Regulation of intestinal cancer stem cells

Emerging biofabrication approaches for gastrointestinal organoids towards patient specific cancer models

Tissue engineered organoids are simple biomodels that can emulate the structural and functional complexity of specific organs. Here, we review developments in three-dimensional (3D) artificial cell constructs to model gastrointestinal dynamics towards cancer diagnosis. We describe bottom-up approaches to fabricate close-packed cell aggregates, from the use of biochemical and physical cues to guide the self-assembly of organoids, to the use of engineering approaches, including 3D printing/additive manufacturing and external field-driven protocols. Finally, we outline the main challenges and possible risks regarding the potential translation of gastrointestinal organoids from laboratory settings to patient-specific models in clinical applications.

EMT-associated microRNAs and their roles in cancer stemness and drug resistance

Epithelial‐to‐mesenchymal transition (EMT) is implicated in a wide array of malignant behaviors of cancers, including proliferation, invasion, and metastasis. Most notably, previou studies have indicated that both cancer stem‐like properties and drug resistance were associated with EMT. Furthermore, microRNAs (miRNAs) play a pivotal role in the regulation of EMT phenotype, as a result, some miRNAs impact cancer stemness and drug resistance. Therefore, understanding the relationship between EMT‐associated miRNAs and cancer stemness/drug resistance is beneficial to both basic research and clinical treatment. In this review, we preliminarily looked into the various roles that the EMT‐associated miRNAs play in the stem‐like nature of malignant cells. Then, we reviewed the interaction between EMT‐associated miRNAs and the drug‐resistant complex signaling pathways of multiple cancers including lung cancer, gastric cancer, gynecologic cancer, breast cancer, liver cancer, colorectal cancer, pancreatic cancer, esophageal cancer, and nasopharyngeal cancer. We finally discussed the relationship between EMT, cancer stemness, and drug resistance, as well as looked forward to the potential applications of miRNA therapy for malignant tumors.

Research Progress on Slit/Robo Pathway in Pancreatic Cancer: Emerging and Promising

Pancreatic cancer is a highly malignant digestive system tumor which is the leading cause of cancer-related deaths. The basic and clinical research of pancreatic cancer has made great progress in recent years, and kinds of signaling pathways have been found in the tumorigenesis and progression in pancreatic cancer. The Slit glycoprotein (Slit) and Roundabout receptor (Robo) signaling pathway acts as a neural targeting factor with the axonal remnant, axon guidance, and inhibition of neuronal migration in the nervous system. In recent years, it has been found that the Slit/Robo signaling pathway has different degrees of expression changes in various tumor cells. In different tumor cells, the signaling pathway gene expression is different and regulates tumor angiogenesis, cell invasion, metastasis, and nerve infiltration. Herein, we summarize the mechanisms of the Slit/Robo pathway in the development and progression of pancreatic cancer, in order to have more understanding of the role of Slit/Robo in pancreatic cancer.

TKP, a serine protease extracted from Trichosanthes kirilowii, inhibits the migration and invasion of colorectal adenocarcinoma cells by targeting Wnt/β-catenin and Hedgehog/Gli1 signalings

Trichosanthes kirilowii, which is a type of Liana from cucurbitaceous family, possesses many bioactive constituents and therefore has multifarious pharmacological functions. TKP, which is a serine protease extracted from the fruit of Trichosanthes kirilowii, has been reported to possess potential anticancer activity. However, the effects of TKP on cancer cell migration and invasion are still unknown. Here, we reported that TKP could inhibit the migration and invasion abilities of colorectal cancer cells. In addition, the mRNA, protein expression levels, and activities of migration and invasion-related proteins MMP2 and MMP9 were decreased in TKP-treated cells. Mechanistically, TKP treatment repressed Wnt/β-catenin and Hedgehog/Gli1 signaling cascades. However, the addition of lithium chloride or the transfection of plasmid pcDNA3.1-V5-HisA-Gli1 reversed the impacts of TKP on MMP2, MMP9, cell migration, and invasion. These results indicated that TKP suppressed the migration and invasion of colorectal cancer cells through blocking Wnt/β-catenin and Hedgehog/Gli1 pathways-mediated MMP2 and MMP9.

MicroRNA Determines the Fate of Intestinal Epithelial Cell Differentiation and Regulates Intestinal Diseases

The rapid self-renewal of intestinal epithelial cells enhances intestinal function, promotes the nutritional needs of animals and strengthens intestinal barrier function to resist the invasion of foreign pathogens. MicroRNAs (miRNAs) are a class of short-chain, non-coding RNAs that regulate stem cell proliferation and differentiation by down-regulating hundreds of conserved target genes after transcription via seed pairing to the 3' untranslated regions. Numerous studies have shown that miRNAs can improve intestinal function by participating in the proliferation and differentiation of different cell populations in the intestine. In addition, miRNAs also contribute to disease regulation and therefore not only play a vital role in the gastrointestinal disease management but also act as blood or tissue biomarkers of disease. As changes to the levels of miRNAs can change cell fates, miRNA-mediated gene regulation can be used to update therapeutic strategies and approaches to disease treatment.

Production of Tissue-Engineered Small Intestine in Rats with Different Ages of Cell Donors

IMPACT STATEMENT

This study compared side-by-side the impact of donor age on the production of tissue-engineered small intestine (TESI). Each age represents a specific period of life: E18 for fetuses, 5-day-old pups for neonates, 21-day-old rats for weanlings, and 6-week-old rats for adults. The TESI produced was compared macroscopically and microscopically. The mechanism(s) contributing to the differences observed was explored by detecting proliferating cells in the TESI and by analyzing intestinal stem cell gene expression in donor cells. These data may provide valuable information for future application of TESI clinically.

Secreted AGR2 promotes invasion of colorectal cancer cells via Wnt11-mediated non-canonical Wnt signaling

Human anterior gradient-2 (AGR2), a member of protein disulfide isomerase (PDI) family, is present in both intracellular and extracellular compartments. Although AGR2 is overexpressed in various human cancers and reported to promote aggressive tumor features, little is known regarding AGR2's extracellular functions during tumorigenesis. Here, we demonstrate that secreted AGR2 promotes cell migration and metastasis of colorectal cancer (CRC) in vitro and in vivo. Mechanistically, secreted AGR2 elevated Wnt11 expression, triggering non-canonical Wnt signaling: the Ca²⁺/Calmodulin-dependent protein kinase II (CaMKII) and c-jun amino-terminal kinase (JNK) pathways. Knockdown of Wnt11 or pretreatment with CaMKII and JNK inhibitors reversed the secreted AGR2's migration-promoting effect. Further studies revealed that AGR2 antagonized canonical Wnt/β-catenin signaling via activating CaMKII. Collectively, our study uncovers a critical role of Wnt11-mediated non-canonical Wnt signaling (CaMKII and JNK pathways) in secreted AGR2's promoted migration of CRC cells. These results raise the possibility that secreted AGR2 may be a potential therapeutic target towards inhibiting CRC metastasis.

AA-NAT, MT1 and MT2 Correlates with Cancer Stem-Like Cell Markers in Colorectal Cancer: Study of the Influence of Stage and p53 Status of Tumors

The characterization of colon cancer stem cells (CSCs) may help to develop novel diagnostic and therapeutic procedures. p53 loss increases the pool of CSCs in colorectal cancer (CRC). Recent reports suggest that the oncostatic effects of melatonin could be related to its ability to kill CSCs. Although there are no data linking the loss of p53 function and melatonin synthesis or signaling in cancer, melatonin does activate the p53 tumor-suppressor pathway in this disease. In this work, we analyze whether the expression of melatonin synthesis and signaling genes are related to the expression of CSC markers and the implication of p53 status in samples from patients with CRC. Arylalkylamine N-acetyltransferase (AA-NAT), MT1, and MT2 expression decreased in tumor samples versus normal mucosa samples in mutated p53 (mtp53) tumors versus those with wild-type p53 (wtp53). Further, AA-NAT and MT2 expression were lower in advanced stages of the disease in wtp53 tumors. On the contrary, CD44 and CD66c expression was higher in tumor versus normal mucosa in wtp53 tumors. Additionally, CD44 expression was higher in advanced stages of the disease regardless of the p53 status. Patients with CD44_highCD66c_high and wtp53 tumors in advanced stages showed low expression of AA-NAT and MT2 in wtp53 tumors. These results could indicate a possible interaction of these pathways in CRC.

Regulatory miRNAs in Colorectal Carcinogenesis and Metastasis

Colorectal cancer is one of the most common malignancies and is the second-leading cause of cancer-related death world-wide, which is linked to genetic mutations, epigenetic alterations, and oncogenic signaling activation. MicroRNAs, one of the categories of epigenetics, have been demonstrated significant roles in carcinogenesis and progression through regulating of oncogenic signaling pathways, stem cells, epithelial-mesenchymal transition, and metastasis. This review summarizes the roles of microRNAs in the regulating of Wnt, Ras, TGF-β, and inflammatory signaling pathways, stemness, and epithelial-mesenchymal transition, for carcinogenesis and metastasis in colorectal cancer. Improving our understanding of the mechanisms of regulatory interactions of microRNAs with signaling pathways in colorectal cancer formation and progression will aid in determining the genes responsible for colorectal cancer initiation, progression, metastasis, and recurrence and, finally, in developing personalized approaches for cancer prevention and therapy.

Consumption of Red/Processed Meat and Colorectal Carcinoma: Possible Mechanisms Underlying the Significant Association

Epidemiology and experimental studies provide an overwhelming support of the notion that diets high in red or processed meat accompany an elevated risk of developing pre-neoplastic colorectal adenoma and frank colorectal carcinoma (CRC). The underlying mechanisms are disputed; thus several hypotheses have been proposed. A large body of reports converges, however, on haem and nitrosyl haem as major contributors to the CRC development, presumably acting through various mechanisms. Apart from a potentially higher intestinal mutagenic load among consumers on a diet rich in red/processed meat, other mechanisms involving subtle interference with colorectal stem/progenitor cell survival or maturation are likewise at play. From an overarching perspective, suggested candidate mechanisms for red/processed meat-induced CRC appear as three partly overlapping tenets: (i) increased N-nitrosation/oxidative load leading to DNA adducts and lipid peroxidation in the intestinal epithelium, (ii) proliferative stimulation of the epithelium through haem or food-derived metabolites that either act directly or subsequent to conversion, and (iii) higher inflammatory response, which may trigger a wide cascade of pro-malignant processes. In this review, we summarize and discuss major findings of the area in the context of potentially pertinent mechanisms underlying the above-mentioned association between consumption of red/processed meat and increased risk of developing CRC.

The role and mechanism of CRL4 E3 ubiquitin ligase in cancer and its potential therapy implications

CRLs (Cullin-RING E3 ubiquitin ligases) are the largest E3 ligase family in eukaryotes, which ubiquitinate a wide range of substrates involved in cell cycle regulation, signal transduction, transcriptional regulation, DNA damage response, genomic integrity, tumor suppression and embryonic development. CRL4 E3 ubiquitin ligase, as one member of CRLs family, consists of a RING finger domain protein, cullin4 (CUL4) scaffold protein and DDB1–CUL4 associated substrate receptors. The CUL4 subfamily includes two members, CUL4A and CUL4B, which share extensively sequence identity and functional redundancy. Aberrant expression of CUL4 has been found in a majority of tumors. Given the significance of CUL4 in cancer, understanding its detailed aspects of pathogenesis of human malignancy would have significant value for the treatment of cancer. Here, the work provides an overview to address the role of CRL4 E3 ubiquitin ligase in cancer development and progression, and discuss the possible mechanisms of CRL4 ligase involving in many cellular processes associated with tumor. Finally, we discuss its potential value in cancer therapy.

Dual role of CD44 isoforms in ampullary adenocarcinoma: CD44s predicts poor prognosis in early cancer and CD44ν is an indicator for recurrence in advanced cancer

Background

Although postoperative adjuvant chemoradiotherapies prevent recurrence for some patients with ampullary cancer, the recurrence rate is as high as 29 % in patients with stage I cancer. In an effort to identify predictors of recurrence in patients with ampullary adenocarcinoma, we investigated the clinical value of assessing standard and variant forms of CD44.

Methods

Immunohistochemistry staining and reverse-transcription polymerase chain reaction (RT-PCR) was used to detect standard and variant forms of CD44 in samples of ampullary adenocarcinoma. The cDNA microarray analysis comparing tumors with or without pancreatic invasion was undertaken and analyzed by Ingenuity Pathway Analysis.

Results

The standard CD44 (CD44s) isoform was detected in 76 of 98 patients with ampullary adenocarcinoma, and the negative or weak expression of CD44s was correlated with pancreatic invasion, lymphovascular invasion, advanced stage and bone metastasis. Moderate to dense expression of CD44s was correlated with shorter overall survival in patients with localized cancer (T1 or T2 disease, P = 0.0268). The patients with advanced cancer (T3 or T4 disease) and moderate or dense CD44s expression had a trend toward better survival. Alternative splicing of CD44 was confirmed using RT-PCR, which revealed that the CD44ν3-10 isoform was only expressed in patients with cancer recurrence. Fold change of CD44ν6-10 was also increased. In addition, networks containing CD44, vascular endothelial growth factor (VEGF), epidermal growth factor receptor (EGFR), transforming growth factor-β (TGF-β), matrix metalloproteinase 2 (MMP2), AKT, extracellular signal-regulated protein kinase 1 and 2 (ERK1/2), p38 MAPK, activated protein 1 (AP1)‚ and CTNNB1 were constructed after comparing microarray data from patients with and without pancreatic invasion.

Conclusions

Whereas CD44s functions as tumor-promoting oncoprotein in early localized ampullary adenocarcinoma, CD44 variants are expressed in advanced cancer and patients with recurrence. Regional invasiveness and distant metastasis of ampullary cancer is controlled by a complex interacting network.

Electronic supplementary material

The online version of this article (doi:10.1186/s12885-015-1924-3) contains supplementary material, which is available to authorized users.

Variations in genes involved in dormancy associated with outcome in patients with resected colorectal liver metastases

BACKGROUND

Tumor dormancy has been described as a state of hibernation. Dormancy can be switched to proliferation by different pathways, which may play a critical role in tumor recurrence. In this study, we investigated genetic variations within genes involved in tumor dormancy and their association with recurrence and outcome in patients with colorectal liver metastases (CLM) who underwent neoadjuvant bevacizumab-based chemotherapy.

PATIENTS AND METHODS

Genomic DNA was extracted from resected CLM (FFPE) from 149 patients. Single-nucleotide polymorphisms (SNPs) in 14 genes associated with dormancy were analyzed by direct Sanger DNA sequencing and evaluated for response, recurrence-free survival (RFS), overall survival (OS) and recurrence patterns.

RESULTS

NME1 rs34214448 C>A was significantly associated with RFS in univariable analysis (P = 0.039) and with intrahepatic recurrence (P = 0.014). NOTCH3 rs1044009 T>C and CD44 rs8193 C>T showed a significant difference in 3-year OS rates (P = 0.004 and P = 0.042, respectively). With respect to radiological response, CD44 rs8193 C>T variant genotypes were associated with a significantly higher response rate (P = 0.033). Recursive partitioning analyses revealed that Dll4 rs12441495 C>G, NME1 rs34214448 C>A and NOTCH3 rs1044009 T>C were the dominant SNPs predicting histological response, RFS and OS, respectively.

CONCLUSION

Our data suggest that gene variations within genes involved in tumor dormancy pathways are associated with response and outcome in patients with resected CLM. These data may lead to new and more effective treatment strategies targeting tumor dormancy.

Prognostic impact of histological categorisation of epithelial-mesenchymal transition in colorectal cancer

BACKGROUND

The crosstalk between cancer cells and stroma is involved in the acquired capability for metastasis through the induction of epithelial-mesenchymal transition (EMT). We aimed to clarify the prognostic value of the histological category of EMT in colorectal cancer (CRC).

METHODS

Tumour EMT was graded into one of three histological categories on the basis of integrated assessment of poorly differentiated clusters and pro-EMT desmoplasia at the leading edge of the primary tumour (Histology(EMT)). Stage II and III CRC patients (cohort 1, N=500) and stage IV patients (cohort 2, N=196) were retrospectively analysed.

RESULTS

In cohort 1, patients were stratified into three groups with widely different disease-free survival rates (95%, 83% and 39%) on the basis of Histology(EMT) (P<0.0001). In cohort 2, Histology(EMT) significantly stratified overall survival of patients irrespective of metasectomy. Multivariate analyses indicated that Histology(EMT) had a strong prognostic impact independent of staging factors. Statistically, Histology(EMT) had a better prognostic stratification power than T and N stages; however, in cohort 2, the power of M substage was superior.

CONCLUSIONS

A histological model to categorise EMT by integrated assessment of dedifferentiation and desmoplastic environment is a potent prognostic index independent of staging factors.

Transforming growth factor-β1-induced epithelial-mesenchymal transition generates ALDH-positive cells with stem cell properties in cholangiocarcinoma

Epithelial-mesenchymal transition (EMT) is a major factor that facilitates the invasiveness and metastasis of cancer. Recent studies have demonstrated that EMT plays a key role in generating cancer stem cells (CSCs). This study aimed to investigate the effect of EMT on CSCs that were identified as positive for aldehyde dehydrogenase (ALDH) in cholangiocarcinoma (CCA). We demonstrated that transforming growth factor-β1 (TGF-β1)-induced EMT in the human cholangiocarcinoma (CCA) cell line, TFK-1, resulted in the acquisition of mesenchymal traits, as well as the expression of ALDH, which was accompanied by decreased sensitivity to the chemotherapeutic agent, 5-fluorouracil. ALDH-positive cells isolated from TFK-1 cells had higher proliferation potential in vitro and tumourigenic ability in vivo. They also expressed mesenchymal markers. Moreover, the expression levels of TGF-β1 and ALDH1 were correlated with poor prognosis in patients. We conclude that ALDH acts as a marker for CSCs in CCA, and TGF-β1-induced EMT is involved in the generation of CSCs. These findings offer a new tool for the study of CCA stem cells and illustrate a direct link between EMT and the gain of stem-cell properties.

Deletion of Ptp4a3 reduces clonogenicity and tumor-initiation ability of colitis-associated cancer cells in mice

The PTP4A3 gene is highly expressed in human colon cancer and often associates with enhanced metastatic potential. Genetic disruption of the mouse Ptp4a3 gene reduces the frequency of colon tumor formation in mice treated in a colitis-associated cancer model. In the current study, we have examined the role of Ptp4a3 in the tumor-initiating cell population of mouse colon tumors using an in vitro culture system. Tumors generated in vivo following AOM/DSS treatment were isolated, dissociated, and expanded on a feeder layer resulting in a CD133(+) cell population, which expressed high levels of Ptp4a3. Tumor cells deficient for Ptp4a3 exhibited reduced clonogenicity and growth potential relative to WT cells as determined by limiting dilution analysis. Importantly, expanded tumor cells from WT mice readily formed secondary tumors when transplanted into nude mice, while tumor cells without Ptp4a3 expression failed to form secondary tumors and thus were not tumorigenic. These results demonstrate that Ptp4a3 contributes to the malignant phenotype of tumor-initiating cells and supports its role as a potential therapeutic target to inhibit tumor self-renewal and metastasis.

Immunotherapy of cancer stem cells in solid tumors: initial findings and future prospective

INTRODUCTION

Conventional chemotherapies seemed to have reached a therapeutic plateau in the treatment of solid tumors and many metastatic diseases are still incurable. Events of chemo-resistance and relapses appear to be sustained by a subset of putative cancer stem cells (CSCs). New anticancer strategies need to face this new challenge exploring their efficacy against CSCs. Immunotherapy has raised enthusiasms in cancer therapy and its potential against CSCs is an intriguing field of research.

AREAS COVERED

In this work we reviewed the immunotherapy approaches directed against CSCs in solid tumors. We schematically divided adaptive immunotherapy strategies, mainly based on dendritic cell-vaccination, and strategies exploiting MHC-unrestricted effectors like natural killer cells, γδ T lymphocytes and cytokine-induced killer cells. Findings, strength and limitations of these models are discussed and compared highlighting their potential clinical relevance.

EXPERT OPINION

The important biologic role and clinical relevance of CSCs introduced a 'noble target' for immunotherapy and cancer treatments in general. Initial evidences suggest that CSCs may be susceptible to various types of immunotherapy attacks, overcoming their chemo-resistance. Investigation of important safety issues, based on shared features with 'normal' stem cells, along with intriguing synergisms with modulatory agents are open challenges for the next future and effective clinical translation.

Cancer Stem Cells: A Moving Target

Even though the number of anti-cancer drugs entering clinical trials and approved by the FDA has increased in recent years, many cancer patients still experience poor survival outcome. The main explanation for such a dismal prognosis is that current therapies might leave behind a population of cancer cells with the capacity for long-term self-renewal, so-called cancer stem cells (CSCs), from which most tumors are believed to be derived and fueled. CSCs might favor local and distant recurrence even many years after initial treatment, thus representing a potential target for therapies aimed at improving clinical outcome. In this review, we will address the CSC hypothesis with a particular emphasis on its current paradigms and debates, and discuss several mechanisms of CSC resistance to conventional therapies.