scholarly journals Double PIK3CA mutations in cis increase oncogenicity and sensitivity to PI3Kα inhibitors

Science ◽  
2019 ◽  
Vol 366 (6466) ◽  
pp. 714-723 ◽  
Author(s):  
Neil Vasan ◽  
Pedram Razavi ◽  
Jared L. Johnson ◽  
Hong Shao ◽  
Hardik Shah ◽  
...  
Keyword(s):  
Membrane Lipid ◽  
Lipid Binding ◽  
Breast Cancers ◽  
Pik3ca Mutations ◽  
Downstream Signaling ◽  
Activating Mutations ◽  
Increased Sensitivity ◽  
Phosphoinositide 3 Kinase ◽  
Tumor Types ◽  
In Cis

Activating mutations in PIK3CA are frequent in human breast cancer, and phosphoinositide 3-kinase alpha (PI3Kα) inhibitors have been approved for therapy. To characterize determinants of sensitivity to these agents, we analyzed PIK3CA-mutant cancer genomes and observed the presence of multiple PIK3CA mutations in 12 to 15% of breast cancers and other tumor types, most of which (95%) are double mutations. Double PIK3CA mutations are in cis on the same allele and result in increased PI3K activity, enhanced downstream signaling, increased cell proliferation, and tumor growth. The biochemical mechanisms of dual mutations include increased disruption of p110α binding to the inhibitory subunit p85α, which relieves its catalytic inhibition, and increased p110α membrane lipid binding. Double PIK3CA mutations predict increased sensitivity to PI3Kα inhibitors compared with single-hotspot mutations.

scholarly journals CD44/HA signaling mediates acquired resistance to a PI3Kα inhibitor

2020 ◽  
Vol 11 (10) ◽  
Author(s):  
Cuixia Yang ◽  
Yumeng Sheng ◽  
Xiaoxing Shi ◽  
Yiwen Liu ◽  
Yiqing He ◽  
...  
Keyword(s):  
Acquired Resistance ◽  
Erk Signaling ◽  
Signaling Cascade ◽  
Breast Cancers ◽  
Pik3ca Mutations ◽  
Adaptive Resistance ◽  
Underlying Mechanisms ◽  
Phosphoinositide 3 Kinase ◽  
Pathway Inhibition ◽  
Mtor Activity

Abstract Most luminal breast carcinomas (BrCas) bearing PIK3CA mutations initially respond to phosphoinositide-3-kinase (PI3K)-α inhibitors, but many eventually become resistant. The underlying mechanisms of this resistance remain obscure. In this work, we showed that a CD44high state due to aberrant isoform splicing was acquired from adaptive resistance to a PI3Kα inhibitor (BLY719) in luminal BrCas. Notably, the expression of CD44 was positively correlated with estrogen receptor (ER) activity in PIK3CA-mutant breast cancers, and ER-dependent transcription upon PI3Kα pathway inhibition was in turn mediated by CD44. Furthermore, the interaction of CD44 with the ligand hyaluronan (HA) initiated the Src-ERK signaling cascade, which subsequently maintained AKT and mTOR activity in the presence of a PI3Kα inhibitor. Activation of this pathway was prevented by disruption of the CD44/HA interaction, which in turn restored sensitivity to BLY719. Our results revealed that an ER-CD44-HA signaling circuit that mediates robust compensatory activation of the Src-ERK signaling cascade may contribute to the development of acquired resistance to PI3Kα inhibitors. This study provides new insight into the mechanism of adaptive resistance to PI3Kα inhibition therapy.

Inhibition of Platelet Aggregation by Ethanol in Vitro Shows Specificity for Aggregating Agent Used and Is Influenced by Platelet Lipid Composition

1982 ◽  
Vol 48 (01) ◽  
pp. 049-053 ◽  
Author(s):  
C G Fenn ◽  
J M Littleton
Keyword(s):  
Platelet Aggregation ◽  
Lipid Composition ◽  
Saturated Fatty Acids ◽  
Calcium Ionophore ◽  
Cholesterol Content ◽  
Membrane Lipid ◽  
Calcium Ionophore A23187 ◽  
Ionophore A23187 ◽  
Increased Sensitivity

SummaryEthanol at physiologically tolerable concentrations inhibited platelet aggregation in vitro in a relatively specific way, which may be influenced by platelet membrane lipid composition. Aggregation to collagen, calcium ionophore A23187 and thrombin (low doses) were often markedly inhibited by ethanol, adrenaline and ADP responses were little affected, and aggregation to exogenous arachidonic acid was actually potentiated by ethanol. Aggregation to collagen, thrombin and A23187 was inhibited more by ethanol in platelets enriched with saturated fatty acids than in those enriched with unsaturated fats. Platelets enriched with cholesterol showed increased sensitivity to ADP, arachidonate and adrenaline but this increase in cholesterol content did not appear to influence the inhibition by ethanol of platelet responses. The results suggest that ethanol may inhibit aggregation by an effect on membrane fluidity and/or calcium mobilization resulting in decreased activity of a membrane-bound phospholipase.

scholarly journals Triple-Knockout, Synuclein-Free Mice Display Compromised Lipid Pattern

Molecules ◽  
2021 ◽  
Vol 26 (11) ◽  
pp. 3078
Author(s):  
Irina A. Guschina ◽  
Natalia Ninkina ◽  
Andrei Roman ◽  
Mikhail V. Pokrovskiy ◽  
Vladimir L. Buchman
Keyword(s):  
Fatty Acids ◽  
Lipid Metabolism ◽  
Family Members ◽  
Ether Lipid ◽  
Brain Regions ◽  
Membrane Lipid ◽  
Lipid Binding ◽  
Synaptic Functions ◽  
Ethanolamine Plasmalogens ◽  
Lipid Pattern

Recent studies have implicated synucleins in several reactions during the biosynthesis of lipids and fatty acids in addition to their recognised role in membrane lipid binding and synaptic functions. These are among aspects of decreased synuclein functions that are still poorly acknowledged especially in regard to pathogenesis in Parkinson’s disease. Here, we aimed to add to existing knowledge of synuclein deficiency (i.e., the lack of all three family members), with respect to changes in fatty acids and lipids in plasma, liver, and two brain regions in triple synuclein-knockout (TKO) mice. We describe changes of long-chain polyunsaturated fatty acids (LCPUFA) and palmitic acid in liver and plasma, reduced triacylglycerol (TAG) accumulation in liver and non-esterified fatty acids in plasma of synuclein free mice. In midbrain, we observed counterbalanced changes in the relative concentrations of phosphatidylcholine (PC) and cerebrosides (CER). We also recorded a notable reduction in ethanolamine plasmalogens in the midbrain of synuclein free mice, which is an important finding since the abnormal ether lipid metabolism usually associated with neurological disorders. In summary, our data demonstrates that synuclein deficiency results in alterations of the PUFA synthesis, storage lipid accumulation in the liver, and the reduction of plasmalogens and CER, those polar lipids which are principal compounds of lipid rafts in many tissues. An ablation of all three synuclein family members causes more profound changes in lipid metabolism than changes previously shown to be associated with γ-synuclein deficiency alone. Possible mechanisms by which synuclein deficiency may govern the reported modifications of lipid metabolism in TKO mice are proposed and discussed.

scholarly journals Repositioning metformin and propranolol for colorectal and triple negative breast cancers treatment

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
L. E. Anselmino ◽  
M. V. Baglioni ◽  
F. Malizia ◽  
N. Cesatti Laluce ◽  
C. Borini Etichetti ◽  
...  
Keyword(s):  
Breast Cancer ◽  
Side Effects ◽  
Triple Negative ◽  
Epithelial Mesenchymal Transition ◽  
Drug Repositioning ◽  
Combined Treatment ◽  
Alternative Therapy ◽  
Breast Cancers ◽  
Mesenchymal Transition ◽  
Tumor Types

AbstractDrug repositioning refers to new uses for existing drugs outside the scope of the original medical indications. This approach fastens the process of drug development allowing finding effective drugs with reduced side effects and lower costs. Colorectal cancer (CRC) is often diagnosed at advanced stages, when the probability of chemotherapy resistance is higher. Triple negative breast cancer (TNBC) is the most aggressive type of breast cancer, highly metastatic and difficult to treat. For both tumor types, available treatments are generally associated to severe side effects. In our work, we explored the effect of combining metformin and propranolol, two repositioned drugs, in both tumor types. We demonstrate that treatment affects viability, epithelial-mesenchymal transition and migratory potential of CRC cells as we described before for TNBC. We show that combined treatment affects different steps leading to metastasis in TNBC. Moreover, combined treatment is also effective preventing the development of 5-FU resistant CRC. Our data suggest that combination of metformin and propranolol could be useful as a putative adjuvant treatment for both TNBC and CRC and an alternative for chemo-resistant CRC, providing a low-cost alternative therapy without associated toxicity.

scholarly journals High EGFR protein expression and exon 9 PIK3CA mutations are independent prognostic factors in triple negative breast cancers

BMC Cancer ◽  
2015 ◽  
Vol 15 (1) ◽  
Author(s):  
William Jacot ◽  
Caroline Mollevi ◽  
Frédéric Fina ◽  
Evelyne Lopez-Crapez ◽  
Pierre-Marie Martin ◽  
...  
Keyword(s):  
Prognostic Factors ◽  
Protein Expression ◽  
Triple Negative ◽  
Breast Cancers ◽  
Pik3ca Mutations ◽  
Exon 9

PIK3CA Mutations are Common in Many Tumor Types and are Often Associated With Other Driver Mutations

2016 ◽  
Vol 24 (5) ◽  
pp. 313-319 ◽  
Author(s):  
Matthew D. Stachler ◽  
Elizabeth M. Rinehart ◽  
Elizabeth Garcia ◽  
Neal I. Lindeman
Keyword(s):  
Driver Mutations ◽  
Pik3ca Mutations ◽  
Tumor Types

scholarly journals Oxidative Stress-Related Mechanisms in Melanoma and in the Acquired Resistance to Targeted Therapies

Antioxidants ◽  
2021 ◽  
Vol 10 (12) ◽  
pp. 1942
Author(s):  
Stefania Pizzimenti ◽  
Simone Ribero ◽  
Marie Angele Cucci ◽  
Margherita Grattarola ◽  
Chiara Monge ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Targeted Therapies ◽  
Current Knowledge ◽  
Mapk Pathway ◽  
Acquired Resistance ◽  
Genetic Alterations ◽  
Advanced Melanoma ◽  
Braf Mutations ◽  
Downstream Signaling ◽  
Activating Mutations

Melanoma is a highly aggressive cancer with the poorest prognosis, representing the deadliest form of skin cancer. Activating mutations in BRAF are the most frequent genetic alterations, present in approximately 50% of all melanoma cases. The use of specific inhibitors towards mutant BRAF variants and MEK, a downstream signaling target of BRAF in the MAPK pathway, has significantly improved progression-free and overall survival in advanced melanoma patients carrying BRAF mutations. Nevertheless, despite these improvements, resistance still develops within the first year of therapy in around 50% of patients, which is a significant problem in managing BRAF-mutated advanced melanoma. Understanding these mechanisms is one of the mainstreams of the research on BRAFi/MEKi acquired resistance. Both genetic and epigenetic mechanisms have been described. Moreover, in recent years, oxidative stress has emerged as another major force involved in all the phases of melanoma development, from initiation to progression until the onsets of the metastatic phenotype and chemoresistance, and has thus become a target for therapy. In the present review, we discuss the current knowledge on oxidative stress and its signaling in melanoma, as well as the oxidative stress-related mechanisms in the acquired resistance to targeted therapies.

scholarly journals The structure and flexibility analysis of the Arabidopsis Synaptotagmin 1 reveal the basis of its regulation at membrane contact sites

2021 ◽  
Author(s):  
Juan Luis Benavente ◽  
Dritan Siliqi ◽  
Lourdes Infantes ◽  
Laura Lagartera ◽  
Alberto Mills ◽  
...  
Keyword(s):  
Cell Function ◽  
Lipid Extraction ◽  
Membrane Lipid ◽  
Lipid Binding ◽  
Lipid Transfer ◽  
C2 Domains ◽  
Membrane Contact Sites ◽  
Contact Sites ◽  
Cellular Environment ◽  
Synaptotagmin 1

Cell function requires the maintenance of membrane lipid homeostasis as changes in cellular environment unbalance this equilibrium. The non-vesicular lipid transfer at endoplasmic reticulum (ER) and plasma membrane (PM) contact sites (CS) is central to restore it. Extended synaptotagmins (E-Syts) are ER proteins that play a central role in this process as they act as molecular tethers with PM and as lipid transfer proteins between these organelles. E-Syts are constitutively anchored to the ER through an N-terminal hydrophobic segment and bind to the PM via C-terminal C2 domains. In plants, synaptotagmins (SYTs) are orthologous of E-Syts and regulate the ER-PM communication by the activity of their two C2 domains in response to abiotic stresses. We have combined macromolecular crystallography, small-angle X-ray scattering, structural bioinformatics and biochemical data to analyze the regulation of plant synaptotagmin 1 (SYT1). Our data show that the binding of SYT1 to the PM is regulated by the interaction of the first C2 domain through a Ca2+-dependent lipid binding site and by a site for phosphorylated forms of phosphatidylinositol in such a way that two different molecular signals are integrated in response to stress. In addition, our data show that SYT1 is highly flexible by virtue of up to three hinge points, including one that connects the two C2 domains. This feature provides conformational freedom to SYT1 to define a large and complementary interaction surface with the PM. This structural plasticity, in turn, may facilitate lipid extraction, protein loading and subsequent transfer between PM and ER.

scholarly journals Drugging an undruggable pocket on KRAS

2019 ◽  
Vol 116 (32) ◽  
pp. 15823-15829 ◽  
Author(s):  
Dirk Kessler ◽  
Michael Gmachl ◽  
Andreas Mantoulidis ◽  
Laetitia J. Martin ◽  
Andreas Zoephel ◽  
...  
Keyword(s):  
Molecular Switches ◽  
Small Gtpases ◽  
Ras Proteins ◽  
Structure Based Drug Design ◽  
Downstream Signaling ◽  
Activating Mutations ◽  
Ras Genes ◽  
Mutant Cells ◽  
Drug Discovery Target ◽  
Micromolar Range

The 3 human RAS genes, KRAS, NRAS, and HRAS, encode 4 different RAS proteins which belong to the protein family of small GTPases that function as binary molecular switches involved in cell signaling. Activating mutations in RAS are among the most common oncogenic drivers in human cancers, with KRAS being the most frequently mutated oncogene. Although KRAS is an excellent drug discovery target for many cancers, and despite decades of research, no therapeutic agent directly targeting RAS has been clinically approved. Using structure-based drug design, we have discovered BI-2852 (1), a KRAS inhibitor that binds with nanomolar affinity to a pocket, thus far perceived to be “undruggable,” between switch I and II on RAS; 1 is mechanistically distinct from covalent KRASG12C inhibitors because it binds to a different pocket present in both the active and inactive forms of KRAS. In doing so, it blocks all GEF, GAP, and effector interactions with KRAS, leading to inhibition of downstream signaling and an antiproliferative effect in the low micromolar range in KRAS mutant cells. These findings clearly demonstrate that this so-called switch I/II pocket is indeed druggable and provide the scientific community with a chemical probe that simultaneously targets the active and inactive forms of KRAS.

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