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      Therapeutic implications of an enriched cancer stem-like cell population in a human osteosarcoma cell line

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          Abstract

          Background

          Osteosarcoma is a bone-forming tumor of mesenchymal origin that presents a clinical pattern that is consistent with the cancer stem cell model. Cells with stem-like properties (CSCs) have been identified in several tumors and hypothesized as the responsible for the relative resistance to therapy and tumor relapses. In this study, we aimed to identify and characterize CSCs populations in a human osteosarcoma cell line and to explore their role in the responsiveness to conventional therapies.

          Methods

          CSCs were isolated from the human MNNG/HOS cell line using the sphere formation assay and characterized in terms of self-renewal, mesenchymal stem cell properties, expression of pluripotency markers and ABC transporters, metabolic activity and tumorigenicity. Cell's sensitivity to conventional chemotherapeutic agents and to irradiation was analyzed and related with cell cycle-induced alterations and apoptosis.

          Results

          The isolated CSCs were found to possess self-renewal and multipotential differentiation capabilities, express markers of pluripotent embryonic stem cells Oct4 and Nanog and the ABC transporters P-glycoprotein and BCRP, exhibit low metabolic activity and induce tumors in athymic mice. Compared with parental MNNG/HOS cells, CSCs were relatively more resistant to both chemotherapy and irradiation. None of the treatments have induced significant cell-cycle alterations and apoptosis in CSCs.

          Conclusions

          MNNG/HOS osteosarcoma cells contain a stem-like cell population relatively resistant to conventional chemotherapeutic agents and irradiation. This resistant phenotype appears to be related with some stem features, namely the high expression of the drug efflux transporters P-glycoprotein and BCRP and their quiescent nature, which may provide a biological basis for resistance to therapy and recurrence commonly observed in osteosarcoma.

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          Most cited references31

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          The response of CD24(-/low)/CD44+ breast cancer-initiating cells to radiation.

          If cancer arises and is maintained by a small population of cancer-initiating cells within every tumor, understanding how these cells react to cancer treatment will facilitate improvement of cancer treatment in the future. Cancer-initiating cells can now be prospectively isolated from breast cancer cell lines and tumor samples and propagated as mammospheres in vitro under serum-free conditions. CD24(-/low)/CD44+ cancer-initiating cells were isolated from MCF-7 and MDA-MB-231 breast cancer monolayer cultures and propagated as mammospheres. Their response to radiation was investigated by assaying clonogenic survival and by measuring reactive oxygen species (ROS) levels, phosphorylation of the replacement histone H2AX, CD44 levels, CD24 levels, and Notch-1 activation using flow cytometry. All statistical tests were two-sided. Cancer-initiating cells were more resistant to radiation than cells grown as monolayer cultures (MCF-7: monolayer cultures, mean surviving fraction at 2 Gy [SF(2Gy)] = 0.2, versus mammospheres, mean SF(2Gy) = 0.46, difference = 0.26, 95% confidence interval [CI] = 0.05 to 0.47; P = .026; MDA-MB-231: monolayer cultures, mean SF(2Gy) = 0.5, versus mammospheres, mean SF(2Gy) = 0.69, difference = 0.19, 95% CI = -0.07 to 0.45; P = .09). Levels of ROS increased in both mammospheres and monolayer cultures after irradiation with a single dose of 10 Gy but were lower in mammospheres than in monolayer cultures (MCF-7 monolayer cultures: 0 Gy, mean = 1.0, versus 10 Gy, mean = 3.32, difference = 2.32, 95% CI = 0.67 to 3.98; P = .026; mammospheres: 0 Gy, mean = 0.58, versus 10 Gy, mean = 1.46, difference = 0.88, 95% CI = 0.20 to 1.56; P = .031); phosphorylation of H2AX increased in irradiated monolayer cultures, but no change was observed in mammospheres. Fractionated doses of irradiation increased activation of Notch-1 (untreated, mean = 10.7, versus treated, mean = 15.1, difference = 4.4, 95% CI = 2.7 to 6.1, P = .002) and the percentage of the cancer stem/initiating cells in the nonadherent cell population of MCF-7 monolayer cultures (untreated, mean = 3.52%, versus treated, mean = 7.5%, difference = 3.98%, 95% CI = 1.67% to 6.25%, P = .009). Breast cancer-initiating cells are a relatively radioresistant subpopulation of breast cancer cells and increase in numbers after short courses of fractionated irradiation. These findings offer a possible mechanism for the accelerated repopulation of tumor cells observed during gaps in radiotherapy.
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            Chemotherapy-resistant human AML stem cells home to and engraft within the bone-marrow endosteal region.

            Acute myelogenous leukemia (AML) is the most common adult leukemia, characterized by the clonal expansion of immature myeloblasts initiating from rare leukemic stem (LS) cells. To understand the functional properties of human LS cells, we developed a primary human AML xenotransplantation model using newborn nonobese diabetic/severe combined immunodeficient/interleukin (NOD/SCID/IL)2r gamma(null) mice carrying a complete null mutation of the cytokine gamma c upon the SCID background. Using this model, we demonstrated that LS cells exclusively recapitulate AML and retain self-renewal capacity in vivo. They home to and engraft within the osteoblast-rich area of the bone marrow, where AML cells are protected from chemotherapy-induced apoptosis. Quiescence of human LS cells may be a mechanism underlying resistance to cell cycle-dependent cytotoxic therapy. Global transcriptional profiling identified LS cell-specific transcripts that are stable through serial transplantation. These results indicate the potential utility of this AML xenograft model in the development of novel therapeutic strategies targeted at LS cells.
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              Osteosarcoma: a randomized, prospective trial of the addition of ifosfamide and/or muramyl tripeptide to cisplatin, doxorubicin, and high-dose methotrexate.

              To determine whether the addition of ifosfamide and/or muramyl tripeptide (MTP) encapsulated in liposomes to cisplatin, doxorubicin, and high-dose methotrexate (HDMTX) could improve the probability for event-free survival (EFS) in newly diagnosed patients with osteosarcoma (OS). Six hundred seventy-seven patients with OS without clinically detectable metastatic disease were treated with one of four prospectively randomized treatments. All patients received identical cumulative doses of cisplatin, doxorubicin, and HDMTX and underwent definitive surgical resection of the primary tumor. Patients were randomly assigned to receive or not to receive ifosfamide and/or MTP in a 2 double dagger 2 factorial design. The primary end point for analysis was EFS. Patients treated with the standard arm of therapy had a 3-year EFS of 71%. We could not analyze the results by factorial design because we observed an interaction between the addition of ifosfamide and the addition of MTP. The addition of MTP to standard chemotherapy achieved a 3-year EFS rate of 68%. The addition of ifosfamide to standard chemotherapy achieved a 3-year EFS rate of 61%. The addition of both ifosfamide and MTP resulted in a 3-year EFS rate of 78%. The addition of ifosfamide in this dose schedule to standard chemotherapy did not enhance EFS. The addition of MTP to chemotherapy might improve EFS, but additional clinical and laboratory investigation will be necessary to explain the interaction between ifosfamide and MTP.
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                Author and article information

                Journal
                BMC Cancer
                BMC Cancer
                BMC Cancer
                BioMed Central
                1471-2407
                2012
                4 April 2012
                : 12
                : 139
                Affiliations
                [1 ]Pharmacology and Experimental Therapeutics - Institute of Biomedical Research in Light and Image (IBILI), Faculty of Medicine, University of Coimbra, Az. de Sta. Comba, Celas, Coimbra 3000-354, Portugal
                [2 ]Center for Neurosciences and Cell Biology (CNC), Coimbra, Portugal
                [3 ]Center of Investigation in Environment, Genetics and Oncobiology (CIMAGO), Faculty of Medicine, University of Coimbra, Coimbra, Portugal
                [4 ]Histocompatibility Centre, University Hospital of Coimbra, Coimbra, Portugal
                [5 ]Radiotherapy Service, University Hospital of Coimbra, Coimbra, Portugal
                [6 ]Institute for Nuclear Sciences Applied to Health (ICNAS), University of Coimbra, Coimbra, Portugal
                Article
                1471-2407-12-139
                10.1186/1471-2407-12-139
                3351999
                22475227
                592665c5-66c7-48f7-af43-ae275e9e0a28
                Copyright ©2012 Martins-Neves et al; licensee BioMed Central Ltd.

                This is an Open Access article distributed under the terms of the Creative Commons Attribution License ( http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

                History
                : 16 December 2011
                : 4 April 2012
                Categories
                Research Article

                Oncology & Radiotherapy
                chemotherapy,osteosarcoma,cancer stem-like cells,radiotherapy,resistance
                Oncology & Radiotherapy
                chemotherapy, osteosarcoma, cancer stem-like cells, radiotherapy, resistance

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