KSR induces RAS-independent MAPK pathway activation and modulates the efficacy of KRAS inhibitors.

The kinase suppressor of rat sarcoma (RAS) proteins (KSR1 and KSR2) have long been considered as scaffolding proteins required for optimal mitogen-activated protein kinase (MAPK) pathway signalling. However, recent evidence suggests that they play a more complex role within this pathway. Here, we demonstrate that ectopic expression of KSR1 or KSR2 is sufficient to activate the MAPK pathway and to induce cell proliferation in the absence of RAS proteins. In contrast, the ectopic expression of KSR proteins is not sufficient to induce cell proliferation in the absence of either rapidly accelerated fibrosarcoma (RAF) or MAPK-ERK kinase proteins, indicating that they act upstream of RAF. Indeed, KSR1 requires dimerization with at least one member of the RAF family to stimulate proliferation, an event that results in the translocation of the heterodimerized RAF protein to the cell membrane. Mutations in the conserved aspartic acid-phenylalanine-glycine motif of KSR1 that affect ATP binding impair the induction of cell proliferation. We also show that increased expression levels of KSR1 decrease the responsiveness to the KRASG12C inhibitor sotorasib in human cancer cell lines, thus suggesting that increased levels of expression of KSR may make tumour cells less dependent on KRAS oncogenic signalling.We thank M. San Roman and R. Villar for technical assistance. This work was supported by grants from the European Research Council (ERC-AG/695566, THERACAN), the Spanish Ministry of Science, Innovation and Universities (RTI2018-094664-B-I00 and RTC2017-6576-1), the Autonomous Community of Madrid (B2017/BMD-3884 iLUNG-CM), the CRIS Cancer Foundation and the Asociacion Espanola contra el Cancer (AECC) (GC166173694BARB). MB is a recipient of an Endowed Chair from the AXA Research Fund. GP has been supported by a fellowship from the Programa de Atraccion de Talento of the Autonomous Community of Madrid. SGA is a recipient of a postdoctoral fellowship from the AECC. OB is a recipient of a fellowship from the Formacion de Personal Investigador (FPI) program of the Spanish Ministry of Science, Innovation and Universities.S

KRAS4A induces metastatic lung adenocarcinomas in vivo in the absence of the KRAS4B isoform.

In mammals, the KRAS locus encodes two protein isoforms, KRAS4A and KRAS4B, which differ only in their C terminus via alternative splicing of distinct fourth exons. Previous studies have shown that whereas KRAS expression is essential for mouse development, the KRAS4A isoform is expendable. Here, we have generated a mouse strain that carries a terminator codon in exon 4B that leads to the expression of an unstable KRAS4B154 truncated polypeptide, hence resulting in a bona fide Kras4B-null allele. In contrast, this terminator codon leaves expression of the KRAS4A isoform unaffected. Mice selectively lacking KRAS4B expression developed to term but died perinatally because of hypertrabeculation of the ventricular wall, a defect reminiscent of that observed in embryos lacking the Kras locus. Mouse embryonic fibroblasts (MEFs) obtained from Kras4B-/- embryos proliferated less than did wild-type MEFs, because of limited expression of KRAS4A, a defect that can be compensated for by ectopic expression of this isoform. Introduction of the same terminator codon into a Kras FSFG12V allele allowed expression of an endogenous KRAS4AG12V oncogenic isoform in the absence of KRAS4B. Exposure of Kras +/FSF4AG12V4B- mice to Adeno-FLPo particles induced lung tumors with complete penetrance, albeit with increased latencies as compared with control Kras +/FSFG12V animals. Moreover, a significant percentage of these mice developed proximal metastasis, a feature seldom observed in mice expressing both mutant isoforms. These results illustrate that expression of the KRAS4AG12V mutant isoform is sufficient to induce lung tumors, thus suggesting that selective targeting of the KRAS4BG12V oncoprotein may not have significant therapeutic consequences.We thank Marta San Roman, Raquel Villar, and Nuria Cabrera for excellent technical assistance; Mayte Lamparero and Isabel Blanco (Animal Facility) for mouse work; the Histopathology Unit for processing of mouse tissues; Lola Martinez (Flow Cytometry Unit) for her help with flow cytometry analyses; Diego Megias and Manuel Perez (Confocal Microscopy Unit) for assistance with confocal microscopy; and the Mouse Genome Editing Unit for support with the generation of the mouse strains described here. We also thank Ignacio Perez de Castro (Instituto de Salud Carlos III, Madrid, Spain) for sharing the EGFP-KRAS4B plasmid and Orlando Dominguez (Genomics Unit) and Pedro P. Lopez-Casas (Clinical Research Program) for their advice on exome sequencing. This work was supported by grants from the European Research Council (ERC-2015-AdG/695566, THERACAN), the Spanish Ministry of Science, Innovation and Universities (RTC-2017-6576-1), and the Autonomous Community of Madrid (B2017/BMD-3884 iLUNG-CM); a grant from the CRIS Cancer Foundation (to M.B.); and a grant from the Spanish Ministry of Science, Innovation and Universities (RTI2018-094664-B-I00, to M.B. and M.M.). M.B. is a recipient of an Endowed Chair from the AXA Research Fund. M.S. was supported by predoctoral contract "Severo Ochoa" (BES-2016-079096) from the SpanishMinistry of Science, Innovation and Universities. G.P. was a recipient of a "Young Ph.D." grant from the Government of the Community of Madrid. F.F.-G. was supported by a formacion de profesorado universitario (FPU) fellowship from the Spanish Ministry of Science, Innovation and Universities.S

Kras oncogene ablation prevents resistance in advanced lung adenocarcinomas

KRASG12C inhibitors have revolutionized the clinical management of patients with KRASG12C-mutant lung adenocarcinoma. However, patient exposure to these inhibitors leads to the rapid onset of resistance. In this study, we have used genetically engineered mice to compare the therapeutic efficacy and the emergence of tumor resistance between genetic ablation of mutant Kras expression and pharmacological inhibition of oncogenic KRAS activity. Whereas Kras ablation induces massive tumor regression and prevents the appearance of resistant cells in vivo, treatment of KrasG12C/Trp53-driven lung adenocarcinomas with sotorasib, a selective KRASG12C inhibitor, caused a limited antitumor response similar to that observed in the clinic, including the rapid onset of resistance. Unlike in human tumors, we did not observe mutations in components of the RAS-signaling pathways. Instead, sotorasib-resistant tumors displayed amplification of the mutant Kras allele and activation of xenobiotic metabolism pathways, suggesting that reduction of the on-target activity of KRASG12C inhibitors is the main mechanism responsible for the onset of resistance. In sum, our results suggest that resistance to KRAS inhibitors could be prevented by achieving a more robust inhibition of KRAS signaling mimicking the results obtained upon Kras ablation.This work was supported by grants from the European Research Council (ERC-GA 695566, THERACAN); the Agencia Estatal de Investigación, Ministerio de Ciencia e Innovación (MCIN/AEI/10.13039/501100011033) (grant RTC2017-6576-1), cofunded by ERDF “A way of making Europe”; the Autonomous Community of Madrid (B2017/BMD-3884 iLung-CM), cofunded by FSE and ERDF “A way of making Europe”; the CRIS Cancer Foundation, the Scientific Foundation of the Spanish Association Against Cancer (GC166173694BARB); an ERA PerMed grant, funded by the Instituto de Salud Carlos III (AC20/00114), the Scientific Foundation of the Spanish Association Against Cancer (PERME20707BARB) and the European Union’s Horizon 2020 program (779282) to MB; and the Agencia Estatal de Investigación, Ministerio de Ciencia e Innovación (grant RTI2018-094664-B-I00), cofunded by ERDF “A way of making Europe” to MM and MB. Additional funding included grants from the Spanish National Research and Development Plan, Instituto de Salud Carlos III, ERDF “A way of making Europe” (PI20/01837 and DTS19/00111); the Scientific Foundation of the Spanish Association Against Cancer (LABAE20049RODR) to SRP; the Instituto de Salud Carlos III (PI19/00514), cofunded by ERDF “A way of making Europe” to CG; the Agencia Estatal de Investigación, Ministerio de Ciencia e Innovación (grant PID2020-116705RB-I00); and the Scientific Foundation of the Spanish Association Against Cancer (LABAE211678DROS) to MD. MB is a recipient of an endowed chair from the AXA Research Fund. M Salmón was supported by a predoctoral contract “Severo Ochoa” (BES-2016-079096) from the Agencia Estatal de Investigación, Ministerio de Ciencia e Innovación. OB is a recipient of a fellowship from the Formación de Personal Investigador (FPI) program of the Agencia Estatal de Investigación, Ministerio de Ciencia e Innovación. FFG was supported by a Formación de Profesorado Universitario (FPU) fellowship from the Ministerio de Universidades

A synthetic peptide from transforming growth factor beta type III receptor inhibits liver fibrogenesis in rats with carbon tetrachloride liver injury

Transforming growth factor beta1 (TGF-beta1) is a pleiotropic cytokine, which displays potent profibrogenic effects and is highly expressed in fibrotic livers. For this reason, development of TGF-B1 inhibitors might be of great importance to control liver fibrogenesis as well as other undesired side effects due to this cytokine. Potential peptide inhibitors of TGF-beta1 (derived from TGF-beta1 and from its type III receptor) were tested in vitro and in vivo using different assays. Peptides P11 and P12, derived from TGF-beta1, and P54 and P144, derived from its type III receptor, prevented TGF-beta1-dependent inhibition of MV1Lu proliferation in vitro and markedly reduced binding of TGF-beta1 to its receptors. P144 blocked TGF-beta1-dependent stimulation of a reporter gene under the control of human alpha2(I) collagen promoter. Intraperitoneal administration of P144 also showed potent antifibrogenic activity in vivo in the liver of rats receiving CCl4. These rats also showed a significant decrease in the number of activated hepatic stellate cells as compared with those treated with saline only. These results suggest that short synthetic peptides derived from TGF-beta1 type III receptor may be of value in reducing liver fibrosis in chronic liver injury

Mitochondrial Na+ controls oxidative phosphorylation and hypoxic redox signalling

All metazoans depend on O2 delivery and consumption by the mitochondrial oxidative phosphorylation (OXPHOS) system to produce energy. A decrease in O2 availability (hypoxia) leads to profound metabolic rewiring. In addition, OXPHOS uses O2 to produce reactive oxygen species (ROS) that can drive cell adaptations through redox signalling, but also trigger cell damage1–4, and both phenomena occur in hypoxia4–8. However, the precise mechanism by which acute hypoxia triggers mitochondrial ROS production is still unknown. Ca2+ is one of the best known examples of an ion acting as a second messenger9, yet the role ascribed to Na+ is to serve as a mere mediator of membrane potential and collaborating in ion transport10. Here we show that Na+ acts as a second messenger regulating OXPHOS function and ROS production by modulating fluidity of the inner mitochondrial membrane (IMM). We found that a conformational shift in mitochondrial complex I during acute hypoxia11 drives the acidification of the matrix and solubilization of calcium phosphate precipitates. The concomitant increase in matrix free-Ca2+ activates the mitochondrial Na+/Ca2+ exchanger (NCLX), which imports Na+ into the matrix. Na+ interacts with phospholipids reducing IMM fluidity and mobility of free ubiquinone between complex II and complex III, but not inside supercomplexes. As a consequence, superoxide is produced at complex III, generating a redox signal. Inhibition of mitochondrial Na+ import through NCLX is sufficient to block this pathway, preventing adaptation to hypoxia. These results reveal that Na+ import into the mitochondrial matrix controls OXPHOS function and redox signalling through an unexpected interaction with phospholipids, with profound consequences in cellular metabolism

Improved biosensing capability with novel suspended nanodisks

In this work, we provide a theoretical and experimental study of the adverse effects that inherently arise when plasmonic nanoparticles are attached to a solid support. Using the example of short-ordered arrays of gold nanodisks, we show that the right choice for the thin metal adhesion layer that is used to ensure stable binding of the nanodisks to the substrate is extremely important to achieve competitive limits of detection. Furthermore, we show that the presence of the high refractive index support undisputedly results in lower bulk and surface sensing sensitivities. To minimize this effect, we propose an isotropic chemical etch of the supporting substrate, resulting in dielectric nanopillars which distance the nanodisks from this high refractive index material. We demonstrate that this novel method not only preserves the mechanical stability but also strongly increases the sensing performance of these suspended nanodisk arrays. This is demonstrated via the label-free detection of DNA hybridization, reflecting the robustness and the surface-regenerative capabilities of these pillar-supported nanodisk arrays. Furthermore, through the successful implementation of this sensitivity enhancing method to more complex nanostructures, such as arrays of closely distanced nanodisk dimers, this method profiles itself as a simple strategy to improve the limits of detection of a wide variety of nanoplasmonic sensors. © 2011 American Chemical Society.This research was carried out with the financial support of MULTIBIOPLAS of Spanish Ministry of Science and Innovation (TEC2009-08729); the M. Botín Foundation. M. A. Otte acknowledges the “Programa de Formación de Profesorado Universitario (FPU)” of the “Ministerio de Educación” of Spain; and B. Sepulveda acknowledges the “Ramón y Cajal” program from “Ministerio de Ciencia e Innovación” of Spain for financial support.Peer Reviewe

Establishment of Pancreatic Cancer-Derived Tumor Organoids and Fibroblasts From Fresh Tissue.

Tumor organoids are three-dimensional (3D) ex vivo tumor models that recapitulate the biological key features of the original primary tumor tissues. Patient-derived tumor organoids have been used in translational cancer research and can be applied to assess treatment sensitivity and resistance, cell-cell interactions, and tumor cell interactions with the tumor microenvironment. Tumor organoids are complex culture systems that require advanced cell culture techniques and culture media with specific growth factor cocktails and a biological basement membrane that mimics the extracellular environment. The ability to establish primary tumor cultures highly depends on the tissue of origin, the cellularity, and the clinical features of the tumor, such as the tumor grade. Furthermore, tissue sample collection, material quality and quantity, as well as correct biobanking and storage are crucial elements of this procedure. The technical capabilities of the laboratory are also crucial factors to consider. Here, we report a validated SOP/protocol that is technically and economically feasible for the culture of ex vivo tumor organoids from fresh tissue samples of pancreatic adenocarcinoma origin, either from fresh primary resected patient donor tissue or patient-derived xenografts (PDX). The technique described herein can be performed in laboratories with basic tissue culture and mouse facilities and is tailored for wide application in the translational oncology field