Aim

Propionibacterium acnes is an emerging pathogen especially in orthopedic implant infection. Interestingly, we previously reported a difference in the distribution of the clades involved in spine versus hip or knee prosthetic infection. To date, no study has previously explored the direct impact and close relationship of P. acnes on bone cells according to their own genetic background. The aim of this study was to investigate this interaction of P. acnes clinical strains involved in spine material infections, arthroplasty infections and acne lesions with bone cells.

The development of multidisciplinary therapy for Ewing’s sarcoma (ES) has increased current long-term survival rates to greater than 50%, but only 20% for patients with clinically detectable metastases at diagnosis, or not responding to therapy or with disease relapse. Anti-bone resorption bisphosphonates (BP) may represent promising adjuvant molecules to limit the osteolytic component of bone tumor.

The combination of zoledronic acid (ZOL) and ifosfamide (IFOS) or mafosfamide (MAFOS) was studied in ES models and in 8 human cell lines all expressing the EWS-FLI1 fusion gene. Cell proliferation, viability, apoptosis and cell cycle distribution were analysed. The ES models were developed in immuno-deficient mice by inoculating the human tumor cells either intra-muscular (soft tissue tumor development) or intra-osseous (bone tumor development). Mice were then treated with ZOL (100 μg/kg twice or 4 times/week) and/or ifosfamide (IFOS 30 mg/kg, one to 3 sequences of 3 injections).

All the cell lines studied were more or less sensitive to ZOL and MAFOS in terms of cell proliferation. Both drugs induced cell cycle arrest respectively in S and G2M phase and final apoptosis associated to caspase 3 activation. In vivo, ZOL had no effect on soft tumor progression although it dramatically inhibits ES development in bone site. When combined with IFOS, ZOL exerts synergistic effects in the soft tissue model leading to a similar quantitative inhibitory effect when associated with 1 sequence IFOS as compared to 3 sequences of IFOS alone. In the bone model, ZOL prevents tumor recurrence observed with a lonely sequence of IFOS.

Combination of ZOL with conventional chemotherapy showed promising results in both ES models and could allow the clinicians to diminish the doses of chemotherapy. Moreover, as ZOL and MAFOS induce cell death by different pathways, respective resistance may be circumvented.

Osteosarcoma is the most frequent malignant primary bone tumors. Despite recent improvements in multimodal therapy the problem of non-response to mono-chemotherapy remains. Therefore, novel multi-drug combinations targeting various molecular pathways are needed to decrease the emergence of resistance phenomenon and to potentiate the treatment efficacy. In this context, the effects of RAD001, a new orally available mTOR inhibitor was investigated in vitro and in vivo on osteosarcoma proliferation, both alone and in combination with Zoledronic acid (ZOL). The in vitro effects of ZOL and RAD001 were analyzed on human (MG63), rat (OSRGa) and mouse (POS-1 and MOS-J) osteosarcoma cell lines in terms of cell proliferation (XTT assay, manual cell counting, time-lapse microscopy), cell cycle analysis (flow cytometry analysis) and apoptosis (caspase 1, 3 and 8 activity). RAD001 and ZOL inhibit MG63, OSRGA and POS-1 osteosarcoma cell proliferation in a dose- and time-dependent manner without any modification of cell cycle distribution. In contrast, MOS-J cells are resistant to ZOL and RAD001. In all cell lines assessed, combination of RAD001 and ZOL exerts synergistic effect on the inhibition of cell proliferation and induces a significant decrease of P-mTOR, P-4EBP1 and Ras expression with no accumulation of IPP and ApppI. This drug combination has been then investigated in a mouse osteosarcoma model induced by i.m. inoculation of MOS-J cells in C57BL/6J mice. Clinical relevant doses of RAD001 (5 mg/kg) and ZOL (100 μg/kg) alone have no effect on tumor growth in contrast to combination of both drugs which decreases osteosarcoma progression. ZOL (alone or in combination) strongly increases bone formation. The combination of RAD001 with ZOL improves tissue repair as shown by important area of fibrosis into the residual tumor mass. The present work demonstrates the in vitro and in vivo synergistic effect of mTOR (RAD001) and mevalonate (ZOL) pathway inhibitors and suggests that ZOL potentiates RAD001 activity through Ras molecular pathway.

Purpose of the study: Wide en bloc surgical resection is the treatment of choice for cure of chondrosarcoma. Despite local control of this primary bone tumor in 60–80% of patients, mortality remains high. Recent studies suggest that biphosphonates can provide promising perspectives for the treatment of malignant bone tumors, even for primary tumors such as osteosarcoma. We report here the results obtained when using zoledronate for Swarm chondrosarcoma in an in vivo rat model and the effect of this compound on tumor cells in vitro.

Material and methods: Swarm chondrosarcoma was implanted in three series of 12 male Sprague Dawley rats. In series A, the animals were treated after implantation to death or sacrifice. In series B and C, the animals were treated a few days before curettage-resection then to death or sacrifice. Tumor growth was assessed by tumor size, presence of metastasis and death. Control series with PBS injections were also studied.

Results: Treatment with zoledronate inhibited tumor growth in all series. In series A, tumor size was significantly smaller in the treated animals (p=0.046). Tumor progression from day 19 to day 32 was significantly less for treated animals (p=0.046). Chance of survival was 0.667 for treated animals versus 0.3 for the controls. For series B and C, recurrence developed later in animals given zoledronate. Tumor size was greater in control animals compared with treated animals (p=0.043). Tumor progression from day 39 to day 49 was significantly greater in the control group (p=0.025). Cultures of cells extracted from the Swarm chondrosarcoma tumor also showed significantly inhibited growth in vitro for concentrations of zoledronic acid from 10 to 100 ml/l.

Discussion and conclusion: Zoledronic acid appears to inhibit growth of Swarm chondrosarcoma in all in vivo therapeutic schemas studied, confirming in vitro data. A more precise animal model better fitting clinical situations should provide more detailed information for use of this treatment after recurrence or in the event of intralesional surgery.

Purpose: In osteosarcoma, tumour progression leads to osteolysis via direct proteolytic mechanisms and/or osteoclast activation. Nitrogen biphosphonates (N-BP) like zolebronate inhibit osteoclast function and apoptosis of osteoclasts and other tumour cells. In animal models, N-BP decrease bony progression of myeloma, bone metastasis, and breast and prostatic tumours. In vitro studies have demonstrated a synergetic action with classical anti-cancer drugs on apoptosis for myeloma and breast cancer cell lines. The purpose of the present study was to investigate the effect of zoebronic acid on osteosarcoma growth, alone or in combination with ifosfamide.

Material and methods: A rat model accepting osteosarcoma transplant was used for the study. Four series of seven rats were treated with zoledronate (100 mg/kg on day 7, 14, 21 and 28 after implantation) in combination or not with ifosfamide (30 mg/kg on day 1”, 14 and 15). Thirty-five days after implantation, the rats were sacrificed to evaluate tumour volume, presence of metastasis, radiography, and pathological examination of the tumour. Zoledronate was also studied in vitro on an OSRGA osteosarcoma cell line isolated from the same tumour.

Results: Zoledronate demonstrated efficacy by reducing the osteolysis induced by the sarcoma, but also on local tumour progression (75%) in comparison with untreated animals. In vitro, zoledronate inhibited cell proliferation by 60%. The ifosfsamide-zoledrnoate combination produced greater reduction in tumour progression than ifosfamide alone.

Conclusion: This work demonstrates for the first time that zoledronate has an effect on osteosarcoma tumour progression, either by a direct effect or by an antiosteoclastic effect and that the effet increases the efficacy of classical antitumour drugs such as ifosfamide.