Lomberk, Gwen

Krüppel-like factor (KLF)-10 is an important transcriptional regulator of TGF-β1signaling in both CD8+and CD4+T lymphocytes. In the present study, we demonstrate a novel role for KLF10 in the regulation of TGFβRII expression with functional relevance in macrophage differentiation and activation. We first show that transfer of KLF10−/−bone marrow-derived macrophages into wild-type (WT) mice leads to exacerbation of experimental colitis. At the cell biological level, using two phenotypic strategies, we show that KLF10-deficient mice have an altered colonic macrophage phenotype with higher frequency of proinflammatory LyC6+MHCII+cells and a reciprocal decrease of the anti-inflammatory LyC6−MHCII+subset. Additionally, the anti-inflammatory CD11b+CX3CR1hisubset of colonic macrophages is significantly decreased in KLF10−/−compared with WT mice under inflammatory conditions. Molecularly, CD11b+colonic macrophages from KLF10−/−mice exhibit a proinflammatory cytokine profile with increased production of TNF-α and lower production of IL-10 in response to LPS stimulation. Because KLF10 is a transcription factor, we explored how this protein may regulate macrophage function. Consequently, we analyzed the expression of TGFβRII expression in colonic macrophages and found that, in the absence of KLF10, macrophages express lower levels of TGFβRII and display an attenuated Smad-2 phosphorylation following TGF-β1stimulation. We further show that KLF10 directly binds to the TGFβRII promoter in macrophages, leading to enhanced gene expression through histone H3 acetylation. Collectively, our data reveal a critical role for KLF10 in the epigenetic regulation of TGFβRII expression in macrophages and the acquisition of a “regulatory” phenotype that contributes to intestinal mucosal homeostasis.

Abstract Pancreatic ductal adenocarcinoma (PDAC) offers an optimal model for discovering “druggable” molecular pathways that participate in inflammation-associated cancer development. Chronic pancreatitis, a common prolonged inflammatory disease, behaves as a well-known premalignant condition that contributes to PDAC development. Although the mechanisms underlying the pancreatitis-to-cancer transition remain to be fully elucidated, emerging evidence supports the hypothesis that the actions of proinflammatory mediators on cells harboring Kras mutations promote neoplastic transformation. Recent elegant studies demonstrated that the IL17 pathway mediates this phenomenon and can be targeted with antibodies, but the downstream mechanisms by which IL17 functions during this transition are currently unclear. In this study, we demonstrate that IL17 induces the expression of REG3β, a well-known mediator of pancreatitis, during acinar-to-ductal metaplasia and in early pancreatic intraepithelial neoplasia (PanIN) lesions. Furthermore, we found that REG3β promotes cell growth and decreases sensitivity to cell death through activation of the gp130-JAK2-STAT3-dependent pathway. Genetic inactivation of REG3β in the context of oncogenic Kras-driven PDAC resulted in reduced PanIN formation, an effect that could be rescued by administration of exogenous REG3β. Taken together, our findings provide mechanistic insight into the pathways underlying inflammation-associated pancreatic cancer, revealing a dual and contextual pathophysiologic role for REG3β during pancreatitis and PDAC initiation. Cancer Res; 75(22); 4852–62. ©2015 AACR.

We have previously shown that amino acid changes in the human Kruppel-Like Factor (KLF) 11 protein is associated with the development of maturity onset diabetes of the young VII, whereas complete inactivation of this pathway by the −331 human insulin mutation causes neonatal diabetes mellitus. Here, we report that Klf11−/− mice have decreased circulating insulin levels, alterations in the control of blood glucose and body weight, as well as serum dyslipidemia, but do not develop diabetes. Functional assays using ex vivo liver tissue sections demonstrate that Klf11−/− mice display increased insulin sensitivity. Genome-wide experiments validated by pathway-specific quantitative PCR arrays reveal that the Klf11−/− phenotype associates to alterations in the regulation of gene networks involved in lipid metabolism, in particular those regulated by peroxisome proliferator-activated receptor-γ. Combined, these results demonstrate that the major phenotype given by the whole-body deletion of Klf11 in mouse is not diabetes but increased insulin sensitivity, likely due to altered transcriptional regulation in target tissues. The absence of diabetes in the Klf11−/− mouse either indicates an interspecies difference for the role of this transcription factor in metabolic homeostasis between mouse and humans, or potentially highlights the fact that other molecular factors can compensate for its absence. Nevertheless, the data of this study, gathered at the whole-organism level, further support a role for KLF11 in metabolic processes like insulin sensitivity, which regulation is critical in several forms of diabetes.

Abstract Background: The transcription factor Krüppel-like factor 5 (KLF5) is essential for normal homeostasis, stemness, and tumorigenesis. Typically, KLF5 functions as a transcriptional activator, including in esophageal epithelia where KLF5 promotes keratinocyte proliferation and migration by activating EGFR and ILK, respectively, and prevents transformation by activating Notch1. Yet, the function of KLF5 is context dependent, and mutation of the tumor suppressor p53 switches KLF5 from a transcriptional activator to a repressor of p21Waf1/Cip1 and from pro-proliferative to anti-proliferative. Interestingly, KLF5 also inhibits p53 itself, though the mechanism of this inhibition is unknown. We hypothesized that the functional switch of KLF5 from transcriptional activator to repressor involves the recruitment of a co-repressor. Methods: Primary human esophageal keratinocytes immortalized with hTERT were stably infected with inducible lentivirus containing shRNA against KLF5 or Sin3A. p53 mRNA and protein levels were assessed by real-time quantitative PCR and Western blotting, respectively, and p53 protein stability was evaluated by pulse-chase experiments. We employed ChIP across a 4 kb region on the p53 gene, from 2 kb upstream to 2 kb downstream of the transcription start site, to identify the region of KLF5 binding on p53. Promoter activity was assessed with a series of luciferase reporters containing varying lengths of p53 and its upstream regulatory region. Protein-protein interaction was examined by co-IP. Results: KLF5 knockdown significantly increased p53 both at the mRNA and protein levels. In unstressed cells p53 protein undergoes rapid degradation such that p53 levels are typically low. Yet, with KLF5 knockdown, despite increased p53 protein levels, we saw no changes in p53 protein stability. By ChIP, we identified a region of KLF5 binding to p53 between -600 to -356 bp upstream of the transcription start site. Several other KLF family members can interact with the co-repressor Sin3A, and we found that Sin3A also complexed with KLF5 in human primary esophageal keratinocytes. Knockdown of Sin3A abolished the inhibitory effect of KLF5 on p53, resulting in elevated p53 expression, growth inhibition, and increased apoptosis. Conclusion: KLF5 transcriptionally represses p53 via the co-repressor Sin3A. Thus, KLF5 promotes cell proliferation in normal keratinocytes by both activating pro-growth signals and inhibiting the brake machinery of the cell cycle. Citation Format: Yizeng Yang, Taicheng Zhou, Zhen Zong, Gwen Lomberk, Raul Urrutia, Jonathan Katz. Regulation of p53 function by KLF5. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 2087. doi:10.1158/1538-7445.AM2015-2087

We have previously demonstrated a crucial role of nuclear protein 1 (NUPR1) in tumor development and progression. In this work, we report the functional characterization of a novel Nupr1‐like isoform (NUPR1L) and its functional interaction with the protumoral factor NUPR1. Through the use of primary sequence analysis, threading, and homology‐based molecular modeling, as well as expression and immunolocalization, studies reveal that NUPR1L displays properties, which are similar to member of the HMG‐like family of chromatin regulators, including its ability to translocate to the cell nucleus and bind to DNA. Analysis of the NUPR1L promoter showed the presence of two p53‐response elements at positions −37 and −7, respectively. Experiments using reporter assays combined with site‐directed mutagenesis and using cells with controllable p53 expression demonstrate that both of these sequences are responsible for the regulation of NUPR1L expression by p53. Congruently, NUPR1L gene expression is activated in response to DNA damage induced by oxaliplatin treatment or cell cycle arrest induced by serum starvation, two well‐validated methods to achieve p53 activation. Interestingly, expression of NUPR1L downregulates the expression of NUPR1, its closely related protumoral isoform, by a mechanism that involves the inhibition of its promoter activity. At the cellular level, overexpression of NUPR1L induces G1 cell cycle arrest and a decrease in their cell viability, an effect that is mediated, at least in part, by downregulating NUPR1 expression. Combined, these experiments constitute the first functional characterization of NUPR1L as a new p53‐induced gene, which negatively regulates the protumoral factor NUPR1. J. Cell. Physiol. 230: 2936–2950, 2015. © 2015 Wiley Periodicals, Inc.

KLF10 has recently elicited significant attention as a transcriptional regulator of transforming growth factor-β1 (TGF-β1) signaling in CD4+ T cells. In the current study, we demonstrate a novel role for KLF10 in the regulation of TGF-β receptor II (TGF-βRII) expression with functional relevance in antiviral immune response. Specifically, we show that KLF10-deficient mice have an increased number of effector/memory CD8+ T cells, display higher levels of the T helper type 1 cell-associated transcription factor T-bet, and produce more IFN-γ following in vitro stimulation. In addition, KLF10−/− CD8+ T cells show enhanced proliferation in vitro and homeostatic proliferation in vivo. Freshly isolated CD8+ T cells from the spleen of adult mice express lower levels of surface TGF-βRII (TβRII). Congruently, in vitro activation of KLF10-deficient CD8+ T cells upregulate TGF-βRII to a lesser extent compared with wild-type (WT) CD8+ T cells, which results in attenuated Smad2 phosphorylation following TGF-β1 stimulation compared with WT CD8+ T cells. Moreover, we demonstrate that KLF10 directly binds to the TGF-βRII promoter in T cells, leading to enhanced gene expression. In vivo viral infection with Daniel's strain Theiler's murine encephalomyelitis virus (TMEV) also led to lower expression of TGF-βRII among viral-specific KLF10−/− CD8+ T cells and a higher percentage of IFN-γ-producing CD8+ T cells in the spleen. Collectively, our data reveal a critical role for KLF10 in the transcriptional activation of TGF-βRII in CD8+ T cells. Thus, KLF10 regulation of TGF-βRII in this cell subset may likely play a critical role in viral and tumor immune responses for which the integrity of the TGF-β1/TGF-βRII signaling pathway is crucial.

Inducible gene expression, which requires chromatin remodeling on gene promoters, underlies the epigenetically inherited differentiation program of most immune cells. However, chromatin-mediated mechanisms that underlie these events in T regulatory cells remain to be fully characterized. Here, we report that inducibility of FOXP3, a key transcription factor for the development of T regulatory cells, depends upon Kruppel-like factor 10 (KLF10) interacting with two antagonistic histone-modifying systems. We utilized chromatin immunoprecipitation, genome-integrated reporter assays, and functional domain KLF10 mutant proteins, to characterize reciprocal interactions between this transcription factor and either the Sin3-histone deacetylase complex or the histone acetyltransferase, p300/CBP-associated factor (PCAF). We characterize a Sin3-interacting repressor domain on the NH2 terminus of KLF10, which works to limit the activating function of this transcription factor. Indeed, inactivation of this Sin3-interacting domain renders KLF10 able to physically associate with PCAF as to induce FOXP3 gene transcription. We show that this biochemical data derived from studying our genome-integrated reporter cell system are recapitulated in primary murine lymphocytes. Collectively, these results advance our understanding of how a single transcription factor, namely KLF10, functions as a toggle to integrate antagonistic signals regulating FOXP3 and, thus, immune activation.