculature but at a rate that does not induce significant tissue heating. The longer wavelength also makes the light distribution less sensitive to changes in tissue blood content: as seen in Fig. 2, there was little change in the local measured fluence rate during treatment in contrast to our findings with Photofrin at 630 mn where the fluence rate varied by more than 50% during an irradiation (6,15). This may also contribute to the contiguous and uniform lesions with Tookad, compared with the patchy distribution with Photofrin, although the drug distribution is also likely to play a significant role in this. Together, these features may make it possible to achieve complete tissue destruction throughout the prostate with a relatively small number of interstitial sources (35). To do this reliably and safely, the drug and light dosimetry must be very accurately controlled and monitored. The variability of the lesion size at the higher light doses (Fig. 4) reinforces this point.

For reasons that are not understood, the PDT response of the normal bladder and colon appeared to be minimal compared with that of prostate tissue when treated with the same 40 J/cm^sup 2^ dose. There was considerable light scatter with each treatment, particularly at the higher fluences. For the largest PDT lesions (200 J/ cm, interstitial fiber, 1.5 cm radius lesion, Deff ~ 3 mm, assuming a few millimeter range for fluence buildup caused by backscatter), an upper estimate of the light fluence at the PDT lesion boundary is ~20 J/cm^sup 2^, so that this is consistent with there being no colon or bladder damage caused by scattered light, The relative insensitivity of the colon or rectum and bladder should provide an additional safety margin that should allow aggressive treatment of the prostate with low risk of damage to these adjacent structures from scattered light. It is also encouraging that the effect on the urethra was minimal, both functionally in terms of micturition and from the gross and microscopic appearance, even when the prostatic urethra was within the treatment area and the immediately adjacent prostate tissue was destroyed. This was not the case with Photofrin (6,15) and may be related to the purely vascular targeting. The lack of urethral obstruction after PDT might have been related to the use of the steroid dexamethasone given to suppress the side effects of Cremophor.

In contrast to many photosensitizers being investigated clinically (36,37), Tookad-PDT is believed to be almost entirely vascularly mediated. The clearance of Tookad is very fast, with a plasma half-life in the mouse typically

The Tookad formulation, administered intravenously, induced a marked drop in blood pressure in the dogs because of the presence of Cremophor, which is known to induce anaphylactoid reaction in this species (39). This side effect was easily controlled by premeditation with antihistamine (i.v. Benadryl, 0.7-1.4 mg/ kg) and steroids (dexamethasone, 2 mg SQ) and by adjustment of the anesthesia. Again, this will need to be incorporated into clinical protocols, although it is noted that other photosensitizers (40) and antineoplastic drugs in common use, such as paclitaxol, also use similar excipients (41).

In conclusion, these results suggest that Tookad may be well suited for PDT of prostate cancer. Clinical trials are currently being designed, initially for treatment of patients with localized recurrence of disease after radiation therapy failure. The initial drug and light doses and dose rates, and the drug-light time intervals, will be based on the findings reported above, together with other preclinical toxicology and PDT-response data (23,32, 35). Although this study and the initial trials are not predicated on there being an intrinsic selectivity for prostate cancer compared with normal prostate tissue, it will be of great interest to investigate whether this is the case.

Acknowledgments-This research was supported in put by Steba Biotech (France) and NIH grant POI-CA43892.

(para) Posted on the website on 25 July 2002.

REFERENCES

1. Boring, C. C., T. X. Squires and T. Tong (1994) Cancer statistics. Can. J. Clin. 44, 7-26.

2. Paulson, D. F. (1988) Randomized series of treatment with surgery versus radiation for prostate adenocarcinoma. In Consensus Development Conference on the Management of Clinically Localized Prostate Cancer (Edited by R. I. Wittes), pp. 121-137. Government Printing Office, Washington, DC. [NIH publication no. 88-3005. NCI Monographs 7]

3. Lepor, H. and P. C. Walsh (1988) Long-term results of radical prostatectomy in clinically localized prostate cancer: experience at the John Hopkins Hospital. In Consensus Development Conference on the Management of Clinically Localized Prostate Cancer (Edited by R. I. Wittes), pp. 117-122. Government Printing Office, Washington, DC. [NIH publication no. 88-3005. NCI Monographs 7]

4. Catalona, W. J. (1994) Management of cancer of the prostate. N. Eng. J. Med. 331, 996-1004.

5. Stamey, T. A. (1993) Irradiation as primary treatment for prostate cancer. Am. Urol. Assoc. Today 6, 14.

6. Chen, Q. and F. W. Hetzel (1998) Laser dosimetry studies in the prostate. J. Clin. Laser Med. Surg. 16, 9-12.

7. Onik, G. (2001) Image-guided prostate cryosurgery: state of the art. Cancer Control 8, 522-531.

8. Chaussy, C. and S. Thuroff (2001) Results and side effects of high-intensity focused ultrasound in localized prostate cancer. J. Endourol. 15, 437-440.

9. Henderson, B. W. and T. J. Dougherty (1992) How does photodynamic therapy work? Photochem. Photobiol. 55, 145-157.

10. McPhee, M. S., C. W. Thorndyke, G. Thomas, J. Tulip, D. Chapman and W. H. Lakey (1984) Interstitial applications of laser irradiation in hematoporphyrin derivative-photosensitized Dunning R3327 prostate cancers. Lasers Surg. Med. 4, 93-98.

11. Moore, R. B., J. D. Chapman, J. R. Mercer. R. H. Mannan, L. I. Wiebe, A. J. McEwan and M. S. McPhee (1993) Measurement of PDT-induced hypoxia in Dunning prostate tumors by iodine123-iodoazomycin arabinoside. J. Nucl. Med. 34, 405-411.

12. Momma, T., M. R. Hamblin, H. C. Wu and T. Hasan (1998) Photodynamic therapy of orthotopic prostate cancer with benzoporphyrin derivative: local control and distant metastasis. Cancer Res. 58, 5425-5431.

13. Colasanti, A., A. Kisslinger, R. Liuzzi, M. Quarto, P. Riccio, G. Roberti, D. Tramontano and F. Villani (2000) Hypericin photosensitization of tumor and metastatic cell lines of human prostate. J. Photochem. Photobiol. B: Biol 54, 103-107.

14. Xie, X., J. B. Hudson and E. S. Guns (2001) Tumor-specific and photodependent cytotoxicity of hypericin in the human LNCaP prostate tumor models. Photochem. Photobiol. 74, 221-225.

15. Chen, Q., B. C. Wilson, S. D. Shetty, M. S. Patterson, J. C. Cerny and F. W. Hetzel (1997) Changes in in vivo optical properties and light distributions in normal canine prostate during photodynamic therapy. Radiat. Res. 147, 86-91.

16. Lee, L. K., C. Whitehurst, M. L. Pantelides and J. V. Moore (1995) In situ comparison of 665 nm and 633 nm wavelength light penetration in the human prostate gland. Photochem. Photobiol. 62, 882-886.

17. Lee, L. K., C. Whitehurst, M. L. Pantelides and J. V. Moore (1995) Interstitial photodynamic therapy in the canine prostate. Br. J. Urol. 80, 898-902.

18. Selman, S. H., R. W. Keck and J. A. Hampton (1996) Transperineal photodynamic ablation of the canine prostate. J. Urol. 156, 258260.

19. Selman, S. H., D. Albrecht, R. W. Keck, P. Brennan and S. Kondo (2001) Studies of tin ethyl etiopurpurin photodynamic therapy of the canine prostate. J. Urol. 165, 1795-1801.

20. Chang, S., G. A. Buonaccorsi, A. J. MacRobert and S. G. Bown (1997) Interstitial photodynamic therapy in the canine prostate with disulfonated aluminum phthalocyanine and 5-aminolevulinic acidinduced protoporphyrin IX. The Prostate 32, 89-98.

21. Chang, S., G. Buonaccorsi, A. MacRobert and S. G. Bown (1996) Interstitial and transurethral photodynamic therapy of the canine prostate using meso-tetra-(m-hydroxyphenyl) Chlorin. Int. J. Cancer 67, 555-562.

22. Hsi, R. A., A. Kapatkin, J. Strandberg, T. Zhu, T. Vulcan, M. Solonenko, C. Rodriguez, J. Chang, M. Saunders, N. Mason and S. Hahn (2001) Photodynamic therapy in the canine prostate using motexatin lutetium. Clin. Cancer Res. 7, 651-660.

23. Scherz, A., Y. Salomon, H. Scheer and A. Brandis (1999) Palladium-substituted bacteriochlorophyll derivatives and use thereof. International PCT patent application no. PCT/IL99/00673.

24. Wagnieres, G., C. Hadjur, P. Grosjean, D. Braichotte, J. F. Savary, P. Monnier and H. van den Bergh (1998) Clinical evaluation of the cutaneous phototoxicity of 5,10,15,20-tetra(m-hydroxyphenyl)chlorin. Photochem. Photobiol. 68, 382-387.

25. van Geel, I. P., H. Oppelaar, Y. G. Oussoren, M. A. van der Valk and F. A. Stewart (1995) Photosensitizing efficacy of MTHPC-PDT compared to Photofrin-PDT in the RIFT mouse tumour and normal skin. Int. J. Cancer 60, 388-394.

26. Chen, J. Y.. N. K. Mak, J. M. Wen, W. N. Leung, S. C. Chen, M. C. Fung and N. H. Cheung (1998) A comparison of the photodynamic effects of temoporfin (mTHPC) and MC540 on leukemia cells: efficacy and apoptosis. Photochem. Photobiol. 68, 545-554.

27. Regula, J., B. Ravi, J. Bedwell, A. J. MacRobert and S. G. Bown (1994) Photodynamic therapy using 5-aminolaevulinic acid for experimental pancreatic cancer-prolonged animal survival. Br. J. Cancer 70, 248-254.

28. Bedwell, J., A. J. MacRobert, D. Phillips and S. G. Bown (1992) Fluorescence distribution and photodynamic effect of ALA-induced PpIX in the DMH rat colonic tumor model. Br. J. Cancer 65, 818824.

29. Barr, H., N. Krasner, P. B. Boulos, P. Chatlani and S. G. Bown (1990) Photodynamic therapy for colorectal cancer: a quantitative pilot study. Br. J. Surg. 77, 93-96.

30. Sheeham, D. C. and B. B. Hrapchak (1987) Theory and Practice of Histotechnology, pp. 196-197. Battelle Press, Columbus, OH.

31. Selman, S. H. and R. W. Keck (1994) The effect of transurethral light on the canine prostate after sensitization with the photosensitizer tin (II) etiopurpurin dichloride: a pilot study. J. Urol. 152, 21292132.

32. Zilberstein, J., S. Schreiber, M. C. Bloemers, P. Bendel, M. Neeman, E. Schechtman, F. Kohen, A. Scherz and Y. Salomon (2001) Anti vascular treatment of solid melanoma tumors with bacteriochlorophyll-serine-based photodynamic therapy. Photochem. Photobiol. 73, 257-263.

33. Nadalini, V. F., C. Giglio, G. Bruttini, N. Positano, M. Fassone, L. Fasce, M. Medica, P. de Angelis, 0. Fantacci, D. Scarpati and S. Ledda (1983) Histological follow-up after implantation of grains of I-125 for prostatic cancer. J. Urol. (Paris) 89, 187-190. [In French]

34. Sheaff, M. T. and S. I. Baithum (1997) Effects of radiation on the normal prostate gland. Histopathology 30, 341-348.

35. Chen, Q., Z. Huang, D. Luck, J. Beckers, P. Brun, B. C. Wilson, A. Scherz, Y. Salomon and F. W. Hetzel (2002) WST09 (TOOKAD) mediated photodynamic therapy as an alternative modality in treatment of prostate cancer. Prog. Biomed. Opt. Imaging 3, 29-39. [see also Proc. SPIE. 4612]

36. Adili, F., R. G. Statius van Eps and G. M. LaMuraglia (1999) Significance of dosimetry in photodynamic therapy of injured arteries: classification of biological responses. Photochem. Photobiol. 70, 663-668.

37. Kurohane, K., A. Tominaga, K. Sato, J. R. North, Y. Namba and N. Oku (2001) Photodynamic therapy targeted to tumor-induced angiogenic vessels. Cancer Lett. 167, 49-56.

38. Messmer, K. J. and S. R. Abel (2001) Verteporfin for age-related macular degeneration. Ann. Pharmacother. 35, 1593-1598.

39. Bowers, V. D., S. Locker, S. Ames, W. Jennings and R. J. Corry (1991) The hemodynamic effects of Cremophor-EL. Transplantation 51, 847-850.

40. Decreau, R., M. J. Richard, P. Verrando, M. Channon and M. Julliard (1990) Photodynamic activities of silicon phthalocyanines against achromic M6 melanoma cells and healthy human melanocytes and keratinocytes. J. Photochem. Photobiol. B: Biol 48, 48-56.

41. Gelderblom, H., J. Verweij, K. Nooter and A. Sparreboom (2001) Cremophor EL: the drawbacks and advantages of vehicle selection for drug formulation. Eur. J. Cancer 37, 1590-1598.

Qun Chen*1, Zheng Huang1, David Luck1, Jill Beckers1, Pierre-Herve Brun2, Brian C. Wilson3, Avigdor Scherz4, Yoram Salomon4 and Fred W. Hetrel1

1HealthONE Alliance, Denver, CO;

2Steba Biotech, Toussus-Le-Noble, France;

3Ontario Cancer Institute, University of Toronto, Toronto, Canada and

4Weizmann Institute of Science, Rehovot, Israel

Received 24 April 2002; accepted 22 July 2002

*To whom correspondence should be addressed at: HealthONE Alliance, 1850 High Street, Denver, CO 80218, USA. Fax: 303-320-6018; e-mail: pdtlaser@aol.com

Copyright American Society of Photobiology Oct 2002
Provided by ProQuest Information and Learning Company. All rights Reserved