Chemotherapeutic agents have been used for the treatment of patients with Osteosarcoma (0s). However, inherent or acquired resistance to these agents is a serious problem in the management of 0 s patients. Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) is considered to induce apoptosis in a variety of cancer cells but not normal cells. In the present study, we examined whether chemotherapeutic agents enhance TRAIL-induced apoptosis in the sarcoma cell lines MG-63 and SaOS-2. Pretreatment with sub-toxic or slightly toxic concentrations of chemotherapeutic agents (cis-diammine dichloroplatinum, CDDP and doxorubicin, DXR) sensitized both cell lines to TRAIL-induced apoptosis, as assessed by the propidium iodide or Annexin V-Cy5 staining method. These cell lines expressed death receptors TRAIL-receptor 1 (TRAIL-R1) and TRAIL-R2, which were unaltered by treatment with CDDP, as assessed by flow cytometry. The decoy receptors TRAIL-R3 and -R4 were barely detected in both cell lines. CDDP down-regulated c-FLIP, tending to lower the activation threshold required for TRAIL-induced caspase-8 activation. The CDDP-pretreated cells indeed demonstrated more increased TRAIL-mediated caspase-8 activation, loss of mitochondrial membrane potential (AY',,,), and apoptosis than untreated cells. Consequently, the activated caspase-8 might lead to either activation of effector caspases such as caspase-3 or loss in AY,,,. Both the increased caspase activation and mitochondrial dysfunction induced by combination of CDDP and TRAIL would contribute to enhanced apoptotic cell death. The results of the present study would be valuable for the design of novel treatment modalities for patients with 0 s .

Soft tissue sarcoma (STS) is a malignant neoplasm, arising in mesenchymal tissues, that is difficult to treat clinically because it can be highly resistant to chemo-radiotherapy. At present, the mechanism of that resistance remains unclear. Cell cycle checkpoints engender strict control of cell proliferation, arresting the cell cycle to provide time for repair or apoptosis when DNA damage is induced by unprogrammed extrinsic events. These pathways involve at least two checkpoints: one at the G1/S transition and one at the G2/M transition. The p53 gene, which is mutated in several malignant tumors, plays an important role in DNA repair at the G1/S transition; however, there is little information on the G2/M checkpoint in STS. In the present study, several proteins (phospho-p53, -cdc25, -cdc2, -Chk1 and -Chk2) involved in checkpoint pathways were investigated using immunohistochemistry in STS specimens. Most STSs maintain a well-preserved G2/M checkpoint despite the loss of the G1/S checkpoint (phospho-p53: 4.9% (2/41); -cdc25: 41% (17/41); -cdc2: 61% (25/41); -Chk1: 29% (12/41); -Chk2: 46% (19/41)). Furthermore, in a postoperative chemotherapy case the number of cells positive for phospho-cdc25 and -Chk2 was higher in a recurrent tumor than in the primary tumor (n = 7, P = 0.046 < 0.05, Wilcoxon signed-ranks test). These findings indicate that the G2/M checkpoint pathway is well preserved and might contribute to the chemotherapeutic resistance associated with STS.

To investigate the frequency and mechanism of the peritumoral inflammatory reaction in chondroblastoma, we evaluated the relationship between clinicoradiological findings and immunohistochemical expression of cyclooxygenase-2 (COX-2) in excised tumors. Twenty-one cases of chondroblastoma were studied. Imaging analysis was performed with radiographs and T1- and T2-weighted magnetic resonance images in all cases and with computed tomography scan and bone scintigraphy in some cases. Immunohistochemical study for COX-2 was carried out using formalin-fixed paraffin-embedded tissues. Periosteal reaction was observed in 6 cases (29%) and bone marrow edema in 15 cases (71%). Soft-tissue edema, joint effusion, and synovitis were found in 10 cases (48%), in 7 cases (33%), and in 9 cases (43%), respectively. Immunohistochemical expression of COX-2 in chondroblastoma cells was found in 15 of 21 cases (71%). The intensity of COX-2 immunoreactivity was correlated statistically with the presence of periosteal reaction, bone-marrow edema, soft-tissue edema, and synovitis. Our results indicate that activation of eicosanoid synthesis by COX-2 expression in the tumor itself is probably an important factor, inducing peritumoral inflammatory changes in chondroblastomas.