In some organs, adult stem cells are uniquely poised to serve as cancer cells of origin. It is unclear, however, whether tumorigenesis is influenced by the activation state of the adult stem cell. Hair follicle stem cells (HFSCs) act as cancer cells of origin for cutaneous squamous cell carcinoma and undergo defined cycles of quiescence and activation. The data presented here show that HFSCs are unable to initiate tumours during the quiescent phase of the hair cycle, indicating that the mechanisms that keep HFSCs dormant are dominant over the gain of oncogenes (such as Ras) or the loss of tumour suppressors (such as p53). Furthermore, Pten activity is necessary for quiescence-based tumour suppression, as its deletion alleviates tumour suppression without affecting proliferation. These data demonstrate that stem cell quiescence is a form of tumour suppression in HFSCs, and that Pten plays a role in maintaining quiescence in the presence of tumorigenic stimuli.
The cancer stem cell (CSC) model depicts that tumors are hierarchically organized and maintained by CSCs lying at the apex. CSCs have been “identified” in a variety of tumors through the tumor-forming assay, in which tumor cells distinguished by a certain cell surface marker (known as a CSC marker) were separately transplanted into immunodeficient mice. In such assays, tumor cells positive but not negative for the CSC marker (hereby defined as CSC(+) and CSC(-) cells, respectively) have the ability of tumor-forming and generating both progenies. However, here we show that CSC(+) and CSC(-) cells exhibit similar proliferation in the native states. Using a cell tracing method, we demonstrate that CSC(-) cells exhibit similar tumorigenesis and proliferation as CSC(+) cells when they were co-transplanted into immunodeficient mice. Through serial single-cell derived subline construction, we further demonstrated that CSC(+) and CSC(-) cells from CSC marker expressing tumors could invariably generate both progenies, and their characteristics are maintained among different generations irrespective of the origins (CSC(+)-derived or CSC(-)-derived). These findings demonstrate that tumorigenic cells cannot be distinguished by common CSC markers alone and we propose that cautions should be taken when using these markers independently to identify cancer stem cells due to the phenotypic plasticity of tumor cells.
The asymmetric total synthesis of cyclic depsipeptide BE-43547A₂ was achieved in 15 linear steps on a 350 mg scale in one batch. Our synthesis is featured with highly diastereoselective construction of α-hydroxy-β-ketoamide via α-hydroxylation with a d.r. up to 86:1. BE-43547A₂ can significantly reduce the percentage of pancreatic cancer stem cells in Panc-1 cells, and dramatically ablate the tumorsphere forming capability of Panc-1 cells. The tumor-initiating assay in-vivo, a gold standard for cancer stem cell assays, confirmed BE-43547A₂ could abolish the tumorigenesis of Panc-1 cells. The anti-PCSC activity of BE-43547A₂ will make this depsipeptide scaffold a start for discovering new PCSC-targeting drug.
Canonical Wnt/β-catenin signalling is essential for maintaining intestinal stem cells, and its constitutive activation has been implicated in colorectal carcinogenesis. We and others have previously identified Traf2- and Nck-interacting kinase (TNIK) as an essential regulatory component of the T-cell factor-4 and β-catenin transcriptional complex. Consistent with this, Tnik-deficient mice are resistant to azoxymethane-induced colon tumorigenesis, and Tnik(-/-)/Apc(min/+) mutant mice develop significantly fewer intestinal tumours. Here we report the first orally available small-molecule TNIK inhibitor, NCB-0846, having anti-Wnt activity. X-ray co-crystal structure analysis reveals that NCB-0846 binds to TNIK in an inactive conformation, and this binding mode seems to be essential for Wnt inhibition. NCB-0846 suppresses Wnt-driven intestinal tumorigenesis in Apc(min/+) mice and the sphere- and tumour-forming activities of colorectal cancer cells. TNIK is required for the tumour-initiating function of colorectal cancer stem cells. Its inhibition is a promising therapeutic approach.
Carcinogenesis is a complex process involving in genotoxic and non-genotoxic pathways. Carcinogenic potential of AgNPs has been predicted by genotoxic effects using several in vitro and in vivo models. However, there is no little information on non-genotoxic effects of AgNPs for carcinogenesis. In vitro cell transformation assay (CTA) can provide specific and sensitive evidence to predict the tumorigenic potential of a chemical, which cannot be supplied by genotoxicity testing. Therefore, we carried out CTA in Balb/c 3T3 A31-1-1 cells to evaluate the carcinogenic potential of silver nanoparticle (AgNPs). Colony forming efficiency (CFE) assay, and crystal violet (CV) assay were carried out to find cytotoxicity of AgNPs. Cytokinesis-block micronucleus assay (CBMN) and CTA in Balb/c 3T3 A31-1-1 cells were performed to predict in vitro carcinogenic potential of AgNPs. In CBMN assay, AgNPs (10.6 ug/mL) induced a significant increase of the micronucleus formation indicating that AgNPs had genotoxicity and could be an initiator for carcinogenesis. In CTA assay to assess carcinogenic potential of AgNPs, cells exposed to AgNPs for 72 h significantly induced morphological neoplastic transformation at all treated doses (0.17, 0.66, 2.65, 5.3, and 10.6 ug/mL) and Tf (transformation frequency) showed a significant increase in a dose-dependent manner. These results indicated that short-term exposure (72 h) to AgNPs had in vitro carcinogenetic potency in Balb/c 3T3 A31-1-1 cells.
NLRP3 inflammasome activation promotes inflammation-induced carcinogenesis in head and neck squamous cell carcinoma
- Journal of experimental & clinical cancer research : CR
- Published 3 months ago
NLRP3 inflammasome acts as a danger signal sensor that triggers and coordinates the inflammatory response. However, the roles of NLRP3 inflammasome in the tumorigenesis and development of cancer stem cells (CSCs) of squamous cell carcinoma of the head and neck (SCCHN) remain ambiguous.
We aimed to characterise the microbial changes associated with histological stages of gastric tumourigenesis.
The effects of Korean solar salt on an azoxymethane (AOM)/dextran sodium sulfate (DSS)-induced colon cancer C57BL/6 mouse model were studied. Korean solar salt samples (SS-S, solar salt from S salt field; SS-Yb, solar salt from Yb salt field), nine-time-baked bamboo salt (BS-9x, made from SS-Yb), purified salt (PS), and SS-G (solar salt from Guérande, France) were orally administered at a concentration of 1% during AOM/DSS colon cancer induction, and compared for their protective effects during colon carcinogenesis in C57BL/6 mice. SS-S and SS-Yb suppressed colon length shortening and tumor counts in mouse colons. Histological evaluation by hematoxylin and eosin staining also revealed suppression of tumorigenesis by SS-S. Conversely, PS and SS-G did not show a similar suppressive efficacy as Korean solar salt. SS-S and SS-Yb promoted colon mRNA expression of an apoptosis-related factor and cell-cycle-related gene and suppressed pro-inflammatory factor. SS-Yb baked into BS-9x further promoted these anti-carcinogenic efficacies. Taken together, the results indicate that Korean solar salt, especially SS-S and SS-Yb, exhibited anti-cancer activity by modulating apoptosis- and inflammation-related gene expression during colon carcinogenesis in mice, and bamboo salt baked from SS-Yb showed enhanced anti-cancer functionality.
A role for iron in carcinogenesis is supported by evidence that iron metabolism proteins are modulated in cancer progression. To date however, the expression of IRP2 (Iron Regulatory Protein-2), which is known to regulate several iron metabolism proteins, has not been assessed in colorectal cancer. Expression of IRP2 was assessed by qRT-PCR and immunohistochemistry in human colorectal cancer tissue. By interrogating The Cancer Genome Atlas (TCGA) database, expression of IRP2 and transferrin receptor-1 (TfR1) was assessed relative to common mutations that are known to occur in cancer. The impact of suppressing IRP2 on cellular iron metabolism was also determined by using siRNA and by using the MEK inhibitor trametinib. IRP2 was overexpressed in colorectal cancer compared to normal colonic mucosa and its expression was positively correlated with TfR1 expression. In addition, IRP2 expression was associated with mutations in BRAF. The MEK inhibitor trametinib suppressed IRP2 and this was associated with a suppression in TfR1 and the labile iron pool (LIP). Moreover, EGF stimulation resulted in decreased ferritin expression and an increase in the LIP which were independent of IRP2. Results presented here suggest that ablating IRP2 provides a therapeutic platform for intervening in colorectal tumorigenesis. This article is protected by copyright. All rights reserved.
Compelling evidence have demonstrated that bulk tumors can arise from a unique subset of cells commonly termed “cancer stem cells” that has been proposed to be a strong driving force of tumorigenesis and a key mechanism of therapeutic resistance. Recent advances in epigenomics have illuminated key mechanisms by which epigenetic regulation contribute to cancer progression. In this review, we present a discussion of how deregulation of various epigenetic pathways can contribute to cancer initiation and tumorigenesis, particularly with respect to maintenance and survival of cancer stem cells. This information, together with several promising clinical and preclinical trials of epigenetic modulating drugs, offer new possibilities for targeting cancer stem cells as well as improving cancer therapy overall.