The intestine‐specific caudal‐related homeobox gene‐2 (CDX2) homeobox gene, while being a tumor suppressor in the gut, is ectopically expressed in a large proportion of acute leukemia and is ...associated with poor prognosis. Here, we report that turning on human CDX2 expression in the hematopoietic lineage of mice induces acute monoblastic leukemia, characterized by the decrease in erythroid and lymphoid cells at the benefit of immature monocytic and granulocytic cells. One of the highly stimulated genes in leukemic bone marrow cells was BMP and activin membrane‐bound inhibitor (Bambi), an inhibitor of transforming growth factor‐β (TGF‐β) signaling. The CDX2 protein was shown to bind to and activate the transcription of the human BAMBI promoter. Moreover, in a leukemic cell line established from CDX2‐expressing mice, reducing the levels of CDX2 or Bambi stimulated the TGF‐β‐dependent expression of Cd11b, a marker of monocyte maturation. Taken together, this work demonstrates the strong oncogenic potential of the homeobox gene CDX2 in the hematopoietic lineage, in contrast with its physiological tumor suppressor activity exerted in the gut. It also reveals, through BAMBI and TGF‐β signaling, the involvement of CDX2 in the perturbation of the interactions between leukemia cells and their microenvironment.
Abnormal expression of the homeodomain transcription factor caudal‐related homeobox gene‐2 (CDX2) is associated with poor prognosis of leukemia patients. Here, we report that turning on human CDX2 expression in the hematopoietic lineage of mice induces acute monoblastic leukemia, through inhibition of the lymphocytic lineage and accumulation of immature monoblasts mediated by the stimulation of the BMP and activin membrane‐bound inhibitor that blocked transforming growth factor‐β‐dependent differentiation of monocytes.
The THRA gene, encoding the thyroid hormone nuclear receptor TRα1, is expressed in an increasing gradient at the bottom of intestinal crypts, overlapping with high Wnt and Notch activities. ...Importantly, THRA is upregulated in colorectal cancers, particularly in the high‐Wnt molecular subtype. The basis of this specific and/or altered expression pattern has remained unknown. To define the mechanisms controlling THRA transcription and TRα1 expression, we used multiple in vitro and ex vivo approaches. Promoter analysis demonstrated that transcription factors important for crypt homeostasis and altered in colorectal cancers, such as transcription factor 7‐like 2 (TCF7L2; Wnt pathway), recombining binding protein suppressor of hairless (RBPJ; Notch pathway), and homeobox protein CDX2 (epithelial cell identity), modulate THRA activity. Specifically, although TCF7L2 and CDX2 stimulated THRA, RBPJ induced its repression. In‐depth analysis of the Wnt‐dependent increase showed direct regulation of the THRA promoter in cells and of TRα1 expression in murine enteroids. Given our previous results on the control of the Wnt pathway by TRα1, our new results unveil a complex regulatory loop and synergy between these endocrine and epithelial‐cell‐intrinsic signals. Our work describes, for the first time, the regulation of the THRA gene in specific cell and tumor contexts.
This study demonstrates the Wnt/β‐catenin‐dependent control of the THRA gene, encoding the thyroid hormone nuclear receptor TRα1, in normal colon and colon tumors. THRA gene transcription and TRα1 expression are directly regulated by the β‐catenin/TCF complex. The induction of the complex upon APC mutation (Wnt‐up) increases TRα1 expression in cancers.
Background & Aims: The Cdx2 homeobox gene exerts multiple functions including trophectoderm specification, antero-posterior patterning, and determination of intestinal identity. The aim of this study ...was to map genomic regions that regulate the transcription of Cdx2 , with a particular interest in the gut. Methods: Genomic fragments covering 13 kilobase (kb) of the mouse Cdx2 locus were analyzed in transgenic mice and in cell assays. Results: No fragment was active in the trophectoderm. Fragments containing the first intron and extending up to −5-kb upstream of the transcription start site became active posteriorly at gastrulation and then inactive at midgestation in every tissue including the endoderm. Specific persistence of activity in the intestinal endoderm/epithelium beyond midgestation requires extending the genomic fragment up to −9 kb. We identified a 250-base pair segment around −8.5-kb binding and responding to endodermal factors, with a stimulatory effect exerted synergistically by HNF4α, GATA6, Tcf4, and β-catenin. These factors were able to activate endogenous expression of Cdx2 in nonintestinal Hela cells. Conclusions: Multiple regulatory regions control the complex developmental pattern of Cdx2 , including far upstream sequences required for the persistence of gene expression specifically in the gut epithelium throughout life. Cooperation between HNF4α, GATA6, β-catenin, and Tcf4 contributes to the intestine-specific expression of Cdx2.
Oncogenic alterations underlying B-cell acute lymphoblastic leukemia (B-ALL) in adults remain incompletely elucidated. To uncover novel oncogenic drivers, we performed RNA sequencing and whole-genome ...analyses in a large cohort of unresolved B-ALL. We identified a novel subtype characterized by a distinct gene expression signature and the unique association of 2 genomic microdeletions. The 17q21.31 microdeletion resulted in a UBTF::ATXN7L3 fusion transcript encoding a chimeric protein. The 13q12.2 deletion resulted in monoallelic ectopic expression of the homeobox transcription factor CDX2, located 138 kb in cis from the deletion. Using 4C-sequencing and CRISPR interference experiments, we elucidated the mechanism of CDX2 cis-deregulation, involving PAN3 enhancer hijacking. CDX2/UBTF ALL (n = 26) harbored a distinct pattern of additional alterations including 1q gain and CXCR4 activating mutations. Within adult patients with Ph− B-ALL enrolled in GRAALL trials, patients with CDX2/UBTF ALL (n = 17/723, 2.4%) were young (median age, 31 years) and dramatically enriched in females (male/female ratio, 0.2, P = .002). They commonly presented with a pro-B phenotype ALL and moderate blast cell infiltration. They had poor response to treatment including a higher risk of failure to first induction course (19% vs 3%, P = .017) and higher post-induction minimal residual disease (MRD) levels (MRD ≥ 10−4, 93% vs 46%, P < .001). This early resistance to treatment translated into a significantly higher cumulative incidence of relapse (75.0% vs 32.4%, P = .004) in univariate and multivariate analyses. In conclusion, we discovered a novel B-ALL entity defined by the unique combination of CDX2 cis-deregulation and UBTF::ATXN7L3 fusion, representing a high-risk disease in young adults.
•CDX2 cis-deregulation and UBTF::ATXN7L3 fusion driven by focal deletions define a novel subtype of B-ALL.•CDX2/UBTF::ATXN7L3 is a high-risk B-ALL subtype in young adults, which warrants improved therapeutic strategies.
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Whether a gene involved in distinct tissue or cell functions exerts a core of common molecular activities is a relevant topic in evolutionary, developmental, and pathological perspectives. Here, we ...addressed this question by focusing on the transcription factor and regulator of chromatin accessibility encoded by the Cdx2 homeobox gene that plays important functions during embryonic development and in adult diseases. By integrating RNAseq data in mouse embryogenesis, we unveiled a core set of common genes whose expression is responsive to the CDX2 homeoprotein during trophectoderm formation, posterior body elongation and intestinal specification. ChIPseq data analysis also identified a set of common chromosomal regions targeted by CDX2 at these three developmental steps. The transcriptional core set of genes was then validated with transgenic mouse models of loss or gain of function of Cdx2. Finally, based on human cancer data, we highlight the relevance of these results by displaying a significant number of human orthologous genes to the core set of mouse CDX2-responsive genes exhibiting an altered expression along with CDX2 in human malignancies.
The homeoprotein encoded by the intestinal-specific Cdx2 gene is a major regulator of gut development and homeostasis,also involved in colon cancer as well as in intestinal-type metaplasias when it ...is abnormally expressed outside the gut.At the molecular level,structure/function studies have demonstrated that the Cdx2 protein is a transcription factor containing a conserved homeotic DNA-binding domain made ofthree alpha helixes arranged in a helix-turn-helix motif,preceded by a transcriptional domain and followed by a regulatory domain.The protein interacts with several thousand sites on the chromatin and widely regulates intestinal functions in stem/progenitor cells as well as in mature differentiated cells.Yet,this transcription factor also acts trough original nontranscriptional mechanisms.Indeed,the identification of novel protein partners of Cdx2 and also of a splicing variant revealed unexpected functions in the control of signaling pathways like the Wnt and NF-k B pathways,in double-strand break DNA repair and in premessenger RNA splicing.These novel functions of Cdx2 must be considered to fully understand the complexity of the role of Cdx2 in the healthy intestine and in diseases.
On the basis of phylogenetic analyses, we uncovered a variant of the CDX2 homeobox gene, a major regulator of the development and homeostasis of the gut epithelium, also involved in cancer. This ...variant, miniCDX2, is generated by alternative splicing coupled to alternative translation initiation, and contains the DNA-binding homeodomain but is devoid of transactivation domain. It is predominantly expressed in crypt cells, whereas the CDX2 protein is present in crypt cells but also in differentiated villous cells. Functional studies revealed a dominant-negative effect exerted by miniCDX2 on the transcriptional activity of CDX2, and conversely similar effects regarding several transcription-independent functions of CDX2. In addition, a regulatory role played by the CDX2 and miniCDX2 homeoproteins on their pre-mRNA splicing is displayed, through interactions with splicing factors. Overexpression of miniCDX2 in the duodenal Brunner glands leads to the expansion of the territory of these glands and ultimately to brunneroma. As a whole, this study characterized a new and original variant of the CDX2 homeobox gene. The production of this variant represents not only a novel level of regulation of this gene, but also a novel way to fine-tune its biological activity through the versatile functions exerted by the truncated variant compared to the full-length homeoprotein. This study highlights the relevance of generating protein diversity through alternative splicing in the gut and its diseases.
The gravity of colorectal cancer is mainly due to the capacity of tumor cells to migrate out of the tumor mass to invade the stroma and disseminate as metastases. The acquisition of a migratory ...phenotype also occurs during wound healing. Here, we show that several features characterizing invasive colon tumor cells are shared by migrating cells during wound repair in vitro. In particular, the expression of the intestine-specific transcription factor Cdx2, a key gene for intestinal identity downregulated in invasive cancer cells, is reduced during wound healing in vitro. Transcription factors involved in epithelial-mesenchymal transition such as Snail and Slug are upregulated during wound healing and are able to repress Cdx2 transcription. In vitro, forced expression of Cdx2 in human colon cancer cell lines retarded wound repair and reduced migration, whereas inhibition of Cdx2 expression by RNA interference enhanced migration. In vivo, forced expression of Cdx2 opposed tumor cells spreading in nude mice xenografted at three different sites. These data provide evidence that Cdx2 antagonizes the process of tumor cell dissemination, and they suggest that this homeobox gene might represent a new therapeutic target against metastatic spreading of colon cancer.
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