RAF1 kinase activity is dispensable for KRAS/p53 mutant lung tumor progression.

We thank Dr. Shiva Malek and her colleagues (Genentech Inc.) for sharing their results with us before publication. We also thank M. San Roman, R. Villar, M.C. Gonzalez, A. Lopez, N. Cabrera, P. Villanueva, J. Condo, O. Dominguez, and S. Ortega for excellent technical support. 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 RTI2018094664-B-I00) and the Autonomous Community of Madrid (B2017/BMD-3884 iLUNG-CM) to M.B., as well as by 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., P.N., and F.F.-G. were supported by FPU fellowships from the Spanish Ministry of Education. L.E.-B. was a recipient of an FPI fellowship from the Spanish Ministry of Economy and Competitiveness. S.G.-A. is a recipient of a postdoctoral fellowship from the Asociacion Espanola Contra el Cancer (AECC).S

Multiple cancer pathways regulate telomere protection

Telomeres are considered as universal anti-cancer targets, as telomere maintenance is essential to sustain indefinite cancer growth. Mutations in telomerase, the enzyme that maintains telomeres, are among the most frequently found in cancer. In addition, mutations in components of the telomere protective complex, or shelterin, are also found in familial and sporadic cancers. Most efforts to target telomeres have focused in telomerase inhibition; however, recent studies suggest that direct targeting of the shelterin complex could represent a more effective strategy. In particular, we recently showed that genetic deletion of the TRF1 essential shelterin protein impairs tumor growth in aggressive lung cancer and glioblastoma (GBM) mouse models by direct induction of telomere damage independently of telomere length. Here, we screen for TRF1 inhibitory drugs using a collection of FDA-approved drugs and drugs in clinical trials, which cover the majority of pathways included in the Reactome database. Among other targets, we find that inhibition of several kinases of the Ras pathway, including ERK and MEK, recapitulates the effects of Trf1 genetic deletion, including induction of telomeric DNA damage, telomere fragility, and inhibition of cancer stemness. We further show that both bRAF and ERK2 kinases phosphorylate TRF1 in vitro and that these modifications are essential for TRF1 location to telomeres in vivo Finally, we use these new TRF1 regulatory pathways as the basis to discover novel drug combinations based on TRF1 inhibition, with the goal of effectively blocking potential resistance to individual drugs in patient-derived glioblastoma xenograft models.We thank the Confocal Microscopy, Protein Engineering, Mass Spectrometry,Comparative Pathology, and Mouse Facility Units at CNIO. MAB laboratory is funded by SAF 2013-45111-R from MINECO,Fundación Botín and Banco Santander, Worldwide Cancer Research 16-1177. LB is a fellow of the La Caixa-Severo Ochoa International PhD Programme.S

Modulation of telomere protection by the PI3K/AKT pathway

Telomeres and the insulin/PI3K pathway are considered hallmarks of aging and cancer. Here, we describe a role for PI3K/AKT in the regulation of TRF1, an essential component of the shelterin complex. PI3K and AKT chemical inhibitors reduce TRF1 telomeric foci and lead to increased telomeric DNA damage and fragility. We identify the PI3Kα isoform as responsible for this TRF1 inhibition. TRF1 is phosphorylated at different residues by AKT and these modifications regulate TRF1 protein stability and TRF1 binding to telomeric DNA in vitro and are important for in vivo TRF1 telomere location and cell viability. Patient-derived breast cancer PDX mouse models that effectively respond to a PI3Kα specific inhibitor, BYL719, show decreased TRF1 levels and increased DNA damage. These findings functionally connect two of the major pathways for cancer and aging, telomeres and the PI3K pathway, and pinpoint PI3K and AKT as novel targets for chemical modulation of telomere protection.We are indebted to D. Megias for microscopy analysis, to D. Calvo for protein purification as well as to J. Muñoz and F. García for LC/MS/MS analysis. The research was funded by project SAF2013-45111-R of Societal Changes Program of the Spanish Ministry of Economics and Competitiveness (MINECO) co-financed through the European Fund of Regional Development (FEDER), Fundación Botín, Banco Santander (Santander Universities Global Division) and Worldwide Cancer Research (WCR 16-1177).S

Tumor regression and resistance mechanisms upon CDK4 and RAF1 inactivation in KRAS/P53 mutant lung adenocarcinomas.

KRAS mutant lung adenocarcinomas remain intractable for targeted therapies. Genetic interrogation of KRAS downstream effectors, including the MAPK pathway and the interphase CDKs, identified CDK4 and RAF1 as the only targets whose genetic inactivation induces therapeutic responses without causing unacceptable toxicities. Concomitant CDK4 inactivation and RAF1 ablation prevented tumor progression and induced complete regression in 25% of KRAS/p53-driven advanced lung tumors, yet a significant percentage of those tumors that underwent partial regression retained a population of CDK4/RAF1-resistant cells. Characterization of these cells revealed two independent resistance mechanisms implicating hypermethylation of several tumor suppressors and increased PI3K activity. Importantly, these CDK4/RAF1-resistant cells can be pharmacologically controlled. These studies open the door to new therapeutic strategies to treat KRAS mutant lung cancer, including resistant tumors.We thank S. Ortega for the generation of the Cdk4FxKD mouse model; and M. San Roman, R. Villar, M. C. Gonzalez, A. Lopez, N. Cabrera, P. Villanueva, J. Condo, J. Klett, A. Cebria, A. Otero, O. Dominguez, G. Luengo, G. Garaulet, F. Mulero, and D. Megias for excellent technical support. This work was supported by European Research Council Grant ERC-2015-AdG/695566, THERACAN, Spanish Ministry of Science, Innovation, and Universities Grant RTC-2017-6576-1, and the Autonomous Community of Madrid Grant B2017/BMD-3884 iLUNG-CM (to M.B.); Spanish Ministry of Science, Innovation, and Universities Grant RTI2018-094664B-I00 (to M.B. and M.M.); and National Natural Science Foundation of China Grant 31771469 (to H.W.). M.B. is a recipient of an Endowed Chair from the AXA Research Fund. L.E.-B. is the recipient of an FPI fellowship from the Spanish Ministry of Economy and Competitiveness. F.F.-G., M.S., and P.N. were supported by an FPU fellowships from the Spanish Ministry of Education.S

CSF1R Protein Expression in Reactive Lymphoid Tissues and Lymphoma: Its Relevance in Classical Hodgkin Lymphoma.

Tumour-associated macrophages (TAMs) have been associated with survival in classic Hodgkin lymphoma (cHL) and other lymphoma types. The maturation and differentiation of tissue macrophages depends upon interactions between colony-stimulating factor 1 receptor (CSF1R) and its ligands. There remains, however, a lack of consistent information on CSF1R expression in TAMs. A new monoclonal antibody, FER216, was generated to investigate CSF1R protein distribution in formalin fixed tissue samples from 24 reactive lymphoid tissues and 187 different lymphoma types. We also analysed the distribution of CSF1R+, CD68+ and CD163+ macrophages by double immunostaining, and studied the relationship between CSF1R expression and survival in an independent series of 249 cHL patients. CSF1R+ TAMs were less frequent in B-cell lymphocytic leukaemia and lymphoblastic B-cell lymphoma than in diffuse large B-cell lymphoma, peripheral T-cell lymphoma, angioimmunoblastic T-cell lymphoma and cHL. HRS cells in cHL and, with the exception of three cases of anaplastic large cell lymphoma, the neoplastic cells in NHLs, lacked detectable CSF1R protein. A CSF1R+ enriched microenvironment in cHL was associated with shorter survival in an independent series of 249 cHL patients. CSF1R pathway activation was evident in the cHL and inactivation of this pathway could be a potential therapeutic target in cHL cases.This work was supported by grants from the Fondo de Investigaciones Sanitarias - Ministerio de Ciencia e Innovacion (PI12/1832), and Spanish Cancer Research Networks-RTICC (RD12/0036/0060), cofunded by the Fondo Europeo de Desarrollo Regional (FEDER), and the Asociacion Espanola Contra el Cancer (AECC Scientific Foundation). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.S

NOTCH pathway inactivation promotes bladder cancer progression

International audienceNOTCH signaling suppresses tumor growth and proliferation in several types of stratified epithelia. Here, we show that missense mutations in NOTCH1 and NOTCH2 found in human bladder cancers result in loss of function. In murine models, genetic ablation of the NOTCH pathway accelerated bladder tumorigenesis and promoted the formation of squamous cell carcinomas, with areas of mesenchymal features. Using bladder cancer cells, we determined that the NOTCH pathway stabilizes the epithelial phenotype through its effector HES1 and, consequently, loss of NOTCH activity favors the process of epithelial-mesenchymal transition. Evaluation of human bladder cancer samples revealed that tumors with low levels of HES1 present mesenchymal features and are more aggressive. Together, our results indicate that NOTCH serves as a tumor suppressor in the bladder and that loss of this pathway promotes mesenchymal and invasive features