bims-pimaco Biomed News
on PI3K and MAPK signalling in colorectal cancer
Issue of 2021‒08‒08
thirteen papers selected by
Lucas B. Zeiger
Beatson Institute for Cancer Research

  1. Hum Antibodies. 2021 Jul 23.
      INTRODUCTION: Metastatic or recurrent colorectal cancer (MRCRC) has a poor prognosis. The aim of the present meta-analysis was to assess the prevalence of different subtypes of KRAS mutation and BRAF mutation in metastatic CRC patients, and evaluate the relationship between the tumor sidedness and prevalence of KRAS and BRAF mutation.METHODS: We searched MEDLINE/PubMed, the Cochrane Library, and from January 2010 to July 2020. The data were extracted independently according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA). The statistical analysis was done using STATA and Meta-Disk 1.4 applications.
    RESULTS: Overall, 6699 colorectal cancer patients were included. KRAS and BRAF mutation was reported in 28% and 6% of patients, respectively. The overall prevalence of right primary and left primary metastatic CRC patients with mutated KRAS was 40% and 60%. However, the prevalence BRAF mutated right primary and left primary metastatic CRC patients was 37% and 63%. The overall HR was 2.38 for patients with metastatic CRC who had a mutated type of KRAS. Our study showed a mean overall survival of 35.4 month for KRAS mutant and a 10.12 month survival for BRAF mutant patients with metastatic colorectal cancer patients.
    CONCLUSION: The prevalence of KRAS and BRAF mutations varied significantly according to the location of the tumor. BRAF mutations are more commonly found in metastatic colorectal cancers on the right side. Liver was the most common site of metastases in patients with mutant KRAS and the mortality of patients with mutant KRAS was 2.3 times higher than the patients with wild types. These results help to better describe the population of mCRC patients and can have implications for improving and organizing anti-EGFR therapies. Further research is needed to assess differences in survival through mutation status and primary tumor location.
    Keywords:  BRAF mutation; KRAS mutation; colorectal cancer; metastatic
  2. Expert Opin Drug Metab Toxicol. 2021 Aug 04.
      Introduction: KRAS is the most frequently mutated oncogenic driver in pancreatic, lung and colon cancer. Recently, KRAS inhibitors in clinical use show promising activity but most responses are partial and drug resistance develops. The use of therapeutics in combination with KRAS inhibitors are expected to improve outcomes.Areas covered: This review describes the KRAS G12C mutation-specific inhibitors and the SOS1-targeting inhibitors that reduce the GTP- loading of wildtype and mutated KRAS. Both types of compounds reduce tumor cell proliferation in vitro and in vivo. The combinations of the various KRAS inhibitors with downstream signaling effectors, modulators of KRAS-associated metabolic alterations and chemotherapeutics are summarized.Expert opinion: The clinical potency of mutated KRAS-specific inhibitors needs to be improved by suitable drug combinations. Inhibition of downstream signaling cascades increases toxicity and other combinations exploited comprise G12C-directed inhibitors with SOS1 inhibitors, glucose/glutamine metabolic modulators, classical chemotherapeutics and others. The most suitable inhibitor combinations corroborated in preclinical development await clinical verification.
    Keywords:  Cancer; amg510; combination therapy; g12c; kras; mrtx849; sos1 inhibitor
  3. Mol Biol Rep. 2021 Aug 06.
      INTRODUCTION: Radiotherapy is one of the most common types of cancer treatment modalities. Radiation can affect both cancer and normal tissues, which limits the whole delivered dose. It is well documented that radiation activates phosphatidylinositol 3-kinase (PI3K) and AKT signaling pathway; hence, the inhibition of this pathway enhances the radiosensitivity of tumor cells. The mammalian target of rapamycin (mTOR) is a regulator that is involved in autophagy, cell growth, proliferation, and survival.CONCLUSION: The inhibition of mTOR as a downstream mediator of the PI3K/AKT signaling pathway represents a vital option for more effective cancer treatments. The combination of PI3K/AKT/mTOR inhibitors with radiation can increase the radiosensitivity of malignant cells to radiation by autophagy activation. Therefore, this review aims to discuss the impact of such inhibitors on the cell response to radiation.
    Keywords:  Inhibitor; PI3K/AKT; Radiation; Radiosensitivity; mTOR
  4. Cell Rep Med. 2021 Jul 20. 2(7): 100350
      Inhibition of the extracellular signal-regulated kinases ERK1 and ERK2 (ERK1/2) offers a promising therapeutic strategy in cancers harboring activated RAS/RAF/MEK/ERK signaling pathways. Here, we describe an orally bioavailable and selective ERK1/2 inhibitor, ASN007, currently in clinical development for the treatment of cancer. In preclinical studies, ASN007 shows strong antiproliferative activity in tumors harboring mutations in BRAF and RAS (KRAS, NRAS, and HRAS). ASN007 demonstrates activity in a BRAFV600E mutant melanoma tumor model that is resistant to BRAF and MEK inhibitors. The PI3K inhibitor copanlisib enhances the antiproliferative activity of ASN007 both in vitro and in vivo due to dual inhibition of RAS/MAPK and PI3K survival pathways. Our data provide a rationale for evaluating ASN007 in RAS/RAF-driven tumors as well as a mechanistic basis for combining ASN007 with PI3K inhibitors.
    Keywords:  ASN007; ERK; KRAS; PI3K; RAF/RAS-driven cancers; biomarker; combinational therapy; kinase inhibitor; lymphoma; solid tumors
  5. Cancer Biol Med. 2021 Aug 04. pii: j.issn.2095-3941.2020.0532. [Epub ahead of print]
      OBJECTIVE: Mutant KRAS, the principal isoform of RAS, plays a pivotal role in the oncogenesis of colorectal cancer by constitutively activating the RAF/MEK/ERK and PI3K/AKT pathways. Effective targeted therapies are urgently needed. We investigated whether rigosertib, a benzyl styryl sulfone RAS signaling disruptor, could selectively kill KRAS-mutant colorectal cancer cells.METHODS: CCK-8 was used to determine the cell viability. Patient-derived tumor and cancer cell xenograft models were used to detect the inhibitory efficacy of rigosertib. Flow cytometry was used to evaluate the apoptosis and cell cycle progression. Apoptosis and cell cycle arrest markers were detected by Western blot. DCFH-DA was used to determine the reactive oxygen species. Immunohistochemistry staining and Western blot were performed to characterize RAS signaling markers in colorectal cancer tissues and cells.
    RESULTS: Rigosertib (RGS) exhibited a cytotoxic effect against colorectal cancer cells, which was greater in KRAS-mutant cells. Furthermore, RGS induced mitotic arrest and oxidative stress-dependent apoptosis in KRAS-mutant DLD1 and HCT116 cells. Besides, RGS disrupted RAS signaling, and the inhibition of RAS/MEK/ERK was independent of cellular oxidative stress. Using patient-derived xenograft models, the response and tumor inhibition of RGS were significantly higher in the KRAS-mutant subgroup, while p-MEK, p-ERK, and p-AKT levels of RGS-treated tumors were significantly decreased. Finally, in a KRAS-mutant, chemotherapy-resistant patient-derived xenograft model, RGS showed a stronger therapeutic effect than the combination standard therapy involving fluoropyrimidine + oxaliplatin/irinotecan + bevacizumab.
    CONCLUSIONS: These data showed that targeting RAS signaling using RGS could be a therapeutic treatment for KRAS-mutant colorectal cancer patients.
    Keywords:  Colorectal cancer; KRAS mutation; RAS signaling; rigosertib; therapeutic effect
  6. Genes (Basel). 2021 Jul 19. pii: 1094. [Epub ahead of print]12(7):
      Ras proteins are essential mediators of a multitude of cellular processes, and its deregulation is frequently associated with cancer appearance, progression, and metastasis. Ras-driven cancers are usually aggressive and difficult to treat. Although the recent Food and Drug Administration (FDA) approval of the first Ras G12C inhibitor is an important milestone, only a small percentage of patients will benefit from it. A better understanding of the context in which Ras operates in different tumor types and the outcomes mediated by each effector pathway may help to identify additional strategies and targets to treat Ras-driven tumors. Evidence emerging in recent years suggests that both oncogenic Ras signaling in tumor cells and non-oncogenic Ras signaling in stromal cells play an essential role in cancer. PI3K is one of the main Ras effectors, regulating important cellular processes such as cell viability or resistance to therapy or angiogenesis upon oncogenic Ras activation. In this review, we will summarize recent advances in the understanding of Ras-dependent activation of PI3K both in physiological conditions and cancer, with a focus on how this signaling pathway contributes to the formation of a tumor stroma that promotes tumor cell proliferation, migration, and spread.
    Keywords:  PI3-Kinase; Ras oncogenes
  7. J Cancer. 2021 ;12(17): 5331-5337
      Background: The clinical significance of KRAS exon 3/4 mutations in colorectal cancer (CRC) remains unclear. We aimed to assess the prognostic value of KRAS exons 3 and 4 mutations to determine the necessity for their testing. Methods: KRAS mutations in exon 2/3/4 were evaluated in 1816 stage I-IV patients with colorectal adenocarcinoma. Results: The mutation rates of KRAS and KRAS exons 2, 3, and 4 were 49.0%, 43.0%, 1.9%, and 4.1%, respectively. Univariate survival analysis showed that patients with exon 3 mutation had worse overall survival (OS) compared to those with KRAS exon 2 mutation or wild-type KRAS (P = 0.044, and P = 0.001). Meanwhile, there was no difference in survival between patients with wild-type KRAS and with exon 4 mutation (P = 0.128). In multivariate analysis, KRAS mutations in exon 3 and 2 were both independent factors for worse OS (Exon 3, P = 0.032, HR = 1.861, 95% CI: 1.021-3.391; Exon 2, P = 0.049, HR = 1.298, 95% CI: 1.002-1.682). Among the patients with KRAS exon 2 mutations, those that had mutations in codon 13 had significantly worse prognosis than those with wild-type KRAS (P = 0.001) or KRAS codon 12 mutations (P = 0.003). Conclusions: In KRAS-mutated CRC, exon 3 mutations predict the worst prognosis, while exon 4 mutations predict the best prognosis. Among KRAS exon 2 mutated patients, codon 13 mutations predict worse prognosis than codon 12 mutations. Mutations of different KRAS exons should be analyzed separately.
    Keywords:   KRAS exon 4; KRAS exon 3; KRAS mutations; clinicopathologic features; colorectal cancer; prognosis
  8. Oncogene. 2021 Jul 31.
      Oncogenic mutations of KRAS are found in the most aggressive human tumors, including colorectal cancer. It has been suggested that oncogenic KRAS phosphorylation at Ser181 modulates its activity and favors cell transformation. Using nonphosphorylatable (S181A), phosphomimetic (S181D), and phospho-/dephosphorylatable (S181) oncogenic KRAS mutants, we analyzed the role of this phosphorylation to the maintenance of tumorigenic properties of colorectal cancer cells. Our data show that the presence of phospho-/dephosphorylatable oncogenic KRAS is required for preserving the epithelial organization of colorectal cancer cells in 3D cultures, and for supporting subcutaneous tumor growth in mice. Interestingly, gene expression differed according to the phosphorylation status of KRAS. In DLD-1 cells, CTNNA1 was only expressed in phospho-/dephosphorylatable oncogenic KRAS-expressing cells, correlating with cell polarization. Moreover, lack of oncogenic KRAS phosphorylation leads to changes in expression of genes related to cell invasion, such as SERPINE1, PRSS1,2,3, and NEO1, and expression of phosphomimetic oncogenic KRAS resulted in diminished expression of genes involved in enterocyte differentiation, such as HNF4G. Finally, the analysis, in a public data set of human colorectal cancer, of the gene expression signatures associated with phosphomimetic and nonphosphorylatable oncogenic KRAS suggests that this post-translational modification regulates tumor progression in patients.
  9. Biomolecules. 2021 Jul 07. pii: 996. [Epub ahead of print]11(7):
      Ras and Raf-kinase interact through the Ras-binding (RBD) and cysteine-rich domains (CRD) of Raf to signal through the mitogen-activated protein kinase pathway, yet the molecular mechanism leading to Raf activation has remained elusive. We present the 2.8 Å crystal structure of the HRas-CRaf-RBD_CRD complex showing the Ras-Raf interface as a continuous surface on Ras, as seen in the KRas-CRaf-RBD_CRD structure. In molecular dynamics simulations of a Ras dimer model formed through the α4-α5 interface, the CRD is dynamic and located between the two Ras protomers, poised for direct or allosteric modulation of functionally relevant regions of Ras and Raf. We propose a molecular model in which Ras binding is involved in the release of Raf autoinhibition while the Ras-Raf complex dimerizes to promote a platform for signal amplification, with Raf-CRD centrally located to impact regulation and function.
    Keywords:  HRas–CRaf-RBD_CRD crystal structure; MAPK; Raf; Raf cystein-rich domain (CRD); Ras; Ras dimerization; Ras–Raf-RBD_CRD dimer simulations; allosteric connections
  10. Nat Rev Cancer. 2021 Aug 02.
      Translational control of mRNAs during gene expression allows cells to promptly and dynamically adapt to a variety of stimuli, including in neoplasia in response to aberrant oncogenic signalling (for example, PI3K-AKT-mTOR, RAS-MAPK and MYC) and microenvironmental stress such as low oxygen and nutrient supply. Such translational rewiring allows rapid, specific changes in the cell proteome that shape specific cancer phenotypes to promote cancer onset, progression and resistance to anticancer therapies. In this Review, we illustrate the plasticity of mRNA translation. We first highlight the diverse mechanisms by which it is regulated, including by translation factors (for example, eukaryotic initiation factor 4F (eIF4F) and eIF2), RNA-binding proteins, tRNAs and ribosomal RNAs that are modulated in response to aberrant intracellular pathways or microenvironmental stress. We then describe how translational control can influence tumour behaviour by impacting on the phenotypic plasticity of cancer cells as well as on components of the tumour microenvironment. Finally, we highlight the role of mRNA translation in the cellular response to anticancer therapies and its promise as a key therapeutic target.
  11. Cancers (Basel). 2021 Jul 26. pii: 3757. [Epub ahead of print]13(15):
      Colorectal cancer remains among the cancers with the highest incidence, prevalence, and mortality worldwide. Although the development of targeted therapies against the EGFR and VEGFR membrane receptors has considerably improved survival in these patients, the appearance of resistance means that their success is still limited. Overactivation of several members of the Ras-GTPase family is one of the main actors in both tumour progression and the lack of response to cytotoxic and targeted therapies. This fact has led many resources to be devoted over the last decades to the development of targeted therapies against these proteins. However, they have not been as successful as expected in their move to the clinic so far. In this review, we will analyse the role of these Ras-GTPases in the emergence and development of colorectal cancer and their relationship with resistance to targeted therapies, as well as the status and new advances in the design of targeted therapies against these proteins and their possible clinical implications.
    Keywords:  EGFR targeted therapies; Ras-GTPases; colorectal cancer; drug resistance
  12. Mol Cell. 2021 Jul 28. pii: S1097-2765(21)00582-7. [Epub ahead of print]
      The Wnt/β-catenin pathway is a highly conserved, frequently mutated developmental and cancer pathway. Its output is defined mainly by β-catenin's phosphorylation- and ubiquitylation-dependent proteasomal degradation, initiated by the multi-protein β-catenin destruction complex. The precise mechanisms underlying destruction complex function have remained unknown, largely because of the lack of suitable in vitro systems. Here we describe the in vitro reconstitution of an active human β-catenin destruction complex from purified components, recapitulating complex assembly, β-catenin modification, and degradation. We reveal that AXIN1 polymerization and APC promote β-catenin capture, phosphorylation, and ubiquitylation. APC facilitates β-catenin's flux through the complex by limiting ubiquitylation processivity and directly interacts with the SCFβ-TrCP E3 ligase complex in a β-TrCP-dependent manner. Oncogenic APC truncation variants, although part of the complex, are functionally impaired. Nonetheless, even the most severely truncated APC variant promotes β-catenin recruitment. These findings exemplify the power of biochemical reconstitution to interrogate the molecular mechanisms of Wnt/β-catenin signaling.
    Keywords:  SCF(β-TrCP); Wnt/beta-catenin signalling; adenomatous polyposis coli (APC); axis inhibition protein (AXIN); beta-catenin destruction complex; biochemistry; casein kinase 1 (CK1); colorectal cancer; glycogen synthase kinase 3 (GSK3); ubiquitin
  13. Front Cell Dev Biol. 2021 ;9 685665
      Epidermal Growth Factor (EGF) has long been known for its role in promoting proliferation of intestinal epithelial cells. EGF is produced by epithelial niche cells at the base of crypts in vivo and is routinely added to the culture medium to support the growth of intestinal organoids ex vivo. The recent identification of diverse stromal cell populations that reside underneath intestinal crypts has enabled the characterization of key growth factor cues supplied by these cells. The nature of these signals and how they are delivered to drive intestinal epithelial development, daily homeostasis and tissue regeneration following injury are being investigated. It is clear that aside from EGF, other ligands of the family, including Neuregulin 1 (NRG1), have distinct roles in supporting the function of intestinal stem cells through the ErbB pathway.
    Keywords:  Epidermal Growth Factor; ErbB; intestinal stem cells; neuregulin 1; niche; organoids; signaling; tissue regeneration