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Osteosarcoma (OS) is a rare, insidious tumor of mesenchymal origin that most often affects children, adolescents, and young adults. While the primary tumor can be controlled with chemotherapy and surgery, it is the lung metastases that are eventually fatal. Multiple studies into the initial drivers of OS development have been undertaken, but few of these have examined innate immune/inflammatory signaling. A central figure in inflammatory signaling is the innate immune/stress‐activated kinase double‐stranded RNA‐dependent protein kinase (PKR). To characterize the role of PKR in OS, U2OS, and SaOS‐2 osteosarcoma cell lines were stably transfected with wild‐type or dominant‐negative (DN) PKR. Overexpression of PKR enhanced colony formation in soft agar (U2OS and SaOS‐2), enhanced cellular migration (U2OS), and invasive migration (SaOS‐2). In contrast, overexpression of DN‐PKR inhibited attachment‐independent growth, migration and/or invasion. These data demonstrate a role for inflammatory signaling in OS formation and migration/invasion and suggest the status of PKR expression/activation may have prognostic value. [ABSTRACT FROM AUTHOR]

Osteosarcoma (OS) is the most common pediatric malignant neoplasia of the skeletal system. It is characterized by a high degree of malignancy and a severe tendency to metastasize. In the past decade, many studies have provided evidence that the phosphoinositide 3‐kinase (PI3K) signaling pathway is one of the most frequently altered pathways in human cancer, and has a critical role in driving tumor initiation and progression. Here, we have analyzed the therapeutic potential of the pan‐PI3K inhibitor NVP‐BKM120, which has recently entered clinical Phase II for treatment of PI3K‐dependent cancers on three OS cell lines. We observed a concentration‐ and time‐dependent decrease of Ser473 p‐Akt as well as reduced levels of Thr37/46 p‐4E‐BP1, an indicator of the mammalian target of rapamycin complex 1 activity. All OS cell lines used in this study responded to BKM120 treatment with an arrest of cell proliferation, an increase in cell mortality, and an increase in caspase‐3 activity. MG‐63 cells were the most responsive cell line, demonstrating a significant increase in sub‐G1 cells, and a rapid induction of cell death. Furthermore, we demonstrate that BKM120 is more effective when used in combination with other standard chemotherapeutic drugs. Combining BKM120 with vincristine demonstrated a more synergistic effect than BKM120 with doxorubicin in all the lines. Hence, we suggest that BKM120 may be a novel therapy for the treatment of OS presenting with anomalous upregulation of the PI3K signaling pathway. We have analyzed the therapeutic potential of the pan‐PI3K inhibitor NVP‐BKM120, which has recently entered clinical Phase II for treatment of PI3K‐dependent cancers on three osteosarcoma cell lines. We observed a concentration‐ and time‐dependent decrease of Ser473 p‐Akt as well as reduced levels of Thr37/46 p‐4E‐BP1. All OS cell lines used in this study responded to BKM120 treatment with an arrest of cell proliferation, an increase in cell mortality, and an increase in caspase‐3 activity. [ABSTRACT FROM AUTHOR]

Bone morphogenetic protein 2 (BMP-2) is a critical growth factor that directs osteoblast differentiation and bone formation. Phosphoinositide-phospholipase Cβ 1 (PLCβ1) plays a crucial role in the initiation of the genetic program responsible for muscle differentiation. Differentiation of C2C12 mouse myoblasts in response to insulin stimulation is characterized by a marked increase in nuclear PLCβ1. Here, the function of PLCβ1 in the osteogenic differentiation was investigated. Briefly, in C2C12 cells treated with BMP-2 we assist to a remarkable increase in PLCβ1 protein and mRNA expression. The data regarding the influence on differentiation demonstrated that PLCβ1 promotes osteogenic differentiation by up-regulating alkaline phosphatase (ALP). Moreover, PLCβ1 is present in the nuclear compartment of these cells and overexpression of a cytosolic-PLCβ1mutant (cyt-PLCβ1), which lacks a nuclear localization sequence, prevented the differentiation of C2C12 cells into osteocytes. Recent evidence indicates that miRNAs act as important post transcriptional regulators in a large number of processes, including osteoblast differentiation. Since miR-214 is a regulator of Osterix (Osx) which is an osteoblast-specific transcription factor that is needful for osteoblast differentiation and bone formation, we further investigated whether PLCβ1 could be a potential target of miR-214 in the control of osteogenic differentiation by gain- and loss- of function experiment. The results indicated that inhibition of miR-214 in C2C12 cells significantly enhances the protein level of PLCβ1 and promotes C2C12 BMP-2-induced osteogenesis by targeting PLCβ1. J. Cell. Physiol. 231: 623-629, 2016. © 2015 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

Here we report that both PLCβ1a and PLCβ1b are relevant regulators of erythropoiesis in that kinamycin F, a potent inducer of γ-globin production in K562 cells, caused a selectively reduction of both PLCβ1 isozymes even though the results point out that the effect of the drug is mainly directed toward the expression of the PLCβ1a isoform. We have identified a different role for the two isozymes as regulators of K562 differentiation process induced by kinamycin F. The overexpression of PLCβ1b induced an increase in γ-globin expression even in the absence of kinamycin F. Moreover during K562 differentiation, cyclin D3 level is regulated by PLCβ1 signaling pathway. Namely the amplification of the expression of the PLCβ1a, but not of PLCβ1b, is able to maintain high levels of expression of cyclin D3 even after treatment with kinamycin F. This could be due to their different distribution in the cell compartments since the amount of PLCβ1b is mainly present in the nucleus in respect to PLCβ1a. Our data indicate that the amplification of PLCβ1a expression, following treatment with kinamycin F, confers a real advantage to K562 cells viability and protects cells themselves from apoptosis. J. Cell. Physiol. 230: 587-594, 2015. © 2014 Wiley Periodicals, Inc., A Wiley Company [ABSTRACT FROM AUTHOR]