bims-pimaco Biomed News
on PI3K and MAPK signalling in colorectal cancer
Issue of 2021‒01‒03
ten papers selected by
Lucas B. Zeiger
Beatson Institute for Cancer Research

  1. FEBS J. 2020 Dec 31.
      Protein synthesis is one of the most essential process in every kingdom of life, and its dysregulation is known as a driving force in cancer development and tumorigenesis. Multiple signaling pathways converge on the translation initiation machinery, and this plays a crucial role in regulating differential gene expression. In colorectal cancer, dysregulation of initiation results in translational reprogramming, which promotes the selective translation of mRNAs required for many oncogenic processes. The majority of upstream mutations found in colorectal cancer, including alterations in the WNT, MAPK and PI3K\AKT pathways, have been demonstrated to play a significant role in translational reprogramming and intestinal tumorigenesis. Many translation initiation factors are also known to be dysregulated, resulting in translational reprogramming during tumor initiation and/or maintenance. In this review, we outline the role of translational reprogramming that occurs during colorectal cancer development and progression and, highlight some of the most critical factors affecting the etiology of this disease.
    Keywords:  Colorectal cancer; Protein synthesis; RNA translation; Translation initiation; Translational control
  2. Cell Rep. 2020 Dec 29. pii: S2211-1247(20)31553-9. [Epub ahead of print]33(13): 108564
      The mechanistic target of rapamycin complex 2 (mTORC2) controls cell metabolism and survival in response to environmental inputs. Dysregulation of mTORC2 signaling has been linked to diverse human diseases, including cancer and metabolic disorders, highlighting the importance of a tightly controlled mTORC2. While mTORC2 assembly is a critical determinant of its activity, the factors regulating this event are not well understood, and it is unclear whether this process is regulated by growth factors. Here, we present data, from human cell lines and mice, describing a mechanism by which growth factors regulate ubiquitin-specific protease 9X (USP9X) deubiquitinase to stimulate mTORC2 assembly and activity. USP9X removes Lys63-linked ubiquitin from RICTOR to promote its interaction with mTOR, thereby facilitating mTORC2 signaling. As mTORC2 is central for cellular homeostasis, understanding the mechanisms regulating mTORC2 activation toward its downstream targets is vital for our understanding of physiological processes and for developing new therapeutic strategies in pathology.
    Keywords:  RICTOR; USP9X; growth factor signaling; mTORC2; mechanistic target of rapamycin complex 2; posttranslational modification; ubiquitin-specific protease 9X
  3. Int J Mol Sci. 2020 Dec 22. pii: E23. [Epub ahead of print]22(1):
      The mechanistic target of rapamycin complex 1 (mTORC1) integrates signals from growth factors and nutrients to control biosynthetic processes, including protein, lipid, and nucleic acid synthesis. Dysregulation in the mTORC1 network underlies a wide array of pathological states, including metabolic diseases, neurological disorders, and cancer. Tumor cells are characterized by uncontrolled growth and proliferation due to a reduced dependency on exogenous growth factors. The genetic events underlying this property, such as mutations in the PI3K-Akt and Ras-Erk signaling networks, lead to constitutive activation of mTORC1 in nearly all human cancer lineages. Aberrant activation of mTORC1 has been shown to play a key role for both anabolic tumor growth and resistance to targeted therapeutics. While displaying a growth factor-independent mTORC1 activity and proliferation, tumors cells remain dependent on exogenous nutrients such as amino acids (AAs). AAs are an essential class of nutrients that are obligatory for the survival of any cell. Known as the building blocks of proteins, AAs also act as essential metabolites for numerous biosynthetic processes such as fatty acids, membrane lipids and nucleotides synthesis, as well as for maintaining redox homeostasis. In most tumor types, mTORC1 activity is particularly sensitive to intracellular AA levels. This dependency, therefore, creates a targetable vulnerability point as cancer cells become dependent on AA transporters to sustain their homeostasis. The following review will discuss the role of AA transporters for mTORC1 signaling in cancer cells and their potential as therapeutic drug targets.
    Keywords:  ASCT2; LAT1; SNAT2; amino acid transporters; cancer; growth factors; mTORC1; nutrients; xCT
  4. J Clin Med. 2020 Dec 29. pii: E87. [Epub ahead of print]10(1):
      BACKGROUND: Tumor tissue (T) mutational analysis represents the standard for metastatic colorectal cancer (mCRC); however, circulating tumor DNA (ctDNA) detected by liquid biopsy in plasma (PL) can better represent tumor heterogeneity.METHODS: mCRC patients undergoing standard first-line chemotherapy with known T-KRAS/NRAS/BRAF status were enrolled in the present prospective study. PL mutations were assessed within 2 weeks before chemotherapy start with real time PCR and correlated with T status and Progression free survival (PFS). Clinical and biochemical variables including also total number of tumor lesions (TNL) and the sum of maximum diameter (SMD) of all lesions were assessed as potential predictors of T/PL discordance.
    RESULTS: Among 45 enrolled patients, all BRAF mutations were concordant between T and PL and there were 20% of patients RAS discordant: 9% wild type in T and mutated in PL and 11% mutated in T and wild type in PL. T mutations were significantly associated to median PFS (mPFS of 4.5, 8.3 and 22.9 months for T-BRAF mutated, T-RAS mutated, and T-wild type patients, respectively, p for trend 0.00014). PL mutations further refined prognosis: RAS wild type in T and mutated in PL had significantly shorter PFS than concordant RAS wild type in T and PL: mPFS 9.6 vs. 23.3 months, respectively, p = 0.02. Patients RAS mutated in T and wild type in PL had longer PFS than concordant RAS mutated in T and PL: 24.4 vs. 7.8 months, respectively, p = 0.008. At a multivariate cox regression analysis for PFS, PL mutations were independent prognostic factor superior to T analysis (HR 0.13, p = 0.0008). At multivariate logistic regression analysis TNL and SMD were significant predictors of discordant cases.
    CONCLUSIONS: PL mutational analysis allows a better prognostication than T analysis alone and could help in mCRC treatment management.
    Keywords:  ctDNA; liquid biopsy; metastatic colorectal cancer
  5. Int J Oncol. 2020 Nov 23.
      W922, a novel PI3K/Akt/mTOR pathway inhibitor, exhibits efficient anti‑tumor effects on HCT116, MCF‑7 and A549 human cancer cells compared with other synthesized compounds. The present study aimed to investigate its anti‑tumor effects on colorectal cancer cells. A total, of seven different colorectal cell lines were selected to test the anti‑proliferation profile of W922, and HCT116 was found to be the most sensitive cell line to the drug treatment. W922 inhibited HCT116 cell viability and cell proliferation in vitro in concentration‑ and time‑dependent manners. Furthermore, W922 suppressed the tumor growth in a xenograft mouse model and exhibited low toxicity. The proteomic alterations in W922‑treated HCT116 cells were found to be associated with cell cycle arrest, negative regulation of signal transduction and lysosome‑related processes. W922 caused cell cycle arrest of HCT116 cells in G0‑G1 phase, but only triggered slight apoptosis. In addition, the PI3K/Akt/mTOR signaling proteins were dephosphorylated upon W922 treatment. It has been reported that inhibition of mTOR is relevant to autophagy, and the present results also indicated that W922 was involved in autophagy induction. An autophagy inhibitor, chloroquine, was used to co‑treat HCT116 cells with W922, and it was identified that the cell cycle arrest was impaired. Moreover, co‑treatment of W922 and chloroquine led to a significant population of apoptotic cells, thus providing a promising therapeutic strategy for colorectal cancer.
  6. Clin Cancer Res. 2020 Dec 22. pii: clincanres.2563.2020. [Epub ahead of print]
      PURPOSE: Targeting RAF for anti-tumor therapy in RAS-mutant tumors holds promise. Herein we describe in detail novel properties of the type II RAF inhibitor LXH254.EXPERIMENTAL DESIGN: LXH254 was profiled in biochemical, in vitro, and in vivo assays including examining the activities of the drug in a large panel of cancer-derived cell lines, and a comprehensive set of in vivo models. In addition, activity of LXH254 was assessed in cells where different sets of RAF paralogs were ablated, or that expressed kinase-impaired and dimer-deficient variants of ARAF.
    RESULTS: We describe an unexpected paralog selectivity of LXH254, which is able to potently inhibit BRAF and CRAF, but has less activity against ARAF. LXH254 was active in models harboring BRAF alterations, including atypical BRAF alterations co-expressed with mutant K/NRAS, and NRAS mutants, but had only modest activity in KRAS mutants. In RAS mutant lines loss of ARAF, but not BRAF or CRAF, sensitized cells to LXH254. ARAF-mediated resistance to LXH254 required both kinase function and dimerization. Higher concentrations of LXH254 were required to inhibit signaling in RAS-mutant cells expressing only ARAF relative to BRAF or CRAF. Moreover, specifically in cells expressing only ARAF, LXH254 caused paradoxical activation of MAPK signaling in a manner similar to dabrafenib. Lastly, in vivo, LXH254 drove complete regressions of isogenic variants of RAS mutant cells lacking ARAF expression, while parental lines were only modestly sensitive.
    CONCLUSIONS: LXH254 is a novel RAF-inhibitor able to inhibit dimerized BRAF and CRAF as well as monomeric BRAF while largely sparing ARAF.
  7. J Clin Oncol. 2020 Dec 23. JCO2001994
      PURPOSE: BRAFV600E mutations are rarely associated with objective responses to the BRAF inhibitor vemurafenib in patients with metastatic colorectal cancer (CRC). Blockade of BRAFV600E by vemurafenib causes feedback upregulation of EGFR, whose signaling activities can be impeded by cetuximab.METHODS: One hundred six patients with BRAFV600E-mutated metastatic CRC previously treated with one or two regimens were randomly assigned to irinotecan and cetuximab with or without vemurafenib (960 mg PO twice daily).
    RESULTS: Progression-free survival, the primary end point, was improved with the addition of vemurafenib (hazard ratio, 0.50, P = .001). The response rate was 17% versus 4% (P = .05), with a disease control rate of 65% versus 21% (P < .001). A decline in circulating tumor DNA BRAFV600E variant allele frequency was seen in 87% versus 0% of patients (P < .001), with a low incidence of acquired RAS alterations at the time of progression. RNA profiling suggested that treatment benefit did not depend on previously established BRAF subgroups or the consensus molecular subtype.
    CONCLUSION: Simultaneous inhibition of EGFR and BRAF combined with irinotecan is effective in BRAFV600E-mutated CRC.
  8. J Biochem Mol Toxicol. 2020 Dec 28. e22665
      Colorectal cancer (CRC) is the leading type of diagnosed cancer; globally, it resides in the fourth-leading origin of cancer-interrelated mortality in the globe. The treatment strategies were chemotherapy and potent radiotherapy. Although chemotherapy treatment can eliminate tumor cells, it remains with unnecessary toxic effects in cancer patients. Therefore, the identification of natural-based compounds, which have selectively inhibiting target proteins with limited toxicity that can facilitate the therapeutic approaches against CRC. In this existing approach, which highlights the binding efficacy of our anthraquinone compound, purpurin against phospholysine phosphohistidine inorganic pyrophosphate phosphatase (LHPP) protein restrains the CRC cell growth by inhibiting phosphatidylinositol-3-kinase/protein kinase B (PI3K/AKT), cell proliferation, and inducing apoptosis signaling. Primarily, purpurin (36 μM) exposed to HCT-116 cells and incubated for 24 and 48 h could induce reactive oxygen species production, subsequently alter mitochondrion membrane, and increase the apoptotic cells in HCT-116. LHPP, a kind of histidine phosphatase protein, has been considered as a tumor suppressor in numerous carcinomas. However, purpurin-mediated LHPP proteins and its associated molecular events in CRC remain unclear. In our docking studies revealed that purpurin has been strongly interacts with LHPP via hydrophobic and hydrophilic binding interaction. Western blot results confirmed that purpurin enhances the expression of LHPP protein, thereby inhibits the expression of phosphorylated-PI3K/AKT, EGFR, cyclin-D1, PCNA in HCT-116 cells. Moreover, purpurin induces messenger RNA expression of apoptotic genes (Bax, CASP-9, and CASP-3) in HCT-116 cells. Thus, we conclude that purpurin could be a natural and useful compound, which inhibits the growth of CRC cells through the activation of LHPP proteins.
    Keywords:  HCT-116; LHPP; colon cancer; purpurin
  9. J Biol Chem. 2020 Dec 30. pii: jbc.RA120.015188. [Epub ahead of print]
      Oncogenic K-Ras (K-RasG12V) promotes senescence in normal cells but fuels transformation of cancer cells after the senescence barrier is bypassed. The mechanisms regulating this pleiotropic function of K-Ras remain to be fully established and bear high pathological significance. We find that K-RasG12V activates the angiotensinogen (AGT) gene promoter and promotes AGT protein expression in a Kruppel Like Factor 6 (KLF6)-dependent manner in normal cells. We show that AGT is then converted to angiotensin II (Ang II) in a cell-autonomous manner by cellular proteases. We show that blockade of the Ang II receptor type 1 (AT1-R) in normal cells inhibits oncogene-induced senescence (OIS). We provide evidence that the oncogenic K-Ras-induced synthesis of Ang II and AT1-R activation promote senescence through caveolin-1-dependent and NOX2-mediated oxidative stress. Interestingly, we find that expression of AGT remains elevated in lung cancer cells but in a KLF6-independent and High Mobility Group AT-Hook 1 (HMGA1)-dependent manner. We show that Ang II-mediated activation of the AT1-R promotes cell proliferation and anchorage-independent growth of lung cancer cells through a STAT3-dependent pathway. Finally, we find that expression of AGT is elevated in lung tumors of K-RasLA2-G12D mice, a mouse model of lung cancer, and human lung cancer. Treatment with the AT1-R antagonist losartan inhibits lung tumor formation in K-RasLA2-G12D mice. Together, our data provide evidence of the existence of a novel cell-autonomous and pleiotropic Ang II-dependent signaling pathway through which oncogenic K-Ras promotes OIS in normal cells while fueling transformation in cancer cells.
    Keywords:  Ras protein; angiotensin II; caveolin; cellular senescence; oncogene
  10. J Med Chem. 2020 Dec 24.
      The phosphoinositide 3-kinase (PI3K)/mammalian target of rapamycin (mTOR) signaling pathway is a frequently dysregulated pathway in human cancer, and PI3Kα is one of the most frequently mutated kinases in human cancer. A PI3Kα-selective inhibitor may provide the opportunity to spare patients the side effects associated with broader inhibition of the class I PI3K family. Here, we describe our efforts to discover a PI3Kα-selective inhibitor by applying structure-based drug design (SBDD) and computational analysis. A novel series of compounds, exemplified by 2,2-difluoroethyl (3S)-3-{[2'-amino-5-fluoro-2-(morpholin-4-yl)-4,5'-bipyrimidin-6-yl]amino}-3-(hydroxymethyl)pyrrolidine-1-carboxylate (1) (PF-06843195), with high PI3Kα potency and unique PI3K isoform and mTOR selectivity were discovered. We describe here the details of the design and synthesis program that lead to the discovery of 1.