521 research outputs found
Correction: Teeuwssen and fodde; colon cancer heterogeneity and phenotypic plasticity in metastasis formation (Cancers (2019) 11, 9, 1368)
The authors would like to make a correction to their published paper [1]. The authors would like to change one incorrect sentence in reference [1]. On page 9, in paragraph 2, the sentence "In colon cancer, CAFs release exosomes containing miR-92a-3p and promote invasion and chemotherapy resistance. miR-92a-3p directly binds to FBXW7 and MOAP1 thereby activating Wnt-induced EMT and mitochondrial apoptosis [89]'should be changed to "In colon cancer, CAFs release exosomes containing miR-92a-3p and promote invasion and chemotherapy resistance. miR-92a-3p directly binds to FBXW7 and MOAP1 thereby activating Wnt-induced EMT and inhibiting mitochondrial apoptosis [89]." The change does not affect the scientific results. The rest of the manuscript does not to be changed. The authors would like to apologize for any inconvenience caused. The manuscript will be updated, and the original will remain available on the article webpage
Evidence for Msh2 haploinsufficiency in mice revealed by MNU-induced sister-chromatid exchange analysis
The role of Msh2 in chromosome stability has been investigated in a targeted mouse model for HNPCC Msh2Ξ7N. Chromosome aberration frequencies were similar in bone marrow of Msh2+/+Msh2+/βand Msh2β/βmice and no differential effects of in vivo X-irradiation were noted. By contrast, the induction of sister-chromatid exchanges (SCEs) by methyl nitrosourea (MNU) was reduced in Msh2β/βand Msh2+/βcells to ~20% and ~45% wild-type levels respectively indicating a phenotypic effect of haploinsufficiency of the mouse Msh2 gene. Β© 2000 CancerResearch Campaig
Stochastic model of transcription factor-regulated gene expression
We consider a stochastic model of transcription factor (TF)-regulated gene
expression. The model describes two genes: Gene A and Gene B which synthesize
the TFs and the target gene proteins respectively. We show through analytic
calculations that the TF fluctuations have a significant effect on the
distribution of the target gene protein levels when the mean TF level falls in
the highest sensitive region of the dose-response curve. We further study the
effect of reducing the copy number of Gene A from two to one. The enhanced TF
fluctuations yield results different from those in the deterministic case. The
probability that the target gene protein level exceeds a threshold value is
calculated with a knowledge of the probability density functions associated
with the TF and target gene protein levels. Numerical simulation results for a
more detailed stochastic model are shown to be in agreement with those obtained
through analytic calculations. The relevance of these results in the context of
the genetic disorder haploinsufficiency is pointed out. Some experimental
observations on the haploinsufficiency of the tumour suppressor gene, Nkx3.1,
are explained with the help of the stochastic model of TF-regulated gene
expression.Comment: 17 pages, 11 figures. Accepted for publication in Physical Biolog
Wnt Signaling in Ovarian Cancer Stemness, EMT, and Therapy Resistance
Ovarian cancers represent the deadliest among gynecologic malignancies and are
characterized by a hierarchical structure with cancer stem cells (CSCs) endowed with self-renewal
and the capacity to differentiate. The Wnt/Ξ²-catenin signaling pathway, known to regulate stemness
in a broad spectrum of stem cell niches including the ovary, is thought to play an important role
in ovarian cancer. Importantly, Wnt activity was shown to correlate with grade, epithelial to
mesenchymal transition, chemotherapy resistance, and poor prognosis in ovarian cancer. This review
will discuss the current knowledge of the role of Wnt signaling in ovarian cancer stemness, epithelial to
mesenchymal transition (EMT), and therapy resistance. In addition, the alleged role of exosomes
in the paracrine activation of Wnt signaling and pre-metastatic niche formation will be reviewed.
Finally, novel potential treatment options based on Wnt inhibition will be highlighted
Cell heterogeneity and phenotypic plasticity in metastasis formation: The case of colon cancer
The adenoma-to-carcinoma progression in colon cancer is driven by a sequential accumulation of genetic alterations at specific tumor suppressors and oncogenes. In contrast, the multistage route from the primary site to metastasis formation is underlined by phenotypic plasticity, i.e., the capacity of disseminated tumor cells to undergo transiently and reversible transformations in order to adapt to the ever-changing environmental contexts. Notwithstanding the considerable body of evidence in support of the role played by epithelial-to-mesenchymal transition (EMT)/mesenchymal-to-epithelial transition (MET) in metastasis, its rate-limiting function, the detailed underlying cellular and molecular mechanisms, and the extension of the necessary morphologic and epigenetic changes are still a matter of debate. Rather than leading to a complete epithelial or mesenchymal state, the EMT/MET-program generates migrating cancer cells displaying intermediate phenotypes featuring both epithelial and mesenchymal characteristics. In this review, we will address the role of colon cancer heterogeneity and phenotypic plasticity in metastasis formation and the contribution of EMT to these processes. The alleged role of hybrid epithelial/mesenchymal (E/M) in collective and/or single-cell migration during local dissemination at the primary site and more systemic spreading will also be highlighted
Generation and characterization of an inducible transgenic model for studying mouse esophageal biology
Background: To facilitate the in vivo study of esophageal (stem) cell biology in homeostasis and cancer, novel mouse models are necessary to elicit expression of candidate genes in a tissue-specific and inducible fashion. To this aim, we developed and studied a mouse model to allow labeling of esophageal cells with the histone 2B-GFP (H2B-GFP) fusion protein. Results: First, we generated a transgenic mouse model expressing the reverse tetracycline transactivator rtTA2-M2 under control of the promoter (ED-L2) of the Epstein-Barr virus (EBV) gene encoding the latent membrane protein-1 (LMP-1). The newly generated ED-L2-rtTA2-M2 (ED-L2-rtTA) mice were then bred with the previously developed tetO-HIST1H2BJ/GFP (tetO-H2B-GFP) model to assess inducibility and tissue-specificity. Expression of the H2B-GFP fusion protein was observed upon doxycycline induction but was restricted to the terminally differentiated cells above the basal cell layer. To achieve expression in the basal compartment of the esophagus, we ubsequently employed a different transgenic model expressing the reverse transactivator rtTA2S-M2 under the control of the ubiquitous, methylation-free CpG island of the human hnRNPA2B1-CBX3 gene (hnRNP-rtTA). Upon doxycycline administration to the compound hnRNP-rtTA/tetO-H2B-GFP mice, near-complete labeling of all esophageal cells was achieved. Pulse-chase experiments confirmed that complete turnover of the esophageal epithelium in the adult mouse is achieved within 710 days. Conclusions: We show that the esophagus-specific promoter ED-L2 is expressed only in the differentiated cells above the basal layer. oreover, we confirmed that esophageal turn-over in the adult mouse does not exceed 710 days
A Targeted Constitutive Mutation in the Apc Tumor Suppressor Gene Underlies Mammary But Not Intestinal Tumorigenesis
Germline mutations in the adenomatous polyposis coli (APC) gene are responsible for familial adenomatous polyposis (FAP), an autosomal dominant hereditary predisposition to the development of multiple colorectal adenomas and of a broad spectrum of extra-intestinal tumors. Moreover, somatic APC mutations play a rate-limiting and initiating role in the majority of sporadic colorectal cancers. Notwithstanding its multifunctional nature, the main tumor suppressing activity of the APC gene resides in its ability to regulate Wnt/Ξ²-catenin signaling. Notably, genotypeβphenotype correlations have been established at the APC gene between the length and stability of the truncated proteins encoded by different mutant alleles, the corresponding levels of Wnt/Ξ²-catenin signaling activity they encode for, and the incidence and distribution of intestinal and extra-intestinal tumors. Here, we report a novel mouse model, Apc1572T, obtained by targeting a truncated mutation at codon 1572 in the endogenous Apc gene. This hypomorphic mutant allele results in intermediate levels of Wnt/Ξ²-catenin signaling activation when compared with other Apc mutations associated with multifocal intestinal tumors. Notwithstanding the constitutive nature of the mutation, Apc+/1572T mice have no predisposition to intestinal cancer but develop multifocal mammary adenocarcinomas and subsequent pulmonary metastases in both genders. The histology of the Apc1572T primary mammary tumours is highly heterogeneous with luminal, myoepithelial, and squamous lineages and is reminiscent of metaplastic carcinoma of the breast in humans. The striking phenotype of Apc+/1572T mice suggests that specific dosages of Wnt/Ξ²-catenin signaling activity differentially affect tissue homeostasis and initiate tumorigenesis in an organ-specific fashion
Genomic profiling by DNA amplification of laser capture microdissected tissues and array CGH.
Comparative genomic hybridization by means of BAC microarrays (array CGH)
allows high-resolution profiling of copy-number aberrations in tumor DNA.
However, specific genetic lesions associated with small but clinically
relevant tumor areas may pass undetected due to intra-tumor heterogeneity
and/or the presence of contaminating normal cells. Here, we show that the
combination of laser capture microdissection, phi29 DNA
polymerase-mediated isothermal genomic DNA amplification, and array CGH
allows genomic profiling of very limited numbers of cells. Moreover, by
means of simple statistical models, we were able to bypass the exclusion
of amplification distortions and variability prone areas, and to detect
tumor-specific chromosomal gains and losses. We applied this new combined
experimental and analytical approach to the genomic profiling of
colorectal adenomatous polyps and demonstrated our ability to accurately
detect single copy gains and losses affecting either whole chromosomes or
small genomic regions from as little as 2 ng of DNA or 1000 microdissected
cells
Familial Adenomatous Polyposis-Associated Desmoids Display Significantly More Genetic Changes than Sporadic Desmoids
Desmoid tumours (also called deep or aggressive fibromatoses) are potentially life-threatening fibromatous lesions. Hereditary desmoid tumours arise in individuals affected by either familial adenomatous polyposis (FAP) or hereditary desmoid disease (HDD) carrying germline mutations in APC. Most sporadic desmoids carry somatic mutations in CTNNB1. Previous studies identified losses on 5q and 6q, and gains on 8q and 20q as recurrent genetic changes in desmoids. However, virtually all genetic changes were derived from sporadic tumours. To investigate the somatic alterations in FAP-associated desmoids and to compare them with changes occurring in sporadic tumours, we analysed 17 FAP-associated and 38 sporadic desmoids by array comparative genomic hybridisation and multiple ligation-dependent probe amplification. Overall, the desmoids displayed only a limited number of genetic changes, occurring in 44% of cases. Recurrent gains at 8q (7%) and 20q (5%) were almost exclusively found in sporadic tumours. Recurrent losses were observed for a 700 kb region at 5q22.2, comprising the APC gene (11%), a 2 Mb region at 6p21.2-p21.1 (15%), and a relatively large region at 6q15-q23.3 (20%). The FAP-associated desmoids displayed a significantly higher frequency of copy number abnormalities (59%) than the sporadic tumours (37%). As predicted by the APC germline mutations among these patients, a high percentage (29%) of FAP-associated desmoids showed loss of the APC region at 5q22.2, which was infrequently (3%) seen among sporadic tumours. Our data suggest that loss of region 6q15-q16.2 is an important event in FAP-associated as well as sporadic desmoids, most likely of relevance for desmoid tumour progression
- β¦