Osteosarcoma is the most common primary bone tumor and poor prognosis for osteosarcoma patients is mainly due to chemotherapy resistance. MicroRNAs are important to maintain pathophysiological mechanisms of cancer and influence cell sensitivity to chemotherapy. In this study, we tested the functions of microRNA-21 for malignant features as well as for drug resistance of osteosarcoma. We used Northern blot to measure microRNA-21 levels in osteosarcoma-derived cell lines. MicroRNA-21 activity was modulated by either expressing a sponge to decrease its activity in an osteosarcoma-derived cell line expressing high levels of microRNA-21 or by introducing pri-microRNA-21 in a cell line with low endogenous levels. Cell migration was determined in a scratch assay and cell proliferation was measured by performing growth curve analysis. Sensitivity of the cells towards chemotherapeutics was investigated by performing cell viability assays and calculating the IC50 values. While cell migration was unaffected by modulated microRNA-21 levels, microRNA-21 inhibition slowed proliferation and exogenously expressed microRNA-21 promoted this process. Modulated microRNA-21 activity failed to effect sensitivity of osteosarcoma-derived cell lines to doxorubicin or methotrexate. Contrarily, reduction of microRNA-21 activity resulted in enhanced resistance towards cisplatin while ectopic expression of microRNA-21 showed the opposite effect. Increased microRNA-21 levels repressed the expression of Sprouty2 and ectopic expression of Sprouty2 was able to largely rescue the observed effects of microRNA-21 in osteosarcoma. In summary, our data indicate that in osteosarcoma microRNA-21 expression is an important component for regulation of cell proliferation and for determining sensitivity to cisplatin.

Purpose Haemophilic pseudotumour was defined by Fernandez de Valderrama and Matthews as a progressive cystic swelling involving muscle, produced by recurrent haemorrhage into muscles adjacent to the bone. The pseudotumour mainly occurs in the long bones and the pelvis. The treatment of the haemophilic pseudotumour poses a challenge, and extensive clinical experience is essential to appropriately address this serious complication in patients with haemophilia. Consequently, the aim of this study is to present our own clinical experience and treatment results of the haemophilic pseudotumour. Methods We retrospectively reviewed the records of 87 patients with bleeding disorders treated between 1967 and 2011 for musculoskeletal complications of congenital bleeding disorders. We identified six patients with a haemophilic pseudotumour who were treated at our department. Results The mean age at surgery was 45.9 (range, 40-61) years. The iliac bone was affected in three patients (one right, two left), the right tibia (distal diaphysis) in one, the right thigh in two and the right ulna (proximal part) in one patient. One patient had two pseudotumours. The perioperative course was easily controllable with adequate factor VIII substitution. At the latest follow-up after 8.4 (range, 4-24) years, normal healing with no recurrence was observed. Conclusions The haemophilic pseudotumour is a rare but severe complication of hereditary bleeding disorders. In the international literature the resection and postoperative course are described as challenging and difficult, requiring detailed preoperative planning. It is advisable to perform such operations in specialised centres with close cooperation between surgeons and haematologists.

Level IV, retrospective study.

No abstract