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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 1,765 records · Page 98
All sourcesNASA NTRSDOE OSTI
DOE OSTI2015

Differential expression of estrogen receptor α and β isoforms in multiple and solitary leiomyomas

Uterine leiomyomas are benign myometrial neoplasms that function as one of the common indications for hysterectomy. Clinical and biological evidences indicate that uterine leiomyomas are estrogen-dependent. Estrogen stimulates cell proliferation through binding to the estrogen receptor (ER), of which both subtypes α and β are present in leiomyomas. Clinically, leiomyomas may be singular or multiple, where the first one is rarely recurring if removed and the latter associated to a relatively young age or genetic predisposition. These markedly different clinical phenotypes indicate that there may different mechanism causing a similar smooth muscle response. To investigate the relative expression of ERα and ERβ in multiple and solitary uterine leiomyomas, we collected samples from 35 Chinese women (multiple leiomyomas n = 20, solitary leiomyoma n = 15) undergoing surgery to remove uterine leiomyomas. ELISA assay was performed to detect estrogen(E{sub 2}) concentration. Quantitative real-time PCR analysis was performed to detect ERα and ERβ mRNA expression. Western blot and immunohistochemical analysis were performed to detect ERα and ERβ protein expression. We found that ERα mRNA and protein levels of in multiple leiomyomas were significantly lower than those of solitary leiomyomas, whereas ERβ mRNA and protein levels in multiple leiomyomas were significantly higher than those in solitary leiomyomas, irrespectively of the menstrual cycle stage. In both multiple and solitary leiomyomas, ERα expression was higher than that of ERβ. E{sub 2} concentration in multiple and solitary leiomyomas correlated with that of ERα expression. ERα was present in nuclus and cytoplasma while estrogen receptor β localized only in nuclei in both multiple and solitary leiomyomas. Our findings suggest that the difference of ERα and ERβ expression between multiple and solitary leiomyomas may be responsible for the course of the disease subtypes. - Highlights: • In both multiple and solitary leiomyomas, ERα expression was higher than that of ERβ. • ERα was significantly lower, whereas ERβ was significantly higher in multiple leiomyomas than that in solitary leiomyomas. • The differential expression of ERα and ERβ may be responsible for the cause of the disease subtypes.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2015

1,25(OH)2D3 attenuates TGF-β1/β2-induced increased migration and invasion via inhibiting epithelial–mesenchymal transition in colon cancer cells

1,25-Dihydroxyvitamin D3 (1,25(OH)2D3) has been reported to inhibit proliferation and migration of multiple types of cancer cells. However, the mechanism underlying its anti-metastasis effect is not fully illustrated. In this study, the effect of 1,25(OH)2D3 on TGF-β1/β2-induced epithelial–mesenchymal transition (EMT) is tested in colon cancer cells. The results suggest that 1,25(OH)2D3 inhibited TGF-β1/β2-induced increased invasion and migration of in SW-480 and HT-29 cells. 1,25(OH)2D3 also inhibited the cadherin switch in SW-480 and HT-29 cells. TGF-β1/β2-induced increased expression of EMT-related transcription factors was also inhibited by 1,25(OH)2D3. 1,25(OH)2D3 also inhibited the secretion of MMP-2 and MMP-9 and increased expression of F-actin induced by TGF-β1/β2 in SW-480 cells. Taken together, this study suggests that the suppression of EMT might be one of the mechanisms underlying the anti-metastasis effect of 1,25(OH)2D3 in colon cancer cells. - Highlights: • TGF-β1/β2-induced model of EMT was used in this study to test the effect of 1,25(OH)2D3 on EMT in colon cancer cells. • 1,25(OH)2D3 inhibited TGF-β1/β2-induced increased migration and invasion. • 1,25(OH)2D3 inhibited TGF-β1/β2-induced increased level of EMT-related transcription factors. • 1,25(OH)2D3 inhibited TGF-β1/β2-induced increased expression of F-actin in SW-480 cells.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2015

Merlin negative regulation by miR-146a promotes cell transformation

Inactivation of the tumor suppressor Merlin, by deleterious mutations or by protein degradation via sustained growth factor receptor signaling-mediated mechanisms, results in cell transformation and tumor development. In addition to these mechanisms, here we show that, miRNA-dependent negative regulation of Merlin protein levels also promotes cell transformation. We provide experimental evidences showing that miR-146a negatively regulates Merlin protein levels through its interaction with an evolutionary conserved sequence in the 3´ untranslated region of the NF2 mRNA. Merlin downregulation by miR-146a in A549 lung epithelial cells resulted in enhanced cell proliferation, migration and tissue invasion. Accordingly, stable miR-146a-transfectant cells formed tumors with metastatic capacity in vivo. Together our results uncover miRNAs as yet another negative mechanism controlling Merlin tumor suppressor functions.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2015

Inhibition of osteoclast differentiation by overexpression of NDRG2 in monocytes

N-Myc downstream-regulated gene 2 (NDRG2), a member of the NDRG family of differentiation-related genes, has been characterized as a regulator of dendritic cell differentiation from monocytes, CD34{sup +} progenitor cells, and myelomonocytic leukemic cells. In this study, we show that NDRG2 overexpression inhibits the differentiation of U937 cells into osteoclasts in response to stimulation with a combination of macrophage colony-stimulating factor (M-CSF) and soluble receptor activator of NF-κB ligand (RANKL). U937 cells stably expressing NDRG2 are unable to differentiate into multinucleated osteoclast-like cells and display reduced tartrate-resistant acid phosphatase (TRAP) activity and resorption pit formation. Furthermore, NDRG2 expression significantly suppresses the expression of genes that are crucial for the proliferation, survival, differentiation, and function of osteoclasts, including c-Fos, Atp6v0d2, RANK, and OSCAR. The activation of ERK1/2 and p38 is also inhibited by NDRG2 expression during osteoclastogenesis, and the inhibition of osteoclastogenesis by NDRG2 correlates with the down-regulation of the expression of the transcription factor PU.1. Taken together, our results suggest that the expression of NDRG2 potentially inhibits osteoclast differentiation and plays a role in modulating the signal transduction pathway responsible for osteoclastogenesis. - Highlights: • The expression of NDRG2 significantly impairs osteoclast differentiation. • PU.1 and p38 MAPK inhibitions by NDRG2 are critical for the inhibition of osteoclastogenesis. • Knockdown of NDRG2 rescues the ability of monocytes to differentiate into osteoclasts. • NDRG2 expression in BM and primary macrophages also impairs osteoclast differentiation. • This study implies the potential of NDRG2 expression in the inhibition of osteoclastogenesis.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2015

Administration of sulfosuccinimidyl-4-[N-maleimidomethyl] cyclohexane-1-carboxylate conjugated GP100{sub 25–33} peptide-coupled spleen cells effectively mounts antigen-specific immune response against mouse melanoma

It remains a top research priority to develop immunotherapeutic approaches to induce potent antigen-specific immune responses against tumors. However, in spite of some promising results, most strategies are ineffective because they generate low numbers of tumor-reactive cytotoxic T lymphocytes (CTLs). Here we designed a strategy to enhance antigen-specific immune response via administering sulfosuccinimidyl-4-[N-maleimidomethyl] cyclohexane-1-carboxylate (sulfo-SMCC)-conjugated melanoma tumor antigen GP100{sub 25–33} peptide-coupled syngeneic spleen cells in a mouse model of melanoma. We found that infusion of GP100{sub 25–33} peptide-coupled spleen cells significantly attenuated the growth of melanoma in prophylactic and therapeutic immunizations. Consistent with these findings, the adoptive transfer of spleen cells from immunized mice to naïve syngeneic mice was able to transfer anti-tumor effect, suggesting that GP100{sub 25–33} peptide-specific immune response was induced. Further studies showed that, CD8+ T cell proliferation and the frequency of interferon (IFN)-γ-producing CD8+ T cells upon ex vivo stimulation by GP100{sub 25–33} were significantly increased compared to control groups. Tumor antigen, GP100{sub 25–23} specific immune response was also confirmed by ELISpot and GP100-tetramer assays. This approach is simple, easy-handled, and efficiently delivering antigens to lymphoid tissues. Our study offers an opportunity for clinically translating this approach into tumor immunotherapy. - Highlights: • Infusion of GP100{sub 25–33}-coupled spleen cells leads to potent anti-melanoma immunity. • GP100{sub 25–33}-coupled spleen cell treatment induces antigen-specific IFN-γ-producing CD8 T cells. • This approach takes advantage of homing nature of immune cells.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2015

Apelin-13 upregulates Egr-1 expression in rat vascular smooth muscle cells through the PI3K/Akt and PKC signaling pathways

Previous studies have shown that Apelin-13 upregulates early growth response factor-1 (Egr-1) via the extracellular signal-regulated protein kinase (ERK) signaling pathway. Apelin-13 induces proliferation and migration of vascular smooth muscle cells (VSMCs) as well as the upregulation of osteopontin (OPN) via the upregulation of Egr-1. This study was designed to further explore the activity of Apelin-13 in VSMCs by investigating members of the mitogen-activated protein kinase (MAPK) family, in particular Jun kinase (JNK) and p38 mitogen-activated protein kinase (P38). We also examined whether the phosphatidylinositol 3 kinase (PI3K)/protein kinase B (Akt) and protein kinase C (PKC) signaling pathways were involved in the regulation of Egr-1 by Apelin-13. We treated rat aortic VSMCs with Apelin-13 and examined the expression of JNK, p-JNK, P38, and p-P38 to investigate whether Apelin-13-mediated increases in Egr-1 occurred through the JNK and P38 signaling pathways. We then pretreated VSMCs with the Gi protein inhibitor pertussis toxin (PTX) and the Gq inhibitor YM254890, added Apelin-13 and looked for changes in Egr-1 expression. Finally, we pretreated with the PI3K inhibitor LY294002 and the PKC inhibitor GF109203X, and treated with Apelin-13. Our results showed that JNK and P38 did not participate in Apelin-13-mediated increase in Egr-1. Instead, Apelin-13 upregulation of Egr-1 was mediated by a PTX-sensitive Gi protein. Apelin-13 did increase ERK phosphorylation through the PI3K/Akt and PKC signaling pathways, resulting in changes in Egr-1 expression. These data provide important targets for future studies to modulate vascular remodeling. - Highlights: • Apelin-13 mediates Egr-1 upregulation in vascular smooth muscle cells via ERK1/2. • The underlying mechanisms are unknown, but exclude Jnk or p38 pathway activation. • Apelin-13 binds to Gi, activating the PI3K/Akt and PKC signaling cascades. • Consequent ERK phosphorylation results in increased Egr-1 expression. • These novel targets may be potential therapies for vascular remodeling diseases.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2016

Triptolide inhibits transcription of hTERT through down-regulation of transcription factor specificity protein 1 in primary effusion lymphoma cells

Primary effusion lymphoma (PEL) is a rare and aggressive non-Hodgkin's lymphoma. Human telomerase reverse transcriptase (hTERT), a key component responsible for the regulation of telomerase activity, plays important roles in cellular immortalization and cancer development. Triptolide purified from Tripterygium extracts displays a broad-spectrum bioactivity profile, including immunosuppressive, anti-inflammatory, and anti-tumor. In this study, it is investigated whether triptolide reduces hTERT expression and suppresses its activity in PEL cells. The mRNA and protein levels of hTERT were examined by real time-PCR and Western blotting, respectively. The activity of hTERT promoter was determined by Dual luciferase reporter assay. Our results demonstrated that triptolide decreased expression of hTERT at both mRNA and protein levels. Further gene sequence analysis indicated that the activity of hTERT promoter was suppressed by triptolide. Triptolide also reduced the half-time of hTERT. Additionally, triptolide inhibited the expression of transcription factor specificity protein 1(Sp1) in PEL cells. Furthermore, knock-down of Sp1 by using specific shRNAs resulted in down-regulation of hTERT transcription and protein expression levels. Inhibition of Sp1 by specific shRNAs enhanced triptolide-induced cell growth inhibition and apoptosis. Collectively, our results demonstrate that the inhibitory effect of triptolide on hTERT transcription is possibly mediated by inhibition of transcription factor Sp1 in PEL cells. - Highlights: • Triptolide reduces expression of hTERT by decreasing its transcription level. • Triptolide reduces promoter activity and stability of hTERT. • Triptolide down-regulates expression of Sp1. • Special Sp1 shRNAs inhibit transcription and protein expression of hTERT. • Triptolide and Sp1 shRNA2 induce cell proliferation inhibition and apoptosis.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2016

LDH-A promotes malignant progression via activation of epithelial-to-mesenchymal transition and conferring stemness in muscle-invasive bladder cancer

Lactate dehydrogenase-A(LDH-A) is an important rate-limiting enzyme in the Warburg effect. Survival analysis indicated poor clinical outcomes in MIBC with high LDH-A expression. The results of in vitro experiment indicated that LDH-A promotes MIBC cells proliferation, invasion and migration. The positive relationship between LDH-A expression and CSC/EMT markers was confirmed both in invasive bladder cell line and in 136 MIBC specimens. Thus, we conclude that LDH-A may be a promising target for MIBC. - Highlights: • Survival analysis indicated poor clinical outcomes in MIBC with high LDH-A expression. • IHC analysis of 136 MIBC specimens revealed increased LDH-A is correlated with positive Oct4 and negative E-cadherin. • In vitro experiments demonstrated LDH-A promotes MIBC progression by positive regulation of EMT/CSC.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2016

Loss of maintenance DNA methylation results in abnormal DNA origin firing during DNA replication

The mammalian maintenance methyltransferase DNMT1 [DNA (cytosine-5-)-methyltransferase 1] mediates the inheritance of the DNA methylation pattern during replication. Previous studies have shown that depletion of DNMT1 causes a severe growth defect and apoptosis in differentiated cells. However, the detailed mechanisms behind this phenomenon remain poorly understood. Here we show that conditional ablation of Dnmt1 in murine embryonic fibroblasts (MEFs) resulted in an aberrant DNA replication program showing an accumulation of late-S phase replication and causing severely defective growth. Furthermore, we found that the catalytic activity and replication focus targeting sequence of DNMT1 are required for a proper DNA replication program. Taken together, our findings suggest that the maintenance of DNA methylation by DNMT1 plays a critical role in proper regulation of DNA replication in mammalian cells. - Highlights: • DNMT1 depletion results in an abnormal DNA replication program. • Aberrant DNA replication is independent of the DNA damage checkpoint in DNMT1cKO. • DNMT1 catalytic activity and RFT domain are required for proper DNA replication. • DNMT1 catalytic activity and RFT domain are required for cell proliferation.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2016

The epigenetic regulation of HIF-1α by SIRT1 in MPP{sup +} treated SH-SY5Y cells

Both silent information regulator 1 (SIRT1) and hypoxia inducible factor 1 (HIF-1) have been found to play important roles in the pathophysiology of Parkinson's disease (PD). However, their mechanisms and their relationship still require further study. In the present study, we focused on the change and relationship of SIRT1 and HIF-1α in PD. PD cell models were established by using methyl-4-phenylpyridinium (MPP{sup +}), which induced inhibition of cell proliferation, cell cycle arrest and apoptosis. We found that the expression of HIF-1α and its target genes VEGFA and LDHA increased and that SIRT1 expression was inhibited in MPP{sup +} treated cells. With further analysis, we found that the acetylation of H3K14 combined with the HIF-1α promoter was dramatically increased in cells treated with MPP{sup +}, which resulted in the transcriptional activation of HIF-1α. Moreover, the acetylation of H3K14 and the expression of HIF-1α increased when SIRT1 was knocked down, suggesting that SIRT1 was involved in the epigenetic regulation of HIF-1α. At last, phenformin, another mitochondrial complex1 inhibitor, was used to testify that the increased HIF-1a was not due to off target effects of MPP{sup +}. Therefore, our results support a link between PD and SIRT1/HIF-1α signaling, which may serve as a clue for understanding PD.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2016

miR-1182 inhibits growth and mediates the chemosensitivity of bladder cancer by targeting hTERT

microRNAs (miRNAs) have been demonstrated to contribute to tumor progression and metastasis and proposed to be key regulators of diverse biological processes. In this study, we report that miR-1182 is deregulated in bladder cancer tissues and cell lines. To characterize the role of miR-1182 in bladder cancer cells, we performed functional assays. The overexpression of miR-1182 significantly inhibits bladder cancer cell proliferation, colony formation, and invasion. Moreover, its up-regulation induced cell cycle arrest and apoptosis and mediated chemosensitivity to cisplatin in bladder cancer. Furthermore, a luciferase reporter assay and a rescue experiment indicated that miR-1182 directly targets hTERT by binding its 3′UTR. In conclusion, these results demonstrate that miR-1182 acts as a tumor suppressor and may be a potential biomarker for bladder cancer diagnosis and treatment.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2016

Trichostatin A enhances estrogen receptor-alpha repression in MCF-7 breast cancer cells under hypoxia

Estrogen receptor (ER) is a crucial determinant of resistance to endocrine therapy, which may change during the progression of breast cancer. We previously showed that hypoxia induces ESR1 gene repression and ERα protein degradation via proteasome-mediated pathway in breast cancer cells. HDAC plays important roles in the regulation of histone and non-histone protein post-translational modification. HDAC inhibitors can induce epigenetic changes and have therapeutic potential for targeting various cancers. Trichostatin A exerts potent antitumor activities against breast cancer cells in vitro and in vivo. In this report, we show that TSA augments ESR1 gene repression at the transcriptional level and downregulates ERα protein expression under hypoxic conditions through a proteasome-mediated pathway. TSA-induced estrogen response element-driven reporter activity in the absence of estrogen was synergistically enhanced under hypoxia; however, TSA inhibited cell proliferation under both normoxia and hypoxia. Our data show that the hypoxia-induced repression of ESR1 and degradation of ERα are enhanced by concomitant treatment with TSA. These findings expand our understanding of hormone responsiveness in the tumor microenvironment; however, additional in-depth studies are required to elucidate the detailed mechanisms of TSA-induced ERα regulation under hypoxia. - Highlights: • TSA augments ESR1 gene repression at the transcriptional level under hypoxia. • TSA downregulates ERα protein expression under hypoxia. • TSA-induced ERα regulation under hypoxia is essential for understanding the behavior and progression of breast cancer.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2016

Eukaryotic translation initiation factor 5A (eIF5A) is essential for HIF-1α activation in hypoxia

The eukaryotic initiation factor 5A (eIF5A) is an essential protein involved in translation elongation and cell proliferation. eIF5A undergoes several post-translational modifications including hypusination and acetylation. Hypusination is indispensable for the function of eIF5A. On the other hand, the precise function of acetylation remains unknown, but it may render the protein inactive since hypusination blocks acetylation. Here, we report that acetylation of eIF5A increases under hypoxia. During extended hypoxic periods an increase in the level of eIF5A acetylation correlated with a decrease in HIF-1α, suggesting involvement of eIF5A activity in HIF-1α expression under hypoxia. Indeed, suppression of eIF5A by siRNA oligo-mediated knockdown or treatment with GC7, a deoxyhypusine synthase inhibitor, led to significant reduction of HIF-1α activity. Furthermore, knockdown of eIF5A or GC7 treatment reduced tumor spheroid formation with a concomitant decrease in HIF-1α expression. Our results suggest that functional, hypusinated eIF5A is necessary for HIF-1α expression during hypoxia and that eIF5A is an attractive target for cancer therapy. - Highlights: • Hypoxia induces acetylation of eIF5A. • Active eIF5A is necessary for HIF-1α activation in hypoxia. • Active eIF5A is important for tumor spheroid growth.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2016

4SC-202 activates ASK1-dependent mitochondrial apoptosis pathway to inhibit hepatocellular carcinoma cells

The aim of the present study is to investigate the potential anti-hepatocellular carcinoma (HCC) cell activity by 4SC-202, a novel class I HDAC inhibitor (HDACi). The associated signaling mechanisms were also analyzed. We showed that 4SC-202 treatment induced potent cytotoxic and proliferation–inhibitory activities against established HCC cell lines (HepG2, HepB3, SMMC-7721) and patient-derived primary HCC cells. Further, adding 4SC-202 in HCC cells activated mitochondrial apoptosis pathway, which was evidenced by mitochondrial permeability transition pore (mPTP) opening, cytochrome C cytosol release and caspase-3/-9 activation. Inhibition of this apoptosis pathway, by caspase-3/-9 inhibitors, mPTP blockers, or by shRNA-mediated knockdown of cyclophilin-D (Cyp-D, a key component of mPTP), significantly attenuated 4SC-202-induced HCC cell death and apoptosis. Reversely, over-expression of Cyp-D enhanced 4SC-202's sensitivity in HCC cells. Further studies showed that 4SC-202 induced apoptosis signal-regulating kinase 1 (ASK1) activation, causing it translocation to mitochondria and physical association with Cyp-D. This mitochondrial ASK1-Cyp-D complexation appeared required for mediating 4SC-202-induced apoptosis activation. ASK1 stable knockdown by targeted-shRNAs largely inhibited 4SC-202-induced mPTP opening, cytochrome C release, and following HCC cell apoptotic death. Together, we suggest that 4SC-202 activates ASK1-dependent mitochondrial apoptosis pathway to potently inhibit human HCC cells. - Highlights: • 4SC-202 exerts potent anti-proliferative and cytotoxic activity against established/primary HCC cells. • SC-202-induced anti-HCC cell activity relies on caspase-dependent apoptosis activation. • 4SC-202 activates Cyp-D-dependent mitochondrial apoptosis pathway in HCC cells. • 4SC-202 activates ASK1 in HCC cells, causing it translocation to mitochondria. • Mitochondrial ASK1-Cyp-D complexation mediates 4SC-202's activity in HCC cells.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2016

MicroRNA-367 is a potential diagnostic biomarker for patients with esophageal squamous cell carcinoma

Purpose: In this study, we investigated whether microRNA-367 (miR-367) may serve as a circulating biomarker and tumor oncogene in esophageal squamous carcinoma (ESCC). Methods: Circulating serum miR-367 was compared by quantitative RT-PCR (qRT-PCR) between 35 ESCC patients and 35 normal control patients, as well paired ESCC tumor tissues and adjacent non-tumor esophageal epithelial tissues in 46 patients. The correlation between serum miR-367 and clinicopathological properties of ESCC patients was assessed. The overall survival (OS) was assessed by Kaplan–Meier method and compared by log-rank test between patients with high serum miR-367 and low serum miR-367. The possibility of miR-367 being independent prognostic factor for ESCC was also assessed. Furthermore, lentivirus-mediated miR-367 downregulation was conducted in ESCC cell lines Kyse30 and TE-1 cells to assess the possible oncogenic effect of miR-367 on ESCC proliferation and cell cycle transition in vitro. Results: MiR-367 was aberrantly upregulated in sera and tumors of ESCC patients, whereas downregulated in ESCC patients after the treatments of esophagectomy and chemotherapy. Serum miR-367 was found to be closely correlated with the clinicopathological properties of differentiation grades, clinical stage and tumor metastasis in ESCC patients. Serum miR-367 was also confirmed to be associated with OS, as well as serving independent prognostic factor in ESCC patients. Moreover, lentivirus-induced miR-367 downregulation inhibited cancer growth and cell cycle transition in Kyse30 and TE-1 cells. Conclusion: MiR-367 is a potential biomarker for ESCC and may act as an oncogene in regulating ESCC development. - Highlights: • MiR-367 was aberrantly upregulated in sera and tumors of ESCC patients. • MiR-367 was downregulated in ESCC patients after esophagectomy or chemotherapy. • Serum miR-367 was correlated with the clinicopathological properties of ESCC patients. • Serum miR-367 was associated with OS in ESCC patients. • lentivirus-induced miR-367 downregulation inhibited ESCC growth and cell cycle transition.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2016

Mefloquine effectively targets gastric cancer cells through phosphatase-dependent inhibition of PI3K/Akt/mTOR signaling pathway

Deregulation of PI3K/Akt/mTOR pathway has been recently identified to play a crucial role in the progress of human gastric cancer. In this study, we show that mefloquine, a FDA-approved anti-malarial drug, effectively targets human gastric cancer cells. Mefloquine potently inhibits proliferation and induces apoptosis of a panel of human gastric cancer cell lines, with EC{sub 50} ∼0.5–0.7 μM. In two independent gastric cancer xenograft mouse models, mefloquine significantly inhibits growth of both tumors. The combination of mefloquine with paclitaxel enhances the activity of either drug alone in in vitro and in vivo. In addition, mefloquine potently decreased phosphorylation of PI3K, Akt, mTOR and rS6. Overexpression of constitutively active Akt significantly restored mefloquine-mediated inhibition of mTOR phosphorylation and growth, and induction of apoptosis, suggesting that mefloquine acts on gastric cancer cells via suppressing PI3K/Akt/mTOR pathway. We further show that mefloquine-mediated inhibition of Akt/mTOR singaling is phosphatase-dependent as pretreatment with calyculin A does-dependently reversed mefloquine-mediated inhibition of Akt/mTOR phosphorylation. Since mefloquine is already available for clinic use, these results suggest that it is a useful addition to the treatment armamentarium for gastric cancer. - Highlights: • Mefloquine targets a panel of gastric cancer cell lines in vitro and in vivo. • Combination of mefloquine and paclitaxel is synergistic. • Mefloquine acts on gastric cancer via inhibition of PI3K/Akt/mTOR pathway. • Mefloquine can be repurposed for gastric cancer treatment.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2016

PRKCI negatively regulates autophagy via PIK3CA/AKT–MTOR signaling

The atypical protein kinase C isoform PRKC iota (PRKCI) plays a key role in cell proliferation, differentiation, and carcinogenesis, and it has been shown to be a human oncogene. Here, we show that PRKCI overexpression in U2OS cells impaired functional autophagy in normal or cell stress conditions, as characterized by decreased levels of light chain 3B-II protein (LC3B-II) and weakened degradation of endogenous and exogenous autophagic substrates. Conversely, PRKCI knockdown by small interference RNA resulted in opposite effects. Additionally, we identified two novel PRKCI mutants, PRKCI{sup L485M} and PRKCI{sup P560R}, which induced autophagy and exhibited dominant negative effects. Further studies indicated that PRKCI knockdown–mediated autophagy was associated with the inactivation of phosphatidylinositol 3-kinase alpha/AKT–mammalian target of rapamycin (PIK3CA/AKT–MTOR) signaling. These data underscore the importance of PRKCI in the regulation of autophagy. Moreover, the finding may be useful in treating PRKCI-overexpressing carcinomas that are characterized by increased levels of autophagy. - Highlights: • The atypical protein kinase C iota isoform (PRKCI) is a human oncogene. • PRKCI overexpression impairs functional autophagy in U2OS cells. • It reduces LC3B-II levels and weakens SQSTM1 and polyQ80 aggregate degradation. • PRKCI knockdown has the opposite effect. • The effect of PRKCI knockdown is related to PIK3CA/AKT–MTOR signaling inactivation.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2016

Ikaros limits follicular B cell activation by regulating B cell receptor signaling pathways

The Ikaros transcription factor is essential for early B cell development, but its effect on mature B cells is debated. We show that Ikaros is required to limit the response of naive splenic B cells to B cell receptor signals. Ikaros deficient follicular B cells grow larger and enter cell cycle faster after anti-IgM stimulation. Unstimulated mutant B cells show deregulation of positive and negative regulators of signal transduction at the mRNA level, and constitutive phosphorylation of ERK, p38, SYK, BTK, AKT and LYN. Stimulation results in enhanced and prolonged ERK and p38 phosphorylation, followed by hyper-proliferation. Pharmacological inhibition of ERK and p38 abrogates the increased proliferative response of Ikaros deficient cells. These results suggest that Ikaros functions as a negative regulator of follicular B cell activation.

60 APPLIED LIFE SCIENCES↗