Overview of cancer stem cells (CSCs) and mechanisms of their regulation: implications for cancer therapy

Human fallopian tube epithelial cells exhibit stemness features, self-renewal capacity, and Wnt-related organoid formation

BACKGROUND

Fallopian tube epithelial cells (FTEC) were thought to be the origin of high-grade serous ovarian carcinoma (HGSOC). Knowledge of the stemness or initiating characteristics of FTEC is insufficient. Previously, we have characterized the stemness cell marker of FTEC, this study aims to further characterize the clonogenicity and spheroid features of FTEC.

METHODS

We successfully derived FTECs from the epithelial layer of the human fallopian tubes. We examined the morphology, proliferation rate, doubling time, and clonal growth of them. At passage 3, the sphere formations on gelatin-coated culture, suspension culture, and matrigel culture were observed, and the expression of LGR5, SSEA3, SSEA4, and other stemness markers was examined. Furthermore, tissue-reconstituted organoids from coculture of FTEC, fallopian stromal cells (FTMSC) and endothelial cells (HUVEC) were examined.

RESULTS

FTEC exhibited cuboidal cell morphology and maintained at a constant proliferation rate for up to nine passages (P9). FTEC could proliferate from a single cell with a clonogenic efficiency of 4%. Flow cytometry revealed expressions of normal stem cell markers (SSEA3, SSEA4, and LGR5) and cancer stem cell markers (CD24, CD44, CD117, ROR1, and CD133). FTEC formed spheres and colonies when cultured on low attach dish. In the presence of Matrigel, the stemness and colony formation activity were much enhanced. In co-culturing with FTMSC and HUVEC, FTEC could form organoids that could be blocked by Wnt inhibitor DKK1. Expressions of LGR5 and FOXJ1 expression were also decreased by adding DKK1.

CONCLUSION

We demonstrated abundantly presence of stem cells in human FTECs which are efficient in forming colonies, spheres and organoids, relying on Wnt signaling. We also reported for the first time the generation of organoid from reconstitutied cell lineages in the tissue. This may provide a new model for studying the regneration and malignant transformation of the tubal epithelium.

Targeting cancer stem cell pathways for cancer therapy

Since cancer stem cells (CSCs) were first identified in leukemia in 1994, they have been considered promising therapeutic targets for cancer therapy. These cells have self-renewal capacity and differentiation potential and contribute to multiple tumor malignancies, such as recurrence, metastasis, heterogeneity, multidrug resistance, and radiation resistance. The biological activities of CSCs are regulated by several pluripotent transcription factors, such as OCT4, Sox2, Nanog, KLF4, and MYC. In addition, many intracellular signaling pathways, such as Wnt, NF-κB (nuclear factor-κB), Notch, Hedgehog, JAK-STAT (Janus kinase/signal transducers and activators of transcription), PI3K/AKT/mTOR (phosphoinositide 3-kinase/AKT/mammalian target of rapamycin), TGF (transforming growth factor)/SMAD, and PPAR (peroxisome proliferator-activated receptor), as well as extracellular factors, such as vascular niches, hypoxia, tumor-associated macrophages, cancer-associated fibroblasts, cancer-associated mesenchymal stem cells, extracellular matrix, and exosomes, have been shown to be very important regulators of CSCs. Molecules, vaccines, antibodies, and CAR-T (chimeric antigen receptor T cell) cells have been developed to specifically target CSCs, and some of these factors are already undergoing clinical trials. This review summarizes the characterization and identification of CSCs, depicts major factors and pathways that regulate CSC development, and discusses potential targeted therapy for CSCs.

Tumor dormancy in bone

Background

Bone marrow is a common site of metastasis for a number of tumor types, including breast, prostate, and lung cancer, but the mechanisms controlling tumor dormancy in bone are poorly understood. In breast cancer, while advances in drug development, screening practices, and surgical techniques have dramatically improved survival rates in recent decades, metastatic recurrence in the bone remains common and can develop years or decades after elimination of the primary tumor.

Recent Findings

It is now understood that tumor cells disseminate to distant metastatic sites at early stages of tumor progression, leaving cancer survivors at a high risk of recurrence. This review will discuss mechanisms of bone lesion development and current theories of how dormant cancer cells behave in bone, as well as a number of processes suspected to be involved in the maintenance of and exit from dormancy in the bone microenvironment.

Conclusions

The bone is a complex microenvironment with a multitude of cell types and processes. Many of these factors, including angiogenesis, immune surveillance, and hypoxia, are thought to regulate tumor cell entry and exit from dormancy in different bone marrow niches.

Spheroid-Derived Cells From Renal Adenocarcinoma Have Low Telomerase Activity and High Stem-Like and Invasive Characteristics

Cancer stem cells (CSCs) are a theorized small subpopulation of cells within tumors thought to be responsible for metastasis, tumor development, disease progression, treatment-resistance, and recurrence. The identification, isolation, and biological characterization of CSCs may therefore facilitate the development of efficient therapeutic strategies targeting CSCs. This study aims to compare the biology and telomerase activity of CSCs to parental cells (PCs) in renal cancer. Renal CSCs were enriched from the ACHN cell line using a sphere culture system. Spheroid-derived cells (SDCs) and their adherent counterparts were compared with respect to their colony and sphere formation, expression of putative CSC markers, tumorigenicity in non-obese diabetic/severe combined immunodeficiency (NOD/SCID) mice, and invasiveness. The expression of genes associated with CSCs, stemness, EMT, apoptosis, and ABC transporters was also compared between the two populations using quantitative real-time PCR (qRT-PCR). Finally, telomerase activity, hTERT expression, and sensitivity to MST-312, a telomerase inhibitor, was investigated between the two populations. We demonstrated that a subpopulation of ACHN cells was capable of growing as spheroids with many properties similar to CSCs, including higher clonogenicity, superior colony- and sphere-forming ability, and stronger tumorigenicity and invasiveness. In addition, SDCs demonstrated a higher expression of markers for CSCs, stemness, EMT, apoptosis, and ABC transporter genes compared to PCs. The expression of hTERT and telomerase activity in SDCs was significantly lower than PCs; however, the SDC population was more sensitive to MST-312 compared to PCs. These findings indicate that the SDC population exhibits stem-like potential and invasive characteristics. Moreover, the reduced expression of hTERT and telomerase activity in SDCs demonstrated that the expressions of hTERT and telomerase activity are not always higher in CSCs. Our results also showed that MST-312 treatment inhibited SDCs more strongly than PCs and may therefore be useful as a complementary targeted therapy against renal CSCs in the future.

PTTG1: a Unique Regulator of Stem/Cancer Stem Cells in the Ovary and Ovarian Cancer

Origin of cancer stem cells (CSCs) and mechanisms by which oncogene PTTG1 contributes to tumor progression via CSCs is not known. Ovarian CSCs exhibit characteristics of self-renewal, tumor-initiation, growth, differentiation, drug resistance, and tumor relapse. A common location of putative origin, namely the ovarian surface epithelium, is shared between the normal stem and CSC compartments. Existence of ovarian stem cells and their co-expression with CSC signatures suggests a strong correlation between origin of epithelial cancer and CSCs. We hereby explored a putative oncogene PTTG1 (Securin), reported to be overexpressed in various tumors, including ovarian. We report a previously overlooked role of PTTG1 as a marker of CSCs thereby modulating CSC, germline, and stemness-related genes. We further characterized PTTG1's ability to regulate (cancer) stem cell-associated self-renewal and epithelial-mesenchymal transition pathways. Collectively, the data sheds light on a potential target expressed during ovarian tumorigenesis and metastatically disseminated ascites CSCs in the peritoneal cavity. Present study highlights this unconventional, under-explored role of PTTG1 in regulation of stem and CSC compartments in ovary, ovarian cancer and ascites and highlights it as a potential candidate for developing CSC specific targeted therapeutics.

Significant random signatures reveals new biomarker for breast cancer

BACKGROUND

In 2012, Venet et al. proposed that at least in the case of breast cancer, most published signatures are not significantly more associated with outcome than randomly generated signatures. They suggested that nominal p-value is not a good estimator to show the significance of a signature. Therefore, one can reasonably postulate that some information might be present in such significant random signatures.

METHODS

In this research, first we show that, using an empirical p-value, these published signatures are more significant than their nominal p-values. In other words, the proposed empirical p-value can be considered as a complimentary criterion for nominal p-value to distinguish random signatures from significant ones. Secondly, we develop a novel computational method to extract information that are embedded within significant random signatures. In our method, a score is assigned to each gene based on the number of times it appears in significant random signatures. Then, these scores are diffused through a protein-protein interaction network and a permutation procedure is used to determine the genes with significant scores. The genes with significant scores are considered as the set of significant genes.

RESULTS

First, we applied our method on the breast cancer dataset NKI to achieve a set of significant genes in breast cancer considering significant random signatures. Secondly, prognostic performance of the computed set of significant genes is evaluated using DMFS and RFS datasets. We have observed that the top ranked genes from this set can successfully separate patients with poor prognosis from those with good prognosis. Finally, we investigated the expression pattern of TAT, the first gene reported in our set, in malignant breast cancer vs. adjacent normal tissue and mammospheres.

CONCLUSION

Applying the method, we found a set of significant genes in breast cancer, including TAT, a gene that has never been reported as an important gene in breast cancer. Our results show that the expression of TAT is repressed in tumors suggesting that this gene could act as a tumor suppressor in breast cancer and could be used as a new biomarker.

Interstitial cells in calcified aortic valves have reduced differentiation potential and stem cell-like properties

Valve interstitial cells (VICs) are crucial in the development of calcific aortic valve disease. The purpose of the present investigation was to compare the phenotype, differentiation potential and stem cell-like properties of cells from calcified and healthy aortic valves. VICs were isolated from human healthy and calcified aortic valves. Calcification was induced with osteogenic medium. Unlike VICs from healthy valves, VICs from calcified valves cultured without osteogenic medium stained positively for calcium deposits with Alizarin Red confirming their calcific phenotype. Stimulation of VICs from calcified valves with osteogenic medium increased calcification (p = 0.02), but not significantly different from healthy VICs. When stimulated with myofibroblastic medium, VICs from calcified valves had lower expression of myofibroblastic markers, measured by flow cytometry and RT-qPCR, compared to healthy VICs. Contraction of collagen gel (a measure of myofibroblastic activity) was attenuated in cells from calcified valves (p = 0.04). Moreover, VICs from calcified valves, unlike cells from healthy valves had lower potential to differentiate into adipogenic pathway and lower expression of stem cell-associated markers CD106 (p = 0.04) and aldehyde dehydrogenase (p = 0.04). In conclusion, VICs from calcified aortic have reduced multipotency compared to cells from healthy valves, which should be considered when investigating possible medical treatments of aortic valve calcification.

Mitochondrial NIX Promotes Tumor Survival in the Hypoxic Niche of Glioblastoma

Cancer cells rely on mitochondrial functions to regulate key survival and death signals. How cancer cells regulate mitochondrial autophagy (mitophagy) in the tumor microenvironment as well as utilize mitophagy as a survival signal is still not well understood. Here, we elucidate a key survival mechanism of mitochondrial NIX-mediated mitophagy within the hypoxic region of glioblastoma, the most malignant brain tumor. NIX was overexpressed in the pseudopalisading cells that envelop the hypoxic-necrotic regions, and mitochondrial NIX expression was robust in patient-derived glioblastoma tumor tissues and glioblastoma stem cells. NIX was required for hypoxia and oxidative stress-induced mitophagy through NFE2L2/NRF2 transactivation. Silencing NIX impaired mitochondrial reactive oxygen species clearance, cancer stem cell maintenance, and HIF/mTOR/RHEB signaling pathways under hypoxia, resulting in suppression of glioblastoma survival in vitro and in vivo. Clinical significance of these findings was validated by the compelling association between NIX expression and poor outcome for patients with glioblastoma. Taken together, our findings indicate that the NIX-mediated mitophagic pathway may represent a key therapeutic target for solid tumors, including glioblastoma. SIGNIFICANCE: NIX-mediated mitophagy regulates tumor survival in the hypoxic niche of glioblastoma microenvironment, providing a potential therapeutic target for glioblastoma.Graphical Abstract: http://cancerres.aacrjournals.org/content/canres/79/20/5218/F1.large.jpg.

In Vivo Anti-Tumor Effects of Citral on 4T1 Breast Cancer Cells via Induction of Apoptosis and Downregulation of Aldehyde Dehydrogenase Activity

Breast cancer is the most commonly diagnosed cancer and the leading cause of cancer death among females globally. The tumorigenic activities of cancer cells such as aldehyde dehydrogenase (ALDH) activity and differentiation have contributed to relapse and eventual mortality in breast cancer. Thus, current drug discovery research is focused on targeting breast cancer cells with ALDH activity and their capacity to form secondary tumors. Citral (3,7-dimethyl-2,6-octadienal), from lemon grass (Cymbopogoncitrates), has been previously reported to have a cytotoxic effect on breast cancer cells. Hence, this study was conducted to evaluate the in vivo effect of citral in targeting ALDH activity of breast cancer cells. BALB/c mice were challenged with 4T1 breast cancer cells followed by daily oral feeding of 50 mg/kg citral or distilled water for two weeks. The population of ALDH⁺ tumor cells and their capacity to form secondary tumors in both untreated and citral treated 4T1 challenged mice were assessed by Aldefluor assay and tumor growth upon cell reimplantation in normal mice, respectively. Citral treatment reduced the size and number of cells with ALDH⁺ activity of the tumors in 4T1-challenged BALB/c mice. Moreover, citral-treated mice were also observed with smaller tumor size and delayed tumorigenicity after reimplantation of the primary tumor cells into normal mice. These findings support the antitumor effect of citral in targeting ALDH⁺ cells and tumor recurrence in breast cancer cells.

Cancer cell reprogramming: a promising therapy converting malignancy to benignity

In the past decade, remarkable progress has been made in reprogramming terminally differentiated somatic cells and cancer cells into induced pluripotent cells and cancer cells with benign phenotypes. Recent studies have explored various approaches to induce reprogramming from one cell type to another, including lineage-specific transcription factors-, combinatorial small molecules-, microRNAs- and embryonic microenvironment-derived exosome-mediated reprogramming. These reprogramming approaches have been proven to be technically feasible and versatile to enable re-activation of sequestered epigenetic regions, thus driving fate decisions of differentiated cells. One of the significant utilities of cancer cell reprogramming is the therapeutic potential of retrieving normal cell functions from various malignancies. However, there are several major obstacles to overcome in cancer cell reprogramming before clinical translation, including characterization of reprogramming mechanisms, improvement of reprogramming efficiency and safety, and development of delivery methods. Recently, several insights in reprogramming mechanism have been proposed, and determining progress has been achieved to promote reprogramming efficiency and feasibility, allowing it to emerge as a promising therapy against cancer in the near future. This review aims to discuss recent applications in cancer cell reprogramming, with a focus on the clinical significance and limitations of different reprogramming approaches, while summarizing vital roles played by transcription factors, small molecules, microRNAs and exosomes during the reprogramming process.

OCT4B1 Promoted EMT and Regulated the Self-Renewal of CSCs in CRC: Effects Associated with the Balance of miR-8064/PLK1

Cancer stem cells (CSCs) are the main cause of tumor generation, recurrence, metastasis, and therapy failure in various malignancies including colorectal cancer (CRC). Accumulating evidence suggests that tumor cells can acquire CSC characteristics through the epithelial-mesenchymal transition (EMT) process. However, the molecular mechanism of CSCs remains unclear. OCT4B1 is a transcript of OCT4, which is initially expressed in embryonic stem and carcinoma cells, and is involved in the regulation and maintenance of an undifferentiated state of stem cells. In this study, three-dimensional (3D) microspheres were confirmed as CRC stem cells. Compared with that of parental cells, their self-renewal ability was significantly increased, and OCT4B1 expression was increased and promoted the EMT process. The knockdown of OCT4B1 decreased the self-renewal of CSCs and reversed EMT. Moreover, OCT4B1 induced the expression of Polo-like kinase 1 (PLK1), which is a key regulator of EMT in tumor cells. Further examination showed that OCT4B1 regulated the miR-8064/PLK1 balance to exert its function. Taken together, our data suggest that OCT4B1 may be involved in regulating the self-renewal of colorectal CSCs through EMT, which is at least partially due to the miR-8064/PLK1 balance. This study indicates that OCT4B1 is a potential therapeutic target for CRC by targeting CSCs.

The Mode-of-Action of Targeted Alpha Therapy Radium-223 as an Enabler for Novel Combinations to Treat Patients with Bone Metastasis

Bone metastasis is a common clinical complication in several cancer types, and it causes a severe reduction in quality of life as well as lowering survival time. Bone metastases proceed through a vicious self-reinforcing cycle that can be osteolytic or osteoblastic in nature. The vicious cycle is characterized by cancer cells residing in bone releasing signal molecules that promote the differentiation of osteoclasts and osteoblasts either directly or indirectly. The increased activity of osteoclasts and osteoblasts then increases bone turnover, which releases growth factors that benefit metastatic cancer cells. In order to improve the prognosis of patients with bone metastases this cycle must be broken. Radium-223 dichloride (radium-223), the first targeted alpha therapy (TAT) approved, is an osteomimetic radionuclide that is incorporated into bone metastases where its high-linear energy transfer alpha radiation disrupts both the activity of bone cells and cancer cells. Therefore, radium-223 treatment has been shown preclinically to directly affect cancer cells in both osteolytic breast cancer and osteoblastic prostate cancer bone metastases as well as to inhibit the differentiation of osteoblasts and osteoclasts. Clinical studies have demonstrated an increase in survival in patients with metastatic castration-resistant prostate cancer. Due to the effectiveness and low toxicity of radium-223, several novel combination treatment strategies are currently eliciting considerable research interest.

Metabolism and epigenetics of pancreatic cancer stem cells

Pancreatic Cancer (PDA) is an aggressive malignancy characterized by early spread and a high mortality. Current studies suggest that a subpopulation of cells exist within tumors, cancer stem cell (CSC), which are capable of self-renewal and give rise to unique progeny which form the major neoplastic cellular component of tumors. While CSCs constitute a small cellular subpopulation within the tumor, their resistance to chemotherapy and radiation make them an important therapeutic target for eradication. Along with distinctive phenotypic properties, CSCs possess a unique metabolic plasticity allowing them to rapidly respond and adapt to environmental changes. These cells and their progeny also display a significantly altered epigenetic state with distinctive patterns of DNA methylation. Several mechanisms of cross-talk between epigenetic and metabolic pathways in PDA exist which ultimately contribute to the observed cellular plasticity and enhanced tumorigenesis. In this review we discuss various examples of this metabolic-epigenetic interplay and how it may constitute a new avenue for therapy specifically targeting CSCs in PDA.

Targeting the differentiation of gastric cancer cells (KATO‑III) downregulates epithelial‑mesenchymal and cancer stem cell markers

The aim of the present study was to analyze the acquisition of the differentiated phenotype in the human gastric signet ring cell adenoma cancer KATO‑III cell line in vitro. The morphology of KATO‑III cells was explored by microcinematography. Different cytokines secreted by both adherent and non‑adherent KATO‑III cells into medium were observed. The cancer stem cell phenotypes were identified by reverse transcription‑quantitative polymerase chain reaction using primers (E‑Cad, Slug, Snail, vimentin, NANOG, NESTIN, OCT3/4 and C‑X‑C motif chemokine receptor 4) or antibodies [cluster of differentiation (CD)90 and CD117] by flow cytometry (FACS). The influence of the induction media for the differentiation of mesenchymal cells was studied through viability and proliferation assays, by evaluating gene expression and the expression of markers via FACS. Cell viability and cell cycle distribution were evaluated following the treatment of KATO‑III with acetyl salicylic acid and using the induction media as an inhibitor of epithelial‑mesenchymal transition (EMT) and heparanase. A total of 3 phenotypes of KATO‑III were observed (adherent, non‑adherent and cell cluster), which have internal potential for cell transition into one of the other phenotypes. KATO‑III was differentiated into adipocyte‑, chondrocyte‑, osteocyte‑ and neurocyte‑like cells by the induction media. Identification of the induced cells was conducted using cell dyes. Reduced mRNA expression of EMT‑associated molecules, stem cell markers and heparanase was observed with acetyl salicylic acid and induction media. An inhibitory effect of acetyl salicylic acid and the induction media was also noted in regard to cell proliferation. In addition, acetyl salicylic acid induced G0/G1 phase cell cycle arrest in KATO‑III cells. In conclusion, the induction of the differentiation of cancer stem cells into non‑proliferating cells offers the possibility for novel drug design to overcome the issues associated with metastasis, drug resistance and systemic toxicity with improved therapeutic efficacy.

A novel curcumin analog inhibits canonical and non-canonical functions of telomerase through STAT3 and NF-κB inactivation in colorectal cancer cells

Curcumin is a biologically active polyphenol that exists in Indian spice turmeric. It has been reported that curcumin exerted anti-inflammatory, anti-oxidant and anti-cancer effects in numerous in vitro and in vivo studies. However, it is not well-understood the molecular mechanism of curcumin for the cancer stem cells and telomerase in colorectal cancer. In this study, compound 19, a nitrogen-containing curcumin analog, was used to treat human colorectal cancer cells. Compound 19 showed a greater anti-proliferative activity than curcumin while displayed no significant toxicity toward normal human colon epithelial cells. Compound 19 exerted anti-inflammatory activities by deactivating STAT3 and NF-κB. In cancer stem cell populations, CD44, Oct-4 and ALDHA1 expressions were abolished upon treating with compound 19. Cancer stem cell biomarkers CD51 and CD133 positive populations were reduced and telomerase activities were decreased with the reduced STAT3 binding to hTERT promoters. This means compound 19 dually inhibits canonical and non-canonical functions of telomerase. Furthermore, compound 19 treatments induced cell cycle arrest at G1 phase and apoptosis. Human apoptosis-related array screening revealed that activated caspase 3, catalase, clusterin and cytochrome C led to apoptosis. Taken together, our data suggest that compound 19 can be a novel therapeutic agent for metastatic colorectal cancer by concurrently targeting STAT3 and NF-κB signaling pathways.

A New Label-Free Approach to Glioblastoma Cancer Stem Cell Sorting and Detection

Cancer stem cells (CSCs) play critical roles in cancer, making them important targets for new diagnostic and therapeutic approaches. Since CSCs are heterogeneous and not abundant in tumors, and few specific markers for these cells currently exist, new methods to isolate and characterize them are required. To address this issue, we developed a new label-free methodology to isolate, enrich, and identify CSCs from an heterogeneous tumor cell subpopulation using a cell sorting method (sedimentation field flow fractionation, SdFFF) and a biosensor as a detector. Enrichment was optimized using an original protocol and U87-MG glioblastoma cells cultured in a normal (N) or defined (D) medium (± fetal bovine serum, FBS) under normoxic (N, p_O2 = 20%) or hypoxic (H, p_O2 < 2%) conditions to obtain four cell populations: NN, NH, DN, and DH. After elution of CSCs via SdFFF using the hyperlayer mode (inertial elution mode for micrometer-sized species), we isolated eight subpopulations with distinct CSC contents based on phenotypical and functional properties, ranging from NN F1 with a lower CSC content to DH F3 with a higher CSC content. Reflecting biological differences, the intrinsic intracellular dielectric permittivity increased from NN to DH conditions. The largest difference in electromagnetic signature was observed between NN F1 and DH F3, in which the CSC content was lowest and highest, respectively. The results demonstrate that microwave dielectric spectroscopy can be used to reliably and efficiently distinguish stem cell characteristics. This new instrumental and methodological approach is an important innovation that allows both enrichment and detection of CSCs, opening the door to novel diagnostic and therapeutic approaches.

Exosomes, metastases, and the miracle of cancer stem cell markers

Cancer-initiating cells (CIC) are the driving force in tumor progression. There is strong evidence that CIC fulfill this task via exosomes (TEX), which modulate and reprogram stroma, nontransformed cells, and non-CIC. Characterization of CIC, besides others, builds on expression of CIC markers, many of which are known as metastasis-associated molecules. We here discuss that the linkage between CIC/CIC-TEX and metastasis-associated molecules is not fortuitously, but relies on the contribution of these markers to TEX biogenesis including loading and TEX target interactions. In addition, CIC markers contribute to TEX binding- and uptake-promoted activation of signaling cascades, transcription initiation, and translational control. Our point of view will be outlined for pancreas and colon CIC highly expressing CD44v6, Tspan8, EPCAM, claudin7, and LGR5, which distinctly but coordinately contribute to tumor progression. Despite overwhelming progress in unraveling the metastatic cascade and the multiple tasks taken over by CIC-TEX, there remains a considerable gap in linking CIC biomarkers, TEX, and TEX-initiated target modulation with metastasis. We will try to outline possible bridges, which could allow depicting pathways for new and expectedly powerful therapeutic interference with tumor progression.

Immunohistochemical Expression of Nanog and Its Relation with Clinicopathologic Characteristics in Breast Ductal Carcinoma

BACKGROUND

Cancer stem cells (CSCs) are a group of tumor cells with self-renewal property and differentiation potential. CSCs play a crucial role in malignant progression of several types of tumors. However, what is still controversial is the clinicopathological relationship between the Nanog marker and its prognostic value in the patients with breast cancer. The expression of Nanog in the patients with breast cancer and its correlation with clinicopathological prognostic factors was explored in the present study.

METHODS

A sample of 120 breast cancer tissues was obtained from the patients who referred to Imam Khomeini Hospital in Sari City, Iran during January 2012 and December 2016. The associations between Nanog expression and clinicopathological factors were analyzed based on immunohistochemical analysis.

RESULTS

The expression of Nanog was detected in 67 (55.8%) patients with a high expression rate in 24 (36%) cases (staining index ≥3). Moreover, there was a statistically significant relationship between Nanog expression and clinicopathological factors, including tumor grade (p = 0.001), lymph node metastasis (p = 0.01), and the stage of the disease (p = 0.003).

CONCLUSION

Findings of the study indicate that Nanog may act as a biomarker for prognostic prediction in patients with breast cancer.

CD44 epithelial isoform inversely associates with invasive characteristics of colorectal cancer

Aim: There is no consensus regarding the clinical significance of CD44 and CD24 as cancer stem cell (CSC) marker in colorectal cancer (CRC). Methodology: A total of 494 CRC samples (2008-2017) were assessed for CD44 (epithelial isoform) and CD24 expression using tissue microarray. Results: CD24 individually or in combination with CD44 was not associated with any of the clinicopathologic characteristics of the tumor. CD44 expression was inversely associated with pathological Tumor, Node, Metastasis (pTNM) lower stages (p = 0.038) and lymphatic invasion (p = 0.05). Conclusion: In summary, the epithelial isoform of CD44 is inversely associated with invasive characteristics of CRC.

Role of OCT4 in cancer stem-like cells and chemotherapy resistance

Cancer stem-like cells (CSCs) contribute to the tumorigenicity, progression, and chemoresistance of cancers. It is not known whether CSCs arise from normal stem cells or if they arise from differentiated cancer cells by acquiring self-renewal features. These CSCs share stem cell markers that normal stem cells express. There is a rising interest in octamer-binding transcription factor 4 (OCT4), one of the stem cell factors that are essential in embryogenesis and pluripotency. OCT4 is also overexpressed in CSCs of various cancers. Although the majority of the studies in CSCs reported a positive association between the expression of OCT4 and chemoresistance and an inverse correlation between OCT4 and clinical prognosis, there are studies rebuking these findings, possibly due to the sparsity of stem cells within tumors and the heterogeneity of tumors. In addition, post-translational modification of OCT4 affects its activity and warrants further investigation for its association with chemoresistance and prognosis.

GSK3β regulates epithelial-mesenchymal transition and cancer stem cell properties in triple-negative breast cancer

BACKGROUND

Triple-negative breast cancers (TNBCs), which lack receptors for estrogen, progesterone, and amplification of epidermal growth factor receptor 2, are highly aggressive. Consequently, patients diagnosed with TNBCs have reduced overall and disease-free survival rates compared to patients with other subtypes of breast cancer. TNBCs are characterized by the presence of cancer cells with mesenchymal properties, indicating that the epithelial to mesenchymal transition (EMT) plays a major role in the progression of this disease. The EMT program has also been implicated in chemoresistance, tumor recurrence, and induction of cancer stem cell (CSC) properties. Currently, there are no targeted therapies for TNBC, and hence, it is critical to identify the novel targets to treat TNBC.

METHODS

A library of compounds was screened for their ability to inhibit EMT in cells with mesenchymal phenotype as assessed using the previously described Z-cad reporters. Of the several drugs tested, GSK3β inhibitors were identified as EMT inhibitors. The effects of GSK3β inhibitors on the properties of TNBC cells with a mesenchymal phenotype were assessed using qRT-PCR, flow cytometry, western blot, mammosphere, and migration and cell viability assays. Publicly available datasets also were analyzed to examine if the expression of GSK3β correlates with the overall survival of breast cancer patients.

RESULTS

We identified a GSK3β inhibitor, BIO, in a drug screen as one of the most potent inhibitors of EMT. BIO and two other GSK3β inhibitors, TWS119 and LiCl, also decreased the expression of mesenchymal markers in several different cell lines with a mesenchymal phenotype. Further, inhibition of GSK3β reduced EMT-related migratory properties of cells with mesenchymal properties. To determine if GSK3β inhibitors target mesenchymal-like cells by affecting the CSC population, we employed mammosphere assays and profiled the stem cell-related cell surface marker CD44+/24- in cells after exposure to GSK3β inhibitors. We found that GSK3β inhibitors indeed decreased the CSC properties of cell types with mesenchymal properties. We treated cells with epithelial and mesenchymal properties with GSK3β inhibitors and found that GSK3β inhibitors selectively kill cells with mesenchymal attributes while sparing cells with epithelial properties. We analyzed patient data to identify genes predictive of poor clinical outcome that could serve as novel therapeutic targets for TNBC. The Wnt signaling pathway is critical to EMT, but among the various factors known to be involved in Wnt signaling, only the higher expression of GSK3β correlated with poorer overall patient survival.

CONCLUSIONS

Taken together, our data demonstrate that GSK3β is a potential target for TNBCs and suggest that GSK3β inhibitors could serve as selective inhibitors of EMT and CSC properties for the treatment of a subset of aggressive TNBC. GSK3β inhibitors should be tested for use in combination with standard-of-care drugs in preclinical TNBC models.

Role of nitric oxide in pancreatic cancer cells exhibiting the invasive phenotype

Pancreatic cancer is a highly metastatic tumor with an extremely low 5-year survival rate. Lack of efficient diagnostics and dearth of effective therapeutics that can target the cancer as well as the microenvironment niche are the reasons for limited success in treatment and management of this disease. Cell invasion through extracellular matrix (ECM) involves the complex regulation of adhesion to and detachment from ECM and its understanding is critical to metastatic potential of pancreatic cancer. To understand the characteristics of these cancer cells and their ability to metastasize, we compared human pancreatic cancer cell line, PANC-1 and its invading phenotype (INV) collected from transwell inserts. The invasive cell type, INV, exhibited higher resistance to Carbon-ion radiation compared to whole cultured (normally dish-cultured) PANC-1 (WCC), and had more efficient in vitro spheroid formation capability. Invasiveness of INV was hampered by nitric oxide synthase (NOS) inhibitors, suggesting that nitric oxide (NO) plays a cardinal role in PANC-1 invasion. In addition, in vitro studies indicated that a MEK-ERK-dependent, JAK independent mechanism through which NOS/NO modulate PANC-1 invasiveness. Suspended INV showed enhanced NO production as well as induction of several pro-metastatic, and stemness-related genes. NOS inhibitor, l-NAME, reduced the expression of these pro-metastatic or stemness-related genes, and dampened spheroid formation ability, suggesting that NO can potentially influence pancreatic cancer aggressiveness. Furthermore, xenograft studies with INV and WCC in NSG mouse model revealed a greater ability of INV compared to WCC, to metastasize to the liver and l-NAME diminished the metastatic lesions in mice injected with INV. Overall, data suggest that NO is a key player associated with resistance to radiation and metastasis of pancreatic cancer; and inhibition of NOS demonstrates therapeutic potential as observed in the animal model by specifically targeting the metastatic cells that harbor stem-like features and are potentially responsible for relapse.

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Highly invasive pancreatic cancer cell line, collected from transwell inserts showed increased resistance to C-ion radiation.

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NO is a key player in pancreatic cancer aggressiveness inducing pro-metastatic and stemness-related genes.

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NOS/NO modulate invasiveness through a MEK-ERK dependent, JAK signaling independent mechanism.

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NOS inhibition showed promising therapeutic potential in mouse model by reversing the pro-metastatic phenotype.

Not Everyone Fits the Mold: Intratumor and Intertumor Heterogeneity and Innovative Cancer Drug Design and Development

Disruptive innovations in medicine are game-changing in nature and bring about radical shifts in the way we understand human diseases, their treatment, and/or prevention. Yet, disruptive innovations in cancer drug design and development are still limited. Therapies that cure all cancer patients are in short supply or do not exist at all. Chief among the causes of this predicament is drug resistance, a mechanism that is much more dynamic than previously understood. Drug resistance has limited the initial success experienced with biomarker-guided targeted therapies as well. A major contributor to drug resistance is intratumor heterogeneity. For example, within solid tumors, there are distinct subclones of cancer cells, presenting profound complexity to cancer treatment. Well-known contributors to intratumor heterogeneity are genomic instability, the microenvironment, cellular genotype, cell plasticity, and stochastic processes. This expert review explains that for oncology drug design and development to be more innovative, we need to take into account intratumor heterogeneity. Initially thought to be the preserve of cancer cells, recent evidence points to the highly heterogeneous nature and diverse locations of stromal cells, such as cancer-associated fibroblasts (CAFs) and cancer-associated macrophages (CAMs). Distinct subpopulations of CAFs and CAMs are now known to be located immediately adjacent and distant from cancer cells, with different subpopulations exerting different effects on cancer cells. Disruptive innovation and precision medicine in clinical oncology do not have to be a distant reality, but can potentially be achieved by targeting these spatially separated and exclusive cancer cell subclones and CAF subtypes. Finally, we emphasize that disruptive innovations in drug discovery and development will likely come from drugs whose effect is not necessarily tumor shrinkage.

Stem Cell Applications for Treatment of Cancer and Autoimmune Diseases: Its Promises, Obstacles, and Future Perspectives

Since the original discovery of stem cells, a new era of promising results has emerged in the clinical application of stem cells for the treatment of several important diseases, including cancer and autoimmune diseases. The plentiful research on stem cells during the past decades has provided significant information on the developmental, morphological, and physiological processes that govern tissue and organ formation, maintenance, and regeneration; cellular differentiation; molecular processes; and tissue homeostasis. In this review, we present the history of the use of stem cells in different clinical applications. Furthermore, we discuss the various therapeutic options for stem cells in cancer, followed by the role of stem cells in the treatment of autoimmune disorders. Additionally, we highlight the risks of and obstacles to the application of stem cells in clinical practice. Ultimately, we show future perspectives in stem cell use, with an aim to improve the clinical usefulness of stem cells.

Metabolomic Studies of Live Single Cancer Stem Cells Using Mass Spectrometry

Cancer stem cells (CSCs) are rare types of cells responsible for tumor development, relapse, and metastasis. However, current research in CSC biology is largely limited by the difficulty of obtaining sufficient CSCs. Single-cell analysis techniques are promising tools for CSC-related studies. Here, we used the Single-probe mass spectrometry (MS) technique to investigate the metabolic features of live colorectal CSCs at the single-cell level. Experimental data were analyzed using statistical analysis methods, including the t-test and partial least squares discriminant analysis. Our results indicate that the overall metabolic profiles of CSCs are distinct from non-stem cancer cells (NSCCs). Specifically, we demonstrated that tricarboxylic acid (TCA) cycle metabolites are more abundant in CSCs compared to NSCCs, indicating their major energy production pathways are different. Moreover, CSCs have relatively higher levels of unsaturated lipids. Inhibiting the activities of stearoyl-CoA desaturase-1 (SCD1), nuclear factor κB (NF-κB), and aldehyde dehydrogenases (ALDH1A1) in CSCs significantly reduced the abundances of unsaturated lipids and hindered the formation of spheroids, resulting in reduced stemness of CSCs. Our techniques and experimental protocols can be potentially used for metabolomic studies of other CSCs and rare types of cells and provide a new approach to discovering functional biomarkers as therapeutic targets.

Use of DNA-generated gold nanoparticles to radiosensitize and eradicate radioresistant glioma stem cells

The surface reactivity of gold nanoparticles (AuNPs) is receiving attention as a radiosensitizer of cancer cells for radiation therapy and/or as a drug carrier to target cells. This study demonstrates the potential of DNA-AuNPs (prepared by mixing calf thymus DNA with HAuCl₄ solution) as a radiosensitizer of human glioma cells that have cancer stem cell (CSC)-like properties, to reduce their survival. CSC-like U251MG-P1 cells and their parental glioblastoma U251MG cells are treated with a prepared DNA-AuNP colloid. The radiosensitivity of the resultant AuNP-associated cells are significantly enhanced. To reveal the mechanism by which survival is reduced, the generation of reactive oxygen species (ROS), apoptosis induction, or DNA damage in the cells is assayed using the fluorescent dye DCFDA, annexin V-FITC/PI, and foci formation of γ-H2AX, respectively. X-ray irradiation with administration of AuNPs overcomes the radioresistance of U251MG-P1 cells. It does not induce ROS generation or apoptosis in the cells but enhances the number of abnormal nuclei with abundant γ-H2AX foci, which is judged as cell death by mitotic catastrophe. The AuNP association with the cells effectively induces mitotic catastrophe in x-ray-irradiated CSC-like cells, implicating that DNA-AuNPs might be a promising tool to develop an efficient radiosensitizer against CSC.

Gpn3 Is Essential for Cell Proliferation of Breast Cancer Cells Independent of Their Malignancy Degree

Successful therapies for patients with breast cancer often lose their initial effectiveness. Thus, identifying new molecular targets is a constant goal in the fight against breast cancer. Gpn3 is a protein required for RNA polymerase II nuclear targeting in both yeast and human cells. We investigated here the effect of suppressing Gpn3 expression on cell proliferation in a progression series of isogenic cell lines derived from the nontumorigenic MCF-10A breast cells that recapitulate different stages of breast carcinogenesis. Gpn3 protein levels were comparable in all malignant derivatives of the nontumorigenic MCF-10A cells. shRNA-mediated inhibition of Gpn3 expression markedly decreased cell proliferation in all MCF-10A sublines. A fraction of the largest RNA polymerase II subunit Rpb1 was retained in the cytoplasm, but most Rpb1 remained nuclear after suppressing Gpn3 in all cell lines studied. Long-term proliferation experiments in cells with suppressed Gpn3 expression resulted in the eventual loss of all isogenic cell lines but MCF-10CA1d.cl1. In MCF-10CA1d.cl1 cells, Gpn3 knockdown reduced the proliferation of breast cancer stem cells as evaluated by mammosphere assays. After the identification that Gpn3 plays a key role in cell proliferation in mammary epithelial cells independent of the degree of transformation, we also analyzed the importance of Gpn3 in other human breast cancer cell lines from different subtypes. Gpn3 was also required for cell proliferation and nuclear translocation of RNA polymerase II in such cellular models. Altogether, our results show that Gpn3 is essential for breast cancer cell proliferation regardless of the transformation level, indicating that Gpn3 could be considered a molecular target for the development of new antiproliferative therapies. Importantly, our analysis of public data revealed that Gpn3 overexpression was associated with a significant decrease in overall survival in patients with estrogen receptor-positive and Human epidermal growth factor receptor 2 (HER2+) breast cancer, supporting our proposal that targeting Gpn3 could potentially benefit patients with breast cancer.

EPH Profiling of BTIC Populations in Glioblastoma Multiforme Using CyTOF

The ability to elucidate the phenotype of brain tumor initiating cell (BTIC) in the context of bulk tumor in glioblastoma multiforme (GBM) provides significant therapeutic benefits for therapeutic evaluation. For the identification of such an elusive and rare subpopulation of cells, a single cell analysis technology with deep profiling capabilities known as Mass Cytometry (CyTOF) can prove to be highly useful. CyTOF circumvents the spectral overlap limitations of traditional flow cytometry by replacing fluorophores with metal isotope tags, allowing the accurate detection of significantly more parameters at the same time. In this chapter, we demonstrate that synthetic antibodies can be conjugated with metal isotope tags for CyTOF analysis, resulting in the development of a highly tailored, custom multi-parameter panel. This toolset was used to stain patient-derived GBM cells, which was analyzed via CyTOF. Analysis software viSNE and SPADE were applied to study the co-expression patterns of the Eph Receptor (EphR) family and several putative BTIC markers in GBM, resulting in the identification of a distinct group of cells consistent with a BTIC subpopulation. This approach can be readily adapted to the detection of cancer stem-like cells in other cancer types.

Pinostrobin inhibits proliferation and induces apoptosis in cancer stem-like cells through a reactive oxygen species-dependent mechanism

Current treatments and targeted therapies for malignancies are limited due to their severe toxicity and the development of resistance against such treatments, which leads to relapse. Past evidence has indicated that a number of plant-derived dietary agents possess biological activity against highly tumorigenic and resistant cell populations associated with cancer relapse. These subpopulations, termed cancer stem-like cells (CSCs), have been targeted with plant-derived dietary flavonoids. The present study was undertaken to assess the anti-proliferative potential of pinostrobin, a dietary flavonoid, against CSCs. Sphere-forming cells were developed from HeLa cell lines using specific culture conditions. The existence of a CSC population was confirmed by the morphological examination and analysis of surface markers using confocal microscopy and flow cytometry. The effect of pinostrobin on the cell viability of the CSC population, evaluated through MTT reduction assays and the expression levels of surface markers (CD44⁺ and CD24⁺), was studied through various biological assays. HeLa-derived CSCs showed higher CD44⁺ and lower CD24⁺ expression. Pinostrobin inhibited the self-renewal capacity and sphere formation efficiency of CSCs in a dose-dependent manner. Increased ROS production, and decreased mitochondrial membrane potential and CD44⁺ expression indicated that pinostrobin promoted ROS-mediated apoptosis in CSCs. These results thus demonstrate the therapeutic potential and effectiveness of pinostrobin in the chemoprevention and relapse of cancer by targeting the CSC population. Thus, pinostrobin, in combination with currently available chemo and radiation therapies, could possibly be used as a safe strategy to alleviate adverse treatment effects, together with enhancing the efficacy.

The anti-proliferative potential of pinostrobin, a dietary flavonoid, is evaluated against cancer stem-like cells.

Nutritional stress reprograms dedifferention in glioblastoma multiforme driven by PTEN/Wnt/Hedgehog axis: a stochastic model of cancer stem cells

The emergence and maintenance of cancer stem-like cells (CSCs) are usually governed by tumor niche. Tumor niche always provides metabolic challenges to cancer cells and CSCs mostly because of tissue hypoxia. However, the role of micro-environmental nutritional stress (NS) in dedifferentiation of cancer cells is poorly defined. Here, we developed a stochastic model of CSCs by gradual nutritional deprivation in glioblastoma multiforme (GBM) cells used as a model system. Nutritional deprivation induced enhanced expression of glioblastoma stem-like cells (GSCs)-specific biomarkers with higher invasive and angiogenic properties. This NS-induced cells showed higher xenobiotic efflux ability, and hence exhibit resistance to multiple anticancer drugs. In the molecular level, such NS activated Wnt and Hedgehog (Hh) signaling pathways by stabilizing β-catenin and Gli1, respectively, through modulation of GSK3β/AKT axis. GBM-specific PTEN (phosphatase and tensin homolog) mutation contributed to better phenoconversion toward GSCs. Knocking down of PTEN coupled with NS induction enhanced neurosphere formation, GSC-specific biomarker expressions, and activation of Wnt/Hh signaling. Thus, such an in-depth understanding of dedifferentiation of GBM cells to GSCs under NS suggested that targeting Wnt/Hh signaling possibly be a better therapeutic approach.

Inhibition of skin carcinogenesis by suppression of NF-κB dependent ITGAV and TIMP-1 expression in IL-32γ overexpressed condition

BACKGROUND

Interleukin-32 (IL-32) has been associated with various diseases. Previous studies have shown that IL-32 inhibited the development of several tumors. However, the role of IL-32γ, an isotype of IL-32, in skin carcinogenesis remains unknown.

METHODS

We compared 7,12-Dimethylbenz[a]anthracene/12-O-Tetradecanoylphorbol-13-acetate (DMBA/TPA)-induced skin carcinogenesis in wild type (WT) and IL-32γ-overexpressing mice to evaluate the role of IL-32γ. We also analyzed cancer stemness and NF-κB signaling in skin cancer cell lines with or without IL-32γ expression by western blotting, quantitative real-time PCR and immunohistochemistry analysis.

RESULTS

Carcinogen-induced tumor incidence in IL-32γ mice was significantly reduced in comparison to that in WT mice. Infiltration of inflammatory cells and the expression levels of pro-inflammatory mediators were decreased in the skin tumor tissues of IL-32γ mice compared with WT mice. Using a genome-wide association study analysis, we found that IL-32 was associated with integrin αV (ITGAV) and tissue inhibitor of metalloproteinase-1 (TIMP-1), which are critical factor for skin carcinogenesis. Reduced expression of ITGAV and TIMP-1 were identified in DMBA/TPA-induced skin tissues of IL-32γ mice compared to that in WT mice. NF-κB activity was also reduced in DMBA/TPA-induced skin tissues of IL-32γ mice. IL-32γ decreased cancer cell sphere formation and expression of stem cell markers, and increased chemotherapy-induced cancer cell death. IL-32γ also downregulated expression of ITGAV and TIMP-1, accompanied with the inhibition of NF-κB activity. In addition, IL-32γ expression with NF-κB inhibitor treatment further reduced skin inflammation, epidermal hyperplasia, and cancer cell sphere formation and downregulated expression levels of ITGAV and TIMP-1.

CONCLUSIONS

These findings indicated that IL-32γ suppressed skin carcinogenesis through the inhibition of both stemness and the inflammatory tumor microenvironment by the downregulation of TIMP-1 and ITGAV via inactivation of NF-κB signaling.

Pancreatic cancer stem cells: Perspectives on potential therapeutic approaches of pancreatic ductal adenocarcinoma

Pancreatic ductal adenocarcinoma is one of the most aggressive solid tumours of the pancreas, characterised by a five-year survival rate less than 8%. Recent reports that pancreatic cancer stem cells (PCSCs) contribute to the tumorigenesis, progression, and chemoresistance of pancreatic cancer have prompted the investigation of new therapeutic approaches able to directly target PCSCs. In the present paper the non-cancer related drugs that have been proposed to target CSCs that could potentially combat pancreatic cancer are reviewed and evaluated. The role of some pathways and deregulated proteins in PCSCs as new therapeutic targets are also discussed with a focus on selected specific inhibitors. Finally, advances in the development of nanoparticles for targeting PCSCs and site-specific drug delivery are highlighted, and their limitations considered.

Krüppel-like factor 9 and histone deacetylase inhibitors synergistically induce cell death in glioblastoma stem-like cells

Background

The dismal prognosis of patients with glioblastoma (GBM) is attributed to a rare subset of cancer stem cells that display characteristics of tumor initiation, growth, and resistance to aggressive treatment involving chemotherapy and concomitant radiation. Recent research on the substantial role of epigenetic mechanisms in the pathogenesis of cancers has prompted the investigation of the enzymatic modifications of histone proteins for therapeutic drug targeting. In this work, we have examined the function of Krüppel-like factor 9 (KLF9), a transcription factor, in chemotherapy sensitization to histone deacetylase inhibitors (HDAC inhibitors).

Methods

Since GBM neurosphere cultures from patient-derived gliomas are enriched for GBM stem-like cells (GSCs) and form highly invasive and proliferative xenografts that recapitulate the features demonstrated in human patients diagnosed with GBM, we established inducible KLF9 expression systems in these GBM neurosphere cells and investigated cell death in the presence of epigenetic modulators such as histone deacetylase (HDAC) inhibitors.

Results

We demonstrated that KLF9 expression combined with HDAC inhibitor panobinostat (LBH589) dramatically induced glioma stem cell death via both apoptosis and necroptosis in a synergistic manner. The combination of KLF9 expression and LBH589 treatment affected cell cycle by substantially decreasing the percentage of cells at S-phase. This phenomenon is further corroborated by the upregulation of cell cycle inhibitors p21 and p27. Further, we determined that KLF9 and LBH589 regulated the expression of pro- and anti- apoptotic proteins, suggesting a mechanism that involves the caspase-dependent apoptotic pathway. In addition, we demonstrated that apoptosis and necrosis inhibitors conferred minimal protective effects against cell death, while inhibitors of the necroptosis pathway significantly blocked cell death.

Conclusions

Our findings suggest a detailed understanding of how KLF9 expression in cancer cells with epigenetic modulators like HDAC inhibitors may promote synergistic cell death through a mechanism involving both apoptosis and necroptosis that will benefit novel combinatory antitumor strategies to treat malignant brain tumors.

Novel molecular insights and new therapeutic strategies in osteosarcoma

Osteosarcoma (OS) is one of the most prevalent malignant cancers with lower survival and poor overall prognosis mainly in children and adolescents. Identifying the molecular mechanisms and OS stem cells (OSCs) as new concepts involved in disease pathogenesis and progression may potentially lead to new therapeutic targets. Therefore, therapeutic targeting of OSCs can be one of the most important and effective strategies for the treatment of OS. This review describes the new molecular targets of OS as well as novel therapeutic approaches in the design of future investigations and treatment.

4Mu Decreases CD47 Expression on Hepatic Cancer Stem Cells and Primes a Potent Antitumor T Cell Response Induced by Interleukin-12

The tumor microenvironment (TME) represents a complex interplay between different cellular components, including tumor cells and cancer stem cells (CSCs), with the associated stroma; such interaction promotes tumor immune escape and sustains tumor growth. Several experimental approaches for cancer therapy are focused on TME remodeling, resulting in increased antitumor effects. We previously demonstrated that the hyaluronan synthesis inhibitor 4-methylumbelliferone (4Mu) decreases liver fibrosis and induces antitumor activity in hepatocellular carcinoma (HCC). In this work, 4Mu, in combination with an adenovirus encoding interleukin-12 genes (AdIL-12), elicited a potent antitumor effect and significantly prolonged animal survival (p < 0.05) in an orthotopic HCC model established in fibrotic livers. In assessing the presence of CSCs, we found reduced mRNA levels of CD133⁺, CD90⁺, EpCAM⁺, CD44⁺, and CD13⁺ CSC markers within HCC tumors (p < 0.01). Additionally, 4Mu downregulated the expression of the CSC marker CD47⁺ on HCC cells, promoted phagocytosis by antigen-presenting cells, and, combined with Ad-IL12, elicited a potent cytotoxic-specific T cell response. Finally, animal survival was increased when CD133^low HCC cells, generated upon 4Mu treatment, were injected in a metastatic HCC model. In conclusion, the combined strategy ameliorates HCC aggressiveness by targeting CSCs and as a result of the induction of anticancer immunity.

Poly(ethylene glycol)-poly(lysine) block copolymer-ubenimex conjugate targets aminopeptidase N and exerts an antitumor effect in hepatocellular carcinoma stem cells

Previous studies highlighted that aminopeptidase N (APN)/CD13 acts as a scavenger in the survival of hepatocellular carcinoma (HCC) stem cells by reducing reactive oxygen species (ROS) levels. Hence, it has been proposed that APN/CD13 inhibition can increase cellular ROS levels and sensitize cells to chemotherapeutic agents. Although ubenimex, also known as bestatin, competitively inhibits proteases such as APN/CD13 on the cellular membrane and it is clinically used for patients with acute myeloid leukemia and lymphedema, research has demonstrated that higher concentrations of the agent induce the death of APN/CD13⁺ HCC stem cells. In this study, we developed a poly(ethylene glycol)-poly(lysine) block copolymer-ubenimex conjugate (PEG-b-PLys(Ube)) to increase the efficacy of reagents in APN/CD13⁺ cancer stem cells. Exposure to PEG-b-PLys(Ube) increased the intracellular ROS concentration by inhibiting APN enzyme activity, permitting the induction of apoptosis and attenuation of HCC cell proliferation. In addition, PEG-b-PLys(Ube) exhibited a relatively stronger antitumor effect in mice than PEG-b-PLys alone or phosphate-buffered saline. Moreover, an isobologram analysis revealed that combinations of fluorouracil, cisplatin, or doxorubicin with PEG-b-PLys(Ube) exhibited synergistic effects. This study demonstrated that PEG-b-PLys(Ube) does not impair the properties of ubenimex and exerts a potent antitumor effect.

A metabolic interplay coordinated by HLX regulates myeloid differentiation and AML through partly overlapping pathways

The H2.0-like homeobox transcription factor (HLX) regulates hematopoietic differentiation and is overexpressed in Acute Myeloid Leukemia (AML), but the mechanisms underlying these functions remain unclear. We demonstrate here that HLX overexpression leads to a myeloid differentiation block both in zebrafish and human hematopoietic stem and progenitor cells (HSPCs). We show that HLX overexpression leads to downregulation of genes encoding electron transport chain (ETC) components and upregulation of PPARδ gene expression in zebrafish and human HSPCs. HLX overexpression also results in AMPK activation. Pharmacological modulation of PPARδ signaling relieves the HLX-induced myeloid differentiation block and rescues HSPC loss upon HLX knockdown but it has no effect on AML cell lines. In contrast, AMPK inhibition results in reduced viability of AML cell lines, but minimally affects myeloid progenitors. This newly described role of HLX in regulating the metabolic state of hematopoietic cells may have important therapeutic implications.

HLX transcription factor regulates haematopoietic stem and progenitor cell (HSPC) differentiation and is overexpressed in acute myeloid leukemia. Here the authors show that HLX overexpression leads to myeloid differentiation block in zebrafish and human HSPCs by direct regulation of metabolic pathways.

Pituitary adenomas, stem cells, and cancer stem cells: what's new?

PURPOSE

To clarify the existence of pituitary stem cells (SCs) both in the embryonic and the postnatal gland and the role for SCs in pituitary adenomas.

METHODS

This work, which does not address the pathogenesis of pituitary adenomas, reviews the latest research findings and discoveries on SCs in pituitary and cancer SCs (CSCs) in pituitary adenomas and discusses the involvement of the EMT.

RESULTS

Several groups using different approaches and techniques have demonstrated the existence of SCs and CSCs and as they are major players in pituitary adenoma onset.

CONCLUSIONS

As in other benign and malignant tumors, the hypothesis that CSCs play a pivotal role in pituitary adenoma onset has been confirmed as well as the existence of a link between the epithelial-to-mesenchymal transition (EMT) process and CSC formation in epithelial tumors.

IL-1β promotes the nuclear translocaiton of S100A4 protein in gastric cancer cells MGC803 and the cell's stem-like properties through PI3K pathway

It has been shown that nuclear expression of S100A4 is significantly correlated with increased metastasis and reduced survival in patients with gastric cancer and many other cancers. However, the factors which could influence the nuclear contents of S100A4 in cancer cells are not clear. It has also been reported that Interleukin-1β (IL-1β) promotes the nuclear translocation of S100A4 in chondrocytes. Previous studies have shown that IL-1β promotes the stemness of colon cancer cells, and S100A4 is also involved in maintaining cancer-initiating cells in head and neck cancers. We speculate that IL-1β might promote the nuclear translocation of S100A4 protein in MGC803 gastric cancer cells and therefore enhance their stem-like properties. The results from Western-blot and qRT-PCR analysis showed that IL-1β increased the nuclear and total cellular content of S100A4 protein and S100A4 mRNA level in MGC803 cells. LY294002, a pharmacological inhibitor of Phosphoinositide 3-kinase (PI3K) reversed the above effects. Functional studies indicated that IL-1β promoted the colony-forming and spheroid-forming capabilities of the cells and the expression of SOX2 and NANOG gene. PI3K or S100A4 inhibition reversed the IL-1β-mediated increase in colony and spheroid-forming capabilities of the cells. LY294002 also reversed the elevated SOX2 and NANOG expression induced by IL-1β. Our study demonstrated that IL-1β promote the nuclear translocation of S100A4 protein in gastric cancer cells MGC803, which are PI3K dependent, suggesting the existence of IL-1β-PI3K-S100A4 pathway for the first time. The study also showed that IL-1β promoted stem-like properties of the cells through the new pathway.

CHD4 mutations promote endometrial cancer stemness by activating TGF-beta signaling

Endometrial cancer is one of the most common cancers of the female reproductive system. CHD4, a core subunit of the nucleosome remodeling and deacetylation (NuRD) complex, is frequently mutated in these patients. However the role it plays in promoting endometrial tumorigenesis is poorly understood. Here, we use genetic engineering approaches to modulate CHD4 expression levels and functionally evaluate hot spot mutations R975H and R1162W. We find that CHD4 depletion induces up-regulation of the cancer stem cell (CSC) marker CD133. This CSC phenotype was verified functionally by invasion ability, spheroid formation, and tumorigenicity in vivo. While cells expressing mutated CHD4 did not display impaired CHD4 DNA recruitment or NuRD complex formation, the mutations did reduce the stability of CHD4 protein to phenocopy CHD4 depletion. Consistently, patients with mutant CHD4 showed overexpression of CD133. Network analysis indicated activation of the TGFβ signaling pathway may drive this CSC phenotype, and chemical blockade of TGFβ abrogated the ability CHD4 knockdown cells to form spheroids. Taken together, these results indicate that mutations in CHD4 can promote endometrial tumorigenesis by increasing CSC character through TGFβ signaling pathway.

Comparative aspects of microRNA expression in canine and human cancers

MicroRNAs (miRNAs) have important roles in all biological pathways in multicellular organisms. Over 1,400 human miRNAs have been identified, and many are conserved among vertebrates and invertebrates. Regulation of miRNA is the most common mode of post-transcriptional gene regulation. The miRNAs that are involved in the initiation and progression of cancers are termed oncomiRs and several of them have been identified in canine and human cancers. Similarly, several miRNAs have been reported to be down-regulated in cancers of the two species. In this review, current information on the expression and roles of miRNAs in oncogenesis and progression of human and canine cancers, as well the roles miRNAs have in cancer stem cell biology, are highlighted. The potential for the use of miRNAs as therapeutic targets in personalized cancer therapy in domestic dogs and their possible application in human cancer counterparts are also discussed.

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, p_corr=0.032; CT vs. CC: OR=1.29, p=0.015, p_corr=0.047; TT vs. CC: OR=1.77, p=<0.000, p_corr=0.018; CT+TT vs. CC: OR=1.34, p=<0.009, p_corr=0.041) and rs187115 (GG vs. AA: OR=2.34, p=<0.000, p_corr=0.025; AG vs. AA: OR=1.59, p=<0.000, p_corr=0.038; G vs. A allele OR=1.56, p=0.000, p_corr=0.05; AG+GG vs. AA: OR=1.63, p=<0.000, p_corr=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, p_corr=0.04; AG vs. GG: OR=0.85, p=<0.017, p_corr=0.01; AG+AA vs. GG: OR=0.86, p=<0.020, p_corr=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 (CSCs), cervical CSCs and targeted therapies

Accumulating evidence has shown that cancer stem cells (CSCs) have a tumour-initiating capacity and play crucial roles in tumour metastasis, relapse and chemo/radio-resistance. As tumour propagation initiators, CSCs are considered to be promising targets for obtaining a better therapeutic outcome. Cervical carcinoma is the most common gynaecological malignancy and has a high cancer mortality rate among females. As a result, the investigation of cervical cancer stem cells (CCSCs) is of great value. However, the numbers of cancer cells and corresponding CSCs in malignancy are dynamically balanced, and CSCs may reside in the CSC niche, about which little is known to date. Therefore, due to their complicated molecular phenotypes and biological behaviours, it remains challenging to obtain “purified” CSCs and continuously culture CSCs for further in vitro studies without the cells losing their stem properties. At present, CSC-related markers and functional assays are used to purify, identify and therapeutically target CSCs both in vitro and in vivo. Nevertheless, CSC-related markers are not universal to all tumour types, although some markers may be valid in multiple tumour types. Additionally, functional identifications based on CSC-specific properties are usually limited in in vivo studies. Furthermore, an optimal method for identifying potential CCSCs in CCSC studies has not been previously published, and these techniques are currently of great importance. This article updates our knowledge on CSCs and CCSCs, reviews potential stem cell markers and functional assays for identifying CCSCs, and describes the potential of targeting CCSCs in the treatment of cervical carcinoma.

Current perspectives on the crosstalk between lung cancer stem cells and cancer-associated fibroblasts

Lung cancer, in particular non-small cell lung carcinoma (NSCLC), is the second most common cancer in both men and women and the leading cause of cancer-related deaths worldwide. Its prognosis and diagnosis are determined by several driver mutations and diverse risk factors (e.g. smoking). While immunotherapy has proven effective in some patients, treatment of NSCLC using conventional chemotherapy is largely ineffective. The latter is believed to be due to the existence of a subpopulation of stem-like, highly tumorigenic and chemoresistant cells within the tumor population known as cancer stem cells (CSC). To complicate the situation, CSCs interact with the tumor microenvironment, which include cancer-associated fibroblasts (CAFs), immune cells, endothelial cells, growth factors, cytokines and connective tissue components, which via a dynamic crosstalk, composed of proteins and exosomes, activates the CSC compartment. In this review, we analyze the crosstalk between CSCs and CAFs, the primary component of the NSCLC microenvironment, at the molecular and extracellular level and contemplate therapies to disrupt this communication.

Loss of insulin-like growth factor II imprinting is a hallmark associated with enhanced chemo/radiotherapy resistance in cancer stem cells

Insulin-like growth factor II (IGF2) is maternally imprinted in most tissues, but the epigenetic regulation of the gene in cancer stem cells (CSCs) has not been defined. To study the epigenetic mechanisms underlying self-renewal, we isolated CSCs and non-CSCs from colon cancer (HT29, HRT18, HCT116), hepatoma (Hep3B), breast cancer (MCF7) and prostate cancer (ASPC) cell lines. In HT29 and HRT18 cells that show loss of IGF2 imprinting (LOI), IGF2 was biallelically expressed in the isolated CSCs. Surprisingly, we also found loss of IGF2 imprinting in CSCs derived from cell lines HCT116 and ASPC that overall demonstrate maintenance of IGF2 imprinting. Using chromatin conformation capture (3C), we found that intrachromosomal looping between the IGF2 promoters and the imprinting control region (ICR) was abrogated in CSCs, in parallel with loss of IGF2 imprinting in these CSCs. Loss of imprinting led to increased IGF2 expression in CSCs, which have a higher rate of colony formation and greater resistance to chemotherapy and radiotherapy in vitro. These studies demonstrate that IGF2 LOI is a common feature in CSCs, even when the stem cells are derived from a cell line in which the general population of cells maintain IGF2 imprinting. This finding suggests that aberrant IGF2 imprinting may be an intrinsic epigenetic control mechanism that enhances stemness, self-renewal and chemo/radiotherapy resistance in cancer stem cells.

Cancer Stem Cell-Suppressing Activity of Chrysotoxine, a Bibenzyl from Dendrobium pulchellum

Cancer stem cells (CSCs) have been recognized as rare populations driving cancer progression, metastasis, and drug resistance in leading cancers. Attempts have been made toward identifying compounds that specifically target these CSCs. Therefore, investigations of novel therapeutic strategies for CSC targeting are required. The cytotoxic effects of chrysotoxine on human non-small cell lung cancer-derived H460 and H23 cells were evaluated by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. The effects of chrysotoxine suppression of CSC-like phenotypes were determined in CSC-rich populations and primary CSCs in three-dimensional (3D) culture and in an extreme limiting dilution assay. Expression of CSC markers and associated proteins was determined by Western blot analyse and flow cytometry. We have reported herein the CSC-suppressing activity of chrysotoxine, a bibenzyl compound isolated from Dendrobium pulchellum We have shown, to our knowledge for the first time, that chrysotoxine dramatically suppresses CSC-like phenotypes of H460 and H23 cells. Treatment with chrysotoxine significantly reduced the viability of 3D CSC-rich populations and concomitantly decreased known CSC markers. Chrysotoxine suppressed CSC phenotypes through downregulation of Src/protein kinase B (Akt) signaling. Active (phosphorylated Y416) Src was shown to regulate cancer stemness, since ectopic overexpression of Src strongly activated Akt and subsequently enhanced pluripotency transcription factor SRY (sex-determining region Y)-box 2 (Sox2)- mediating CSC phenotypes, whereas the short hairpin RNA of Src and an Src inhibitor (dasatinib) suppressed Akt, Sox2, and CSC properties. Importantly, chrysotoxine was shown to suppress active Src/Akt signaling and in turn depleted Sox2-mediated CSCs. Our findings indicate a novel CSC-targeted role of chrysotoxine and its regulation by Src/Akt and Sox2, which may be exploited for cancer treatment.

A2B adenosine receptor agonist induces cell cycle arrest and apoptosis in breast cancer stem cells via ERK1/2 phosphorylation

PURPOSE

It has been reported that cancer stem cells (CSCs) may play a crucial role in the development, recurrence and metastasis of breast cancer. Targeting signaling pathways in CSCs is considered to be a promising strategy for the treatment of cancer. Here, we investigated the role of the A2B adenosine receptor (A2BAR) and its associated signaling pathways in governing the proliferation and viability of breast cancer cell line derived CSCs.

METHODS

CSCs were isolated from the breast cancer cell lines MCF-7 and MDA-MB-231 using a mammosphere assay. The effect of the A2BAR agonist BAY606583 on cell proliferation was evaluated using XTT and mammosphere formation assays, respectively. Apoptosis was assessed using Annexin-V staining and cell cycle analyses were performed using flow cytometry. The expression levels of Bax, Bcl-2, cyclin-D1, CDK-4 and (phosphorylated) ERK1/2 were assessed using Western blotting.

RESULTS

Our data revealed that the breast cancer cell line derived mammospheres were enriched for CSCs. We also found that A2BAR stimulation with its agonist BAY606583 inhibited mammosphere formation and CSC viability. In addition, we found that the application of BAY606583 led to CSC cell cycle arrest and apoptosis through the cyclin-D1/Cdk-4 and Bax/Bcl-2 pathways, respectively. Notably, we found that BAY606583 significantly down-regulated ERK1/2 phosphorylation in the breast cancer cell line derived CSCs.

CONCLUSIONS

From our results we conclude that A2BAR induces breast CSC cell cycle arrest and apoptosis through downregulation of the ERK1/2 cascade. As such, A2BAR may be considered as a novel target for the treatment of breast cancer.