An engineered chimeric toxin that cleaves activated mutant and wild-type RAS inhibits tumor growth.
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ABSTRACT:
SUBMITTER: Vidimar V
PROVIDER: S-EPMC7382267 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:Oncogenic RAS mutant (RASMUT) proteins have been considered undruggable via conventional antibody regimens owing to the intracellular location restricting conventional-antibody accessibility. Here, we report a pan-RAS-targeting IgG antibody, inRas37, which directly targets the intracellularly activated form of various RASMUT subtypes after tumor cell-specific internalization into the cytosol to block the interactions with effector proteins, thereby suppressing the downstream signaling. Systemic administration of inRas37 exerted a potent antitumor activity in a subset of RASMUT tumor xenografts in mice, but little efficacy in RASMUT tumors with concurrent downstream PI3K mutations, which were overcome by combination with a PI3K inhibitor. The YAP1 protein was up-regulated as an adaptive resistance-inducing response to inRas37 in RASMUT-dependent colorectal tumors; accordingly, a combination of inRas37 with a YAP1 inhibitor manifested synergistic antitumor effects in vitro and in vivo. Our study offers a promising pan-RAS-targeting antibody and the corresponding therapeutic strategy against RASMUT tumors.
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Project description:Lung cancer is currently the most deadly malignancy in industrialized countries and accounts for 18% of all cancer-related deaths worldwide. Over 70% of patients with non-small cell lung cancer (NSCLC) are diagnosed at a late stage, with a 5-year survival below 10%. KRAS and the EGFR are frequently mutated in NSCLC and while targeted therapies for patients with EGFR mutations exist, oncogenic KRAS is thus far not druggable. KRAS activates multiple signalling pathways, including the PI3K/Akt pathway, the Raf-Mek-Erk pathway and the RalGDS/Ral pathway. Lung-specific expression of BrafV600E, the most prevalent BRAF mutation found in human tumors, results in Raf-Mek-Erk pathway activation and in the formation of benign adenomas that undergo widespread senescence in a Cre-activated Braf mouse model (Braf(CA)). However, oncogenic KRAS expression in mice induces adenocarcinomas, suggesting additional KRAS-activated pathways cooperate with sustained RAF-MEK-ERK signalling to bypass the oncogene-induced senescence proliferation arrest. To determine which KRAS effectors were responsible for tumor progression, we created four effector domain mutants (S35, G37, E38 and C40) in G12V-activated KRAS and expressed these alone or with BrafV600E in mouse lungs... The S35 and E38 mutants bind to Raf proteins but not PI3K or RalGDS; the G37 mutant binds to RalGDS and not Raf or PI3K and the C40 mutant is specific to PI3K. We designed lentiviral vectors to code for Cre recombinase along with KRAS mutants (V12, V12/S35, V12/G37, V12/E38 or V12/C40) or EGFP as a negative control.. These lentiviruses were used to infect Braf(CA) and wild-type mice. Surprisingly there was a significant decrease in tumor number and penetrance with each KRAS effector domain mutant relative to controls, suggesting that KRAS directly activates effectors with tumor suppressive functions.
| S-EPMC3904846 | biostudies-literature
Project description:Pancreatic cancer is one of the most lethal human diseases, with an all-stage 5-year survival rate below 5%. To date, no effective and specific therapy is available for this disease. Mutations in KRAS are frequently reported in pancreatic and many other cancers; thus, KRAS is an attractive therapeutic target. Our objective was to specifically eliminate mutant KRAS and induce cell death of tumors expressing this mutant protein. We thus constructed several chimeric proteins by connecting the C-terminal domains of several adaptor proteins of E3 ubiquitin ligases such as CBL, CHIP, E6AP, and VHL, as well as VIF encoded by human immunodeficiency virus type 1 (HIV-1), to the Ras binding domain (RBD) of Raf. Although all of these chimeric proteins caused the degradation of mutant KRAS and the death of KRAS-mutant-tumor cell lines, the RBD-VIF with a protein transduction domain (PTD), named PTD-RBD-VIF, had the strongest tumor-killing effect. Intraperitoneally administered recombinant PTD-RBD-VIF potently inhibited the growth of xenografted KRAS-mutant pancreatic cancer cells. Our findings indicate that recombinant PTD-RBD-VIF, a chimeric protein with a combined cellular-viral origin, could be further developed for the treatment of various tumors harboring mutant or over-activated KRAS, especially for cases presenting with pancreatic cancer recurrence after surgery.
| S-EPMC5190097 | biostudies-literature
Project description:BackgroundmiRNAs play crucial role in the progression of K-Ras-mutated nonsmall cell lung cancer (NSCLC). However, most studies have focused on miRNAs that target K-Ras. Here, we investigated miRNAs regulated by mutant K-Ras and their functions.MethodsmiRNAs regulated by mutant K-Ras were screened using miRNA arrays. miR-199b expression levels were measured by qRT-PCR. The protein expression levels were measured using Western blot and immunohistochemistry. The effects of miR-199b on NSCLC were examined both in vitro and in vivo by overexpressing or inhibiting miR-199b. DNA methylation was measured by bisulfite sequencing.ResultsAn inverse correlation was observed between K-Ras mutation status and miR-199b levels in NSCLC specimens and cell lines. The inhibition of miR-199b stimulated NSCLC growth and metastasis, while restoration of miR-199b suppressed K-Ras mutation-driven lung tumorigenesis as well as K-Ras-mutated NSCLC growth and metastasis. miR-199b inactivated ERK and Akt pathways by targeting K-Ras, KSR2, PIK3R1, Akt1, and Rheb1. Furthermore, we determined that mutant K-Ras inhibits miR-199b expression by increasing miR-199b promoter methylation.ConclusionOur findings suggest that mutant K-Ras plays an oncogenic role through downregulating miR-199b in NSCLC and that overexpression of miR-199b is a novel strategy for the treatment of K-Ras-mutated NSCLC.
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Project description:The axe-txe operon encodes a toxin-antitoxin (TA) pair, Axe-Txe, that was initially identified on the multidrug-resistance plasmid pRUM in Enterococcus faecium. In Escherichia coli, expression of the Txe toxin is known to inhibit cell growth, and co-expression of the antitoxin, Axe, counteracts the toxic effect of Txe. Here, we report the nucleotide sequence of pS177, a 39 kb multidrug-resistant plasmid isolated from vancomycin-resistant Ent. faecium, which harbours the axe-txe operon and the vanA gene cluster. RT-PCR analysis revealed that the axe-txe transcript is produced by strain S177 as well as by other vancomycin-resistant enteroccoci. Moreover, we determine the mechanism by which the Txe protein exerts its toxic activity. Txe inhibits protein synthesis in E. coli without affecting DNA or RNA synthesis, and inhibits protein synthesis in a cell-free system. Using in vivo primer extension analysis, we demonstrate that Txe preferentially cleaves single-stranded mRNA at the first base after an AUG start codon. We conclude that Txe is an endoribonuclease which cleaves mRNA and inhibits protein synthesis.
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Project description:Mutations in KRAS are prevalent in human cancers and universally predictive of resistance to anticancer therapeutics. Although it is widely accepted that acquisition of an activating mutation endows RAS genes with functional autonomy, recent studies suggest that the wild-type forms of Ras may contribute to mutant Ras-driven tumorigenesis. Here, we show that downregulation of wild-type H-Ras or N-Ras in mutant K-Ras cancer cells leads to hyperactivation of the Erk/p90RSK and PI3K/Akt pathways and, consequently, the phosphorylation of Chk1 at an inhibitory site, Ser 280. The resulting inhibition of ATR/Chk1 signaling abrogates the activation of the G2 DNA damage checkpoint and confers specific sensitization of mutant K-Ras cancer cells to DNA damage chemotherapeutic agents in vitro and in vivo.
| S-EPMC4063560 | biostudies-literature
Project description:Type II toxin-antitoxin systems contain a toxin protein, which mediates diverse interactions within the bacterial cell when it is not bound by its cognate antitoxin protein. These toxins provide a rich source of evolutionarily-conserved tertiary folds that mediate diverse catalytic reactions. These properties make toxins of interest in biotechnology applications, and studies of the catalytic mechanisms continue to provide surprises. In the current work, our studies on a YoeB family toxin from Agrobacterium tumefaciens have revealed a conserved ribosome-independent non-specific nuclease activity. We have quantified the RNA and DNA cleavage activity, revealing they have essentially equivalent dose-dependence while differing in requirements for divalent cations and pH sensitivity. The DNA cleavage activity is as a nickase for any topology of double-stranded DNA, as well as cleaving single-stranded DNA. AtYoeB is able to bind to double-stranded DNA with mid-micromolar affinity. Comparison of the ribosome-dependent and -independent reactions demonstrates an approximate tenfold efficiency imparted by the ribosome. This demonstrates YoeB toxins can act as non-specific nucleases, cleaving both RNA and DNA, in the absence of being bound within the ribosome.
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Project description:Ras oncogenes (Hras, Kras and Nras) are important drivers of carcinogenesis. However, tumors with Ras mutations often show loss of the corresponding wild-type (WT) allele, suggesting that proto-oncogenic forms of Ras can function as a suppressor of carcinogenesis. In vitro studies also suggest that WT Ras proteins can suppress the tumorigenic properties of alternate mutant Ras family members, but in vivo evidence for these heterologous interactions is lacking. We have investigated the genetic interactions between different combinations of mutant and WT Ras alleles in vivo using carcinogen-induced lung and skin carcinogenesis in mice with targeted deletion of different Ras family members. The major suppressor effect of WT Kras is observed only in mutant Kras-driven lung carcinogenesis, where loss of one Kras allele led to increased tumor number and size. Deletion of one Hras allele dramatically reduced the number of skin papillomas with Hras mutations, consistent with Hras as the major target of mutation in these tumors. However, skin carcinoma numbers were very similar, suggesting that WT Hras functions as a suppressor of progression from papillomas to invasive squamous carcinomas. In the skin, the Kras proto-oncogene functions cooperatively with mutant Hras to promote papilloma development, although the effect is relatively small. In contrast, the Hras proto-oncogene attenuated the activity of mutant Kras in lung carcinogenesis. Interestingly, loss of Nras increased the number of mutant Kras-induced lung tumors, but decreased the number of mutant Hras-induced skin papillomas. These results show that the strongest suppressor effects of WT Ras are only seen in the context of mutation of the cognate Ras protein, and only relatively weak effects are detected on tumor development induced by mutations in alternative family members. The data also underscore the complex and context-dependent nature of interactions between proto-oncogenic and oncogenic forms of different Ras family members during tumor development.
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Project description:The ability to selectively and directly target activated Ras would provide immense utility for treatment of the numerous cancers that are driven by oncogenic Ras mutations. Patients with disorders driven by overactivated wild-type Ras proteins, such as type 1 neurofibromatosis, might also benefit from progress made in that context. Activated Ras is an extremely challenging direct drug target due to the inherent difficulties in disrupting the protein:protein interactions that underlie its activation and function. Major investments have been made to target Ras through indirect routes. Inhibition of farnesyl transferase to block Ras maturation has failed in large clinical trials. Likely reasons for this disappointing outcome include the significant and underappreciated differences in the isoforms of Ras. It is still plausible that inhibition of farnesyl transferase will prove effective for disease that is driven by activated H-Ras. The principal current focus of drugs entering clinic trial is inhibition of pathways downstream of activated Ras, for example, trametinib, a first-in-class MEK inhibitor. The complexity of signaling that is driven by activated Ras indicates that effective inhibition of oncogenic transduction through this approach will be difficult, with resistance being likely to emerge through switch to parallel pathways. Durable disease responses will probably require combinatorial block of several downstream targets.
| S-EPMC3833460 | biostudies-literature
Project description:The Ras-extracellular signal-regulated kinase pathway is critical for controlling cell proliferation, and its aberrant activation drives the growth of various cancers. Because many pathogens produce toxins that inhibit Ras activity, efforts to develop effective Ras inhibitors to treat cancer could be informed by studies of Ras inhibition by pathogens. Vibrio vulnificus causes fatal infections in a manner that depends on multifunctional autoprocessing repeats-in-toxin, a toxin that releases bacterial effector domains into host cells. One such domain is the Ras/Rap1-specific endopeptidase (RRSP), which site-specifically cleaves the Switch I domain of the small GTPases Ras and Rap1. We solved the crystal structure of RRSP and found that its backbone shares a structural fold with the EreA/ChaN-like superfamily of enzymes. Unlike other proteases in this family, RRSP is not a metalloprotease. Through nuclear magnetic resonance analysis and nucleotide exchange assays, we determined that the processing of KRAS by RRSP did not release any fragments or cause KRAS to dissociate from its bound nucleotide but instead only locally affected its structure. However, this structural alteration of KRAS was sufficient to disable guanine nucleotide exchange factor-mediated nucleotide exchange and prevent KRAS from binding to RAF. Thus, RRSP is a bacterial effector that represents a previously unrecognized class of protease that disconnects Ras from its signaling network while inducing limited structural disturbance in its target.
| S-EPMC6309442 | biostudies-literature