Functional analysis reveals driver cooperativity and novel mechanisms in endometrial carcinogenesis

Data availability Microarray data from this study have been deposited in GEO under accession number GSE232356: https://www.ncbi.nlm.nih.gov/geo/query/acc.cgi?acc=GSE232356.For more information: Author website: https://www.well.ox.ac.uk/research/research-groups/church-group . Endometrial cancer driver mutations: https://www.intogen.org/search?cancer=UCEC . Endometrial cancer information and patient support: https://peachestrust.org .Supporting Information is available online at: https://www.embopress.org/doi/full/10.15252/emmm.202217094#support-information-section .Copyright © 2023 The Authors. High-risk endometrial cancer has poor prognosis and is increasing in incidence. However, understanding of the molecular mechanisms which drive this disease is limited. We used genetically engineered mouse models (GEMM) to determine the functional consequences of missense and loss of function mutations in Fbxw7, Pten and Tp53, which collectively occur in nearly 90% of high-risk endometrial cancers. We show that Trp53 deletion and missense mutation cause different phenotypes, with the latter a substantially stronger driver of endometrial carcinogenesis. We also show that Fbxw7 missense mutation does not cause endometrial neoplasia on its own, but potently accelerates carcinogenesis caused by Pten loss or Trp53 missense mutation. By transcriptomic analysis, we identify LEF1 signalling as upregulated in Fbxw7/FBXW7-mutant mouse and human endometrial cancers, and in human isogenic cell lines carrying FBXW7 mutation, and validate LEF1 and the additional Wnt pathway effector TCF7L2 as novel FBXW7 substrates. Our study provides new insights into the biology of high-risk endometrial cancer and suggests that targeting LEF1 may be worthy of investigation in this treatment-resistant cancer subgroup.Cancer Research UK (CRUK). Grant Number: C26642/A27963; KWF Kankerbestrijding; HHS¦NIH¦Office of Extramural Research, National Institutes of Health (OER). Grant Numbers: RO1 HD042311, Z1AES103311; Medical Research Council; Oxford NIHR Biomedical Research Centre (BRC); Verein zur F#x00F6;rderung von Wissenschaft und Forschung an der Medizinischen Fakult#x00E4;t der LMU M#x00FC;nchen e.. Grant Number: 203141/Z/16/Z; Wellcome Trust (WT)

The transcriptional repressor Blimp1/PRDM1 regulates the maternal decidual response in mice

The transcriptional repressor Blimp1 controls cell fate decisions in the developing embryo and adult tissues. Here we describe Blimp1 expression and functional requirements within maternal uterine tissues during pregnancy. Expression is robustly up-regulated at early post-implantation stages in the primary decidual zone (PDZ) surrounding the embryo. Conditional inactivation results in defective formation of the PDZ barrier and abnormal trophectoderm invasion. RNA-Seq analysis demonstrates down-regulated expression of genes involved in cell adhesion and markers of decidualisation. In contrast, genes controlling immune responses including IFNγ are up-regulated. ChIP-Seq experiments identify candidate targets unique to the decidua as well as those shared across diverse cell types including a highly conserved peak at the Csf-1 gene promoter. Interestingly Blimp1 inactivation results in up-regulated Csf1 expression and macrophage recruitment into maternal decidual tissues. These results identify Blimp1 as a critical regulator of tissue remodelling and maternal tolerance during early stages of pregnancy

A mouse model for endometrioid ovarian cancer arising from the distal oviduct

Ovarian cancer is the deadliest gynecological malignancy in Western countries. Early detection, however, is hampered by the fact that the origin of ovarian cancer remains unclear. Knowing that in a high percentage of endometrioid ovarian cancers Wnt/beta-catenin signaling is activated, and in view of the hypothesis that ovarian cancer may originate from the distal oviduct, we studied mice in which Wnt/beta-catenin signaling was activated in Mullerian duct-derived tissues. Conditional adenomatous polyposis coli (Apc) knockout mice were used to study the activation of Wnt/beta-catenin signaling in Mullerian duct-derived organs. These Pgr(Cre/+); Apc(ex15lox/lox) mice (n = 44) were sacrificed at 10, 20, 40 and 80 weeks and uterus, oviduct, ovaries and surrounding fat tissues were assessed using immunohistochemistry. Using nuclear beta-catenin staining, Wnt/beta-catenin signaling activation was confirmed in the entire epithelium of the adult Mullerian duct (fimbriae, oviduct and endometrium), but was absent in ovarian surface epithelium cells (OSEs). Besides endometrial hyperplasia, in 87.2% of mice intraepithelial lesions of the distal oviduct were found, whereas OSEs remained unaffected. In addition, 62.5% of mice developed tumors in the distal and fimbrial part of the oviduct. In the ovaries, mainly at young age, in 16.3% of mice, simple epithelial cysts were noted, which developed further into endometrioid ovarian tumors, resembling human endometrioid ovarian cancer (27.9% of mice). Next to this, locoregional growth in the utero-ovarian ligament was also shown. Here, for the first time, mutations (activation of Wnt/beta-catenin) in the distal oviduct result in precursor lesions that develop into ovarian tumors, resembling human endometrioid ovarian cancer

Loss of APC function in mesenchymal cells surrounding the Mullerian duct leads to myometrial defects in adult mice

The WNT signal transduction pathway plays a rate limiting role in early development of many different organs. To study the functional consequences of constitutive activation of the canonical WNT pathway in the developing uterus, we generated a novel mouse model where loss of the tumor suppressor gene Apc was induced. A mouse model was generated and evaluated where Amhr2(Cre/+) driven loss of Apc exon 15 was induced. The Apc recombination was detected mainly in the myometrial layer of the adult uterus. A significant loss of muscle fibers in myometrium was apparent, though with very few muscle cells earmarked by nuclear beta-catenin. The finding was confirmed in the Pgr(Cre/+);Apc(15lox/15lox) mouse model. Loss of APC function in mesenchymal cells surrounding the fetal Mullerian ducts results in severe defects in the myometrial layers of the uterus in adult mice, suggesting that the WNT signaling pathway plays important roles in maintaining myometrial integrity. (C) 2011 Elsevier Ireland Ltd. All rights reserved

THE RAT PROBASIN GENE PROMOTER DIRECTS HORMONALLY AND DEVELOPMENTALLY-REGULATED EXPRESSION OF A HETEROLOGOUS GENE SPECIFICALLY TO THE PROSTATE IN TRANSGENIC MICE

An expression cassette carrying 426 basepairs of the rat probasin (PB) gene promoter and 28 basepairs of 5’-untranslated region is sufficient to target the expression of the bacterial chloramphenicol acetyltransferase (CAT) gene specifically to the prostate in transgenic mice. The PB-CAT transgene was expressed in three of five (60%) independent lines of mice, and this expression, as reported previously for the endogenous rat gene, was male specific, restricted primarily to the lateral, dorsal, and ventral lobes of the prostate, with only very low levels of CAT activity detected in the anterior prostate and seminal vesicles. The developmental and hormonal regulation of the transgene also paralleled that reported for the rat gene, with a 70-fold increase in CAT activity in the mouse prostate observed between 2-7 weeks of age, a time corresponding to sexual maturation. PB-CAT activity in the prostate declined after castration to 3.5% of the precastration level, and the CAT activity in castrated males approached precastration levels when mice were supplemented with testosterone. Transgene expression in castrated males was not induced by dexamethasone. Coinjection of PB-CAT with a chicken lysozyme gene matrix attachment region resulted in their cointegration and further restricted the pattern of PB-CAT to the dorsolateral prostate, with suppressed expression observed in the ventral prostate. These studies demonstrate that a minimal rat probasin promoter can target heterologous gene expression specifically to the prostate in a developmentally and hormonally regulated fashion