Colon cancer stem cells: implications for prevention and therapy

Differences and Similarities between Colorectal Cancer Cells and Colorectal Cancer Stem Cells: Molecular Insights and Implications

Malignant tumors are formed by diverse groups of cancer cells. Cancer stem cells (CSCs) are a subpopulation of heterogeneous cells identified in tumors that have the ability to self-renew and differentiate. Colorectal cancer (CRC), the third most frequent malignant tumor, is progressively being supported by evidence suggesting that CSCs are crucial in cancer development. We aim to identify molecular differences between CRC cells and CRC CSCs, as well as the effects of those differences on cell behavior in terms of migration, EMT, pluripotency, morphology, cell cycle/control, and epigenetic characteristics. The HT-29 cell line (human colorectal adenocarcinoma) and HT-29 CSCs (HT-29 CD133+/CD44+ cells) were cultured for 72 h. The levels of E-cadherin, KLF4, p53, p21, p16, cyclin D2, HDAC9, and P300 protein expression were determined using immunohistochemistry staining. The migration of cells was assessed by employing the scratch assay technique. Additionally, the scanning electron microscopy method was used to examine the morphological features of the cells, and their peripheral/central elemental ratios were compared with the help of EDS. Furthermore, a Muse cell cycle kit was utilized to determine the cell cycle analysis. The HT-29 CSC group exhibited high levels of expression for E-cadherin, p53, p21, p16, cyclin D2, HDAC9, and P300, whereas KLF4 was found to be high in the HT-29. The two groups did not exhibit any statistically significant differences in the percentages of cell cycle phases. The identification of specific CSC characteristics will allow for earlier cancer detection and the development of more effective precision oncology options.

Prognostic Impact of LGR5, Prox1, and Notch1 Biomarkers in Stage II to III Colon Cancer

The potentiation and activation of Wnt signaling pathways are now assumed to mediate the self-renewal and proliferation of colon cancer stem cells that are responsible for therapeutic resistance, tumor relapse, and metastasis. We aimed to evaluate LGR5, Prox1, and Notch1 immunohistochemical expression in stage II to III colon cancer. Their predictive role of tumor relapse, overall survival, and disease-free survival was statistically analyzed. Our results revealed that high LGR5 expression was identified in 56.7% of the patients, LGR5 expression was significantly associated with left-sided tumors (P<0.001). Moreover, its expression was significantly associated with the unfavorable tumor characteristics including high grade, deep invasion (pT), lymph node metastasis, and advanced tumor stage (P<0.001 for each). High Prox1 expression was observed in 65% of the cases, and its expression was significantly associated with tumor grade, lymph node metastasis, and the advanced tumor stage (P=0.004, 0.009, 0.016, respectively). Positive Notch1 expression was identified in 35% of patients, and it was inversely associated with high grade lymph node metastasis, deep invasion (pT), and advanced tumor stage (P<0.001 for each). During the follow-up period, the tumor relapse was significantly associated with high LGR5, high Prox1, and negative Notch1 expression. Shorter overall survival and disease-free survival were significantly associated with high LGR5, high Prox1, and negative Notch1 expression. High LGR5, high Prox1, and negative Notch1 expression are unfavorable prognostic factors in colon cancer. Prox1 is a crucial regulator of Notch-independent LGR5+ stem cells that is mostly responsible for relapse and therapeutic resistance in stage II to III colon cancer.

Microarray-based identification of differentially expressed genes associated with andrographolide derivatives-induced resistance in colon and prostate cancer cell lines

Chemoresistance poses a major hurdle to cancer treatments. Andrographolide-derived SRJ09 and SRJ23 were reported to exhibit potent, selective inhibitory activities against colon and prostate cancer cells, respectively. In this study, previously developed resistant colon (HCT-116^rst09) and prostate (PC-3^rst23) cancer cell lines were used to elucidate the molecular mechanisms contributing to chemoresistance. Cytotoxic effects of SRJ09 and SRJ23 on both parental and resistant cells were investigated. Cell cycle distributions in HCT-116^rst09 cells following SRJ09 treatment were analysed using flow cytometry. Whole-genome microarray analysis was performed on both parental and resistant cells to obtain differential gene expression profiles. Microarray data were subjected to protein-protein interaction network, functional enrichment, and pathway analyses. Reverse transcription-polymerase chain reaction (RT-PCR) was used to validate the changes in expression levels of selected genes. Besides morphological changes, HCT-116^rst09 cells showed 7.0-fold resistance to SRJ09 while PC-3^rst23 cells displayed a 5.5-fold resistance to SRJ23, as compared with their respective parental cells. G₀/G₁-phase cell cycle arrest was observed in HCT-116^rst09 cells upon SRJ09 treatment. Collectively, 77 and 21 genes were found differentially modulated in HCT-116^rst09 and PC-3^rst23 cells, respectively. Subsequent bioinformatics analysis revealed several genes associated with FGFR4 and PI3K pathways, and cancer stemness, were chemoresistance mediators in HCT-116^rst09 cells. RT-PCR confirmed the HMOX1 upregulation and ATG12 downregulation protected the PC-3^rst23 cells from SRJ23 cytotoxicity. In conclusion, acquired chemoresistance to SRJ09 and SRJ23 in colon and prostate cancer cells, respectively, could be attributed to the alterations in the expression of genes such as those related to PI3K and autophagy pathways.

High expression of CD133 - stem cell marker for prediction of clinically agressive type of colorectal cancer

&lt;b&gt; Background:&lt;/b&gt; Colorectal cancer (CRC) is one of the most common malignancies in the world. The cancer stem cell (CSC) markers are associated with aggressive cancer types and poor prognosis. The objective of the study was to evaluate the CD133 expression and to correlate it with clinicopathological features in patients with CRC. &lt;br&gt;&lt;b&gt;Material and Methods:&lt;/b&gt; Our study included ninety patients with CRC who underwent curative surgical resection from 2012 to 2017 at the University Clinic for Digestive Surgery, Skopje, North Macedonia. Tumor samples were first analyzed with standard histopathological methods and then the CD133 expression was investigated immunohistochemically. The level of expression of CD133 was classified semiquantitatively. Low positivity was defined as positive immunoreactivity in &lt;50% of tumor glands, and high positivity was defined as positive immunoreactivity in ≥50% of tumor glands. Furthermore, clinicopathological features of patients were retrospectively reviewed. &lt;br&gt;&lt;b&gt;Results:&lt;/b&gt; High expression of CD133 was found in 47.8% of patients' CRC samples. In 69.6% of patients with metastatic lesions in visceral organs we found high expression of CD133. We found statistically significant differences in the expression of CD133 between patients with and without visceral metastatic lesions (P = 0.0153), between patients with a different T category (P = 0.0119), N status (P = 0.0066) and grade (G) (P = 0.0115). Our results showed that the stage of disease has the greatest impact on expression of CD133 (P &lt; 0.00001). &lt;br&gt;&lt;b&gt;Conclusion:&lt;/b&gt; High expression of CD133 is a useful marker for prediction of the clinically aggressive type of CRC and can be routinely implemented in standard pathohistological diagnostics.

Biological roles of piRNAs in colorectal cancer

Colorectal cancer (CRC) is one of the most common malignancies worldwide and a major cause of cancer-related deaths. Numerous studies have suggested that piwi-interacting RNAs (piRNAs), a new type of non-coding RNA (ncRNA), are closely related to the occurrence and development of cancer. piRNAs have been shown to regulate the occurrence of CRC by modulating multiple molecular signaling pathways. Here, the roles of piRNAs in CRC were reviewed to provide evidence for their potential as molecular targets for CRC.

Triptolide inhibits CD133+ /CD44+ colon cancer stem cell growth and migration through triggering apoptosis and represses epithelial-mesenchymal transition via downregulating expressions of snail, slug, and twist

High recurrence and metastatic behavior patterns are the most important reasons for the failure of treatment strategies in patients with colon cancer. Cancer stem cells (CSCs), which are considered root of cancer, are thought to be associated with therapy resistance, relapse, and metastasis, and, therefore, targeting CSCs rather than the bulk population may be an effective approach. In cancer studies, there is an increasing interest in close friendship between epithelial-mesenchymal transition (EMT) and CSCs. Triptolide (TPL) isolated from Chinese herb Tripterygium wilfordii has important effects on the prevention of migration and metastasis as well as cytotoxic effect against cancer cells. The potential lethal efficacy of TPL on CSCs that is highly resistant to the drug is an unsolved mystery. Fundamentally, the present study basically aims to find answers to two questions: (a) is it possible to target colon CSCs with TPL? and (b) what are the mechanisms underlying TPL's potential to eliminate CSCs? Cytotoxic effects of TPL on CSCs were evaluated by WST-1 and Muse count and viability assays. Apoptosis assay and cell-cycle analysis were performed to investigate the inhibitory effect of TPL. Moreover, the effects of TPL on spheroid formation capacity, migration, and EMT processes, which are associated with CSC phenotype, were also investigated. The results revealed that TPL triggered cell death and apoptosis and altered cell cycle distribution. Moreover, TPL significantly reduced the snail slug and twist expressions associated with EMT. TPL has been shown to be effective in colon CSCs by in vitro experiments, and it might be a highly effective agent against colon cancer has been implicated in need of supporting in vivo and clinical studies.

DNA methylation of shelf, shore and open sea CpG positions distinguish high microsatellite instability from low or stable microsatellite status colon cancer stem cells

Aim: To investigate the genome-wide methylation of genetically characterized colorectal cancer stem cell (CR-CSC) lines. Materials & methods: Eight CR-CSC lines were isolated from primary colorectal cancer (CRC) tissues, cultured and characterized for aneuploidy, mutational status of CRC-related genes and microsatellite instability (MSI). Genome-wide DNA methylation was assessed by MethylationEPIC microarray. Results: We describe a distinctive methylation pattern that is maintained following in vivo passages in immune-compromised mice. We identified an epigenetic CR-CSC signature associated with MSI. We noticed that the preponderance of the differentially methylated positions do not reside at CpG islands, but spread to shelf and open sea regions. Conclusion: Given that CRCs with MSI-high status have a lower metastatic potential, the identification of a MSI-related methylation signature could provide new insights and possible targets into metastatic CRC.

Integrin α10, a Novel Therapeutic Target in Glioblastoma, Regulates Cell Migration, Proliferation, and Survival

New, effective treatment strategies for glioblastomas (GBMs), the most malignant and invasive brain tumors in adults, are highly needed. In this study, we investigated the potential of integrin α10β1 as a therapeutic target in GBMs. Expression levels and the role of integrin α10β1 were studied in patient-derived GBM tissues and cell lines. The effect of an antibody–drug conjugate (ADC), an integrin α10 antibody conjugated to saporin, on GBM cells and in a xenograft mouse model was studied. We found that integrin α10β1 was strongly expressed in both GBM tissues and cells, whereas morphologically unaffected brain tissues showed only minor expression. Partial or no overlap was seen with integrins α3, α6, and α7, known to be expressed in GBM. Further analysis of a subpopulation of GBM cells selected for high integrin α10 expression demonstrated increased proliferation and sphere formation. Additionally, siRNA-mediated knockdown of integrin α10 in GBM cells led to decreased migration and increased cell death. Furthermore, the ADC reduced viability and sphere formation of GBM cells and induced cell death both in vitro and in vivo. Our results demonstrate that integrin α10β1 has a functional role in GBM cells and is a novel, potential therapeutic target for the treatment of GBM.

Prognostic implication of ABC transporters and cancer stem cell markers in patients with stage III colon cancer receiving adjuvant FOLFOX-4 chemotherapy

Cancer stem cell (CSC) and ATP-binding cassette (ABC) transporters are associated with treatment resistance and outcomes of patients with cancer. The present study investigated the prognostic implications of pre-therapeutic expression of ABC transporters and CSC markers in patients with colon cancer (CC) who received adjuvant 5-fluorouracil, leucovorin and oxaliplatin combination therapy (FOLFOX-4). The immunohistochemical expression of 3 ABC transporters, including ABC subfamily C member 2 (ABCC2), ABCC3 and ABC subfamily G member 2 (ABCG2), and 3 CSC markers, including sex determining region Y-box 2 (SOX2), leucine-rich repeat-containing G protein-coupled receptor 5 and aldehyde dehydrogenase 1, were determined in 164 CC tissues from patients with stage III CC, who underwent postoperative FOLFOX-4 chemotherapy. The association between the protein expression and patients' prognoses was statistically analyzed. ABCG2 was associated with favorable overall survival rate (OS; P=0.001), and ABCC2, ABCG2 and SOX2 were associated with increased disease-free survival rate (DFS; P=0.001, 0.002 and 0.013, respectively). In multivariate analyses, ABCG2 was an independent prognostic factor for OS [hazard ratio (HR)=2.877; P=0.046], and ABCC2 and SOX2 were independent prognostic factors for DFS (HR=2.831; P=0.014; HR=2.558, P=0.020, respectively). ABCC2, ABCG2 and SOX2 may be promising prognostic markers for patients with CC receiving FOLFOX-4 therapy.

c-Myc maintains the self-renewal and chemoresistance properties of colon cancer stem cells

Cancer stem cells (CSCs) are responsible for cancer formation, recurrence and drug resistance. c-Myc, one of the core markers for stem cells, has recently been considered to serve as a link between malignancy and ‘stemness’. However, the precise function of c-Myc in colon CSCs is still unclear. In the present study, a subpopulation of colon CSCs expressing a CD133 surface phenotype was isolated from the human HT-29 cell line, which possess greater tumor sphere-forming efficiency and have higher expression of ‘stemness’-associated genes compared with CD133-negative cells. Furthermore, it was demonstrated that c-Myc was highly expressed in CD133⁺ colon CSCs. Knockdown of c-Myc expression with small interfering RNA in colon CSCs can significantly inhibit tumor sphere formation, reduce the invasive and migratory capacity of CD133⁺ cells in vitro, and suppress the tumorigenicity of colon CSCs in vivo. In addition, it was suggested that c-Myc silencing may sensitize colon CSCs to chemotherapy-induced cytotoxicity via the downregulation of ABCG2 and ABCB5. These findings support a central role for c-Myc in maintaining the self-renewing and chemoresistant properties of colon CSCs.

R-spondin1/Wnt-enhanced Ascl2 autoregulation controls the self-renewal of colorectal cancer progenitor cells

The Wnt signaling pathway controls stem cell identity in the intestinal epithelium and cancer stem cells (CSCs). The transcription factor Ascl2 (Wnt target gene) is fate decider of intestinal cryptic stem cells and colon cancer stem cells. It is unclear how Wnt signaling is translated into Ascl2 expression and keeping the self-renewal of CRC progenitor cells. We showed that the exogenous Ascl2 in colorectal cancer (CRC) cells activated the endogenous Ascl2 expression via a direct autoactivatory loop, including Ascl2 binding to its own promoter and further transcriptional activation. Higher Ascl2 expression in human CRC cancerous tissues led to greater enrichment in Ascl2 immunoprecipitated DNA within the Ascl2 promoter in the CRC cancerous sample than the peri-cancerous mucosa. Ascl2 binding to its own promoter and inducing further transcriptional activation of the Ascl2 gene was predominant in the CD133⁺CD44⁺ CRC population. R-spondin1/Wnt activated Ascl2 expression dose-dependently in the CD133⁺CD44⁺ CRC population, but not in the CD133^-CD44^- CRC population, which was caused by differences in Ascl2 autoregulation under R-spondin1/Wnt activation. R-spondin1/Wnt treatment in the CD133⁺CD44⁺ or CRC CD133^-CD44^- populations exerted a different pattern of stemness maintenance, which was defined by alterations of the mRNA levels of stemness-associated genes, the protein expression levels (Bmi1, C-myc, Oct-4 and Nanog) and tumorsphere formation. The results indicated that Ascl2 autoregulation formed a transcriptional switch that was enhanced by Wnt signaling in the CD133⁺CD44⁺ CRC population, thus conferring their self-renewal.

Colonic Stem Cells Expression of Lgr5 and CD133 Proteins as Predictive Markers in Colorectal Cancer among Egyptian Patients

AIM:

Colorectal cancer is the fourth common tumour in Egypt after lymphoid, breast and urinary tumours. The study aims to assess the expression of Lgr5 and CD133 in pre-malignant (adenomatous polyps and IBD), malignant colorectal lesions and normal colonic mucosa by immunohistochemical staining.

MATERIAL AND METHODS:

This prospective study was done on 100 patients presenting with colonic symptoms, patients were divided into four groups; group I including 20 patients in the control group, group II including 20 ulcerative colitis (U.C) patients, group III including 20 patients with adenomatous polyps and group IV including 40 patients with colorectal cancer (CRC).

RESULTS:

Lgr5 and CD133 expression was significantly higher in carcinoma than in adenomas, IBD and normal mucosa (P < 0.001). Lrg5 and CD133 was positively correlated with histological grade (P = 0.001), depth of invasion (P = 0.001), lymph node metastasis (P < 0.001), distant metastasis (P < 0.004) and TNM stage (P < 0.001).

CONCLUSION:

Role of Lgr5 and CD133 as stem cell marker was expressed and presented with different expression in the normal colonic mucosa, adenoma and CRC and showed increased expression in an advanced stage of CRC. This may suggest its possible involvement in colorectal tumorigenesis and invasion.

Rab27A mediated by NF-κB promotes the stemness of colon cancer cells via up-regulation of cytokine secretion

Recent evidences have unveiled critical roles of cancer stem cells (CSCs) in tumorigenicity, but how interactions between CSC and tumor environments help maintain CSC initiation remains obscure. The small GTPases Rab27A regulates autocrine and paracrine cytokines by monitoring exocytosis of extracellular vesicles, and is reported to promote certain tumor progression. We observe that overexpression of Rab27A increased sphere formation efficiency (SFE) by increasing the proportion of CD44⁺ and PKH26^high cells in HT29 cell lines, and accelerating the growth of colosphere with higher percentage of cells at S phase. Mechanism study revealed that the supernatant derived from HT29 sphere after Rab27A overexpression was able to expand sphere numbers with elevated secretion of VEGF and TGF-β. In tumor implanting nude mice model, tumor initiation rates and tumor sizes were enhanced by Rab27A with obvious angiogenesis. As a contrast, knocking down Rab27A impaired the above effects. More importantly, the correlation between higher p65 level and Rab27A in colon sphere was detected, p65 was sufficient to induce up-regulation of Rab27A and a functional NF-κB binding site in the Rab27A promoter was demonstrated. Altogether, our findings reveal a unique mechanism that tumor environment related NF-κB signaling promotes various colon cancer stem cells (cCSCs) properties via an amplified paracrine mechanism regulated by higher Rab27A level.

Hedgehog Signals Mediate Anti-Cancer Drug Resistance in Three-Dimensional Primary Colorectal Cancer Organoid Culture

Colorectal cancer is one of the most common causes of cancer death worldwide. In patients with metastatic colorectal cancer, combination treatment with several anti-cancer drugs is employed and improves overall survival in some patients. Nevertheless, most patients with metastatic disease are not cured owing to the drug resistance. Cancer stem cells are known to regulate resistance to chemotherapy. In the previous study, we established a novel three-dimensional organoid culture model from tumor colorectal tissues of human patients using an air-liquid interface (ALI) method, which contained numerous cancer stem cells and showed resistance to 5-fluorouracil (5-FU) and Irinotecan. Here, we investigate which inhibitor for stem cell-related signal improves the sensitivity for anti-cancer drug treatment in tumor ALI organoids. Treatment with Hedgehog signal inhibitors (AY9944, GANT61) decreases the cell viability of organoids compared with Notch (YO-01027, DAPT) and Wnt (WAV939, Wnt-C59) signal inhibitors. Combination treatment of AY9944 or GANT61 with 5-FU, Irinotecan or Oxaliplatin decreases the cell viability of tumor organoids compared with each anti-cancer drug alone treatment. Treatment with AY9944 or GANT61 inhibits expression of stem cell markers c-Myc, CD44 and Nanog, likely through the decrease of their transcription factor, GLI-1 expression. Combination treatment of AY9944 or GANT61 with 5-FU or Irinotecan also prevents colony formation of colorectal cancer cell lines HCT116 and SW480. These findings suggest that Hedgehog signals mediate anti-cancer drug resistance in colorectal tumor patient-derived ALI organoids and that the inhibitors are useful as a combinational therapeutic strategy against colorectal cancer.

Ascl2 activation by YAP1/KLF5 ensures the self-renewability of colon cancer progenitor cells

Achaete scute-like 2 (Ascl2) is the Wnt signaling target, its regulation by other signaling is undefined. Now we demonstrated that CD133⁺/CD44⁺ cell population from HT-29 or Caco-2 cells exhibited cancer stem cell (CSC) properties with highly expressed Ascl2, which is related to the Hippo signaling pathway. YAP1 interference in CD133⁺/CD44⁺ HT-29 or Caco-2 cells reduced their proliferation, colony-forming ability and tumorsphere formation in vitro and inhibited the ‘stemness’-associated genes and Ascl2 expression. Enforcing YAP1 expression in HT-29 or Caco-2 cells triggered the opposite changes. Ascl2 interference reversed the phenotype of YAP1-enforced expressed HT-29 or Caco-2 cells. Krüppel-like factor 5 (KLF5) protein, not KLF5 mRNA levels, were increased due to YAP1 overexpression which is reported to prevent KLF5 degradation. Co-immunoprecipitation (Co-IP) assays demonstrated that YAP1 bound with KLF5 in HT-29 and Caco-2 cells. Luciferase and chromatin immunoprecipitation (ChIP) assays indicated that both YAP1 and KLF5 bound to the first two loci with GC-boxes in Ascl2 promoter and induced Ascl2 transcription. The decreased Ascl2 transcription by YAP1 interference required an intact KLF5 binding site (GC-box) within Ascl2 promoter, KLF5 knockdown reduced YAP1 binding and Ascl2 luciferase reporter activity upon YAP1 overexpression. Positive correlation among YAP1 and Ascl2 mRNA levels was observed in colorectal cancer (CRC) samples. Thus, our study demonstrated that Ascl2, a fate decider of CRC progenitor cells can be activated by the Hippo signaling pathway in CRC progenitor cells, and ensured their self-renewability.

Therapeutic strategies against cancer stem cells in human colorectal cancer

Colorectal cancer (CRC) is the third most frequent malignancy and represents the fourth most common cause of cancer-associated mortalities in the world. Despite many advances in the treatment of CRC, the 5-year survival rate of patients with CRC remains unsatisfactory due to tumor recurrence and metastases. Recently, cancer stem cells (CSCs), have been suggested to be responsible for the initiation and relapse of the disease, and have been identified in CRC. Due to their basic biological features, which include self-renewal and pluripotency, CSCs may be novel therapeutic targets for CRC and other cancer types. Conventional therapeutics only act on proliferating and mature cancer cells, while quiescent CSCs survive and often become resistant to chemotherapy. In this review, markers of CRC-CSCs are evaluated and the recently introduced experimental therapies that specifically target these cells by inducing CSC proliferation, differentiation and sensitization to apoptotic signals via molecules including Dickkopf-1, bone morphogenetic protein 4, Kindlin-1, tankyrases, and p21-activated kinase 1, are discussed. In addition, novel strategies aimed at inhibiting some crucial processes engaged in cancer progression regulated by the Wnt, transforming growth factor β and Notch signaling pathways (pyrvinium pamoate, silibinin, PRI-724, P17, and P144 peptides) are also evaluated. Although the metabolic alterations in cancer were first described decades ago, it is only recently that the concept of targeting key regulatory molecules of cell metabolism, such as sirtuin 1 (miR-34a) and AMPK (metformin), has emerged. In conclusion, the discovery of CSCs has resulted in the definition of novel therapeutic targets and the development of novel experimental therapies for CRC. However, further investigations are required in order to apply these novel drugs in human CRC.

Aptamer-mediated survivin RNAi enables 5-fluorouracil to eliminate colorectal cancer stem cells

The development of chemoresistance and inability in elimination of cancer stem cells are among the key limitations of cancer chemotherapy. Novel molecular therapeutic strategies able to overcome such limitations are urgently needed for future effective management of cancer. In this report, we show that EpCAM-aptamer-guided survivin RNAi effectively downregulated survivin both in colorectal cancer cells in vitro and in a mouse xenograft model for colorectal cancer. When combined with the conventional chemotherapeutic agents, the aptamer-guided survivin RNAi was able to enhance the sensitivity towards 5-FU or oxaliplatin in colorectal cancer stem cells, increase apoptosis, inhibit tumour growth and improve the overall survival of mice bearing xenograft colorectal cancer. Our results indicate that survivin is one of the key players responsible for the innate chemoresistance of colorectal cancer stem cells. Thus, aptamer-mediated targeting of survivin in cancer stem cells in combination with chemotherapeutic drugs constitutes a new avenue to improve treatment outcome in oncologic clinics.

Assessment of neutralizing interleukin-4 effect on CD133 gene expression in colon cancer cell line

Colorectal cancer may be maintained by cancer stem-like cells (CSCs) that express the cell surface marker CD133. CSCs (CD133+cells) exhibits greater resistance to the chemotherapy and this resistance may be mediated in part by an autocrine response to IL4. The aim of the study was to assess the effect of anti-IL4 antibody alone or in combination with chemotherapy on the CD133 expression andthe tumor growth. We used Caco cell line in our experiments and the samples were as the following; untreated colorectal cell line, cells treated by chemotherapy, cells treated by anti-IL4 antibody in 3doses (2.5, 5, 10μg/ml), cells treatedby combination of chemotherapy and anti-IL4 antibody in 3 doses. Results of our in vitro studies demonstrated that anti-IL4 inhibited growth of Caco cell line in a dose-dependent manner revealing a 32.11% inhibition at the highest concentration (10µg/ml). There was further significant inhibition by combination of anti IL4 and chemotherapy in a dose response manner when compared to group treated by chemotherapy only. These effects were associated with decreased expression of CD133 in tumor cells also. Lastly, anti-IL4 antibody stimulated apoptosis. Our study suggested that neutralizing of IL4 by anti IL4 antibody affect the CD133+ cells may be by increasing their apoptosis. The effects of anti IL4 antibody either, alone or in combination with chemotherapy, inhibited the tumor growth and decreased the viable tumor cells. Furthermore, neutralizing of IL4 increased the efficacy of chemotherapy treatment.

Identification of microRNA profile specific to cancer stem-like cells directly isolated from human larynx cancer specimens

Background

Emerging evidences proposed that microRNAs are associated with regulation of distinct physio-pathological processes including development of normal stem cells and carcinogenesis. In this study we aimed to investigate microRNA profile of cancer stem-like cells (CSLCs) isolated form freshly resected larynx cancer (LCa) tissue samples.

Methods

CD133 positive (CD133⁺) stem-like cells were isolated from freshly resected LCa tumor specimens. MicroRNA profile of 12 pair of CD133⁺ and CD133⁻ cells was determined using microRNA microarray and differential expressions of selvected microRNAs were validated by quantitative real time PCR (qRT-PCR).

Results

MicroRNA profiling of CD133⁺ and CD133⁻ LCa samples with microarray revealed that miR-26b, miR-203, miR-200c, and miR-363-3p were significantly downregulated and miR-1825 was upregulated in CD133⁺ larynx CSLCs. qRT-PCR analysis in a total of 25 CD133⁺/CD133⁻ sample pairs confirmed the altered expressions of these five microRNAs. Expressions of miR-26b, miR-200c, and miR-203 were significantly correlated with miR-363-3p, miR-203, and miR-363-3p expressions, respectively. Furthermore, in silico analysis revealed that these microRNAs target both cancer and stem-cell associated signaling pathways.

Conclusions

Our results showed that certain microRNAs in CD133⁺ cells could be used as cancer stem cell markers. Based on these results, we propose that this panel of microRNAs might carry crucial roles in LCa pathogenesis through regulating stem cell properties of tumor cells.

Electronic supplementary material

The online version of this article (doi:10.1186/s12885-016-2863-3) contains supplementary material, which is available to authorized users.

Dual Targeting of 3-Hydroxy-3-methylglutaryl Coenzyme A Reductase and Histone Deacetylase as a Therapy for Colorectal Cancer

Statins are 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase (HMGR) inhibitors decreasing serum cholesterol and have shown promise in cancer prevention. In this study, we demonstrated the oncogenic role of HMGR in colorectal cancer (CRC) by disclosing increased HMGR activity in CRC patients and its enhancement of anti-apoptosis and stemness. Our previous studies showed that statins containing carboxylic acid chains possessed activity against histone deacetylases (HDACs), and strengthened their anti-HDAC activity through designing HMGR-HDAC dual inhibitors, JMF compounds. These compounds exerted anti-cancer effect in CRC cells as well as in AOM-DSS and Apc^Min/+ CRC mouse models. JMF mostly regulated the genes related to apoptosis and inflammation through genome-wide ChIP-on-chip analysis, and Ingenuity Pathways Analysis (IPA) predicted their respective regulation by NR3C1 and NF-κB. Furthermore, JMF inhibited metastasis, angiogenesis and cancer stemness, and potentiated the effect of oxaliplatin in CRC mouse models. Dual HMGR-HDAC inhibitor could be a potential treatment for CRC.

•

HMGR is an oncotarget of CRC.

•

JMF3086 targeting HMGR and HDACs is effective therapy in different preclinical CRC models.

•

JMF3086 down-regulated inflammatory, proliferation, stemness and anti-apoptotic genes but up-regulated tumor suppressor genes.

Addition of chemotherapeutic and molecular targeted agents stepwise prolongs the survival of metastatic colorectal cancer (CRC), implying the importance of new drugs discovery. Furthermore, combination therapy is a rational approach to improve the anti-cancer efficacy. Here, we demonstrate HMGR is a target for CRC and design a dual HMGR and HDAC inhibitor JMF3086. It inhibits tumor progression, metastasis and stemness in several preclinical models, conferring a significant benefit above lovastatin plus SAHA. JMF3086 also potentiates the effect of oxaliplatin, an important chemotherapeutic agent of CRC. These results provide a rationale for clinical studies of JMF3086 to advance the survival of metastatic CRC.

Treatment of colon cancer with oncolytic herpes simplex virus in preclinical models

Cancer stem cells (CSCs), which are a rare population in any type of cancer, including colon cancer, are tumorigenic and responsible for cancer recurrence and metastasis. CSCs have been isolated from a number of different solid tumors recently, although the isolation of CSCs in colon cancer is still challenging. We cultured colon cancer cells in stem cell medium to obtain colonosphere cells. These cells possessed the characteristics of CSCs, with a high capacity of tumorigenicity, migration and invasion in vitro and in vivo. The isolation and identification of CSCs have provided new targets for the therapeutics. Oncolytic herpes simplex viruses (oHSV) are an effective strategy for killing colon cancer cells in preclinical models. Here, we examined the efficacy of an oncolytic herpes simplex virus type 2 (oHSV2) in killing colon cancer cells and colon cancer stem-like cells (CSLCs). oHSV2 was found to be highly cytotoxic to the adherent and sphere cells in vitro, and oHSV2 treatment in vivo significantly inhibited tumor growth. This study demonstrates that oHSV2 is effective against colon cancer cells and colon CSLCs and could be a promising strategy for treating colon cancer patients.

Functional modification of adipocytes by grape seed extract impairs their pro-tumorigenic signaling on colon cancer stem cells and the daughter cancer cells

With global rise in obesity, it is imperative that we identify obesity-driven factors that increase growth and progression of colorectal cancer (CRC), and also discover and develop agents with anti-CRC efficacy under obese conditions. Here in, we investigated grape seed extract (GSE), a well-defined agent with both preventive and anti-CRC efficacy, for its potential to impair pro-tumorigenic signaling of adipocytes on CRC/colon cancer stem cells (CSCs) and associated molecular mechanisms, to control CRC under obese conditions. GSE treatment significantly decreased the growth and invasion promoting effects of both mouse and human adipocytes on CRC cells. Moreover, GSE exerted a direct inhibitory effect, as well as it strongly reduced the growth promoting signals of adipocytes, on colon CSCs. These GSE effects were associated with a decrease in both mRNA and protein levels of various CSC-associated molecules. Notably, GSE effects on adipocytes were not due to changes in lipid content, but by inducing the ‘browning’ of adipocytes as evidenced by an increase in UCP-1 mRNA level and mitochondriogenesis. Together, these findings, for the first time, suggest the ability of GSE to induce ‘brown remodeling’ of white adipocytes, which causes functional modification of adipocytes thus impairing their pro-tumorigenic signals on colon CSCs/CRC cells.

Drug-eluting microarrays to identify effective chemotherapeutic combinations targeting patient-derived cancer stem cells

A new paradigm in oncology establishes a spectrum of tumorigenic potential across the heterogeneous phenotypes within a tumor. The cancer stem cell hypothesis postulates that a minute fraction of cells within a tumor, termed cancer stem cells (CSCs), have a tumor-initiating capacity that propels tumor growth. An application of this discovery is to target this critical cell population using chemotherapy; however, the process of isolating these cells is arduous, and the rarity of CSCs makes it difficult to test potential drug candidates in a robust fashion, particularly for individual patients. To address the challenge of screening drug libraries on patient-derived populations of rare cells, such as CSCs, we have developed a drug-eluting microarray, a miniaturized platform onto which a minimal quantity of cells can adhere and be exposed to unique treatment conditions. Hundreds of drug-loaded polymer islands acting as drug depots colocalized with adherent cells are surrounded by a nonfouling background, creating isolated culture environments on a solid substrate. Significant results can be obtained by testing <6% of the cells required for a typical 96-well plate. Reliability was demonstrated by an average coefficient of variation of 14% between all of the microarrays and 13% between identical conditions within a single microarray. Using the drug-eluting array, colorectal CSCs isolated from two patients exhibited unique responses to drug combinations when cultured on the drug-eluting microarray, highlighting the potential as a prognostic tool to identify personalized chemotherapeutic regimens targeting CSCs.

Silibinin strongly inhibits the growth kinetics of colon cancer stem cell-enriched spheroids by modulating interleukin 4/6-mediated survival signals

Involvement of cancer stem cells (CSC) in initiation, progression, relapse, and therapy-resistance of colorectal cancer (CRC) warrants search for small molecules as ‘adjunct-therapy’ to target both colon CSC and bulk tumor population. Herein, we assessed the potential of silibinin to eradicate colon CSC together with associated molecular mechanisms. In studies examining how silibinin modulates dynamics of CSC spheroids in terms of its effect on kinetics of CSC spheroids generated in presence of mitogenic and interleukin (IL)-mediated signaling which provides an autocrine/paracrine amplification loop in CRC, silibinin strongly decreased colon CSC pool together with cell survival of bulk tumor cells. Silibinin effect on colon CSC was mediated via blocking of pro-tumorigenic signaling, notably IL-4/-6 signaling that affects CSC population. These silibinin effects were associated with decreased mRNA and protein levels of various CSC-associated transcription factors, signaling molecules and markers. Furthermore, 2D and 3D differentiation assays indicated formation of more differentiated clones by silibinin. These results highlight silibinin potential to interfere with kinetics of CSC pool by shifting CSC cell division to asymmetric type via targeting various signals associated with the survival and multiplication of colon CSC pool. Together, our findings further support clinical usefulness of silibinin in CRC intervention and therapy.

Cancer stem cells: a new approach to tumor development

Many theories have been proposed to explain the origins of cancer. Currently, evidences show that not every tumor cell is capable of initiating a tumor. Only a small part of the cancer cells, called cancer stem cells (CSCs), can generate a tumor identical to the original one, when removed from human tumors and transplanted into immunosuppressed mice. The name given to these cells comes from the resemblance to normal stem cells, except for the fact that their ability to divide is infinite. These cells are also affected by their microenvironment. Many of the signaling pathways, such as Wnt, Notch and Hedgehog, are altered in this tumoral subpopulation, which also contributes to abnormal proliferation. Researchers have found several markers for CSCs; however, much remains to be studied, or perhaps a universal marker does not even exist, since they vary among tumor types and even from patient to patient. It was also found that cancer stem cells are resistant to radiotherapy and chemotherapy. This may explain the re-emergence of the disease, since they are not completely eliminated and minimal amounts of CSCs can repopulate a tumor. Once the diagnosis in the early stages greatly increases the chances of curing cancer, identifying CSCs in tumors is a goal for the development of more effective treatments. The objective of this article is to discuss the origin of cancer according to the theory of stem cell cancer, as well as its markers and therapies used for treatment.

Biomolecules-conjugated nanomaterials for targeted cancer therapy

Biomolecules perform vital functions in biology. These functional biomolecules with diverse modifications hold great promise for further applications in bioanalysis and cancer therapy. However, these functional biomolecules face challenges, especially in the field of drug delivery for cancer therapy. For example, functional biomolecules are typically unstable when taken up by cells, as they are easily digested by enzymes. To address this obstacle, nanomaterials have been employed as drug carriers or vehicles, which are powerful nanoplatforms for imaging and cancer treatment. Multifunctionality of these nanoplatforms offers great advantages over conventional reagents, including targeting to a diseased site to minimize systemic toxicity, and the ability to solubilize hydrophobic or labile drugs to improved pharmacokinetics. In this review, we summarize typical functional biomolecule-conjugated nanomaterials for targeting drug delivery. Under the appropriate conditions, targeted drug delivery can be achieved from a high density of biomolecules that are bound to the surface of nanomaterials, resulting in a high affinity for the targets. The high density of biomolecules then leads to a high local concentration, being able to prevent degradation by enzymes. Furthermore, biomolecule-nanomaterial conjugates have been identified to enter cells more easily than free biomolecules, and controllable drug release can then be obtained by a response to a stimulus, such as redox, pH, light, thermal, enzyme-trigged strategies. Now and in the future, with the development of artificial biomolecules as well as nanomaterials, targeted drug delivery based on elegant biomolecule-nanomaterial conjugation approaches is expected to achieve great versatility, additional functions, and further advances.

Cancer stem cells: a systems biology view of their role in prognosis and therapy

Evidence has accumulated that characterizes highly tumorigenic cancer cells residing in heterogeneous populations. The accepted term for such a subpopulation is cancer stem cells (CSCs). While many questions still remain about their precise role in the origin, progression, and drug resistance of tumors, it is clear they exist. In this review, a current understanding of the nature of CSC, their potential usefulness in prognosis, and the need to target them will be discussed. In particular, separate studies now suggest that the CSC is plastic in its phenotype, toggling between tumorigenic and nontumorigenic states depending on both intrinsic and extrinsic conditions. Because of this, a static view of gene and protein levels defined by correlations may not be sufficient to either predict disease progression or aid in the discovery and development of drugs to molecular targets leading to cures. Quantitative dynamic modeling, a bottom up systems biology approach whereby signal transduction pathways are described by differential equations, may offer a novel means to overcome the challenges of oncology today. In conclusion, the complexity of CSCs can be captured in mathematical models that may be useful for selecting molecular targets, defining drug action, and predicting sensitivity or resistance pathways for improved patient outcomes.

Stem cells, colorectal cancer and cancer stem cell markers correlations

: The idea of stem cells as being progenitors of cancer was initially controversial, but later supported by research in the field of leukemia and solid tumors. Afterwards, it was established that genetic abnormalities can affect the stem and progenitor cells, leading to uncontrolled replication and deregulated differentiation. These alterations will cause the changeover to cancerous stem cells (CSC) having two main characteristics: tumor initiation and maintenance. This review will focus on the colorectal cancer stem cell (CR-CSCs) theory which provides a better understanding of different tumor processes: initiation, aggressive growth, recurrence, treatment resistance and metastasis. A search in PubMed/Medline was performed using the following keywords: colorectal cancer stem cells (CR-CSCs), colorectal neoplasms stem cells, colorectal cancer stem cell (CR-CSCs) markers, etc. Electronic searches were supplemented by hand searching reference lists, abstracts and proceedings from meetings. Isolation of CR-CSCs can be achieved by targeting and selecting subpopulation of tumor cells based on expression of one or multiple cell surface markers associated with cancer self-renewal, markers as: CD133, CD166, CD44, CD24, beta1 integrin-CD29, Lgr5, EpCAM (ESA), ALDH-1, Msi-1, DCAMLK1 or EphB receptors. The identification and localization of CR-CSCs through different markers will hopefully lead to a better stratification of prognosis and treatment response, as well as the development of new effective strategies for cancer management.

The impact of Aldehyde dehydrogenase 1 expression on prognosis for metastatic colon cancer

BACKGROUND

Cancer stem cells may be associated with tumor progression and prognosis for colon cancer. We hypothesized that expression of Aldehyde dehydrogenase 1 (ALDH1) would increase with tumor progression and be associated with survival.

METHODS

Tissue was obtained from resection specimens for isolation of cancer stem cells. In addition, paraffin blocks from resected colon cancers with normal colon, primary tumor, and lymph node and liver metastasis from 2000 to 2010 were identified and stained with ALDH1.

RESULTS

In in vitro models (adherent and tumor spheres) ALHD1+ cells grew more efficiently than ALDH1- cells. ALDH1 expression was highest in peritumoral crypt cells (0.137 μm(2), 95% confidence interval [CI] 0.125-0.356) and normal crypts (median 0.091 μm(2), 95% CI 0.064-0.299) followed by lymph node metastasis (median 0.025 μm(2), 95% CI 0-0.131) and the primary cancers (median 0.014 μm(2), 95% CI 0.0123-0.154). Samples were divided into high and low ALDH1 expression. Survival was associated with expression in the primary tumor (9 versus 23 mo, P = 0.0016) expression but not peritumoral tissue (21 versus 20.5 mo, P = 0.32), normal colon (19 versus 27 mo, P = 0.289), or lymph node metastasis (23 versus 21 mo, P = 0.69). On univariate analysis, ALDH1 expression and grade were associated with survival but ages, number of lymph node metastasis, race, or grade were not associated. On multivariate analysis, only ALDH1 status continued to be associated with survival, odds ratio 4.4, and P = 0.011.

CONCLUSIONS

ALDH1 is indicative of stemness and is a biomarker marker in colon cancer. Expression did not increase with progression from normal colon to primary tumors and metastasis.

DNA methyltransferases: a novel target for prevention and therapy

Cancer is the second leading cause of death in US. Despite the emergence of new, targeted agents, and the use of various therapeutic combinations, none of the available treatment options are curative in patients with advanced cancer. Epigenetic alterations are increasingly recognized as valuable targets for the development of cancer therapies. DNA methylation at the 5-position of cytosine, catalyzed by DNA methyltransferases (DNMTs), is the predominant epigenetic modification in mammals. DNMT1, the major enzyme responsible for maintenance of the DNA methylation pattern is located at the replication fork and methylates newly biosynthesized DNA. DNMT2 or TRDMT1, the smallest mammalian DNMT is believed to participate in the recognition of DNA damage, DNA recombination, and mutation repair. It is composed solely of the C-terminal domain, and does not possess the regulatory N-terminal region. The levels of DNMTs, especially those of DNMT3B, DNMT3A, and DNMT3L, are often increased in various cancer tissues and cell lines, which may partially account for the hypermethylation of promoter CpG-rich regions of tumor suppressor genes in a variety of malignancies. Moreover, it has been shown to function in self-renewal and maintenance of colon cancer stem cells and need to be studied in several cancers. Inhibition of DNMTs has demonstrated reduction in tumor formation in part through the increased expression of tumor suppressor genes. Hence, DNMTs can potentially be used as anti-cancer targets. Dietary phytochemicals also inhibit DNMTs and cancer stem cells; this represents a promising approach for the prevention and treatment of many cancers.

Tumor initiating cells and chemoresistance: which is the best strategy to target colon cancer stem cells?

There is an emerging body of evidence that chemoresistance and minimal residual disease result from selective resistance of a cell subpopulation from the original tumor that is molecularly and phenotypically distinct. These cells are called “cancer stem cells” (CSCs). In this review, we analyze the potential targeting strategies for eradicating CSCs specifically in order to develop more effective therapeutic strategies for metastatic colon cancer. These include induction of terminal epithelial differentiation of CSCs or targeting some genes expressed only in CSCs and involved in self-renewal and chemoresistance. Ideal targets could be cell regulators that simultaneously control the stemness and the resistance of CSCs. Another important aspect of cancer biology, which can also be harnessed to create novel broad-spectrum anticancer agents, is the Warburg effect, also known as aerobic glycolysis. Actually, little is yet known with regard to the metabolism of CSCs population, leaving an exciting unstudied avenue in the dawn of the emerging field of metabolomics.

Defining suitable reference genes for RT-qPCR analysis on intestinal epithelial cells

The study of the mammalian intestinal epithelium concerns several aspects of cellular and molecular biology. In fact, most of these studies aim to define molecular components or mechanisms related with the control of stemness and the balance between cell proliferation and differentiation in physiopathological conditions. It is worth mentioning that real-time quantitative reverse transcription-polymerase chain reaction (RT-qPCR) approaches are commonly used, but only a few studies are available regarding suitable reference genes to normalize gene expression data. The present study was designed to validate potential reference genes in freshly isolated proliferating or differentiated epithelial cells from the mouse intestine. We also extended our analysis to the IEC6 intestinal epithelial cells, as a promising model to study intestinal physiopathology in vitro. The stability of six potential reference genes (Hprt1, Ppia, Gapdh, Rplp0, Ppib, and Vil1) has been tested both in epithelial cells isolated from the mouse intestine and in the IEC6 cell line. The software programs-geNorm and Normfinder-were used to obtain an estimation of the expression stability of each gene and, by comparing the results, to identify the most suitable genes for RT-qPCR data normalization. These multiple approaches allowed us to select different suitable reference genes for the correct quantification of mRNAs depending on the differentiated or proliferative nature of the cells.

Overexpression of Lgr5 correlates with resistance to 5-FU-based chemotherapy in colorectal cancer

BACKGROUND

The leucine-rich repeat-containing G protein-coupled receptor 5 (Lgr5) is an adult intestinal stem cell marker frequently detected in human colorectal cancers (CRCs). However, the value of Lgr5 level in CRC prognosis and treatment prediction has not been well characterized.

METHODS

We examined Lgr5 expression in 384 formalin-fixed paraffin-embedded CRC specimens from 296 CRC patients, including 64 patients treated with 5-fluorouracil (5-FU)-based chemotherapy. The effects of Lgr5 on cell proliferation, survival, and drug resistance were examined in cultured CRC cells.

RESULTS

Elevated expression of Lgr5 was observed in CRC tissues, and Lgr5 protein levels were significantly correlated with an advanced American Joint Committee on Cancer stage (P < 0.001), T stage (P < 0.001), N stage (P < 0.001), and distant metastasis (P < 0.001). High expression levels of Lgr5 were significantly associated with shorter disease-free survival (P < 0.001) and shorter cancer-specific survival (P = 0.007) in CRC patients. Among the chemotherapy-treated subgroups, patients with low Lgr5 level showed a better response rate (65 %) than patients with high Lgr5 level (37 %) towards 5-FU-based treatment (P = 0.025). In cultured CRC cell lines, knocking down Lgr5 suppressed cell proliferation and colony formation ability, while it enhanced apoptosis and rendered cells more sensitive to chemotherapeutic agents. In contrast, overexpression of Lgr5 increased cell proliferation and enhanced chemoresistance.

CONCLUSION

These results suggest that elevated Lgr5 level is associated with CRC progression and treatment response and has the potential to serve as a therapeutic target in CRC patients.

Colorectal adenoma stem-like cell populations: associations with adenoma characteristics and metachronous colorectal neoplasia

Cancer stem cells have tumor-initiation and tumor-maintenance capabilities. Stem-like cells are present in colorectal adenomas, but their relationship to adenoma pathology and patient characteristics, including metachronous development of an additional adenoma ("recurrence"), has not been studied extensively. We evaluated the expression of aldehyde dehydrogenase isoform 1A1 (ALDH1A1), a putative stem cell marker, in baseline adenomas from the placebo arm of chemoprevention trial participants with colonoscopic follow-up. An exploratory set of 20 baseline adenomas was analyzed by ALDH1A1 immunohistochemistry with morphometry, and a replication set of 89 adenomas from 76 high-risk participants was evaluated by computerized image analysis. ALDH1A1-labeling indices (ALI) were similar across patient characteristics and in advanced and nonadvanced adenomas. There was a trend toward higher ALIs in adenomas occurring in the right than left colon (P = 0.09). ALIs of synchronous adenomas were correlated (intraclass correlation coefficient 0.67). Participants in both sample sets who developed a metachronous adenoma had significantly higher ALIs in their baseline adenoma than participants who remained adenoma free. In the replication set, the adjusted odds for metachronous adenoma increased 1.46 for each 10% increase in ALIs (P = 0.03). A best-fit algorithm-based cutoff point of 22.4% had specificity of 75.0% and positive predictive value of 70.0% for metachronous adenoma development. A larger population of ALDH1A1-expressing cells in an adenoma is associated with a higher risk for metachronous adenoma, independent of adenoma size or histopathology. If confirmed, ALDH1A1 has potential as a novel biomarker in risk assessment and as a potential stem cell target for chemoprevention.

Aptamer-conjugated nanorods for targeted photothermal therapy of prostate cancer stem cells

Prostate cancer results in about 30,000 deaths annually in the United States, making it the second leading cause of cancer mortality in men in the Western world. Therefore, it is of great significance to capture and kill prostate cancer cells. It is well known that cancer stem cells are responsible for the maintenance and metastasis of tumors. This concept offers the possibility of developing a selective therapeutic approach in which cancer stem cells are directly targeted and killed. In this work, aptamers selected against DU145 prostate cancer cells (aptamer CSC1) and their subpopulation of cancer stem cells (aptamer CSC13) were linked to the surfaces of gold nanorods (AuNRs), and the resulting conjugates were successfully used to target and kill both cancer cells and cancer stem cells by near-infrared (NIR) laser irradiation. Even though cancer stem cells represent only a small population among all cancer cells, the entire cell viability was very low after laser irradiation, suggesting that tumorigenesis could be successfully controlled by this aptamer-based method, thus paving the way for early diagnosis and targeted therapy.

Colon cancer stem cells: Controversies and perspectives

Tumors have long been viewed as a population in which all cells have the equal propensity to form new tumors, the so called conventional stochastic model. The cutting-edge theory on tumor origin and progression, tends to consider cancer as a stem cell disease. Stem cells are actively involved in the onset and maintenance of colon cancer. This review is intended to examine the state of the art on colon cancer stem cells (CSCs), with regard to the recent achievements of basic research and to the corresponding translational consequences. Specific prominence is given to the hypothesized origin of CSCs and to the methods for their identification. The growing understanding of CSC biology is driving the optimization of novel anti-cancer targeted drugs.

CD133 expression is not an independent prognostic factor in stage II and III colorectal cancer but may predict the better outcome in patients with adjuvant therapy

Background

Cancer stem cells (CSCs) are notorious for their capacity of tumor progression, metastasis or resistance to chemo-radiotherapy. However, the undisputed role of cancer stem marker, CD133, in colorectal cancers (CRCs) is not clear yet.

Methods

We assessed 271 surgically-resected stage II and III primary CRCs with (171) and without (100) adjuvant therapy after surgery. CD133 expression was analyzed by immunohistochemical (IHC) staining and real-time RT-PCR. CD133 promoter methylation was quantified by pyrosequencing.

Results

The CD133 IHC expression was significantly correlated with mRNA expression (p=0.0257) and inversely correlated with the promoter methylation (p=0.0001). CD133 was expressed more frequently in rectal cancer (p=0.0035), and in moderately differentiated tumors (p=0.0378). In survival analysis, CD133 expression was not significantly correlated with overall survival (OS) (p=0.9689) as well as disease-free survival (DFS) (p=0.2103). However, CD133+ tumors were significantly associated with better OS in patients with adjuvant therapy compared to those without adjuvant therapy (p<0.0001, HR 0.125, 95% CI 0.052-0.299). But the patients with CD133- tumors did not show any significant difference of survival according to adjuvant therapy (p=0.055, HR 0.500, 95% CI 0.247-1.015).

Conclusions

In stage II and III CRCs, CD133 IHC expression may signify the benefit for adjuvant therapy although it is not an independent prognostic factor.

Endothelial progenitor cells: current issues on characterization and challenging clinical applications

Since their discovery about a decade ago, endothelial precursor cells (EPC) have been subjected to intensive investigation. The vision to stimulate respectively suppress a key player of vasculogenesis opened a plethora of clinical applications. However, as research opened deeper insights into EPC biology, the enthusiasm of the pioneer era has been damped in favour of a more critical view. Recent research is focused on three major questions: The fact that the number of EPC in peripheral blood is exceedingly low has consistently raised suspicion whether these cells can plausibly have an impact on physiological or pathophysiological processes. Secondly, whereas the key role of EPC in tumourigenesis has been strongly emphasized by various groups in the past, recent publications are challenging this hypothesis. Thirdly, the lack of consensus on EPC-defining markers and standardized protocols for their detection have repeatedly led to difficulties concerning comparability between papers. In this current review, an overview on recent findings on EPC biology is given, their challenging clinical implications are discussed and the perplexity underlying the current controversial debate is illustrated.

Rapid re-expression of CD133 protein in colorectal cancer cell lines in vitro and in vivo

Studies related to the cancer stem cell hypothesis are challenging because of the imperfect tools to identify cell populations of interest and controversy on the usefulness of established cancer cell lines. We previously found CD133 to not be selective for a tumor-propagating or radioresistant population in a near-diploid, microsatellite-instable colorectal carcinoma (CRC) cell line. Because of discrepant literature data, we herein systematically analyzed the behavior of microsatellite-stable cell line subpopulations reflecting the more frequent carcinogenesis pathway in spontaneous CRC. CD133⁺ and CD133(-/low) populations were isolated by fluorescence-activated cell sorting and further processed. HT29 and SW620 cells were studied in detail in monolayer and/or spheroid culture assays and upon subcutaneous injection in NMRI (nu/nu) mice using a limiting dilution approach. CD133(-/low) HT29 cells showed a significantly lower clonogenic survival and reduced spheroid formation capacity than their CD133⁺ counterparts. However, the cell populations neither differed in growth kinetics and response to treatment in vitro nor in tumor formation capacity when injecting as low as 10 cells. CD133(-/low) HT29 cells rapidly re-expressed CD133 protein in vitro and in vivo as shown by flow cytometry and/or western blot analyses, and they also showed a particular survival benefit under tissue normoxic conditions. In contrast, CD133 protein in the CD133⁺ population was quite stable throughout culturing. The observation of CD133 re-expression and lack of difference in tumor take rate of subpopulations was confirmed in SW620 cells. Here, we found cell density to affect CD133 re-expression in the CD133(-)-sorted population. And even SW480 cells, classified as a CD133⁻ cell line, presented some CD133 protein on their surface upon in vivo engraftment. We conclude that (i) CD133 protein expression shows high plasticity in CRC cell lines, and (ii) in vitro CD133 status on the cell surface neither determines tumorigenic potential nor CD133 profile in vivo.

miRNA expression profile of colon cancer stem cells compared to non-stem cells using the SW1116 cell line

Colorectal cancer (CRC) is one of the major causes of cancer-related mortality worldwide. Recent studies revealed that there is a relationship between CRC occurrence and microRNA (miRNA) function. Stem cells are a type of cells that have the ability to self-renew and to proliferate extensively while maintaining the undifferentiated state. Cancer stem cells (CSCs) are closely linked to tumor recurrence and metastasis. To this end, we evaluated the miRNA expression differences between colon CSCs and non-stem cells using the SW1116 cell line, to determine the relationship between tumor stem cells and tumor biological behavior. We isolated populations of colon CSCs with the CD133+/CD44+ and CD133-/CD44- surface phenotype from a human SW1116 colon adenocarcinoma cell line using flow cytometry. The expression of miRNA and mRNA of both sets of cells was examined with miRNA and mRNA arrays. Bioinformatic methods were used to analyze microarray results. We completed gene ontology analysis, pathway analysis, miRNA target gene prediction with databases. We identified a colon stem cell miRNA expression profile comprising 31 upregulated and 31 downregulated miRNAs, such as miR29a, miR29b, miR449b and miR4524. Some of these differentially expressed miRNAs may be involved in the regulation of stem cell differentiation. Gene ontology and pathway analyses showed that the differences are closely related to the function of the cell cycle, cell differentiation, signaling pathway, cytoskeletal proteins and cell-matrix adhesion in colon cancer stem cells. We found that miRNAs play an important role in regulating the expression of colon CSC characteristics. By regulating the expression of CSC signaling pathways, cytoskeleton and membrane proteins, miRNAs give tumor stem cells the macrobiological behavior of recurrence and metastasis. This study provides a new perspective on CRC metastasis and recurrence.

Expression of Abelson interactor 1 (Abi1) correlates with inflammation, KRAS mutation and adenomatous change during colonic carcinogenesis

Background

Abelson interactor 1 (Abi1) is an important regulator of actin dynamics during cytoskeletal reorganization. In this study, our aim was to investigate the expression of Abi1 in colonic mucosa with and without inflammation, colonic polyps, colorectal carcinomas (CRC) and metastases as well as in CRC cell lines with respect to BRAF/KRAS mutation status and to find out whether introduction of KRAS mutation or stimulation with TNFalpha enhances Abi1 protein expression in CRC cells.

Methodology/Principal Findings

We immunohistochemically analyzed Abi1 protein expression in 126 tissue specimens from 95 patients and in 5 colorectal carcinoma cell lines with different mutation status by western immunoblotting. We found that Abi1 expression correlated positively with KRAS, but not BRAF mutation status in the examined tissue samples. Furthermore, Abi1 is overexpressed in inflammatory mucosa, sessile serrated polyps and adenomas, tubular adenomas, invasive CRC and CRC metastasis when compared to healthy mucosa and BRAF-mutated as well as KRAS wild-type hyperplastic polyps. Abi1 expression in carcinoma was independent of microsatellite stability of the tumor. Abi1 protein expression correlated with KRAS mutation in the analyzed CRC cell lines, and upregulation of Abi1 could be induced by TNFalpha treatment as well as transfection of wild-type CRC cells with mutant KRAS. The overexpression of Abi1 could be abolished by treatment with the PI3K-inhibitor Wortmannin after KRAS transfection.

Conclusions/Significance

Our results support a role for Abi1 as a downstream target of inflammatory response and adenomatous change as well as oncogenic KRAS mutation via PI3K, but not BRAF activation. Furthermore, they highlight a possible role for Abi1 as a marker for early KRAS mutation in hyperplastic polyps. Since the protein is a key player in actin dynamics, our data encourages further studies concerning the exact role of Abi1 in actin reorganization upon enhanced KRAS/PI3K signalling during colonic tumorigenesis.

Colorectal cancer stem cells

Colorectal cancer (CRC) is one of the most commonly diagnosed and lethal cancers worldwide. It is a multistep process that requires the accumulation of genetic/epigenetic aberrations. There are several issues concerning colorectal carcinogenesis that remain unanswered, such as the cell of origin and the type of cells that propagate the tumor after its initiation. There are two models of carcinogenesis: the stochastic and the cancer stem cell (CSC) model. According to the stochastic model, any kind of cell is capable of initiating and promoting cancer development, whereas the CSC model suggests that tumors are hierarchically organized and only CSCs possess cancer-promoting potential. Moreover, various molecular pathways, such as Wingless/Int (Wnt) and Notch, as well as the complex crosstalk network between microenvironment and CSCs, are involved in CRC. Identification of CSCs remains controversial due to the lack of widely accepted specific molecular markers. CSCs are responsible for tumor relapse, because conventional drugs fail to eliminate the CSC reservoir. Therefore, the design of CSC-targeted interventions is a rational target, which will enhance responsiveness to traditional therapeutic strategies and reduce local recurrence and metastasis. This review discusses the implications of the newly introduced CSC model in CRC, the markers used up to now for CSC identification, and its potential implications in the design of novel therapeutic approaches.

MicroRNA-451 is involved in the self-renewal, tumorigenicity, and chemoresistance of colorectal cancer stem cells

Many antitumor therapies affect rapidly dividing cells. However, tumor proliferation may be driven by cancer stem cells (CSCs), which divide slowly and are relatively resistant to cytotoxic drugs. Thus, many tumors may progress because CSCs are not sensitive to the treatment. In this work, we searched for target genes whose expression is involved in proliferation and chemoresistance of CSCs. Both of these processes could be controlled simultaneously by cell regulators such as microRNAs (miRNAs). Therefore, colonospheres with properties of CSCs were obtained from different colon carcinoma cells, and miRNA profiling was performed. The results showed that miR-451 was downregulated in colonspheres versus parental cells. Surprisingly, expression of miR-451 caused a decrease in self-renewal, tumorigenicity, and chemoresistance to irinotecan of colonspheres. We identified cyclooxygenase-2 (COX-2) as an indirect miR-451 target gene involved in sphere growth. Our results indicate that miR-451 downregulation allows the expression of the direct target gene macrophage migration inhibitory factor, involved in the expression of COX-2. In turn, COX-2 allows Wnt activation, which is essential for CSC growth. Furthermore, miR-451 restoration decreases expression of the ATP-binding cassette drug transporter ABCB1 and results in irinotecan sensitization. These findings correlate well with the lower expression of miR-451 observed in patients who did not respond to irinotecan-based first-line therapy compared with patients who did. Our data suggest that miR-451 is a novel candidate to circumvent recurrence and drug resistance in colorectal cancer and could be used as a marker to predict response to irinotecan in patients with colon carcinoma.

Ascl2 knockdown results in tumor growth arrest by miRNA-302b-related inhibition of colon cancer progenitor cells

BACKGROUND

Achaete scute-like 2 (Ascl2), a basic helix-loop-helix (bHLH) transcription factor, controls the fate of intestinal stem cells. However, the role of Ascl2 in colon cancer progenitor cells remains unknown. The cell line HT-29 (47.5-95% of CD133(+) population) and LS174T (0.45% of CD133(+) population) were chosen for functional evaluation of Ascl2 in colon cancer progenitor cells after gene knockdown by RNA interference.

METHODOLOGY/PRINCIPAL FINDINGS

Immunohistochemistry demonstrated that Ascl2 was significantly increased in colorectal adenocarcinomas. Downregulation of Ascl2 using RNA interference in cultured colonic adenocarcinoma HT-29 and LS174T cells reduced cellular proliferation, colony-forming ability, invasion and migration in vitro, and resulted in the growth arrest of tumor xenografts in vivo. The Ascl2 protein level in CD133(+) HT-29 cells was significantly higher than in CD133(-) HT-29 cells. Ascl2 blockade via shRNA interference in HT-29 cells (shRNA-Ascl2/HT-29 cells) resulted in 26.2% of cells staining CD133(+) compared with 54.7% in control shRNA-Ctr/HT-29 cells. The levels of 'stemness' associated genes, such as CD133, Sox2, Oct4, Lgr5, Bmi1, and C-myc, were significantly decreased in shRNA-Ascl2/HT-29 and shRNA-Ascl2/LS174T cells in vitro as well as in the corresponding tumor xenograft (CD133 was not performed in shRNA-Ascl2/LS174T cells). The shRNA-Ascl2/HT-29 cells had inhibited abilities to form tumorspheres compared with control. The microRNA (miRNAs) microarrays, identified 26 up-regulated miRNAs and 58 down-regulated miRNAs in shRNA-Ascl2/HT-29 cells. Expression levels of let-7b, miRNA-124, miRNA-125b, miRNA-17, miRNA-20a and miRNA-302b, involved in the regulation of 'stemness', were quantified with qPCR, which confirmed their identities. Restoration of miRNA-302b, via its mimic, led to the restoration of shRNA-Ascl2/HT-29 'stemness' characteristics, including tumorsphere formation and 'stemness' associated genes levels, and the recovery of cellular behaviors, including colony-forming ability, invasion and migration in vitro.

CONCLUSIONS/SIGNIFICANCE

Ascl2 may be a potential target for the inhibition of colon cancer progenitor cells, and functions through a miR-302b-related mechanism.

Interleukin-12 inhibits the survival of human colon cancer stem cells in vitro and their tumor initiating capacity in mice

Interleukin-12 (IL-12) is a potent immunomodulatory cytokine with unknown direct effect on the property of cancer stem cells (CSCs). In this study, we investigated the capacity of IL-12 to regulate the self-renewal and differentiation of human colon CSCs in vitro, as well as the effect of IL-12 on the growth of tumors initiated by CSCs in mice. After over-expression of IL-12 with lentiviral transfection, CSCs exhibited reduced invasiveness and tumorsphere formation in association with increased apoptosis in vitro. After injection into NOD/SCID mice, tumors initiated by CSCs transfected with IL-12 showed markedly reduced rate of growth. Mechanistic studies revealed that over-expression of IL-12 reduced the expression of IL-4 and STAT6 in CSCs. Thus, our study demonstrates a potentially beneficial role of IL-12 in directly limiting the malignant phenotype of CSCs.

Molecular markers in circulating tumour cells from metastatic colorectal cancer patients

The prognosis of metastatic cancer patients is still largely affected by treatment failure, mainly due to drug resistance. The hypothesis that chemotherapy might miss circulating tumour cells (CTCs) and particularly a subpopulation of more aggressive, stem-like CTCs, characterized by multidrug resistance, has been recently raised. We investigated the prognostic value of drug resistance and stemness markers in CTCs from metastatic colorectal cancer patients treated with oxaliplatin (L-OHP) and 5-fluoruracil (5-FU) based regimens. Forty patients with metastatic colorectal cancer were enrolled. CTCs were isolated from peripheral blood and analysed for the expression of aldheyde dehydrogenase 1 (ALDH1), CD44, CD133 (used as markers of stemness), multidrug resistance related protein 5 (MRP5 used as marker of resistance to 5-FU and L-OHP) and survivin (used as a marker of apoptosis resistance). CTCs were found in 27/40 (67%) patients. No correlation was found between the expression of either CD44 and CD133 in CTCs and the outcome of patients, while a statistically significant shorter progression-free survival was found in patients with CTCs positive for the expression of ALDH1, survivin and MRP5. These results support the idea that isolating survivin and MRP5+ CTCs may help in the selection of metastatic colorectal cancer patients resistant to standard 5-FU and L-OHP based chemotherapy, for which alternative regimens may be appropriate.