The differential effects of the radioprotectant drugs amifostine and sodium selenite treatment in combination with radiation therapy on constituent bone cells, ewing's sarcoma of bone tumor cells, and rhabdomyosarcoma tumor cells in vitro

Abstract

The purpose of this study was to determine the differential effects of therapeutic X-radiation on constituent bone cells relative to the pediatric tumor cells: Ewing's sarcoma of bone and rhabdomyosarcoma. In addition, the radioprotectant drugs amifostine and sodium selenite were administered to constituent bone cells and the two tumor cells to determine if the radioprotectants differentially protect bone cells while not benefiting the tumor cells. These studies are a necessary first step in determining the potential clinical benefit of radioprotective therapy. An established in vitro cell culture model employing both constituent bone cells (osteoblasts, primary bone marrow monocytes, osteoclasts chondrocytes, and endothelial cells) and the tumor cells lines (Ewing's sarcoma of bone and rhabdomyosarcoma) were exposed to irradiation, amifostine, and sodium selenite. Cells were then assayed for changes in cell number, cytotoxicity, mineralization, bone resorption, cell attachment, osteocalcin, caspase-3 expression, clonogenic survival, and alkaline phosphatase expression. Radiation therapy differentially decreased cell number; with osteoblasts being shown to be the least sensitive to irradiation, the tumor cells had an intermediate sensitivity and monocytes were the most sensitive. Both amifostine and sodium selenite protected chondrocytes and osteoblasts from the negative effects of irradiation, while not protecting the tumor cells. The pediatric tumor cell lines were generally more radiosensitive than the bone cells examined. The radioprotectant drugs amifostine and sodium selenite provided significant radioprotection to constituent bone cells while not protecting the tumor cells. Finally, amifostine and sodium selenite therapy provided an additional benefit beyond radioprotection by increasing cytotoxicity in nonirradiated and irradiated tumor cells. ß

SHIP1 Regulates MSC Numbers and Their Osteolineage Commitment by Limiting Induction of the PI3K/Akt/β-Catenin/Id2 Axis

“…OIM was composed of b-glycerol 2-phosphate (BGP, 4 mM, Cat: G9891; Sigma) and 2-phospho-l-ascorbic acid (25 mg/mL, Cat: A8960; Sigma) for 14 days, with media changed every 2 days. To assay for formation of mineral nodules, plates were stained with 1% Alizarin red S solution (pH 4.2) [29]. For inhibitor studies, these cells were pretreated for 1 h prior to induction with b-catenin inhibitor, CCT031374 [30] at 20 mM concentration and PI3K/mTOR inhibitor, NVP-BEZ235 at 10 nM concentration [31] respectively.…”

“…Bone marrow-derived monocytes (BMM) expanded through M-CSF treatment were then cultured (1 · 10 6 cells/well) with 25 ng/mL recombinant receptor activator of nuclear factor kappa-B ligand (RANKL) (R&D Systems) and 25 ng/mL M-CSF for *14 days, with media changes every 2 days. Multinucleate OCs were stained with the tartrate-resistant acid phosphatase (TRAP) (Acid Phosphatase, Leukocyte Kit; Sigma) [29]. Multinucleate, TRAP-positive OCs were subsequently counted using a modification of Cavalieri's sampling method and the fractionator to generate an unbiased estimate of the numbers of OCs within each tissue-culture well [32,33].…”

Sodium Selenite-Induced Apoptosis Mediated by ROS Attack in Human Osteosarcoma U2OS Cells

“…The drugs commonly used for treatment include methotrexate, cisplatin, adriamycin, and ifosfamide. SSE protects chondrocytes and osteoblasts from the negative effects of irradiation while targeting tumor cells including Ewing's sarcoma of bone and rhabdomyosarcoma [15]. While low doses of SSE treatment (about 0.01-10 μM) do not produce significant cytotoxic responses against human osteosarcoma U2OS cells, pretreatment with low doses could increase the cytotoxicity of cisplatin to the cells [16].…”

Ewing's sarcoma of bone tumor cells produces MCSF that stimulates monocyte proliferation in a novel mouse model of Ewing's sarcoma of bone

“…We also hypothesized that the efficacy of XRT to treat ESB may be due the radio-sensitivity of monocytes in parallel with the radio-sensitivity of ESB, consistent with previous data. (16) Here we report that ESB tumor expansion in bone is driven by increased osteoclastic bone re-absorption due to increased numbers of monocytes, using a novel in vivo mouse model of ESB tumor progression. We also identify that the increase in monocyte numbers is due to the expression of MCSF produced by ESB tumor cells; with the application of XRT resulting in decreased tumor burden and corresponding monocyte numbers.…”

“…Monocytes and ESB are highly sensitive to XRT; with our previous in vitro work identifying the specific XRT-dose sensitivity, or D 0 -value, in both monocytes (0.94-Gy) and ESB (1.14-Gy). (16) Further, the loss of monocytes after 17.5-Gy XRT in vivo resulted in decreased numbers of osteoclasts and increased bone mass. (7) …”