Total tumor cell elimination with minimum damage to normal tissues in musculoskeletal sarcomas following photodynamic therapy with acridine orange

The safety and efficiency of photodynamic therapy for the treatment of osteosarcoma: A systematic review of in vitro experiment and animal model reports

BACKGROUND

Osteosarcoma (OS) is an aggressive malignant bone tumour with high mortality. A poor prognosis is noted in patients with distal metastases or multidrug resistance. As an emerging antitumor strategy, photodynamic therapy (PDT) mediated by visible and near infrared light has attracted intensive attention given its target selectivity, remote controllability, minimal or non-invasive features. However, PDT also has obvious limitations. Specifically, due to the limited penetration of light, it is mainly used in the clinical treatment of superficial malignant tumours, such as musculoskeletal sarcomas and melanoma, but it has not been applied to the clinical treatment of deep malignant bone tumours except for a very small number of experiments on deep canine OS models.

MATERIALS AND METHODS

We searched for studies that focused on the effectiveness and safety of PDT for OS based on in vitro experiments and animal models in the last decade. A systematic search was conducted using electronic databases, including PubMed, ClinicalTrials.gov, and the Cochrane Library.

INCLUSION CRITERIA

(1) original research articles about PDT for OS; (2) articles in English; (3) in vitro or animal model research; and (4) detailed information, including cell name, fluence, irradiation wavelength, time of incubation with PS, duration between PS treatment and irradiation, and duration between irradiation and viability assays.

EXCLUSION CRITERIA

(1) study was a review/systemic review article, patent, letter, or conference abstract/paper; (2) articles were not published in English; (3) studies containing overlapping or insufficient data.

RESULTS

We identified 201 publications, and 44 articles met the inclusion criteria and were included in the synthesis. Unfortunately, there are no relevant clinical reports of the use of PDT in the treatment of human OS. In these studies, 8 studies only employed in vivo experiments to evaluate the efficiency of PDT in an OS animal model, 19 studies exclusively performed in vitro viability assays of cells treated with PDT under different conditions, and 17 studies included in vitro cell experiments and in vivo animal OS models to evaluate the effect of PDT on OS in vivo and in vitro. All studies have shown that PDT is cytotoxic to OS cells or can inhibit the growth of OS in heterologous or homologous animal OS models but exhibits minimal cytotoxicity at a certain range of dosages.

CONCLUSION

Based on this systematic review, PDT can eradicate OS cells in cell culture and there is some evidence for efficacy in animal models. However, the ability for PDT to control human OS is unclear, the animal and human reports do not show evidence of human OS control, they just do show feasibility. The major issues concerning the potential for treatment of osteosarcoma with PDT are that adequate light should be transmitted to tumor loci and if the disease is caught before metastasis and irradiation of tumor sites is feasible, curative potential is there. Otherwise, PDT may be mainly palliative. To determine whether PDT can safely and efficiently be used in the clinical treatment of OS, many preclinical orthotopic animal OS models and OS models of multiple systemic metastases must be performed and interstitial PDT or intraoperative PDT may be a good and potential candidate for human OS treatment. If these problems can be well solved, PDT may be a potentially effective strategy for the treatment of OS patients.

Radiodynamic therapy with acridine orange local administration as a new treatment option for primary and secondary bone tumours

AIMS

Acridine orange (AO) demonstrates several biological activities. When exposed to low doses of X-ray radiation, AO increases the production of reactive radicals (radiodynamic therapy (AO-RDT)). We elucidated the efficacy of AO-RDT in breast and prostate cancer cell lines, which are likely to develop bone metastases.

METHODS

We used the mouse osteosarcoma cell line LM8, the human breast cancer cell line MDA-MB-231, and the human prostate cancer cell line PC-3. Cultured cells were exposed to AO and radiation at various concentrations followed by various doses of irradiation. The cell viability was then measured. In vivo, each cell was inoculated subcutaneously into the backs of mice. In the AO-RDT group, AO (1.0 μg) was locally administered subcutaneously around the tumour followed by 5 Gy of irradiation. In the radiation group, 5 Gy of irradiation alone was administered after macroscopic tumour formation. The mice were killed on the 14th day after treatment. The change in tumour volume by AO-RDT was primarily evaluated.

RESULTS

The viability of LM8, MDA-MB-231, and PC-3 cells strongly decreased at AO concentration of 1.0 μg/ml and a radiation dose of 5 Gy. In xenograft mouse model, the AO-RDT also showed a strong cytocidal effect on tumour at the backside in osteosarcoma, breast cancer, and prostate cancer. AO-RDT treatment was more effective for tumour control than radiotherapy in breast cancer.

CONCLUSION

AO-RDT was effective in preventing the proliferation of osteosarcoma, breast cancer, and prostate cancer cell lines in vitro. The reduction in tumour volume by AO-RDT was also confirmed in vivo.Cite this article: Bone Joint Res 2022;11(10):685-692.

Radiodynamic Therapy with Acridine Orange Is an Effective Treatment for Bone Metastases

Current multimodal treatment of bone metastases is partially effective and often associated with side effects, and novel therapeutic options are needed. Acridine orange is a photosensitizing molecule that accumulates in acidic compartments. After photo- or radiodynamic activation (AO-PDT or AO-RDT), acridine orange can induce lysosomal-mediated cell death, and we explored AO-RDT as an acid-targeted anticancer therapy for bone metastases. We used osteotropic carcinoma cells and human osteoclasts to assess the extracellular acidification and invasiveness of cancer cells, acridine orange uptake and lysosomal pH/stability, and the AO-RDT cytotoxicity in vitro. We then used a xenograft model of bone metastasis to compare AO-RDT to another antiacid therapeutic strategy (omeprazole). Carcinoma cells showed extracellular acidification activity and tumor-derived acidosis enhanced cancer invasiveness. Furthermore, cancer cells accumulated acridine orange more than osteoclasts and were more sensitive to lysosomal death. In vivo, omeprazole did not reduce osteolysis, whereas AO-RDT promoted cancer cell necrosis and inhibited tumor-induced bone resorption, without affecting osteoclasts. In conclusion, AO-RDT was selectively toxic only for carcinoma cells and effective to impair both tumor expansion in bone and tumor-associated osteolysis. We therefore suggest the use of AO-RDT, in combination with the standard antiresorptive therapies, to reduce disease burden in bone metastasis.

Progress of Phototherapy Applications in the Treatment of Bone Cancer

Bone cancer including primary bone cancer and metastatic bone cancer, remains a challenge claiming millions of lives and affecting the life quality of survivors. Conventional treatments of bone cancer include wide surgical resection, radiotherapy, and chemotherapy. However, some bone cancer cells may remain or recur in the local area after resection, some are highly resistant to chemotherapy, and some are insensitive to radiotherapy. Phototherapy (PT) including photodynamic therapy (PDT) and photothermal therapy (PTT), is a clinically approved, minimally invasive, and highly selective treatment, and has been widely reported for cancer therapy. Under the irradiation of light of a specific wavelength, the photosensitizer (PS) in PDT can cause the increase of intracellular ROS and the photothermal agent (PTA) in PTT can induce photothermal conversion, leading to the tumoricidal effects. In this review, the progress of PT applications in the treatment of bone cancer has been outlined and summarized, and some envisioned challenges and future perspectives have been mentioned. This review provides the current state of the art regarding PDT and PTT in bone cancer and inspiration for future studies on PT.

Impact of Acridine Orange in Patients With Local Recurrent Soft Tissue Sarcoma

BACKGROUND/AIM

Local recurrence in soft tissue sarcoma (STS) is a risk factor of worse prognosis. Although a few studies have shown that adjuvant therapy with acridine orange (AO) is effective for local control of primary STS, there have been no reports examining its effectiveness for local recurrence.

PATIENTS AND METHODS

This retrospective study included 36 patients with first local recurrence of STS. Of them, 23 patients received wide excision without AO therapy (Wide group); the other 13 patients received marginal excision with AO therapy (AO group). We compared re-recurrence rates between these two groups.

RESULTS

The total re-recurrence rate was 43.5% in the Wide group and 46.2% in the AO group. There was no significant difference in local re-recurrence-free survival and overall survival between the two groups.

CONCLUSION

Adjuvant AO therapy combined with a marginal excision suppresses local re-recurrence rates of individuals with local STS recurrence.

Acridine Orange: A Review of Novel Applications for Surgical Cancer Imaging and Therapy

Introduction: Acridine orange (AO) was first extracted from coal tar in the late nineteenth century and was used as a fluorescent dye. In this paper, we review emergent research about novel applications of AO for fluorescence surgery and cancer therapy. Materials and methods: We performed a systematic search in the MEDLINE, PubMed, Cochrane library, Google Scholar, Embase, Web of Science, and Scopus database using combinations of the term "acridine orange" with the following: "surgical oncology," "neuropathology," "microsurgery," "intraoperative fluorescence," "confocal microscopy," "pathology," "endomicroscopy," "guidance," "fluorescence guidance," "oncology," "surgery," "neurooncology," and "photodynamic therapy." Peer-reviewed articles published in English were included in this review. We have also scanned references for relevant articles. Results: We have reviewed studies on the various application of AO in microscopy, endomicroscopy, intraoperative fluorescence guidance, photodynamic therapy, sonodynamic therapy, radiodynamic therapy. Conclusion: Although the number of studies on the clinical use of AO is limited, pilot studies have demonstrated the safety and feasibility of its application as an intraoperative fluorescent dye and as a novel photo- and radio-sensitizator. Further clinical studies are necessary to more definitively assess the clinical benefit AO-based fluorescence guidance, therapy for sarcomas, and to establish feasibility of this new approach for the treatment of other tumor types.

Photodynamic Surgery for Feline Injection-Site Sarcoma

Musculoskeletal sarcomas are rare and aggressive human malignancies affecting bones and soft tissues with severe consequences, in terms of both morbidity and mortality. An innovative technique that combines photodynamic surgery (PDS) and therapy (PDT) with acridine orange has been recently suggested, showing promising results. However, due to the low incidence of sarcoma in humans, this procedure has been attempted only in pilot studies and stronger evidence is needed. Naturally occurring tumors in cats are well-established and advantageous models for human cancers. Feline injection-site sarcoma (FISS) shares with human musculoskeletal sarcomas a mesenchymal origin and an aggressive behavior with a high relapse rate. Furthermore, wide surgical excision is not always possible due to the size and site of development. We assessed the feasibility and the effectiveness of PDS and PDT with acridine orange to prevent FISS recurrence by treating a short case series of cats. For PDS, the surgical field was irrigated with an acridine orange solution and exposed to UV light to enlighten the residual tumor tissue, and the resultant fluorescent areas were trimmed. For PDT, before wound closure, the field was again irrigated with acridine orange solution and exposed to visible light to get the antitumoral cytocidal effect. The procedure was easy to perform and well tolerated, we did not observe any major complications, and all the surgical resection margins were free of disease. Finally, at follow-up, all treated patients did not show evidence of tumor recurrence and had a significantly higher event-free survival rate in respect to a control group treated only by surgery. In conclusion, by this study we demonstrated that, in FISS, PDS and PDT with acridine orange may improve local tumor control, granting a better outcome, and we laid the foundation to validate its effectiveness for the treatment of human musculoskeletal sarcomas.

Long-term clinical outcome in patients with high-grade soft tissue sarcoma who were treated with surgical adjuvant therapy using acridine orange after intra-lesional or marginal resection

BACKGROUND

We investigated the long-term clinical efficacy of acridine orange (AO) therapy on the inhibition of local recurrence after marginal or intra-lesional tumor resection in high-grade soft tissue sarcomas (STSs).

METHODS

Our study consisted of 48 patients with STSs who received AO therapy after marginal or intra-lesional resection. The median and mean follow-up durations were 76 and 78 months, respectively. Our AO therapy procedure was combined with photodynamic surgery, photodynamic therapy, and radiodynamic therapy.

RESULTS

There were 25 men and 23 women, with a mean age of 46 years. The average tumor size at surgery was 8.5 cm. At the last follow-up, 11 patients developed local recurrence. The 5- and 10-year local recurrence-free rates were 78.9% and 73.3%, respectively. In multivariate analysis, tumor size remained significant for local control. None of the patients developed systemic or local complications. All patients recovered activities of daily life before AO therapy.

CONCLUSION

AO therapy can be performed in safety and may be a useful therapy for acquiring long-term local control in patients with high-grade STSs. Tumor size is an important factor for the indication of AO therapy.

Acridine orange exhibits photodamage in human bladder cancer cells under blue light exposure

Human bladder cancer (BC) cells exhibit a high basal level of autophagic activity with accumulation of acridine-orange(AO)-stained acidic vesicular organelles. The rapid AO relocalization was observed in treated BC cells under blue-light emission. To investigate the cytotoxic effects of AO on human BC cell lines under blue-light exposure, human immortalized uroepithelial (SV-Huc-1) and BC cell lines (5637 and T24) were treated with indicated concentrations of AO or blue-light exposure alone and in combination. The cell viability was then determined using WST-1, time-lapse imaging with a Cytosmart System and continuous quantification with a multi-mode image-based reader. Treatment of AO or blue-light exposure alone did not cause a significant loss of viability in BC cells. However, AO exhibited a dose-dependent increment of cytotoxicity toward BC cells under blue-light exposure. Furthermore, the tumor formation of BC cells with treatment was significantly reduced when evaluated in a mouse xenograft model. The photodamage caused by AO was nearly neglected in SV-Huc-1 cells, suggesting a differential effect of this treatment between cancer and normal cells. In summary, AO, as a photosensitizer, disrupts acidic organelles and induces cancer cell death in BC cells under blue-light irradiation. Our findings may serve as a novel therapeutic strategy against human BC.

Microenvironmental acidosis in carcinogenesis and metastases: new strategies in prevention and therapy

Much effort is currently devoted to developing patient-specific cancer therapy based on molecular characterization of tumors. In particular, this approach seeks to identify driver mutations that can be blocked through small molecular inhibitors. However, this approach is limited by extensive intratumoral genetic heterogeneity, and, not surprisingly, even dramatic initial responses are typically of limited duration as resistant tumor clones rapidly emerge and proliferate. We propose an alternative approach based on observations that while tumor evolution produces genetic divergence, it is also associated with striking phenotypic convergence that loosely correspond to the well-known cancer “hallmarks”. These convergent properties can be described as driver phenotypes and may be more consistently and robustly expressed than genetic targets. To this purpose, it is necessary to identify strategies that are critical for cancer progression and metastases, and it is likely that these driver phenotypes will be closely related to cancer “hallmarks”. It appears that an antiacidic approach, by targetting a driver phenotype in tumors, may be thought as a future strategy against tumors in either preventing the occurrence of cancer or treating tumor patients with multiple aims, including the improvement of efficacy of existing therapies, possibly reducing their systemic side effects, and controlling tumor growth, progression, and metastasis. This may be achieved with existing molecules such as proton pump inhibitors (PPIs) and buffers such as sodium bicarbonate, citrate, or TRIS.

Phototoxic effect of na-pheophorbide a toward osteosarcoma cells in vitro using a laser diode

OBJECTIVE

The purpose of this study was to investigate the effectiveness of photodynamic therapy (PDT) with Na-pheophorbide A in anticancer treatment, using osteosarcoma cells in vitro.

BACKGROUND DATA

It has been reported that PDT with chlorophyll derivatives inhibits the proliferation of various cancer cells. However, there have been no reports that have evaluated the effectiveness of PDT in suppressing osteosarcoma cells.

MATERIALS AND METHODS

Uptake of Na-pheophorbide A into Hu09 cells (osteosarcoma cells) was assayed using fluorescence microscopy following incubation of the cells with 28 μmol/L of Na-pheophorbide A. The viability of Hu09 cells after PDT treatment was assessed using trypan blue dye staining and MTS assays. PDT-induced apoptosis was determined by evaluation of the activity of selected members of the caspase family and by terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) staining of cells.

RESULTS

Na-pheophorbide A uptake by cells was rapid, being observed after 60 min of treatment, and Na-pheophorbide A persisted in cells for >24 h. PDT treatment decreased cell viability compared with the control group, indicating high cytocidal activity of PDT. This cytocidal effect was dependent upon drug concentration, light dose, and the number of irradiation times. An increase in the number of cells positive for TUNEL staining and increases in the activity of caspases-3, -8 and -9 were observed in the first 2 h after PDT treatment.

CONCLUSIONS

A cytotoxic effect of PDT with Na-pheophorbide A on an osteosarcoma cell line in vitro was shown. Caspase activity assays suggested that PDT with Na-pheophorbide A induced an apoptotic change in HuO9 cells, mainly via activation of mitochondrial caspase -9 and -3 pathways.

Progress of photodynamic therapy applications in the treatment of musculoskeletal sarcoma (Review)

Photodynamic therapy (PDT) has clinical approval for use as a minimally invasive therapeutic procedure that is able to exert selective cytotoxic activity toward pathological cells, particularly malignant cells. Following a number of recent technological improvements, PDT has been widely applied to the diagnosis and treatment of malignancies, including lung, esophageal, gastrointestinal, bladder, prostate, head and neck, oral and skin cancer. Studies have shown that osteosarcoma is a malignant tumor afflicting young adults worldwide, and recently, the incidence of bone and soft-tissue malignant tumors has been shown to be increasing, so the use of PDT has become an area of focus for the diagnosis and treatment of musculoskeletal sarcoma.

Can a less radical surgery using photodynamic therapy with acridine orange be equal to a wide-margin resection?

BACKGROUND

Wide-margin resections are an accepted method for treating soft tissue sarcoma. However, a wide-margin resection sometimes impairs function because of the lack of normal tissue. To preserve the normal tissue surrounding a tumor, we developed a less radical (ie, without a wide margin) surgical procedure using adjunctive photodynamic therapy and acridine orange for treating soft tissue sarcoma. However, whether this less radical surgical approach increases or decreases survival or whether it increases the risk of local recurrence remains uncertain.

QUESTIONS/PURPOSES

We determined the survival, local recurrence, and limb function outcomes in patients treated with a less radical approach and adjunctive acridine orange therapy compared with those who underwent a conventional wide-margin resection.

METHODS

We treated 170 patients with high-grade soft tissue sarcoma between 1999 and 2009. Fifty-one of these patients underwent acridine orange therapy. The remaining 119 patients underwent a conventional wide-margin resection for limb salvage surgery. We recorded the survival, local recurrence, and functional score (International Society of Limb Salvage [ISOLS]) score) for all the patients.

RESULTS

The 10-year overall survival rates in the acridine orange therapy group and the conventional surgery group were 68% and 63%, respectively. The 10-year local recurrence rate was 29% for each group. The 5-year local recurrence rates for Stages II, III, and IV were 8%, 36%, and 40%, respectively, for the acridine orange group and 13%, 27%, and 33%, respectively, for the conventional surgery group. The average ISOLS score was 93% for the acridine orange group and 83% for the conventional therapy group.

CONCLUSION

Acridine orange therapy has the potential to preserve limb function without increasing the rate of local recurrence. This therapy may be useful for eliminating tumor cells with minimal damage to the normal tissue in patients with soft tissue sarcoma.

LEVEL OF EVIDENCE

Level IV, therapeutic study. See Guidelines for Authors for a complete description of the levels of evidence.

Photodynamic therapy with acridine orange in musculoskeletal sarcomas

Limb salvage involving wide resection and reconstruction is now well established for managing musculoskeletal sarcomas. However, involvement of major nerves and vessels with a large volume of muscle and skin may result in a useless limb, contributing to depression and a low quality of life. We have been studying alternative treatments for musculoskeletal sarcoma since 1990, and have recently established a regime using photodynamic surgery with cells labelled with acridine orange, photodynamic therapy with cells treated similarly and radiodynamic treatment using the effect of X-rays on such cells. These techniques have been used after marginal or intralesional resection of tumours since 1999 and have enabled maintenance of excellent limb function in patients with sarcomas.

In vivo anti-tumor activity of photodynamic therapy with intravenous administration of acridine orange, followed by illumination with high-power flash wave light in a mouse osteosarcoma model

In a recent study, we demonstrated that a high-power flash wave light (FWL) from a xenon lamp exerted a stronger cytocidal effect against a mouse osteosarcoma cell line than continuous wave light (CWL) in photodynamic therapy with acridine orange (AO-PDT). Based on our in vitro results, we investigated the in vivo anti-tumor activity of AO-PDT using flash wave light from a xenon lamp in a mouse osteosarcoma model. Mouse osteosarcoma cells (LM8) were injected into the subcutaneous tissue of the back of C3H mice, and tumors that grew to approximately 3 mm in diameter were treated by AO-PDT using FWL. AO was administered by intravenous injection and 2 h later the entire body of the mouse was illuminated with FWL from a xenon lamp. Significant growth inhibition of the tumor xenografts was observed as compared with that in the control group, suggesting that AO-PDT with FWL may be useful in the treatment of osteosarcoma. An immunohistochemical study of the tumors treated by AO-PDT showed that the underlying mechanism of the tumor growth inhibition involved both apoptosis and necrosis. In conclusion, it appears that following the intravenous administration of AO, AO-PDT in combination with FWL exerts strong anti-tumor activity. Inhibitory effects against growth of the primary tumor in human patients with osteosarcoma as well as other musculoskeletal sarcomas were also observed.

A new limb salvage surgery in cases of high-grade soft tissue sarcoma using photodynamic surgery, followed by photo- and radiodynamic therapy with acridine orange

BACKGROUND

To maintain excellent limb function after tumor resection in patients with high-grade malignant sarcomas, we developed and established a new surgical adjuvant therapy using acridine orange (AO) after intra-lesional or marginal resection while sparing normal tissues of major nerves, vessels or bones adjacent to the tumor.

METHOD

Our AO therapy procedure was combined with photodynamic surgery (PDS), photodynamic therapy (PDT) and radiodynamic therapy (RDT). In this study, 26 patients with primary high-grade soft tissue sarcomas were treated with AO therapy.

RESULT

Results showed a low local recurrence rate (7.7%) and good local recurrence-free rate (88%) after AO therapy. Limb function of all patients was maintained at 100% of ISOLS criteria.

CONCLUSION

Based on these results, we concluded that AO therapy is useful for local control after margin-positive tumor resection and for preserving excellent limb function in patients with high-grade soft tissue sarcomas.

Photodynamic therapy with ATX-S10.Na(II) inhibits synovial sarcoma cell growth

Photodynamic therapy (PDT) is an effective cancer treatment modality that allows selective destruction of malignant tumor cells. We asked whether PDT could inhibit in vivo and in vitro growth of synovial sarcoma cells. We analyzed PDT using ATX-S10.Na(II) and a diode laser for a synovial sarcoma cell line (SYO-1). Photodynamic therapy with ATX-S10.Na(II) showed an in vitro cytotoxic effect on the cultured SYO-1 cells. The in vitro effect of PDT depended on the treatment concentration of ATX-S10.Na(II) and the laser dose of irradiation. ATX-S10.Na(II) was detected in the tumor tissue specimens that were excised from nude mice bearing SYO-1 within 6 hours after intravenous injection, but it was eliminated from the tumor 12 hours after injection. Photodynamic therapy suppressed the tumor growth of nude mice bearing SYO-1, and high-dose irradiation induced no viable tumor cells in histologic specimens. Photodynamic therapy performed after marginal resection of the tumor of nude mice bearing SYO-1 reduced the rate of local recurrence of the tumor. Our results suggest PDT using ATX-S10.Na(II) and laser irradiation may be a potentially useful treatment for synovial sarcoma, especially to reduce the surgical margin and preserve critical anatomic structures adjacent to the tumor.

Extracorporeal photodynamic image detection of mouse osteosarcoma in soft tissues utilizing fluorovisualization effect of acridine orange

Various imaging methods have been employed for the extracorporeal detection of malignant tumors in the human body, such as scintigraphy and PET; however, none is sufficiently accurate and all are also very expensive. To resolve these issues, we attempted to develop a new imaging technique of photodynamic diagnosis (PDD) with acridine orange (AO). AO has the ability to rapidly and specifically accumulate in malignant tumors and emit brilliant green fluorescence after blue light excitation. In this study, we investigated the feasibility of PDD utilizing the fluorovisualization effect of AO, for the extracorporeal detection of mouse osteosarcoma inoculated into the soft tissues. At 2 h after intravenous administration of 0.1, 0.2, 0.5, 1.0, 2.0 and 5.0 mg/kg AO, the tumor and the surrounding normal tissues were illuminated by blue light. The visual fluorescence contrast and ratio (X) of the difference in fluorescence intensity between the tumor and the surrounding normal tissues were evaluated using a high-resolution digital camera equipped with an absorption filter. In addition, the fluorescence contrast was also detected sequentially at 0.5, 1, 2, 3, 6 and 12 h after intravenous administration of AO at 1.0 mg/kg. The results revealed that the optimal condition for clear detection of the tumor was evaluation 2 h after intravenous injection of AO at 0.1 mg/kg, because it provided the best visual contrast on the digital images, and the fluorescence intensity as well as the value of X were higher as compared to the values under other conditions of dose and timing. Based on the results of an acute toxicity study of AO, the estimated LD50 of this substance following intravenous administration was 27.30 mg/kg. In conclusion, we believe that PDD using AO administered intravenously may be feasible for the detection of human musculoskeletal sarcomas in the soft tissues at extremities, and this technique might be a less invasive, less expensive, quicker and more accurate imaging modality than other previously reported imaging methods for this purpose.

Vesicle disruption, plasma membrane bleb formation, and acute cell death caused by illumination with blue light in acridine orange-loaded malignant melanoma cells

Acridine orange (AO), a weakly basic fluorescent dye, is permeable to plasma and vesicle membranes and preferentially remains in intracellular acidic regions. Using fluorescence microscopy, we observed dynamic changes in AO-loaded cultured malignant melanoma cells during illumination with blue light. Immediately after the start of the illumination, the successive disruption of vesicles was observed as a flash of fluorescence, and shortly after that, blebs were formed on the plasma membrane. These cells died within 5 min. Vesicle disruption was completely inhibited when cells were treated with the vacuolar H(+)-ATPase inhibitor bafilomycin A1 followed by loading with AO, but not when bafilomycin A1 was treated after AO loading. Thus, the filling of AO in the vesicle, which is driven by vacuolar H(+)-ATPase, is initially required for vesicle disruption. In contrast, bafilomycin A1 did not prevent plasma membrane blebbing, indicating that the blebs are formed independently of the vesicle disruption. Acute cell death was inhibited by treatment with bafilomycin A1 before but not after AO loading. Thus, AO- and blue light-induced acute cell death is associated with vesicle disruption rather than bleb formation. Both the vesicle disruption and the formation of plasma membrane blebs were inhibited by removal of oxygen from the cell environment and by singlet oxygen scavengers, sodium azide, ascorbic acid, and L-histidine, but not inhibited by the hydroxyl radical scavenger dimethyl thiourea. Acute cell death was also prevented by singlet oxygen scavengers but not by dimethyl thiourea. Thus, these phenomena are likely caused at least in part by the generation of singlet oxygen. The photosensitive features of plasma and vesicle membranes observed in the present study may be based on the use of the photodynamic effect, such as cancer therapy.

Intrinsic radiation resistance in human chondrosarcoma cells

Human chondrosarcomas rarely respond to radiation treatment, limiting the options for eradication of these tumors. The basis of radiation resistance in chondrosarcomas remains obscure. In normal cells radiation induces DNA damage that leads to growth arrest or death. However, cells that lack cell cycle control mechanisms needed for these responses show intrinsic radiation resistance. In previous work, we identified immortalized human chondrosarcoma cell lines that lacked p16(ink4a), one of the major tumor suppressor proteins that regulate the cell cycle. We hypothesized that the absence of p16(ink4a) contributes to the intrinsic radiation resistance of chondrosarcomas and that restoring p16(ink4a) expression would increase their radiation sensitivity. To test this we determined the effects of ectopic p16(ink4a) expression on chondrosarcoma cell resistance to low-dose gamma-irradiation (1-5 Gy). p16(ink4a) expression significantly increased radiation sensitivity in clonogenic assays. Apoptosis did not increase significantly with radiation and was unaffected by p16(ink4a) transduction of chondrosarcoma cells, indicating that mitotic catastrophe, rather than programmed cell death, was the predominant radiation effect. These results support the hypothesis that p16(ink4a) plays a role in the radiation resistance of chondrosarcoma cell lines and suggests that restoring p16 expression will improve the radiation sensitivity of human chondrosarcomas.

Mutagenic effect of acridine orange on the expression of penicillin G acylase and beta-lactamase in Escherichia coli

AIMS

The present work aimed to improve the production of penicillin G acylase (PGA) and reduce the beta-lactamase activity through acridine orange (AO) induced mutation in Escherichia coli.

METHODS AND RESULTS

Three wild E. coli strains BDCS-N-FMu10, BDCS-N-S21 and BDCS-N-W50, producing both the enzymes PGA and beta-lactamase were treated by AO. Minimum inhibitory concentration of AO was 10 microg ml(-1) and it was noted that bacterial growth was gradually suppressed by increasing the concentration of AO from 10 to 100 microg ml(-1). The highest concentration that gave permissible growth rate was 50 microg ml(-1). The isolated survivals were screened on the bases of PGA and beta-lactamase activities. Among the retained mutants, the occurrence of beta-lactamase deficient ones (91%) was significantly higher than penicillin acylase deficient ones (27%).

CONCLUSIONS

In seven of the mutants, PGA activity was enhanced with considerable decrease in beta-lactamase activity. One of the mutant strains (BDCS-N-M36) exhibited very negligible expression of beta-lactamase activity and twofold increase in PGA activity [12.7 mg 6-amino-penicillanic acid (6-APA) h(-1) mg(-1) wet cells] compared with that in the wild-type strain (6.3 mg 6-APA h(-1) mg(-1) wet cells).

SIGNIFICANCE AND IMPACT OF THE STUDY

The treatment of E. coli cells with AO resulted in mutants with enhanced production of PGA and inactivation of beta-lactamase. These mutants could be used for industrial production of PGA.

Tunable DNA Photocleavage by an Acridine−Imidazole Conjugate

We report the synthesis and characterization of photonucleases N,N'-bis[2-[bis(1H-imidazol-4-ylmethyl)amino]ethyl]-3,6-acridinediamine (7) and N-[2-[bis(1H-imidazol-4-ylmethyl)amino]ethyl]-3,6-acridinediamine (10), consisting of a central 3,6-acridinediamine chromophore attached to 4 and 2 metal-coordinating imidazole rings, respectively. In DNA reactions employing 16 metal salts, photocleavage of pUC19 plasmid is markedly enhanced when compound 7 is irradiated in the presence of either Hg(II), Fe(III), Cd(II), Zn(II), V(V), or Pb(II) (low-intensity visible light, pH 7.0, 22 degrees C, 8-50 microM 7). We also show that DNA photocleavage by 7 can be modulated by modifying buffer type and pH. Evidence of metal complex formation is provided by EDTA experiments and by NMR and electrospray ionization mass spectral data. Sodium azide, sodium benzoate, superoxide dismutase, and catalase indicate the involvement of type I and II photochemical processes in the metal-assisted DNA photocleavage reactions. Thermal melting studies show that compound 7 increases the Tm of calf thymus DNA by 10 +/- 1 degrees C at pH 7.0 and that the Tm is further increased upon the addition of either Hg(II), Cd(II), Zn(II), or Pb(II). In the case of Fe(III) and V(V), a colorimetric assay demonstrates that compound 7 sensitizes one electron photoreduction of these metals to Fe(II) and V(IV), likely accelerating the production of type I reactive oxygen species. Our data collectively indicate that buffer, pH, Hg(II), Fe(III), Cd(II), Zn(II), V(V), Pb(II), and light can be used to "tune" DNA cleavage by compound 7 under physiologically relevant conditions. The 3,6-acridinediamine acridine orange has demonstrated great promise for use as a photosensitizer in photodynamic therapy. In view of the distribution of iron in living cells, compound 7 and other metal-binding acridine-based photonucleases should be expected to demonstrate excellent photodynamic action in vivo.

Efficacy of combined photodynamic and hyperthermic therapy with a new light source in an in vivo osteosarcoma tumor model

OBJECTIVE

In this study, we investigated the efficacy of Super Lizer (SL) as a new light source in photodynamic therapy (PDT) with hyperthermia in an in vivo osteosarcoma tumor model.

MATERIALS AND METHODS

Nude mice in three study groups (PDT only, PDT with hyperthermia in low energy, and PDT with hyperthermia in high energy) and three control groups (no treatment, photosensitizer only, and hyperthermia only) were implanted subcutaneously with human osteosarcoma cells and injected with a photosensitizing hematoporphyrin derivative (HPD) at a total dose of 10 mg/kg, in all study groups and in control group 2. At 72 h after light treatment, mice were sacrificed.

RESULTS

The tumor volume growth rates in the heat-only (1.50) and PDT-only (1.40) groups were significantly lower than the growth rate in the no-treatment group (1.82). Further, the tumor volume growth rate in the PDT with hyperthermia in high-energy group (1.19) was significantly lower than in the heat- or PDT-only groups.

CONCLUSION

Although non-laser PDT, including SL-PDT, may be beneficial only in the treatment of superficial tumors because of limited light penetration, PDT combined with hyperthermia may extend the utility of PDT in antitumor treatment. The use of SL as a new light source in PDT may significantly advance antitumor therapy due to its simplicity, ease, and cost benefit.

Acridine orange excited by low-dose radiation has a strong cytocidal effect on mouse osteosarcoma

The study was conducted to clarify the cytocidal effect of combination therapy consisting of administration of acridine orange (AO), which is a photosensitizer, and radiation therapy using in vitro and in vivo mouse osteosarcoma models. The results revealed that AO combined with low-dose X-ray irradiation of about 1-5 Gy had a strong cytocidal effect on the cultured mouse osteosarcoma cells regardless of their chemosensitivity, and that this combination therapy inhibited growth of the in vivo mouse osteosarcoma by induction of tumor necrosis. This effect was inhibited by L-histidine, but not by mannitol. These findings suggested that AO might be excited by X-rays and kill osteosarcoma cells through the release of singlet oxygen, which is toxic to living cells. This mechanism is similar to that of photodynamic therapy with AO.