SUMMARY A large proportion of colorectal cancers (CRCs) display mutational inactivation of the TGF-beta pathway yet paradoxically, they are characterized by elevated TGF-beta production. Here, we unveil a prometastatic programme induced by TGF-beta in the microenvironment that associates with a high-risk of CRC relapse upon treatment. The activity of TGF-beta on stromal cells increases the efficiency of organ colonization by CRC cells whereas mice treated with a pharmacological inhibitor of TGFBR1 are resilient to metastasis formation. Secretion of IL11 by TGF-beta-stimulated cancer-associated fibroblasts (CAFs) triggers GP130/STAT3 signalling in tumour cells. This crosstalk confers a survival advantage to metastatic cells. The dependency on the TGF-beta stromal programme for metastasis initiation could be exploited to improve the diagnosis and treatment of CRC.

In a genome-wide screen for microRNAs regulated by the transcription factor encoded by the p53 tumor suppressor gene we found that after p53-activation the abundance of thirty-four miRNAs was significantly increased, whereas sixteen miRNAs were suppressed. The induction of miR-34a was most pronounced among all differential regulations. Also expression of the primary miR-34a transcript was induced after p53 activation and by DNA damage in a p53-dependent manner. p53 occupied an evolutionarily conserved binding site proximal to the first non-coding exon of miR-34a. Ectopic miR-34a induced apoptosis and a cell cycle arrest in the G1-phase, thereby suppressing tumor cell proliferation. Other p53-induced miRNAs identified here may also have tumor suppressive potential as they are known to suppress the anti-apoptotic factor Bcl2 (miR-15a/16) and the oncogenes RAS and HMGA2 (let-7a). Our results for the first time directly integrate the regulation of miRNA expression into the transcriptional network regulated by p53. siRNAs corresponding to p53-induced miRNAs may have potential as cancer therapeutic agents as RNA interference based therapies are currently emerging.

A frequent complication in colorectal cancer (CRC) is regeneration of the tumor after therapy. Here, we report that a gene signature specific for adult intestinal stem cells (ISCs) predicts disease relapse in CRC patients. ISCs are marked by high expression of the EphB2 receptor, which becomes gradually silenced as cells differentiate. Using EphB2 and the ISC marker Lgr5, we have FACS-purified and profiled mouse ISCs, crypt proliferative progenitors, and late transient amplifying cells to define a gene program specific for normal ISCs. Furthermore, we discovered that ISC-specific genes identify a stem-like cell population positioned at the bottom of tumor structures reminiscent of crypts. EphB2 sorted ISC-like tumor cells display robust tumor-initiating capacity in immunodeficient mice as well as long-term self-renewal potential. Taken together, our data suggest that the ISC program defines a cancer stem cell niche within colorectal tumors and plays a central role in CRC relapse.

Here we describe the isolation of stem cells of the human colonic epithelium. Differential cell surface abundance of ephrin type-B receptor 2 (EPHB2) allows the purification of different cell types from human colon mucosa biopsies. The highest EPHB2 surface levels correspond to epithelial colonic cells with the longest telomeres and elevated expression of intestinal stem cell (ISC) marker genes. Moreover, using culturing conditions that recreate the ISC niche, a substantial proportion of EPHB2-high cells can be expanded in vitro as an undifferentiated and multipotent population.

In the majority of human tumors, expression of the c-MYC oncogene becomes constitutive. Here, we report that c-MYC directly regulates the expression of AP4 via CACGTG motifs in the first intron of the AP4 gene. Induction of AP4 was required for c-MYCmediated cell cycle reentry of anti-estrogen arrested breast cancer cells and mitogen-mediated repression of the CDK inhibitor p21. AP4 directly repressed p21 by occupying four CAGCTG motifs in the p21 promoter via its basic region. AP4 levels declined after DNA damage, and ectopic AP4 interfered with p53-mediated cell cycle arrest and sensitized cells to apoptosis induced by DNA damaging agents. AP4 expression blocked induction of p21 by TGF-␤ in human keratinocytes and interfered with up-regulation of p21 and cell cycle arrest during monoblast differentiation. Notably, AP4 is specifically expressed in colonic progenitor and colorectal carcinoma cells. In conclusion, our results indicate that c-MYC employs AP4 to maintain cells in a proliferative, progenitor-like state.colorectal cancer ͉ DNA damage ͉ p53 ͉ progenitor cells ͉ TGF-beta

Background and objective: The aim of the Pulmonary Rehabilitation Guidelines (Guidelines) is to provide evidence-based recommendations for the practice of pulmonary rehabilitation (PR) specific to Australian and New Zealand healthcare contexts.

ObjectiveUC is a chronic inflammatory disease of the colonic mucosa. Growing evidence supports a role for epithelial cell defects in driving pathology. Moreover, long-lasting changes in the epithelial barrier have been reported in quiescent UC. Our aim was to investigate whether epithelial cell defects could originate from changes in the epithelial compartment imprinted by the disease.DesignEpithelial organoid cultures (EpOCs) were expanded ex vivo from the intestinal crypts of non-IBD controls and patients with UC. EpOCs were induced to differentiate (d-EpOCs), and the total RNA was extracted for microarray and quantitative real-time PCR (qPCR) analyses. Whole intestinal samples were used to determine mRNA expression by qPCR, or protein localisation by immunostaining.ResultsEpOCs from patients with UC maintained self-renewal potential and the capability to give rise to differentiated epithelial cell lineages comparable with control EpOCs. Nonetheless, a group of genes was differentially regulated in the EpOCs and d-EpOCs of patients with UC, including genes associated with antimicrobial defence (ie, LYZ, PLA2G2A), with secretory (ie, ZG16, CLCA1) and absorptive (ie, AQP8, MUC12) functions, and with a gastric phenotype (ie, ANXA10, CLDN18 and LYZ). A high rate of concordance was found in the expression profiles of the organoid cultures and whole colonic tissues from patients with UC.ConclusionsPermanent changes in the colonic epithelium of patients with UC could be promoted by alterations imprinted in the stem cell compartment. These changes may contribute to perpetuation of the disease.

The transcription factor AP4 is a critical regulator of epithelial–mesenchymal transition, migration, invasion, and metastasis in colorectal cancer cells.