The Prognostic Value of Decreased KLF4 in Digestive System Cancers: A Meta-Analysis from 17 Studies

Background

The prognostic value of loss of Krüppel-like factor 4 (KLF4) expression in digestive system cancers has not reached a consensus. This study aimed for a comprehensive investigation of the internal associations between KLF4 expression loss and prognostic implications in patients with digestive system cancers.

Methods

We searched for all relevant literatures in the electronic databases until February 1, 2017. The degree of association between KLF4 and prognosis was evaluated by pooled hazard ratios (HRs) as well as relevant 95% confidence intervals (95% CIs).

Results

Seventeen eligible studies with 2118 patients revealed that loss of KLF4 expression was connected with poor prognosis, with the pooled HRs of 1.61 (95% CI: 1.17–2.20, P = 0.003) for the overall survival (OS) and 1.99 (95% CI: 1.12–3.52, P = 0.001) for the disease-free survival (DFS)/recurrence-free survival (RFS)/metastasis-free survival (MFS). Additionally, loss of KLF4 expression was also related to a worse disease-special survival (DSS) yielding a pooled HR of 1.73 (95% CI: 1.08–2.77, P = 0.022).

Conclusion

Our findings suggest that loss of KLF4 expression is correlated with a bad outcome in most digestive system cancers, apart from esophagus squamous cell carcinoma (ESCC).

Ribonucleic acid interference knockdown of IL-6 enhances the efficacy of cisplatin in laryngeal cancer stem cells by down-regulating the IL-6/STAT3/HIF1 pathway

Background

Cisplatin has been used in the treatment of many cancers, including laryngeal cancer; however, its efficacy can be reduced due to the development of drug resistance. This study aimed to investigate whether interleukin-6 (IL-6) knockdown may enhance the efficacy of cisplatin in laryngeal cancer stem cells (CSC) and the potential involvement of the signal transducer and activator of transcription 3 (STAT3) and hypoxia-inducible factor 1 (HIF1) in this effect.

Methods

The ALDH+ and CD44+ CSC in Hep2 human laryngeal squamous cancer cells were identified by the fluorescence-activated cell sorting technique. IL-6, STAT3 and HIF1 mRNA and protein expressions were examined with quantitative real-time polymerase chain reaction and Western blot, respectively. Cell proliferation was measured by MTT assay. Tumorigenicity was measured by a colony formation assay and invasion was determined by a cell invasion assay. Apoptotic cells were counted by flow cytometry. Immunohistochemistry was performed to detect immunoreactive IL-6, STAT3 and HIF1 cells in xenografts.

Results

The mRNA and protein levels of IL-6, STAT3 and HIF1 were significantly increased in Hep2-CSC as compared with those from Hep2 cells. Application of siRNA-IL-6 to knockdown IL-6 resulted in significantly decreased IL-6, STAT3 and HIF1 mRNA and protein levels. IL-6 knockdown reduced cell proliferation, tumorigenicity and invasion and increased apoptosis within CSC. Enhanced degrees of suppression in these parameters were observed when IL-6 knockdown was combined with cisplatin in these CSC. Results from the xenograft study showed that the combination of IL-6 knockdown and cisplatin further inhibited the growth of xenografts as compared with that obtained in the cisplatin-injected group alone. Immunoreactive IL-6, STAT3 and HIF1 cell numbers were markedly reduced in IL-6 knockdown tumor tissues. IL-6, STAT3 and HIF1 immunoreactive cell counts were further reduced in tissue where IL-6 knockdown was combined with cisplatin treatment as compared with tissue receiving cisplatin alone.

Conclusions

IL-6 knockdown can increase chemo-drug efficacy of cisplatin, inhibit tumor growth and reduce the potential for tumor recurrence and metastasis in laryngeal cancer. The IL-6/STAT3/HIF1 pathway may represent an important target for investigating therapeutic strategies for the treatment of laryngeal cancer.

Novel crosstalk between KLF4 and ZEB1 regulates gemcitabine resistance in pancreatic ductal adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC) is one of the most lethal malignancies with broad resistance to chemotherapeutic drugs. Krüppel-like factor 4 (KLF4) is a candidate tumor suppressor in PDAC. However, the precise role of KLF4 in gemcitabine resistance of PDAC remains largely unclear. In this study, we demonstrated that gemcitabine inhibited KLF4 expression. Moreover, gemcitabine also reduced the levels of miR‑200b and miR‑183, but promoted ZEB1 expression in PDAC cells. KLF4 knockdown blocked the expression of miR‑200b and miR‑183, and inversely, KLF4 overexpression promoted the expression of miR‑200b and miR‑183, suggesting that KLF4 positively regulated the expression of miR‑200b and miR‑183. Moreover, KLF4 knockdown enhanced ZEB1 expression and gemcitabine resistance while KLF4 overexpression induced the opposite effect. ChIP assays verified that KLF4 positively regulated the expression of miR‑200b and miR‑183 by directly binding to their promoters. Then, miR‑200b and miR‑183 directly inhibited ZEB1 expression by targeting its 3'UTR region. ZEB1 knockdown attenuated gemcitabine resistance in PDAC cells. KLF4 overexpression promoted gemcitabine sensitivity of PDAC in vivo by negatively regulating ZEB1 expression. Our results revealed that novel crosstalk between KLF4 and ZEB1 regulated gemcitabine resistance in PDAC.

Harnessing the BMP signaling pathway to control the formation of cancer stem cells by effects on epithelial-to-mesenchymal transition

Cancer stem cells (CSCs) persist in tumors as a distinct population and may be causative in metastasis and relapse. CSC-rich tumors are associated with higher rates of metastasis and poor patient prognosis. Targeting CSCs therapeutically is challenging, since they seem to be resistant to standard chemotherapy. We have shown that a novel peptide agonist of bone morphogenetic protein (BMP) signaling, P123, is capable of inhibiting the growth of primary tumor cells by interacting with type I receptors selectively [activin receptor-like kinase 2 (ALK2) and ALK3, but not ALK6] and type II BMP receptors, activating SMAD 1/5/8 signaling and controlling the cell cycle pathway. Furthermore, the compound is capable of blocking transforming growth factor-β induced epithelial-to-mesenchymal transition (EMT) in primary tumor cells, a critical step for tumor progression and metastasis. In addition, we have investigated the effects of P123 on self-renewal, growth, differentiation (reversal of EMT) and apoptosis of isolated human breast CSCs. We have shown that P123 and BMP-7 reverse the EMT process in human breast CSCs, and inhibit self-renewal and growth. Moreover, compared with single treatment with paclitaxel, co-treatment with paclitaxel and P123 showed an increase in cell apoptosis. Together, these findings suggest that P123 has the therapeutic potential to suppress both bulk tumor cells and CSCs. We believe that P123 represents a new class of drugs that have the potential to eliminate the primary tumor, prevent reoccurrence and metastasis, and enhance the treatment of breast cancer.

Cancer stem cell markers in patterning differentiation and in prognosis of oral squamous cell carcinoma

Differentiation is a major histological parameter determining tumor aggressiveness and prognosis of the patient; cancer stem cells with their slow dividing and undifferentiated nature might be one of the factors determining the same. This study aims to correlate cancer stem cell markers (CD44 and CD147) with tumor differentiation and evaluate their subsequent effect on prognosis. Immunohistochemical analysis in treatment naïve oral cancer patients (n = 53) indicated that the expression of CD147 was associated with poorly differentiated squamous cell carcinoma and moderately differentiated squamous cell carcinoma (p < 0.01). Furthermore, co-expression analysis showed that 45% each of moderately differentiated squamous cell carcinoma and poorly differentiated squamous cell carcinoma patients were CD44^high/CD147^high as compared to only 10% of patients with well-differentiated squamous cell carcinoma. A three-way analysis indicated that differentiation correlated with recurrence and survival (p < 0.05) in only the patients with CD44^high/CD147^high cohort. Subsequently, relevance of these cancer stem cell markers in patterning the differentiation characteristics was evaluated in oral squamous cell carcinoma cell lines originating from different grades of oral cancer. Flowcytometry-based analysis indicated an increase in CD44⁺/CD147⁺ cells in cell lines of poorly differentiated squamous cell carcinoma (94.35 ± 1.14%, p < 0.001) and moderately differentiated squamous cell carcinoma origin (93.49 ± 0.47%, p < 0.001) as compared to cell line of well-differentiated squamous cell carcinoma origin (23.12% ± 0.49%). Expression profiling indicated higher expression of cancer stem cell and epithelial-mesenchymal transition markers in SCC029B (poorly differentiated squamous cell carcinoma originated; p ≤ 0.001), which was further translated into increased spheroid formation, migration, and invasion (p < 0.001) as compared to cell line of well-differentiated squamous cell carcinoma origin. This study suggests that CD44 and CD147 together improve the prognostic efficacy of tumor differentiation; in vitro results further point out that these markers might be determinant of differentiation characteristics, imparting properties of increased self-renewal, migration, and invasion.

Cancer stem cells and epithelial-mesenchymal transition in urothelial carcinoma: Possible pathways and potential therapeutic approaches

There is growing evidence of the presence of cancer stem cells in urothelial carcinoma. Cancer stem cells have the ability to self-renew and to differentiate into all cell types of the original heterogeneous tumor. A panel of diverse cancer stem cell markers might be suitable for simulation studies of urothelial cancer stem cells and for the development of optimized treatment protocols. The present review focuses on the advances in recognizing the markers of urothelial cancer stem cells and possible therapeutic targets. The commonly reported markers and pathways that were evaluated include CD44, CD133, ALDH1, SOX2 & SOX4, BMI1, EZH1, PD-L1, MAGE-A3, COX2/PGE2/STAT3, AR, and autophagy. Studies on the epithelial-mesenchymal transition-related pathways (Shh, Wnt/β-catenin, Notch, PI3K/Akt, TGF-β, miRNA) are also reviewed. Most of these markers were recognized through the expression patterns of cancer stem cell-rich side populations. Their regulative role in the development and differentiation of urothelial cancer stem cells was confirmed in vitro by functional analyses (e.g. cell migration, colony formation, sphere formation), and in vivo in xenograft experiments. Although a small number of these pathways are targeted by currently available drugs or drugs that are the currently being tested in clinical trials, a clear treatment approach has not been developed for most pathways. A greater understanding of the mechanisms that control the proliferation and differentiation of cancer stem cells is expected to lead to improvements in targeted therapy.

Krüppel-Like Factor 4 Enhances Sensitivity of Cisplatin to Esophageal Squamous Cell Carcinoma (ESCC) Cells

Background

The aim of this study was to elucidate the role of Krüppel-Like factor 4 (KLF4) in cisplatin resistance in esophageal squamous cell carcinoma (ESCC) cells, which may eventually help to improve the treatment efficacy.

Material/Methods

Human esophageal squamous cell carcinoma (ESCC) cell line CaEs-17, TE-1, EC109, KYSE510, KYSE140, KYSE70, and KYSE30 were selected to detect their sensitivity to cisplatin. 5-Azacytidine-2′-deoxycytidine (5′-Aza-CdR) treatment and methylation-specific PCR (MS-PCR) were used to detect the methylation status for KLF4. Cell viability, apoptosis, and cell cycle were measured using methyl thiazolyl tetrazolium (MTT) assay, Annexin V affinity assay, and flow cytometry, respectively.

Results

The sensitivity to cisplatin was different in the seven ESCC cell lines, with TE-1 having the lowest sensitivity and KYSE140 having the highest sensitivity. Interestingly, the level of KLF4 was relatively low in TE-1 cells; while it was high in KYSE140 cells. These results suggested that KLF4 may be involved in cisplatin resistance. The promoter region was mostly unmethylated in KYSE140 cells; while it was hypermethylated in TE-1 cells. After treatment with demethylation reagent 5-Aza-CdR, cisplatin sensitivities were significantly increased after upregulation of KLF4, as the IC50 values were significantly decreased in the TE-1 cell treated with 5-Aza-CdR. Furthermore, upregulation of KLF4 induced cell apoptosis and cell cycle arrest at S phase.

Conclusions

KLF4 enhances the sensitivity of cisplatin to ESCC cells through apoptosis induction and cell cycle arrest. Our data provided a novel insight to the mechanism of cisplatin resistance; overexpression of KLF4 may be a potential therapeutic strategy for cisplatin resistance in human ESCC.

CD44v8-10 as a potential theranostic biomarker for targeting disseminated cancer cells in advanced gastric cancer

Gastric cancer is the third most common cause of cancer mortality, and the survival rate of stage IV advanced gastric cancer (AGC) patients with distant metastasis is very low. Thus, the detection and eradication of disseminated cancer cells by targeting cell surface molecules in AGC would improve patient survival. The hyaluronic acid receptor, CD44, has various isoforms generated by alternative splicing, and some isoforms are known to be correlated to gastric cancer. In this study, to find out the most appropriate CD44v for targeting AGC, we analysed the expression differences of CD44 isoforms at the mRNA level in stomach cancer cell lines as well as in 74 patients with AGC by using exon-specific qRT-PCR. Among the CD44v isoforms, CD44v8-10 was determined as the most promising biomarker for the development of theranostic agents of gastric cancer. Next, we synthesised the conjugate of anti-CD44v9 antibody with near-infrared fluorophore or photosensitiser, and then demonstrated its feasibility for target cell-specific imaging and photoimmunotherapy in gastric cancer. As a result, these conjugates have clearly demarcated the surface of CD44v8-10 expressing cancer cells and showed efficient phototoxic effects. Therefore, this study revealed that CD44v8-10 is the efficient theranostic biomarker to target disseminated cancer cells in AGC.

Multifaceted Interpretation of Colon Cancer Stem Cells

Colon cancer is one of the leading causes of cancer-related deaths worldwide, despite recent advances in clinical oncology. Accumulating evidence sheds light on the existence of cancer stem cells and their role in conferring therapeutic resistance. Cancer stem cells are a minor fraction of cancer cells, which enable tumor heterogeneity and initiate tumor formation. In addition, these cells are resistant to various cytotoxic factors. Therefore, elimination of cancer stem cells is difficult but essential to cure the malignant foci completely. Herein, we review the recent evidence for intestinal stem cells and colon cancer stem cells, methods to detect the tumor-initiating cells, and clinical significance of cancer stem cell markers. We also describe the emerging problems of cancer stem cell theory, including bidirectional conversion and intertumoral heterogeneity of stem cell phenotype.

Variant CD44 expression is enriching for a cell population with cancer stem cell-like characteristics in human lung adenocarcinoma

Background: Preliminary studies have identified cancer stem cells (CSCs) in various cancers and there are several ongoing clinical studies targeting these cells. CD44 (standard or variant isoforms) and/or aldehyde dehydrogenase (ALDH) expression is the most commonly used markers for the identification of CSCs. The goal of the current study was to examine the ability of CD44v, either alone or in combination with ALDH, to identify CSCs within human lung cancer cells lines.

Methods: We examined several lung adenocarcinoma cell lines for the ability of CD44v and/or ALDH expression to enrich for cells with CSC characteristics such as in vitro differential proliferation rate, chemotherapeutic-resistance, tumorsphere formation, and in vivo tumorigenicity. We also compared their in vivo secondary tumor formation, and histological characteristics of their xenograft tumors, and examined their expression of PD-L1, EGFR, xCT, and reactive oxygen species (ROS).

Results: Both CD44v^high/ALDH^high and CD44v^high/ALDH^low cells were enriched in cells with CSC characteristics, with the CD44v^high/ALDH^low cells being more proliferative and more resistant to chemotherapeutics, whereas CD44v^high/ALDH^high cells were more efficient in forming tumorspheres in vitro, in making primary xenograft tumors, and in propagating secondary tumors in vivo. Applying stricter sorting gates to select for cells with the highest CD44v/ALDH expression caused the CD44v^high/ALDH^low cells to lose their high proliferation rates and chemotherapeutic resistance ability, but enriched for the tumorsphere-forming cells among the CD44v^high/ALDH^high and CD44v^high/ALDH^low cells. CD44v^high expression was associated with PD-L1 and xCT expression in both H1650 and HCC827 cells. This association was not modified by ALDH expression in the H1650 cell line. However, in the HCC827 cell line, ALDH expression was negatively associated with PD-L1 and positively associated with xCT expression.

Conclusion: Lung adenocarcinoma cells with high CD44v expression are enriched for CSCs. Addition of ALDH as an enrichment marker bestowed some CSCs characteristics to CD44v^high/ALDH^low cells and others to CD44v^high/ALDH^high cells. We propose that lung adenocarcinoma contains different CSCs, each of them endowed with different CSC characteristics.

MUC1-C is a target in lenalidomide resistant multiple myeloma

Lenalidomide (LEN) acts directly on multiple myeloma (MM) cells by inducing cereblon-mediated degradation of interferon regulatory factor 4, Ikaros (IKZF)1 and IKZF3, transcription factors that are essential for MM cell survival. The mucin 1 (MUC1) C-terminal transmembrane subunit (MUC1-C) oncoprotein is aberrantly expressed by MM cells and protects against reactive oxygen species (ROS)-mediated MM cell death. The present studies demonstrate that targeting MUC1-C with GO-203, a cell-penetrating peptide inhibitor of MUC1-C homodimerization, is more than additive with LEN in downregulating the WNT/β-catenin pathway, suppressing MYC, and inducing late apoptosis/necrosis. We show that the GO-203/LEN combination acts by synergistically increasing ROS and, in turn, suppressing β-catenin. LEN resistance has been linked to activation of the WNT/β-catenin→CD44 pathway. In this regard, our results further demonstrate that targeting MUC1-C is effective against LEN-resistant MM cells. Moreover, GO-203 resensitized LEN-resistant MM cells to LEN treatment in association with suppression of β-catenin and CD44. Targeting MUC1-C also resulted in downregulation of CD44 on the surface of primary MM cells. These findings, and the demonstration that expression of MUC1 and CD44 significantly correlate in microarrays from primary MM cells, provide support for combining GO-203 with LEN in the treatment of MM and in LEN-resistance.

Molecular and Microenvironmental Determinants of Glioma Stem-Like Cell Survival and Invasion

Glioblastoma multiforme (GBM) is the most frequent primary brain tumor in adults with a 5-year survival rate of 5% despite intensive research efforts. The poor prognosis is due, in part, to aggressive invasion into the surrounding brain parenchyma. Invasion is a complex process mediated by cell-intrinsic pathways, extrinsic microenvironmental cues, and biophysical cues from the peritumoral stromal matrix. Recent data have attributed GBM invasion to the glioma stem-like cell (GSC) subpopulation. GSCs are slowly dividing, highly invasive, therapy resistant, and are considered to give rise to tumor recurrence. GSCs are localized in a heterogeneous cellular niche, and cross talk between stromal cells and GSCs cultivates a fertile environment that promotes GSC invasion. Pro-migratory soluble factors from endothelial cells, astrocytes, macrophages, microglia, and non-stem-like tumor cells can stimulate peritumoral invasion of GSCs. Therefore, therapeutic efforts designed to target the invasive GSCs may enhance patient survival. In this review, we summarize the current understanding of extrinsic pathways and major stromal and immune players facilitating GSC maintenance and survival.

p38MAPK builds a hyaluronan cancer niche to drive lung tumorigenesis

Brichkina et al. show that lung cancer growth depends on short-distance cues produced by the cancer niche and identify fibroblast-specific hyaluronan synthesis at the center of p38-driven tumorigenesis. This in turn regulates early stromal fibroblast activation, the conversion to carcinoma-associated fibroblasts (CAFs), and cancer cell proliferation.

Expansion of neoplastic lesions generates the initial signal that instigates the creation of a tumor niche. Nontransformed cell types within the microenvironment continuously coevolve with tumor cells to promote tumorigenesis. Here, we identify p38MAPK as a key component of human lung cancer, and specifically stromal interactomes, which provides an early, protumorigenic signal in the tissue microenvironment. We found that lung cancer growth depends on short-distance cues produced by the cancer niche in a p38-dependent manner. We identified fibroblast-specific hyaluronan synthesis at the center of p38-driven tumorigenesis, which regulates early stromal fibroblast activation, the conversion to carcinoma-associated fibroblasts (CAFs), and cancer cell proliferation. Systemic down-regulation of p38MAPK signaling in a knock-in model with substitution of activating Tyr182 to phenylalanine or conditional ablation of p38 in fibroblasts has a significant tumor-suppressive effect on K-ras lung tumorigenesis. Furthermore, both Kras-driven mouse lung tumors and orthotopically grown primary human lung cancers show a significant sensitivity to both a chemical p38 inhibitor and an over-the-counter inhibitor of hyaluronan synthesis. We propose that p38MAPK–hyaluronan-dependent reprogramming of the tumor microenvironment plays a critical role in driving lung tumorigenesis, while blocking this process could have far-reaching therapeutic implications.

SP and KLF Transcription Factors in Digestive Physiology and Diseases

Specificity proteins (SPs) and Krüppel-like factors (KLFs) belong to the family of transcription factors that contain conserved zinc finger domains involved in binding to target DNA sequences. Many of these proteins are expressed in different tissues and have distinct tissue-specific activities and functions. Studies have shown that SPs and KLFs regulate not only physiological processes such as growth, development, differentiation, proliferation, and embryogenesis, but pathogenesis of many diseases, including cancer and inflammatory disorders. Consistently, these proteins have been shown to regulate normal functions and pathobiology in the digestive system. We review recent findings on the tissue- and organ-specific functions of SPs and KLFs in the digestive system including the oral cavity, esophagus, stomach, small and large intestines, pancreas, and liver. We provide a list of agents under development to target these proteins.

Natural and synthetic progestins enrich cancer stem cell-like cells in hormone-responsive human breast cancer cell populations in vitro

Clinical trials and studies have shown that combination estrogen/progestin hormone replacement therapy, but not estrogen therapy alone or placebo, increases breast cancer risk in postmenopausal women. Using animal models, we have previously shown that both natural and synthetic progestins (including medroxyprogesterone acetate [MPA], a synthetic progestin used widely in the clinical setting) accelerate the development of breast tumors in vivo and increase their metastasis to lymph nodes. Based on these observations, we have hypothesized that progestin-induced breast cancer tumor growth and metastasis may be mediated by an enrichment of the cancer stem cell (CSC) pool. In this study, we used T47-D and BT-474 hormone-responsive human breast cancer cells to examine the effects of progestin on phenotypic and functional markers of CSCs in vitro. Both natural and synthetic progestins (10 nM) significantly increased protein expression of CD44, an important CSC marker in tumor cells. MPA increased the levels of both CD44 variants v3 and v6 associated with stem cell functions. This induction of CD44 was blocked by the antiprogestin RU-486, suggesting that this process is progesterone receptor (PR) dependent. CD44 induction was chiefly progestin dependent. Because RU-486 can bind other steroid receptors, we treated PR-negative T47-D_CO-Y cells with MPA and found that MPA failed to induce CD44 protein expression, confirming that PR is essential for progestin-mediated CD44 induction in T47-D cells. Further, MPA treatment of T47-D cells significantly increased the activity of aldehyde dehydrogenase (ALDH), another CSC marker. Finally, two synthetic progestins, MPA and norethindrone, significantly increased the ability of T47-D cells to form mammospheres, suggesting that enrichment of the CD44^high, ALDH^bright subpopulation of cancer cells induced by MPA exposure is of functional significance. Based on our observations, we contend that exposure of breast cancer cells to synthetic progestins leads to an enrichment of the CSC pool, supporting the development of progestin-accelerated tumors in vivo.

Biophysical Regulation of Cancer Stem/Initiating Cells: Implications for Disease Mechanisms and Translation

Cancer stem/initiating cells (CSCs) are a subset of tumor cells proposed to play privileged roles in seeding tumors and driving metastasis. CSCs have emerged as an increasingly important target of interest in cancer biology and therapy. Recent work has suggested that CSC maintenance and metastatic potential may be modulated by physical inputs within the tissue microenvironment, including interstitial pressure and extracellular matrix stiffness. Here we review recent progress in our understanding of CSC regulation by biophysical signals within the tumor microenvironment. While the mechanistic basis of this signaling remains incompletely understood, we discuss emerging evidence that mechanical inputs can epigenetically regulate CSC behavior and that some CSCs can evade mechanotransductive signals to more efficiently infiltrate tissue. We also describe efforts to leverage these findings to engineer culture platforms for the characterization of CSC mechanics for discovery and screening.

MiR-520b as a novel molecular target for suppressing stemness phenotype of head-neck cancer by inhibiting CD44

Cancer stem cells preferentially acquire the specific characteristics of stress tolerance and high mobility, allowing them to progress to a therapy-refractive state. To identify a critical molecule to regulate cancer stemness is indispensable to erratically cure cancer. In this study, we identified miR-520b as a novel molecular target to suppress head-neck cancer (HNC) with stemness phenotype. MiR-520b inhibited cellular migration and invasion via the mechanism of epithelial-mesenchymal transition. It also sensitized cells to therapeutic drug and irradiation. Significantly, miR-520b suppressed spheroid cell formation, as well as reduced expressions of multiple stemness regulators (Nestin, Twist, Nanog, Oct4). The CD44 molecule was identified as a direct target of miR-520b, as shown by the reverse correlative expressions, the response to miR-520 modulation, the luciferase reporter assay, and the functional rescue analyses. These cellular results were confirmed by a tumor xenograft mice study. Administration of miR-520b dramatically restrained tumorigenesis and liver colonization. Conversely, miR-520b silencing led to an acceleration of tumor growth. Taken together, our study demonstrated that miR-520b inhibits the malignancy of HNC through regulation of cancer stemness conversion by targeting CD44. MiR-520b may serve as an emerging therapeutic target that may be further developed for the intervention of refractory HNC.

Chemotherapeutics-induced Oct4 expression contributes to drug resistance and tumor recurrence in bladder cancer

Cancer cells initially characterized as sensitive to chemotherapy may acquire resistance to chemotherapy and lead to tumor recurrence through the expansion of drug-resistant population. Acquisition of drug resistance to conventional chemotherapy is a major obstacle in the treatment of recurrent cancer. Here we investigated whether anticancer drugs induced Oct4 expression, thereby contributing to acquired drug resistance and tumor recurrence in bladder cancer. We identified a positive correlation of Oct4 expression with tumor recurrence in 122 clinical specimens of superficial high-grade (stages T1-2) bladder transitional cell carcinoma (TCC). Increased Oct4 levels in bladder tumors were associated with short recurrence-free intervals in the patients. Chemotherapy induced Oct4 expression in bladder cancer cells. Notably, treatment with cisplatin increased CD44-positive bladder cancer cells expressing Oct4, representing cancer stem-like cell subpopulation. Forced expression of Oct4 reduced, whereas knockdown of Oct4 enhanced, drug sensitivity in bladder cancer cells. Furthermore, tumor cells overexpressing Oct4 responded poorly to cisplatin in vivo. In regard to clinical relevance, inhibition of Oct4 by all-trans retinoic acid (ATRA) synergistically increased sensitivity to cisplatin in bladder cancer cells. Furthermore, the combination of cisplatin and ATRA was superior to cisplatin alone in suppressing tumor growth. Therefore, our results provide evidence that Oct4 increases drug resistance and implicate that inhibition of Oct4 may be a therapeutic strategy to circumvent drug resistance.

A novel nanomissile targeting two biomarkers and accurately bombing CTCs with doxorubicin

Rare circulating tumor cells (CTCs) cause >50% of primary colorectal cancer survivors to develop deadly metastasis at 3-5 years after surgery; the current chemotherapies can do nothing about these cells. Herein, we synthesized a novel doxorubicin (DOX)-entrapped mesoporous silica nanoparticle (MSN), covalently-conjugated with two aptamers, for simultaneously targeting EpCAM and CD44, the typical surface biomarkers of colorectal CTCs. The nanomissile can specifically capture the metastasis-prone CTCs spiked in healthy human blood in a competitive-binding manner. The binding not only accurately delivers DOX into the cancer cells via the biomarker-mediated endocytosis to inhibit CTC viability through the DOX-dependent mechanism, but also inhibits the adhesion of cancer cells to the endothelium and the consequent transmembrane migration through the DOX-independent mechanism. The molecular entity of the conjugate and its pharmaceutical DOX encapsulation-releasing capacity are well-demonstrated via various physiochemical characterizations including gel electrophoresis, which proves the >8-hour biostability of the nanomissile in blood, long enough for it to chase CTCs in mice and synergistically inhibit the CTC-induced lung metastasis more potently than its single aptamer-conjugated counterparts and DOX itself. The present strategy may pave a new avenue for safe and effective cancer metastasis chemoprevention.

NANOG overexpression and its correlation with stem cell and differentiation markers in meningiomas of different WHO grades

NANOG, as a key regulator of pluripotency and acting synergistically with other factors, has been described as a crucial transcription factor in various types of cancer. In meningiomas the expression of this marker has not yet been described. With our study, we aimed to identify and localize NANOG and other possible markers of pluripotency, stem cell properties and differentiation in meningioma tissue, to elucidate a possible effect on tumorigenesis. The gene expression levels of NANOG (NANOG1 and NANOGP8), SOX2, OCT4, KLF4, ABCG2, CMYC, MSI1, CD44, NOTCH1, NES, SALL4B, TP53, and EPAS1 were quantitatively examined using RT-qPCR in 33 surgical specimens of low- (WHO grade I) as well as in high-grade (WHO grade II/III) meningiomas with dural tissue as reference. Immunofluorescence co-localization analysis following confocal fluorescence microscopy for NANOG, OCT4, SOX2, Nestin, KI-67, and CD44 was also performed. There was a significant overexpression of NANOG, MSI1, and EPAS1 and a downregulation of NES in all examined tumors. Subgroup analysis (WHO grade I versus grade II/III) revealed differences in the expression of NANOG, CD44, and MSI1. We found 1% NANOG-positive (NANOG+) cells in low-grade and 2% in grade II/III meningiomas co-expressing the other mentioned markers in various compositions. In particular, NANOG+ cells expressing SOX2 and OCT4 were successfully identified (26% low-grade versus 20% high-grade). Our data reveal an overexpression of NANOG and other markers of pluripotency and stemness in meningiomas. Such potentially pluripotent "stem cell-like" cells may have an impact on tumorigenesis and progression in human meningiomas.

CD44 and its ligand hyaluronan as potential biomarkers in malignant pleural mesothelioma: evidence and perspectives

Malignant pleural mesothelioma (MPM) is a rare and highly drug resistant tumor arising from the mesothelial surfaces of the lung pleura. The standard method to confirm MPM is the tedious, time-consuming cytological examination of cancer biopsy. Biomarkers that are detectable in pleural effusion or patient serum are reasonable options to provide a faster and noninvasive diagnostic approach. As yet, the current biomarkers for MPM lack specificity and sensitivity to discriminate this neoplasm from other lung tumors. CD44, a multifunctional surface receptor has been implicated in tumor progression in different cancers including MPM. The interaction of CD44 with its ligand, hyaluronan (HA) has demonstrated an important role in modulating cell proliferation and invasiveness in MPM. In particular, the high expression levels of these molecules have shown diagnostic relevance in MPM. This review will summarize the biology and diagnostic implication of CD44 and HA as well as the interaction of both molecules in MPM that will demonstrate their potential as biomarkers. Augmentation of the current markers in MPM may lead to an earlier diagnosis and management of this disease.

Expression of Krüppel-like factor 4 in breast cancer tissues and its effects on the proliferation of breast cancer MDA-MB-231 cells

The aim of the present study was to detect the expression of Krüppel-like factor 4 (KLF4) in breast cancer tissues and to evaluate the effect on the proliferation of breast cancer MDA-MB-231 cells. The expression of KLF4 protein in 239 breast cancer tissues and 40 paracancerous tissues were detected by an immunohistochemical assay, and its correlation with clinical pathological parameters was analyzed. A eukaryotic expression vector, pcDNA3.1-KLF4, was constructed by transient transfection of breast cancer MDA-MB-231 cells with liposomes (experimental group). The untransfected cells and those transfected with empty plasmid pcDNA3.1 were used as the blank and negative control groups, respectively. The expression of the KLF4 gene and protein in the three groups were detected by reverse transcription polymerase chain reaction and western blotting, respectively. Furthermore, the cell proliferative capacity was detected by an MTT assay. The positive expression rate of KLF4 protein in breast cancer tissues (39.0%, 93/239) was significantly lower than that of paracancerous tissues (77.5%, 31/40) (P<0.05). In addition, KLF4 protein expression in breast cancer tissues was correlated with pathological type, histological grade and lymphatic metastasis (P<0.05). KLF4 mRNA and protein were both expressed by the experimental group, but not by the two control groups. Meanwhile, the proliferative capacity of the experimental group was also significantly decreased. A significant decrease in the positive expression rate of KLF4 protein in breast cancer tissues was correlated with several clinical pathological parameters. In addition, transfection of the KLF4 gene inhibited the proliferation of breast cancer cells, suggesting that this gene is important in the onset and progression of this type of cancer.

Multinucleated polyploidy drives resistance to Docetaxel chemotherapy in prostate cancer

BACKGROUND

Docetaxel is the only FDA-approved first-line treatment for castration-resistant prostate cancer (CRPC) patients. Docetaxel treatment inevitably leads to tumour recurrence after an initial therapeutic response with generation of multinucleated polyploid (MP) cells. Here we investigated role of MP cells in clinical relapse of CRPC.

METHODS

Prostate cancer (PC-3) cells were treated with docetaxel (5 nM) for 3 days followed by a washout and samples were collected at close intervals over 35 days post drug washout. The tumorigenic potential of the giant MP cells was studied by implanting MP cells subcutaneously as tumour xenografts in nude mice.

RESULTS

Docetaxel-induced polyploid cells undergo mitotic slippage and eventually spawn mononucleated cells via asymmetric cell division or neosis. Both MP and cells derived from polyploid cells had increased survival signals, were positive for CD44 and were resistant to docetaxel chemotherapy. Although MP cells were tumorigenic in nude mice, these cells took a significantly longer time to form tumours compared with parent PC-3 cells.

CONCLUSIONS

Generation of MP cells upon docetaxel therapy is an adaptive response of apoptosis-reluctant cells. These giant cells ultimately contribute to the generation of mononucleated aneuploid cells via neosis and may have a fundamental role precipitating clinical relapse and chemoresistance in CRPC.

Hyaluronan coating improves liver engraftment of transplanted human biliary tree stem/progenitor cells

BACKGROUND

Cell therapy of liver diseases with human biliary tree stem cells (hBTSCs) is biased by low engraftment efficiency. Coating the hBTSCs with hyaluronans (HAs), the primary constituents of all stem cell niches, could facilitate cell survival, proliferation, and, specifically, liver engraftment given that HAs are cleared selectively by the liver.

METHODS

We developed a fast and easy method to coat hBTSCs with HA and assessed the effects of HA-coating on cell properties in vitro and in vivo.

RESULTS

The HA coating markedly improved the viability, colony formation, and population doubling of hBTSCs in primary cultures, and resulted in a higher expression of integrins that mediate cell attachment to matrix components. When HA-coated hBTSCs were transplanted via the spleen into the liver of immunocompromised mice, the engraftment efficiency increased to 11% with respect to 3% of uncoated cells. Notably, HA-coated hBTSC transplantation in mice resulted in a 10-fold increase of human albumin gene expression in the liver and in a 2-fold increase of human albumin serum levels with respect to uncoated cells. Studies in distant organs showed minimal ectopic cell distribution without differences between HA-coated and uncoated hBTSCs and, specifically, cell seeding in the kidney was excluded.

CONCLUSIONS

A ready and economical procedure of HA cell coating greatly enhanced the liver engraftment of transplanted hBTSCs and improved their differentiation toward mature hepatocytes. HA coating could improve outcomes of stem cell therapies of liver diseases and could be immediately translated into the clinic given that GMP-grade HAs are already available for clinical use.

Prognostic Significance of CD44 and Orthopedia Homeobox Protein (OTP) Expression in Pulmonary Carcinoid Tumours

CD44 and orthopedia homeobox protein (OTP) expressions have shown to be predictive of overall survival in pulmonary carcinoid (PC) tumours. The scope of the present study was to validate their role in PC patients and investigate potential application in clinical practice. Data was collected from patients presenting to a tertiary cancer centre diagnosed with PC between 2003 and 2015. Diagnosis was confirmed by central pathology review. Formalin-fixed paraffin-embedded (FFPE) tissue samples collected at diagnosis were scored using immunohistochemistry (H score) for standard CD44 and nuclear and cytoplasmic OTP protein expression. The study included 108 patients. High CD44/nuclear OTP (nOTP) expression was strongly associated with typical carcinoid (TC) histology (p < 0.001). Eighty-six patients, who underwent radical surgical resection, were selected to assess the impact of patient and tumour parameters on relapse-free survival (RFS). Sixty-nine (80 %) had TC and 17 (20 %) had atypical carcinoid tumours. On multivariate analysis, high CD44 and nOTP expression, TC histology and non-infiltrative tumour growth were associated with superior RFS. Early stage TC (stage pT1aN0) patients (N = 32; 46 %) had excellent prognosis irrespective of CD44/nOTP status. Importantly, TC patients with locally advanced disease (defined as >pT1aN0) and high CD44/nOTP expression (N = 26; 38 %) had excellent RFS (p = 0.005) compared to those with the same stage but low CD44 and/or nOTP (N = 11; 16 %). Additionally, the combination of CD44/nOTP expression and tumour growth pattern led to a more accurate prognostic system compared to the established WHO classification of PC tumours (concordance index = 0.902 vs 0.811, respectively, p < 0.001). Assessment of CD44/nOTP expression combined with tumour growth pattern identifies clear groups with largely different prognosis. These findings provide important information on how patients with these resected cancers should be followed up.

Adult human retinal Müller glia display distinct peripheral and macular expression of CD117 and CD44 stem cell-associated proteins

Experimental evidence suggests human Müller glia exhibit neural progenitor properties in vitro. CD117 and CD44 are known to be expressed by stem cells, the survival of which appears to depend critically on interactions with hyaluronan-rich extracellular matrix (ECM). Here, we characterise Müller glia expression of CD117 and CD44 in normal adult human retina and describe how it correlates with hyaluronan distribution in ocular ECM. By using chromogen-based immunohistochemistry, CD117 expression was found in entire Müller glia cytoplasm spanning from inner to outer limiting membrane in both peripheral retina (PR) and macular retina (MR), mirroring expression of the established Müller glia marker vimentin. Unlike vimentin, CD117 was also strongly expressed by Müller glia nuclei. Relative to total inner nuclear layer (INL) nuclei, more CD117+ Müller glia nuclei were seen in PR than MR. By contrast, CD44 expression was found predominantly in Müller glia apical processes of PR; no expression was found in MR. Astral blue staining demonstrated the presence of hyaluronan in cortical vitreous and the interphotoreceptor matrix (IPM) in both MR and PR. Our findings demonstrate that: (i) both CD117 and CD44 are expressed by human adult Müller glia; (ii) CD117 is a robust nuclear and cytoplasmic immunohistochemical marker of Müller glia; and (iii) that while CD117 is expressed by the entire Müller glia in both PR and MR, CD44 is only expressed by Müller glia apices in PR. Since the apices of Müller glia are in direct contact with the hyaluronan-rich IPM, the Müller glia-IPM interface in PR is likely a favourable region for supporting progenitor or stem cell-like signalling. These observations provide novel insights into potential stem-cell favouring microenvironments in mature human retina.

Krüppel-like factor 4 (KLF4): What we currently know

Krüppel-like factor 4 (KLF4) is an evolutionarily conserved zinc finger-containing transcription factor that regulates diverse cellular processes such as cell growth, proliferation, and differentiation. Since its discovery in 1996, KLF4 has been gaining a lot of attention, particularly after it was shown in 2006 as one of four factors involved in the induction of pluripotent stem cells (iPSCs). Here we review the current knowledge about the different functions and roles of KLF4 in various tissue and organ systems.

KLF4 is regulated by RAS/RAF/MEK/ERK signaling through E2F1 and promotes melanoma cell growth

Melanoma is the most lethal form of skin cancer and treatment of metastatic melanoma remains challenging. BRAF/MEK inhibitors show only temporary benefit due the occurrence of resistance and immunotherapy is effective only in a subset of patients. To improve patient survival, there is a need to better understand molecular mechanisms that drive melanoma growth and operate downstream of the mitogen activated protein kinase (MAPK) signaling. The Krüppel-like factor 4 (KLF4) is a zinc-finger transcription factor that plays a critical role in embryonic development, stemness and cancer, where it can act either as oncogene or tumor suppressor. KLF4 is highly expressed in post-mitotic epidermal cells, but its role in melanoma remains unknown. Here, we address the function of KLF4 in melanoma and its interaction with the MAPK signaling pathway. We find that KLF4 is highly expressed in a subset of human melanomas. Ectopic expression of KLF4 enhances melanoma cell growth by decreasing apoptosis. Conversely, knock-down of KLF4 reduces melanoma cell proliferation and induces cell death. In addition, depletion of KLF4 reduces melanoma xenograft growth in vivo. We find that the RAS/RAF/MEK/ERK signaling positively modulates KLF4 expression through the transcription factor E2F1, which directly binds to KLF4 promoter. Overall, our data demonstrate the pro-tumorigenic role of KLF4 in melanoma and uncover a novel ERK1/2-E2F1-KLF4 axis. These findings identify KLF4 as a possible new molecular target for designing novel therapeutic treatments to control melanoma growth.

Aging and the Krüppel-like factors

The mammalian Krüppel-like factors (KLFs) are a family of zinc-finger containing transcription factors with diverse patterns of expression and a wide array of cellular functions. While their roles in mammalian physiology are well known, there is a growing appreciation for their roles in modulating the fundamental progression of aging. Here we review the current knowledge of Krüppel-like factors with a focus on their roles in processes regulating aging and age-associated diseases.

Associations of five polymorphisms in the CD44 gene with cancer susceptibility in Asians

CD44 polymorphisms have been previously associated with cancer risk. However, the results between independent studies were inconsistent. Here, a meta-analysis was performed to systematically evaluate associations between CD44 polymorphisms and cancer susceptibility. A comprehensive literature search conducted in PubMed, Embase, and Web of Science databases through August 10, 2016 yielded 11 eligible publications consisting of 5,788 cancer patients and 5,852 controls. Overall, odds ratios (OR) calculated with 95% confidence intervals (CI) identified a significant association between CD44 polymorphism rs13347 and cancer susceptibility under all genetic models. Additionally, the minor allele of polymorphism rs11821102 was associated with a decreased susceptibility to cancer in allele contrast, dominant, and heterozygous models, while no significant association was identified for polymorphisms rs10836347, rs713330, or rs1425802. Subgroup analysis by ethnicity revealed rs13347 was significantly associated with cancer susceptibility for Chinese but not for Indians. Linkage disequilibrium (LD) between different polymorphisms varied across diverse ethnic populations. In conclusion, the results indicate that CD44 polymorphism rs13347 acts as a risk factor for cancer, especially in Chinese, while the minor allele of polymorphism rs11821102 may be associated with a decreased susceptibility to cancer. Nevertheless, further studies on a larger population covering different ethnicities are warranted.

A novel double-targeted nondrug delivery system for targeting cancer stem cells

Instead of killing cancer stem cells (CSCs), the conventional chemotherapy used for cancer treatment promotes the enrichment of CSCs, which are responsible for tumor growth, metastasis, and recurrence. However, most therapeutic agents are only able to kill a small proportion of CSCs by targeting one or two cell surface markers or dysregulated CSC pathways, which are usually shared with normal stem cells (NSCs). In this study, we developed a novel nondrug delivery system for the dual targeting of CSCs by conjugating hyaluronic acid (HA) and grafting the doublecortin-like kinase 1 (DCLK1) monoclonal antibody to the surface of poly(ethylene glycol) (PEG)–poly(d,l-lactide-co-glycolide) (PLGA) nanoparticles (NPs), which can specifically target CD44 receptors and the DCLK1 surface marker – the latter was shown to possess the capacity to distinguish between CSCSs and NSCs. The size and morphology of these NPs were characterized by dynamic light scattering (DLS), transmission electron microscopy (TEM), and scanning electron microscopy (SEM). This was followed by studies of NP encapsulation efficiency and in vitro drug release properties. Then, the cytotoxicity of the NPs was tested via Cell Counting Kit-8 assay. Finally, the 4T1 CSCs were obtained from the alginate-based platform, which we developed as an in vitro tumor model. Tumor-bearing nude mice were used as in vivo models to systematically detect the ability of NPs to target CSCs. Our results showed that the DCLK1–HA–PEG–PLGA NPs exhibited a targeting effect toward CSCs both in vitro and in vivo. These findings have important implications for the rational design of drug delivery systems that target CSCs with high efficacy.

Effect of Kruppel-like factor 4 on Notch pathway in hepatic stellate cells

The relationship between Kruppel-like factor 4 (KLF4) and the Notch pathway was determined to investigate the effect of KLF4 on the activation of hepatic stellate cells and underlying mechanisms. Fifty SPF BALB/c mice were randomly divided into two groups. A liver fibrosis model was established in 25 mice as the experimental group, and the remaining 25 mice served as controls. On the day 0, 7, 14, and 35, liver tissues were removed for immunofluorescent detection. The Notch pathway inhibitor DAPT was added to the primary original hepatic stellate cells, and KLF4 and Notch-associated factor expression was detected by qRT-PCR. Additionally, the hepatic stellate cell line LX-2 was used to establish control and experimental groups, and was cultured in vitro. LX-2 cells in the experimental groups were treated with DAPT and the Notch activator transforming growth factor-beta 1 separately, whereas those in the control group were given isotonic culture medium. After 48 h, KLF4 expression was examined by Western blotting. After transient transfection of LX-2 cells to increase KLF4, the expression of Notch factor was examined. Immunofluorescence analysis showed that, with the aggravation of liver fibrosis, the absorbance (A) values of KLF4 were decreased (day 0: 980.73±153.19; day 7: 1087.99±230.23; day 14: 390.95±93.56; day 35: 245.99±87.34). The expression of Notch pathway- related factors (Notch-1, Notch-2, and Jagged-1) in the hepatic stellate cell membrane was negatively correlated to KLF4 expression. With the increase of KLF4 expression, Notch-2 (0.73±0.13) and Jagged-1 (0.43±0.12) expression decreased, whereas Notch-1 level was not detectable. When the Notch pathway was inhibited, KLF4 levels generally increased (18.12±1.31). Our results indicate that KLF4 expression is negatively correlated to the Notch pathway in hepatic stellate cells, which may provide a reference for the treatment of hepatic fibrosis.

ESE3 Inhibits Pancreatic Cancer Metastasis by Upregulating E-Cadherin

The ETS family transcription factor ESE3 is a crucial element in differentiation and development programs for many epithelial tissues. Here we report its role as a tumor suppressor in pancreatic cancer. We observed drastically lower ESE3 expression in pancreatic ductal adenocarcinomas (PDAC) compared with adjacent normal pancreatic tissue. Reduced expression of ESE3 in PDAC correlated closely with an increase in lymph node metastasis and vessel invasion and a decrease in relapse-free and overall survival in patients. In functional experiments, downregulating the expression of ESE3 promoted PDAC cell motility and invasiveness along with metastasis in an orthotopic mouse model. Mechanistic studies in PDAC cell lines, the orthotopic mouse model, and human PDAC specimens demonstrated that ESE3 inhibited PDAC metastasis by directly upregulating E-cadherin expression at the level of its transcription. Collectively, our results establish ESE3 as a negative regulator of PDAC progression and metastasis by enforcing E-cadherin upregulation. Cancer Res; 77(4); 874-85. ©2016 AACR.

Quantitative assessment of CD44 genetic variants and cancer susceptibility in Asians: a meta-analysis

CD44 is a well-established cancer stem cell marker playing a crucial role in tumor metastasis, recurrence and chemo-resistance. Genetic variants of CD44 have been shown to be associated with susceptibility to various cancers; however, the results are confounding. Hence, we performed a meta-analysis to clarify these associations more accurately. Overall, rs13347 (T vs. C: OR=1.30, p=<0.004, pcorr=0.032; CT vs. CC: OR=1.29, p=0.015, pcorr=0.047; TT vs. CC: OR=1.77, p=<0.000, pcorr=0.018; CT+TT vs. CC: OR=1.34, p=<0.009, pcorr=0.041) and rs187115 (GG vs. AA: OR=2.34, p=<0.000, pcorr=0.025; AG vs. AA: OR=1.59, p=<0.000, pcorr=0.038; G vs. A allele OR=1.56, p=0.000, pcorr=0.05; AG+GG vs. AA: OR=1.63, p=<0.000, pcorr=0.013) polymorphisms were found to significantly increase the cancer risk in Asians. On the other hand, rs11821102 was found to confer low risk (A vs. G: OR=0.87, p=<0.027, pcorr=0.04; AG vs. GG: OR=0.85, p=<0.017, pcorr=0.01; AG+AA vs. GG: OR=0.86, p=<0.020, pcorr=0.02). Based on our analysis, we suggest significant role of CD44 variants (rs13347, rs187115 and rs11821102) in modulating individual's cancer susceptibility in Asians. Therefore, these variants may be used as predictive genetic biomarkers for cancer predisposition in Asian populations. However, more comprehensive studies involving other cancers and/or populations, haplotypes, gene-gene and gene-environment interactions are necessary to delineate the role of these variants in conferring cancer risk.

Cancer Stem Cells Therapeutic Target Database: The First Comprehensive Database for Therapeutic Targets of Cancer Stem Cells

Cancer stem cells (CSCs) are a subpopulation of tumor cells that have strong self-renewal capabilities and may contribute to the failure of conventional cancer therapies. Hence, therapeutics homing in on CSCs represent a novel and promising approach that may eradicate malignant tumors. However, the lack of information on validated targets of CSCs has greatly hindered the development of CSC-directed therapeutics. Herein, we describe the Cancer Stem Cells Therapeutic Target Database (CSCTT), the first online database to provide a rich bioinformatics resource for the display, search, and analysis of structure, function, and related annotation for therapeutic targets of cancer stem cells. CSCTT contains 135 proteins that are potential targets of CSCs, with validated experimental evidence manually curated from existing literatures. Proteins are carefully annotated with a detailed description of protein families, biological process, related diseases, and experimental evidences. In addition, CSCTT has compiled 213 documented therapeutic methods for cancer stem cells, including 118 small molecules and 20 biotherapy methods. The CSCTT may serve as a useful platform for the development of CSC-directed therapeutics against various malignant tumors. The CSCTT database is freely available to the public at http://www.csctt.org/. Stem Cells Translational Medicine 2017;6:331-334.

Burrowing through the Heterogeneity: Review of Mouse Models of PTCL-NOS

Currently, there are 19 different peripheral T-cell lymphoma (PTCL) entities recognized by the World Health Organization; however, ~70% of PTCL diagnoses fall within one of three subtypes [i.e., peripheral T-cell lymphoma not otherwise specified (PTCL-NOS), anaplastic large-cell lymphoma, and angioimmunoblastic T-cell lymphoma]. PTCL-NOS is a grouping of extra-thymic neoplasms that represent a challenging and heterogeneous subset of non-Hodgkin’s lymphomas. Research into peripheral T-cell lymphomas has been cumbersome as the lack of defining cytogenetic, histological, and molecular features has stymied diagnosis and treatment of these diseases. Similarly, the lacks of genetically manipulated murine models that faithfully recapitulate disease characteristics were absent prior to the turn of the century. Herein, we review the literature concerning existing mouse models for PTLC-NOS, while paying particular attention to the etiology of this heterogeneous disease.

The role of CD44 in glioblastoma multiforme

A transmembrane molecule with several isoforms, CD44 is overexpressed in many tumors and promotes tumor formation through interactions with the tumor microenvironment. CD44 has been implicated in malignant processes including cell motility, tumor growth, and angiogenesis. The role of CD44 has been examined in many cancer types. This paper provides, to our knowledge, the first focused review of the role of CD44 in glioblastoma multiforme (GBM), the most common and fatal of primary brain cancers. We summarize research that describes how CD44 promotes GBM aggressiveness by increasing tumor cell invasion, proliferation and resistance to standard chemoradiation therapy. Effects of CD44 inhibition in GBM are also explored. Clinical trials investigating CD44 targeting in CD44-positive solid tumors are underway, and the evidence presented here suggests that CD44 inhibition in GBM may be a promising therapy.

Krüppel-like factor 4 is a novel prognostic predictor for urothelial carcinoma of bladder and it regulates TWIST1-mediated epithelial-mesenchymal transition

BACKGROUND

Krüppel-like factor 4 (KLF4) exerts tumor suppressive or oncogenic functions in a cell-type-dependent manner, but its prognostic role in urothelial carcinoma of bladder (UCB) remains unclear. We aimed to determine how KLF4 regulates epithelial-mesenchymal transition (EMT) and predicts patient survival in UCB.

PATIENTS AND METHODS

The roles of KLF4 and other EMT regulators in cancer progression were studied in UCB specimens of 398 patients, UCB cell lines. The results were validated by open-access The Cancer Genome Atlas dataset.

RESULTS

Over a median follow-up of 46.5 months, tissue microarray demonstrated that strong KLF4 expression was associated with higher risk toward metastasis and death (P<0.001). KLF4 expression positively correlated with TWIST1 and vimentin, and inversely correlated with E-cadherin expression. Metastasis-free survival was poorest in KLF4/TWIST1 coexpression group, followed by KLF4 or TWIST1 expression-alone group, and no-expression group (P<0.001). Multivariate analysis substantiated that KLF4/TWIST1 coexpression independently predicted overall mortality and metastasis risk with hazard ratios of 2.43 (95% CI: 1.65-3.64) and 7.54 (CI: 4.03-12.10). The Cancer Genome Atlas dataset of bladder cancer also revealed a trend toward decreased overall survival in the high KLF4 expression group as compared to the low KLF4 group. In vitro, KLF4 is accompanied with decreased E-cadherin and β-catenin expressions, increased vimentin and fibronectin expressions, and enhanced migration/invasion. KLF4 knockdown suppressed TWIST1 expression and inhibited EMT, migration and invasion, whereas enforced KLF4 overexpression activated TWIST1 expression and restored EMT and metastatic phenotype. Furthermore, TWIST1 knockdown abolished KLF4-faciliated EMT and metastatic feature without affecting KLF4 expression.

CONCLUSIONS

KLF4 promotes TWIST1-mediated EMT and may represent a novel prognostic predictor in UCB.

The Novel KLF4/MSI2 Signaling Pathway Regulates Growth and Metastasis of Pancreatic Cancer

PURPOSE

Musashi 2 (MSI2) is reported to be a potential oncoprotein in cases of leukemia and several solid tumors. However, its expression, function, and regulation in pancreatic ductal adenocarcinoma (PDAC) cases have yet to be demonstrated. Therefore, in the current study, we investigated the clinical significance and biologic effects of MSI2 expression in PDAC cases and sought to delineate the clinical significance of the newly identified Krüppel-like factor 4 (KLF4)/MSI2 regulatory pathway.

EXPERIMENTAL DESIGN

MSI2 expression and its association with multiple clinicopathologic characteristics in human PDAC specimens were analyzed immunohistochemically. The biological functions of MSI2 regarding PDAC cell growth, migration, invasion, and metastasis were studied using gain- and loss-of-function assays both in vitro and in vivo Regulation of MSI2 expression by KLF4 was examined in several cancer cell lines, and the underlying mechanisms were studied using molecular biologic methods.

RESULTS

MSI2 expression was markedly increased in both PDAC cell lines and human PDAC specimens, and high MSI2 expression was associated with poor prognosis for PDAC. Forced MSI2 expression promoted PDAC proliferation, migration, and invasion in vitro and growth and metastasis in vivo, whereas knockdown of MSI2 expression did the opposite. Transcriptional inhibition of MSI2 expression by KLF4 occurred in multiple PDAC cell lines as well as mouse models of PDAC.

CONCLUSIONS

Lost expression of KLF4, a transcriptional repressor of MSI2 results in overexpression of MSI2 in PDACs, which may be a biomarker for accurate prognosis. A dysregulated KLF4/MSI2 signaling pathway promotes PDAC progression and metastasis. Clin Cancer Res; 23(3); 687-96. ©2016 AACR.

Post-Transcriptional Regulation of KLF4 by High-Risk Human Papillomaviruses Is Necessary for the Differentiation-Dependent Viral Life Cycle

Human papillomaviruses (HPVs) are epithelial tropic viruses that link their productive life cycles to the differentiation of infected host keratinocytes. A subset of the over 200 HPV types, referred to as high-risk, are the causative agents of most anogenital malignancies. HPVs infect cells in the basal layer, but restrict viral genome amplification, late gene expression, and capsid assembly to highly differentiated cells that are active in the cell cycle. In this study, we demonstrate that HPV proteins regulate the expression and activities of a critical cellular transcription factor, KLF4, through post-transcriptional and post-translational mechanisms. Our studies show that KLF4 regulates differentiation as well as cell cycle progression, and binds to sequences in the upstream regulatory region (URR) to regulate viral transcription in cooperation with Blimp1. KLF4 levels are increased in HPV-positive cells through a post-transcriptional mechanism involving E7-mediated suppression of cellular miR-145, as well as at the post-translational level by E6–directed inhibition of its sumoylation and phosphorylation. The alterations in KLF4 levels and functions results in activation and suppression of a subset of KLF4 target genes, including TCHHL1, VIM, ACTN1, and POT1, that is distinct from that seen in normal keratinocytes. Knockdown of KLF4 with shRNAs in cells that maintain HPV episomes blocked genome amplification and abolished late gene expression upon differentiation. While KLF4 is indispensable for the proliferation and differentiation of normal keratinocytes, it is necessary only for differentiation-associated functions of HPV-positive keratinocytes. Increases in KLF4 levels alone do not appear to be sufficient to explain the effects on proliferation and differentiation of HPV-positive cells indicating that additional modifications are important. KLF4 has also been shown to be a critical regulator of lytic Epstein Barr virus (EBV) replication underscoring the importance of this cellular transcription factor in the life cycles of multiple human cancer viruses.

Viruses that induce persistent infections often alter the expression and activities of cellular transcription factors to regulate their productive life cycles. Human papillomaviruses (HPVs) are epithelial tropic viruses that link their productive life cycles to the differentiation of infected host keratinocytes. Our studies show that KLF-4, originally characterized as a pluripotency factor, binds HPV-31 promoters activating viral transcription as well as modulates host cell differentiation and cell cycle progression. KLF4 levels and activity are enhanced in HPV-positive cells by E6 and E7 mediated post-transcriptional and post-translational mechanisms resulting in altered target gene expression and biological functions from that seen in normal keratinocytes. Importantly, silencing KLF4 hinders viral genome amplification and late gene expression. Along with its recently identified role in Epstein Barr Virus reactivation during differentiation, our studies demonstrate the importance of KLF4 in the life cycles of multiple human cancer viruses.

Wnt Signaling in Cancer Stem Cell Biology

Aberrant regulation of Wnt signaling is a common theme seen across many tumor types. Decades of research have unraveled the epigenetic and genetic alterations that result in elevated Wnt pathway activity. More recently, it has become apparent that Wnt signaling levels identify stem-like tumor cells that are responsible for fueling tumor growth. As therapeutic targeting of these tumor stem cells is an intense area of investigation, a concise understanding on how Wnt activity relates to cancer stem cell traits is needed. This review attempts at summarizing the intricacies between Wnt signaling and cancer stem cell biology with a special emphasis on colorectal cancer.

Auraptene Attenuates Malignant Properties of Esophageal Stem-Like Cancer Cells

The high incidence of esophageal squamous cell carcinoma has been reported in selected ethnic populations including North of Iran. Low survival rate of esophageal carcinoma is partially due to the presence of stem-like cancer cells with chemotherapy resistance. In the current study, we aimed to determine the effects of auraptene, an interesting dietary coumarin with various biological activities, on malignant properties of stem-like esophageal squamous cell carcinoma, in terms of sensitivity to anticancer drugs and expression of specific markers. To do so, the half maximal inhibitory concentration values of auraptene, cisplatin, paclitaxel, and 5-fluorouracil were determined on esophageal carcinoma cells (KYSE30 cell line). After administrating combinatorial treatments, including nontoxic concentrations of auraptene + cisplatin, paclitaxel, or 5-fluorouracil, sensitivity of cells to chemical drugs and also induced apoptosis were assessed. In addition, quantitative real-time polymerase chain reaction was used to study changes in the expression of tumor suppressor proteins 53 and 21 ( P53 and P21), cluster of differentiation 44 ( CD44), and B cell-specific Moloney murine leukemia virus integration site 1 ( BMI-1) upon treatments. Results of thiazolyl blue assay revealed that auraptene significantly ( P < .05) increased toxicity of cisplatin, paclitaxel, and 5-fluorouracil in KYSE30 cells, specifically 72 hours after treatment. Conducting an apoptosis assay using flow cytometry also confirmed the synergic effects of auraptene. Results of quantitative real-time polymerase chain reaction revealed significant ( P < .05) upregulation of P53 and P21 upon combinatorial treatments and also downregulation of CD44 and BMI-1 after auraptene administration. Current study provided evidence, for the first time, that auraptene attenuates the properties of esophageal stem-like cancer cells through enhancing sensitivity to chemical agents and reducing the expression of CD44 and BMI-1 markers.

Neurotrophin signaling in cancer stem cells

Cancer stem cells (CSCs), are thought to be at the origin of tumor development and resistance to therapies. Thus, a better understanding of the molecular mechanisms involved in the control of CSC stemness is essential to the design of more effective therapies for cancer patients. Cancer cell stemness and the subsequent expansion of CSCs are regulated by micro-environmental signals including neurotrophins. Over the years, the roles of neurotrophins in tumor development have been well established and regularly reviewed. Especially, nerve growth factor (NGF) and brain-derived neurotrophic factor (BDNF) are reported to stimulate tumor cell proliferation, survival, migration and/or invasion, and favors tumor angiogenesis. More recently, neurotrophins have been reported to regulate CSCs. This review briefly presents neurotrophins and their receptors, summarizes their roles in different cancers, and discusses the emerging evidence of neurotrophins-induced enrichment of CSCs as well as the involved signaling pathways.

Carcinoma Cell Hyaluronan as a "Portable" Cancerized Prometastatic Microenvironment

Hyaluronan (HA) is a structurally simple polysaccharide, but its ability to act as a template for organizing pericellular matrices and its regulated synthesis and degradation are key to initiating repair responses. Importantly, these HA functions are usurped by tumor cells to facilitate progression and metastasis. Recent advances have identified the functional complexities associated with the synthesis and degradation of HA-rich matrices. Three enzymes synthesize large HA polymers while multiple hyaluronidases or tissue free radicals degrade these into smaller bioactive fragments. A family of extracellular and cell-associated HA-binding proteins/receptors translates the bioinformation encrypted in this complex polymer mixture to activate signaling networks required for cell survival, proliferation, and migration in an actively remodeling microenvironment. Changes in HA metabolism within both the peritumor stroma and parenchyma are linked to tumor initiation, progression, and poor clinical outcome. We review evidence that metastatic tumor cells must acquire the capability to autonomously synthesize, assemble, and process their own "portable" HA-rich microenvironments to survive in the circulation, metastasize to ectopic sites, and escape therapeutic intervention. Strategies to disrupt the HA machinery of primary tumor and circulating tumor cells may enhance the effectiveness of current conventional and targeted therapies. Cancer Res; 76(9); 2507-12. ©2016 AACR.