XI-006 induces potent p53-independent apoptosis in Ewing sarcoma.

There is an imperious need for the development of novel therapeutics for the treatment of Ewing sarcoma, the second most prevalent solid bone tumour observed in children and young adolescents. Recently, a 4-nitrobenzofuroxan derivative, XI-006 (NSC207895) was shown to diminish MDM4 promoter activity in breast cancer cell lines. As amplification of MDM4 is frequently observed in sarcomas, this study examined the therapeutic potential of XI-006 for the treatment of Ewing and osteosarcoma. XI-006 treatment of Ewing and osteosarcoma cell lines (n = 11) resulted in rapid and potent apoptosis at low micro-molar concentrations specifically in Ewing sarcoma cell lines (48 hr IC50 0.099-1.61 µM). Unexpectedly, apoptotic response was not dependent on MDM4 mRNA/protein levels or TP53 status. Alkaline/neutral comet and γH2AX immunofluorescence assays revealed that the cytotoxic effects of XI-006 could not be attributed to the induction of DNA damage. RNA expression analysis revealed that the mechanism of action of XI-006 could be accredited to the inhibition of cell division and cycle regulators such as KIF20A and GPSM2. Finally, potent synergy between XI-006 and olaparib (PARP inhibitor) were observed due to the down-regulation of Mre11. Our findings suggest that XI-006 represents a novel therapeutic intervention for the treatment of Ewing sarcoma.

Nutlin-3a efficacy in sarcoma predicted by transcriptomic and epigenetic profiling.

Nutlin-3a is a small-molecule antagonist of p53/MDM2 that is being explored as a treatment for sarcoma. In this study, we examined the molecular mechanisms underlying the sensitivity of sarcomas to Nutlin-3a. In an ex vivo tissue explant system, we found that TP53 pathway alterations (TP53 status, MDM2/MDM4 genomic amplification/mRNA overexpression, MDM2 SNP309, and TP53 SNP72) did not confer apoptotic or cytostatic responses in sarcoma tissue biopsies (n = 24). Unexpectedly, MDM2 status did not predict Nutlin-3a sensitivity. RNA sequencing revealed that the global transcriptomic profiles of these sarcomas provided a more robust prediction of apoptotic responses to Nutlin-3a. Expression profiling revealed a subset of TP53 target genes that were transactivated specifically in sarcomas that were highly sensitive to Nutlin-3a. Of these target genes, the GADD45A promoter region was shown to be hypermethylated in 82% of wild-type TP53 sarcomas that did not respond to Nutlin-3a, thereby providing mechanistic insight into the innate ability of sarcomas to resist apoptotic death following Nutlin-3a treatment. Collectively, our findings argue that the existing benchmark biomarker for MDM2 antagonist efficacy (MDM2 amplification) should not be used to predict outcome but rather global gene expression profiles and epigenetic status of sarcomas dictate their sensitivity to p53/MDM2 antagonists.

Pre-activation of the p53 pathway through Nutlin-3a sensitises sarcomas to drozitumab therapy.

The present study evaluated the efficacy of drozitumab, a human monoclonal agonistic antibody directed against death receptor 5 (DR5), as a new therapeutic avenue for the targeted treatment of bone and soft-tissue sarcomas. The antitumour activity of drozitumab as a monotherapy or in combination with Nutlin-3a was evaluated in a panel of sarcoma cell lines in vitro and human sarcoma patient samples ex vivo. Knockdown experiments were used to investigate the central role of p53 as a regulator of drozitumab cytotoxicity. Pre-activation of the p53 pathway through Nutlin-3a upregulated DR5, subsequently sensitising sarcoma cell lines and human sarcoma specimens to the pro-apoptotic effects of drozitumab. Silencing of p53 strongly decreased DR5 mRNA expression resulting in abrogation of drozitumab-induced apoptosis. Our study provides the first pre-clinical evaluation of combination therapy using p53-activating agents with drozitumab to further sensitise sarcomas to the cytotoxic effects of DR5 antibody therapy.

Low risk of cardiac events during intramedullary instrumentation of lung cancer metastases.

BACKGROUND: Instrumentation, particularly reaming, of the long bones carries the risk of embolic phenomenon. Emboli may result in pulmonary injury, which is usually manifested by desaturation. This pulmonary injury may be particularly relevant if there is diminished pulmonary reserve due to pre-existing lung disease such as lung carcinoma. In extreme cases, this can result in cardiac arrest intraoperatively. PATIENTS AND METHODS: We reviewed 34 consecutive operations that involved instrumentation of long bones for metastases of lung carcinoma. RESULTS: Desaturation developed during 1 procedure, and there was hypotension in 5 patients. In addition, cardiac arrest occurred intraoperatively in 1 patient, which was the only fatality. INTERPRETATION: This study has shown that while emboli during femoral instrumentation may be common, significant clinical manifestations of this phenomenon are uncommon.

Lytic bone lesions in an Australian population: the results of 100 consecutive biopsies.

BACKGROUND: The identification of a lytic bone lesion is often perceived as a harbinger of malignancy, especially in an older patient. This study reviews the results of 100 consecutive biopsies of patients who presented with either a solitary lesion or multiple lytic bone lesions in the absence of a history of malignancy. METHODS: Following preoperative planning, including plain radiographs, bone scan and computed tomography scanning, an open biopsy was carried out. RESULTS: The most common site affected was the pelvis (20 patients), followed by the femur (19) and tibia (15). The lesions were solitary in 88 patients and multiple in 12. The most common diagnosis was a secondary carcinoma presenting as a bone lesion, which was found in 25 patients. The carcinomas were a widely distributed group, but the most common among them were renal cell carcinoma (seven patients), breast carcinoma (five patients) and lung carcinoma (five patients). The most common primary bone tumour was a giant cell tumour (16) followed by myeloma (10). Multiple lesions were not universally an indication of a malignant process. In 14 patients the lesion was not a tumour. CONCLUSION: This study emphasizes the importance of obtaining a tissue diagnosis.