bims-pimaco 2022-10-09 papers

on PI3K and MAPK signalling in colorectal cancer

Issue of 2022–10–09
eleven papers selected by
Lucas B. Zeiger, CRUK Scotland Institute, Beatson Institute for Cancer Research

Cystine induced-mTORC2 activation through promoting Sin1 phosphorylation to suppress cancer cell ferroptosis.
Computational Modeling Implicates Protein Scaffolding in p38 Regulation of Akt.
The KRASG12D inhibitor MRTX1133 elucidates KRAS-mediated oncogenesis.
Targeting Extracellular Signal-Regulated Protein Kinase 1/2 (ERK1/2) in Cancer: An Update on Pharmacological Small-Molecule Inhibitors.
Linear ubiquitination of PTEN impairs its function to promote prostate cancer progression.
Novel Allosteric Inhibitor-Derived AKT Proteolysis Targeting Chimeras (PROTACs) Enable Potent and Selective AKT Degradation in KRAS/BRAF Mutant Cells.
Response to BRAF targeted therapy is enhanced by co-targeting VEGFRs or WNT/β-Catenin signaling in BRAF-mutant colorectal cancer models.
Identifying selective PI3KC2α inhibitors.
MCL-1 is a master regulator of cancer dependency on fatty acid oxidation.
Wnt Signaling Modulator DKK4 Inhibits Colorectal Cancer Metastasis through an AKT/Wnt/β-catenin Negative Feedback Pathway.
S6K1 phosphorylates Cdk1 and MSH6 to regulate DNA repair.

Mol Nutr Food Res. 2022 Oct 03. e2200186

Cystine induced-mTORC2 activation through promoting Sin1 phosphorylation to suppress cancer cell ferroptosis.

GuoYan Wang, Lei Chen, SenLin Qin, YiNing Zheng, Chao Xia, JunHu Yao, Ping Wang, Lu Deng.

   SCOPE: Mechanistic target of rapamycin (mTOR) serves as a central signaling node in the coordination of cell growth and metabolism, and it functions via two distinct complexes, namely, mTORC1 and mTORC2. mTORC1 plays a crucial role in sensing amino acids, whereas mTORC2 involves in sensing growth factors. However, it remains largely unclear whether mTORC2 can sense amino acids and the mechanism by which amino acids regulate mTORC2 has not been studied.
METHODS AND RESULTS: After treating cells with indicated concentration of amino acids for different time, it is found that the mTORC2 activation was significantly increased in response to amino acids stimulation, especially cystine. Particularly, knockdown SLC7A11 by siRNA showed that SLC7A11-mediated cystine uptake is responsible for activating mTORC2. Mechanistically, we found that p38 is activated in response to cystine stimulation, and co-immunoprecipitation experiments suggested that p38 regulated the assembly of components within mTORC2 by mediating the phosphorylation of the mTORC2 subunit Sin1 in a cystine-dependent manner. Finally, combined with inducers and inhibitors of ferroptosis and cell viability assay, we observed that cystine-mediated regulation of the p38-Sin1-mTOR-AKT pathway induced resistance to ferroptosis.
CONCLUSION: These results indicate that cystine-induced activation of the p38-Sin1-mTORC2-AKT pathway suppresses ferroptosis. This article is protected by copyright. All rights reserved.

Keywords:  Cystine; Ferroptosis; Sin1; mTORC2; p38

DOI:  https://doi.org/10.1002/mnfr.202200186
J Theor Biol. 2022 Oct 01. pii: S0022-5193(22)00285-5. [Epub ahead of print] 111294

Computational Modeling Implicates Protein Scaffolding in p38 Regulation of Akt.

Patrick C Kinnunen, Gary D Luker, Kathryn E Luker, Jennifer J Linderman.

  Cells process environmental cues by activating intracellular signaling pathways with numerous interconnections and opportunities for cross-regulation. We employed a systems biology approach to investigate intersections of kinase p38, a context-dependent tumor suppressor or promoter, with Akt and ERK, two kinases known to promote cell survival, proliferation, and drug resistance in cancer. Using live, single cell microscopy, multiplexed fluorescent reporters of p38, Akt, and ERK activities, and a custom automated image-processing pipeline, we detected marked heterogeneity of signaling outputs in breast cancer cells stimulated with chemokine CXCL12 or epidermal growth factor (EGF). Basal activity of p38 correlated inversely with amplitude of Akt and ERK activation in response to either ligand. Remarkably, small molecule inhibitors of p38 immediately decreased basal activities of Akt and ERK but increased the proportion of cells with high amplitude ligand-induced activation of Akt signaling. To identify mechanisms underlying cross-talk of p38 with Akt signaling, we developed a computational model with subcellular compartmentalization of signaling molecules by scaffold proteins. Dynamics of this model revealed that subcellular scaffolding of Akt accounted for observed regulation by p38. The model also predicted that differences in the amount of scaffold protein in a subcellular compartment captured the observed single cell heterogeneity in signaling. Finally, our model predicted that reduction in kinase signaling can be accomplished by both scaffolding and direct kinase inhibition. However, scaffolding inhibition can potentiate future kinase activity by redistribution of pathway components, potentially amplifying oncogenic signaling. These studies reveal how computational modeling can decipher mechanisms of cross-talk between the p38 and Akt signaling pathways and point to scaffold proteins as central regulators of signaling dynamics and amplitude.

Keywords:  Single cell analysis; cell signaling; compartmentalization; live-cell imaging; scaffolding; signaling kinetics

DOI:  https://doi.org/10.1016/j.jtbi.2022.111294
Nat Med. 2022 Oct 07.

The KRASG12D inhibitor MRTX1133 elucidates KRAS-mediated oncogenesis.

DOI: https://doi.org/10.1038/s41591-022-02008-6
J Med Chem. 2022 Oct 07.

Targeting Extracellular Signal-Regulated Protein Kinase 1/2 (ERK1/2) in Cancer: An Update on Pharmacological Small-Molecule Inhibitors.

Leilei Fu, Siwei Chen, Gu He, Yi Chen, Bo Liu.

Extracellular signal-regulated protein kinase 1/2 (ERK1/2), the only known substrate of MEK1/2, is located downstream of the RAS-RAF-MEK-ERK (MAPK) pathway and is associated with the abnormal activation and poor prognosis of cancer. To date, several small-molecule inhibitors of RAS, RAF, and MEK have been reported to make rapid advances in cancer therapy; however, acquired resistance still occurs, thereby weakening the therapeutic efficacy of these inhibitors. Recently, selective inhibition of ERK1/2 has been regarded as a potential cancer therapeutic strategy that can not only effectively block the MAPK pathway but also overcome drug resistance caused by upstream mutations in RAS, RAF, and MEK. Herein, we summarize the oncogenic roles, key signaling network, and the single- and dual-target inhibitors of ERK1/2 in preclinical and clinical trials. Together, these inspiring findings shed new light on the discovery of more small-molecule inhibitors of ERK1/2 as candidate drugs to improve cancer therapeutics.

DOI: https://doi.org/10.1021/acs.jmedchem.2c01244
Oncogene. 2022 Oct 03.

Linear ubiquitination of PTEN impairs its function to promote prostate cancer progression.

Yanmin Guo, Jianfeng He, Hailong Zhang, Ran Chen, Lian Li, Xiaojia Liu, Caihu Huang, Zhe Qiang, Zihan Zhou, Yanli Wang, Jian Huang, Xian Zhao, Junke Zheng, Guo-Qiang Chen, Jianxiu Yu.

PTEN is frequently mutated in human cancers, which leads to the excessive activation of PI3K/AKT signaling and thus promotes tumorigenesis and drug resistance. Met1-linked ubiquitination (M1-Ubi) is also involved in cancer progression, but the mechanism is poorly defined. Here we find that HOIP, one important component of linear ubiquitin chain assembly complex (LUBAC), promotes prostate cancer (PCa) progression by enhancing AKT signaling in a PTEN-dependent manner. Mechanistically, PTEN is modified by M1-Ubi at two sites K144 and K197, which significantly inhibits PTEN phosphatase activity and thus accelerates PCa progression. More importantly, we identify that the high-frequency mutants PTENR173H and PTENR173C in PCa patients showed the enhanced level of M1-Ubi, which impairs PTEN function in inhibition of AKT phosphorylation and cell growth. We also find that HOIP depletion sensitizes PCa cells to therapeutic agents BKM120 and Enzalutamide. Furthermore, the clinical data analyses confirm that HOIP is upregulated and positively correlated with AKT activation in PCa patient specimen, which may promote PCa progression and increase the risk of PCa biochemical relapse. Together, our study reveals a key role of PTEN M1-Ubi in regulation of AKT activation and PCa progression, which may propose a new strategy for PCa therapy.

DOI: https://doi.org/10.1038/s41388-022-02485-6
J Med Chem. 2022 Oct 05.

Novel Allosteric Inhibitor-Derived AKT Proteolysis Targeting Chimeras (PROTACs) Enable Potent and Selective AKT Degradation in KRAS/BRAF Mutant Cells.

Xufen Yu, Jia Xu, Kaitlyn M Cahuzac, Ling Xie, Yudao Shen, Xian Chen, Jing Liu, Ramon E Parsons, Jian Jin.

AKT is an important target for cancer therapeutics. Significant advancements have been made in developing ATP-competitive and allosteric AKT inhibitors. Recently, several AKT proteolysis targeting chimeras (PROTACs) derived from ATP-competitive AKT inhibitors have been reported, including MS21. While MS21 potently degraded AKT and inhibited the growth in tumor cells harboring PI3K/PTEN pathway mutation, it was largely ineffective in degrading AKT in KRAS/BRAF mutated cells as a single agent. To overcome the AKT degradation resistance in KRAS/BRAF mutated cells, we developed novel AKT PROTACs derived from an AKT allosteric inhibitor, including degrader 62 (MS15). 62 displayed potent and selective AKT degradation activity and potent antiproliferative activity in KRAS/BRAF mutated cancer cells, in addition to PI3K/PTEN mutated cancer cells. Furthermore, 62 was bioavailable in mice through intraperitoneal administration. Overall, 62 is a valuable chemical tool to degrade AKT in cells harboring KRAS/BRAF mutation and expands the tool box for pharmacologically modulating AKT.

DOI: https://doi.org/10.1021/acs.jmedchem.2c01454
Mol Cancer Ther. 2022 Oct 05. pii: MCT-21-0941. [Epub ahead of print]

Response to BRAF targeted therapy is enhanced by co-targeting VEGFRs or WNT/β-Catenin signaling in BRAF-mutant colorectal cancer models.

Khanh B Tran, Sharada V Kolekar, Qian Wang, Jen-Hsing Shih, Christina M Buchanan, Sanjeev Deva, Peter R Shepherd.

The fact that 10% of colorectal cancer (CRC) tumours harbor BRAF V600E mutations suggested targeting BRAF as a potential therapy. However, BRAF inhibitors have only limited single agent in this context. The potential for combination therapy has been shown by the BEACON trial where targeting the EGF receptor with cetuximab greatly increased efficacy of BRAF inhibitors in BRAF-mutant CRC. Therefore, we explored whether efficacy of the mutant BRAF inhibitor vemurafenib could be enhanced by co-targeting of either oncogenic WNT/β-catenin signalling or VEGFR signalling. We find the WNT/-catenin inhibitors pyrvinium, ICG-001 and PKF118-310 attenuate growth of CRC cell lines in vitro with BRAF-mutant lines being relatively more sensitive. Pyrvinium combined with vemurafenib additively or synergistically attenuated growth of CRC cell lines in vitro. The selective and potent VEGFR inhibitor axitinib was most effective against BRAF-mutant CRC cell lines in vitro but addition of vemurafenib did not significantly increase these effects. When tested in vivo in animal tumour models both pyrvinium and axitinib were able to significantly increase the ability of vemurafenib to attenuate tumour growth in xenografts of BRAF mutant CRC cells. The magnitude of these effects was comparable to that induced by a combination of vemurafenib and cetuximab. This was associated with additive effects on release from tumour cells and tumour microenvironment cell types of substances that would normally aid tumour progression. Taken together, this preclinical data indicates that the efficacy of BRAF inhibitor therapy in CRC could be increased by co-targeting either WNT/β-catenin or VEGFRs with small molecule inhibitors.

DOI: https://doi.org/10.1158/1535-7163.MCT-21-0941
Nat Rev Drug Discov. 2022 Oct 03.

Identifying selective PI3KC2α inhibitors.

Sarah Crunkhorn.

DOI: https://doi.org/10.1038/d41573-022-00161-8
Cell Rep. 2022 Oct 04. pii: S2211-1247(22)01286-4. [Epub ahead of print]41(1): 111445

MCL-1 is a master regulator of cancer dependency on fatty acid oxidation.

Michelle S Prew, Utsarga Adhikary, Dong Wook Choi, Erika P Portero, Joao A Paulo, Pruthvi Gowda, Amit Budhraja, Joseph T Opferman, Steven P Gygi, Nika N Danial, Loren D Walensky.

  MCL-1 is an anti-apoptotic BCL-2 family protein essential for survival of diverse cell types and is a major driver of cancer and chemoresistance. The mechanistic basis for the oncogenic supremacy of MCL-1 among its anti-apoptotic homologs is unclear and implicates physiologic roles of MCL-1 beyond apoptotic suppression. Here we find that MCL-1-dependent hematologic cancer cells specifically rely on fatty acid oxidation (FAO) as a fuel source because of metabolic wiring enforced by MCL-1 itself. We demonstrate that FAO regulation by MCL-1 is independent of its anti-apoptotic activity, based on metabolomic, proteomic, and genomic profiling of MCL-1-dependent leukemia cells lacking an intact apoptotic pathway. Genetic deletion of Mcl-1 results in transcriptional downregulation of FAO pathway proteins such that glucose withdrawal triggers cell death despite apoptotic blockade. Our data reveal that MCL-1 is a master regulator of FAO, rendering MCL-1-driven cancer cells uniquely susceptible to treatment with FAO inhibitors.

Keywords:  BCL-2 family; CP: Cancer; CP: Metabolism; MCL-1; apoptosis; cancer; fatty acid oxidation; metabolism

DOI:  https://doi.org/10.1016/j.celrep.2022.111445
J Biol Chem. 2022 Sep 28. pii: S0021-9258(22)00989-9. [Epub ahead of print] 102545

Wnt Signaling Modulator DKK4 Inhibits Colorectal Cancer Metastasis through an AKT/Wnt/β-catenin Negative Feedback Pathway.

Junrong Liang, Lina Sun, Yujun Li, Wanning Liu, Danxiu Li, Ping Chen, Xin Wang, Juan Hui, Jinchi Zhou, Hao Liu, Tianyu Cao, Maogui Pang, Meng Guo, Xin Wang, Xiaodi Zhao, Yuanyuan Lu.

  Aberrant activation of the Wnt/β-catenin signaling pathway is implicated in most malignant cancers, especially in the initiation and progression of colorectal cancer (CRC). DKK4 is a classical inhibitory molecule of the Wnt/β-catenin pathway, but its role in CRC is ambiguous, and the molecular mechanism remains unclear. Here, we determined DKK4 expression was significantly upregulated in 23 CRC cell lines and 229 CRC tissues when analyzed by quantitative PCR and immunohistochemistry, respectively. Our analysis of tissue samples indicated the survival time of CRC patients with high DKK4 expression was longer than that of patients with medium-low DKK4 expression. We examined the effects of DKK4 on cell proliferation and metastasis by cell counting kit-8 assays, Transwell assays, and subcutaneous and metastatic mouse tumor models, and we discovered that DKK4 silencing promoted the metastasis of CRC cells both in vitro and in vivo. Our RNA-seq analysis revealed that AKT2, FZD6, and JUN, which play important roles in AKT and Wnt signaling, were significantly increased after DKK4 knockdown. DKK4 represses Wnt/β-catenin signaling by repressing FZD6 and AKT2/s552 β-catenin in CRC. Further experiments revealed recombinant Wnt3a and LiCl could induce DKK4 expression. Moreover, our bioinformatics analysis and luciferase reporter assays identified posttranscriptional regulators of DKK4 in CRC cells. In summary, DKK4 is elevated in CRC and inhibits cell metastasis by a novel negative feedback mechanism of the Wnt3a/DKK4/AKT/s552 β-catenin regulatory axis to restrict overactivation of Wnt activity in CRC. Therefore, DKK4 restoration may be applied as a potential CRC therapeutic strategy.

Keywords:  AKT; DKK4; Wnt pathway; colorectal cancer; metastasis

DOI:  https://doi.org/10.1016/j.jbc.2022.102545
Elife. 2022 Oct 03. pii: e79128. [Epub ahead of print]11

S6K1 phosphorylates Cdk1 and MSH6 to regulate DNA repair.

Adi Amar-Schwartz, Vered Ben Hur, Amina Jbara, Yuval Cohen, Georgina D Barnabas, Eliran Arbib, Zahava Siegfried, Bayan Mashahreh, Fouad Hassouna, Asaf Shilo, Mohammad Abu-Odeh, Michael Berger, Reuven Wiener, Rami Aqeilan, Tamar Geiger, Rotem Karni.

  The mTORC1 substrate, S6 Kinase 1 (S6K1), is involved in the regulation of cell growth, ribosome biogenesis, glucose homeostasis, and adipogenesis. Accumulating evidence has suggested a role for mTORC1 signaling in the DNA damage response. This is mostly based on the findings that mTORC1 inhibitors sensitized cells to DNA damage. However, a direct role of the mTORC1-S6K1 signaling pathway in DNA repair and the mechanism by which this signaling pathway regulates DNA repair is unknown. In this study, we discovered a novel role for S6K1 in regulating DNA repair through the coordinated regulation of the cell cycle, homologous recombination (HR) DNA repair (HRR) and mismatch DNA repair (MMR) mechanisms. Here, we show that S6K1 orchestrates DNA repair by phosphorylation of Cdk1 at serine 39, causing G2/M cell cycle arrest enabling homologous recombination and by phosphorylation of MSH6 at serine 309, enhancing MMR. Moreover, breast cancer cells harboring RPS6KB1 gene amplification show increased resistance to several DNA damaging agents and S6K1 expression is associated with poor survival of breast cancer patients treated with chemotherapy. Our findings reveal an unexpected function of S6K1 in the DNA repair pathway, serving as a tumorigenic barrier by safeguarding genomic stability.

Keywords:  CDK1; DNA repair; MSH2; MSH6; S6K1; biochemistry; cancer biology; cdk1(cdc2); chemical biology; dna repair; mTORC1; msh2; msh6; s6k1

DOI:  https://doi.org/10.7554/eLife.79128