The authors would like to thank biolitec Research GmbH (Jena, Germany) for kindly providing us with the liposomal mTHPC formulation, with special thanks to Susanna Gr&#228;fe and Arno Wiehe for their help and technical expertise. We also would like to thank Kerstin Reidy, who generated a large part of the results and was coresponsible for its publication11.
This work was supported by grants from the Schweizerischer Verein Balgrist, the University of Zurich, the Krebsliga Zurich as well as by a grant from the Walter L. and Johanna Wolf Foundation, Zurich, Switzerland and a grant from EuroNanoMed ERA-NET &#8260;SNF Swiss National Science Foundation 31NM30-131004 &#8260; 1. This work was also supported by the HSM (Highly Specialized Medicine) program for Musculoskeletal Oncology of the Kanton Zurich.

1.&#160;Comparison of the Uptake of mTHPC in the Respective Low and Highly Metastatic HOS and 143B OS Cell Lines
<ol>
	<li>Prepare cell culture medium containing DMEM, Ham F12, and heat inactivated fetal calf serum in a ratio 4.5:4.5:1. 
	Note: The liposomal formulation of the PS mTHPC was dissolved in water at a final concentration of 1.5 mg/ml mTHPC.</li>
	<li>Plate 0.2 x 106 HOS and 143B cells/well in 6-well plates (triplicates for each condition) and let the cells adhere overnight.<...

<ol>
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To achieve optimal cytotoxicity in response to PDT, it is crucial to choose the right laser light settings and incubation times. The here described procedures are consistent and efficient to determine PS uptake and to quantify PDT induced cytotoxicity in vitro. Using the specific absorption wavelengths of the PS mTHPC, the cellular PS uptake can be determined in a direct manner, and the PS can be activated to generate cytotoxic reactive oxygen species.
Using this in vitro set...

Today&#8217;s state of the art treatment of osteosarcoma (OS), a primary bone tumor, encompasses a combination of neo adjuvant chemotherapy and surgery. This treatment regimen revealed an increase in the survival rate of patients with localized disease from approximately 20% before the use of chemotherapy, to currently between 60-70%3,4. However, in the last two decades, the overall survival of OS patients with local disease has plateaued4,5. Moreover, 30-40% of these patients relapse within 3 years after diagnosis and patients with metastatic disease continue to have a poor survival of 20-30%4,6,7. To improve the outcome of these patients, new therapeutic strategies need to be developed.
Photodynamic Therapy (PDT), a rather novel anticancer therapy, uses light of a specific wavelength for excitation of a photosensitizer (PS), which accumulates in the tumor cells after its injection into the bloodstream. Laser light excitation of the PS generates oxygen radicals in the presence of oxygen, which induce cytotoxic reaction in tumor cells and cell death. Besides this primary mechanism, two additional PDT evoked biological processes contribute to reduced tumor growth: PDT causes vasoconstriction and thrombus formation of the tumor microvasculature and, consequently local hypoxia and anoxia inside the tumor, leading to tumor infarction. Finally, PDT injured and dying tumor cells trigger a local immune response, a rather unique feature of PDT. This involves the complement system and the activation of antigen presenting dendritic cells8. Thus, conditions are created for the presentation of tumor antigens with subsequent activation of lymphoid cells, leading to tumor specific immunity.
So far, PDT has been used to treat several types of soft tissue tumors and hyperplasia&#8217;s, such as actinic keratosis, Barrett&#8217;s esophagus, endobronchial tumors, bladder cancer, basal cell carcinomas, and palliative treatment of head and neck cancer2. The treatment is known to induce local, large scale necrosis with only little side effects, and thus has the potential to selectively eradicate tumor tissue. Despite these advantages, the application of PDT remains technically more demanding than the administration of chemotherapeutic drugs. In order to achieve maximal efficacy, the PS concentration, light exposure time and total light energy transfer need to be optimized. This can be done in in vivo experiments, but, because of the relative large number of parameters that need to be optimized, it is more efficient to initially determine optimal conditions in vitro.
In the experiments described below, we tested the in vitro efficacy of PDT using the PS 5,10,15,20-tetrakis(meta-hydroxyphenyl)chlorin, abbreviated mTHPC (Figure 1A). mTHPC is the active substance in the medicinal product Foscan, which is currently used in the clinic for palliative treatment of head and neck cancer. It is one of the most potent PS, inducing massive cell damage already at low concentrations, and it was demonstrated to be superior to other PS in terms of tissue penetration9,10. Its light absorption spectrum (Figure 1B) shows two prominent peaks, one at 417 nm and a second at 652 nm, which are used for tissue localization of accumulating PS and for PDT induction, respectively.
Currently, a liposomal formulation for mTHPC is under development. Here, we describe the procedures to quantify the uptake of this liposomal formulation, and to perform PDT in two human OS cell lines; the low metastatic HOS and the high metastatic 143B cells. Some of the data presented here have been reported earlier11. The approach described here enables us to study the effect of a metastatic phenotype on PDT efficacy. 143B cells, orthotopically injected into the hind limbs of immune deficient SCID mice cause intratibial metastasizing primary tumors, a model closely mimicking the human metastasizing disease. Thus, the proposed in vitro experiments are perfectly suitable to assess the optimal PDT settings to be later used in in vivo experiments.

<table border="0" cellpadding="0" cellspacing="0" width="955">
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		<col />
		<col />
	</colgroup>
	<tbody>
		<tr height="21">
			<td height="21" style="height:21px;width:291px;">DMEM</td>
			<td style="width:251px;">PAA GmbH, Freiburg, Germany</td>
			<td style="width:127px;">E15-883</td>
			<td style="width:287px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:291px;">HAM F12</td>
			<td>PAA GmbH, Freiburg, Germany</td>
			<td style="width:127px;">E15-817</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:291px;">heat-inactivated fetal calf serum</td>
			<td>GIBCO, Basel, Switzerland</td>
			<td style="width:127px;">10500-064</td>
			<td></td>
		</tr>
		<tr height="147">
			<td height="147" style="height:147px;width:291px;">mTHPC</td>
			<td style="width:251px;">biolitec research GmbH, Jena, Germany</td>
			<td style="width:127px;"></td>
			<td style="width:287px;">As this liposomal formulation is originating from R &#38; D 
			no catalogue number is available at the moment. Stock: 1.5mg/ml; provided in a 9:1 mixture of dipalmitoylphosphatidylcholine (DPPC) and dipalmitoylphosphatidylglycerol (DPPG; &#62;99% purity)</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Spectramax Gemini XS plate reader</td>
			<td style="width:251px;">Molecular Devices, Sunnyvale, CA</td>
			<td style="width:127px;">ID# 861</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:291px;">Microscope Zeiss Observer.Z1</td>
			<td style="width:251px;">Axio Observer, Axio Vision Release 4.6.3 SP1, Jena Germany</td>
			<td style="width:127px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:291px;">Ceralas PDT 652 nm Laser</td>
			<td style="width:251px;">Biolitec AG, Jena, Germany</td>
			<td style="width:127px;">LD652nm2W400u</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:291px;">Water-soluble tetrazolium (WST) reagent</td>
			<td style="width:251px;">Roche Diagnostics AG, Rotkreuz, Switzerland</td>
			<td style="width:127px;">1644807</td>
			<td></td>
		</tr>
	</tbody>
</table>

cytotoxic efficacy of photodynamic therapy in osteosarcoma cells in vitro

In recent years, there has been the difficulty in finding more effective therapies against cancer with less systemic side effects. Therefore Photodynamic Therapy is a novel approach for a more tumor selective treatment.
Photodynamic Therapy (PDT) that makes use of a nontoxic photosensitizer (PS), which, upon activation with light of a specific wavelength in the presence of oxygen, generates oxygen radicals that elicit a cytotoxic response1. Despite its approval almost twenty years ago by the FDA, PDT is nowadays only used to treat a limited number of cancer types (skin, bladder) and nononcological diseases (psoriasis, actinic keratosis)2.
The major advantage of the use of PDT is the ability to perform a local treatment, which prevents systemic side effects. Moreover, it allows the treatment of tumors at delicate sites (e.g. around nerves or blood vessels). Here, an intraoperative application of PDT is considered in osteosarcoma (OS), a tumor of the bone, to target primary tumor satellites left behind in tumor surrounding tissue after surgical tumor resection. The treatment aims at decreasing the number of recurrences and at reducing the risk for (postoperative) metastasis.
In the present study, we present in vitro PDT procedures to establish the optimal PDT settings for effective treatment of widely used OS cell lines that are used to reproduce the human disease in well established intratibial OS mouse models. The uptake of the PS mTHPC was examined with a spectrophotometer and phototoxicity was provoked with laser light excitation of mTHPC at 652 nm to induce cell death assessed with a WST-1 assay and by the counting of surviving cells. The established techniques enable us to define the optimal PDT settings for future studies in animal models. They are an easy and quick tool for the evaluation of the efficacy of PDT in vitro before an application in vivo.

With the here reported techniques, we investigated mTHPC-based PDT in human OS cells. First, the time&#160; and dose dependent uptake of mTHPC was investigated in the low metastatic HOS and in the highly metastatic 143B OS cell lines. mTHPC uptake can be assessed by measuring the fluorescence of mTHPC with a fluorescence spectrophotometer (Figure 2, reproduced with permission from Reidy et al.11). Figure 2A illustrates the uptake of mTHPC in a time dependent manner. T...

Watch this Scientific Journal Video about Cytotoxic Efficacy of Photodynamic Therapy in Osteosarcoma Cells In Vitro at JoVE.com

Cytotoxic Efficacy of Photodynamic Therapy in Osteosarcoma Cells In Vitro

The protocol reported here allows the evaluation of the efficacy of photodynamic therapy (PDT) in cell lines and the optimization of the PDT settings before applying the therapy in animal models.

Cytotoxic Efficacy of Photodynamic Therapy in Osteosarcoma Cells In Vitro

In recent years, there has been the difficulty in finding more effective therapies against cancer with less systemic side effects. Therefore Photodynamic ...

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12.7K vistas.  Balgrist University Hospital, Zurich, Switzerland.  El protocolo informado aquí permite la evaluación de la eficacia de la terapia fotodinámica (PDT) en líneas de células y la optimización de la configuración de PDT antes de aplicar la terapia en modelos animales. 