Guillermo Rodríguez-Hernández

Crebbp loss cooperates with Bcl2 overexpression to promote lymphoma in mice

CREBBP is targeted by inactivating mutations in follicular lymphoma (FL) and diffuse large B-cell lymphoma (DLBCL). Here, we provide evidence from transgenic mouse models that Crebbp deletion results in deficits in B-cell development and can cooperate with Bcl2 overexpression to promote B-cell lymphoma. Through transcriptional and epigenetic profiling of these B cells, we found that Crebbp inactivation was associated with broad transcriptional alterations, but no changes in the patterns of histone acetylation at the proximal regulatory regions of these genes. However, B cells with Crebbp inactivation showed high expression of Myc and patterns of altered histone acetylation that were localized to intragenic regions, enriched for Myc DNA binding motifs, and showed Myc binding. Through the analysis of CREBBP mutations from a large cohort of primary human FL and DLBCL, we show a significant difference in the spectrum of CREBBP mutations in these 2 diseases, with higher frequencies of nonsense/frameshift mutations in DLBCL compared with FL. Together, our data therefore provide important links between Crebbp inactivation and Bcl2 dependence and show a role for Crebbp inactivation in the induction of Myc expression. We suggest this may parallel the role of CREBBP frameshift/nonsense mutations in DLBCL that result in loss of the protein, but may contrast the role of missense mutations in the lysine acetyltransferase domain that are more frequently observed in FL and yield an inactive protein.

Infection exposure promotes ETV6-RUNX1 precursor B cell leukemia via impaired H3K4 demethylases

ETV6-RUNX1 is associated with the most common subtype of childhood leukemia. As few ETV6-RUNX1 carriers develop precursor B-cell acute lymphocytic leukemia (pB-ALL), the underlying genetic basis for development of full-blown leukemia remains to be identified, but the appearance of leukemia cases in time-space clusters keeps infection as a potential causal factor. Here, we present in vivo genetic evidence mechanistically connecting preleukemic ETV6-RUNX1 expression in hematopoetic stem cells/precursor cells (HSC/PC) and postnatal infections for human-like pB-ALL. In our model, ETV6-RUNX1 conferred a low risk of developing pB-ALL after exposure to common pathogens, corroborating the low incidence observed in humans. Murine preleukemic ETV6-RUNX1 pro/preB cells showed high Rag1/2 expression, known for human ETV6-RUNX1 pB-ALL. Murine and human ETV6-RUNX1 pB-ALL revealed recurrent genomic alterations, with a relevant proportion affecting genes of the lysine demethylase (KDM) family. KDM5C loss of function resulted in increased levels of H3K4me3, which coprecipitated with RAG2 in a human cell line model, laying the molecular basis for recombination activity. We conclude that alterations of KDM family members represent a disease-driving mechanism and an explanation for RAG off-target cleavage observed in humans. Our results explain the genetic basis for clonal evolution of an ETV6-RUNX1 preleukemic clone to pB-ALL after infection exposure and offer the possibility of novel therapeutic approaches. Cancer Res; 77(16); 4365-77. ©2017 AACR.

Lmo2 expression defines tumor cell identity during T‐cell leukemogenesis

The impact of LMO2 expression on cell lineage decisions during T‐cell leukemogenesis remains largely elusive. Using genetic lineage tracing, we have explored the potential of LMO2 in dictating a T‐cell malignant phenotype. We first initiated LMO2 expression in hematopoietic stem/progenitor cells and maintained its expression in all hematopoietic cells. These mice develop exclusively aggressive human‐like T‐ALL. In order to uncover a potential exclusive reprogramming effect of LMO2 in murine hematopoietic stem/progenitor cells, we next showed that transient LMO2 expression is sufficient for oncogenic function and induction of T‐ALL. The resulting T‐ALLs lacked LMO2 and its target‐gene expression, and histologically, transcriptionally, and genetically similar to human LMO2‐driven T‐ALL. We next found that during T‐ALL development, secondary genomic alterations take place within the thymus. However, the permissiveness for development of T‐ALL seems to be associated with wider windows of differentiation than previously appreciated. Restricted Cre‐mediated activation of Lmo2 at different stages of B‐cell development induces systematically and unexpectedly T‐ALL that closely resembled those of their natural counterparts. Together, these results provide a novel paradigm for the generation of tumor T cells through reprogramming in vivo and could be relevant to improve the response of T‐ALL to current therapies.

The Making of Leukemia

Due to the clonal nature of human leukemia evolution, all leukemic cells carry the same leukemia-initiating genetic lesions, independently of the intrinsic tumoral cellular heterogeneity. However, the latest findings have shown that the mode of action of oncogenes is not homogeneous throughout the developmental history of leukemia. Studies on different types of hematopoietic tumors have shown that the contribution of oncogenes to leukemia is mainly mediated through the epigenetic reprogramming of the leukemia-initiating target cell. This driving of cancer by a malignant epigenetic stem cell rewiring is, however, not exclusive of the hematopoietic system, but rather represents a common tumoral mechanism that is also at work in epithelial tumors. Tumoral epigenetic reprogramming is therefore a new type of interaction between genes and their target cells, in which the action of the oncogene modifies the epigenome to prime leukemia development by establishing a new pathological tumoral cellular identity. This reprogramming may remain latent until it is triggered by either endogenous or environmental stimuli. This new view on the making of leukemia not only reveals a novel function for oncogenes, but also provides evidence for a previously unconsidered model of leukemogenesis, in which the programming of the leukemia cellular identity has already occurred at the level of stem cells, therefore showing a role for oncogenes in the timing of leukemia initiation.

Loss of Pax5 exploits Sca1-BCR-ABLp190 susceptibility to confer the metabolic shift essential for pB-ALL

Preleukemic clones carrying BCR-ABLp190 oncogenic lesions are found in neonatal cord blood, where the majority of preleukemic carriers do not convert into precursor B-cell acute lymphoblastic leukemia (pB-ALL). However, the critical question of how these preleukemic cells transform into pB-ALL remains undefined. Here, we model a BCR-ABLp190 preleukemic state and show that limiting BCR-ABLp190 expression to hematopoietic stem/progenitor cells (HS/PC) in mice (Sca1-BCR-ABLp190) causes pB-ALL at low penetrance, which resembles the human disease. pB-ALL blast cells were BCR-ABL-negative and transcriptionally similar to pro-B/pre-B cells, suggesting disease onset upon reduced Pax5 functionality. Consistent with this, double Sca1-BCR-ABLp190+Pax5+/- mice developed pB-ALL with shorter latencies, 90% incidence, and accumulation of genomic alterations in the remaining wild-type Pax5 allele. Mechanistically, the Pax5-deficient leukemic pro-B cells exhibited a metabolic switch toward increased glucose utilization and energy metabolism. Transcriptome analysis revealed that metabolic genes (IDH1, G6PC3, GAPDH, PGK1, MYC, ENO1, ACO1) were upregulated in Pax5-deficient leukemic cells, and a similar metabolic signature could be observed in human leukemia. Our studies unveil the first in vivo evidence that the combination between Sca1-BCR-ABLp190 and metabolic reprogramming imposed by reduced Pax5 expression is sufficient for pB-ALL development. These findings might help to prevent conversion of BCR-ABLp190 preleukemic cells.Significance: Loss of Pax5 drives metabolic reprogramming, which together with Sca1-restricted BCR-ABL expression enables leukemic transformation. Cancer Res; 78(10); 2669-79. ©2018 AACR.

Early epigenetic cancer decisions

Abstract A cancer dogma states that inactivation of oncogene(s) can cause cancer remission, implying that oncogenes are the Achilles’ heel of cancers. This current model of cancer has kept oncogenes firmly in focus as therapeutic targets and is in agreement with the fact that in human cancers all cancerous cells, with independence of the cellular heterogeneity existing within the tumour, carry the same oncogenic genetic lesions. However, recent studies of the interactions between an oncogene and its target cell have shown that oncogenes contribute to cancer development via developmental reprogramming of the epigenome within the target cell. These results provide the first evidence that carcinogenesis can be initiated by epigenetic stem cell reprogramming, and uncover a new role for oncogenes in the origin of cancer. Here we analyse these evidences and discuss how this vision offers new avenues for developing novel anti-cancer interventions.

T-cell leukemogenesis is an inappropriate lineage decision-making process: implications for precision oncology

ABSTRACT Genetic lineage tracing in cell type-specific mouse models of T-cell acute lymphoblastic leukemia (T-ALL) have revealed that tumor cell identity is imposed by expression of the oncogene Lim Domain Only 2 (LMO2), rather than by the target cell phenotype. This approach allowed to identify that secondary genomic alterations, like Notch1 mutations, appeared late and only took place within the thymus during T-ALL development. These concepts are therefore critical for the development of modern therapies aimed at curing T-ALL.

Dnmt1 links BCR-ABLp210 to epigenetic tumor stem cell priming in myeloid leukemia

Research in CVD group is partially supported by FEDER, “Miguel Servet” Grant (CP14/00082 - AES 2013-2016) from the Instituto de Salud Carlos III (Ministerio de Economia y Competitividad), “Fondo de Investigaciones Sanitarias/Instituto de Salud Carlos III” (PI17/00167), and by the Lady Tata International Award for Research in Leukaemia 2016–2017. Research in ISG group is partially supported by FEDER and by MINECO (SAF2012-32810, SAF2015-64420-R and Red de Excelencia Consolider OncoBIO SAF2014-57791- REDC), Instituto de Salud Carlos III (PIE14/00066), ISCIII- Plan de Ayudas IBSAL 2015 Proyectos Integrados (IBY15/00003), by Junta de Castilla y Leon (BIO/SA51/15, CSI001U14, UIC-017, and CSI001U16), and by the German Carreras Foundation (DJCLS R13/26). ISG lab is a member of the EuroSyStem and the DECIDE Network funded by the European Union under the FP7 program. IGR was supported by BES-Ministerio de Economia y Competitividad (BES2013-063789). GRH was supported by FSE-Conserjeria de Educacion de la Junta de Castilla y Leon (CSI001-15).

Modeling the process of childhood ETV6-RUNX1 B-cell leukemias

ETV6-RUNX1 is associated with the most common subtype of childhood leukemia. Pre-leukaemic clones carrying ETV6-RUNX1 oncogenic lesions are frequently found in neonatal cord blood, but only few ETV6-RUNX1 carriers develop pB-ALL. The highly demanding and pending challenge is to reveal the multistep natural history of ETV6-RUNX1 pB-ALL, because it can offer non-toxic prophylactic interventions to preleukemic carriers. However, the lack of a genetically engineered ETV6-RUNX1 mouse model mimicking the human pB-ALL has hampered our understanding of the pathogenesis of this disease. This rule has now been broken in a study of the effect of the ETV6-RUNX1 oncogene in cancer development in a mouse model in which oncogene expression is restricted to the stem cell compartment. In this article, we review the different attempts to model this disease, including the recent representative success stories and we discuss its potential application to both identify etiologic factors of childhood ETV6-RUNX1 pB-ALL and prevent the conversion of a preleukemic clone in an irreversible transformed state.

Could Vitamin D Analogues Be Used to Target Leukemia Stem Cells

Leukemic stem cells (LSCs) are defined as cells that possess the ability to self-renew and give rise to the differentiated cancer cells that comprise the tumor. These LSCs seem to show chemo-resistance and radio-resistance leading to the failure of conventional cancer therapies. Current therapies are directed at the fast growing tumor mass leaving the LSC fraction untouched. Eliminating LSCs, the root of cancer origin and recurrence, is considered to be a hopeful approach to improve survival or even to cure cancer patients. In order to achieve this, the characterization of LSCs is a prerequisite in order to develop LSC-based therapies to eliminate them. Here we review if vitamin D analogues may allow an avenue to target the LSCs.