bims-pimaco 2021-03-14 papers

on PI3K and MAPK signalling in colorectal cancer

Issue of 2021–03–14
nine papers selected by
Lucas B. Zeiger, CRUK Scotland Institute, Beatson Institute for Cancer Research

An ARF GTPase module promoting invasion and metastasis through regulating phosphoinositide metabolism.
mTORC1 couples cyst(e)ine availability with GPX4 protein synthesis and ferroptosis regulation.
Signaling pathways in intestinal homeostasis and colorectal cancer: KRAS at centre stage.
Influence of BRAF and PIK3CA mutations on the efficacy of FOLFIRI plus bevacizumab or cetuximab as first-line therapy in patients with RAS wild-type metastatic colorectal carcinoma and <3 baseline circulating tumour cells: the randomised phase II VISNÚ-2 study.
SK4 oncochannels regulate calcium entry and promote cell migration in KRAS-mutated colorectal cancer.
The Multi-Level Mechanism of Action of a Pan-Ras Inhibitor Explains its Antiproliferative Activity on Cetuximab-Resistant Cancer Cells.
Genomic alterations in PIK3CA-mutated breast cancer result in mTORC1 activation and limit sensitivity to PI3Kα inhibitors.
KRAS and BRAF mutations in Iranian colorectal cancer patients: A systematic review and meta-analysis.
Zn2+ influx activates ERK and Akt signaling pathways.

Nat Commun. 2021 Mar 12. 12(1): 1623

An ARF GTPase module promoting invasion and metastasis through regulating phosphoinositide metabolism.

Marisa Nacke, Emma Sandilands, Konstantina Nikolatou, Álvaro Román-Fernández, Susan Mason, Rachana Patel, Sergio Lilla, Tamas Yelland, Laura C A Galbraith, Eva C Freckmann, Lynn McGarry, Jennifer P Morton, Emma Shanks, Hing Y Leung, Elke Markert, Shehab Ismail, Sara Zanivan, Karen Blyth, David M Bryant.

The signalling pathways underpinning cell growth and invasion use overlapping components, yet how mutually exclusive cellular responses occur is unclear. Here, we report development of 3-Dimensional culture analyses to separately quantify growth and invasion. We identify that alternate variants of IQSEC1, an ARF GTPase Exchange Factor, act as switches to promote invasion over growth by controlling phosphoinositide metabolism. All IQSEC1 variants activate ARF5- and ARF6-dependent PIP5-kinase to promote PI(3,4,5)P3-AKT signalling and growth. In contrast, select pro-invasive IQSEC1 variants promote PI(3,4,5)P3 production to form invasion-driving protrusions. Inhibition of IQSEC1 attenuates invasion in vitro and metastasis in vivo. Induction of pro-invasive IQSEC1 variants and elevated IQSEC1 expression occurs in a number of tumour types and is associated with higher-grade metastatic cancer, activation of PI(3,4,5)P3 signalling, and predicts long-term poor outcome across multiple cancers. IQSEC1-regulated phosphoinositide metabolism therefore is a switch to induce invasion over growth in response to the same external signal. Targeting IQSEC1 as the central regulator of this switch may represent a therapeutic vulnerability to stop metastasis.

DOI: https://doi.org/10.1038/s41467-021-21847-4
Nat Commun. 2021 03 11. 12(1): 1589

mTORC1 couples cyst(e)ine availability with GPX4 protein synthesis and ferroptosis regulation.

Yilei Zhang, Robert V Swanda, Litong Nie, Xiaoguang Liu, Chao Wang, Hyemin Lee, Guang Lei, Chao Mao, Pranavi Koppula, Weijie Cheng, Jie Zhang, Zhenna Xiao, Li Zhuang, Bingliang Fang, Junjie Chen, Shu-Bing Qian, Boyi Gan.

Glutathione peroxidase 4 (GPX4) utilizes glutathione (GSH) to detoxify lipid peroxidation and plays an essential role in inhibiting ferroptosis. As a selenoprotein, GPX4 protein synthesis is highly inefficient and energetically costly. How cells coordinate GPX4 synthesis with nutrient availability remains unclear. In this study, we perform integrated proteomic and functional analyses to reveal that SLC7A11-mediated cystine uptake promotes not only GSH synthesis, but also GPX4 protein synthesis. Mechanistically, we find that cyst(e)ine activates mechanistic/mammalian target of rapamycin complex 1 (mTORC1) and promotes GPX4 protein synthesis at least partly through the Rag-mTORC1-4EBP signaling axis. We show that pharmacologic inhibition of mTORC1 decreases GPX4 protein levels, sensitizes cancer cells to ferroptosis, and synergizes with ferroptosis inducers to suppress patient-derived xenograft tumor growth in vivo. Together, our results reveal a regulatory mechanism to coordinate GPX4 protein synthesis with cyst(e)ine availability and suggest using combinatorial therapy of mTORC1 inhibitors and ferroptosis inducers in cancer treatment.

DOI: https://doi.org/10.1038/s41467-021-21841-w
Cell Commun Signal. 2021 Mar 10. 19(1): 31

Signaling pathways in intestinal homeostasis and colorectal cancer: KRAS at centre stage.

Camille Ternet, Christina Kiel.

  The intestinal epithelium acts as a physical barrier that separates the intestinal microbiota from the host and is critical for preserving intestinal homeostasis. The barrier is formed by tightly linked intestinal epithelial cells (IECs) (i.e. enterocytes, goblet cells, neuroendocrine cells, tuft cells, Paneth cells, and M cells), which constantly self-renew and shed. IECs also communicate with microbiota, coordinate innate and adaptive effector cell functions. In this review, we summarize the signaling pathways contributing to intestinal cell fates and homeostasis functions. We focus especially on intestinal stem cell proliferation, cell junction formation, remodelling, hypoxia, the impact of intestinal microbiota, the immune system, inflammation, and metabolism. Recognizing the critical role of KRAS mutants in colorectal cancer, we highlight the connections of KRAS signaling pathways in coordinating these functions. Furthermore, we review the impact of KRAS colorectal cancer mutants on pathway rewiring associated with disruption and dysfunction of the normal intestinal homeostasis. Given that KRAS is still considered undruggable and the development of treatments that directly target KRAS are unlikely, we discuss the suitability of targeting pathways downstream of KRAS as well as alterations of cell extrinsic/microenvironmental factors as possible targets for modulating signaling pathways in colorectal cancer. Video Abstract.

Keywords:  Colorectal cancer; Hypoxia; Inflammation; Intestinal stem cells; KRAS; MAPK pathway; Metabolic reprogramming; Microenvironment; Reactive oxygen species; Small GTPases

DOI:  https://doi.org/10.1186/s12964-021-00712-3
ESMO Open. 2021 Mar 09. pii: S2059-7029(21)00018-1. [Epub ahead of print]6(2): 100062

Influence of BRAF and PIK3CA mutations on the efficacy of FOLFIRI plus bevacizumab or cetuximab as first-line therapy in patients with RAS wild-type metastatic colorectal carcinoma and <3 baseline circulating tumour cells: the randomised phase II VISNÚ-2 study.

Spanish Cooperative Group for the Treatment of Digestive Tumours (TTD)

   BACKGROUND: We explored the influence of BRAF and PIK3CA mutational status on the efficacy of bevacizumab or cetuximab plus 5-fluorouracil/leucovorin and irinotecan (FOLFIRI) as first-line therapy in patients with RAS wild-type metastatic colorectal cancer (mCRC).
PATIENTS AND METHODS: VISNÚ-2 was a multicentre, randomised, phase II study. Patients with RAS wild-type mCRC and <3 circulating tumour cells/7.5 ml blood were stratified by BRAF/PIK3CA status (wild-type versus mutated) and number of affected organs (1 versus >1), and allocated to bevacizumab (5 mg/kg every 2 weeks) or cetuximab (400 mg/m2 then 250 mg/m2 weekly) plus FOLFIRI [irinotecan 180 mg/m2, leucovorin 400 mg/m2, 5-fluorouracil 400 mg/m2 (bolus) then 2400 mg/m2 (46-h continuous infusion) every 2 weeks]. The primary endpoint was progression-free survival (PFS). All analyses were exploratory.
RESULTS: Two hundred and forty patients with BRAF/PIK3CA wild-type (n = 196) or BRAF- and/or PIK3CA-mutated tumours (n = 44) were enrolled. Median PFS was 12.7 and 8.8 months in patients with BRAF/PIK3CA wild-type and BRAF/PIK3CA-mutated tumours, respectively [hazard ratio (HR) = 1.22; 95% confidence interval (CI) 0.80-1.85; P = 0.3602]. In the BRAF- and/or PIK3CA-mutated cohort, median PFS was 2.8, 8.8 and 15.0 months in patients with BRAF/PI3KCA-mutated (n = 8), BRAF-mutated/PI3KCA wild-type (n = 16) and BRAF wild-type/PI3KCA-mutated (n = 20) tumours, respectively (P = 0.0002). PFS was similar with bevacizumab plus FOLFIRI versus cetuximab plus FOLFIRI in BRAF/PIK3CA wild-type (HR = 0.99; 95% CI 0.67-1.45; P = 0.9486) and BRAF/PIK3CA-mutated tumours (HR = 1.11; 95% CI 0.53-2.35; P = 0.7820). The most common grade 3/4 treatment-related adverse events were neutropenia, diarrhoea and asthenia in both treatment groups.
CONCLUSIONS: BRAF/PIK3CA status influences outcomes in patients with RAS wild-type mCRC but does not appear to assist with the selection of first-line targeted therapy.

Keywords:  BRAF; PIK3CA; RAS; colorectal cancer; targeted therapy

DOI:  https://doi.org/10.1016/j.esmoop.2021.100062
Cell Calcium. 2021 Feb 25. pii: S0143-4160(21)00038-5. [Epub ahead of print]96 102384

SK4 oncochannels regulate calcium entry and promote cell migration in KRAS-mutated colorectal cancer.

Sajida Ibrahim, Justine Chaigne, Hassan Dakik, Yann Fourbon, Laetitia Corset, Thierry Lecomte, William Raoul, Maxime Guéguinou.

   BACKGROUND: Colorectal cancer (CRC) metastases are the main cause of CRC mortality. Intracellular Ca2+ regulates cell migration and invasion, key factors for metastases. Ca2+ also activates Ca2+-dependent potassium channels which in turn affect Ca2+ driving force. We have previously reported that the expression of the Ca2+ activated potassium channel KCNN4 (SK4) is higher in CRC primary tumors compared to normal tissues. Here, we aimed to investigate the role of SK4 in the physiology of CRC.
RESULTS: SK4 protein expression is enhanced in CRC tissues compared to normal colon tissues, with a higher level of KCNN4 in CRC patients with KRAS mutations. At the cellular level, we found that SK4 regulates the membrane potential of HCT116 cells. We also found that its inhibition reduced store operated Ca2+ entry (SOCE) and constitutive Ca2+ entry (CCE), while reducing cell migration. We also found that the activity of SK4 is linked to resistance pathways such as KRAS mutation and the expression of NRF2 and HIF-1α. In addition, the pharmacological inhibition of SK4 reduced intracellular reactive oxygen species (ROS) production, NRF2 expression and HIF1α stabilization.
CONCLUSION: Our results suggest that SK4 contributes to colorectal cancer cell migration and invasion by modulating both Ca2+ entry and ROS regulation. Therefore, SK4 could be a potential target to reduce metastasis in KRAS-mutated CRC.

Keywords:  Calcium signaling; Colorectal cancer; KCa3.1; KRAS; Migration; SK4

DOI:  https://doi.org/10.1016/j.ceca.2021.102384
Front Mol Biosci. 2021 ;8 625979

The Multi-Level Mechanism of Action of a Pan-Ras Inhibitor Explains its Antiproliferative Activity on Cetuximab-Resistant Cancer Cells.

Renata Tisi, Michela Spinelli, Alessandro Palmioli, Cristina Airoldi, Paolo Cazzaniga, Daniela Besozzi, Marco S Nobile, Elisa Mazzoleni, Simone Arnhold, Luca De Gioia, Rita Grandori, Francesco Peri, Marco Vanoni, Elena Sacco.

  Ras oncoproteins play a crucial role in the onset, maintenance, and progression of the most common and deadly human cancers. Despite extensive research efforts, only a few mutant-specific Ras inhibitors have been reported. We show that cmp4-previously identified as a water-soluble Ras inhibitor- targets multiple steps in the activation and downstream signaling of different Ras mutants and isoforms. Binding of this pan-Ras inhibitor to an extended Switch II pocket on HRas and KRas proteins induces a conformational change that down-regulates intrinsic and GEF-mediated nucleotide dissociation and exchange and effector binding. A mathematical model of the Ras activation cycle predicts that the inhibitor severely reduces the proliferation of different Ras-driven cancer cells, effectively cooperating with Cetuximab to reduce proliferation even of Cetuximab-resistant cancer cell lines. Experimental data confirm the model prediction, indicating that the pan-Ras inhibitor is an appropriate candidate for medicinal chemistry efforts tailored at improving its currently unsatisfactory affinity.

Keywords:  Raf1 binding; RasG12V; RasG13D; anti-cancer agent; cetuximab; exchange factor; intrinsic nucleotide dissociation and exchange; mathematical modeling & simulation

DOI:  https://doi.org/10.3389/fmolb.2021.625979
Cancer Res. 2021 Mar 08. pii: canres.3232.2020. [Epub ahead of print]

Genomic alterations in PIK3CA-mutated breast cancer result in mTORC1 activation and limit sensitivity to PI3Kα inhibitors.

Yanyan Cai, Guotai Xu, Fan Wu, Flavia Michelini, Carmen Chan, Xuan Qu, Pier Selenica, Erik Ladewig, Pau Castel, Yuanming Cheng, Alison Zhao, Komal Jhaveri, Eneda Toska, Marta Jimenez, Alexandra Jacquet Jacquet, Alicia Tran-Dien, Fabrice Andre, Sarat Chandarlapaty, Jorge S Reis-Filho, Pedram Razavi, Maurizio Scaltriti.

PI3Kα inhibitors have shown clinical activity in PIK3CA-mutated estrogen receptor-positive (ER+) breast cancer patients. Using whole genome CRISPR/Cas9 sgRNA knockout screens, we identified and validated several negative regulators of mTORC1 whose loss confers resistance to PI3Kα inhibition. Among the top candidates were TSC1, TSC2, TBC1D7, AKT1S1, STK11, MARK2, PDE7A, DEPDC5, NPRL2, NPRL3, C12orf66, SZT2 and ITFG2. Loss of these genes invariably results in sustained mTOR signaling under pharmacological inhibition of the PI3K-AKT pathway. Moreover, resistance could be prevented or overcome by mTOR inhibition, confirming the causative role of sustained mTOR activity in limiting the sensitivity to PI3Kα inhibition. Cumulatively, genomic alterations affecting these genes are identified in about 15% of PIK3CA-mutated breast tumors and appear to be mutually exclusive. This study improves our understanding of the role of mTOR signaling restoration in leading to resistance to PI3Kα inhibition and proposes therapeutic strategies to prevent or revert this resistance.

DOI: https://doi.org/10.1158/0008-5472.CAN-20-3232
Caspian J Intern Med. 2020 ;11(4): 355-369

KRAS and BRAF mutations in Iranian colorectal cancer patients: A systematic review and meta-analysis.

Abolfazl Yari, Asiyeh Afzali, Mostafa Aalipour, Mehran Nakheai, Mohammad Javad Zahedi.

   Background: Mutations in the EGFR signaling pathway play an important role in the development of colorectal cancer (CRC). Mutations in these genes, like KRAS and BRAF, affect the treatment strategies and associated with poor prognosis and relative resistance to anti-EGFR therapies. Our aim was to conduct a systematic and meta-analysis on all studies that have been conducted on the prevalence of these gene mutations in Iranian CRC patients.
Methods: Four science citation index databases (MEDLINE, EMBASE, Web of Science and Cochrane library) and local databases were searched up to March 2018 with related keywords. Two reviewers independently screened and extracted the data. Quality of all included studies was assessed using an adapted checklist from STROBE. A random-effect model was used to calculate the total prevalence of KRAS and BRAF mutations in CRC subjects by the event rate (ER). Meta-regression was utilized to explore heterogeneity causes.
Results: In total, from 573 records, 23 eligible studies (2662 patients) were included for data extraction and analysis. In 18 of 23 included studies, the prevalence of KRAS mutations was 33.9% (95% CI=30.1-37.9) with I2=65.17 (p<0.001). The occurrence of KRAS mutations in codon 12 and 13 was 76.9% (95% CI = 70.4-82.3%) with I2=84.88 (p<0.001) and 23.5% (95% CI=17.9-30.3) with I2=85.85 (p<0.001), respectively. In 9 of 23 studies, the BRAF mutation rate was 3.2% (95% CI=0.003-13.6) with I2=88.61 (p<0.001).
Conclusion: The prevalence of these mutations in CRC patients shows a significant difference in the different regions of Iran, which is probably due to environmental and racial factors.

Keywords:  BRAF; CRC; Colorectal cancer; Iran; KRAS; Mutation

DOI:  https://doi.org/10.22088/cjim.11.4.355
Proc Natl Acad Sci U S A. 2021 Mar 16. pii: e2015786118. [Epub ahead of print]118(11):

Zn2+ influx activates ERK and Akt signaling pathways.

Kelsie J Anson, Giulia A Corbet, Amy E Palmer.

  Zinc (Zn2+) is an essential metal in biology, and its bioavailability is highly regulated. Many cell types exhibit fluctuations in Zn2+ that appear to play an important role in cellular function. However, the detailed molecular mechanisms by which Zn2+ dynamics influence cell physiology remain enigmatic. Here, we use a combination of fluorescent biosensors and cell perturbations to define how changes in intracellular Zn2+ impact kinase signaling pathways. By simultaneously monitoring Zn2+ dynamics and kinase activity in individual cells, we quantify changes in labile Zn2+ and directly correlate changes in Zn2+ with ERK and Akt activity. Under our experimental conditions, Zn2+ fluctuations are not toxic and do not activate stress-dependent kinase signaling. We demonstrate that while Zn2+ can nonspecifically inhibit phosphatases leading to sustained kinase activation, ERK and Akt are predominantly activated via upstream signaling and through a common node via Ras. We provide a framework for quantification of Zn2+ fluctuations and correlate these fluctuations with signaling events in single cells to shed light on the role that Zn2+ dynamics play in healthy cell signaling.

Keywords:  Akt; ERK; Ras; kinase signaling; zinc

DOI:  https://doi.org/10.1073/pnas.2015786118