bims-pimaco Biomed News
on PI3K and MAPK signalling in colorectal cancer
Issue of 2021‒02‒28
eight papers selected by
Lucas B. Zeiger
Beatson Institute for Cancer Research


  1. J Cell Biol. 2021 May 03. pii: e202004010. [Epub ahead of print]220(5):
      The mammalian target of rapamycin complex 1 (mTORC1) integrates mitogenic and stress signals to control growth and metabolism. Activation of mTORC1 by amino acids and growth factors involves recruitment of the complex to the lysosomal membrane and is further supported by lysosome distribution to the cell periphery. Here, we show that translocation of lysosomes toward the cell periphery brings mTORC1 into proximity with focal adhesions (FAs). We demonstrate that FAs constitute discrete plasma membrane hubs mediating growth factor signaling and amino acid input into the cell. FAs, as well as the translocation of lysosome-bound mTORC1 to their vicinity, contribute to both peripheral and intracellular mTORC1 activity. Conversely, lysosomal distribution to the cell periphery is dispensable for the activation of mTORC1 constitutively targeted to FAs. This study advances our understanding of spatial mTORC1 regulation by demonstrating that the localization of mTORC1 to FAs is both necessary and sufficient for its activation by growth-promoting stimuli.
    DOI:  https://doi.org/10.1083/jcb.202004010
  2. Cancer Res. 2021 Feb 25. pii: canres.2929.2020. [Epub ahead of print]
      Pancreatic adenocarcinoma (PDAC) epitomizes a deadly cancer driven by abnormal KRAS signalling. Here we show that the eIF4A RNA helicase is required for translation of key KRAS signaling molecules and that pharmacological inhibition of eIF4A has single-agent activity against murine and human PDAC models at safe dose levels. EIF4A was uniquely required for the translation of mRNAs with long and highly structured 5'UTRs including those with multiple G-quadruplex (GQ) elements. Computational analyses identified these features in mRNAs encoding KRAS and key downstream molecules. Transcriptome-scale ribosome footprinting accurately identified eIF4A-dependent mRNAs in PDAC including critical KRAS signaling molecules such as PI3K, RALA, RAC2, MET, MYC, and YAP1. These findings contrast with a recent study that relied on an older method, polysome fractionation, and implicated redox-related genes as eIF4A clients. Together, our findings highlight the power of ribosome footprinting in conjunction with deep RNA sequencing in accurately decoding translational control mechanisms and define the therapeutic mechanism of eIF4A inhibitors in PDAC.
    DOI:  https://doi.org/10.1158/0008-5472.CAN-20-2929
  3. BMC Cancer. 2021 Feb 25. 21(1): 193
      BACKGROUND: KRAS is the most frequently mutated oncogene in cancer, however efforts to develop targeted therapies have been largely unsuccessful. Recently, two small-molecule inhibitors, AMG 510 and MRTX849, have shown promising activity in KRAS G12C-mutant solid tumors. The current study aims to assess the molecular profile of KRAS G12C in colorectal (CRC) and non-small-cell lung cancer (NSCLC) tested in a clinical certified laboratory.METHODS: CRC and NSCLC samples submitted for KRAS testing between 2017 and 2019 were reviewed. CRC samples were tested for KRAS and NRAS by pyrosequencing, while NSCLC samples were submitted to next generation sequencing of KRAS, NRAS, EGFR, and BRAF.
    RESULTS: The dataset comprised 4897 CRC and 4686 NSCLC samples. Among CRC samples, KRAS was mutated in 2354 (48.1%). Most frequent codon 12 mutations were G12D in 731 samples (14.9%) and G12V in 522 (10.7%), followed by G12C in 167 (3.4%). KRAS mutations were more frequent in females than males (p = 0.003), however this difference was exclusive of non-G12C mutants (p < 0.001). KRAS mutation frequency was lower in the South and North regions (p = 0.003), but again KRAS G12C did not differ significantly (p = 0.80). In NSCLC, KRAS mutations were found in 1004 samples (21.4%). As opposed to CRC samples, G12C was the most common mutation in KRAS, in 346 cases (7.4%). The frequency of KRAS G12C was higher in the South and Southeast regions (p = 0.012), and lower in patients younger than 50 years (p < 0.001). KRAS G12C mutations were largely mutually exclusive with other driver mutations; only 11 NSCLC (3.2%) and 1 CRC (0.6%) cases had relevant co-mutations.
    CONCLUSIONS: KRAS G12C presents in frequencies higher than several other driver mutations, and may represent a large volume of patients in absolute numbers. KRAS testing should be considered in all CRC and NSCLC patients, independently of clinical or demographic characteristics.
    Keywords:  Colorectal neoplasms; KRAS; Lung neoplasms; Molecular diagnostics; Molecular targeted therapy
    DOI:  https://doi.org/10.1186/s12885-021-07884-8
  4. Gut. 2021 Feb 25. pii: gutjnl-2020-321534. [Epub ahead of print]
    Huyghe JR, Harrison TA, Bien SA, Hampel H, Figueiredo JC, Schmit SL, Conti DV, Chen S, Qu C, Lin Y, Barfield R, Baron JA, Cross AJ, Diergaarde B, Duggan D, Harlid S, Imaz L, Kang HM, Levine DM, Perduca V, Perez-Cornago A, Sakoda LC, Schumacher FR, Slattery ML, Toland AE, van Duijnhoven FJB, Van Guelpen B, Agudo A, Albanes D, Alonso MH, Anderson K, Arnau-Collell C, Arndt V, Banbury BL, Bassik MC, Berndt SI, Bézieau S, Bishop DT, Boehm J, Boeing H, Boutron-Ruault MC, Brenner H, Brezina S, Buch S, Buchanan DD, Burnett-Hartman A, Caan BJ, Campbell PT, Carr PR, Castells A, Castellví-Bel S, Chan AT, Chang-Claude J, Chanock SJ, Curtis KR, de la Chapelle A, Easton DF, English DR, Feskens EJM, Gala M, Gallinger SJ, Gauderman WJ, Giles GG, Goodman PJ, Grady WM, Grove JS, Gsur A, Gunter MJ, Haile RW, Hampe J, Hoffmeister M, Hopper JL, Hsu WL, Huang WY, Hudson TJ, Jenab M, Jenkins MA, Joshi AD, Keku TO, Kooperberg C, Kühn T, Küry S, Le Marchand L, Lejbkowicz F, Li CI, Li L, Lieb W, Lindblom A, Lindor NM, Männistö S, Markowitz SD, Milne RL, Moreno L, Murphy N, Nassir R, Offit K, Ogino S, Panico S, Parfrey PS, Pearlman R, Pharoah PDP, Phipps AI, Platz EA, Potter JD, Prentice RL, Qi L, Raskin L, Rennert G, Rennert HS, Riboli E, Schafmayer C, Schoen RE, Seminara D, Song M, Su YR, Tangen CM, Thibodeau SN, Thomas DC, Trichopoulou A, Ulrich CM, Visvanathan K, Vodicka P, Vodickova L, Vymetalkova V, Weigl K, Weinstein SJ, White E, Wolk A, Woods MO, Wu AH, Abecasis GR, Nickerson DA, Scacheri PC, Kundaje A, Casey G, Gruber SB, Hsu L, Moreno V, Hayes RB, Newcomb PA, Peters U.
      OBJECTIVE: An understanding of the etiologic heterogeneity of colorectal cancer (CRC) is critical for improving precision prevention, including individualized screening recommendations and the discovery of novel drug targets and repurposable drug candidates for chemoprevention. Known differences in molecular characteristics and environmental risk factors among tumors arising in different locations of the colorectum suggest partly distinct mechanisms of carcinogenesis. The extent to which the contribution of inherited genetic risk factors for CRC differs by anatomical subsite of the primary tumor has not been examined.DESIGN: To identify new anatomical subsite-specific risk loci, we performed genome-wide association study (GWAS) meta-analyses including data of 48 214 CRC cases and 64 159 controls of European ancestry. We characterised effect heterogeneity at CRC risk loci using multinomial modelling.
    RESULTS: We identified 13 loci that reached genome-wide significance (p<5×10-8) and that were not reported by previous GWASs for overall CRC risk. Multiple lines of evidence support candidate genes at several of these loci. We detected substantial heterogeneity between anatomical subsites. Just over half (61) of 109 known and new risk variants showed no evidence for heterogeneity. In contrast, 22 variants showed association with distal CRC (including rectal cancer), but no evidence for association or an attenuated association with proximal CRC. For two loci, there was strong evidence for effects confined to proximal colon cancer.
    CONCLUSION: Genetic architectures of proximal and distal CRC are partly distinct. Studies of risk factors and mechanisms of carcinogenesis, and precision prevention strategies should take into consideration the anatomical subsite of the tumour.
    Keywords:  cancer genetics; cancer susceptibility; colon carcinogenesis; colorectal cancer; genetic polymorphisms
    DOI:  https://doi.org/10.1136/gutjnl-2020-321534
  5. Future Oncol. 2021 Feb 25.
      Background: Data on RAS testing practices prior to metastatic colorectal cancer (mCRC) treatment initiation are lacking in the USA. Materials & methods: Flatiron data were utilized for patients diagnosed with mCRC between 2011 and 2017. Flatiron is a longitudinal, demographically and geographically diverse database representing data from over 1.5 million active US patients treated at 255 community and hospital-affiliated oncology clinics. Results: Among 17,387 mCRC patients 69% were RAS tested and 31% were never tested. Timing of RAS testing was as follows: 23% were tested at the time of their initial CRC diagnosis, 60% following mCRC diagnosis but prior to first line of treatment, 3% prior to third line, the remaining 14% were tested following third line. Conclusion: A third (31%) of patients failed to receive RAS testing, therefore all treatment options were unavailable to them. These data highlight how universal testing has not been achieved.
    Keywords:  KRAS; NRAS; RAS; anti-EGFR; metastatic colorectal cancer; panitumumab
    DOI:  https://doi.org/10.2217/fon-2020-1075
  6. Cell Metab. 2021 Feb 17. pii: S1550-4131(21)00057-7. [Epub ahead of print]
      Mitochondrial respiration is critical for cell proliferation. In addition to producing ATP, respiration generates biosynthetic precursors, such as aspartate, an essential substrate for nucleotide synthesis. Here, we show that in addition to depleting intracellular aspartate, electron transport chain (ETC) inhibition depletes aspartate-derived asparagine, increases ATF4 levels, and impairs mTOR complex I (mTORC1) activity. Exogenous asparagine restores proliferation, ATF4 and mTORC1 activities, and mTORC1-dependent nucleotide synthesis in the context of ETC inhibition, suggesting that asparagine communicates active respiration to ATF4 and mTORC1. Finally, we show that combination of the ETC inhibitor metformin, which limits tumor asparagine synthesis, and either asparaginase or dietary asparagine restriction, which limit tumor asparagine consumption, effectively impairs tumor growth in multiple mouse models of cancer. Because environmental asparagine is sufficient to restore tumor growth in the context of respiration impairment, our findings suggest that asparagine synthesis is a fundamental purpose of tumor mitochondrial respiration, which can be harnessed for therapeutic benefit to cancer patients.
    Keywords:  asparaginase; asparagine; cancer metabolism; cancer treatment; dietary restriction; metformin; respiration
    DOI:  https://doi.org/10.1016/j.cmet.2021.02.001
  7. Clin Cancer Res. 2021 Feb 22. pii: clincanres.CCR-20-3872-A.2020. [Epub ahead of print]
      PURPOSE: Covalent inhibitors of KRASG12C specifically target tumors driven by this form of mutant KRAS, yet early studies show that bypass signaling drives adaptive resistance. While several combination strategies have been shown to improve efficacy of KRASG12C inhibitors, underlying mechanisms and predictive strategies for patient enrichment are less clear.EXPERIMENTAL DESIGN: We performed mass spectrometry based phosphoproteomics analysis in KRASG12C cell lines after short term treatment with ARS-1620. To understand signaling diversity and cell-type specific markers, we compared proteome and phosphoproteomes of KRASG12C cells. Gene expression patterns of KRASG12C cell lines and lung tumor tissues were examined.
    RESULTS: Our analysis suggests cell-type specific perturbation to ERBB2/3 signaling compensate for repressed ERK and AKT signaling following ARS-1620 treatment in epithelial cell type, and this subtype was also more responsive to co-inhibition of SHP2 and SOS1. Conversely, both high basal and feedback activation of FGFR or AXL signaling was identified in mesenchymal cells. Inhibition of FGFR signaling suppress feedback activation of ERK and mTOR, while AXL inhibition suppress PI3K pathway. In both cell lines and human lung cancer tissues with KRASG12C we observed high basal ERBB2/3 associated with epithelial gene signatures while higher basal FGFR1 and AXL was observed in cells/tumors with mesenchymal gene signatures.
    CONCLUSIONS: Our phosphoproteomic study identified cell-type adaptive responses to KRASG12C inhibitors. Markers and targets associated with ERBB2/3 signaling in epithelial subtype and FGFR1/AXL signaling in mesenchymal subtype should be considered in patient enrichment schemes with KRASG12C inhibitors.
    DOI:  https://doi.org/10.1158/1078-0432.CCR-20-3872
  8. Gut. 2021 Feb 22. pii: gutjnl-2020-323924. [Epub ahead of print]
      
    Keywords:  colorectal cancer; drug resistance; stem cells
    DOI:  https://doi.org/10.1136/gutjnl-2020-323924