bims-pimaco 2023-09-10 papers

on PI3K and MAPK signalling in colorectal cancer

Issue of 2023–09–10
eleven papers selected by
Lucas B. Zeiger, CRUK Scotland Institute, Beatson Institute for Cancer Research

PI3K Signaling Through a Biochemical Systems Lens.
Lysines K117 and K147 play conserved roles in Ras activation from Drosophila to mammals.
Small molecular inhibitors for KRAS-mutant cancers.
PTEN activates chaperone-mediated autophagy to regulate metabolism.
Small-Molecule Inhibition of KRAS through Conformational Selection.
S6K1 Regulates GSK3 under Conditions of mTOR-Dependent Feedback Inhibition of Akt.
SHP2: A Pleiotropic Target at the Interface of Cancer and Its Microenvironment.
Lysosomes mediate the mitochondrial UPR via mTORC1-dependent ATF4 phosphorylation.
RAS signaling and immune cells: a sinister crosstalk in the tumor microenvironment.
Vitamin B6 is governed by the local compartmentalization of metabolic enzymes during growth.
Conditional fluorescent mouse translocation reporters for ERK1/2 and AKT signaling.

J Biol Chem. 2023 Sep 04. pii: S0021-9258(23)02252-4. [Epub ahead of print] 105224

PI3K Signaling Through a Biochemical Systems Lens.

Ralitsa R Madsen, Alex Toker.

DOI: https://doi.org/10.1016/j.jbc.2023.105224
G3 (Bethesda). 2023 Sep 04. pii: jkad201. [Epub ahead of print]

Lysines K117 and K147 play conserved roles in Ras activation from Drosophila to mammals.

Jiya Singh, Prashath Karunaraj, Max Luf, Cathie M Pfleger.

  Ras signaling plays an important role in growth, proliferation, and developmental patterning. Maintaining appropriate levels of Ras signaling is important to establish patterning in development and to prevent diseases such as cancer in mature organisms. The Ras protein is represented by Ras85D in Drosophila and by HRas, NRas, and KRas in mammals. In the past dozen years, multiple reports have characterized both inhibitory and activating ubiquitination events regulating Ras proteins. Inhibitory Ras ubiquitination mediated by Rabex-5 or Lztr1 is highly conserved between flies and mammals. Activating ubiquitination events at K117 and K147 have been reported in mammalian HRas, NRas, and KRas, but it is unclear if these activating roles of K117 and K147 are conserved in flies. Addressing a potential conserved role for these lysines in Drosophila Ras activation requires phenotypes strong enough to assess suppression. Therefore, we utilized oncogenic Ras, RasG12V, which biases Ras to the GTP-loaded active conformation. We created double mutants RasG12V,K117R, RasG12V,K147R, and triple mutant RasG12V,K117R,K147R, to prevent lysine-specific post-translational modification of K117, K147, or both respectively. We compared their phenotypes to RasG12V in the wing to reveal the roles of these lysines. Although RasG12V,K147R did not show compelling or quantifiable differences from RasG12V, RasG12V,K117R showed visible and quantifiable suppression compared to RasG12V, and triple mutant RasG12V,K117R,K147R showed dramatic suppression compared to RasG12V and increased suppression compared to RasG12V,K117R. These data are consistent with highly conserved roles for K117 and K147 in Ras activation from flies to mammals.

Keywords:  Drosophila; HRas; K117; K147; KRas; NRas; Ras; lysine; ubiquitin

DOI:  https://doi.org/10.1093/g3journal/jkad201
Front Immunol. 2023 ;14 1223433

Small molecular inhibitors for KRAS-mutant cancers.

Xuan Wu, Wenping Song, Cheng Cheng, Ziyang Liu, Xiang Li, Yu Cui, Yao Gao, Ding Li.

  Three rat sarcoma (RAS) gene isoforms, KRAS, NRAS, and HRAS, constitute the most mutated family of small GTPases in cancer. While the development of targeted immunotherapies has led to a substantial improvement in the overall survival of patients with non-KRAS-mutant cancer, patients with RAS-mutant cancers have an overall poorer prognosis owing to the high aggressiveness of RAS-mutant tumors. KRAS mutations are strongly implicated in lung, pancreatic, and colorectal cancers. However, RAS mutations exhibit diverse patterns of isoforms, substitutions, and positions in different types of cancers. Despite being considered "undruggable", recent advances in the use of allele-specific covalent inhibitors against the most common mutant form of RAS in non-small-cell lung cancer have led to the development of effective pharmacological interventions against RAS-mutant cancer. Sotorasib (AMG510) has been approved by the FDA as a second-line treatment for patients with KRAS-G12C mutant NSCLC who have received at least one prior systemic therapy. Other KRAS inhibitors are on the way to block KRAS-mutant cancers. In this review, we summarize the progress and promise of small-molecule inhibitors in clinical trials, including direct inhibitors of KRAS, pan-RAS inhibitors, inhibitors of RAS effector signaling, and immune checkpoint inhibitors or combinations with RAS inhibitors, to improve the prognosis of tumors with RAS mutations.

Keywords:  RAS inhibitor; RAS mutation; combination strategy; different isoform; immunotherapy

DOI:  https://doi.org/10.3389/fimmu.2023.1223433
Autophagy. 2023 Sep 08. 1-2

PTEN activates chaperone-mediated autophagy to regulate metabolism.

S Joseph Endicott, Richard A Miller.

  PTEN is a negative modulator of the INS-PI3K-AKT pathway and is an essential regulator of metabolism and cell growth. PTEN is one of the most commonly mutated tumor suppressors in cancer. However, PTEN overexpression extends the lifespan of both sexes of mice. We recently showed that PTEN is necessary and sufficient to activate chaperone-mediated autophagy (CMA) in the mouse liver and cultured cells. Selective protein degradation via CMA is required to suppress glycolysis and fatty acid synthesis when PTEN is overexpressed. Thus, activation of CMA downstream of PTEN might modulate health and metabolism through selective degradation of key metabolic enzymes.

Keywords:  Aging; PTEN; autophagy; chaperone-mediated autophagy; metabolism

DOI:  https://doi.org/10.1080/15548627.2023.2255966
ACS Omega. 2023 Aug 29. 8(34): 31419-31426

Small-Molecule Inhibition of KRAS through Conformational Selection.

Cynthia V Pagba, Amit K Gupta, Alemayehu A Gorfe.

Mutations in KRAS account for about 20% of human cancers. Despite the major progress in recent years toward the development of KRAS inhibitors, including the discovery of covalent inhibitors of the G12C KRAS variant for the treatment of non-small-cell lung cancer, much work remains to be done to discover broad-acting inhibitors to treat many other KRAS-driven cancers. In a previous report, we showed that a 308.4 Da small-molecule ligand [(2R)-2-(N'-(1H-indole-3-carbonyl)hydrazino)-2-phenyl-acetamide] binds to KRAS with low micro-molar affinity [Chem. Biol. Drug Des.2019; 94(2):1441-1456]. Binding of this ligand, which we call ACA22, to the p1 pocket of KRAS and its interactions with residues at beta-strand 1 and the switch loops have been supported by data from nuclear magnetic resonance spectroscopy and microscale thermophoresis experiments. However, the inhibitory potential of the compound was not demonstrated. Here, we show that ACA22 inhibits KRAS-mediated signal transduction in cells expressing wild type (WT) and G12D mutant KRAS and reduces levels of guanosine triphosphate-loaded WT KRAS more effectively than G12D KRAS. We ruled out the direct effect on nucleotide exchange or effector binding as possible mechanisms of inhibition using a variety of biophysical assays. Combining these observations with binding data that show comparable affinities of the compound for the active and inactive forms of the mutant but not the WT, we propose conformational selection as a possible mechanism of action of ACA22.

DOI: https://doi.org/10.1021/acsomega.3c04013
Mol Cell. 2023 Sep 07. pii: S1097-2765(23)00616-0. [Epub ahead of print]83(17): 3217

S6K1 Regulates GSK3 under Conditions of mTOR-Dependent Feedback Inhibition of Akt.

Hui H Zhang, Alex I Lipovsky, Christian C Dibble, Mustafa Sahin, Brendan D Manning.

DOI: https://doi.org/10.1016/j.molcel.2023.08.003
Cancer Discov. 2023 Sep 08. OF1-OF17

SHP2: A Pleiotropic Target at the Interface of Cancer and Its Microenvironment.

Nicole M Sodir, Gaurav Pathria, Joanne I Adamkewicz, Elizabeth H Kelley, Jawahar Sudhamsu, Mark Merchant, Roberto Chiarle, Danilo Maddalo.

The protein phosphatase SHP2/PTPN11 has been reported to be a key modulator of proliferative pathways in a wide range of malignancies. Intriguingly, SHP2 has also been described as a critical regulator of the tumor microenvironment. Based on this evidence SHP2 is considered a multifaceted target in cancer, spurring the notion that the development of direct inhibitors of SHP2 would provide the twofold benefit of tumor intrinsic and extrinsic inhibition. In this review, we will discuss the role of SHP2 in cancer and the tumor microenvironment, and the clinical strategies in which SHP2 inhibitors are leveraged as combination agents to improve therapeutic response.
SIGNIFICANCE: The SHP2 phosphatase functions as a pleiotropic factor, and its inhibition not only hinders tumor growth but also reshapes the tumor microenvironment. Although their single-agent activity may be limited, SHP2 inhibitors hold the potential of being key combination agents to enhance the depth and the durability of tumor response to therapy.

DOI: https://doi.org/10.1158/2159-8290.CD-23-0383
Cell Discov. 2023 Sep 07. 9(1): 92

Lysosomes mediate the mitochondrial UPR via mTORC1-dependent ATF4 phosphorylation.

Terytty Yang Li, Qi Wang, Arwen W Gao, Xiaoxu Li, Yu Sun, Adrienne Mottis, Minho Shong, Johan Auwerx.

Lysosomes are central platforms for not only the degradation of macromolecules but also the integration of multiple signaling pathways. However, whether and how lysosomes mediate the mitochondrial stress response (MSR) remain largely unknown. Here, we demonstrate that lysosomal acidification via the vacuolar H+-ATPase (v-ATPase) is essential for the transcriptional activation of the mitochondrial unfolded protein response (UPRmt). Mitochondrial stress stimulates v-ATPase-mediated lysosomal activation of the mechanistic target of rapamycin complex 1 (mTORC1), which then directly phosphorylates the MSR transcription factor, activating transcription factor 4 (ATF4). Disruption of mTORC1-dependent ATF4 phosphorylation blocks the UPRmt, but not other similar stress responses, such as the UPRER. Finally, ATF4 phosphorylation downstream of the v-ATPase/mTORC1 signaling is indispensable for sustaining mitochondrial redox homeostasis and protecting cells from ROS-associated cell death upon mitochondrial stress. Thus, v-ATPase/mTORC1-mediated ATF4 phosphorylation via lysosomes links mitochondrial stress to UPRmt activation and mitochondrial function resilience.

DOI: https://doi.org/10.1038/s41421-023-00589-1
J Transl Med. 2023 Sep 05. 21(1): 595

RAS signaling and immune cells: a sinister crosstalk in the tumor microenvironment.

Yongting Liu, Bin Xie, Qiong Chen.

  The rat sarcoma virus (RAS) gene is the most commonly mutated oncogene in cancer, with about 19% of cancer patients carrying RAS mutations. Studies on the interaction between RAS mutation and tumor immune microenvironment (TIM) have been flourishing in recent years. More and more evidence has proved that RAS signals regulate immune cells' recruitment, activation, and differentiation while assisting tumor cells to evade immune surveillance. This review concluded the direct and indirect treatment strategies for RAS mutations. In addition, we updated the underlying mechanisms by which RAS signaling modulated immune infiltration and immune escape. Finally, we discussed advances in RAS-targeted immunotherapies, including cancer vaccines and adoptive cell therapies, with a particular focus on combination strategies with personalized therapy and great potential to achieve lasting clinical benefits.

Keywords:  Adoptive cell therapy; Cancer vaccine; Immune cell infiltration; Immune escape; RAS mutation

DOI:  https://doi.org/10.1186/s12967-023-04486-9
Sci Adv. 2023 Sep 08. 9(36): eadi2232

Vitamin B6 is governed by the local compartmentalization of metabolic enzymes during growth.

Carolina N Franco, Laurence J Seabrook, Steven T Nguyen, Ying Yang, Melissa Campos, Qi Fan, Andrew C Cicchetto, Mei Kong, Heather R Christofk, Lauren V Albrecht.

Vitamin B6 is a vital micronutrient across cell types and tissues, and dysregulated B6 levels contribute to human disease. Despite its importance, how B6 vitamer levels are regulated is not well understood. Here, we provide evidence that B6 dynamics are rapidly tuned by precise compartmentation of pyridoxal kinase (PDXK), the rate-limiting B6 enzyme. We show that canonical Wnt rapidly led to the accumulation of inactive B6 by shunting cytosolic PDXK into lysosomes. PDXK was modified with methyl-arginine Degron (MrDegron), a protein tag for lysosomes, which enabled delivery via microautophagy. Hyperactive lysosomes resulted in the continuous degradation of PDXK and B6 deficiency that promoted proliferation in Wnt-driven colorectal cancer (CRC) cells. Pharmacological or genetic disruption of the coordinated MrDegron proteolytic pathway was sufficient to reduce CRC survival in cells and organoid models. In sum, this work contributes to the repertoire of micronutrient-regulated processes that enable cancer cell growth and provides insight into the functional impact of B6 deficiencies for survival.

DOI: https://doi.org/10.1126/sciadv.adi2232
Dev Biol. 2023 Sep 01. pii: S0012-1606(23)00146-X. [Epub ahead of print]503 113-119

Conditional fluorescent mouse translocation reporters for ERK1/2 and AKT signaling.

Colin J Dinsmore, Philippe Soriano.

  Understanding how cells activate intracellular signaling pathways in response to external signals, such as growth factors, is a longstanding goal of cell and developmental biology. Recently, live-cell signaling reporters have greatly expanded our understanding of signaling dynamics in response to wide-ranging stimuli and chemical or genetic perturbation, both ex vivo (cell lines) and in vivo (whole embryos or animals). Among the many varieties of reporter systems, translocation reporters that change sub-cellular localization in response to pathway activation have received considerable attention for their ease of use compared to FRET systems and favorable response times compared to transcriptional reporters. We reasoned that mouse reporter lines expressed in a conditional fashion would be a useful addition to the arsenal of mouse genetic tools, as such lines remain undeveloped despite widespread use of these sensors. We therefore created and validated two novel mouse reporter lines at the ROSA26 locus. One expresses an ERK1/2 pathway reporter and a nuclear marker from a single transcript, while the second additionally expresses an AKT reporter in order to simultaneously interrogate both pathways.

Keywords:  AKT; ERK; FOXO; Genetics; KTR; Mouse; Reporter; Signaling

DOI:  https://doi.org/10.1016/j.ydbio.2023.08.007