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The mitochondrial dye Rhodamine 123 (Rh-123) has been shown to be an effective photosensitizer for argon-laser irradiation of some types of human cancer cells in vitro. We reported that 514.5-nm laser illumination of Rh-123 sensitized human melanoma, and squamous carcinoma cells strongly inhibited tumor-cell proliferation as measured by decreased 3H-thymidine (3H-T) uptake in vitro and may eradicate some tumors when grown as transplants in nude mice. However, several other human tumors were resistant to Rh-123 laser therapy in vitro and in vivo. In the current study, it was possible to obtain 100- to 1000-fold increased sensitivity to 514.5-nm laser illumination by replacement of Rh-123 with the cationic rhodamine dyes Rh-3G and Rh-6G. Cell viability was decreased over 95% and 3H-T incorporation reduced at least 80% by laser phototherapy after sensitizing tumor cells with 1 micrograms/mL Rh-123, 0.01 microgram/mL Rh-3G, or 0.001 microgram/mL Rh-6G. However, Rh-123 alone did not decrease 3H-T uptake significantly unless present at over 10- to 100-fold higher levels than Rh-3G, respectively. The tumor cell dye uptake level was measured by N-butanol extraction and absorption scans at 400 to 600 nm. The results revealed that dye uptake was more rapid, and retention of Rh-3G and Rh-6G was 5- to 10-fold higher than for Rh-123 in the human tumor cells. The data suggest that Rh-3G and Rh-6G may be highly sensitive chromophores for laser phototherapy of human cancer cells. [ABSTRACT FROM AUTHOR]

Laser photodynamic therapy of superficial malignancies is a promising new approach that will become clinically useful when fluorochromes with high tumor specificity and low toxicity to normal tissues are identified. We recently reported that the mitochondrial dye, Rhodamine-123 (Rh-123), at nontoxic doses, is an effective sensitizing agent for argon laser treatment of human squamous carcinoma and melanoma cells in vitro. We now report the complete inhibition of in vivo tumor development by human M24 melanoma cells transplanted subcutaneously into nu/nu mice after exposure to 1 microgram/ml of Rh-123 for 1 hour and treatment with an argon laser at nonthermal temperatures of 36 to 40 degrees C. Significant in vivo growth was observed for all control tumors. These results demonstrate that Rh-123 enhances the tumoricidal effects of the argon laser at nonthermal temperatures and provides evidence that effective photodynamic therapy may be possible in vivo with the new fluorochrome Rhodamine-123. [ABSTRACT FROM AUTHOR]

The human squamous carcinoma cell line P3 was subjected to treatment with a single mode argon laser at 514.5 nm. The temperature and energy levels delivered to the target cells were determined by a reproducible method of dosimetry. At energy levels between 860 to 990 J/cm2 and a corresponding temperature of 39 +/- 1 degrees C, a significant delayed stimulation in DNA synthesis was noted after 24 hours, but the cells remained viable. However, at energy levels and temperatures higher or equal to 1100 J/cm2 (41 degrees C), an immediate suppression of DNA synthesis was accompanied by nonviability of the P3 carcinoma cells. These results indicate that the argon laser has potential for selective biostimulation on carcinoma cell duplication at the specific "non-thermal" range of 39 +/- 1 degrees C. Similar effects were not observed when the P3 carcinoma cells were heated to this same temperature using a standard heat bath. This phenomenon appears to represent a previously undescribed potential iatrogenic effect of the monochromatic laser beam in the treatment of cancer. [ABSTRACT FROM AUTHOR]

A human squamous carcinoma cell line (P3) was first exposed to a nontoxic dose of Rhodamine-123 (1 microgram/ml for 1 hour), then subjected to treatment with a single mode argon laser at 514.5 nm. The temperature and energy levels delivered to the target cells were determined by a reproducible method of dosimetry. Cell viability was assessed by the trypan blue exclusion test. Cell duplication and DNA synthesis were measured by the incorporation of 3H-thymidine at 6 and 24 hours post-treatment. The results indicate that Rhodamine-123 at nontoxic doses of 1 microgram/ml enhanced the tumoricidal effects of the argon laser at reduced temperatures as low as 40 degrees C. Furthermore, at physiological temperature ranges as low as 28 to 39 degrees C, an immediate and/or delayed inhibition of cell duplication was demonstrated, while cell viability was not affected. These observations, suggest that Rhodamine-123 can be used effectively as a chemosensitizing agent in the treatment of human tumor cells with the argon laser at 514.5 nm. This new technique of tumor cell targeting by Rhodamine sensitization and specific laser treatment may offer real advantages without the extreme photosensitivity associated with hematoporphyrin derivatives. [ABSTRACT FROM AUTHOR]

A new and highly promising adjunctive modality for the diagnosis and therapy of malignancies is under development using lasers and tumor targeting dyes. To reach the eventual goal of clinical treatment, several current "fantasies and fallacies" regarding laser applications in medicine must be identified and their problems clearly outlined. A multidisciplinary scientific approach is also required to enable the clinical practicality of this laser targeting approach. Many new dyes and laser wavelengths are being tested to improve specific tumor uptake and/or retention, lower systemic toxicity, increase tissue penetration, and identify fluorochromes with synergistic properties to further enhance laser tumoricidal effects. Rapid technological advancements in magnetic resonance imaging may now provide an extremely sensitive way to detect and monitor laser-tissue effects, and allow efficient interstitial laser phototherapy of deep and sometimes inaccessible tumors. The current and future prospectives of the emerging field of laser phototherapy are described.

Interstitial laser phototherapy (ILP) is a promising technique in which laser energy is delivered percutaneously to various depths of tumors. This technique will become clinically useful only when efficient, sensitive, and noninvasive monitoring systems are developed. In this study, the spatial distribution of ILP in bovine liver tissue, induced by a Nd: YAG laser with an interstitial sapphire-frosted contact probe, was evaluated by magnetic resonance imaging (MRI). Tissue was exposed to three energy densities of the Nd:YAG laser by a reproducible method of dosimetry. Thermal profiles were measured with a probe inserted 5 mm from the laser tip. T1-weighted magnetic resonance images were taken after the laser exposure. Tissue specimens were then evaluated for standard quantification of laser-induced damages. A linear correlation between the level of laser energy, induced temperature change, lesion size on T1 magnetic resonance image, and volume of histological damage was observed. Further improvement of this technique of dosimetry in an in vivo model should allow the development of software for MRI which will correlate the above parameters and render this technique of ILP clinically useful.

Recent studies demonstrated that the cationic, mitochondrial-specific dye Rhodamine-123 (Rh-123), is an efficient tumor photosensitizer for Argon laser treatment of human cancer cells both in vitro and in tumors grown as xenografts in athymic mice. To demonstrate the photodynamic mechanism of action of this reaction, the intracellular role of oxygen and temperature changes in treated cells have to be defined. In the current study, a large panel of human tumor cell lines of diverse histologic origin were tested for in vitro sensitivity to Rh-123 and the Argon laser (514.5 nm) in oxygen, deuterium oxide (D2O), and nitrogen (N2) environment. Tumor cells in suspension were first sensitized to Rh-123 (1 or 20 micrograms/ml for 1 hour), cooled on ice to 4 degrees C, and then exposed to the Argon laser (delta T = 14 +/- 1 degree C). Cell proliferation measured by [3H]-thymidine uptake 24 hours after sensitization with Rh-123 and laser treatment was significantly decreased in tumor cells kept in oxygen and D2O atmospheres. No decrease in DNA synthesis was seen in Rh-123 and laser treated cells kept in an N2 environment. Control tumor cells treated with Rh-123 or the Argon laser separately did not show any decreased [3H]-thymidine uptake in oxygen, D2O or N2 environment. These results provide evidence of a photodynamic process since Rh-123 sensitization and Argon laser activation occur at nonthermal levels of energy and are oxygen dependent. The high effectiveness of this technique of photodynamic therapy with the Argon laser, and low toxicity of Rh-123 could make its clinical use very attractive for the treatment of superficial malignancies.

The rapid technological advances of magnetic resonance imaging, laser fiberoptics, and compatible probes may allow treatment of deep and sometimes surgically unreachable tumors of the head and neck with minimal morbidity through interstitial laser phototherapy. In this study, a new application of magnetic resonance imaging was developed to monitor and quantify laser-induced tissue damages. Pig skin was exposed to increased levels of argon laser (514.5 nm) at energy densities between 62.5 and 375 J/cm2 as determined by an accurate and reproducible method of dosimetry. Thermal profiles were recorded using an infrared sensor and T1- and T2-weighted magnetic resonance images were taken; afterward, biopsies were performed to quantitate the level of tissue damage. Our results demonstrate that above a certain threshold of laser energy, the magnetic resonance imaging findings are temperature dependent. Appropriate development of a scale matching laser energies, temperature profiles, T1- and T2-weighted magnetic resonance images, and histological quantitation of tissue destruction will allow us to optimize the three-dimensional control and monitoring of laser-tissue interactions.

Kodak Q-switch II dye has recently proven to be an effective biostimulative agent on normal human fibroblast cultures. The potential for this dye as a new chemosensitizing agent for the treatment of connective tissue diseases and wound healing with the Nd:YAG laser was examined. Two normal fibroblast cell lines were first sensitized to a nontoxic dose of Q-switch II dye, then subjected to treatment with an Nd:YAG laser at 1,060 nm, with varying levels of energy and temperatures determined by a reproducible method of dosimetry. The results indicate that Q-switch II dye at nontoxic doses of 0.1 micrograms/ml enhances the cytotoxic effects of the Nd:YAG laser at temperatures as low as 36 degrees C. Furthermore, at physiological temperature ranges as low as 24 degrees C to 34 degrees C, cell duplication was inhibited, but cell viability was not affected. Similar results were not observed when fibroblast cultures were treated with the laser alone. These observations suggest that Q-switch II dye is an effective chemosensitizing agent for the Nd:YAG laser and could potentially be used to reduce collagen deposits in conditions such as keloids and hypertrophic scars.

Kodak Q-switch II is a new chemical with an absorption maxima at 1,051 nm, designed to be used as an Nd:YAG dye laser. The potential for this dye as a new chemosensitizing agent in the treatment of connective tissue diseases and wound healing with low energy Nd:YAG laser was examined. Two normal fibroblast cell lines were tested for sensitivity to various levels of this dye in vitro. These cells were exposed to Q-switch II dye at concentrations of 0.01, 0.1, 1, 10, 50, and 100 micrograms/ml for 1 and 24 hours. Cell viability was assessed by the trypan blue exclusion test. Cell duplication and DNA synthesis were measured by the incorporation of [3H]-thymidine at 6 and 24 hours postexposure to Q-switch II dye. At concentrations up to 10 micrograms/ml, both cell lines tested showed no changes in cell viability. However, at concentrations equal or higher than 50 micrograms/ml, more than 40% of the fibroblasts incorporated trypan blue after 24 hours of exposure to this dye, indicating significant cell destruction. The results indicate that Q-switch II dye is nontoxic to normal human fibroblast cultures and showed significant biostimulative effects on cell duplication at concentrations equal to or lower than 10 micrograms/ml. Further studies will be required to determine the usefulness of Q-switch II dye as a new photochemosensitizing agent for potential biostimulation of wound healing and/or treatment of connective tissue diseases with the Nd:YAG laser (near infrared, 1,060 nm) at "nonthermal" levels of energies.

Rhodamine-123 (Rh-123) is a mitochondrial-specific dye that has recently proven to be an effective fluorochrome for photo-dynamic therapy of squamous carcinoma cells and melanomas with the Argon laser. Complete eradication of heterotransplanted human tumors in nude mice was possible if tumors were first "sensitized" to Rh-123 and then treated with the Argon laser. Prior to initiation of human testing of this technique, the toxicity and pathological changes in BALB/c mice were tested by an escalating dose schedule after systemic injection of Rh-123. Animals' body weight, blood chemistry, enzymes and organ evaluation for histology, and ultrastructural changes were analyzed for 3 weeks after injection with Rh-123. The results of this study demonstrate that Rh-123 has significant systemic toxicity in BALB/c mice injected at doses of 10 micrograms/g of body weight and above, manifested by chronic weight loss and elevation of muscle enzymes with death of the animals injected at doses higher than 50 micrograms/g of body weight. At doses of 1 micrograms/g of Rh-123, no local or systemic toxicity was observed even after a 3-week follow-up, suggesting that safe and effective tumor sensitization might be possible in humans at this concentration. The high effectiveness of this new technique of photodynamic therapy and the low toxicity of this dye in this preclinical model system suggests that Rh-123 and the Argon laser may represent a powerful new method for treatment of superficial malignancies.