Article

Increased radiation-induced apoptosis of SaOS2 cells via inhibition of NFκB: A role for c-Jun N-terminal kinase

Center for Musculoskeletal Research, University of Rochester Medical Center, Rochester, New York 14642, USA.
Journal of Cellular Biochemistry (Impact Factor: 3.26). 12/2005; 96(6):1262-73. DOI: 10.1002/jcb.20607
Source: PubMed

ABSTRACT

To elucidate the possible effect of NFkappaB on radioresistance, we used the osteosarcoma cell line Saos2, stably expressing the NFkappaB constitutive inhibitor, mIkappaB (Saos2-mIkappaB) or stably transfected with the empty vector (Saos2-EV). Ionizing radiation induced "intrinsic" apoptosis in Saos2-mIkappaB cells but not in Saos2-EV control cells, with intact NFkappaB activity. We find as expected, that this NFkappaB activity was enhanced following irradiation in the Saos2-EV control cells. On the other hand, inhibition of NFkappaB signaling in Saos2-mIkappaB cells led to the upregulation of the pro-apoptotic systems, such as Bax protein and c-Jun N-terminal Kinase (JNK)/c-Jun/AP1 signaling. Inhibition of NFkappaB resulted in decreased expression of the DNA damage protein GADD45beta, a known inhibitor of JNK. Subsequently, JNK activation of c-Jun/AP-1 proteins increased radiation-induced apoptosis in these mutants. Radiation-induced apoptosis in Saos2-mIkappaB cells was inhibited by the JNK specific inhibitor SP600125 as well as by Bcl-2 over-expression. Furthermore, release of cytochrome-c from mitochondria was increased and caspase-9 and -3 were activated following irradiation in Saos2-mIkappaB cells. Antisense inhibition of GADD45beta in Saos2-EV cells significantly enhanced apoptosis following irradiation. Our results demonstrate that radioresistance of Saos2 osteosarcoma cells is due to NFkappaB-mediated inhibition of JNK. Our study brings new insight into the mechanisms underlying radiation-induced apoptosis of osteosarcoma, and may lead to development of new therapeutic strategies against osteosarcoma.

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    • "We reviewed experimentally identified miR-221 targets or upstream genes and pathways. Among them, there are several genes and pathways mediate osteosarcoma tumorigenicity such as p57 [54], [55], NF-κb [56], [57], p27 [21], [58], Notch pathway [59] and so on. Our work identified a role for PTEN in miRNA-221-induced biology and confirmed p27 but not p57 could be regulated by miR-221, these results indicate that miR-221 induces cisplatin resistance directly through at least p27 and PTEN pathway, it remains possible other factors might be partially involved. "
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    ABSTRACT: MicroRNAs are short regulatory RNAs that negatively modulate protein expression at a post-transcriptional and/or translational level and are deeply involved in the pathogenesis of several types of cancers. Specifically, microRNA-221 (miR-221) is overexpressed in many human cancers, wherein accumulating evidence indicates that it functions as an oncogene. However, the function of miR-221 in human osteosarcoma has not been totally elucidated. In the present study, the effects of miR-221 on osteosarcoma and the possible mechanism by which miR-221 affected the survival, apoptosis, and cisplatin resistance of osteosarcoma were investigated.
    Preview · Article · Jan 2013 · PLoS ONE
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    • "Because elevated NF-κB signaling in osteosarcoma may confer radioresistance (Eliseev et al., 2005), the suppression of NF-κB by parthenolide is hypothesized to increase the susceptibility of cells to ionizing radiation. In Fig. 3A, a reporter-promoter assay was used to demonstrate further activation of NF-κB in LM7 cells following exposure to radiation compared to untreated LM7 cells, indicating initiation of an NF-κB-mediated protective response to stress that may lead to evasion of apoptosis (Naugler and Karin, 2008; Van Antwerp et al, 1996). "
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    ABSTRACT: Osteosarcoma is a devastating tumor of bone, primarily affecting adolescents. Osteosarcoma tumors are notoriously radioresistant. Radioresistant cancers, including osteosarcoma, typically exhibit a considerable potential for relapse and development of metastases following treatment. Relapse and metastatic potential can, in part, be due to a specific radioresistant subpopulation of cells with stem-like characteristics, cancer stem cells, which maintain the capacity to regenerate entire tumors. In the current study, we have investigated whether in vitro treatments with parthenolide, a naturally occurring small molecule that interferes with NF-κB signaling and has various other effects, will re-sensitize cancer stem cells and the entire cell population to radiotherapy in osteosarcoma. Our results indicate that parthenolide and ionizing radiation synergistically induce cell death in LM7 osteosarcoma cells. Importantly, the combination treatment results in a significant reduction in the viability of both the overall population of osteosarcoma cells and the cancer stem cell subpopulation. This effect is dependent on the ability of parthenolide to induce oxidative stress. Therefore, as a supplement to current multimodal therapy, parthenolide may sensitize osteosarcoma tumors to radiation and greatly reduce the prevalence of relapse and metastatic progression.
    Full-text · Article · Apr 2012 · Journal of Cellular Biochemistry
    • "One microliter of the synthesized cDNA was subjected to real-time PCR using the following pairs of primers: CypD (. Real-time PCR was performed as previously described[16]using the RotorGene real-time DNA amplification system (Corbett Research) and the double-strand-specific fluorescent dye SYBR Green (Rad) to monitor DNA synthesis. PCR products were subjected to a melting curve analysis and the data were analyzed and quantified with the RotorGene analysis software. "
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    ABSTRACT: The mitochondrial permeability transition (MPT) is involved in both necrosis and apoptosis. Cyclophilin D (CypD) is an important component of the MPT. Brain mitochondria are more resistant to the MPT when compared to heart or liver mitochondria. We found that this increased resistance correlates with low expression of CypD in brain when compared to heart or liver. In newborn rats, sensitivity of brain mitochondria to the MPT and CypD expression are significantly higher than in mature animals. In an in vitro model of neuronal development, mitochondria in differentiated neuronal-like cells exert a higher calcium threshold toward MPT induction and express significantly less CypD when compared to undifferentiated precursor cells. Gain and loss of function experiments confirm the role of CypD in sensitivity to the MPT. Together our data indicate that the increased calcium threshold of brain mitochondria to the MPT correlates with low expression of CypD in brain; and that neuronal cells lose CypD during differentiation and become less sensitive to the MPT induction. This may be a protection mechanism that raises the threshold of brain tissue against injuries.
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