bims-pimaco 2023-06-11 papers

on PI3K and MAPK signalling in colorectal cancer

Issue of 2023–06–11
nine papers selected by
Lucas B. Zeiger, CRUK Scotland Institute, Beatson Institute for Cancer Research

A Pan-KRAS Inhibitor Impedes Common KRAS Oncoproteins and Tumor Growth.
Redundant electrostatic interactions between GATOR1 and the Rag GTPase heterodimer drives efficient amino acid sensing in human cells.
mTORC1 inhibition impairs activation of the unfolded protein response and induces cell death during ER stress in cardiomyocytes.
An evolutionary mechanism to assimilate new nutrient sensors into the mTORC1 pathway.
PTEN regulated PI3K-p110 and AKT isoform plasticity controls metastatic prostate cancer progression.
An allosteric pan-TEAD inhibitor blocks oncogenic YAP/TAZ signaling and overcomes KRAS G12C inhibitor resistance.
The GCN2/eIF2αK stress kinase regulates PP1 to ensure mitotic fidelity.
SHP2 Inhibition Sensitizes Diverse Oncogene-Addicted Solid Tumors to Re-treatment with Targeted Therapy.
Intestinal stem cells and their niches in homeostasis and disease.

Cancer Discov. 2023 Jun 09. OF1

A Pan-KRAS Inhibitor Impedes Common KRAS Oncoproteins and Tumor Growth.

A pan-KRAS inhibitor is selective for the inactive state of multiple KRAS mutants, sparing other RAS isoforms.

DOI: https://doi.org/10.1158/2159-8290.CD-RW2023-090
J Biol Chem. 2023 Jun 01. pii: S0021-9258(23)01908-7. [Epub ahead of print] 104880

Redundant electrostatic interactions between GATOR1 and the Rag GTPase heterodimer drives efficient amino acid sensing in human cells.

Dylan D Doxsey, Steven D Tettoni, Shawn B Egri, Kuang Shen.

  Cells need to coordinate nutrient availability with their growth and proliferation. In eukaryotic cells, this coordination is mediated by the mechanistic target of rapamycin complex 1 (mTORC1) pathway. mTORC1 activation is regulated by two GTPase units, the Rag GTPase heterodimer and the Rheb GTPase. The RagA-RagC heterodimer controls the subcellular localization of mTORC1, and its nucleotide loading states are strictly controlled by upstream regulators including amino acid sensors. A critical negative regulator of the Rag GTPase heterodimer is GATOR1. In the absence of amino acids, GATOR1 stimulates GTP hydrolysis by the RagA subunit to turn off mTORC1 signaling. Despite the enzymatic specificity of GATOR1 to RagA, a recent cryo-EM structural model of the human GATOR1-Rag-Ragulator complex reveals an unexpected interface between Depdc5, a subunit of GATOR1, and RagC. Currently, there is no functional characterization of this interface, nor do we know its biological relevance. Here, combining structure-function analysis, enzymatic kinetic measurements, and cell-based signaling assays, we identified a critical electrostatic interaction between Depdc5 and RagC. This interaction is mediated by the positively charged Arg-1407 residue on Depdc5, and a patch of negatively charged residues on the lateral side of RagC. Abrogating this interaction impairs the GAP activity of GATOR1 and cellular response to amino acid withdrawal. Our results reveal how GATOR1 coordinates the nucleotide loading states of the Rag GTPase heterodimer, and thus precisely controls cellular behavior in the absence of amino acids.

Keywords:  GATOR1; GTPase Activating Protein; Metabolism; Rag GTPase; mTOR complex 1 (mTORC1)

DOI:  https://doi.org/10.1016/j.jbc.2023.104880
Am J Physiol Heart Circ Physiol. 2023 Jun 09.

mTORC1 inhibition impairs activation of the unfolded protein response and induces cell death during ER stress in cardiomyocytes.

Christoph Hofmann, Zoe Löwenthal, Marjan Aghajani, Randal J Kaufman, Hugo A Katus, Norbert Frey, Christopher C Glembotski, Mirko Völkers, Shirin Doroudgar.

  The mechanistic target of rapamycin complex 1 (mTORC1) is a central regulator of protein synthesis that senses and responds to a variety of stimuli to coordinate cellular metabolism with environmental conditions. To ensure that protein synthesis is inhibited during unfavorable conditions, translation is directly coupled to the sensing of cellular protein homeostasis. Thus, translation is attenuated during endoplasmic reticulum (ER) stress by direct inhibition of the mTORC1 pathway. However, residual mTORC1 activity is maintained during prolonged ER stress which is thought to be involved in translational reprogramming and adaption to ER stress. By analyzing the dynamics of mTORC1 regulation during ER stress, we unexpectedly found that mTORC1 is transiently activated in cardiomyocytes within minutes at the onset of ER stress before being inhibited during chronic ER stress. This dynamic regulation of mTORC1 appears to be mediated, at least in part, by ATF6, as its activation was sufficient to induce the biphasic control of mTORC1. We further showed that protein synthesis remains dependent on mTORC1 throughout the ER stress response and that mTORC1 activity is essential for posttranscriptional induction of several unfolded protein response elements. Pharmacological inhibition of mTORC1 increased cell death during ER stress, indicating that the mTORC1 pathway serves adaptive functions during ER stress in cardiomyocytes potentially by controlling the expression of the protective unfolded protein response.

Keywords:  ATF6; ER stress; cardiomyocytes; cell death; mTORC1

DOI:  https://doi.org/10.1152/ajpheart.00682.2022
bioRxiv. 2023 May 26. pii: 2023.05.25.541239. [Epub ahead of print]

An evolutionary mechanism to assimilate new nutrient sensors into the mTORC1 pathway.

Grace Y Liu, Patrick Jouandin, Raymond E Bahng, Norbert Perrimon, David M Sabatini.

Animals must sense and respond to nutrient availability in their local niche. This task is coordinated in part by the mTOR complex 1 (mTORC1) pathway, which regulates growth and metabolism in response to nutrients 1-5 . In mammals, mTORC1 senses specific amino acids through specialized sensors that act through the upstream GATOR1/2 signaling hub 6-8 . To reconcile the conserved architecture of the mTORC1 pathway with the diversity of environments that animals can occupy, we hypothesized that the pathway might maintain plasticity by evolving distinct nutrient sensors in different metazoan phyla 1,9,10 . Whether such customization occurs- and how the mTORC1 pathway might capture new nutrient inputs-is not known. Here, we identify the Drosophila melanogaster protein Unmet expectations (Unmet, formerly CG11596) as a species-restricted nutrient sensor and trace its incorporation into the mTORC1 pathway. Upon methionine starvation, Unmet binds to the fly GATOR2 complex to inhibit dTORC1. S -adenosylmethionine (SAM), a proxy for methionine availability, directly relieves this inhibition. Unmet expression is elevated in the ovary, a methionine-sensitive niche 11 , and flies lacking Unmet fail to maintain the integrity of the female germline under methionine restriction. By monitoring the evolutionary history of the Unmet-GATOR2 interaction, we show that the GATOR2 complex evolved rapidly in Dipterans to recruit and repurpose an independent methyltransferase as a SAM sensor. Thus, the modular architecture of the mTORC1 pathway allows it to co-opt preexisting enzymes and expand its nutrient sensing capabilities, revealing a mechanism for conferring evolvability on an otherwise highly conserved system.

DOI: https://doi.org/10.1101/2023.05.25.541239
Res Sq. 2023 May 16. pii: rs.3.rs-2924750. [Epub ahead of print]

PTEN regulated PI3K-p110 and AKT isoform plasticity controls metastatic prostate cancer progression.

Karina Miller, Seamus Degan, Yanqing Wang, Joseph Cohen, Sheng-Yu Ku, David Goodrich, Irwin Gelman.

PTEN loss, one of the most frequent mutations in prostate cancer (PC), is presumed to drive disease progression through AKT activation. However, two transgenic PC models with Akt activation plus Rb loss exhibited different metastasis development: Pten/Rb PE:-/- mice produced systemic metastatic adenocarcinomas with high AKT2 activation, whereas Rb PE:-/- mice deficient for the Src-scaffolding protein, Akap12, induced high-grade prostatic intraepithelial neoplasias and indolent lymph node disseminations, correlating with upregulated phosphotyrosyl PI3K-p85α. Using PC cells isogenic for PTEN, we show that PTEN-deficiency correlated with dependence on both p110β and AKT2 for in vitro and in vivo parameters of metastatic growth or motility, and with downregulation of SMAD4, a known PC metastasis suppressor. In contrast, PTEN expression, which dampened these oncogenic behaviors, correlated with greater dependence on p110α plus AKT1. Our data suggest that metastatic PC aggressiveness is controlled by specific PI3K/AKT isoform combinations influenced by divergent Src activation or PTEN-loss pathways.

DOI: https://doi.org/10.21203/rs.3.rs-2924750/v1
Nat Cancer. 2023 Jun 05.

An allosteric pan-TEAD inhibitor blocks oncogenic YAP/TAZ signaling and overcomes KRAS G12C inhibitor resistance.

Thijs J Hagenbeek, Jason R Zbieg, Marc Hafner, Rana Mroue, Jennifer A Lacap, Nicole M Sodir, Cameron L Noland, Shervin Afghani, Ayush Kishore, Kamakoti P Bhat, Xiaosai Yao, Stephen Schmidt, Saundra Clausen, Micah Steffek, Wendy Lee, Paul Beroza, Scott Martin, Eva Lin, Rina Fong, Paola Di Lello, Marta H Kubala, Michelle N-Y Yang, Jeffrey T Lau, Emily Chan, Alfonso Arrazate, Le An, Elizabeth Levy, Maria N Lorenzo, Ho-June Lee, Trang H Pham, Zora Modrusan, Richard Zang, Yi-Chen Chen, Michal Kabza, Musaddeque Ahmed, Jason Li, Matthew T Chang, Danilo Maddalo, Marie Evangelista, Xin Ye, James J Crawford, Anwesha Dey.

The Hippo pathway is a key growth control pathway that is conserved across species. The downstream effectors of the Hippo pathway, YAP (Yes-associated protein) and TAZ (transcriptional coactivator with PDZ-binding motif), are frequently activated in cancers to drive proliferation and survival. Based on the premise that sustained interactions between YAP/TAZ and TEADs (transcriptional enhanced associate domain) are central to their transcriptional activities, we discovered a potent small-molecule inhibitor (SMI), GNE-7883, that allosterically blocks the interactions between YAP/TAZ and all human TEAD paralogs through binding to the TEAD lipid pocket. GNE-7883 effectively reduces chromatin accessibility specifically at TEAD motifs, suppresses cell proliferation in a variety of cell line models and achieves strong antitumor efficacy in vivo. Furthermore, we uncovered that GNE-7883 effectively overcomes both intrinsic and acquired resistance to KRAS (Kirsten rat sarcoma viral oncogene homolog) G12C inhibitors in diverse preclinical models through the inhibition of YAP/TAZ activation. Taken together, this work demonstrates the activities of TEAD SMIs in YAP/TAZ-dependent cancers and highlights their potential broad applications in precision oncology and therapy resistance.

DOI: https://doi.org/10.1038/s43018-023-00577-0
EMBO Rep. 2023 Jun 09. e56100

The GCN2/eIF2αK stress kinase regulates PP1 to ensure mitotic fidelity.

Vilte Stonyte, Maria Mastrangelopoulou, Romy Timmer, Lilian Lindbergsengen, Marina Vietri, Coen Campsteijn, Beáta Grallert.

  GCN2/eIF2αK4 is exclusively seen as an eIF2α kinase, which regulates reprogramming of protein translation in response to stress. Here, we show that GCN2 has an unexpected role in unstressed cells as a regulator of mitosis. This function is not through its canonical role in translation reprogramming, but through the regulation of two previously unidentified substrates, PP1α and γ. In the absence of GCN2 function, timing and levels of phosphorylation of key mitotic players are altered, leading to aberrant chromosome alignment, missegregating chromosomes, elevated number of tripolar spindles, and a delay in progression through mitosis. Pharmacological inhibition of GCN2 results in similar effects and is synergistic with Aurora A inhibition in causing more severe mitotic errors and cell death. We suggest that GCN2-dependent phosphorylation of PP1α and γ restrains their activity and this is important to ensure the timely regulation of phosphorylation of several PP1 substrates during early mitosis. These findings highlight a druggable PP1 inhibitor and open new avenues of research on the therapeutic potential of GCN2 inhibitors.

Keywords:  Aurora A; GCN2; PP1; chromosome alignment; mitosis

DOI:  https://doi.org/10.15252/embr.202256100
Cancer Discov. 2023 Jun 03. OF1-OF13

SHP2 Inhibition Sensitizes Diverse Oncogene-Addicted Solid Tumors to Re-treatment with Targeted Therapy.

Alexander Drilon, Manish R Sharma, Melissa L Johnson, Timothy A Yap, Shirish Gadgeel, Dale Nepert, Gang Feng, Micaela B Reddy, Allison S Harney, Mohamed Elsayed, Adam W Cook, Christina E Wong, Ronald J Hinklin, Yutong Jiang, Eric N Brown, Nickolas A Neitzel, Ellen R Laird, Wen-I Wu, Anurag Singh, Ping Wei, Keith A Ching, John J Gaudino, Patrice A Lee, Dylan P Hartley, S Michael Rothenberg.

Rationally targeted therapies have transformed cancer treatment, but many patients develop resistance through bypass signaling pathway activation. PF-07284892 (ARRY-558) is an allosteric SHP2 inhibitor designed to overcome bypass-signaling-mediated resistance when combined with inhibitors of various oncogenic drivers. Activity in this setting was confirmed in diverse tumor models. Patients with ALK fusion-positive lung cancer, BRAFV600E-mutant colorectal cancer, KRASG12D-mutant ovarian cancer, and ROS1 fusion-positive pancreatic cancer who previously developed targeted therapy resistance were treated with PF-07284892 on the first dose level of a first-in-human clinical trial. After progression on PF-07284892 monotherapy, a novel study design allowed the addition of oncogene-directed targeted therapy that had previously failed. Combination therapy led to rapid tumor and circulating tumor DNA (ctDNA) responses and extended the duration of overall clinical benefit.
SIGNIFICANCE: PF-07284892-targeted therapy combinations overcame bypass-signaling-mediated resistance in a clinical setting in which neither component was active on its own. This provides proof of concept of the utility of SHP2 inhibitors in overcoming resistance to diverse targeted therapies and provides a paradigm for accelerated testing of novel drug combinations early in clinical development. See related commentary by Hernando-Calvo and Garralda.

DOI: https://doi.org/10.1158/2159-8290.CD-23-0361
Cells Dev. 2023 Jun 02. pii: S2667-2901(23)00038-4. [Epub ahead of print] 203862

Intestinal stem cells and their niches in homeostasis and disease.

Jun Zhou, Michael Boutros.

  Tissues such as the intestine harbor stem cells that have remarkable functional plasticity in response to a dynamic environment. To adapt to the environment, stem cells constantly receive information from their surrounding microenvironment (also called the 'niche') that instructs them how to adapt to changes. The Drosophila midgut shows morphological and functional similarities to the mammalian small intestine and has been a useful model system to study signaling events in stem cells and tissue homeostasis. In this review, we summarize the current understanding of the Drosophila midgut regarding how stem cells communicate with microenvironmental niches including enteroblasts, enterocytes, enteroendocrine cells and visceral muscles to coordinate tissue regeneration and homeostasis. In addition, distant cells such as hemocytes or tracheal cells have been shown to interact with stem cells and influence the development of intestinal diseases. We discuss the contribution of stem cell niches in driving or counteracting disease progression, and review conceptual advances derived from the Drosophila intestine as a model for stem cell biology.

Keywords:  Drosophila; Intestine; Niche; Signal transduction; Stem cells

DOI:  https://doi.org/10.1016/j.cdev.2023.203862