bims-pimaco Biomed News
on PI3K and MAPK signalling in colorectal cancer
Issue of 2021‒01‒24
eight papers selected by
Lucas B. Zeiger
Beatson Institute for Cancer Research

  1. Proc Natl Acad Sci U S A. 2021 Jan 26. pii: e2003193118. [Epub ahead of print]118(4):
      We have shown previously that phosphorylation of Mdm2 by ATM and c-Abl regulates Mdm2-p53 signaling and alters the effects of DNA damage in mice, including bone marrow failure and tumorigenesis induced by ionizing radiation. Here, we examine the physiological effects of Mdm2 phosphorylation by Akt, another DNA damage effector kinase. Surprisingly, Akt phosphorylation of Mdm2 does not alter the p53-mediated effects of ionizing radiation in cells or mice but regulates the p53 response to oxidative stress. Akt phosphorylation of Mdm2 serine residue 183 increases nuclear Mdm2 stability, decreases p53 levels, and prevents senescence in primary cells exposed to reactive oxidative species (ROS). Using multiple mouse models of ROS-induced cancer, we show that Mdm2 phosphorylation by Akt reduces senescence to promote KrasG12D-driven lung cancers and carcinogen-induced papilloma and hepatocellular carcinomas. Collectively, we document a unique physiologic role for Akt-Mdm2-p53 signaling in regulating cell growth and tumorigenesis in response to oxidative stress.
    Keywords:  Akt; Mdm2; Tp53; senescence; tumorigenesis
  2. Bioimpacts. 2021 ;11(1): 5-14
      Introduction: Early-activated RAS/RAF mutation status is a key molecular finding in colorectal cancer (CRC), while these mutations have been proposed as predictive and prognostic biomarkers. The present study has been designed as a longitudinal study to evaluate and summarize the different genotypes of metastatic CRC (mCRC), and assessing any association with the disease prognosis and clinicopathological characteristics. This study was performed in two main referral hospitals of Tabriz University of Medical Sciences, over three years (2016-2018). Methods: Mutations were detected by Idylla tests of KRAS/NRAS/BRAF among a total of 173 mCRCs, using surgically-resected specimens or biopsied samples. To evaluate the factors associated with overall survival (OS) and prognosis, the Cox proportional hazards model was used in two steps to estimate the outcome measures (hazard ratio, or HR) with a 95% confidence interval (CI). Results: The nominal 1 to 5-year OS rates were 78%, 65%, 55%, 46%, and 42%, respectively. KRAS mutations in codon 12 was an independent significant prognostic factor, as the patients with codon 12 mutations had a significantly lower OS (P Log-rank=0.049) and a higher hazard of mortality (HR=2.30; 95% CI: 0.95-5.58; P =0.066). Also, the mCRC patients with liver metastasis (HR=2.49; 95% CI: 1.49-12.52; P =0.002) and tumors of the distal colon (HR=3.36; 95% CI: 1.07-10.49; P =0.037) had a significantly worse prognosis. Conclusion: KRAS mutation in codon 12 was an independent significant poor prognostic factor, and patients with liver metastasis had a significantly worse prognosis. Routinely performing specific oncogenic tests may help improve the patients' prognosis and life expectancy.
    Keywords:  Colorectal cancer; Hazard ratio; KRAS; Oncogene; Overall survival
  3. Oncologist. 2021 Jan 19.
      BACKGROUND: RAS short variant mutations (SV) in colorectal cancer (CRC) are associated with lack of benefit from EGFR monoclonal antibody (EGFRmAb). However, the clinical implications for RAS amplification (RASa) as a biomarker for anti-EGFR therapy in CRC remain ill-defined.METHODS: Genomic analysis was performed using the Foundation Medicine (FM) comprehensive genomic profiling (CGP) database (GDB) of 37,233 CRC cases. Clinical outcomes were assessed using 2 independent cohorts (1) The City of Hope (COH): 338 metastatic CRC (mCRC) patients, (2) Flatiron Health (FH)-FM real-world clinico-GDB (CGDB): 3,904 mCRC patients.
    RESULTS: RASa was detected in 1.6% (614/37,233) of primarily mCRC. RASa 6-9 (n=241, 39%), 10-19 (n=165, 27%) and ≥20 copy (n=209, 34%) subsets had co-RAS SV/BRAF V600E in 63%/3%, 31%/0.6% and 4.8%/0% of cases, respectively. COH cohort: 6 patients with RASa (13-54 copies) received EGFRmAb; 4/6 had progressive disease, 2 had stable disease; median time to treatment discontinuation (TTD) was 2.5 months. CGDB EGFRmAb-treated patients: RASa (n=9) had median TTD of 4.7 months and overall survival (OS) of 11.4 months; RAS SV (n=101) had median TTD and OS of 5.3 and 9.4 months; RAS/BRAF wild-type (n=608) had median TTD and OS of 7.6 and 13.7 months.
    CONCLUSIONS: Patients with RASa without RAS mutations (1.1% of mCRC) may have poor outcomes on EGFRmAb, although numbers herein were small, and interpretation is confounded by combination chemotherapy. Larger independent studies are warranted to determine if RASa, including degree of amplification, may act similarly to RAS mutation as a resistance mechanism to EGFRmAb therapies.
    IMPLICATIONS FOR PRACTICE: Genomic data suggests that RAS amplification occurs as the sole RAS/RAF alteration in in >1% of CRC, and degree of amplification inversely correlates with co-occuring MAPK pathway alterations. Preliminary clinical evidence suggests that RAS amplification may function similarly to RAS mutation as a negative predictor of benefit from anti-EGFR therapies in colorectal cancer. More clinical data is needed, and comprehensive genomic profiling including detection of RAS amplification should be utilized in trial design to inform therapy selection.
    Keywords:  CRC; EGFR antibody; RAS amplification; copy number; genomic profiling
  4. Oncologist. 2021 Jan 19.
      LESSONS LEARNED: Antitumor activity was observed in the study population. Dose modifications of cabozantinib improve long-term tolerability. Biomarkers are needed to identify patient populations most likely to benefit. Further study of cabozantinib with or without panitumumab in patients with metastatic colorectal cancer is warranted.BACKGROUND: The epidermal growth factor receptor (EGFR) antibody panitumumab is active in patients with RAS wild-type (WT) metastatic colorectal cancer (mCRC), but nearly all patients experience resistance. MET amplification is a driver of panitumumab resistance. Cabozantinib is an inhibitor of multiple kinases, including vascular endothelial growth factor receptor 2 (VEGFR2) and c-MET, and may delay or reverse anti-EGFR resistance.
    METHODS: In this phase Ib clinical trial, we established maximum tolerated dose (MTD) and recommended phase II dose (RP2D) of cabozantinib and panitumumab. We then treated an expansion cohort to further describe the tolerability and clinical activity of the RP2D. Eligibility included patients with KRAS WT mCRC (later amended to include only RAS WT mCRC) who had received prior treatment with a fluoropyrimidine, oxaliplatin, irinotecan, and bevacizumab.
    CONCLUSION: The combination of cabozantinib and panitumumab has activity. Dose reductions of cabozantinib improve tolerability.
    Keywords:  Cabozantinib; Colorectal cancer; Panitumumab; RAS
  5. Nat Commun. 2021 01 21. 12(1): 508
      Thousands of human small and alternative open reading frames (smORFs and alt-ORFs, respectively) have recently been annotated. Many alt-ORFs are co-encoded with canonical proteins in multicistronic configurations, but few of their functions are known. Here, we report the detection of alt-RPL36, a protein co-encoded with human RPL36. Alt-RPL36 partially localizes to the endoplasmic reticulum, where it interacts with TMEM24, which transports the phosphatidylinositol 4,5-bisphosphate (PI(4,5)P2) precursor phosphatidylinositol from the endoplasmic reticulum to the plasma membrane. Knock-out of alt-RPL36 increases plasma membrane PI(4,5)P2 levels, upregulates PI3K-AKT-mTOR signaling, and increases cell size. Alt-RPL36 contains four phosphoserine residues, point mutations of which abolish interaction with TMEM24 and, consequently, alt-RPL36 effects on PI3K signaling and cell size. These results implicate alt-RPL36 as an upstream regulator of PI3K-AKT-mTOR signaling. More broadly, the RPL36 transcript encodes two sequence-independent polypeptides that co-regulate translation via different molecular mechanisms, expanding our knowledge of multicistronic human gene functions.
  6. Proc Natl Acad Sci U S A. 2021 Jan 26. pii: e2022120118. [Epub ahead of print]118(4):
      In mammalian cells, nutrients and growth factors signal through an array of upstream proteins to regulate the mTORC1 growth control pathway. Because the full complement of these proteins has not been systematically identified, we developed a FACS-based CRISPR-Cas9 genetic screening strategy to pinpoint genes that regulate mTORC1 activity. Along with almost all known positive components of the mTORC1 pathway, we identified many genes that impact mTORC1 activity, including DCAF7, CSNK2B, SRSF2, IRS4, CCDC43, and HSD17B10 Using the genome-wide screening data, we generated a focused sublibrary containing single guide RNAs (sgRNAs) targeting hundreds of genes and carried out epistasis screens in cells lacking nutrient- and stress-responsive mTORC1 modulators, including GATOR1, AMPK, GCN2, and ATF4. From these data, we pinpointed mitochondrial function as a particularly important input into mTORC1 signaling. While it is well appreciated that mitochondria signal to mTORC1, the mechanisms are not completely clear. We find that the kinases AMPK and HRI signal, with varying kinetics, mitochondrial distress to mTORC1, and that HRI acts through the ATF4-dependent up-regulation of both Sestrin2 and Redd1. Loss of both AMPK and HRI is sufficient to render mTORC1 signaling largely resistant to mitochondrial dysfunction induced by the ATP synthase inhibitor oligomycin as well as the electron transport chain inhibitors piericidin and antimycin. Taken together, our data reveal a catalog of genes that impact the mTORC1 pathway and clarify the multifaceted ways in which mTORC1 senses mitochondrial dysfunction.
    Keywords:  CRISPR-Cas9 screen; mTORC1; mitochondria
  7. J Biol Chem. 2021 Jan 19. pii: S0021-9258(21)00083-1. [Epub ahead of print] 100314
      Ras genes are among the most frequently mutated oncogenes in human malignancies. To date, there are no successful anti-cancer drugs in the clinic that target Ras proteins or their pathways. Therefore, it is imperative to identify and characterize new components that regulate Ras activity or mediates its downstream signaling. To this end, we used a combination of affinity-pulldown and mass spectrometry to search for proteins that are physically associated with KRas. One of the top hits was Radil, a gene product with a Ras-association (RA) domain. Radil is known to be a downstream effector of Rap1, inhibiting RhoA signaling to regulate cell adhesion and migration. We demonstrate that Radil interacted with all three isoforms of Ras including HRas, NRas, and KRas, although it exhibited the strongest interaction with KRas. Moreover, Radil interacts with GTP-bound Ras more efficiently, suggesting a possibility that Radil may be involved in Ras activation. Supporting this, ectopic expression of Radil led to transient activation of MEK and ERK; Radil knockdown resulted in weakened activation of Ras downstream signaling components, which was coupled with decreased cell proliferation and invasion, and reduced expression of mesenchymal cell markers. Moreover, Radil knockdown greatly reduced the number of adhesion foci and depolymerized actin filaments, molecular processes that facilitate cancer cell migration. Taken together, our current studies strongly suggest that Radil is an important player for regulating Ras signaling, cell adhesion, and the epithelial-mesenchymal transition, and may provide new directions for Ras-related anti-cancer drug development.
    Keywords:  KRas; Radil; cell adhesion; cell invasion; epithelial-mesenchymal-transition
  8. Asian J Surg. 2021 Jan 16. pii: S1015-9584(21)00013-0. [Epub ahead of print]
      BACKGROUND: Recent studies have reported that KRAS mutational status is correlated with ERCC1 expression level. The purpose of this study was to determine the clinical significance of the KRAS mutation and ERCC1 overexpression status as predictive factors for resistance against oxaliplatin-based treatment.METHODS: We retrospectively analyzed clinicopathologic features, KRAS mutation status, and ERCC1 overexpression status in 386 patients with colorectal cancer (CRC) who underwent curative-intent surgery. Of these patients, 84 were administered the FOLFOX regimen as a first-line or adjuvant treatment. Disease-free survival and overall survival in groups separated by KRAS and ERCC1 statuses were analyzed.
    RESULTS: Wild-type KRAS and ERCC1 overexpression were observed in 25.5% of all patients. Among the 84 patients who were treated with the FOLFOX regimen, 73 patients were evaluated for KRAS and ERCC1 status. There were no significant differences in disease-free survival or overall survival in groups separated by KRAS mutation and ERCC1 expression status. Subgroup analysis of patients with wild-type KRAS showed that overall survival in the ERCC1 overexpression group was lower than that of patients in the ERCC1 underexpression group (p = 0.029); however, no significant difference was found in the mutant KRAS patient group (p = 0.671).
    CONCLUSIONS: Our results suggest that CRC with wild-type KRAS and ERCC1 overexpression might be associated with oxaliplatin resistance. When considering oxaliplatin-based chemotherapy, the status of both KRAS mutation and ERCC1 overexpression should be evaluated.
    Keywords:  Colorectal neoplasm; ERCC1; KRAS; Oxaliplatin; Resistance