bims-pimaco Biomed News
on PI3K and MAPK signalling in colorectal cancer
Issue of 2021‒02‒07
sixteen papers selected by
Lucas B. Zeiger
Beatson Institute for Cancer Research

  1. J Mol Biol. 2021 Feb 01. pii: S0022-2836(21)00032-2. [Epub ahead of print] 166838
      Phosphatidylinositol-3-kinases (PI3Ks) are lipid kinases that phosphorylate phosphatidylinositol 4,5-bisphosphate to generate a key lipid second messenger, phosphatidylinositol 3,4,5-bisphosphate. PI3Kα and PI3Kγ require activation by RAS proteins to stimulate signaling pathways that control cellular growth, differentiation, motility and survival. Intriguingly, RAS binding to PI3K isoforms likely differ, as RAS mutations have been identified that discriminate between PI3Kα and PI3Kγ, consistent with low sequence homology (23%) between their RAS binding domains (RBDs). As disruption of the RAS/PI3Kα interaction reduces tumor growth in mice with RAS- and epidermal growth factor receptor driven skin and lung cancers, compounds that interfere with this key interaction may prove useful as anti-cancer agents. However, a structure of PI3Kα bound to RAS is lacking, limiting drug discovery efforts. Expression of full-length PI3K isoforms in insect cells has resulted in low yield and variable activity, limiting biophysical and structural studies of RAS/PI3K interactions. This led us to generate the first RBDs from PI3Kα and PI3Kγ that can be expressed at high yield in bacteria and bind to RAS with similar affinity to full-length PI3K. We also solved a 2.31 Å X-ray crystal structure of the PI3Kα-RBD, which aligns well to full-length PI3Kα. Structural differences between the PI3Kα and PI3Kγ RBDs are consistent with differences in thermal stability and may underly differential RAS recognition and RAS-mediated PI3K activation. These high expression, functional PI3K RBDs will aid in interrogating RAS interactions and could aid in identifying inhibitors of this key interaction.
    Keywords:  Phosphoinositide 3-kinase (PI3K); RAS; cancer; cell signaling; protein/protein interactions
  2. Biochem Soc Trans. 2021 Feb 05. pii: BST20200964. [Epub ahead of print]
      Cancer stem cells (CSC) may be the most relevant and elusive cancer cell population, as they have the exquisite ability to seed new tumors. It is plausible, that highly mutated cancer genes, such as KRAS, are functionally associated with processes contributing to the emergence of stemness traits. In this review, we will summarize the evidence for a stemness driving activity of oncogenic Ras. This activity appears to differ by Ras isoform, with the highly mutated KRAS having a particularly profound impact. Next to established stemness pathways such as Wnt and Hedgehog (Hh), the precise, cell cycle dependent orchestration of the MAPK-pathway appears to relay Ras activation in this context. We will examine how non-canonical activities of K-Ras4B (hereafter K-Ras) could be enabled by its trafficking chaperones calmodulin and PDE6D/PDEδ. Both dynamically localize to the cellular machinery that is intimately linked to cell fate decisions, such as the primary cilium and the centrosome. Thus, it can be speculated that oncogenic K-Ras disrupts fundamental polarized signaling and asymmetric apportioning processes that are necessary during cell differentiation.
    Keywords:  KRAS; cancer stem cells; centrosomes; cilia; trafficking
  3. Curr Oncol Rep. 2021 Feb 06. 23(2): 23
      PURPOSE OF REVIEW: Mitogen-activated protein kinase (MAPK) kinase (MEK) is an integral component of the RAS signaling pathway, one of the most frequently mutated pathways in cancer biology. MEK inhibitors were initially developed to directly target oncogenic signaling, but are recognized to have pleiotropic effects on both tumor cells and lymphocytes. Here, we review the preclinical and clinical evidence that MEK inhibition is immunomodulatory and discuss the potential rationale for combining MEK inhibitors with systemic immunotherapies.RECENT FINDINGS: MEK inhibition may modulate the tumor microenvironment (TME) through direct effects on both tumor cells and immune cells. Despite encouraging evidence that MEK inhibition can reprogram the tumor microenvironment (TME) and augment anti-tumor immunity regardless of KRAS/BRAF status, recent clinical outcome studies combining MEK inhibition with systemic immunotherapy have yielded mixed results. The combination of MEK inhibitors plus systemic immunotherapies has been tolerable, but has thus far failed to demonstrate clear evidence of synergistic clinical activity. These results underscore the need to understand the appropriate therapeutic context for this combination. MEK inhibitors have the potential to inhibit oncogenic signaling and reprogram the tumor immune microenvironment, representing an attractive therapy to combine with systemic immunotherapies. Ongoing preclinical and clinical studies will further clarify the immunomodulatory effects of MEK inhibitors to inform the design of rational therapeutic combinations.
    Keywords:  Immunotherapy; MAPK; MEK; PD-1; PD-L1; RAS
  4. Adv Exp Med Biol. 2021 ;1275 357-382
      While protein tyrosine kinases (PTKs) play an initiative role in growth factor-mediated cellular processes, protein tyrosine phosphatases (PTPs) negatively regulates these processes, acting as tumor suppressors. Besides selective tyrosine dephosphorylation of PTKs via PTPs may affect oncogenic pathways during carcinogenesis. The PTP family contains a group of dual-specificity phosphatases (DUSPs) that regulate the activity of Mitogen-activated protein kinases (MAPKs), which are key effectors in the control of cell growth, proliferation and survival. Abnormal MAPK signaling is critical for initiation and progression stages of carcinogenesis. Since depletion of DUSP-MAPK phosphatases (MKPs) can reduce tumorigenicity, altering MAPK signaling by DUSP-MKP inhibitors could be a novel strategy in anti-cancer therapy. Moreover, Cdc25A is, a DUSP and a key regulator of the cell cycle, promotes cell cycle progression by dephosphorylating and activating cyclin-dependent kinases (CDK). Cdc25A-CDK pathway is a novel mechanism in carcinogenesis. Besides the mammalian target of rapamycin (mTOR) kinase inhibitors or mammalian target of rapamycin complex 1 (mTORC1) inhibition in combination with the dual phosphatidylinositol 3 kinase (PI3K)/mTOR or AKT kinase inhibitors are more effective in inhibiting the phosphorylation of eukaryotic translation initiation factor 4E-binding protein 1 (4E-BP1) and cap-dependent translation. Dual targeting of the Akt and mTOR signaling pathways regulates cellular growth, proliferation and survival. Like the Cdc2-like kinases (CLK), dual-specific tyrosine phosphorylation-regulated kinases (DYRKs) are essential for the regulation of cell fate. The crosstalk between dual-specific phosphatases and dual- specific protein kinases is a novel drug target for anti-cancer therapy. Therefore, the focus of this chapter involves protein kinase modules, critical biochemical checkpoints of cancer therapy and the synergistic effects of protein kinases and anti-cancer molecules.
    Keywords:  AKT; CDK; Carcinogenesis; Cdc25A; DUSP; Kinases; MAPK; PI3K; Phosphatases; mTOR
  5. J Biol Chem. 2020 Jan 03. pii: S0021-9258(17)49565-2. [Epub ahead of print]295(1): 263-274
      Mammalian target of rapamycin complex 1 (mTORC1) promotes cell growth and proliferation in response to nutrients and growth factors. Amino acids induce lysosomal translocation of mTORC1 via the Rag GTPases. Growth factors activate Ras homolog enriched in brain (Rheb), which in turn activates mTORC1 at the lysosome. Amino acids and growth factors also induce the phospholipase D (PLD)-phosphatidic acid (PA) pathway, required for mTORC1 signaling through mechanisms that are not fully understood. Here, using human and murine cell lines, along with immunofluorescence, confocal microscopy, endocytosis, PLD activity, and cell viability assays, we show that exogenously supplied PA vesicles deliver mTORC1 to the lysosome in the absence of amino acids, Rag GTPases, growth factors, and Rheb. Of note, pharmacological or genetic inhibition of endogenous PLD prevented mTORC1 lysosomal translocation. We observed that precancerous cells with constitutive Rheb activation through loss of tuberous sclerosis complex subunit 2 (TSC2) exploit the PLD-PA pathway and thereby sustain mTORC1 activation at the lysosome in the absence of amino acids. Our findings indicate that sequential inputs from amino acids and growth factors trigger PA production required for mTORC1 translocation and activation at the lysosome.
    Keywords:  amino acid; cancer biology; cancer therapy; growth factor; lysosome; mTOR complex (mTORC); phosphatidic acid; phospholipase D; phospholipid vesicle
  6. Front Oncol. 2020 ;10 608722
      Serum and glucocorticoid-induced protein kinase 1 (SGK1) is a member of the "AGC" subfamily of protein kinases, which shares structural and functional similarities with the AKT family of kinases and displays serine/threonine kinase activity. Aberrant expression of SGK1 has profound cellular consequences and is closely correlated with human cancer. SGK1 is considered a canonical factor affecting the expression and signal transduction of multiple genes involved in the genesis and development of many human cancers. Abnormal expression of SGK1 has been found in tissue and may hopefully become a useful indicator of cancer progression. In addition, SGK1 acts as a prognostic factor for cancer patient survival. This review systematically summarizes and discusses the role of SGK1 as a diagnostic and prognostic biomarker of diverse cancer types; focuses on its essential roles and functions in tumorigenesis, cancer cell proliferation, apoptosis, invasion, metastasis, autophagy, metabolism, and therapy resistance and in the tumor microenvironment; and finally summarizes the current understanding of the regulatory mechanisms of SGK1 at the molecular level. Taken together, this evidence highlights the crucial role of SGK1 in tumorigenesis and cancer progression, revealing why it has emerged as a potential target for cancer therapy.
    Keywords:  autophagy; metabolism; serum and glucocorticoid-induced protein kinase 1; therapeutic resistance; tumor microenvironment
  7. Clin Cancer Res. 2021 Feb 05. pii: clincanres.4699.2020. [Epub ahead of print]
      BACKGROUND: The routine use of liquid biopsy is not recommended for the choice of initial treatment of patients with metastatic colorectal cancer (mCRC).EXPERIMENTAL DESIGN: We included patients with left-sided, RAS/BRAF wild-type, HER2-negative and microsatellite stable mCRC, treated with upfront FOLFOX-panitumumab in the Valentino study. We performed amplicon-based genomic profiling of 14 genes in baseline plasma samples and compared these data with tumor tissue ultra-deep sequencing results. Specific gene mutations in ctDNA and their clonality were associated with PFS, OS and radiological dynamics.
    RESULTS: Ten and 15 out of 120 patients had a mutation of RAS and PIK3CA in ctDNA, with a positive concordance with tissue deep-sequencing of only 31.3% and 47.1%, respectively. Presence of RAS or PIK3CA mutations in baseline ctDNA was associated with worse median PFS (8.0 vs. 12.8 months; HR=2.49, 95%CI: 1.28-4.81, p=0.007; 8.5 vs 12.9 months; HR=2.86, 95%CI: 1.63-5.04, p<0.001) and median OS (17.1 vs. 36.5 months; HR=2.26, 95%CI: 1.03-4.96, p=0.042; 21.1 vs 38.9 months; HR=2.18, 95%CI: 1.16-4.07, p=0.015). RAS mutations in ctDNA were associated with worse RECIST response, early tumor shrinkage and depth of response, while PIK3CA mutations were not. Patients with higher levels of RAS/PIK3CA variant allele fraction (VAF) in ctDNA had the worst outcomes (VAF {greater than or equal to}5% vs all-wild-type: median PFS: 7.7 vs 13.1 months, HR: 4.02, 95%CI: 2.03-7.95, p<0.001; median OS: 18.8 vs 38.9 months, HR: 4.07, 95%CI: 2.04-8.12, p<0.001).
    CONCLUSION: Baseline ctDNA profiling may add value to tumor tissue testing to refine the molecular hyperselection of mCRC patients for upfront anti-EGFR-based strategies.
  8. Biochem Soc Trans. 2021 Feb 05. pii: BST20190730. [Epub ahead of print]
      Cells have evolved highly intertwined kinase networks to finely tune cellular homeostasis to the environment. The network converging on the mechanistic target of rapamycin (MTOR) kinase constitutes a central hub that integrates metabolic signals and adapts cellular metabolism and functions to nutritional changes and stress. Feedforward and feedback loops, crosstalks and a plethora of modulators finely balance MTOR-driven anabolic and catabolic processes. This complexity renders it difficult - if not impossible - to intuitively decipher signaling dynamics and network topology. Over the last two decades, systems approaches have emerged as powerful tools to simulate signaling network dynamics and responses. In this review, we discuss the contribution of systems studies to the discovery of novel edges and modulators in the MTOR network in healthy cells and in disease.
    Keywords:  amino acids; computational models; mechanistic target of rapamycin; protein kinase B; signaling; systems biology
  9. Biochem Soc Trans. 2021 Feb 05. pii: BST20200507. [Epub ahead of print]
      The RAF-MEK-ERK mitogen-activated protein kinase (MAPK) cascade is aberrantly activated in a diverse set of human cancers and the RASopathy group of genetic developmental disorders. This protein kinase cascade is one of the most intensely studied cellular signaling networks and has been frequently targeted by the pharmaceutical industry, with more than 30 inhibitors either approved or under clinical evaluation. The ERK-MAPK cascade was originally depicted as a serial and linear, unidirectional pathway that relays extracellular signals, such as mitogenic stimuli, through the cytoplasm to the nucleus. However, we now appreciate that this three-tiered protein kinase cascade is a central core of a complex network with dynamic signaling inputs and outputs and autoregulatory loops. Despite our considerable advances in understanding the ERK-MAPK network, the ability of cancer cells to adapt to the inhibition of key nodes reveals a level of complexity that remains to be fully understood. In this review, we summarize important developments in our understanding of the ERK-MAPK network and identify unresolved issues for ongoing and future study.
    Keywords:  PDAC; RAS GTPase; extracellular signal-regulated kinases; mitogen-activated protein kinases
  10. J Cell Sci. 2021 Feb 04. pii: jcs.246090. [Epub ahead of print]
      The class I phosphoinositide 3-kinase (PI3K) catalytic subunits p110α and p110β are ubiquitously expressed but differently targeted in tumours. In cancer, PIK3CB (encoding p110β) is seldom mutated compared to PIK3CA (encoding p110α) but can contribute to tumorigenesis in certain PTEN-deficient tumours. The underlying molecular mechanisms are however unclear. We have previously reported that p110β is highly expressed in endometrial cancer (EC) cell lines and at the mRNA levels in primary patient tumours. Here, we show that p110β protein levels are high in both the cytoplasmic and nuclear compartments in EC cells. Moreover, high nuclear/cytoplasmic staining ratio were detected in high grade primary tumours. High levels of phosphatidylinositol (3,4,5)-trisphosphate (PtdIns(3,4,5)P 3) were measured in the nucleus of EC cells and pharmacological and genetic approaches showed that its production was partly dependent upon p110β activity. Using immunofluorescence staining, p110β and PtdIns(3,4,5)P 3 were localised in the nucleolus, which correlated with high levels of 47S pre-rRNA. p110β inhibition led to a decrease in 47S rRNA levels and cell proliferation. In conclusion, these results present a nucleolar role for p110β that may contribute to tumorigenesis in EC.
    Keywords:  Endometrial cancer; Nucleolus; PIK3CB; Phosphoinositide 3-kinase; RDNA transcription; p110β
  11. Data Brief. 2021 Feb;34 106719
      Dataset contains results of multiple parallel calculations using the tugHall simulator. Output data of simulations are variant allele frequencies for four genes (APC, KRAS, TP53, and PIK3CA) related to colorectal cancer. During each simulation tugHall stochastically reproduces Darwinian evolution for cancer cells and calculates clonal heterogeneity. The probabilities of stochastic processes depend on a correspondence matrix between genome information and cancer hallmarks. As a result, tugHall records variant allele frequencies for the final stage of evolution. The number of trials is several million to get rich statistics of stochastic processes. These data can be used for approximate Bayesian computation and other statistical methods to get personalized coefficients for patients with colorectal cancer. The procedure of usage data is explained in our paper [Bioinformatics, 36, 11 (2020) 3597] in which the part of these data was used.
    Keywords:  Approximate Bayesian computation; Colorectal cancer; Dataset of tugHall simulator; Evolution of cancer cells; Genome and cancer hallmarks relationship
  12. J Natl Compr Canc Netw. 2021 Feb 02. pii: jnccn20180. [Epub ahead of print] 1-12
      BACKGROUND: This study sought to assess microsatellite and KRAS status, prevalence, and impact on outcome in stage IV colorectal cancer (CRC).MATERIALS AND METHODS: The 2010 to 2016 US National Cancer Database was queried for adult patients with stage IV CRC. Prevalence of microsatellite status (microsatellite instability-high [MSI-H] or microsatellite stable [MSS]) and KRAS status (KRAS mutation or wild-type) of the primary CRC was assessed. Overall survival (OS) was evaluated using multivariable Cox proportional hazards models in patients with complete data on both microsatellite and KRAS status and information on follow-up.
    RESULTS: Information on microsatellite and KRAS status was available for 10,844 and 25,712 patients, respectively, and OS data were available for 5,904 patients. The overall prevalence of MSI-H status and KRAS mutation was 3.1% and 42.4%, respectively. Prevalence of MSI-H ranged between 1.6% (rectosigmoid junction) and 5.2% (transverse colon), and between 34.7% (sigmoid colon) and 58.2% (cecum) for KRAS mutation. MSI-H rates were highest in East North Central US states (4.1%), and KRAS mutation rates were highest in West South Central US states (44.1%). Multivariable analyses revealed longer OS for patients with KRAS wild-type versus mutation status (hazard ratio [HR], 0.91; 95% CI, 0.85-0.97; P=.004), those with MSS versus MSI-H status (HR, 0.75; 95% CI, 0.62-0.9; P=.003), and those with left-sided versus right-sided CRC (multivariable HR, 0.65; 95% CI, 0.6-0.7; P<.001). The effect of KRAS mutation further varied with CRC site and microsatellite status (P=.002 for interaction).
    CONCLUSIONS: Depending on the primary site and US geography, stage IV CRC shows distinct mutational behavior. KRAS mutation, MSI-H, and primary CRC sidedness independently affect OS and interact with distinct prognostic profiles. Generically classifying adenocarcinomas at different sites as CRC might deprecate this diversity.
  13. Onco Targets Ther. 2021 ;14 699-710
      Introduction: Colorectal cancer (CRC) is a major cause of cancer-related mortality worldwide. Copines-1 (CPNE1) has been shown to be overexpressed in various cancers; however, the role of CPNE1 in CRC remains unknown. Therefore, it is of great importance to elucidate the role of CPNE1 in CRC and its underlying mechanism of action.Methods: CPNE1 expression in CRC tissues was measured by quantitative real-time PCR and immunohistochemical (IHC) staining. CPNE1 was knocked down (KD) or overexpressed using small inferring RNAs or lentiviral transduction in CRC cells. The proliferation, apoptosis, glycolysis, and mitochondrial respiration of CRC cells were assessed by cell counting kit-8, flow cytometry, and Xfe24 extracellular flux analyzer assays, respectively. The role of CPNE1 in tumor growth and chemoresistance was further confirmed in xenograft and patient-derived tumor xenograft models, respectively.
    Results: CPNE1 mRNA and protein were upregulated in CRC tissues. CPNE1 promoted proliferation, inhibited apoptosis, increased mitochondrial respiration, enhanced aerobic glycolysis by activating AKT signaling, upregulated glucose transporter 1 (GLUT1) and hexokinase 2 (HK2), and downregulated the production of cleaved Caspase-3 (c-Caspase 3). CPNE1 also contributed to chemoresistance in CRC cells. CPNE1 KD inhibited tumor growth and increased the sensitivity of tumors to oxaliplatin in vivo.
    Conclusion: CPNE1 promotes CRC progression by activating the AKT-GLUT1/HK2 cascade and enhances chemoresistance.
    Keywords:  aerobic glycolysis; colorectal cancer; copines-1; mitochondrial respiration
  14. Front Cell Dev Biol. 2020 ;8 641552
    Keywords:  AMPK; cell metabolism; mTOR; metformin; nucleus; post-translational modifications; rapamycin; transcriptional regulation
  15. FEBS Lett. 2021 Feb 04.
      The balance between phosphoinositides distributed at specific sites in the plasma membrane causes polarized actin polymerization. Oncogenic transformations affect this balance by regulating phosphoinositide 3-kinase (PI3K) and phosphatase and tensin homolog deleted on chromosome ten (PTEN), causing metastatic behavior in cancer cells. Here, we show that the PTEN tumor suppressor gene is required for epithelial cancer cell invasion. Loss of PTEN in Ras-transformed MDCK cells suppressed their migratory phenotype in collagen gel and invasion through Matrigel. Rescue experiments showed a requirement for the C2 domain-mediated membrane recruitment of PTEN, which is typically observed at the rear side of invading cancer cells. These findings support the role of PTEN in suppression of unwanted leading edges necessary for efficient migration of epithelial cancer cells.
    Keywords:  PI3K; PTEN; Ras; cancer cell invasion