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Purpose: The implementation of targeted therapies for acute myeloid leukemia (AML) has been challenging. Fat mass and obesity associated protein (FTO), an mRNA N 6 -methyladenosine (m 6 A) demethylase, functions as an oncogene that promotes leukemic oncogene-mediated cell transformation and leukemogenesis. Here, we investigated the role of Saikosaponin-d (SsD) in broad anti-proliferation effects in AML and evaluated the m 6 A demethylation activity by targeting FTO of SsD. Methods: It was examined whether and how SsD regulates FTO/m 6 A signaling in AML. The pharmacologic activities and mechanisms of actions of SsD in vitro , in mice, primary patient cells, and tyrosine kinase inhibitors-resistant cells were determined. Results: SsD showed a broadly-suppressed AML cell proliferation and promoted apoptosis and cell-cycle arrest both in vitro and in vivo . Mechanistically, SsD directly targeted FTO, thereby increasing global m 6 A RNA methylation, which in turn decreased the stability of downstream gene transcripts, leading to the suppression of relevant pathways. Importantly, SsD also overcame FTO/m 6 A-mediated leukemia resistance to tyrosine kinase inhibitors. Conclusion: Our findings demonstrated that FTO-dependent m 6 A RNA methylation mediated the anti-leukemic actions of SsD, thereby opening a window to develop SsD as an epitranscriptome-base drug for leukemia therapy.

Hypoxia-inducible factor (HIF)-1␣ is a key nuclear transcription factor that regulates the cellular response to hypoxia, and is important for solid tumor growth and survival. However, the underlying role of HIF-1␣ in human chondrosarcoma has not been well characterized. This study aims to investigate the expression patterns of HIF-1␣ in chondrosarcoma, and its association with clinicopathologic features, Bcl-xL expression, apoptosis index (AI), and overall survival of patients with chondrosarcoma. Our results shown that the protein levels of HIF-1␣ were increased, and the mRNA and protein levels of Bcl-xL were also increased in SW1353 cells under hypoxic conditions. In eight patients with chondrosarcoma, increased expression of HIF-1␣ and Bcl-xL was detected in chondrosarcoma tissues compared with the paired adjacent normal tissues. Of 34 archival specimens of chondrosarcomas, 20 (58.8%) showed high HIF-1␣ protein expression as compared to benign cartilage tumors. Increased HIF-1␣ expression was correlated with a higher pathological grade and MSTS stage of chondrosarcoma. Moreover, HIF-1␣ expression was significantly associated with Bcl-xL expression and AI. More significantly, the survival rate of patients with HIF-1␣ high tumors was significantly lower than that of patients with HIF-1␣ low tumors. These findings suggest that increased HIF-1␣ levels mediated up-regulation of Bcl-xL play a prominent role in evasion of apoptosis and tumor progression, and can be predictive for the prognosis in human chondrosarcoma.

Clinical management of chondrosarcoma remains a challenging problem, largely due to the toxicity and resistance of this tumor to conventional chemotherapy. Programmed Cell Death 5 (PDCD5) is a protein that accelerates apoptosis in different cell types in response to various stimuli, and has been shown to be down-regulated in many cancer tissues. In this study, mRNA and protein levels of PDCD5 were found to be up-regulated in cisplatin-treated SW1353 chondrosarcoma cells compared with untreated cells. Recombinant human PDCD5 (rhPDCD5) was also shown to sensitize chondrosarcoma cells to cisplatin-based chemotherapy, with inhibition of cell growth and apoptosis detected both in vitro and in vivo. Increased expression of Bax and decreased expression of Bcl-2 were also observed, along with release of cytochrome c from mitochondria into the cytosol. Additionally, cleavage of caspase-9 and caspase-3, as well as the cleavage of poly (ADP-ribose) polymerase (PARP), were detected, suggesting that sensitization of chondrosarcoma cells involves the intrinsic mitochondrial apoptosis pathway. In vivo, the treatment of a xenograft model of chondrosarcoma with rhPDCD5 and cisplatin significantly inhibited tumor cell proliferation and induced apoptosis compared to treatment with cisplatin alone. Overall, these data provide a theoretical basis for the administration of rhPDCD5 and cisplatin for the treatment of patients with chondrosarcoma.

Elevated HIF-2α levels associated with low Beclin 1 expression play a role in the development of chondrosarcoma. Beclin 1 can serve as a novel biomarker to predict survival of chondrosarcoma patients, and may represent a potential therapeutic target.

The VHL tumor suppressor gene is frequently inactivated in several human tumors, including bone sarcomas. We previously identified that reduced expression of VHL protein is implicated in sarcomagenesis. However, the underlying biological functions of restored VHL protein expression have not been clearly elucidated in bone sarcomas. Here we initially constructed a recombinant adenovirus 5-VHL vector (Ad5-VHL) and evaluated its expression in bone sarcomas, and antitumor activity in vitro and in vivo. We found that the adenovirus-mediated increase of VHL significantly suppresses bone sarcoma cell growth, attributed to induction of apoptosis mediated by increased caspase-3 activity and modulated Bcl-2 protein family. This suppression effect involves inhibition of Wnt/β-catenin signaling and upregulation of GSK-3β. Moreover, Ad5-VHL showed a dramatic antitumor effect on a chondrosarcoma xenograft model. These findings establish that Ad5-VHL suppresses bone sarcoma cell growth by inhibiting Wnt/β-catenin signaling, and may be a novel target for gene-based therapy of bone sarcomas.