Wild-Type H- and N-Ras Promote Mutant K-Ras-Driven Tumorigenesis by Modulating the DNA Damage Response

Grabocka, Elda; Pylayeva-Gupta, Yuliya; Ma, Jones; Lubkov, Veronica; Yemanaberhan, Eyoel; Taylor, Laura; Jeng, Hao Hsuan; Bar–Sagi, Dafna

doi:10.1016/j.ccr.2014.01.005

Cited by 130 publications

(122 citation statements)

References 49 publications

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“…This conjecture could explain a long standing observation that wild-type Kras2 can suppress mutant KRas-driven lung carcinogens in mice (36). Nevertheless, the interplays between wild-type and mutant Ras appear to be much more complex, as exemplified by a recent study (37).…”

Section: Discussionmentioning

confidence: 92%

Ras-GTP dimers activate the Mitogen-Activated Protein Kinase (MAPK) pathway

Nan

Tamgüney

Collisson

et al. 2015

Proc. Natl. Acad. Sci. U.S.A.

250

252

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Rat sarcoma (Ras) GTPases regulate cell proliferation and survival through effector pathways including Raf-MAPK, and are the most frequently mutated genes in human cancer. Although it is well established that Ras activity requires binding to both GTP and the membrane, details of how Ras operates on the cell membrane to activate its effectors remain elusive. Efforts to target mutant Ras in human cancers to therapeutic benefit have also been largely unsuccessful. Here we show that Ras-GTP forms dimers to activate MAPK. We used quantitative photoactivated localization microscopy (PALM) to analyze the nanoscale spatial organization of PAmCherry1-tagged KRas 4B (hereafter referred to KRas) on the cell membrane under various signaling conditions. We found that at endogenous expression levels KRas forms dimers, and KRas G12D , a mutant that constitutively binds GTP, activates MAPK. Overexpression of KRas leads to formation of higher order Ras nanoclusters. Conversely, at lower expression levels, KRas G12D is monomeric and activates MAPK only when artificially dimerized. Moreover, dimerization and signaling of KRas are both dependent on an intact CAAX (C, cysteine; A, aliphatic; X, any amino acid) motif that is also known to mediate membrane localization. These results reveal a new, dimerization-dependent signaling mechanism of Ras, and suggest Ras dimers as a potential therapeutic target in mutant Ras-driven tumors.Ras dimer | MAPK signaling | cancer | single molecule imaging | superresolution microscopy T he canonical rat sarcoma (Ras) GTPase family members H-, N-, and K-ras are frequently activated in human cancers (1-4) by recurrent point mutations at codons 12, 13, or 61. These mutations result in constitutive binding of Ras to GTP due to impaired GTP hydrolysis (5). Despite nearly identical G-domains, mammalian Ras isoforms serve nonredundant biological roles and exhibit different mutational spectra in human cancers (1,4,6). These functional differences are in part attributed to distinctions in the membranetethering motif at the C-terminal of Ras known as the hyper-variable region [HVR, which includes the "CAAX" (C, cysteine; A, aliphatic; X, any amino acid) motif] (6, 7). Although mechanisms regulating Ras-GTP levels in cells have been examined extensively, details of how Ras organizes and operates on the cell membrane have been elusive. Efforts on targeting mutant Ras to therapeutic benefits in human cancers by inhibiting membrane localization or GTP binding have not been successful, leaving mutant Ras an intractable drug target (8). Hence, identification of new mechanisms that regulate Ras oncogenesis is crucial to combating mutant Ras-driven cancers.Recent studies using immuno electron microscopy (immuno-EM) have implicated a previously unappreciated spatial mechanism in regulating the biological functions of Ras. In particular, Ras proteins were found to form 5-to 8-membered nanoclusters that serve as signaling scaffolds for recruiting and activating downstream effectors such as Raf and PI3K on the cell membr...

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Section: Discussionmentioning

confidence: 92%

Ras-GTP dimers activate the Mitogen-Activated Protein Kinase (MAPK) pathway

Nan

Tamgüney

Collisson

et al. 2015

Proc. Natl. Acad. Sci. U.S.A.

250

252

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“…Recent studies demonstrated that wild-type Ras proteins contribute to tumorigenesis in Ras-mutant cancer cells (21)(22)(23)(24). However, the oncogenic roles of Ras in Ras wild-type cancers have yet to be established.…”

Section: Discussionmentioning

confidence: 99%

Ras–MEK Signaling Mediates a Critical Chk1-Dependent DNA Damage Response in Cancer Cells

Lee¹,

Cao²,

Pham

et al. 2017

Molecular Cancer Therapeutics

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Cancer cell line profiling to identify previously unrecognized kinase dependencies revealed a novel nonmutational dependency on the DNA damage response checkpoint kinase Chk1. Although Chk1 is a promising therapeutic target in p53-deficient cancers, we found that Ras-MEK signaling engages Chk1 in a subset of osteosarcoma, ovarian, and breast cancer cells to enable their survival upon DNA damage, irrespective of p53 mutation status. Mechanistically, Ras-MEK signaling drives Chk1 expression and promotes cancer cell growth that produces genotoxic stress that requires Chk1 to mediate a response to the consequent DNA damage. Reciprocally, Chk1 engages a negative feedback loop to prevent hyperactivation of Ras-MEK signaling, thereby limiting DNA damage. Furthermore, exogenous DNA damage promotes Chk1 dependency, and pharmacologic Chk1 inhibition combined with genotoxic chemotherapy potentiates a DNA damage response and tumor cell killing. These findings reveal a mechanism-based diagnostic strategy to identify cancer patients that may benefit from Chk1-targeted therapy.

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“…In agreement with this finding, we now show that the converse is true, namely, that converting rare codons into common codons in the nononcogenic Kras allele, which can elevate protein expression, reduces tumor burden when the opposing allele is oncogenic. WT RAS proteins can also promote tumor growth through a variety of mechanisms, including enhancing signaling (37-39), suppressing apoptosis (40,41), and modulating a DNA damage response (42). Since these tumor-promoting effects were elucidated in established cancer cell lines that are typically resistant to oncogene-induced stress, it stands to reason that the nononcogenic Kras ex3op allele similarly promotes tumorigenesis in more malignant cells, altering codon bias has a biological impact on the function of an endogenous mammalian gene in vivo.…”

Section: Discussionmentioning

confidence: 99%