MicroRNA-221 promotes cisplatin resistance in osteosarcoma cells by targeting PPP2R2A

Osteosarcoma (OS), the most common malignant bone tumor, is the main cause of cancer-related deaths in children and young adults. Despite the combination of surgery and multi-agent chemotherapy, patients with OS who develop resistance to chemotherapy or experience recurrence have a dismal prognosis. MicroRNAs (miRNAs) are a class of small noncoding RNAs that repress their targets by binding to the 3′-UTR and/or coding sequences, leading to the inhibition of gene expression. miR-221 is found to be up-regulated in tumors when compared with their matched normal osteoblast tissues. We also observed significant miR-221 up-regulation in the OS cell lines, MG-63, SaoS-2, and U2OS, when compared with the normal osteoblast cell line, HOb. Overexpression of miR-221 promoted OS cell invasion, migration, proliferation, and cisplatin resistance. MG-63 and SaoS-2 cells transfected with miR-221 mimics were more resistant to cisplatin. The IC50 of MG-63 cells transfected with control mimics was 1.24 μM. However, the IC50 of MG-63 cells overexpressing miR-221 increased to 7.65 μM. Similar results were found in SaoS-2 cells, where the IC50 for cisplatin increased from 3.65 to 8.73 μM. Thus, we report that miR-221 directly targets PP2A subunit B (PPP2R2A) in OS by binding to the 3′-UTR of the PPP2R2A mRNA. Restoration of PPP2R2A in miR-221-overexpressing OS cells recovers the cisplatin sensitivity of OS cells. Therefore, the present study suggests a new therapeutic approach by inhibiting miR-221 for anti-chemoresistance in OS.

Oncogenic role of SFRP2 in p53-mutant osteosarcoma development via autocrine and paracrine mechanism

Osteosarcoma (OS), the most common primary bone tumor, is highly metastatic with high chemotherapeutic resistance and poor survival rates. Using induced pluripotent stem cells (iPSCs) generated from Li–Fraumeni syndrome (LFS) patients, we investigate an oncogenic role of secreted frizzled-related protein 2 (SFRP2) in p53 mutation-associated OS development. Interestingly, we find that high SFRP2 expression in OS patient samples correlates with poor survival. Systems-level analyses identified that expression of SFRP2 increases during LFS OS development and can induce angiogenesis. Ectopic SFRP2 overexpression in normal osteoblast precursors is sufficient to suppress normal osteoblast differentiation and to promote OS phenotypes through induction of oncogenic molecules such as FOXM1 and CYR61 in a β-catenin–independent manner. Conversely, inhibition of SFRP2, FOXM1, or CYR61 represses the tumorigenic potential. In summary, these findings demonstrate the oncogenic role of SFRP2 in the development of p53 mutation-associated OS and that inhibition of SFRP2 is a potential therapeutic strategy.

Oncogenic role of sFRP2 in P53-mutant osteosarcoma development via autocrine and paracrine mechanism

Osteosarcoma (OS), the most common primary bone tumor, is highly metastatic with high chemotherapeutic resistance and poor survival rates. Using induced pluripotent stem cells (iPSCs) generated from Li-Fraumeni syndrome (LFS) patients, we investigated an oncogenic role of secreted frizzled-related protein 2 (sFRP2) in P53 mutation-associated OS development. Interestingly, we found that high sFRP2 expression in OS patient samples correlates with poor survival. Systems-level analyses identified that expression of sFRP2 increases during LFS OS development and can induce angiogenesis. Ectopic sFRP2 overexpression in normal osteoblast precursors is sufficient to suppress normal osteoblast differentiation and to promote OS phenotypes through induction of oncogenic molecules such as FOXM1 and CYR61 in a β-catenin independent manner. Conversely, inhibition of sFRP2, FOXM1 or CYR61 represses the tumorigenic potential. In summary, these findings demonstrate the oncogenic role of sFRP2 in P53 mutation-associated OS development and that inhibition of sFRP2 is a potential therapeutic strategy.

Role of Long Noncoding RNA HOTAIR in the Growth and Apoptosis of Osteosarcoma Cell MG-63

This study investigated the function of HOTAIR in the growth and apoptosis of OS MG-63 cell linein vitroand further clarified its mechanism. The expression levels of HOTAIR in OS MG-63 cell line and normal osteoblast hFOB1.19 cell line were determined by RT-PCR, respectively. The growth and apoptosis of MG-63 cellsin vitrowere investigated by MTT assay and flow cytometry assay after HOTAIR was knocked down with retroviral vector construction. And the expression levels of cell growth and apoptosis related factors TGF-β, p53, Bcl-2, and TNF-αwere determined to clarify the mechanism. We found that HOTAIR was highly expressed in osteosarcoma MG-63 cell line compared with normal osteoblast hFOB1.19 cell line. The proliferation rate was lower and the apoptosis rate was higher significantly in shHOTAIR MG-63 cells than those in EV MG-63 cells. TGF-βand Bcl-2 were downregulated significantly when HOTAIR was knocked down. p53 and TNF-αwere upregulated significantly when HOTAIR was knocked down. These results indicated that HOTAIR functioned as a carcinogenic lncRNA, which could promote the proliferation and inhibit the apoptosis of MG-63 cellsin vitro. HOTAIR could be a potential target for the treatment of osteosarcoma.

Enroute through Bone: Biology of Tooth Movement

ABSTRACT Biology of orthodontic tooth movement has always been an interesting field of orthodontist. Orthodontic tooth movement is divided into different phases and number of theories has been given for it, at present most of them are invalid. Gene-directed protein synthesis, modification and integration form the essence of all life processes, including OTM. Bone adaptation to orthodontic force depends on normal osteoblast and osteoclast genes that correctly express needed proteins at the right time and places. Prostaglandins, cytokines and growth factors play an important role in OTM. How to cite this article Patel VD, Jyothikiran H, Raghunath N, Shivalinga BM. Enroute through Bone: Biology of Tooth Movement. World J Dent 2012;3(1):55-59.