PurposeFeatures of epidermal growth factor receptor (EGFR) expression in osteosarcoma and in vitro efficacies of EGFR inhibitors against osteosarcoma cells were evaluated.Materials and MethodsThirty biopsy samples of osteosarcoma patients were retrospectively analyzed for EGFR protein expression by immunohistochemistry. Relationships between EGFR expression and clinicopathologic characteristics and treatment outcomes were evaluated. Four osteosarcoma cell lines were analyzed for EGFR and p-EGFR expression by western blotting. Efficacies of gefitinib and BIBW2992 on osteosarcoma cells were evaluated using a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. Tyrosine kinase domains in exons 18 to 21 were sequenced and gene expression analyses of EGFR and PTEN were performed in four osteosarcoma cell lines.ResultsEGFR protein was expressed in 27 (90%) samples (6 low, 12 intermediate, 9 high) and in three cell lines. Intermediate or high staining for EGFR was related to a tumor volume<150 mL (p<0.001) and histologic subtype other than osteoblastic type (p=0.03). However, EGFR expression was not associated with histologic response to preoperative chemotherapy or survival. Gefitinib and BIBW 2992 did not have any significant inhibitory effect on cell viabilities. DNA sequencing analysis revealed three osteosarcoma cell lines have single base changes at codon 2361 of exon 20 (G to A), without affecting translation results. Furthermore, no mutation was found to be associated with constitutive EGFR activation.ConclusionIn the present study, gefitinib and BIBW2992 were not effective against osteosarcoma cells. However, as osteosarcoma cells express EGFR, further studies are necessary to explore the potential of other therapeutic agents targeting EGFR.

BackgroundHumanized mouse models are still under development, and various protocols exist to improve human cell engraftment and function. MethodsFourteen NOD/SCID/IL-2Rnull (NSG) mice (4-5 wk old) were conditioned with busulfan and injected with human umbilical cord blood (hUCB)-derived CD34 + hematopoietic stem cells (HSC) via retro-orbital sinuses. The bone marrow (BM), spleen, and peripheral blood (PB) were analyzed 8 and 12 weeks after HSC transplantation. + T cells were barely detectable, while hCD7 + was detected in the BM and spleen. The percentage of hCD3 + T cells was 2-3% at week 12 in the BM, spleen, and PB of humanized NSG mice. Results Most of the ConclusionWe adopted a simplified protocol for establishing humanized NSG mice. We observed a higher engraftment rate of human CD45 + cells than earlier studies without any significant toxicity. And human CD45 + cell engraftment at week 8 was comparable to that of week 12.

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PurposePatients with unresectable, relapsed, or refractory osteosarcoma need a novel therapeutic agent. Metformin is a biguanide derivative used in the treatment of type II diabetes, and is recently gaining attention in cancer research.MethodsWe evaluated the effect of metformin against human osteosarcoma. Four osteosarcoma cell lines (KHOS/NP, HOS, MG-63, U-2 OS) were treated with metformin and cell proliferation was evaluated using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. Cell cycle progression and apoptosis were evaluated using flow cytometric analysis, and migration and wound healing assay were performed. Fourteen female Balb/c-nude mice received KHOS/NP cell grafts in their thigh, and were allowed access to metformin containing water (2 mg/mL) ad libitum. Tumor volume was measured every 3–4 days for a period of 4 weeks.ResultsMetformin had a significant antiproliferative effect on human osteosarcoma cells. In particular, metformin inhibited the proliferation and migration of KHOS/NP cells by activation of AMP-activated protein kinase and consequent inhibition of the mammalian target of rapamycin pathway. It also inhibited the proliferation of cisplatin-resistant KHOS/NP clone cells. Analysis of KHOS/NP xenograft Balb/c-nude models indicated that metformin displayed potent in vivo antitumor effects.ConclusionFurther studies are necessary to explore metformin's therapeutic potential and the possibilities for its use as an adjuvant agent for osteosarcoma.

Background/Aim: Osteosarcoma is the most common type of bone cancer, but current therapeutic interventions remain largely insufficient. The development of new treatment strategies is needed, and moreover, optimal rodent models are necessary for testing the efficacy of new treatment modalities of osteosarcoma. Humanized mice carry human hematopoietic and immune systems, and are considered an ideal tool to study human diseases including cancer immunology. Herein, we performed a preliminary study toward developing an in vivo bioluminescent osteosarcoma model using humanized immunodeficient (NSG) mice. Materials and Methods: To establish the xenograft and orthotopic mouse model, NSG mice engrafted with human CD34 + hematopoietic stem cells were injected with luciferaseexpressing KHOS/NP cells at two different time points. Bioluminescence images were obtained to monitor in vivo tumor growth and metastasis. Influence of the degree of human cell engraftment on tumor growth and metastatic behavior was analyzed and compared between the two groups. Results: KHOS/NP-luc cells injected in humanized NSG mice formed macroscopic tumors. The percentage of human CD45+ cells in these models was similar, but the percentage of human CD45+CD3+ and their subset was higher in the late-injection group compared to that of the early-injection group. The rate of KHOS/NP tumor growth was higher in the early-injection group than in the late-injection group. In the present study, human hematopoietic cell engraftment was not influenced by KHOS/NP cell injection, but KHOS/NP osteosarcoma showed more aggressive behavior in the early-injection group than that in the late-injection group, forming larger tumor volumes and earlier metastases. Conclusion: The results indicated that tumor growth and progression in humanized NSG mice may have been influenced by higher levels of human cell engraftment, especially T cells. Although there exist some limitations to our study, our preliminary results can provide the basis for the development of a humanized osteosarcoma mouse model. Osteosarcoma is the most common malignant bone tumor with a peak incidence occurring in adolescents. As the survival rate of patients with osteosarcoma has reached a plateau, the development of new treatment strategies based on its molecular characteristics are needed (1-3). As investigators search for novel agents, optimal in vitro or in vivo testing models are necessary. Animal models are widely used as preclinical platforms to test the efficacy of new treatment modalities. Due to the importance of bone and immune microenvironments in osteosarcoma, animal models recapitulating the human immune system are desirable in order to obtain more insight into the processes of osteosarcoma initiation, progression, and metastasis, as well as treatment sensitivity (4, 5). Super immunodeficient mice, such as NOD-scid IL2rγ null (NSG) mice, engraft human cells and tissues more efficiently than other models (6). Meanwhile, humanized mice carry human hematopoietic and immune systems and are co...