Bicyclic triterpenoid Iripallidal induces apoptosis and inhibits Akt/mTOR pathway in glioma cells

Genome assembly of the bearded iris, Iris pallida Lam

Irises are perennial plants, representing a large genus with hundreds of species. While cultivated extensively for their ornamental value, commercial interest in irises lies in the secondary metabolites present in their rhizomes. The Dalmatian Iris (Iris pallida Lam.) is an ornamental plant that also produces secondary metabolites with potential value to the fragrance and pharmaceutical industries. In addition to providing base notes for the fragrance industry, iris tissues and extracts possess antioxidant, anti-inflammatory and immunomodulatory effects. However, study of these secondary metabolites has been hampered by a lack of genomic information, requiring difficult extraction and analysis techniques. Here, we report the genome sequence of Iris pallida Lam., generated with Pacific Bioscience long-read sequencing, resulting in a 10.04-Gbp assembly with a scaffold N50 of 14.34 Mbp and 91.8% complete BUSCOs. This reference genome will allow researchers to study the biosynthesis of these secondary metabolites in much greater detail, opening new avenues of investigation for drug discovery and fragrance formulations.

Suppression of FAM83D Inhibits Glioma Proliferation, Invasion and Migration by Regulating the AKT/mTOR Signaling Pathway

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FAM83D is upregulated in the glioma cells and tissues.

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Silencing FAM83D inhibits the proliferation, invasion and migration of glioma cells.

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Silencing FAM83D inhibits the activity of AKT/mTOR signaling pathway.

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FAM83D inhibition limits the in vivo growth of glioma cells.

Objective

To explore the mechanism by which the family with sequence similarity 83, member D (FAM83D)-mediated AKT/mTOR signaling pathway activation affects the proliferation and metastasis of glioma cells.

Methods

FAM83D protein expression in glioma cells and tissues was detected by western blotting. Glioma U87 and U251 cells were selected and divided into the Mock, siNC, siFAM83D, FAM83D, MK2206 and FAM83D + MK2206 groups. Cell proliferation was assessed by MTT (3-[4,5-dimethylthiazol-2-yl]-2,5 diphenyl tetrazolium bromide) and clone formation assays, while invasion and migration were evaluated by Transwell assays and wound healing tests. The protein expression of members of the AKT/mTOR pathway was determined via western blotting. Xenograft models were also established in nude mice to observe the in vivo effect of FAM83D on the growth of glioma.

Results

FAM83D was upregulated in glioma patients, especially in those with Stage III-IV. In addition, cells treated with siFAM83D had significant downregulation of p-AKT/AKT and p-mTOR/mTOR, with decreased proliferation and colony numbers, as well as decreased invasion and migration compared to the Mock group. However, FAM83D overexpression could activate the Akt/mTOR pathway and promote the proliferation, invasion and migration of glioma cells. Moreover, treatment with MK2206, an inhibitor of AKT, reversed the promoting effect of FAM83D on the growth of glioma cells. The in vivo experiments demonstrated that silencing FAM83D could inhibit the in vivo growth of glioma cells

Conclusion

FAM83D was upregulated in glioma and silencing FAM83D suppressed the proliferation, invasion and migration of glioma cells via inhibition of the AKT/mTOR pathway.

ARID4B Knockdown Suppresses PI3K/AKT Signaling and Induces Apoptosis in Human Glioma Cells

PURPOSE

Glioblastoma multiforme is a highly malignant primary brain cancer with a poor prognosis. We recently reported that ARID4B could potentially serve as a biomarker associated with poor survival in glioma patients. However, the function of ARID4B in human gliomas remains unclear. The aim of this study is to investigate the molecular cell biology role of ARID4B in human glioma cells.

MATERIALS AND METHODS

Gene Expression Omnibus (GEO) and Human Protein Atlas (HPA) datasets were analyzed for the expression of ARID4B in WHO pathological grading, overall survival and immunohistochemical staining. Using quantitative RT-PCR and Western blotting, those findings were confirmed in normal brain tissue and glioma cell lines. ARID4B knockdown was conducted via lentivirus-based transfection of small hairpin RNA in human glioma cells to investigate cell proliferation, cell cycle, and apoptosis.

RESULTS

In the present study, our analysis of GEO datasets showed that ARID4B mRNA expression is higher in WHO grade IV tumors (n = 81) than in non-tumor control tissue (n = 23, P <0.0001). ARID4B knockdown suppressed glioma cell proliferation and induced G1 phase arrest via the PI3K/AKT pathway. It also increased expression of HDAC1, leading to higher acetyl-p53 and acetyl-H3 levels and reduced glioma cell migration and invasion. These effects were mediated via downregulation of AKT pathway components, including p-mTOR, p-PI3K and p-AKT. ARID4B knockdown also led to downregulation of Cyclin D1, which increased apoptosis in human glioma cells.

CONCLUSION

These findings that ARID4B expression correlates positively with WHO pathologic grading in glioma. ARID4B knockdown suppresses PI3K/AKT signaling and induces apoptosis in human glioma cells. These results suggests that ARID4B acts as an oncogene in human gliomas.

RasGRP3, a Ras guanyl releasing protein 3 that contributes to malignant proliferation and aggressiveness in human esophageal squamous cell carcinoma

Esophageal squamous cell carcinoma (ESCC) is one of the most common cancers worldwide; however, clinical and pathological parameters have limited ability in discriminating between clinically significant and indolent ESCC. Since RasGRP3 transcript levels have prognostic value in discriminating ESCC with different clinical aggressiveness, we decided to investigate its putative oncogenic role in ESCC. We found that RasGRP3 was highly expressed in ESCC cells. Suppression of endogenous RasGRP3 expression in esophageal cell lines reduced Ras-GTP formation as well as AKT phosphorylation. RasGRP3 suppression also inhibited cell invasion and migration and reduced proliferation, demonstrating the importance of RasGRP3 for the transformed phenotype of melanoma cells. Suppression of RasGRP3 expression in these cells inhibited downstream RasGRP3 responses and suppressed cell growth and migration, confirming the functional role of RasGRP3 in the altered behaviour of these cells. This suggests that RasGRP3 may function as a Ras activator in the phosphoinositide signalling pathway and may potentially serve as a new therapeutic target.

Neuroglobin promotes the proliferation and suppresses the apoptosis of glioma cells by activating the PI3K/AKT pathway

Our previous study demonstrated that neuroglobin (Ngb) functions as an independent predictive indicator of the prognosis of patients with glioma and promotes cancer cell growth by suppressing apoptosis. However, the understanding of the mechanisms underlying the survival‑enhancing function of Ngb in glioma is limited. In the present study, KEGG PathwayFinder by gene correlation analysis was performed on the R2: Genomics Analysis and Visualization Platform, which revealed a high association between Ngb and the phosphatidylinositol 3‑kinase (PI3K)/AKT pathway using glioma data (GSE4290) from the Gene Expression Omnibus database. Furthermore, western blotting experiments were performed in U251 and U87 glioma cells, and Ngb knockdown using short hairpin RNA reduced the protein levels of phosphorylated (p)‑AKT, p‑mammalian target of rapamycin (mTOR) and antiapoptotic factor Bcl‑2, and increased the expression of the proapoptotic protein Bcl‑2‑associated X, in U251 cells. In addition, Ngb overexpression promoted the activation of the PI3K/AKT pathway in U87 cells. MK2206, a PI3K/AKT signaling inhibitor, reduced the expression of p‑AKT and increased the levels of apoptosis‑associated proteins, including cleaved poly(ADP‑ribose) polymerase 1 and cleaved caspase‑3/7/8, in Ngb‑overexpressing U87 cells. Furthermore, MK2206 treatment reduced the proliferation and induced the apoptosis of Ngb‑overexpressing U87 cells, as indicated by the results of MTT, colony formation and flow cytometry assays. In addition, insulin‑like growth factor‑1, a PI3K/AKT signaling activator, reversed Ngb knockdown‑induced growth arrest and apoptosis in U251 cells. In conclusion, the results of the present study indicate that Ngb may facilitate a malignant phenotype of glioma cells by activating the PI3K/AKT pathway.

G9a inhibition induced PKM2 regulates autophagic responses

Epigenetic regulation by histone methyltransferase G9a is known to control autophagic responses. As the link between autophagy and metabolic homeostasis is widely accepted, we investigated whether G9a affects metabolic circuitries to affect autophagic response in glioma cells. Both pharmacological inhibition and siRNA mediated knockdown of G9a increased autophagy marker LC3B in glioma cells. G9a inhibitor BIX-01294 (BIX) induced Akt-dependent increase in HIF-1α expression and activity. Inhibition of Akt-HIF-1α axis reversed BIX-mediated (i) increase in LC3B expression and (ii) decrease in Yes-associated protein 1 (YAP1) phosphorylation. YAP1 over-expression abrogated BIX induced increase in LC3B expression. Interestingly, BIX induced increase in metabolic modelers TIGAR (TP53-induced glycolysis and apoptosis regulator) and PKM2 (Pyruvate kinase M2) were crucial for BIX-mediated changes, as transfection with TIGAR mutant or PKM2 siRNA reversed BIX-mediated alterations in pYAP1 and LC3B expression. Coherent with the in vitro observation, BIX had no significant effect on the tumor burden in heterotypic xenograft glioma mouse model. Elevated LC3B and PKM2 in BIX-treated xenograft tissue was accompanied by decreased YAP1 levels. Taken together, our findings suggest that Akt-HIF-1α axis driven PKM2-YAP1 cross talk activates autophagic responses in glioma cells upon G9a inhibition.

mTOR in Brain Physiology and Pathologies

TOR (target of rapamycin) and its mammalian ortholog mTOR have been discovered in an effort to understand the mechanisms of action of the immunosuppressant drug rapamycin extracted from a bacterium of the Easter Island (Rapa Nui) soil. mTOR is a serine/threonine kinase found in two functionally distinct complexes, mTORC1 and mTORC2, which are differentially regulated by a great number of nutrients such as glucose and amino acids, energy (oxygen and ATP/AMP content), growth factors, hormones, and neurotransmitters. mTOR controls many basic cellular functions such as protein synthesis, energy metabolism, cell size, lipid metabolism, autophagy, mitochondria, and lysosome biogenesis. In addition, mTOR-controlled signaling pathways regulate many integrated physiological functions of the nervous system including neuronal development, synaptic plasticity, memory storage, and cognition. Thus it is not surprising that deregulation of mTOR signaling is associated with many neurological and psychiatric disorders. Preclinical and preliminary clinical studies indicate that inhibition of mTORC1 can be beneficial for some pathological conditions such as epilepsy, cognitive impairment, and brain tumors, whereas stimulation of mTORC1 (direct or indirect) can be beneficial for other pathologies such as depression or axonal growth and regeneration.

Guggulsterone sensitizes glioblastoma cells to Sonic hedgehog inhibitor SANT-1 induced apoptosis in a Ras/NFκB dependent manner

Since Shh pathway effector, Gli1, is overexpressed in gliomas, we investigated the effect of novel Shh inhibitor SANT-1 on glioma cell viability. Though SANT-1 failed to induce apoptosis, it reduced proliferation of glioma stem-like cells. Apart from canonical Shh cascade, Gli1 is also induced by non-canonical pathways including NFκB. Therefore, a combinatorial strategy with Ras/NFκB inhibitor, Guggulsterone, was employed to enhance effectiveness of SANT-1. Guggulsterone inhibited Ras and NFκB activity and sensitized cells to SANT-1 induced apoptosis via intrinsic apoptotic mechanism. Inhibition of either Ras or NFκB activity was sufficient to sensitize cells to SANT-1. Guggulsterone induced ERK activation also contributed to Caspase-9 activation. Since SANT-1 and Guggulsterone differentially target stem-like and non-stem glioma cells respectively, this combination warrants investigation as an effective anti-glioma therapy.

EGFR inhibitor BIBU induces apoptosis and defective autophagy in glioma cells

The importance of aberrant EGFR signaling in glioblastoma progression and the promise of EGFR-specific therapies, prompted us to determine the efficacy of novel EGFR inhibitor BIBU-1361 [(3-chloro-4-fluoro-phenyl)-[6-(4-diethylaminomethyl-piperidin-1-yl)-pyrimido [5,4-d]pyrimidin-4-yl]-amine] in affecting glioma survival. BIBU induced apoptosis in a caspase-dependent manner and induced cell cycle arrest in glioma cells. Apoptosis was accompanied by decreased EGFR levels and its increased distribution towards caveolin rich lipid raft microdomains. BIBU inhibited pro-survival pathways Akt/mTOR and gp130/JAK/STAT3; and decreased levels of pro-inflammatory cytokine IL-6. BIBU caused increased LC3-I to LC3-II conversion and triggered the internalization of EGFR within vacuoles along with its increased co-localization with LC3-II. BIBU caused accumulation of p62 and increased levels of cleaved forms of Beclin-1 in all the cell lines tested. Importantly, BIBU failed to initiate execution of autophagy as pharmacological inhibition of autophagy with 3-Methyladenine or Bafilomycin failed to rescue BIBU mediated death. The ability of BIBU to abrogate Akt and STAT3 activation, induce apoptosis and prevent execution of autophagy warrants its investigation as a potent anti-glioma target.

Inhibition of Casein kinase-2 induces p53-dependent cell cycle arrest and sensitizes glioblastoma cells to tumor necrosis factor (TNFα)-induced apoptosis through SIRT1 inhibition

Glioblastoma multiforme (GBM) are resistant to TNFα-induced apoptosis and blockade of TNFα-induced NF-κB activation sensitizes glioma cells to apoptosis. As Casein kinase-2 (CK2) induces aberrant NF-κB activation and as we observed elevated CK2 levels in GBM tumors, we investigated the potential of CK2 inhibitors (CK2-Is) - DRB and Apigenin in sensitizing glioma cells to TNFα-induced apoptosis. CK2-Is and CK2 small interfering RNA (siRNA) reduced glioma cell viability, inhibited TNFα-mediated NF-κB activation, and sensitized cell to TNFα-induced apoptosis. Importantly, CK2-Is activated p53 function in wild-type but not in p53 mutant cells. Activation of p53 function involved its increased transcriptional activation, DNA-binding ability, increased expression of p53 target genes associated with cell cycle progression and apoptosis. Moreover, CK2-Is decreased telomerase activity and increased senescence in a p53-dependent manner. Apoptotic gene profiling indicated that CK2-Is differentially affect p53 and TNFα targets in p53 wild-type and mutant glioma cells. CK2-I decreased MDM2-p53 association and p53 ubiquitination to enhance p53 levels. Interestingly, CK2-Is downregulated SIRT1 activity and over-expression of SIRT1 decreased p53 transcriptional activity and rescued cells from CK2-I-induced apoptosis. This ability of CK2-Is to sensitize glioma to TNFα-induced death via multiple mechanisms involving abrogation of NF-κB activation, reactivation of wild-type p53 function and SIRT1 inhibition warrants investigation.

Rac-dependent doubling of HeLa cell area and impairment of cell migration and cell cycle by compounds from Iris germanica

Plants are an infinite source of bioactive compounds. We screened the Israeli flora for compounds that interfere with the organization of the actin cytoskeleton. We found an activity in lipidic extract from Iris germanica that was able to increase HeLa cell area and adhesion and augment the formation of actin stress fibers. This effect was not observed when Ref52 fibroblasts were tested and was not the result of disruption of microtubules. Further, the increase in cell area was Rac1-dependent, and the iris extract led to slight Rac activation. Inhibitor of RhoA kinase did not interfere with the ability of the iris extract to increase HeLa cell area. The increase in HeLa cell area in the presence of iris extract was accompanied by impairment of cell migration and arrest of the cell cycle at G1 although the involvement of Rac1 in these processes is not clear. Biochemical verification of the extract based on activity-mediated fractionation and nuclear magnetic resonance analysis revealed that the active compounds belong to the group of iridals, a known group of triterpenoid. Purified iripallidal was able to increase cell area of both HeLa and SW480 cells.

Centchroman inhibits proliferation of head and neck cancer cells through the modulation of PI3K/mTOR pathway

Centchroman (CC; 67/20; INN: Ormeloxifene) is a non-steroidal antiestrogen extensively used as a female contraceptive in India. In the present study, we report the anti-proliferative effect of CC in head and neck squamous cell carcinoma (HNSCC) cells. CC inhibited cell proliferation in a dose dependent manner at 24 h of treatment. Further studies showed that CC treatment induced apoptosis, inhibited Akt/mTOR and signal transducers and activators of transcription protein 3 (STAT3) signaling, altered proteins associated with cell cycle regulation and DNA damage and inhibited colony forming efficiency of HNSCC cells. In addition, CC displayed anti-proliferative activity against a variety of non-HNSCC cell lines of diverse origin. The ability of CC to serve as a dual-inhibitor of Akt/mTOR and STAT3 signaling warrants further studies into its role as a therapeutic strategy against HNSCC.