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Aspirin reduces the incidence of colorectal adenoma and colorectal cancer among high-risk persons. Observational studies suggest that aspirin may also improve disease-free survival after diagnosis, particularly among patients with tumors harboring somatic mutations. However, data from randomized trials are lacking. We conducted a double-blind, randomized, placebo-controlled trial involving patients with stage I, II, or III rectal cancer or stage II or III colon cancer with somatic alterations in PI3K pathway genes. The patients were assigned in a 1:1 ratio to receive 160 mg of aspirin or matched placebo once daily for 3 years. Patients with prespecified hotspot mutations in exon 9 or 20 (group A alterations) and those with other moderate- or high-impact somatic variants in , , or (group B alterations) were eligible for randomization. The primary end point was colorectal cancer recurrence, assessed in a time-to-event analysis, in patients with group A alterations. Secondary end points included colorectal cancer recurrence in patients with group B alterations, disease-free survival, and safety. Alterations in PI3K pathway genes were detected in 1103 of 2980 patients (37.0%) with complete genomic data. Of 515 patients with group A alterations and 588 patients with group B alterations, 314 and 312, respectively, were assigned to receive aspirin or placebo. The estimated 3-year cumulative incidence of recurrence was 7.7% with aspirin and 14.1% with placebo (hazard ratio, 0.49; 95% confidence interval [CI], 0.24 to 0.98; P = 0.04) among patients with group A alterations and 7.7% and 16.8%, respectively (hazard ratio, 0.42; 95% CI, 0.21 to 0.83), among those with group B alterations. The estimated 3-year disease-free survival was 88.5% with aspirin and 81.4% with placebo (hazard ratio, 0.61; 95% CI, 0.34 to 1.08) among patients with group A alterations and 89.1% and 78.7%, respectively (hazard ratio, 0.51; 95% CI, 0.29 to 0.88), among those with group B alterations. Severe adverse events occurred in 16.8% of aspirin recipients and 11.6% of placebo recipients. Aspirin led to a significantly lower incidence of colorectal cancer recurrence than placebo among patients with hotspot mutations in exon 9 or 20 and appeared to have a similar benefit among those with other somatic alterations in PI3K pathway genes. (Funded by the Swedish Research Council and others; ALASCCA ClinicalTrials.gov number, NCT02647099; EudraCT number, 2015-004240-19.).

Alpelisib selectively inhibits the p110α catalytic subunit of PI3Kα and is approved for treatment of breast cancers harboring canonical PIK3CA mutations. In head and neck squamous cell carcinoma (HNSCC), 63% of PIK3CA mutations occur at canonical hotspots. The oncogenic role of the remaining 37% of PIK3CA noncanonical mutations is incompletely understood. We report a patient with HNSCC with a noncanonical PIK3CA mutation (Q75E) who exhibited a durable (12 months) response to alpelisib in a phase II clinical trial. Characterization of all 32 noncanonical PIK3CA mutations found in HNSCC using several functional and phenotypic assays revealed that the majority (69%) were activating, including Q75E. The oncogenic impact of these mutations was validated in 4 cellular models, demonstrating that their activity was lineage independent. Further, alpelisib exhibited antitumor effects in a xenograft derived from a patient with HNSCC containing an activating noncanonical PIK3CA mutation. Structural analyses revealed plausible mechanisms for the functional phenotypes of the majority of the noncanonical PIK3CA mutations. Collectively, these findings highlight the importance of characterizing the function of noncanonical PIK3CA mutations and suggest that patients with HNSCC whose tumors harbor activating noncanonical PIK3CA mutations may benefit from treatment with PI3Kα inhibitors.

Oscillations of actin, FBP17 and N-WASP are coupled to phase-shifted phosphoinositide (PI) turnover that is regulated by the lipid phosphatases SHIP1, synaptojanin 2 and PI 3-kinases. PI(4,5)P 2 turnover regulates wave amplitude and PI(3,4)P 2 acts as a pacemaker. Rhythmicity is prevalent in the cortical dynamics of diverse single and multicellular systems. Current models of cortical oscillations focus primarily on cytoskeleton-based feedbacks, but information on signals upstream of the actin cytoskeleton is limited. In addition, inhibitory mechanisms—especially local inhibitory mechanisms, which ensure proper spatial and kinetic controls of activation—are not well understood. Here, we identified two phosphoinositide phosphatases, synaptojanin 2 and SHIP1, that function in periodic traveling waves of rat basophilic leukemia (RBL) mast cells. The local, phase-shifted activation of lipid phosphatases generates sequential waves of phosphoinositides. By acutely perturbing phosphoinositide composition using optogenetic methods, we showed that pulses of PtdIns(4,5)P 2 regulate the amplitude of cyclic membrane waves while PtdIns(3,4)P 2 sets the frequency. Collectively, these data suggest that the spatiotemporal dynamics of lipid metabolism have a key role in governing cortical oscillations and reveal how phosphatidylinositol 3-kinases (PI3K) activity could be frequency-encoded by a phosphatase-dependent inhibitory reaction.

‘Coincidence-detecting’ phosphoinositide sensors are used to study changes in the phosphoinositide lipid species found in membranes during the development and maturation of endocytic clathrin-coated vesicles. Changing composition of cell membranes The traffic within cells is busy. At any given time, many vesicles bud off the membrane of one organelle and travel to fuse with another membrane elsewhere. Which characteristics identify the donor and acceptor membranes is an intriguing question. The answer seems to be the lipid and protein composition of the membranes, specifically the presence and relative abundance of the seven species of phosphoinositide lipids, as well as GTP-bound GTPases. Tom Kirchhausen and colleagues describe a new generation of phosphoinositide sensors. They used these sensors to study the phosphoinositide composition of clathrin-associated membranes, which are involved in the process of endocytosis. The findings provide information on how the composition of the membrane changes from the time it is coated with clathrin to form pits, to when the pits close into vesicles, and, once the vesicles bud off, to when they lose their clathrin coating and fuse with endosomes. Vesicular carriers transport proteins and lipids from one organelle to another, recognizing specific identifiers for the donor and acceptor membranes. Two important identifiers are phosphoinositides and GTP-bound GTPases, which provide well-defined but mutable labels. Phosphatidylinositol and its phosphorylated derivatives are present on the cytosolic faces of most cellular membranes 1 , 2 . Reversible phosphorylation of its headgroup produces seven distinct phosphoinositides. In endocytic traffic, phosphatidylinositol-4,5-biphosphate marks the plasma membrane, and phosphatidylinositol-3-phosphate and phosphatidylinositol-4-phosphate mark distinct endosomal compartments 2 , 3 . It is unknown what sequence of changes in lipid content confers on the vesicles their distinct identity at each intermediate step. Here we describe ‘coincidence-detecting’ sensors that selectively report the phosphoinositide composition of clathrin-associated structures, and the use of these sensors to follow the dynamics of phosphoinositide conversion during endocytosis. The membrane of an assembling coated pit, in equilibrium with the surrounding plasma membrane, contains phosphatidylinositol-4,5-biphosphate and a smaller amount of phosphatidylinositol-4-phosphate. Closure of the vesicle interrupts free exchange with the plasma membrane. A substantial burst of phosphatidylinositol-4-phosphate immediately after budding coincides with a burst of phosphatidylinositol-3-phosphate, distinct from any later encounter with the phosphatidylinositol-3-phosphate pool in early endosomes; phosphatidylinositol-3,4-biphosphate and the GTPase Rab5 then appear and remain as the uncoating vesicles mature into Rab5-positive endocytic intermediates. Our observations show that a cascade of molecular conversions, made possible by the separation of a vesicle from its parent membrane, can label membrane-traffic intermediates and determine their destinations.

The protein kinase Akt controls myriad signaling processes in cells, ranging from growth and proliferation to differentiation and metabolism. Akt is activated by a combination of binding to the lipid second messenger PI(3,4,5)P₃ and its subsequent phosphorylation by phosphoinositide-dependent kinase 1 and mechanistic target of rapamycin complex 2. The relative contributions of these mechanisms to Akt activity and signaling have hitherto not been understood. Here, we show that phosphorylation and activation by membrane binding are mutually interdependent. Moreover, the converse is also true: Akt is more rapidly dephosphorylated in the absence of PIP₃, an autoinhibitory process driven by the interaction of its PH and kinase domains. We present biophysical evidence for the conformational changes in Akt that accompany its activation onmembranes, show that Akt is robustly autoinhibited in the absence of PIP₃ irrespective of its phosphorylation, and map the autoinhibitory PH–kinase interface. Finally, we present a model for the activation and inactivation of Akt by an ordered series of membrane binding, phosphorylation, dissociation, and dephosphorylation events.

Phosphoinositides are a family of membrane lipids essential for many biological and pathological processes. Due to the existence of multiple phosphoinositide regioisomers and their low intracellular concentrations, profiling these lipids and linking a specific acyl variant to a change in biological state have been difficult. To enable the comprehensive analysis of phosphoinositide phosphorylation status and acyl chain identity, we develop PRMC-MS (Phosphoinositide Regioisomer Measurement by Chiral column chromatography and Mass Spectrometry). Using this method, we reveal a severe skewing in acyl chains in phosphoinositides in Pten -deficient prostate cancer tissues, extracellular mobilization of phosphoinositides upon expression of oncogenic PIK3CA, and a unique profile for exosomal phosphoinositides. Thus, our approach allows characterizing the dynamics of phosphoinositide acyl variants in intracellular and extracellular milieus. Different phosphoinositide isomers are involved in a variety of physiological and pathological processes. Here, the authors combine chiral column chromatography and mass spectrometry to measure phosphoinositide regioisomers, revealing their dynamic changes in intra- and extracellular cancer cell milieus.

Phosphoinositides play a crucial role in regulating many cellular functions, such as actin dynamics, signaling, intracellular trafficking, membrane dynamics, and cell–matrix adhesion. Central to this process is phosphatidylinositol bisphosphate (PIP2). The levels of PIP2 in the membrane are rapidly altered by the activity of phosphoinositide-directed kinases and phosphatases, and it binds to dozens of different intracellular proteins. Despite the vast literature dedicated to understanding the regulation of PIP2 in cells over past 30 years, much remains to be learned about its cellular functions. In this review, we focus on past and recent exciting results on different molecular mechanisms that regulate cellular functions by binding of specific proteins to PIP2 or by stabilizing phosphoinositide pools in different cellular compartments. Moreover, this review summarizes recent findings that implicate dysregulation of PIP2 in many diseases

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.

In PIK3CA -mutated, HR-positive, HER2-negative locally advanced or metastatic breast cancer, inavolisib plus palbociclib–fulvestrant led to significantly longer progression-free survival than placebo plus palbociclib–fulvestrant.

Autophagy is a conserved intracellular degradation pathway essential for protein homeostasis, survival and development. Defects in autophagic pathways have been connected to a variety of human diseases, including cancer and neurodegeneration. In the process of macroautophagy, cytoplasmic cargo is enclosed in a double-membrane structure and fused to the lysosome to allow for digestion and recycling of material. Autophagosome formation is primed by the ULK complex, which enables the downstream production of PI(3)P, a key lipid signalling molecule, on the phagophore membrane. The PI(3)P is generated by the PI3 kinase (PI3K) complex, consisting of the core components VPS34, VPS15 and Beclin 1. Beclin 1 is a central player in autophagy and constitutes a molecular platform for the regulation of autophagosome formation and maturation. Post-translational modifications of Beclin 1 affect its stability, interactions and ability to regulate PI3K activity, providing the cell with a plethora of strategies to fine-tune the levels of autophagy. Being such an important regulator, Beclin 1 is a potential target for therapeutic intervention and interfering with the post-translational regulation of Beclin 1 could be one way of manipulating the levels of autophagy. In this review, we provide an overview of the known post-translational modifications of Beclin 1 that govern its role in autophagy and how these modifications are maintained by input from several upstream signalling pathways.