GSK-3β: A Bifunctional Role in Cell Death Pathways

Although glycogen synthase kinase-3 beta (GSK-3β) was originally named for its ability to phosphorylate glycogen synthase and regulate glucose metabolism, this multifunctional kinase is presently known to be a key regulator of a wide range of cellular functions. GSK-3β is involved in modulating a variety of functions including cell signaling, growth metabolism, and various transcription factors that determine the survival or death of the organism. Secondary to the role of GSK-3β in various diseases including Alzheimer's disease, inflammation, diabetes, and cancer, small molecule inhibitors of GSK-3β are gaining significant attention. This paper is primarily focused on addressing the bifunctional or conflicting roles of GSK-3β in both the promotion of cell survival and of apoptosis. GSK-3β has emerged as an important molecular target for drug development

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Not AvailableStudies were conducted to investigate the effect of soil applied paclobutrazol (PBZ) on the hormonal composition of auxin (IAA), abscisic acid (ABA), cytokinins and gibberellins in 12 years old Alphonso mango trees during the year 2011. Paclobutrazol treatment decreased IAA contain in shoots by 4.3 and 28.2 % at 15 days before bud break and at bud break stage, respectively. Abscisic acid content in PBZ treated trees was 59.85 and 41.11 % higher in leaf and bud, respectively, as compared to untreated trees, during flowering period. Fifteen days before bud break, total cytokinin contents (zeatin, dihydrozeatin riboside, zeatin riboside, isopentenyl adenine, isopentenyl adenosine) in leaf and bud were 25.93 and 37.54 %, respectively less than untreated trees, but at bud break and 15 days after bud break it increased by 31.92 and 36.37 % in leaf and bud, respectively. Paclobutrazol treatment decreased gibberellin contents in shoots. Total gibberellin contents at bud break stage was 51.71 % less in treated trees as compared with untreated trees, while 55.58 % reduction was observed in treated trees from 15 days before bud break to bud break. While in untreated trees slight increment in total gibberellin contents was observed. These results indicated that, PBZ application though decreased gibberellin and IAA contents, but caused increases in ABA and cytokinins in mango shoots to elicit flowering responses.Not Availabl

Not Available

Not AvailableStudies were conducted to investigate the effect of soil applied paclobutrazol (PBZ) on the hormonal composition of auxin (IAA), abscisic acid (ABA), cytokinins and gibberellins in 12 years old Alphonso mango trees during the year 2011. Paclobutrazol treatment decreased IAA contain in shoots by 4.3 and 28.2 % at 15 days before bud break and at bud break stage, respectively. Abscisic acid content in PBZ treated trees was 59.85 and 41.11% higher in leaf and bud, respectively, as compared to untreated trees, during flowering period. Fifteen days before bud break, total cytokinin contents (zeatin, dihydrozeatin riboside, zeatin riboside, isopentenyl adenine, isopentenyl adenosine) in leaf and bud were 25.93 and 37.54 %, respectively less than untreated trees, but at bud break and 15 days after bud break it increased by 31.92 and 36.37 % in leaf and bud, respectively. Paclobutrazol treatment decreased gibberellin contents in shoots. Total gibberellin contents at bud break stage was 51.71 % less in treated trees as compared with untreated trees, while 55.58 % reduction was observed in treated trees from 15 days before bud break to bud break. While in untreated trees slight increment in total gibberellin contents was observed. These results indicated that, PBZ application though decreased gibberellin and IAA contents, but caused increases in ABA and cytokinins in mango shoots to elicit flowering responses.Not Availabl

Cytosolic phospholipaseA2 inhibition with PLA-695 radiosensitizes tumors in lung cancer animal models.

Lung cancer remains the leading cause of cancer deaths in the United States and the rest of the world. The advent of molecularly directed therapies holds promise for improvement in therapeutic efficacy. Cytosolic phospholipase A2 (cPLA2) is associated with tumor progression and radioresistance in mouse tumor models. Utilizing the cPLA2 specific inhibitor PLA-695, we determined if cPLA2 inhibition radiosensitizes non small cell lung cancer (NSCLC) cells and tumors. Treatment with PLA-695 attenuated radiation induced increases of phospho-ERK and phospho-Akt in endothelial cells. NSCLC cells (LLC and A549) co-cultured with endothelial cells (bEND3 and HUVEC) and pre-treated with PLA-695 showed radiosensitization. PLA-695 in combination with irradiation (IR) significantly reduced migration and proliferation in endothelial cells (HUVEC & bEND3) and induced cell death and attenuated invasion by tumor cells (LLC &A549). In a heterotopic tumor model, the combination of PLA-695 and radiation delayed growth in both LLC and A549 tumors. LLC and A549 tumors treated with a combination of PLA-695 and radiation displayed reduced tumor vasculature. In a dorsal skin fold model of LLC tumors, inhibition of cPLA2 in combination with radiation led to enhanced destruction of tumor blood vessels. The anti-angiogenic effects of PLA-695 and its enhancement of the efficacy of radiotherapy in mouse models of NSCLC suggest that clinical trials for its capacity to improve radiotherapy outcomes are warranted

Autotaxin inhibition with PF8380 enhances the radiosensitivity of human and murine glioblastoma cell lines

Purpose: Glioblastoma multiforme (GBM) is an aggressive primary brain tumor that is radio-resistant and recurs despite aggressive surgery, chemo and radiotherapy. Autotaxin (ATX) is over expressed in various cancers including GBM and is implicated in tumor progression, invasion, and angiogenesis. Using the ATX specific inhibitor, PF-8380, we studied ATX as a potential target to enhance radiosensitivity in GBM.Methods and Materials: Mouse GL-261 and Human U87MG cells were used as GBM cell models. Clonogenic survival assays and tumor transwell invasion assays were performed using PF-8380 to evaluate role of ATX in survival and invasion. Radiation dependent activation of Akt was analyzed by immunoblotting. Tumor induced angiogenesis was studied using the dorsal skin-fold model in Gl-261. Heterotopic mouse GL-261 tumors were used to evaluate the efficacy of PF-8380 as a radiosensitizer.Results: Pretreatment of GL-261 and U87-MG cells with 1µM PF-8380 followed by 4Gy irradiation resulted in decreased clonogenic survival, decreased migration (33% in GL-261;P = 0.002 and 17.9% in U87; P = 0.012) decreased invasion (35.6% in GL-261; P = 0.0037 and 31.8% in U87; P = 0.002), and attenuated radiation induced Akt phosphorylation. In the tumor window model inhibition of ATX abrogated radiation-induced tumor neovascularization (65%; P=0.011). In a heterotopic mouse GL-261 tumors untreated mice took 11.2 days to reach a tumor volume of 7000 mm3 , however combination of PF-8380 (10mg/kg) with irradiation (5 fractions of 2Gy) took more than 32 days to reach a tumor volume of 7000 mm3 .Conclusion: Inhibition of ATX by PF8380 led to decreased invasion and enhanced radiosensitization of glioma cells. Radiation induced activation of Akt was abrogated by inhibition of ATX. Furthermore, inhibition of ATX led to diminished tumor vascularity and delayed tumor growth. These results suggest that inhibition of ATX may ameliorate glioblastoma response to radiotherapy

PLA-695 enhances tumor growth delay in heterotopic lung cancer tumors.

<p>LLC or A549 cells were implanted into the right footpad of C57/BL6 mice. Tumors were irradiated with 2 Gy for 5 consecutive days for a total of 10 Gy. Mice were treated with 7.5 mg/Kg body weight or vehicle control for 30 min prior to IR on days 1, 3, 5, 7 and 9. Shown are mean tumor volumes for LLC and A549 with SEM from each treatment group of mice. Tumor growth delay for LLC and A549 tumors was calculated as the number of days for tumors to reach 0. 25 cm³(B). Shown is a bar graph representing the mean tumor growth delay with SEM from each treatment group of 7 mice; * p<0.05. Tumor volumes were analyzed on day 7 for LLC tumors and day 15 for A549 tumors. Shown is a bar graph representing the tumor growth on day 7 for LLC tumors and day 15 for A549 tumors with SEM from each treatment group of 6 mice; * p<0.05.</p

Effect of PLA-695 on pro-survival signaling after radiation.

<p>HUVEC cells (A) were treated with various concentrations of PLA-695 as indicated for 45 min before treatment with 3 Gy, cells were lysed at 5 min after IR. HUVEC (B) and 3B11 (C&D) cells were treated with 300 nM PLA-695 for 45 min before treatment with 3 Gy. Cells were lysed at 5 min after IR. Shown are immunoblot analyses using specific antibodies to phospho-Akt^Ser473, total Akt, phospho-ERK1/2, total ERK1/2, and actin.</p

A. PLA-695 reduces proliferation in endothelial and lung cancer cells after irradiation.

<p>Equal numbers of bEND3, HUVEC, LLC and A549 cells were plated in 96 well plates and treated with 300 nM PLA-695 for 45 min prior to treatment with 3 Gy. Cell proliferation was determined using a colorimetric cell proliferation assay at 24, 48, 72 and 96 h post treatment. Shown is the absorbance at 490 nm. <b>B. PLA-695 enhances cell death in irradiated lung cancer cells</b>. LLC and A549 cells were treated with 300 nM PLA-695 or DMSO for 45 min prior to treatment with 3 Gy. Cells were stained with Annexin V-APC and propidium iodide and analyzed by flow cytometry at 24, 48, 72 or 96 h after irradiation. Shown are the line graphs indicating fold increase of cell death over control for each treatment with SEM from three experiments.</p