bims-pimaco 2021-06-27 papers

on PI3K and MAPK signalling in colorectal cancer

Issue of 2021–06–27
eleven papers selected by
Lucas B. Zeiger, CRUK Scotland Institute, Beatson Institute for Cancer Research

Development of a High-throughput NanoBRET Screening Platform to Identify Modulators of the RAS/RAF Interaction.
Focal Adhesion Kinase (FAK) Inhibition Synergizes with KRAS G12C Inhibitors in Treating Cancer through the Regulation of the FAK-YAP Signaling.
Finally, Effective Inhibitors of Mutant KRAS.
NeoRAS wild-type in metastatic colorectal cancer: Myth or truth?-Case series and review of the literature.
Hepcidin sequesters iron to sustain nucleotide metabolism and mitochondrial function in colorectal cancer epithelial cells.
Analysis of the mTOR Interactome using SILAC technology revealed NICE-4 as a novel regulator of mTORC1 activity.
Selective inhibitors of mTORC1 activate 4EBP1 and suppress tumor growth.
Acquired Resistance to KRASG12C Inhibition in Cancer.
Akt scaffold proteins: the key to controlling specificity of Akt signaling.
mTOR Regulation of AGC Kinases: New Twist to an Old Tail.
FDA Approves First KRAS Inhibitor: Sotorasib.

Mol Cancer Ther. 2021 Jun 22. pii: molcanther.0175.2021. [Epub ahead of print]

Development of a High-throughput NanoBRET Screening Platform to Identify Modulators of the RAS/RAF Interaction.

David E Durrant, Emily A Smith, Ekaterina I Goncharova, Nirmala Sharma, Patrick A Alexander, Andrew G Stephen, Curtis J Henrich, Deborah K Morrison.

Activating mutations in RAS are found in approximately 30% of human cancers, resulting in the delivery of a persistent signal to critical downstream effectors that drive tumorigenesis. RAS-driven malignancies respond poorly to conventional cancer treatments and inhibitors that target RAS directly are limited; therefore, the identification of new strategies and/or drugs to disrupt RAS signaling in tumor cells remains a pressing therapeutic need. Taking advantage of the live-cell bioluminescence resonance energy transfer (BRET) methodology, we describe the development of a Nano-BRET screening platform to identify compounds that modulate binding between activated KRAS and the CRAF kinase, an essential effector of RAS that initiates ERK cascade signaling. Using this strategy, libraries containing synthetic compounds, targeted inhibitors, purified natural products, and natural product extracts were evaluated. These efforts resulted in the identification of compounds that inhibit RAS/RAF binding and in turn suppress RAS-driven ERK activation, but also compounds that have the deleterious effect of enhancing the interaction to upregulate pathway signaling. Among the inhibitor hits identified, the majority were compounds derived from natural products, including ones reported to alter KRAS nanoclustering (ophiobolin A), to impact RAF function (HSP90 inhibitors and ROS inducers) as well as some with unknown targets and activities. These findings demonstrate the potential for this screening platform in natural product drug discovery and in the development of new therapeutic agents to target dysregulated RAS signaling in human disease states such as cancer.

DOI: https://doi.org/10.1158/1535-7163.MCT-21-0175
Adv Sci (Weinh). 2021 Jun 20. e2100250

Focal Adhesion Kinase (FAK) Inhibition Synergizes with KRAS G12C Inhibitors in Treating Cancer through the Regulation of the FAK-YAP Signaling.

Baoyuan Zhang, Yan Zhang, Jiangwei Zhang, Ping Liu, Bo Jiao, Zaiqi Wang, Ruibao Ren.

  KRAS mutation is one of the most prevalent genetic drivers of cancer development, yet KRAS mutations are until very recently considered undruggable. There are ongoing trials of drugs that target the KRAS G12C mutation, yet acquired drug resistance from the extended use has already become a major concern. Here, it is demonstrated that KRAS G12C inhibition induces sustained activation of focal adhesive kinase (FAK) and show that a combination therapy comprising KRAS G12C inhibition and a FAK inhibitor (IN10018) achieves synergistic anticancer effects. It can simultaneously reduce the extent of drug resistance. Diverse CDX and PDX models of KRAS G12C mutant cancer are examined and synergistic benefits from the combination therapy are consistently observed. Mechanistically, it is found that both aberrant FAK-YAP signaling and FAK-related fibrogenesis impact on the development of KRAS G12C inhibitor resistance. This study thus illustrates the mechanism of resistance of cancer to the treatment of KRAS G12C inhibitor, as well as an innovative combination therapy to improve treatment outcomes for KRAS G12C mutant cancers.

Keywords:  FAK; KRAS G12C; YAP; drug resistance; synergy

DOI:  https://doi.org/10.1002/advs.202100250
N Engl J Med. 2021 Jun 24. 384(25): 2447-2449

Finally, Effective Inhibitors of Mutant KRAS.

Neal Rosen.

DOI: https://doi.org/10.1056/NEJMe2107884
Eur J Cancer. 2021 Jun 18. pii: S0959-8049(21)00318-X. [Epub ahead of print]153 86-95

NeoRAS wild-type in metastatic colorectal cancer: Myth or truth?-Case series and review of the literature.

Hiroki Osumi, Loredana Vecchione, Ulrich Keilholz, Claudia Vollbrecht, Annabel H S Alig, Jobst C von Einem, Arndt Stahler, Jana K Striefler, Annika Kurreck, Andreas Kind, Dominik P Modest, Sebastian Stintzing, Ivan Jelas.

  Upfront KRAS and NRAS gene testing ('RAS') is the standard of care for metastatic colorectal cancer (mCRC), to guide first-line treatment. The presence of RAS mutation (MT) is a negative predictor for the efficacy of anti-EGFR antibodies and the use of cetuximab and panitumumab is restricted to RAS wild-type (WT) mCRC. Conversion from RAS WT to RAS MT mCRC after treatment with anti-EGFR antibodies is a known and well-described acquired resistance mechanism. The by far less frequent 'NeoRAS wild-type' phenomenon (reversion from RAS MT to RAS WT) has recently drawn attention. The proposed effect of chemotherapy on RAS status in mCRC patients is not fully understood. Because of the intriguing biological consequence of a RAS MT to RAS WT reversion, subsequent treatment of NeoRAS WT patients with anti-EGFR antibodies is increasingly being discussed. Here, we report three clinical cases of NeoRAS WT mCRC patients, which received standard-of-care regimens for RAS MT mCRC. Anti-EGFR antibodies were used in two out of three patients after progression of the disease. One of the patients had a long-term response. In line with our observations, NeoRAS WT phenomenon occurs in clinical practice. Retesting of RAS status during treatment should be discussed in patients with unusual long-term clinical courses of RAS MT mCRC to optimise treatment strategy and to evaluate the use of anti-EGFR antibodies.

Keywords:  Cetuximab; Circulating tumour DNA; Liquid biopsy; Metastatic colorectal cancer; NeoRAS wild-type; Panitumumab; ctDNA

DOI:  https://doi.org/10.1016/j.ejca.2021.05.010
Nat Metab. 2021 Jun 21.

Hepcidin sequesters iron to sustain nucleotide metabolism and mitochondrial function in colorectal cancer epithelial cells.

Andrew J Schwartz, Joshua W Goyert, Sumeet Solanki, Samuel A Kerk, Brandon Chen, Cristina Castillo, Peggy P Hsu, Brian T Do, Rashi Singhal, Michael K Dame, Ho-Joon Lee, Jason R Spence, Samira Lakhal-Littleton, Matthew G Vander Heiden, Costas A Lyssiotis, Xiang Xue, Yatrik M Shah.

Colorectal cancer (CRC) requires massive iron stores, but the complete mechanisms by which CRC modulates local iron handling are poorly understood. Here, we demonstrate that hepcidin is activated ectopically in CRC. Mice deficient in hepcidin specifically in the colon tumour epithelium, compared with wild-type littermates, exhibit significantly diminished tumour number, burden and size in a sporadic model of CRC, whereas accumulation of intracellular iron by deletion of the iron exporter ferroportin exacerbates these tumour parameters. Metabolomic analysis of three-dimensional patient-derived CRC tumour enteroids indicates a prioritization of iron in CRC for the production of nucleotides, which is recapitulated in our hepcidin/ferroportin mouse CRC models. Mechanistically, our data suggest that iron chelation decreases mitochondrial function, thereby altering nucleotide synthesis, whereas exogenous supplementation of nucleosides or aspartate partially rescues tumour growth in patient-derived enteroids and CRC cell lines in the presence of an iron chelator. Collectively, these data suggest that ectopic hepcidin in the tumour epithelium establishes an axis to sequester iron in order to maintain the nucleotide pool and sustain proliferation in colorectal tumours.

DOI: https://doi.org/10.1038/s42255-021-00406-7
Life Sci. 2021 Jun 22. pii: S0024-3205(21)00731-1. [Epub ahead of print] 119745

Analysis of the mTOR Interactome using SILAC technology revealed NICE-4 as a novel regulator of mTORC1 activity.

Yun Wang, Zhenguo Chen, Chunhong Jia, Xiaochun Bai, Yu Jiang, Zhipeng Zou.

  The evolutionarily conserved mechanistic target of rapamycin (mTOR) forms two functionally distinct complexes, -the mTOR complex 1 (mTORC1) and mTOR complex 2 (mTORC2)-which differ in their subunit composition. Although the function of mTORC1 has been studied extensively, the interaction between mTORC1 and the ubiquitin-proteasome system (UPS) remains unclear. To facilitate a thorough understanding of the mechanismby which UPS regulates mTORC1 activity, steady isotope labeling with amino acids in cell culture (SILAC) technology was used to screen for potential mTORC1-interacting UPS members. Fourteen previously unknown proteins bound to mTOR in HEK293 cells with a SILAC ratio (heavy/light, H/L) above 2, five of which are components of the UPS. Subsequent immunoprecipitation analysis confirmed that ubiquitin-relevant protein 2-like (UBAP2L, also known as NICE-4) binds to both mTOR and Raptor, but not Rictor, suggesting that NICE-4 specifically interacts with mTORC1, but not mTORC2. Interestingly, NICE-4 is essential for basic mTORC1 activity in both HeLa cancer cells and HEK293 cells. In addition, NICE-4 depletion markedly suppressed proliferation of both HeLa and HEK293 cells as well as survival of HeLa cells. Collectively, these results revealed the identity of novel mTOR-interacting UPS proteins and established NICE-4 as a critical UPS member that maintains mTORC1 activity.

Keywords:  Cancer; HeLa cells; NICE-4; SILAC; Ubiquitin-proteasome system; mTORC1

DOI:  https://doi.org/10.1016/j.lfs.2021.119745
Nat Chem Biol. 2021 Jun 24.

Selective inhibitors of mTORC1 activate 4EBP1 and suppress tumor growth.

Bianca J Lee, Jacob A Boyer, G Leslie Burnett, Arun P Thottumkara, Nidhi Tibrewal, Stacy L Wilson, Tientien Hsieh, Abby Marquez, Edward G Lorenzana, James W Evans, Laura Hulea, Gert Kiss, Hui Liu, Dong Lee, Ola Larsson, Shannon McLaughlan, Ivan Topisirovic, Zhengping Wang, Zhican Wang, Yongyuan Zhao, David Wildes, James B Aggen, Mallika Singh, Adrian L Gill, Jacqueline A M Smith, Neal Rosen.

The clinical benefits of pan-mTOR active-site inhibitors are limited by toxicity and relief of feedback inhibition of receptor expression. To address these limitations, we designed a series of compounds that selectively inhibit mTORC1 and not mTORC2. These 'bi-steric inhibitors' comprise a rapamycin-like core moiety covalently linked to an mTOR active-site inhibitor. Structural modification of these components modulated their affinities for their binding sites on mTOR and the selectivity of the bi-steric compound. mTORC1-selective compounds potently inhibited 4EBP1 phosphorylation and caused regressions of breast cancer xenografts. Inhibition of 4EBP1 phosphorylation was sufficient to block cancer cell growth and was necessary for maximal antitumor activity. At mTORC1-selective doses, these compounds do not alter glucose tolerance, nor do they relieve AKT-dependent feedback inhibition of HER3. Thus, in preclinical models, selective inhibitors of mTORC1 potently inhibit tumor growth while causing less toxicity and receptor reactivation as compared to pan-mTOR inhibitors.

DOI: https://doi.org/10.1038/s41589-021-00813-7
N Engl J Med. 2021 Jun 24. 384(25): 2382-2393

Acquired Resistance to KRASG12C Inhibition in Cancer.

Mark M Awad, Shengwu Liu, Igor I Rybkin, Kathryn C Arbour, Julien Dilly, Viola W Zhu, Melissa L Johnson, Rebecca S Heist, Tejas Patil, Gregory J Riely, Joseph O Jacobson, Xiaoping Yang, Nicole S Persky, David E Root, Kristen E Lowder, Hanrong Feng, Shannon S Zhang, Kevin M Haigis, Yin P Hung, Lynette M Sholl, Brian M Wolpin, Julie Wiese, Jason Christiansen, Jessica Lee, Alexa B Schrock, Lee P Lim, Kavita Garg, Mark Li, Lars D Engstrom, Laura Waters, J David Lawson, Peter Olson, Piro Lito, Sai-Hong I Ou, James G Christensen, Pasi A Jänne, Andrew J Aguirre.

BACKGROUND: Clinical trials of the KRAS inhibitors adagrasib and sotorasib have shown promising activity in cancers harboring KRAS glycine-to-cysteine amino acid substitutions at codon 12 (KRASG12C). The mechanisms of acquired resistance to these therapies are currently unknown.
METHODS: Among patients with KRASG12C -mutant cancers treated with adagrasib monotherapy, we performed genomic and histologic analyses that compared pretreatment samples with those obtained after the development of resistance. Cell-based experiments were conducted to study mutations that confer resistance to KRASG12C inhibitors.
RESULTS: A total of 38 patients were included in this study: 27 with non-small-cell lung cancer, 10 with colorectal cancer, and 1 with appendiceal cancer. Putative mechanisms of resistance to adagrasib were detected in 17 patients (45% of the cohort), of whom 7 (18% of the cohort) had multiple coincident mechanisms. Acquired KRAS alterations included G12D/R/V/W, G13D, Q61H, R68S, H95D/Q/R, Y96C, and high-level amplification of the KRASG12C allele. Acquired bypass mechanisms of resistance included MET amplification; activating mutations in NRAS, BRAF, MAP2K1, and RET; oncogenic fusions involving ALK, RET, BRAF, RAF1, and FGFR3; and loss-of-function mutations in NF1 and PTEN. In two of nine patients with lung adenocarcinoma for whom paired tissue-biopsy samples were available, histologic transformation to squamous-cell carcinoma was observed without identification of any other resistance mechanisms. Using an in vitro deep mutational scanning screen, we systematically defined the landscape of KRAS mutations that confer resistance to KRASG12C inhibitors.
CONCLUSIONS: Diverse genomic and histologic mechanisms impart resistance to covalent KRASG12C inhibitors, and new therapeutic strategies are required to delay and overcome this drug resistance in patients with cancer. (Funded by Mirati Therapeutics and others; ClinicalTrials.gov number, NCT03785249.).

DOI: https://doi.org/10.1056/NEJMoa2105281
Am J Physiol Cell Physiol. 2021 06 23.

Akt scaffold proteins: the key to controlling specificity of Akt signaling.

Fan Bao, Peiqi Hao, Su An, Yang Yang, Ying Liu, Qian Hao, Ejaz Mubashir, Xiao-Xi Guo, Tian-Rui Xu.

  The PI3K-Akt signaling pathway plays an essential role in regulating cell proliferation and apoptosis. Akt kinase is at the center of this signaling pathway and interacts with a variety of proteins. Overexpression of Akt has been found in almost 80% of tumors, however, inhibiting Akt has serious clinical side effects so is not a suitable treatment for cancer. During recent years, Akt scaffold proteins have received increasing attention for their ability to regulate Akt signaling and have emerged as potential targets for cancer therapy. In this paper, we categorize AKT kinase scaffold proteins into four groups based on their cellular location: membrane-bound activator and inhibitor, cytoplasm, and endosome. We describe how these scaffolds interact with Akt kinase, how they affect AKT activity, and how they regulate the specificity of Akt signaling. We also discuss the clinical application of Akt-scaffold proteins as targets for cancer therapy.

Keywords:  Akt/PKB; cancer; interactome; phosphorylation; scaffold protein

DOI:  https://doi.org/10.1152/ajpcell.00146.2020
Mol Pharmacol. 2021 Jun 21. pii: MOLPHARM-MR-2021-000310. [Epub ahead of print]

mTOR Regulation of AGC Kinases: New Twist to an Old Tail.

Timothy R Baffi, Alexandra C Newton.

  The family of AGC kinases not only regulate cellular biology by phosphorylating substrates, but are themselves controlled by phosphorylation. Phosphorylation generally occurs at two conserved regions in these kinases: a loop near the entrance to the active site, termed the activation loop, that correctly aligns residues for catalysis, and a C-terminal tail whose phosphorylation at a site termed the hydrophobic motif stabilizes the active conformation. Whereas phosphorylation of the activation loop is well established to be catalyzed by the phosphoinositide-dependent kinase 1 (PDK1), the mechanism of phosphorylation of the C-tail hydrophobic motif has been controversial. For a subset of AGC kinases, which includes most protein kinase C (PKC) isozymes and Akt, phosphorylation of the hydrophobic motif in cells was shown to depend on mTORC2 over 15 years ago, yet whether by direct phosphorylation or by another mechanism has remained elusive. The recent identification of a novel and evolutionarily conserved phosphorylation site on the C-tail termed the TOR-Interaction Motif (TIM) has finally unraveled the mystery of how mTORC2 regulates its client kinases. mTORC2 does not directly phosphorylate the hydrophobic motif, rather it converts kinases such as PKC and Akt into a conformation that can ultimately autophosphorylate at the hydrophobic motif. Identification of the direct mTOR phosphorylation that facilitates auto-regulation of the C-tail hydrophobic motif revises the activation mechanisms of mTOR-regulated AGC kinases. This new twist to an old tail opens avenues for therapeutic intervention. Significance Statement The enzyme mTORC2 has been an enigmatic regulator of AGC kinases such as protein kinase C (PKC) and Akt. The recent discovery of a motif named the TOR Interaction Motif in the C-tail of these kinases solves the mystery: mTORC2 marks these kinases for maturity by, ultimately, facilitating autophosphorylation another C-tail site, the hydrophobic motif.

Keywords:  AKT; Protein Kinase C (PKC); mTOR

DOI:  https://doi.org/10.1124/molpharm.121.000310
Cancer Discov. 2021 Jun 22.

FDA Approves First KRAS Inhibitor: Sotorasib.

The FDA has approved the first KRAS-targeted therapy, sotorasib, for patients with previously treated non-small cell lung cancer with KRASG12C mutations. In a phase II trial, the drug yielded a median progression-free survival of 6.8 months in patients whose disease had advanced despite treatment with standard therapies, namely platinum-based chemotherapy and PD-1-PD-L1 inhibitors.

DOI: https://doi.org/10.1158/2159-8290.CD-NB2021-0362