ETV6 and ETV7: Siblings in hematopoiesis and its disruption in disease

A novel role of ETV6 as a pro-viral factor in host response by inhibiting TBK1 phosphorylation

E26-transforming specific (ETS) variant 6 (ETV6) is a transcription factor regulating the expression of interferon stimulating genes (ISGs) and involved in the embryonic development and hematopoietic regulation, but the role of ETV6 in host response to virus infection is not clear. In this study, we show that ETV6 was upregulated in DF-1 cells with poly(I:C) stimulation or IBDV, AIV and ARV infection via engagement of dsRNA by MDA5. Overexpression of ETV6 in DF-1 cells markedly inhibited IBDV-induced type I interferon (IFN-I) and ISGs expressions. In contrast, knockdown, or knockout of ETV6 remarkably inhibited IBDV replication via promoting IFN-I response. Furthermore, our data show that ETV6 negatively regulated host antiviral response to IBDV infection by interaction with TANK binding kinase 1 (TBK1) and subsequently inhibited its phosphorylation. These results uncovered a novel role of ETV6 as a pro-viral factor in host response by inhibiting TBK1 phosphorylation, furthering our understandings of RNA virus immunosuppression and providing a valuable clue to the development of antiviral reagents for the control of avian RNA virus infection.

Identification of early gene expression profiles associated with long-lasting antibody responses to the Ebola vaccine Ad26.ZEBOV/MVA-BN-Filo

Ebola virus disease is a severe hemorrhagic fever with a high fatality rate. We investigate transcriptome profiles at 3 h, 1 day, and 7 days after vaccination with Ad26.ZEBOV and MVA-BN-Filo. 3 h after Ad26.ZEBOV injection, we observe an increase in genes related to antigen presentation, sensing, and T and B cell receptors. The highest response occurs 1 day after Ad26.ZEBOV injection, with an increase of the gene expression of interferon-induced antiviral molecules, monocyte activation, and sensing receptors. This response is regulated by the HESX1, ATF3, ANKRD22, and ETV7 transcription factors. A plasma cell signature is observed on day 7 post-Ad26.ZEBOV vaccination, with an increase of CD138, MZB1, CD38, CD79A, and immunoglobulin genes. We have identified early expressed genes correlated with the magnitude of the antibody response 21 days after the MVA-BN-Filo and 364 days after Ad26.ZEBOV vaccinations. Our results provide early gene signatures that correlate with vaccine-induced Ebola virus glycoprotein-specific antibodies.

The ETS transcription factor ETV6 constrains the transcriptional activity of EWS-FLI to promote Ewing sarcoma

Transcription factors (TFs) are frequently mutated in cancer. Paediatric cancers exhibit few mutations genome-wide but frequently harbour sentinel mutations that affect TFs, which provides a context to precisely study the transcriptional circuits that support mutant TF-driven oncogenesis. A broadly relevant mechanism that has garnered intense focus involves the ability of mutant TFs to hijack wild-type lineage-specific TFs in self-reinforcing transcriptional circuits. However, it is not known whether this specific type of circuitry is equally crucial in all mutant TF-driven cancers. Here we describe an alternative yet central transcriptional mechanism that promotes Ewing sarcoma, wherein constraint, rather than reinforcement, of the activity of the fusion TF EWS-FLI supports cancer growth. We discover that ETV6 is a crucial TF dependency that is specific to this disease because it, counter-intuitively, represses the transcriptional output of EWS-FLI. This work discovers a previously undescribed transcriptional mechanism that promotes cancer.

The Role of IRX Homeobox Genes in Hematopoietic Progenitors and Leukemia

IRX genes are members of the TALE homeobox gene class and encode six related transcription factors (IRX1-IRX6) controlling development and cell differentiation of several tissues in humans. Classification of TALE homeobox gene expression patterns for the hematopoietic compartment, termed TALE-code, has revealed exclusive IRX1 activity in pro-B-cells and megakaryocyte erythroid progenitors (MEPs), highlighting its specific contribution to developmental processes at these early stages of hematopoietic lineage differentiation. Moreover, aberrant expression of IRX homeobox genes IRX1, IRX2, IRX3 and IRX5 has been detected in hematopoietic malignancies, including B-cell precursor acute lymphoblastic leukemia (BCP-ALL), T-cell ALL, and some subtypes of acute myeloid leukemia (AML). Expression analyses of patient samples and experimental studies using cell lines and mouse models have revealed oncogenic functions in cell differentiation arrest and upstream and downstream genes, thus, revealing normal and aberrant regulatory networks. These studies have shown how IRX genes play key roles in the development of both normal blood and immune cells, and hematopoietic malignancies. Understanding their biology serves to illuminate developmental gene regulation in the hematopoietic compartment, and may improve diagnostic classification of leukemias in the clinic and reveal new therapeutic targets and strategies.

Development and validation of a novel prognosis prediction model for patients with myelodysplastic syndrome

Background

Somatic mutations are widespread in patients with Myelodysplastic Syndrome (MDS) and are associated with prognosis. However, a practical prognostic model for MDS that incorporates somatic mutations urgently needs to be developed.

Methods

A cohort of 201 MDS patients from the Gene Expression Omnibus (GEO) database was used to develop the model, and a single-center cohort of 115 MDS cohorts from Northwest China was used for external validation. Kaplan-Meier analysis was performed to compare the effects of karyotype classifications and gene mutations on the prognosis of MDS patients. Univariate and multivariate Cox regression analyses and Lasso regression were used to screen for key prognostic factors. The shinyapps website was used to create dynamic nomograms with multiple variables. The time-dependent receiver operating characteristic (ROC) curves, calibration plots, and decision curve analysis (DCA) were used to evaluate the model's discrimination, accuracy and clinical utility.

Results

Six risk factors (age, bone morrow blast percentage, ETV6, TP53, EZH2, and ASXL1) were considered as predictor variables in the nomogram. The nomogram showed excellent discrimination, with respective the area under the ROC curve (AUC) values of 0.850, 0.839, 0.933 for the training cohort at 1 year, 3 years and 5 years; 0.715, 0.802 and 0.750 for the testing cohort at 1 year, 3 years and 5 years; and 0.668, 0.646 and 0.731 for the external validation cohort at 1 year, 3 years and 5 years. The calibration curves and decision curve showed that the nomogram had good consistency and clinical practical benefit. Finally, a stratified analysis showed that MDS patients with high risk had worse survival outcomes than patients with low risk.

Conclusion

We developed a nomogram containing six risk factors, which provides reliable and objective predictions of prognosis for MDS patients.

Combined heterozygosity of FLT3 ITD, TET2, and DNMT3A results in aggressive leukemia

Heterozygous mutations in FLT3ITD, TET2, and DNMT3A are associated with hematologic malignancies in humans. In patients, cooccurrence of mutations in FLT3ITD combined with TET2 (TF) or FLT3ITD combined with DNMT3A (DF) are frequent. However, in some rare complex acute myeloid leukemia (AML), all 3 mutations cooccur - i.e., FLT3ITD, TET2, and DNMT3A (TFD). Whether the presence of these mutations in combination result in quantitative or qualitative differences in disease manifestation has not been investigated. We generated mice expressing heterozygous Flt3ITD and concomitant for either heterozygous loss of Tet2 (TF) or Dnmt3a (DF) or both (TFD). TF and DF mice did not induce disease early on, in spite of similar changes in gene expression; during the same time frame, an aggressive form of transplantable leukemia was observed in TFD mice, which was mostly associated with quantitative but not qualitative differences in gene expression relative to TF or DF mice. The gene expression signature of TFD mice showed remarkable similarity to the human TFD gene signature at the single-cell RNA level. Importantly, TFD-driven AML responded to a combination of drugs that target Flt3ITD, inflammation, and methylation in a mouse model, as well as in a PDX model of AML bearing 3 mutations.

A Three-Gene Signature Predicts Response to Selinexor in Multiple Myeloma

PURPOSE

Selinexor is the first selective inhibitor of nuclear export to be approved for the treatment of relapsed or refractory multiple myeloma (MM). Currently, there are no known genomic biomarkers or assays to help select MM patients at higher likelihood of response to selinexor. Here, we aimed to characterize the transcriptomic correlates of response to selinexor-based therapy.

METHODS

We performed RNA sequencing on CD138+ cells from the bone marrow of 100 patients with MM who participated in the BOSTON study, followed by differential gene expression and pathway analysis. Using the differentially expressed genes, we used cox proportional hazard models to identify a gene signature predictive of response to selinexor, followed by validation in external cohorts.

RESULTS

The three-gene signature predicts response to selinexor-based therapy in patients with MM in the BOSTON cohort. Then, we validated this gene signature in 64 patients from the STORM cohort of triple-class refractory MM and additionally in an external cohort of 35 patients treated in a real-world setting outside of clinical trials. We found that the signature tracks with both depth and duration of response, and it also validates in a different tumor type using a cohort of pretreatment tumors from patients with recurrent glioblastoma. Furthermore, the genes involved in the signature, WNT10A, DUSP1, and ETV7, reveal a potential mechanism through upregulated interferon-mediated apoptotic signaling that may prime tumors to respond to selinexor-based therapy.

CONCLUSION

In this study, we present a present a novel, three-gene expression signature that predicts selinexor response in MM. This signature has important clinical relevance as it could identify patients with cancer who are most likely to benefit from treatment with selinexor-based therapy.

Fusion-associated carcinomas of the breast: Diagnostic, prognostic, and therapeutic significance

Recurrent gene fusions comprise a class of viable genetic targets in solid tumors that have culminated several recent breakthrough cancer therapies. Their role in breast cancer, however, remains largely underappreciated due to the complexity of genomic rearrangements in breast malignancy. Just recently, we and others have identified several recurrent gene fusions in breast cancer with important clinical and biological implications. Examples of the most significant recurrent gene fusions to date include (1) ESR1::CCDC170 gene fusions in luminal B and endocrine-resistant breast cancer that exert oncogenic function via modulating the HER2/HER3/SRC Proto-Oncogene (SRC) complex, (2) ESR1 exon 6 fusions in metastatic disease that drive estrogen-independent estrogen-receptor transcriptional activity, (3) BCL2L14::ETV6 fusions in a more aggressive form of the triple-negative subtype that prime epithelial-mesenchymal transition and endow paclitaxel resistance, (4) the ETV6::NTRK3 fusion in secretory breast carcinoma that constitutively activates NTRK3 kinase, (5) the oncogenic MYB-NFIB fusion as a genetic driver underpinning adenoid cystic carcinomas of the breast that activates MYB Proto-Oncogene (MYB) pathway, and (6) the NOTCH/microtubule-associated serine-threonine (MAST) kinase gene fusions that activate NOTCH and MAST signaling. Importantly, these fusions are enriched in more aggressive and lethal breast cancer presentations and appear to confer therapeutic resistance. Thus, these gene fusions could be utilized as genetic biomarkers to identify patients who require more intensive treatment and surveillance. In addition, kinase fusions are currently being evaluated in breast cancer clinical trials and ongoing mechanistic investigation is exposing therapeutic vulnerabilities in patients with fusion-positive disease.

ETV6 Regulates Hemin-Induced Erythroid Differentiation of K562 Cells through Mediating the Raf/MEK/ERK Pathway

As a member of transcription factor E-Twenty Six (ETS) family, ETS variant 6 (ETV6) plays significant role in hematopoiesis and embryonic development. ETV6 dysexpression also involved in the occurrence, development and progression of cancers and leukemia. In current work, we hypothesized that ETV6 plays a role in erythroid differentiation of chronic myeloid leukemia (CML). We found the protein expression level of ETV6 was significantly upregulated during hemin-induced erythroid differentiation of K562 cells. Moreover, overexpression of ETV6 inhibited erythroid differentiation in hemin-induced K562 cells with decreased numbers of benzidine-positive cells and decreased expression levels of erythroid differentiation specific markers glycophorin (GPA), CD71, hemoglobin A (HBA), α-globin, γ-globin and ε-globin. Conversely, ETV6 knockdown promoted erythroid differentiation in hemin-induced K562 cells. Furthermore, ETV6 expression level slightly positively with the proliferation capacity of K562 cells treated with hemin. Mechanistically, ETV6 overexpression inhibited fibrosarcoma/mitogen activated extracellular signal-regulated kinase/extracellular regulated protein kinase (Raf/MEK/ERK) pathway, ETV6 knockdown activated the Raf/MEK/ERK pathway. Collectively, the current work demonstrates that ETV6 plays an inhibitory role in the regulation of K562 cell erythroid differentiation via Raf/MEK/ERK pathway, it would be a potentially therapeutic target for dyserythropoiesis.

NKL Homeobox Genes NKX2-3 and NKX2-4 Deregulate Megakaryocytic-Erythroid Cell Differentiation in AML

NKL homeobox genes encode transcription factors that impact normal development and hematopoietic malignancies if deregulated. Recently, we established an NKL-code that describes the physiological expression pattern of eleven NKL homeobox genes in the course of hematopoiesis, allowing evaluation of aberrantly activated NKL genes in leukemia/lymphoma. Here, we identify ectopic expression of NKL homeobox gene NKX2-4 in an erythroblastic acute myeloid leukemia (AML) cell line OCI-M2 and describe investigation of its activating factors and target genes. Comparative expression profiling data of AML cell lines revealed in OCI-M2 an aberrantly activated program for endothelial development including master factor ETV2 and the additional endothelial signature genes HEY1, IRF6, and SOX7. Corresponding siRNA-mediated knockdown experiments showed their role in activating NKX2-4 expression. Furthermore, the ETV2 locus at 19p13 was genomically amplified, possibly underlying its aberrant expression. Target gene analyses of NKX2-4 revealed activated ETV2, HEY1, and SIX5 and suppressed FLI1. Comparative expression profiling analysis of public datasets for AML patients and primary megakaryocyte–erythroid progenitor cells showed conspicuous similarities to NKX2-4 activating factors and the target genes we identified, supporting the clinical relevance of our findings and developmental disturbance by NKX2-4. Finally, identification and target gene analysis of aberrantly expressed NKX2-3 in AML patients and a megakaryoblastic AML cell line ELF-153 showed activation of FLI1, contrasting with OCI-M2. FLI1 encodes a master factor for myelopoiesis, driving megakaryocytic differentiation and suppressing erythroid differentiation, thus representing a basic developmental target of these homeo-oncogenes. Taken together, we have identified aberrantly activated NKL homeobox genes NKX2-3 and NKX2-4 in AML, deregulating genes involved in megakaryocytic and erythroid differentiation processes, and thereby contributing to the formation of specific AML subtypes.

ETV7 limits antiviral gene expression and control of influenza viruses

The type I interferon (IFN) response is an important component of the innate immune response to viral infection. Precise control of IFN responses is critical because insufficient expression of IFN-stimulated genes (ISGs) can lead to a failure to restrict viral spread, whereas excessive ISG activation can result in IFN-related pathologies. Although both positive and negative regulatory factors control the magnitude and duration of IFN signaling, it is also appreciated that several ISGs regulate aspects of the IFN response themselves. In this study, we performed a CRISPR activation screen to identify previously unknown regulators of the type I IFN response. We identified the strongly induced ISG encoding ETS variant transcription factor 7 (ETV7) as a negative regulator of the type I IFN response. However, ETV7 did not uniformly suppress ISG transcription. Instead, ETV7 preferentially targeted a subset of antiviral ISGs that were particularly important for IFN-mediated control of influenza viruses. Together, our data assign a function for ETV7 as an IFN response regulator and also identify ETV7 as a potential therapeutic target to increase innate antiviral responses and enhance IFN-based antiviral therapies.

Ubiquitin-Mediated Control of ETS Transcription Factors: Roles in Cancer and Development

Genome expansion, whole genome and gene duplication events during metazoan evolution produced an extensive family of ETS genes whose members express transcription factors with a conserved winged helix-turn-helix DNA-binding domain. Unravelling their biological roles has proved challenging with functional redundancy manifest in overlapping expression patterns, a common consensus DNA-binding motif and responsiveness to mitogen-activated protein kinase signalling. Key determinants of the cellular repertoire of ETS proteins are their stability and turnover, controlled largely by the actions of selective E3 ubiquitin ligases and deubiquitinases. Here we discuss the known relationships between ETS proteins and enzymes that determine their ubiquitin status, their integration with other developmental signal transduction pathways and how suppression of ETS protein ubiquitination contributes to the malignant cell phenotype in multiple cancers.

Asian Population Is More Prone to Develop High-Risk Myelodysplastic Syndrome, Concordantly with Their Propensity to Exhibit High-Risk Cytogenetic Aberrations

Simple Summary

The world population is genetically and environmentally diverse. In particular, genetic differences related to an ethnic factor may underlie differences in cancer phenotypic expression. Therefore, we compared the epidemiology, and the clinical, biological and genetic characteristics of myelodysplastic syndrome (MDS) between Asian and Western countries. Our results show substantial differences in the incidence and age of onset between Asian and Western MDS patients. A higher proportion of Asian MDS patients fall into the high- and very-high risk prognostic MDS groups. This finding is supported by the identification of a higher proportion of high-risk cytogenetic aberrations in Asian MDS patients. However, the survival rate is similar for Western and Asian MDS patients. Our findings may impact the clinical management as well as the strategy of clinical trials targeting those genetic aberrations and mutations depending on the world area where they are run.

Abstract

This study explores the hypothesis that genetic differences related to an ethnic factor may underlie differences in phenotypic expression of myelodysplastic syndrome (MDS). First, to identify clear ethnic differences, we systematically compared the epidemiology, and the clinical, biological and genetic characteristics of MDS between Asian and Western countries over the last 20 years. Asian MDS cases show a 2- to 4-fold lower incidence and a 10-year younger age of onset compared to the Western cases. A higher proportion of Western MDS patients fall into the very low- and low-risk categories while the intermediate, high and very high-risk groups are more represented in Asian MDS patients according to the Revised International Prognostic Scoring System. Next, we investigated whether differences in prognostic risk scores could find their origin in differential cytogenetic profiles. We found that 5q deletion (del(5q)) aberrations and mutations in TET2, SF3B1, SRSF2 and IDH1/2 are more frequently reported in Western MDS patients while trisomy 8, del(20q), U2AF1 and ETV6 mutations are more frequent in Asian MDS patients. Treatment approaches differ between Western and Asian countries owing to the above discrepancies, but the overall survival rate within each prognostic group is similar for Western and Asian MDS patients. Altogether, our study highlights greater risk MDS in Asians supported by their cytogenetic profile.

Immune profiling reveals prognostic genes in high-grade serous ovarian cancer

High-grade serous ovarian cancer (HGSOC) is a heterogeneous disease with diverse clinical outcomes, highlighting a need for prognostic biomarker identification. Here, we combined tumor microenvironment (TME) scores with HGSOC characteristics to identify immune-related prognostic genes through analysis of gene expression profiles and clinical patient data from The Cancer Genome Atlas and the International Cancer Genome Consortium public cohorts. We found that high TME scores (TMEscores) based on the fractions of immune cell types correlated with better overall survival. Furthermore, differential expression analysis revealed 329 differentially expressed genes between patients with high vs. low TMEscores. Gene Ontology and Kyoto Encyclopedia of Genes and Genomes analyses showed that these genes participated mainly in immune-related functions and, among them, 48 TME-related genes predicted overall survival in HGSOC. Seven of those genes were associated with prognosis in an independent HGSOC database. Finally, the two genes with the lowest p-values in the prognostic analysis (GBP1, ETV7) were verified through in vitro experiments. These findings reveal specific TME-related genes that could serve as effective prognostic biomarkers for HGSOC.

Landscape analysis of adjacent gene rearrangements reveals BCL2L14-ETV6 gene fusions in more aggressive triple-negative breast cancer

Triple-negative breast cancer (TNBC) accounts for 10 to 20% of breast cancer, with chemotherapy as its mainstay of treatment due to lack of well-defined targets, and recent genomic sequencing studies have revealed a paucity of TNBC-specific mutations. Recurrent gene fusions comprise a class of viable genetic targets in solid tumors; however, their role in breast cancer remains underappreciated due to the complexity of genomic rearrangements in this cancer. Our interrogation of the whole-genome sequencing data for 215 breast tumors catalogued 99 recurrent gene fusions, 57% of which are cryptic adjacent gene rearrangements (AGRs). The most frequent AGRs, BCL2L14-ETV6, TTC6-MIPOL1, ESR1-CCDC170, and AKAP8-BRD4, were preferentially found in the more aggressive forms of breast cancers that lack well-defined genetic targets. Among these, BCL2L14-ETV6 was exclusively detected in TNBC, and interrogation of four independent patient cohorts detected BCL2L14-ETV6 in 4.4 to 12.2% of TNBC tumors. Interestingly, these fusion-positive tumors exhibit more aggressive histopathological features, such as gross necrosis and high tumor grade. Amid TNBC subtypes, BCL2L14-ETV6 is most frequently detected in the mesenchymal entity, accounting for ∼19% of these tumors. Ectopic expression of BCL2L14-ETV6 fusions induce distinct expression changes from wild-type ETV6 and enhance cell motility and invasiveness of TNBC and benign breast epithelial cells. Furthermore, BCL2L14-ETV6 fusions prime partial epithelial-mesenchymal transition and endow resistance to paclitaxel treatment. Together, these data reveal AGRs as a class of underexplored genetic aberrations that could be pathological in breast cancer, and identify BCL2L14-ETV6 as a recurrent gene fusion in more aggressive form of TNBC tumors.

Ectopia associated MN1 fusions and aberrant activation in myeloid neoplasms with t(12;22)(p13;q12)

Chromosome translocation t(12;22)(p13;q12)/MN1-ETV6 and MN1 overexpression confer a subset of adverse prognostic AML but so far lack in-depth research. We focused on the clinical course and comprehensive genetic analysis of eight cases with t(12;22)(p13;q12) and one with t(12;17;22) (p13;q21;q13) to elucidate their molecular etiology and outcomes of allogeneic hemopoietic stem cell transplantation (allo-HSCT). The total incidence of t(12;22)(p13;q12) and related translocations was 0.32% in myeloid neoplasms. These patients were confirmed to have dismal prognosis when treated only with chemotherapy, and we firstly provided evidence that they can significantly benefit from timely allo-HSCT. Five cases were MN1-ETV6 positive, and a novel MN1-STAT3 fusion was identified in the patient with triadic translocation. Significant MN1 overexpression was observed in all three MN1-fusion-negative cases. Genetic analysis highlighted the evidence of an ectopic super-enhancer associated orchestrated mechanism of MN1 overexpression and ETV6 haploinsufficiency in t(12;22)(p13;q12) myeloid neoplasms, rather than the conventional thought of MN1-ETV6 fusion formation. We also disclosed the high concomitance of trisomy 8 and 531 Kbps focal 8q duplication in t(12;22)(p13;q12) cases. The new perspective about this entity of disease will enlighten further research to define the mechanism of tumorigenesis and discover effective treatments for MN1-driven malignancies.

Transmembrane adaptor protein WBP1L regulates CXCR4 signalling and murine haematopoiesis

WW domain binding protein 1-like (WBP1L), also known as outcome predictor of acute leukaemia 1 (OPAL1), is a transmembrane adaptor protein, expression of which correlates with ETV6-RUNX1 (t(12;21)(p13;q22)) translocation and favourable prognosis in childhood leukaemia. It has a broad expression pattern in haematopoietic and in non-haematopoietic cells. However, its physiological function has been unknown. Here, we show that WBP1L negatively regulates signalling through a critical chemokine receptor CXCR4 in multiple leucocyte subsets and cell lines. We also show that WBP1L interacts with NEDD4-family ubiquitin ligases and regulates CXCR4 ubiquitination and expression. Moreover, analysis of Wbp1l-deficient mice revealed alterations in B cell development and enhanced efficiency of bone marrow cell transplantation. Collectively, our data show that WBP1L is a novel regulator of CXCR4 signalling and haematopoiesis.

ETS transcription factors as emerging drug targets in cancer

The ETS family of proteins consists of 28 transcription factors, many of which have been implicated in development and progression of a variety of cancers. While one family member, ERG, has been rigorously studied in the context of prostate cancer where it plays a critical role, other ETS factors keep emerging as potential hallmark oncodrivers. In recent years, numerous studies have reported initial discoveries of small molecule inhibitors of ETS proteins and opened novel avenues for ETS-directed cancer therapies. This review summarizes the state of the art data on therapeutic targeting of ETS family members and highlights the corresponding drug discovery strategies.

FOXO1 and ETV6 genes may represent novel regulators of splicing factor expression in cellular senescence

Cellular plasticity is a key facet of cellular homeostasis requiring correct temporal and spatial patterns of alternative splicing. Splicing factors, which orchestrate this process, demonstrate age-related dysregulation of expression; they are emerging as potential influences on aging and longevity. The upstream drivers of these alterations are still unclear but may involve aberrant cellular signaling. We compared the phosphorylation status of proteins in multiple signaling pathways in early and late passage human primary fibroblasts. We then assessed the impact of chemical inhibition or targeted knockdown of direct downstream targets of the ERK and AKT pathways on splicing factor expression, cellular senescence, and proliferation kinetics in senescent primary human fibroblasts. Components of the ERK and AKT signaling pathways demonstrated altered activation during cellular aging. Inhibition of AKT and ERK pathways led to up-regulation of splicing factor expression, reduction in senescent cell load, and partial reversal of multiple cellular senescence phenotypes in a dose-dependent manner. Furthermore, targeted knockdown of the genes encoding the downstream targets FOXO1 or ETV6 was sufficient to mimic these observations. Our results suggest that age-associated dysregulation of splicing factor expression and cellular senescence may derive in part from altered activity of ERK and AKT signaling and may act in part through the ETV6 and FOXO1 transcription factors. Targeting the activity of downstream effectors of ERK and AKT may therefore represent promising targets for future therapeutic intervention.-Latorre, E., Ostler, E. L., Faragher, R. G. A., Harries, L. W. FOXO1 and ETV6 genes may represent novel regulators of splicing factor expression in cellular senescence.