Abstract
Objective: Poor tumor differentiation status is associated with worse patient outcome in colorectal cancer. However, the molecular basis for loss of differentiation in colon cancer is not ...well understood. We have found that the transcription factor Ets homologous factor (EHF) is highly expressed in the normal human and mouse colonic epithelium and is down-regulated in poorly-differentiated colorectal cancer cell lines. The aim of this study was to investigate the role of EHF in regulating normal colonic epithelial cell differentiation in vivo.
Methods: A novel mouse model was generated in which the Ets DNA binding domain (exon 8) of EHF was flanked by loxP sites (EHFlox/lox). To inactive EHF in the intestinal epithelium, EHFlox/lox mice were crossed to Villin-CreERT2 mice and recombination induced by tamoxifen treatment. Tamoxifen and vehicle treated mice were monitored weekly for up to one year. At each endpoint, tissue was collected and the effect of EHF deletion on intestinal cell proliferation and differentiation assessed by qRT-PCR and immunohistochemistry.
Results: Targeted inactivation of EHF in the small intestinal and colonic epithelium following tamoxifen treatment was confirmed at the DNA and RNA level. EHF inactivation in the intestinal epithelium had minimal effect on survival, weight gain and overall health of the animals. Furthermore, loss of EHF did not markedly affect cell proliferation or the overall architecture of the intestinal epithelium. Finally, EHF inactivation also had minimal effect on markers of absorptive, enteroendocrine or Paneth cell differentiation but did reduce the number of goblet cells in the colonic epithelium.
Conclusion: EHF does not play a major role in regulating cell proliferation in the mouse intestine but may play a role in regulating goblet cell differentiation. The role of EHF in intestinal tumourigenesis and response to stress are currently being investigated.
Citation Format: Camilla M. Reehorst, Ian Y. Luk, Rebecca Nightingale, Mercedes Davalos-Salas, Amardeep S. Dhillon, John M. Mariadason. Investigating the in vivo role of the EHF transcription factor in intestinal epithelial differentiation abstract. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 3529. doi:10.1158/1538-7445.AM2017-3529
The metabolism of cancer cells is often reprogrammed by dysregulation of metabolic enzymes. Transketolase-like 1 (TKTL1) is a homodimeric transketolase linking the pentose-phosphate pathway with the ...glycolytic pathway. It is generally silenced at a transcriptional level in somatic tissues. However, in human cancers its expression is associated with the acquisition of a glycolytic phenotype (the Warburg effect) by cancer cells that contributes to the progression of malignant tumors. In melanoma, defective promoter methylation results in the expression of genes and their products that can affect the tumor cell's phenotype including the modification of immune and functional characteristics. The present study evaluates the role of TKTL1 as a mediator of disease progression in melanoma associated with a defective methylation phenotype.
The expression of TKTL1 in metastatic melanoma tumors and cell lines was analysed by qRT-PCR and immunohistochemistry. The promoter methylation status of TKTL1 in melanoma cells was evaluated by quantitative methylation specific PCR. Using qRT-PCR, the effect of a DNA demethylating agent 5-aza-2'-deoxycytidine (5aza) on the expression of TKTL1 was examined. Biochemical and molecular analyses such as glucose consumption, lactate production, invasion, proliferation and cell cycle progression together with ectopic expression and siRNA mediated knockdown were used to investigate the role of TKTL1 in melanoma cells.
Expression of TKTL1 was highly restricted in normal adult tissues and was overexpressed in a subset of metastatic melanoma tumors and derived cell lines. The TKTL1 promoter was activated by hypomethylation and treatment with 5aza induced TKTL1 expression in melanoma cells. Augmented expression of TKTL1 in melanoma cells was associated with a glycolytic phenotype. Loss and gain of function studies revealed that TKTL1 contributed to enhanced invasion of melanoma cells.
Our data provide evidence for an important role of TKTL1 in aerobic glycolysis and tumor promotion in melanoma that may result from defective promoter methylation. This epigenetic change may enable the natural selection of tumor cells with a metabolic phenotype and thereby provide a potential therapeutic target for a subset of melanoma tumors with elevated TKTL1 expression.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
El control adecuado del ciclo celular mediante la acción coordinada de la familia de factores de transcripción E2F resulta ser clave para la homeostasis celular. El entender su modo de acción desde ...una perspectiva epigenética resulta ser un tema de gran actualidad y cambia la visión de cómo es regulado el ciclo celular. Uno de los principales reguladores epigenéticos está conformado por el grupo de proteínas polycomb (PcG), relacionadas con procesos patológicos como el cáncer, a través de la desregulación a nivel epigenético de genes supresores de tumores como BRCA1, p16 y p53, entre otros. Con relación a lo anterior, la regulación del gen supresor Retinoblastoma (Rb) ha sido ampliamente estudiado dada su importante participación como regulador negativo del ciclo celular, pero más reciente se ha demostrado que su modo de acción está relacionado con el grupo de proteínas PcG. Cada uno de los procesos que involucran a componentes de la familia de factores E2F, los miembros de Polycomb y la familia de proteína Rb, parecen ser en cierta medida independientes y, por ende, poco relacionados. sin embargo, existen evidencias de una convergencia a nivel epigenético en la acción de estos conjuntos de moléculas reguladoras de la progresión del ciclo celular y su desregulación nos puede llevar a entender mejor su contribución al desarrollo de procesos patológicos como el cáncer.
Interleukin 33 (IL33) is an inflammatory cytokine released during necrotic cell death. The epithelium and stroma of the intestine express large amounts of IL33 and its receptor St2. IL33 is therefore ...continuously released during homeostatic turnover of the intestinal mucosa. Although IL33 can prevent colon cancer associated with inflammatory colitis, the contribution of IL33 signaling to sporadic colon cancer remains unknown. Here, we utilized a mouse model of sporadic colon cancer to investigate the contribution of IL33 signaling to tumorigenesis in the absence of preexisting inflammation. We demonstrated that genetic ablation of St2 enhanced colon tumor development. Conversely, administration of recombinant IL33 reduced growth of colon cancer cell allografts. In reciprocal bone marrow chimeras, the concurrent loss of IL33 signaling within radioresistant nonhematopoietic, and the radiosensitive hematopoietic, compartments was associated with increased tumor burden. We detected St2 expression within the radioresistant mesenchymal cell compartment of the colon whose stimulation with IL33 induced expression of
NF-κB target genes. Mechanistically, we discovered that St2 deficiency within the nonhematopoietic compartment coincided with increased abundance of regulatory T cells and suppression of an IFNγ gene expression signature, whereas IL33 administration triggered IFNγ expression by tumor allograft-infiltrating T cells. The decrease of this IFNγ gene expression signature was associated with more aggressive disease in human colon cancer patients, suggesting that lack of IL33 signaling impaired the generation of a potent IFNγ-mediated antitumor immune response. Collectively, our data reveal that IL33 functions as a tumor suppressor in sporadic colon cancer.
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Histone deacetylase inhibitors (HDACi) are epigenome-targeting small molecules approved for the treatment of cutaneous T-cell lymphoma and multiple myeloma. They have also demonstrated clinical ...activity in acute myelogenous leukemia, non-small cell lung cancer, and estrogen receptor-positive breast cancer, and trials are underway assessing their activity in combination regimens including immunotherapy. However, there is currently no clear strategy to reliably predict HDACi sensitivity. In colon cancer cells, apoptotic sensitivity to HDACi is associated with transcriptional induction of multiple immediate-early (IE) genes. Here, we examined whether this transcriptional response predicts HDACi sensitivity across tumor type and investigated the mechanism by which it triggers apoptosis.
Fifty cancer cell lines from diverse tumor types were screened to establish the correlation between apoptotic sensitivity, induction of IE genes, and components of the intrinsic apoptotic pathway.
We show that sensitivity to HDACi across tumor types is predicted by induction of the IE genes
, and
, but that only
is required for HDACi-induced apoptosis. We further demonstrate that the proapoptotic function of ATF3 is mediated through direct transcriptional repression of the prosurvival factor
These findings provided the rationale for dual inhibition of HDAC and BCL-X
, which we show strongly cooperate to overcome inherent resistance to HDACi across diverse tumor cell types.
These findings explain the heterogeneous responses of tumor cells to HDACi-induced apoptosis and suggest a framework for predicting response and expanding their therapeutic use in multiple cancer types.
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