BackgroundSkeletal metastasis is a common metastatic event for several carcinomas, and the treatment for skeletal metastasis of unknown primary (SMUP) are a critical issue in cancer therapy. Making a diagnosis of the primary site is the most crucial step in the treatment of SMUP; however, the procedures are sometimes difficult and time-consuming, and the primary site often remains unknown. Therefore, to establish optimal diagnostic strategies and elucidate the overall survival rates of SMUP, we conducted this retrospective study.MethodsWe retrospectively analyzed the clinical data for 286 SMUP cases from a total of 2,641 patients with skeletal metastases who were treated between 2002 and 2014 at our initiations.ResultsThe primary sites were identified in 254/286 patients (88.8%), while 32 (11.2%) primary sites were not detected by our diagnostic strategies. Lung cancer was identified in 72 (25.2%) cases, and was the most frequently observed primary lesion. The median survival time of the SMUP patients was 20.0 months, while the median survival times of solitary bone metastasis cases and multi-bone metastasis cases were 39.0 months and 16.0 months, respectively. The median survival times of prostate cancer cases was over 120 months, that of patients with primary lung cancers was 9.0 months and the median survival time of cases who were finally diagnosed with an unknown primary was 11.0 months.ConclusionsWe believe that our study would contribute to establishing an optimal strategy for diagnosing the primary site in SMUP patients, and our data provide definite indications for the survival times for different SMUP situations.

Ewing's sarcoma (ES) is the second-most frequent pediatric bone tumor. Chromosomal translocation t(11;22)(q24:q12) results in the formation of EWS/FLI1 gene fusion, which is detected in approximately 90% of tumors of the Ewing family. Several transcriptome studies have provided lists of genes associated with EWS/FLI1 expression. However, the protein expression profiles associated with EWS/FLI1 have yet to be elucidated. In this study, to identify the regulated proteins associated with EWS/FLI1 and therapeutic targets in ES, we conducted proteomic studies using EWS/FLI1 knockdown in four Ewing's sarcoma cell lines and human mesenchymal stem cells (hMSCs) expressing EWS/FLI1. Isobaric tags for relative and absolute quantitation (i-TRAQ) analyses identified more than 2,000 proteins regulated by the EWS/FLI1 fusion. In addition, the network analyses identified several critical pathways, including XBP1, which was ranked the highest. XBP1 is a protein well known to play an important role in the unfolded protein response (UPR) to endoplasmic reticulum (ER) stress through the IRE1α-XBP1 pathway. We confirmed the high mRNA expression of XBP1 (spliced XBP1 and unspliced XBPl) in surgical samples and cell lines in ES. The silencing of XBP1 significantly suppressed the cell viabilities in ES cell lines. In the inhibitor assays using IRE1α-XBP1 inhibitors, including toyocamycin, we confirmed that these agents significantly suppressed the cell viabilities, leading to apoptosis in ES cells both in vitro and in vivo. Our findings suggested that IRE1α-XBP1 inhibitors might be useful for developing novel therapeutic strategies in ES.

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Abstract. Recurrent hot-spot mutations in the telomerase reverse transcriptase (TERT) promoter have been reported in various types of tumor. In several tumor types, TERT promoter mutations are associated with poor clinical outcomes. TERT promoter mutations are reported to be rare in soft tissue tumors, with the exception of myxoid liposarcoma (MLS). Our previous study reported that TERT promoter mutations occurred in a subset of solitary fibrous tumors (SFTs) and were associated with adverse clinical outcomes in Japanese individuals. The site-specific frequency (e.g. central nervous or soft tissue origin) of TERT promoter mutations in our SFT cases appeared to be different from previously reported values in a European population. These findings prompted the present study to elucidate the potential role of ethnic background in the different frequencies of TERT promoter mutations in bone and soft tissue sarcomas. In the present study, TERT promoter mutations were examined in 180 cases of bone and soft tissue sarcomas. TERT promoter region mutations were identified in 10 cases [5 SFTs, 3 MLSs, 1 undifferentiated pleomorphic sarcoma (UPS) and 1 malignant granular cell tumor]. All mutations were C228T. The frequencies of TERT promoter mutation in MLS and UPS were 23.1 (3/13) and 5% (1/20), respectively. Only 1/5 patients with TERT-mutated tumors experienced local recurrence or distant metastasis. The present study revealed the first case of a malignant granular cell tumor with a TERT promoter mutation and revealed that the frequency of TERT promoter mutations in MLSs of Japanese patients is lower compared with that reported in German patients, providing evidence of a possible ethnic difference in the frequency of TERT promoter mutations.

Giant cell tumors of bone (GCTB) are locally aggressive osteolytic bone tumors. Recently, some clinical trials have shown that denosumab is a novel and effective therapeutic option for aggressive and recurrent GCTB. This study was performed to investigate the molecular mechanism underlying the therapeutic effect of denosumab. Comparative proteomic analyses were performed using GCTB samples which were taken before and after denosumab treatment. Each expression profile was analyzed using the software program to further understand the affected biological network. One of identified proteins was further evaluated by gelatin zymography and an immunohistochemical analysis. We identified 13 consistently upregulated proteins and 19 consistently downregulated proteins in the pre- and post-denosumab samples. Using these profiles, the software program identified molecular interactions between the differentially expressed proteins that were indirectly involved in the RANK/RANKL pathway and in several non-canonical subpathways including the Matrix metalloproteinase pathway. The data analysis also suggested that the identified proteins play a critical functional role in the osteolytic process of GCTB. Among the most downregulated proteins, the activity of MMP-9 was significantly decreased in the denosumab-treated samples, although the residual stromal cells were found to express MMP-9 by an immunohistochemical analysis. The expression level of MMP-9 in the primary GCTB samples was not correlated with any clinicopathological factors, including patient outcomes. Although the replacement of tumors by fibro-osseous tissue or the diminishment of osteoclast-like giant cells have been shown as therapeutic effects of denosumab, the residual tumor after denosumab treatment, which is composed of only stromal cells, might be capable of causing bone destruction; thus the therapeutic application of denosumab would be still necessary for these lesions. We believe that the protein expression patterns and the results of the network analysis will provide a better understanding of the effects of denosumab administration in patients with GCTB.