Edited by: Priscilla Pui Lam Chiu, The Hospital for Sick Children, Canada
Reviewed by: Richard Keijzer, University of Manitoba, Canada; Priscilla Pui Lam Chiu, The Hospital for Sick Children, Canada; Roshni Dasgupta, Cincinnati Children’s Hospital, USA
This article was submitted to Pediatric Surgery, a section of the journal Frontiers in Pediatrics.
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Ewing’s sarcoma (ES) is a primitive neuroectodermal tumor and is the second most common bone tumor in children and young adults (ages 5–30) (
A growing amount of preclinical research has been completed investigating the potential role of bone marrow derived mesenchymal stromal cell (MSC) therapy for the treatment multiple forms of cancer. By definition, MSCs are multipotent and have the capacity for self renewal (
Preliminary research using an ES model has shown the successful intravenous delivery of MSCs transfected with a gene for the anti tumorigenic protein interleukin 12 (IL-12). The transplanted MSCs were found to engraft at tumor sites and increase local IL 12 production leading to a decrease in tumor burden (
The design of future studies to investigate the potential use of MSC therapy for ES requires the development of tested animal models. Therefore, we evaluated the effect of intravenous MSC injection on both primary and metastatic tumor sites using a novel ES model (
All procedures were approved by the institutional animal care and use committee and were consistent with the National Institutes of Health’s Guide for the Care and Use of 13 Laboratory Animals (HSC-AWC-07-031).
TC71 human ES cells transfected with a luciferase reporter were injected in the rib of nude female mice. As previously described, our model is associated with a 60% incidence of chest wall tumors alone, 30% incidence of pulmonary metastasis alone, and 10% incidence of synchronous chest wall and pulmonary metastatic tumors (
The ES model has been described in a previous publication (
TC71 human ES cells were cultured as previously described (
Mesenchymal stromal cells were isolated from the bone marrow of Sprague-Dawley rats and expanded in MAPC media as previously described (
The rationale for using 1 × 106 MSCs is based on previous experience with the use of MSCs in a non-tumor model. These amount of MSC cells were adequate to detect in all organs. Because it is technically easier to isolate rat MSCs, compared to mice, rat MSCs are used in this study.
Mesenchymal stromal cells were removed from culture plates with 1X trypsin and washed with PBS. Next, the cells were suspended in PBS at a concentration of 1 million MSCs per milliliter of PBS and placed on ice until injection. After induction of anesthesia, the tail vein was cleansed with betadine and 1 million MSCs were injected. MSC injections were completed 1, 2, and 3 weeks after ES implantation. There were 15 mice in each group; one central group injected with PBS; one central group injected with lung and epithelial cells (CRL2300); and one treatment group.
After the injection of cells, the mice were imaged at different time points using an
After orthotopic Ewing’s chest wall tumors were established, MSCs were isolated, labeled, and delivered intravenously. Unexpectedly, the “naked” MSCs caused reduction in size of primary tumors and more so, lung metastasis.
First, we show MSCs exclusively home to the site of the tumor. Figure
Figure
We then wanted to identify the exact location microscopically of the MSCs in relationship to the primary tumor cells and MSCS in each organ. Organ explants from mice given MSCs were compared to mice in which lung epithelial cells (CRL2300) were delivered as controls. Figure
In animals with lung metastasis, after MSC delivery (f), MSCs infiltrate the lung parenchyma surrounding the tumor. No lung epithelial cells (d, e) and some MSCs (h, i) are seen infiltrating the primary tumors (red). Microscopically, the MSCs home to the lung metastasis more than the primary tumor.
We then evaluated the longevity of MSC engraftment. Figure
Mesenchymal stromal cell therapy resulted in a decrease in the volume of lung metastasis after 3 weeks of treatment. Significantly, less tumor is seen in the lung metastasis of the mice treated with MSC therapy compared to those treated with control lung epithelial cells (Figure
Preliminary research into the potential role of MSC therapy for ES has shown promise; (
Fischer et al. have shown that the intravenous injection of MSCs results in a significant first-pass pulmonary effect leading to the majority of MSCs being sequestered within the lung parenchyma (
Since we are the first to show this effect of MSCs on lung malignancies, we plan more research on the etiology. Other authors have shown in carcinomas, MSCs can actually exacerbate tumor growth; specifically in breast carcinomas (
Mesenchymal stromal cells could be seen in the lung at 5 days after the injection. Since the MSCs were delivered weekly, we don’t know how long they would be present in the lung. In the future, we anticipate isolating the patient’s own MSCs from their bone marrow, and determining by Magnetic Resonance Imaging (MRI), how long they remain in the lung. Sequential MRI exams could also detect the effect of the MSCs in reduction or stabilization of lung metastasis.
It was unexpected that the “naked” MSCs were able to significantly decrease lung metastasis. This is the first time MSC treatment has been demonstrated to reduce lung metastasis or any other lung tumors. As a next step, we plan to transfect the MSCs with ES specific targeted therapy to afford further reduction in disease.
The intravenous injection of MSCs offers a novel potential therapy for ES pulmonary metastasis. Our data show that the intravenous injection of MSCs in an ES model decreases the volume of pulmonary metastatic lesions. This is the first description of successful MSC therapy of lung tumors.
The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.