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PubMed2005

Pure lipopolysaccharide or synthetic lipid A induces activation of p21Ras in primary macrophages through a pathway dependent on Src family kinases and PI3K.

Recognition of bacterial LPS by macrophages plays a critical role in host defense against infection by Gram-negative bacteria. However, when not tightly regulated, the macrophage's response to LPS can induce severe disease and septic shock. Although LPS triggers the activation of multiple signaling pathways in macrophages, it was unclear whether these include activation of the p21Ras GTPases. We report that p21Ras is rapidly and transiently activated in murine primary macrophages stimulated with an ultra-pure preparation of LPS or with synthetic lipid A. The molecular basis of this activation was investigated using a pharmacological approach. LPS-induced activation of p21Ras was inhibited in the presence of PP2, LY294002, or wortmannin, suggesting that it depends on the activity of one or more members of the Src kinase family and the subsequent activation of PI3K. In that pharmacological inhibitors of PI3K inhibited LPS-induced activation of p21Ras, but not activation of ERK, we concluded that LPS-induced activation of ERK occurs through a pathway that is not dependent on the activation of p21Ras.

Animals↗

PubMed2006

Anti-HER2 antibody trastuzumab inhibits CDK2-mediated NPAT and histone H4 expression via the PI3K pathway.

The anti-HER2 antibody trastuzumab (Herceptin) has been used to treat patients with breast cancers that overexpress HER2. We have demonstrated that p27(Kip1) upregulation is one of the key events that cause G(1) arrest upon trastuzumab treatment. Here, we have examined the effect of trastuzumab on expression of CDK2, Rb, E2F, NPAT and histone H4 in breast cancer cells that overexpress HER2. Trastuzumab treatment dramatically inhibited the kinase activity and expression of CDK2, whereas the kinase activity and expression of CDK4 were not affected. Unlike the p27(Kip1) upregulation that occurs primarily through post-translational mechanisms, CDK2 was downregulated primarily at a transcriptional level as shown by Northern blotting and real-time RT-PCR analyses. With a decrease in CDK2 activity, trastuzumab decreased the kinase activity of cyclin E but had little effect on cyclin E protein level. Overexpression of wild-type cyclin E or its lower molecular weight forms did not influence the response to trastuzumab. Levels and activities of CDK6, cyclin A, and cyclin D1 were all suppressed by trastuzumab. As a result, trastuzumab inhibited Rb phosphorylation that associates with CDK2, cyclin E, CDK6, cyclin A, or cyclin D1. As predicted from these changes, trastuzumab decreased the DNA-binding activity of E2F, decreased the level of NPAT protein, and decreased the level of histone H4 mRNA. Blockade of the PI3K pathway with LY294002 produced similar effects to trastuzumab treatment on expression of each of these genes. Taken together, treatment of breast cancer cells that overexpress HER2 with the anti-HER2 antibody trastuzumab inhibits CDK2, Rb phosphorylation, E2F activity, NPAT, and histone H4 via PI3K signaling that are needed for both DNA and histone synthesis during progression from G(1) phase to S phase of the cell cycle.

Antibodies, Monoclonal↗

PubMed2000

The PI3K-PDK1 connection: more than just a road to PKB.

Phosphoinositide 3-kinases (PI3Ks) generate specific inositol lipids that have been implicated in the regulation of cell growth, proliferation, survival, differentiation and cytoskeletal changes. One of the best characterized targets of PI3K lipid products is the protein kinase Akt or protein kinase B (PKB). In quiescent cells, PKB resides in the cytosol in a low-activity conformation. Upon cellular stimulation, PKB is activated through recruitment to cellular membranes by PI3K lipid products and phosphorylation by 3'-phosphoinositide-dependent kinase-1 (PDK1). Here we review the mechanism by which PKB is activated and the downstream actions of this multifunctional kinase. We also discuss the evidence that PDK1 may be involved in the activation of protein kinases other than PKB, the mechanisms by which this activity of PDK1 could be regulated and the possibility that some of the currently postulated PKB substrates targets might in fact be phosphorylated by PDK1-regulated kinases other than PKB.

3-Phosphoinositide-Dependent Protein Kinases↗

PubMed2002

PI3K and PLCgamma play a central role in experimental PVR.

PURPOSE: It has been reported that the platelet-derived growth factor (PDGF)-alpha receptor (alphaPDGFR) is required for experimental proliferative vitreoretinopathy (PVR) in rabbits. This study investigated which of the signaling enzymes downstream of the alphaPDGFR participate in PVR. METHODS: A panel of cell lines that expressed alphaPDGFR signaling mutants were made and characterized. These cell lines were used in a rabbit model of PVR and in an in vitro collagen type I contraction assay. RESULTS: Phosphoinositide 3-kinase (PI3K) and, to a lesser extent, phospholipase C (PLC)-gamma were the signaling enzymes required for the alphaPDGFR to mediate PVR. Furthermore, the cells lines that were the most effective at inducing PVR displayed the most potent activity in the in vitro contraction assay. CONCLUSIONS: PI3K and PLCgamma are necessary downstream effectors of the alphaPDGFR in experimental PVR. Consequently, these two signaling enzymes are required for one or more of the cellular responses (chemotaxis, proliferation, extracellular matrix production, contraction) that contribute to PVR.

Animals↗

PubMed2004

[Overexpression of HER2/neu downregulates wild p53 protein expression via PI3K and Ras/Raf/MEK/ERK pathways in human breast cancer cells].

OBJECTIVE: To evaluate the effect of HER2/neu overexpression on wild p53 protein expression and to delineate the related signal pathways. METHODS: Lipofectin method was used to transfer HER2/neu into human breast tumor cell line MCF7. Overexpression of HER2/neu was then determined by Western blot. Western blot was also used to detect the quantity of p53, Akt, p-Akt, p-Raf, p-MEK, p-ERK protein. Semi-quantitative reverse transcriptase-polymerase chain reaction (RT-PCR) was employed to detect p53 mRNA expression. PI3K pathway inhibitor LY294002 and MEK inhibitor U0126 were used to block the two pathways. The subsequent effect on p53 protein expression was then determined. RESULTS: HER2/neu-overexpressed MCF7 clone (MCF7-neu3) was successfully established, in which the amount of HER2/neu protein was 13 times more than that in parental MCF7 cells. The amount of p53 protein in MCF7-neu3 was 40% of that in parental MCF7 cells (P < 0.01), while there was no difference on p53 mRNA level. There were 2.5, 2.0, 1.6 and 1.6 fold increase in the amount of p-Akt, p-Raf, p-MEK, p-ERK protein respectively in MCF7-neu3 to that in parental MCF7 cells (P < 0.01). When treated with LY294002 or U0126 for 24 hours, the amount of wild p53 protein in MCF7-neu3 cells was 1.7 or 1.5 times higher than those in DMSO treated cells. There were 4.7 or 5.3 times increase in the p53 protein when MCF7-neu3 cells were treated with LY294002 or U0126 for 48 hours (P < 0.01). Similar results were not seen in MDA-MB-453 cells which contained mutant p53. CONCLUSIONS: HER2/neu overexpression can activate PI3K and Ras/Raf/MEK/ERK pathways, resulting in reduction of wild p53 protein expression. This may be the molecular mechanism responsible for the poor prognosis and therapeutic non-responsiveness in HER2/neu-overexpressed breast cancer patients.

Breast Neoplasms↗

PubMed2005

A role for PI3K-Akt signaling in pulmonary metastatic nodule formation of the osteosarcoma cell line, LM8.

To search for the intracellular signaling pathway critical for the pulmonary metastasis of osteosarcoma, we examined two osteosarcoma cell lines with different metastatic capability, Dunn and LM8. While parental Dunn is poorly metastatic to lung, LM8, derived from Dunn by in vivo selection through pulmonary metastasis, displays clear capability of pulmonary metastasis. We found that LM8 had higher levels of Akt phosphorylation and Ezrin expression than Dunn. In contrast, no clear difference was observed between Dunn and LM8 in other signaling mediators, including MAPK, SAPK and Stat3. In contrast to Dunn, LM8 secreted higher levels of matrix metalloproteinase-2 and -9, showed higher levels of invasiveness and cell motility, and displayed strong pulmonary metastasis. Inhibition of PI3K-Akt signaling in LM8 by a PI3K inhibitor, LY294002, or by a dominant negative form of Akt, resulted in suppression of MMP secretion, in vitro invasiveness, cell locomotion and in vivo pulmonary metastasis. In contrast, expression of an active form of Akt in Dunn substantially activated its MMP secretion, in vitro invasiveness, cell locomotion and in vivo pulmonary metastasis. Taken together, our results demonstrate, for the first time, an important role of Akt signaling in pulmonary metastasis of osteosarcoma.

Cell Line, Tumor↗

PubMed2006

[PI3K-AKT-mTOR pathway inhibitors].

Molecular targeted agents have enlarged the armamentarium of anti-cancer therapies. Along with the success of some anti-growth factor receptors, signal transduction inhibitors represent a promising anti-cancer strategy. The PI3K-AKT-mTOR pathway is a key pathway frequently altered in cancer cells. This manuscript provides an overview of the PI3K-AKT-mTOR pathway and its targeting in human malignancies. A focus is delivered for mTOR inhibitors.

Antineoplastic Agents↗

PubMedDate not supplied

Suppression of pro-metastasis phenotypes expression in malignant pleural mesothelioma by the PI3K inhibitor LY294002 or the MEK inhibitor UO126.

BACKGROUND: This study aimed to evaluate the impact of selective abrogation of either the MEK/ERK1/2 (UO126 or PD98059) or the PI3K/AKT (LY294002) signaling cascade on cell proliferation, motility and invasion and production of VEGF (collectively termed pro-metastasis phenotypes) in cultured malignant pleural mesothelioma (MPM) cells. MATERIALS AND METHODS: Treatment-induced cytotoxicity was evaluated by MTT or Annexin V assays. Cell motility was assessed by wound healing and Matrigel invasion assays. VEGF in conditioned media of cancer cells was measured by ELISA. RESULTS: LY294002 and UO126 significantly inhibited cell proliferation and clonogenicity of MPM cells in vitro. A substantial reduction of cell motility, Matrigel invasion as well as inhibition of basal or EGF-induced VEGF production were observed in drug-treated cells. CONCLUSION: The selective MEK or PI3K kinase inhibitors are equally effective in down-regulating the expression of pro-metastasis phenotypes, suggesting that MEK or PI3K are appropriate targets for the development of molecular therapeutics for malignant pleural mesothelioma.

Butadienes↗

PubMed1994

Substrate specificities and identification of a putative binding site for PI3K in the carboxy tail of the murine Flt3 receptor tyrosine kinase.

Flt3 is a receptor tyrosine kinase (RTK) structurally related to the CSF-1R encoded by the c-fms locus, Kit and the PDGFR which is restricted in its expression to hematopoietic precursor populations and several distinct cell types within the central nervous system. Although the ligand for Flt3 has recently been identified, the developmental function of Flt3 within these tissues has not yet been described. In order to examine the signalling properties of this receptor, we previously constructed a chimeric molecule containing the extracellular domain of CSF-1R fused to the transmembrane and cytoplasmic domain of mouse Flt3 (FF3). The ability of the FF3 to directly associate with or tyrosine phosphorylate specific cytoplasmic signalling molecules in vivo was examined. GAP, Vav, Shc, and to a lesser extent PLC gamma become tyrosine-phosphorylated but no in vivo association with the receptor was detectable. FF3 associates with PI3K activity and the SH2 domains of p85 and Grb-2. Phosphopeptide competition experiments suggest that the PI3K binding site is located outside of the kinase insert in the carboxy tail of the receptor.

Amino Acid Sequence↗

PubMed2026

A PMS2-deficient pediatric high-grade glioma with PI3K-pathway mutations and adjacent developmental venous anomaly suggestive of CMMRD.

PURPOSE: Constitutional mismatch repair deficiency (CMMRD) is a rare hereditary cancer predisposition syndrome that frequently manifests with pediatric high-grade gliomas. However, recognition remains challenging, particularly in the absence of a clear family history. We report a pediatric high-grade glioma with PMS2 deficiency and complex molecular alterations to highlight key diagnostic clues and the importance of routine mismatch repair assessment. METHODS: Clinical, radiological, histopathological, immunohistochemical, and molecular findings of an 8-year-old girl presenting with a high-grade glioma were retrospectively evaluated. Immunohistochemistry included glial and mismatch repair markers. Targeted next-generation sequencing was performed to assess tumor mutational burden and pathogenic variants. RESULTS: Neuroimaging revealed a right frontoparietal mass associated with an adjacent developmental venous anomaly. Histopathology demonstrated a diffuse pediatric-type high-grade glioma with pseudopapillary architecture and marked mitotic activity. Immunohistochemistry showed diffuse p53 overexpression in tumor cells and complete loss of PMS2 expression in both tumor and non-neoplastic cells, supporting constitutional mismatch repair deficiency. Molecular analysis revealed an ultra-hypermutated profile with a tumor mutational burden of 117.4 mutations/Mb, a pathogenic PMS2 frameshift variant, and co-occurring alterations in TP53, PIK3CA, PIK3R1, and PTEN. The presence of PI3K-pathway mutations alongside a venous anomaly suggested a potential biological association. CONCLUSION: This case illustrates the characteristic clinicopathological and molecular features of CMMRD-associated pediatric high-grade glioma and underscores the critical role of routine mismatch repair immunohistochemistry. Integrated histological and genomic evaluation is essential for accurate diagnosis, appropriate genetic counseling, and potential therapeutic implications. Key Points • This case represents a pediatric high-grade glioma arising in the setting of PMS2-related constitutional mismatch repair deficiency (CMMRD). • The tumor exhibited an ultra-hypermutated profile with co-occurring TP53, PIK3CA, PIK3R1, and PTEN mutations. • Loss of PMS2 expression in both tumor and non-neoplastic cells was critical in establishing the diagnosis of CMMRD. • The presence of a developmental venous anomaly may relate to underlying PIK3R1 pathway alterations. • Routine mismatch repair immunohistochemistry is essential in pediatric high-grade gliomas, even in the absence of a family history.

Humans↗

PubMed2002

Regulation of cell size in growth, development and human disease: PI3K, PKB and S6K.

It has generally been observed that cells grow to a certain size before they divide. In the last few years, the PI3K signal transduction pathway has emerged as one of the main signaling routes utilized by cells to control their increase in size. Here we focus on two components of this pathway, PKB and S6K, and briefly review the experiments that initially uncovered their roles in cell size control. In addition, we discuss a number of recent observations suggesting that the generic models used to describe this pathway to date may have been oversimplified. Indeed, recent observations in Drosophila and mouse support a more complex interaction between these signaling components in development. Finally, we have utilized two contemporary studies involving PKB- and S6K-deficient mice as a paradigm to underscore the importance of cell size and to accurately delineate the connections between signaling pathways for human disease, such as diabetes mellitus.

Animals↗

PubMed1998

cDNA cloning of a third human C2-domain-containing class II phosphoinositide 3-kinase, PI3K-C2gamma, and chromosomal assignment of this gene (PIK3C2G) to 12p12.

Phosphoinositide (PI) 3-kinases have been shown to have critical roles in signaling pathways that regulate proliferation, oncogenic transformation, cell survival, cell migration, and intracellular protein trafficking. We have previously used reverse-transcription polymerase chain reaction methods to identify novel PI 3-kinase isoforms in normal human breast and in lymph nodes containing metastatic breast cancer. Here we report the cDNA cloning of a Class II PI 3-kinase found in normal breast tissue. This gene (PIK3C2G) encodes the third distinct protein of the human Class II PI 3-kinase family, PI3K-C2gamma. PIK3C2G was mapped to chromosome 12 at 12p12 by fluorescence in situ hybridization.

Amino Acid Sequence↗

PubMed2003

Inhibition of the PI3K-Akt signaling pathway enhances the sensitivity of Fas-mediated apoptosis in human gastric carcinoma cell line, MKN-45.

It is well known that Fas ligand and anti-Fas antibodies can induce apoptosis, although some cancer cells are resistant to their stimuli. On the other hand, phosphatidylinositol 3'-kinase (PI3 K) and Akt mediate the survival signal and allow the cells to escape from apoptosis in various human cancers. Thus, we postulated that LY294002, a PI3 K inhibitor, should inactivate Akt, consequently inhibiting cell proliferation and increase apoptosis in the human gastric carcinoma cell line, MKN-45. Previously, we reported that MKN-45 was resistant against the anti-Fas antibody, CH-11, without interferon-gamma pretreatment in vitro. LY294002 caused a decrease of phosphorylated-Akt and an inhibition of cell proliferation via cell cycle arrest in the G0/G1 phase by P27/Kip1 accumulation, but there was no obvious induction of apoptosis. The simultaneous treatment of LY294002 and CH-11 significantly induced apoptosis confirmed by morphology and DNA ladder formation. Decreased phosphorylated-Akt by LY294002 treatment led to a down-regulation of Mcl-2 and phosphorylated Bad proteins, which are anti-apoptotic factors and belong to the Bcl-2 family. On the other hand, expression levels of the other anti-apoptotic factors, such as FLICE-inhibitory protein (FLIP), Bcl-2 and Bcl-XL, which are associated with the Fas-mediated apoptotic signal pathway, did not change after LY294002 treatment. We concluded that: 1) the PI3K-Akt pathway plays an important role in preventing Fas-mediated apoptosis; and 2) a PI3 K inhibitor, such as LY294002, might be a useful anti-tumoral agent for gastric carcinoma.

Antineoplastic Agents↗

PubMed2026

TET2 promotes monocyte inflammatory activation in asthma via ALKBH5-m6A regulation and PI3K signaling: evidence from m6A-SNP and single-cell analyses.

Asthma is a complex inflammatory airway disease with strong genetic determinants, yet the functional relevance of most asthma-associated non-coding variants remains unclear. Emerging evidence suggests that N6-methyladenosine (m6A) modification may serve as a critical epitranscriptomic link between genetic variation and immune regulation. In this study, we aimed to systematically identify functionally relevant m6A-regulated genes in asthma by integrating large-scale GWAS data, m6A-SNP annotations, and single-cell transcriptomic analyses, and to investigate their roles in monocyte-driven airway inflammation. We identified TET2 as a key m6A-regulated gene associated with both asthma and lung function, which was selectively upregulated in monocytes during asthma and accompanied by activation of inflammatory and PI3K signaling pathways. Mechanistic experiments further demonstrated that inflammatory stimulation induced ALKBH5 expression, reduced m6A modification of TET2 mRNA, and increased TET2 protein levels, thereby promoting PI3K/AKT signaling and pro-inflammatory cytokine production, whereas inhibition of TET2 or ALKBH5 attenuated these effects. Collectively, these findings demonstrate that ALKBH5-mediated m6A regulation of TET2 enhances PI3K/AKT signaling in monocytes, thereby promoting inflammatory responses in asthma. Our study establishes TET2 as a key m6A-regulated gene linking genetic susceptibility to monocyte-driven inflammation, and highlights the ALKBH5-m6A-TET2 axis as a potential therapeutic target for modulating aberrant immune responses in asthma.

Humans↗

PubMed2026

Proteomic regulation of anti-proliferative and anti-migratory activity by potent phytochemicals from Pistacia integerrima J.L. Steward Ex Brandis via PI3K, AKT1, and KRAS for Lung Cancer.

BACKGROUND: Non-small cell lung cancer (NSCLC) is the leading cause of mortality worldwide and remains a major therapeutic challenge due to high metastasis, drug resistance and limited treatments. Pistacia integerrima J.L. Steward Ex Brandis (PI) consists of flavonoids, steroids, terpenoids and phenolic compounds reported for pharmacological activities. The efficacy of potent bioactives from P. integerrima may be ascertained employing cytotoxic, antiproliferative, anti-migratory, and anti-metastatic evaluations in A549 NSCLC cells with proteomic profiling, molecular docking, and dynamics simulation study. METHODS AND RESULTS: PI EtAc produced significant dose-dependent cytotoxicity in A549 cells (100 µg/mL, p < 0.0001 in the MTT assay. There was a pronounced decrease in colony formation after treatment with EtAc, with 18.41% (p < 0.002), and markedly. Furthermore. PI EtAC markedly inhibited cell migration emphasized by wound healing and Transwell migration (p < 0.01) assays, indicating reduced metastatic migratory potential. Proteomic analysis demonstrated significant downregulation of Endoglin (CD105), KLK5 and MMP-2, indicating suppression of angiogenic and metastatic signalling pathways in the Human XL Oncology protein array. The interaction of major PI phytochemicals with key NSCLC-associated targets was recorded in Molecular docking, revealing favourable binding affinities of kaempferol, β- sitosterol, luteolin, and quercetin towards several oncogenic targets, including AKT1(- 7.6 kcal/mol), PI3K(- 9.4 kcal/mol), KRAS (- 8.5 kcal/mol) and MMP9 (- 8.1 kcal/mol). Molecular dynamics simulation confirmed the structural stability of the kaempferol -AKT1 complex throughout the 100 ns simulation. CONCLUSION: Pistacia integerrima bioactives exhibited significant anti-proliferative, anti-migratory, and anti-metastatic activities in vitro, which may provide scientific rationale identifying newer promising candidates for NSCLC.

Humans↗

PubMed2004

Beta-adrenergic stimulation induces interleukin-18 expression via beta2-AR, PI3K, Akt, IKK, and NF-kappaB.

We investigated whether beta-adrenergic receptor (beta-AR) stimulation induces the expression of interleukin (IL)-18, a proinflammatory cytokine, in myocardium and in cardiac-derived endothelial cells (CDEC) via activation of nuclear factor (NF)-kappaB. Our results indicate that isoproterenol (ISO) activates NF-kappaB DNA binding activity, and induces myocardial and systemic elaboration of IL-18 via beta2-AR signaling. Furthermore, in CDEC, ISO increased basal and inducible promoter activities, increased IL-18 gene transcription and mRNA stability, and induced IL-18 expression via beta2-AR agonism. Signaling required GiPI3K, PI3K, Akt, IKK, and NF-kappaB. In conclusion, our results indicate for the first time that isoproterenol induces myocardial and systemic elaboration of IL-18 via a beta2-AR and NF-kappaB-dependent mechanism. Similar events may occur in heart failure, a disease state characterized by sustained beta-AR activation.

Adrenergic beta-Agonists↗

PubMed2006

PI3K-Akt inactivation induced CHOP expression in endoplasmic reticulum-stressed cells.

Stress signals that impair the function of the endoplasmic reticulum (ER) can lead to an accumulation of unfolded proteins in the ER causing cell death. Recent studies have indicated that ER stress contributes to several diseases such as neurodegenerative disorders or diabetes. In the present study, we found that Akt down-regulation is important for inducing CHOP expression, an ER stress-induced transcription factor. Treatment with tunicamycin or thapsigargin, ER stress inducers, caused dephosphorylation of Akt from 12 to 24 h and induced cell death. Interestingly, treatment with a PI3K inhibitor alone induced CHOP expression and caused cell death. However, a MEK1 inhibitor induced neither CHOP expression nor cell death. These results indicate that the inactivation of Akt by ER stress induces CHOP expression and causes cell death. Therefore, Akt plays an important role in ER stressed condition and may have important implications for understanding ER stress-related diseases.

Animals↗

PubMed2006

EGFR signaling pathway negatively regulates PSA expression and secretion via the PI3K-Akt pathway in LNCaP prostate cancer cells.

Epidermal growth factor (EGF) and its receptor (EGFR) are involved in hormone-refractory growth and poor prognosis of a subgroup of human prostate cancer. In this communication, we investigated the regulation of PSA by the EGFR signaling pathway using LNCaP C-81 prostate cancer cells. Administration of EGF stimulated the growth of LNCaP C-81 cells, however, PSA expression and secretion were suppressed. An EGFR inhibitor, AG1478, abrogated the PSA suppression effect by EGF, in concurrence with the suppression of tyro-phosphorylation levels of EGFR. Interestingly, the AR level was also decreased in EGF-treated LNCaP C-81 cells. Moreover, LY294002, but not PD98059, inhibited the PSA and AR suppression effect by EGF in concurrence with the suppression of phosphorylation levels of Akt. In conclusion, our results strongly suggest the existence of a novel androgen-independent PSA regulatory mechanism, i.e., the EGFR signaling pathway negatively regulates PSA expression which may be induced by the alteration of AR expression via the PI3K-Akt pathway in LNCaP C-81 cells.

Androgens↗