Osteosarcoma is the most common type primary malignant tumor of bone. Patients with regional osteosarcoma are routinely treated with surgery and chemotherapy. In addition, many patients with metastatic or recurrent osteosarcoma show poor prognosis with current chemotherapy agents. Therefore, it is important to improve the general condition and the overall survival rate of patients with osteosarcoma by identifying novel therapeutic strategies. Recent studies have revealed that CDK11 is essential in osteosarcoma cell growth and survival by inhibiting CDK11 mRNA expression with RNAi. Here, we apply the Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR)-Cas9 system, a robust and highly efficient novel genome editing tool, to determine the effect of targeting endogenous CDK11 gene at the DNA level in osteosarcoma cell lines. We show that CDK11 can be efficiently silenced by CRISPR-Cas9. Inhibition of CDK11 is associated with decreased cell proliferation and viability, and induces cell death in osteosarcoma cell lines KHOS and U-2OS. Furthermore, the migration and invasion activities are also markedly reduced by CDK11 knockout. These results demonstrate that CRISPR-Cas9 system is a useful tool for the modification of endogenous CDK11 gene expression, and CRISPR-Cas9 targeted CDK11 knockout may be a promising therapeutic regimen for the treatment of osteosarcoma.

Background:The major limitation to the success of chemotherapy in osteosarcoma is the development of multidrug resistance (MDR). Preventing the emergence of MDR during chemotherapy treatment has been a high priority of clinical and investigational oncology, but it remains an elusive goal. The NSC23925 has recently been identified as a novel and potent MDR reversal agent. However, whether NSC23925 can prevent the development of MDR in cancer is unknown. Therefore, this study aims to evaluate the effects of NSC23925 on prevention of the development of MDR in osteosarcoma.Methods:Human osteosarcoma cell lines U-2OS and Saos were exposed to increasing concentrations of paclitaxel alone or in combination with NSC23925 for 6 months. Cell sublines selected at different time points were evaluated for their drug sensitivity, drug transporter P-glycoprotein (Pgp) expression and activity.Results:We observed that tumour cells selected with increasing concentrations of paclitaxel alone developed MDR with resistance to paclitaxel and other Pgp substrates, whereas cells cultured with paclitaxel–NSC23925 did not develop MDR and cells remained sensitive to chemotherapeutic agents. Paclitaxel-resistant cells showed high expression and activity of the Pgp, whereas paclitaxel–NSC23925-treated cells did not express Pgp. No changes in IC50 and Pgp expression and activity were observed in cells grown with the NSC23925 alone.Conclusions:Our findings suggest that NSC23925 may prevent the development of MDR by specifically preventing the overexpression of Pgp. Given the significant incidence of MDR in osteosarcoma and the lack of effective agents for prevention of MDR, NSC23925 and derivatives hold the potential to improve the outcome of cancer patients with poor prognosis due to drug resistance.

Purpose: Survivin is one of the apoptosis inhibitor genes and is rarely expressed in adult ­tissues. However, survivin expression has been detected in various human cancers and ­correlations have been recognized between the level of expression of this gene in tumors and prognosis. In this study, we investigated the correlations between survivin mRNA expres­sion in osteosarcoma tissues and clinicopathological parameters.Methods: There were 22 osteosarcoma patients in our hospital with paraffin-embedded ­tissues which could be extracted from biopsy specimens. We used the RT-PCR method after extracting total RNA and conducted a densitometric analysis to determine the ratio of survivin relative to h-GAPDH as an internal marker.Results: Expression of survivin mRNA was detected in all osteosarcoma samples. Patients with metastasis had high survivin mRNA levels in initial biopsy specimens (p<0.01). Moreover, there was a statistically significant difference in survivin mRNA expression between ­patients with and without metastasis (p<0.01).Conclusion: We concluded that high levels of survivin mRNA expression suggest poor prognosis for osteosarcoma patients.

Our results suggest that large chordoma should be widely excised, using a modified threadwire saw, with a combination of anterior-posterior procedures.

Recent studies have revealed that expression of miRNA-1(miR-1) is frequently downregulated in several cancer types including chordoma. Identifying and validating novel targets of miR-1 is useful for understanding the roles of miR-1 in chordoma. We aimed to further investigate the functions of miR-1 in chordoma. Specifically, we assessed whether restoration of miR-1 affects cell migration and invasion in chordoma, and focused on the miR-1 potential target Slug gene. Migratory and invasive activities were assessed by wound healing and Matrigel invasion assays, respectively. Cell proliferation was determined by MTT assay. Slug expression was evaluated by Western blot, immunofluorescence, and immunohistochemistry. Restoration of miR-1 expression suppressed the migratory and invasive activities of chordoma cells. Transfection of miR-1 inhibited cell proliferation both time- and dose-dependently in chordoma. miR-1 transfected cells showed inhibited Slug expression. Slug was overexpressed in chordoma cell lines and advanced chordoma tissues. In conclusion, we have shown that miR-1 directly targets the Slug gene in chordoma. Restoration of miR-1 suppressed not only proliferation, but also migratory and invasive activities, and reduced the Slug expression in chordoma cells. These results collectively indicate that miR-1/Slug pathway is a potential therapeutic target because of its crucial roles in chordoma cell growth and migration.

Three of the 5 primary tumours had a benign clinical pattern and immunohistochemistry. Two of the 5 patients died of pulmonary metastases, which had an aggressive clinical pattern and a high prevalence of positive cells in Ki-67. Examination of Ki-67 should be carried out for aggressive type of giant cell tumour.

Reliable prognostic biomarkers for chordoma have not yet been established. Recent studies revealed that expression of miRNA-1(miR-1) is frequently downregulated in several cancer types including chordoma. The goal of this follow-up study is to investigate the expression of miR-1 as a prognostic biomarker and further confirm the functional role of miR-1 in chordoma cell growth and proliferation. We determined the relative expression levels of miR-1 and Met in chordoma tissue samples and correlated those to clinical variables. The results showed that miR-1 was downregulated in 93.7% of chordoma tissues and expression was inversely correlated with Met expression. miR-1 expression levels also correlated with clinical prognosis. To characterize and confirm the functional role of miR-1 in the growth and proliferation of chordoma cells, miR-1 precursors were stably transfected into chordoma cell lines UCH-1 and CH-22. Cell Proliferation Assay and MTT were used to evaluate cell growth and proliferation. Restoring expression of miR-1 precursor decreased cell growth and proliferation in UCH-1 and CH-22 cells. These results indicate that suppressed miR-1 expression in chordoma may in part be a driver for tumor growth, and that miR-1 has potential to serve as prognostic biomarker and therapeutic target for chordoma patients.

Survivin expression has been detected in various cancers and correlations have been recognized between the level of expression of this gene in tumors and prognosis. However, the aforementioned authors did not evaluate correlations between prognosis and survivin expression levels using surgically resected samples. In this study, we retrospectively investigated outcomes by examining the correlations between expression of this gene and clinicopathological parameters. Biopsy and resected specimens from which paraffin-embedded tissues could be extracted, were available from 16 patients in our hospital. We used the RT-PCR method and conducted a densitometric analysis to determine the ratio of survivin relative to h-GAPDH as an internal marker. Expression of survivin mRNA was detected in all samples. There was a significant negative correlation between survivin expression levels and duration of follow up, in months, using the Spearman's rank for the initial biopsy samples (rho¼À0.775, p<0.01) and those obtained after chemotherapy (rho¼À0.687, p<0.01). Moreover, Cox multivariate regression identified the survivin expression levels in both biopsy and post-chemotherapy samples as independent predictors of survival. We conclude that survivin levels in both initial biopsy and post-chemotherapy samples are useful prognostic indicators. ß