Expansion of cancer stem cell pool initiates lung cancer recurrence before angiogenesis

The role of liver cancer stem cells in hepatocellular carcinoma metastasis

Metastasis accounts for the vast majority of cancer deaths; however, this complex process has yet to be fully explained. To form metastases, cancer cells must undergo a series of steps, known as the "Metastatic cascade", each of which requires a specific functional transformation. Cancer stem cells (CSCs) play a vital role in tumor metastasis, but their dynamic behavior and regulatory mechanisms have not been fully elucidated. Based on the "Metastatic cascade" theory, this review summarizes the effect of liver CSCs on the metastatic biological programs that underlie the dissemination and metastatic growth of cancer cells. Liver CSCs have the capacity to initiate distant organ metastasis via EMT, and the microenvironment transformation that supports the ability of these cells to disseminate, evade immune surveillance, dormancy, and regenerate metastasis. Understanding the heterogeneity and traits of liver CSCs in these processes is critical for developing strategies to prevent and treat metastasis of advanced hepatocellular carcinoma (HCC).

Adrenergic microenvironment driven by cancer-associated Schwann cells contributes to chemoresistance in patients with lung cancer

Doublecortin (DCX)-positive neural progenitor-like cells are purported components of the cancer microenvironment. The number of DCX-positive cells in tissues reportedly correlates with cancer progression; however, little is known about the mechanism by which these cells affect cancer progression. Here we demonstrated that DCX-positive cells, which are found in all major histological subtypes of lung cancer, are cancer-associated Schwann cells (CAS) and contribute to the chemoresistance of lung cancer cells by establishing an adrenergic microenvironment. Mechanistically, the activation of the Hippo transducer YAP/TAZ was involved in the acquisition of new traits of CAS and DCX positivity. We further revealed that CAS express catecholamine-synthesizing enzymes and synthesize adrenaline, which potentiates the chemoresistance of lung cancer cells through the activation of YAP/TAZ. Our findings shed light on CAS, which drive the formation of an adrenergic microenvironment by the reciprocal regulation of YAP/TAZ in lung cancer tissues.

The role of IGF/IGF-1R signaling in the regulation of cancer stem cells

Cancer stem cells (CSCs) are a group of tumor cells with high tumorigenic ability and self-renewal potential similar to those of normal stem cells. CSCs are the key "seeds" for tumor development, metastasis, and recurrence. A better insight into the key mechanisms underlying CSC survival improves the efficiency of cancer therapy via specific targeting of CSCs. Insulin-like growth factor (IGF)/IGF-1 receptor (IGF-1R) signaling plays an important role in the maintenance of cancer stemness. However, the effect of IGF/IGF-1R signaling on stemness and CSCs and the underlying mechanisms are still controversial. Based on the similarity between CSCs and normal stem cells, this review discusses emerging data on the functions of IGF/IGF-1R signaling in normal stem cells and CSCs and dissects the underlying mechanisms by which IGF/IGF-1R signaling is involved in CSCs. On the other hand, this review highlighted the role of IGF/IGF-1R signaling blockade in multiple CSCs as a potential strategy to improve CSC-based therapy.

Esophageal cancer stem cells reduce hypoxia-induced apoptosis by inhibiting the GRP78-perk-eIF2α-ATF4-CHOP pathway in vitro

Background

Due to the abnormal angiogenesis, cancer stem cells (CSCs) in esophageal cancer (EC) have the characteristics of a hypoxic microenvironment. However, they can resist hypoxia-induced apoptosis. the molecular mechanism underlying the resistance of esophageal CSCs to hypoxia-induced apoptosis is currently unclear. Therefore, this study will investigate the molecular mechanism based on CHOP-mediated endoplasmic reticulum stress.

Methods

CD44+CD24- cells in EC9706 cells were screened by fluorescence-activated cell sorting (FACS). To clarify which apoptosis pathway esophageal CSCs resist hypoxia-induced cell apoptosis through, the effects of hypoxia on apoptosis were detected by nuclear staining, flow cytometry, and JC-1 reagent, the effects of hypoxia on the expression of apoptosis-related proteins were detected by western blotting (WB) assay and quantitative polymerase chain reaction (qPCR) assay. To clarify the mechanisms of CD44+CD24- cells resistance to hypoxia-induced apoptosis is achieved by inhibiting the activation of endoplasmic reticulum stress (ERS) pathway, silenced CHOP and PERK cell lines of EC9706 cells and overexpressed CHOP and PERK cell lines of CD44+CD24- cells were constructed, the effects of hypoxia on apoptosis, cell cycle, and mitochondrial membrane potential were detected by flow cytometry and JC-1 reagent. WB assay and qPCR assay were used to detect the expressions of apoptosis-related proteins and ERS-related proteins.

Results

Hypoxia significantly induce apoptosis and cycle arrest of EC9706 cells (P<0.05), but did not affect apoptosis and cycle of CD44+CD24- cells (P>0.05). Hypoxia considerably induced the activation of mitochondrial and ERS apoptosis pathways in EC9706 cells (P<0.05), but did not affect Fas receptor apoptosis pathways (P>0.05). The three apoptosis pathways were not affected by hypoxia in CD44+CD24- cells (P>0.05). Silencing the CHOP and PERK gene inhibited hypoxia-induced apoptosis of EC9706 cells (P<0.05). CHOP and PERK overexpression promoted hypoxia-induced apoptosis of CD44+CD24- cells (P<0.05), whereas mitochondrial membrane permeability inhibitors inhibited hypoxia-induced apoptosis of CD44+CD24- cells overexpressed CHOP gene.

Conclusions

CD44+CD24- tumor stem cells in EC resist to hypoxia-induced apoptosis by the inhibition of ERS-mediated mitochondrial apoptosis pathway, which suggested that ERS pathway can serve as a potential target for reducing EC treatment resistance in clinical treatment.

Recent advancements to engineer mesenchymal stem cells and their extracellular vesicles for targeting and destroying tumors

Mesenchymal stem cells (MSCs) have the ability to migrate into tumor sites and release growth factors to modulate the tumor microenvironment. MSC therapy have shown a dual role in cancers, promoting or inhibiting. However, MSCs could be used as a carrier of anticancer agents for targeted tumor therapy. Recent technical improvements also allow engineering MSCs to improve tumor-targeting properties, protect anticancer agents, and decrease the cytotoxicity of drugs. While some of MSC functions are mediated through their secretome, MSCs-derived extracellular vesicles (EVs) are also proposed as a possible viechle for cancer therapy. EVs allow efficient loading of anticancer agents and have an intrinsic ability to target tumor cells, making them suitable for targeted therapy of tumors. In addition, the specificity and selectivity of EVs to the tumor sites could be enhanced by surface modification. In this review, we addressed the current approaches used for engineering MSCs and EVs to effectively target tumor sites and deliver anticancer agents.

HN1L/AP-2γ/PLK1 signaling drives tumor progression and chemotherapy resistance in esophageal squamous cell carcinoma

Hematological and neurological expressed 1 like (HN1L) is a newly identified oncogene in lung cancer and hepatocellular carcinoma recently identified by our team, but its roles in the development and treatment of esophageal squamous cell carcinoma (ESCC) remain incompletely cataloged. Here, using ESCC tissue array and public database analysis, we demonstrated that HN1L was highly expressed in ESCC tissues, which was associated with tumor tissue invasion, poor clinical stage and short survival for ESCC patients. Loss- and gain-of-function studies in ESCC cells revealed that HN1L enhances ESCC cell metastasis and proliferation in vitro and in mice models. Moreover, high level of HN1L reduces the sensibility of ESCC cells to chemotherapeutic drugs, such as Docetaxel. Mechanism studies revealed that HN1L activated the transcription of polo-like kinase 1 (PLK1) by interacting with transcription factor AP-2γ, which increased the expression of malignancy related proteins Cyclin D1 and Slug in ESCC cells. Blocking PLK1 with inhibitor BI-2356 abrogated the oncogenic function of HN1L and significantly suppressed ESCC progression by combining with chemotherapy. Therefore, this study demonstrates the vital pro-tumor role of HN1L/AP-2γ/PLK1 signaling axis in ESCC, offering a potential therapeutic strategy for ESCC patients with high HN1L by blocking PLK1.

Tumor-associated macrophages promote resistance of hepatocellular carcinoma cells against sorafenib by activating CXCR2 signaling

BACKGROUND

Sorafenib (SOR) is the first line treatment for advanced hepatocellular carcinoma (HCC), but resistance develops frequently. Tumor-associated macrophages (TAMs) have been reported to affect the progression of HCC. We therefore aimed to study the role of TAMs in promoting SOR resistance.

METHODS

Immunofluorescence staining for the M2 marker CD204 and the cancer stem cell (CSC) markers CD44 and CD133 was performed in paired HCC and adjacent noncancerous tissues and HCC tissues stratified by response of SOR treatment. HCC/U937 coculture system and cytokines were used to induce M2 polarization for studying the effects of M2 TAMs on CSC properties and apoptotic death of HCC cells after SOR treatment.

RESULTS

Higher expression of CD204, CD44, and CD133 was observed in patients with SOR nonresponse (SNR) than in those with SOR response (SR), suggesting that SNR is positively correlated to levels of CSCs and M2 TAMs. After coculture, M2 TAMs could increase the level of CSCs but decrease SOR-induced apoptosis. Incubation of HCC cells with coculture conditioned medium increased the formation of spheres that were resistant to SOR. Furthermore, CXCL1 and CXCL2 were found to be the potential paracrine factors released by M2 TAMs to upregulate SOR resistance in HCC cells. Treatment with CXCL1 and CXCL2 could increase HCC CSC activity but decrease SOR-induced apoptosis by affecting BCL-2 family gene expression. Using pharmacological inhibitors, CXCR2/ERK signaling was found to be critical to CXCL1- and CXCL2-mediated SOR resistance.

CONCLUSION

This study identified CXCL1, CXCL2, and their downstream CXCR2/ERK signaling as potential therapeutic targets to overcome SOR resistance in HCC.

Dissecting Tumor Growth: The Role of Cancer Stem Cells in Drug Resistance and Recurrence

Simple Summary

Cancer is one of the most debated problems all over the world. Cancer stem cells are considered responsible of tumor initiation, metastasis, drug resistance, and recurrence. This subpopulation of cells has been found into the tumor bulk and showed the capacity to self-renew, differentiate, up to generate a new tumor. In the last decades, several studies have been set on the molecular mechanisms behind their specific characteristics as the Wnt/β-catenin signaling, Notch signaling, Hedgehog signaling, transcription factors, etc. The most powerful part of CSCs is represented by the niches as “promoter” of their self-renewal and “protector” from the common oncological treatment as chemotherapy and radiotherapy. In our review article we highlighted the primary mechanisms involved in CSC tumorigenesis for the setting of further targets to control the metastatic process.

Abstract

Emerging evidence suggests that a small subpopulation of cancer stem cells (CSCs) is responsible for initiation, progression, and metastasis cascade in tumors. CSCs share characteristics with normal stem cells, i.e., self-renewal and differentiation potential, suggesting that they can drive cancer progression. Consequently, targeting CSCs to prevent tumor growth or regrowth might offer a chance to lead the fight against cancer. CSCs create their niche, a specific area within tissue with a unique microenvironment that sustains their vital functions. Interactions between CSCs and their niches play a critical role in regulating CSCs’ self-renewal and tumorigenesis. Differences observed in the frequency of CSCs, due to the phenotypic plasticity of many cancer cells, remain a challenge in cancer therapeutics, since CSCs can modulate their transcriptional activities into a more stem-like state to protect themselves from destruction. This plasticity represents an essential step for future therapeutic approaches. Regarding self-renewal, CSCs are modulated by the same molecular pathways found in normal stem cells, such as Wnt/β-catenin signaling, Notch signaling, and Hedgehog signaling. Another key characteristic of CSCs is their resistance to standard chemotherapy and radiotherapy treatments, due to their capacity to rest in a quiescent state. This review will analyze the primary mechanisms involved in CSC tumorigenesis, with particular attention to the roles of CSCs in tumor progression in benign and malignant diseases; and will examine future perspectives on the identification of new markers to better control tumorigenesis, as well as dissecting the metastasis process.

Mesenchymal stem/stromal cells in cancer therapy

The multipotent mesenchymal stem/stromal cells (MSCs), initially discovered from bone marrow in 1976, have been identified in nearly all tissues of human body now. The multipotency of MSCs allows them to give rise to osteocytes, chondrocytes, adipocytes, and other lineages. Moreover, armed with the immunomodulation capacity and tumor-homing property, MSCs are of special relevance for cell-based therapies in the treatment of cancer. However, hampered by lack of knowledge about the controversial roles that MSC plays in the crosstalk with tumors, limited progress has been made with regard to translational medicine. Therefore, in this review, we discuss the prospects of MSC-associated anticancer strategies in light of therapeutic mechanisms and signal transduction pathways. In addition, the clinical trials designed to appraise the efficacy and safety of MSC-based anticancer therapies will be assessed according to published data.

Insuline-Like Growth Factor-2 (IGF2) and Hepatocyte Growth Factor (HGF) Promote Lymphomagenesis in p53-null Mice in Tissue-specific and Estrogen-signaling Dependent Manners

Background: Trp53^-/- mice are prone to develop lymphomas at old ages. Factors promoting this tumorigenesis are unknown. Here, we showed human ovulatory follicular fluid (FF) largely promotes lymphomagenesis in Trp53^-/- mice at earlier ages. Meanwhile, we clarified that IGF2 and HGF are important cell transforming factors within FF. Methods: To induce tumor formation, 5% FFs, 100 ng/ml IGF2, 20 ng/ml HGF, or both IGF2 and HGF in a volume of 200 µl PBS, was injected into 8-wk-old female Trp53 ^-/- mice at the mammary fat pad. The injection was repeated weekly for up to 7 weeks or extending to 13 weeks to observe the accumulative incidence of lymphomagenesis. Immunohistochemistry staining and gene rearrangement analysis were used to identify the tumor type. Results: By injecting FF into the mammary fat pad weekly, lymphomas developed in 8/16 (50%) of mice by seven weeks. We identified IGF2 and HGF in FF is largely responsible for this activity. The same weekly injection of IGF2, HGF, and their combination induced lymphomas in 4/11 (36%), 3/8 (38%), and 6/9 (67%) mice, respectively. Interestingly, tumorigenesis was induced only when those were injected into the adipose tissues in the mammary gland, but not when injected into non-adipose sites. We also found this tumor-promoting activity is estradiol (E2)-dependent and relies on estrogen receptor (ER) α expression in the adipose stroma. No tumor or only tiny tumor was yielded when the ovaries were resected or when ER is antagonized. Finally, an extension of the weekly FF-injection to 13 weeks did not further increase the lymphomagenesis rate, suggesting an effect on pre-initiated cancer cells. Conclusions: Taken together, the study disclosed a robust tumor-promoting effect of IGF2 and HGF in the p53 loss-initiated lymphomagenesis depending on an adipose microenvironment in the presence of E2. In light of the clarity of this spontaneous tumor promotion model, we provide a new tool for studying p53-mediated lymphomagenesis and suggest that, as a chemoprevention test, this is a practical model to perform.

Ternary supramolecular nanocomplexes for superior anticancer efficacy of natural medicines

The discovery of effective anticancer drug delivery systems and elucidation of the mechanism are enormous challenges. Using two drug administration-approved biomaterials, we constructed a natural medicine (NM)-loaded ternary supramolecular nanocomplex (TSN) suitable for large-scale production. The TSN has a better effect against cancer cells/stem cells than NM with differentially upregulated (27 versus 59) and downregulated (165 versus 66) proteins, respectively. Treatment with the TSN induced apoptosis and G2/M arrest, inhibited cell proliferation, metastasis and invasion, reduced colony/sphere formation, and decreased the frequency of side population cells and CD133⁺CD44⁺ABCG2⁺ cells. These results were revealed by multiple analyses (proteomic analysis, transwell migration and colony/sphere formation assays, biomarker profiling, etc.). We first reported the proteomic analysis of small lung cancer cells responding to a drug or its nanovesicles. We first conducted a proteomic evaluation of tumor cells responding to a drug supramolecular nanosystem. The supramolecular conformation of the TSN and the interactions of the TSN with albumin were verified by molecular docking experiments. The dominant binding forces in the TSN complexation process were electrostatic interactions, van der Waalsinteractions and bond stretching. The TSN binds to albumin more readily than NM does. The TSN has good in situ absorptive and in vitro/vivo kinetic properties. The relative bioavailability of the TSN to EA was 458.39%. The NM-loaded TSN is a supramolecular vesicle that can be produced at an industrial scale for efficient cancer therapy.

Integrated bioinformatics analysis revealed the regulation of angiogenesis by tumor cells in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is one of the leading causes of cancer mortality, metastasis accounts for most of the cases. Angiogenesis plays an important role in cancer metastasis, but how tumor cells affect the function of endothelial cells by dictating their microRNA (miRNA) expression remains largely unknown.

Differentially expressed miRNAs (DEMs) were identified through dataset downloaded from the Gene Expression Omnibus (GEO) database and analyzed by GEO2R. We then used online tools to obtain potential targets of candidate miRNAs and functional enrichment analysis, as well as the protein-protein interaction (PPI). Finally, the function of miR-302c-3p was validated through in vitro assay.

In the current study, we found that HCC cells altered miRNA expression profiles of human umbilical vein endothelial cells (HUVECs) and miR-302c-3p was the most down-regulated miRNA in HUVECs when they were co-cultured with HCC-LM3 cells. Functional enrichment analysis of the candidate targets revealed that these genes were involved in epigenetic regulation of gene expression, in particular, cytosine methylation. In addition, PPI network demonstrated distinct roles of genes targeted by miR-302c-3p. Importantly, inhibition of angiogenesis, migration and permeability by the most down-regulated miR-302c-3p in HUVECs was confirmed in vitro. These findings brought us novel insight into the regulation of angiogenesis by HCC cells and provided potential targets for the development of therapeutic strategies.

Regulation of angiogenesis by microRNAs in cancer

MicroRNAs (miRs) are endogenous, small, non‑coding RNA molecules with ~22 nucleotides, and are involved in regulating the expression of multiple genes and controlling cellular functions. miRs serve key roles in angiogenesis by regulating the proliferation, differentiation, apoptosis and migration of endothelial cells. Regulation of angiogenesis is essential for several physiological and pathological processes, particularly for tumor development and progression. Therefore, it is important to investigate the roles served by miRs in angiogenesis as this may aid in discovering novel strategies for treating tumors via modulating angiogenesis. In this review, miRNA biogenesis, regulation and functions are described with new information and corresponding references. In particular, the latest advances in the role of various miRs and their target genes involved in tumor angiogenesis were updated. Next, different signaling pathways by which miRNAs could be regulated in different types of tumor progression were addressed. Furthermore, the potential clinical value of miRs as biomarkers for diagnosing and monitoring the response to therapy, as well as their ability to regulate tumor angiogenesis and the mechanism underlying this regulation, were investigated.

Anlotinib exerts anti-cancer efficiency on lung cancer stem cells in vitro and in vivo through reducing NF-κB activity

Anlotinib is a multi-target tyrosine kinase inhibitor. Previous studies confirmed that anlotinib exerts anti-cancer efficiency. However, the functional roles of anlotinib on cancer stem cells (CSCs) are yet to be elucidated. In this study, lung CSCs were isolated and identified in vitro, and mouse xenografts were established in vivo. MTT assays, tumour sphere formation assays, TdT-mediated dUTP nick-end labelling (TUNEL) staining, Annexin V-FITC/PI staining, immunofluorescence analysis and Western blot were performed to investigate the anti-cancer effects of anlotinib on lung CSCs. The results showed that anlotinib inhibits the growth of lung CSCs in vitro and in vivo. In addition, anlotinib induced apoptosis of these cells along with down-regulated expression level of Bcl-2 whereas up-regulated Bax and cleaved caspase-3 expression. It also sensitized lung CSCs to the cytotoxicity of cisplatin and paclitaxel; the tumour sphere formation and expression levels of multiple stemness-associated markers, such as ALDH1 and CD133, were also decreased. Furthermore, the underlying mechanism indicated that anlotinib reduces the phosphorylated levels of NF-κB p65 and IκB-α in lung CSCs. Taken together, these findings suggested that anlotinib exerts potent anti-cancer effects against lung CSCs through apoptotic induction and stemness phenotypic attenuation. The mechanism could be associated with the suppression of NF-κB activity.

Dual-triggered biomimetic vehicles enable treatment of glioblastoma through a cancer stem cell therapeutic strategy

Glioma stem cells (GSCs) and their complex microenvironment play a crucial role in the high invasion of cancer and therapeutic resistance and are considered to be the most likely cause of cancer relapse. We constructed a biomimetic vehicle (LDL-SAL-Ang) based on a low density lipoprotein triggered by Angiopep-2 peptide and ApoB protein, to improve the transport of an anti-GSC therapeutic agent into the brain. The LDL-SAL-Ang showed significant inhabitation for GSC microsphere formation and induced the highest apoptotic rate in two types of GSCs. LDL-SAL-Ang reduced the number of GSC-derived endothelial tubules at a lower drug concentration and inhibited endothelial cell migration and angiogenesis. The pharmacokinetic analysis showed that the brain tissue uptake rate (% ID g^-1) for LDL-SAL-Ang was significantly enhanced at 0.45. For anti-glioblastoma activity in vivo, the median survival time of LDL-SAL-Ang plus temozolomide group was 47 days, which were significantly increased compared with the control or temozolomide only groups. The endogenous biomimetic nanomedicine that we designed provides a potential approach to improve treatments for intracranial tumors and reduced neurotoxicity of nanomedicine.

A Zic2/Runx2/NOLC1 signaling axis mediates tumor growth and metastasis in clear cell renal cell carcinoma

Clear cell renal cell carcinoma (ccRCC) is one of the most common malignancies with rapid growth and high metastasis, but lacks effective therapeutic targets. Here, using public sequencing data analyses, quantitative real-time PCR assay, western blotting, and IHC staining, we characterized that runt-related transcription factor 2 (Runx2) was significantly upregulated in ccRCC tissues than that in normal renal tissues, which was associated with the worse survival of ccRCC patients. Overexpression of Runx2 promoted malignant proliferation and migration of ccRCC cells, and inversely, interfering Runx2 with siRNA attenuates its oncogenic ability. RNA sequencing and functional studies revealed that Runx2 enhanced ccRCC cell growth and metastasis via downregulation of tumor suppressor nucleolar and coiled-body phosphoprotein 1 (NOLC1). Moreover, increased Zic family member 2 (Zic2) was responsible for the upregulation of Runx2 and its oncogenic functions in ccRCC. Kaplan-Meier survival analyses indicated that ccRCC patients with high Zic2/Runx2 and low NOLC1 had the worst outcome. Therefore, our study demonstrates that Zic2/Runx2/NOLC1 signaling axis promotes ccRCC progression, providing a set of potential targets and prognostic indicators for patients with ccRCC.

Cancer stem cells and macrophages: molecular connections and future perspectives against cancer

Cancer stem cells (CSCs) have been considered the key drivers of cancer initiation and progression due to their unlimited self-renewal capacity and their ability to induce tumor formation. Macrophages, particularly tumor-associated macrophages (TAMs), establish a tumor microenvironment to protect and induce CSCs development and dissemination. Many studies in the past decade have been performed to understand the molecular mediators of CSCs and TAMs, and several studies have elucidated the complex crosstalk that occurs between these two cell types. The aim of this review is to define the complex crosstalk between these two cell types and to highlight potential future anti-cancer strategies.

Circulatory shear stress induces molecular changes and side population enrichment in primary tumor-derived lung cancer cells with higher metastatic potential

Cancer is a leading cause of death and disease worldwide. However, while the survival for patients with primary cancers is improving, the ability to prevent metastatic cancer has not. Once patients develop metastases, their prognosis is dismal. A critical step in metastasis is the transit of cancer cells in the circulatory system. In this hostile microenvironment, variations in pressure and flow can change cellular behavior. However, the effects that circulation has on cancer cells and the metastatic process remain unclear. To further understand this process, we engineered a closed-loop fluidic system to analyze molecular changes induced by variations in flow rate and pressure on primary tumor-derived lung adenocarcinoma cells. We found that cancer cells overexpress epithelial-to-mesenchymal transition markers TWIST1 and SNAI2, as well as stem-like marker CD44 (but not CD133, SOX2 and/or NANOG). Moreover, these cells display a fourfold increased percentage of side population cells and have an increased propensity for migration. In vivo, surviving circulatory cells lead to decreased survival in rodents. These results suggest that cancer cells that express a specific circulatory transition phenotype and are enriched in side population cells are able to survive prolonged circulatory stress and lead to increased metastatic disease and shorter survival.

Laminin γ2-mediating T cell exclusion attenuates response to anti-PD-1 therapy

PD-1/PD-L1 blockade therapies provide notable clinical benefits for patients with advanced cancers, but the factors influencing the effectiveness of the treatment remain incompletely cataloged. Here, the up-regulation of laminin γ2 (Ln-γ2) predicted the attenuated efficacy of anti-PD-1 drugs and was associated with unfavorable outcomes in patients with lung cancer or esophageal cancer. Furthermore, Ln-γ2 was transcriptionally activated by transforming growth factor-β1 (TGF-β1) secreted from cancer-associated fibroblasts via JNK/AP1 signaling, which blocked T cell infiltration into the tumor nests by altering the expression of T cell receptors. Coadministration of the TGF-β receptor inhibitor galunisertib and chemotherapy drugs provoked vigorous antitumor activity of anti-PD-1 therapy in mouse tumor models. Therefore, Ln-γ2 may represent a useful biomarker to optimize clinical decisions and predict the response of cancer patients to treatment with anti-PD-1 drugs.

TROAP switches DYRK1 activity to drive hepatocellular carcinoma progression

Hepatocellular carcinoma (HCC) is one of the common malignancy and lacks effective therapeutic targets. Here, we demonstrated that ectopic expression of trophinin-associated protein (TROAP) dramatically drove HCC cell growth assessed by foci formation in monolayer culture, colony formation in soft agar and orthotopic liver transplantation in nude mice. Inversely, silencing TROAP expression with short-hairpin RNA attenuated the malignant proliferation of HCC cells in vitro and in vivo. Next, mechanistic investigation revealed that TROAP directly bound to dual specificity tyrosine phosphorylation regulated kinase 1A/B (DYRK1A/B), resulting in the cytoplasmic retention of proteins DYRK1A/B and promoting cell cycle process via activation of Akt/GSK-3β signaling. Combination of cisplatin with an inhibitor of DYRK1 AZ191 effectively inhibited tumor growth in mouse model for HCC cells with high level of TROAP. Clinically, TROAP was significantly upregulated by miR-142-5p in HCC tissues, which predicted the poor survival of patients with HCC. Therefore, TROAP/DYRK1/Akt axis may be a promising therapeutic target and prognostic indicator for patients with HCC.

SNRPB-mediated RNA splicing drives tumor cell proliferation and stemness in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is one of the leading malignant diseases worldwide, but therapeutic targets for HCC are lacking. Here, we characterized a significant upregulation of Small Nuclear Ribonucleoprotein Polypeptides B and B1 (SNRPB) in HCC via qRT-PCR, western blotting, tissue microarray and public database analyses. Increased SNRPB expression was positively associated with adjacent organ invasion, tumor size, serum AFP level and poor HCC patient survival. Next, we transfected SNRPB into HCC cells to construct SNRPB-overexpressing cell lines, and short hairpin RNA targeting SNRPB was used to silence SNRPB in HCC cells. Functional studies showed that SNRPB overexpression could promote HCC cell malignant proliferation and stemness maintenance. Inversely, SNRPB knockdown in HCC cells caused inverse effects. Importantly, analysis of alternative splicing by RNA sequencing revealed that SNRPB promoted the formation of AKT3-204 and LDHA-220 splice variants, which activated the Akt pathway and aerobic glycolysis in HCC cells. In conclusion, SNRPB could serve as a prognostic predictor for patients with HCC, and it promotes HCC progression by inducing metabolic reprogramming.

Effects of IGF-1 on Proliferation, Angiogenesis, Tumor Stem Cell Populations and Activation of AKT and Hedgehog Pathways in Oral Squamous Cell Carcinoma

(1) Background: Activation of the PI3K-AKT pathway controls most hallmarks of cancer, and the hedgehog (HH) pathway has been associated with oral squamous cell carcinoma (OSCC) development and progression. We hypothesized that fibroblast-derived insulin-like growth factor-1 (IGF-1) acts in oral squamous cell carcinoma (OSCC) cells, leading to the non-canonical activation of the HH pathway, maintaining AKT activity and promoting tumor aggressiveness. (2) Methods: Primary fibroblasts (MF1) were genetically engineered for IGF-1 overexpression (MF1-IGF1) and CRISPR/Cas9-mediated IGF1R silencing was performed in SCC-4 cells. SCC-4 cells were co-cultured with fibroblasts or incubated with fibroblast conditioned medium (CM) or rIGF-1 for functional assays and the evaluation of AKT and HH pathways. (3) Results: Gene expression analysis confirmed IGF-1 overexpression in MF1-IGF1 and the absence of IGF-1 expression in SCC-4, while elevated IGF1R expression was detected. IGF1R silencing was associated with decreased survival of SCC-4 cells. Ihh was expressed in both MF1 and MF1-IGF1, and increased levels of GLI1 mRNA were observed in SCC-4 after stimulation with CM-MF1. Activation of both PI3K-AKT and the HH pathway (GLI1, Ihh and SMO) were identified in SCC-4 cells cultured in the presence of MF1-IGF1-CM. rIGF-1 promoted tumor cell proliferation, migration, invasion and tumorsphere formation, whereas CM-MF1 significantly stimulated angiogenesis. (4) Conclusions: IGF-1 exerts pro-tumorigenic effects by stimulating SCC-4 cell proliferation, migration, invasion and stemness. AKT and HH pathways were activated by IGF-1 in SCC-4, reinforcing its influence on the regulation of these signaling pathways.

Cancer Stem Cells-Origins and Biomarkers: Perspectives for Targeted Personalized Therapies

The use of biomarkers in diagnosis, therapy and prognosis has gained increasing interest over the last decades. In particular, the analysis of biomarkers in cancer patients within the pre- and post-therapeutic period is required to identify several types of cells, which carry a risk for a disease progression and subsequent post-therapeutic relapse. Cancer stem cells (CSCs) are a subpopulation of tumor cells that can drive tumor initiation and can cause relapses. At the time point of tumor initiation, CSCs originate from either differentiated cells or adult tissue resident stem cells. Due to their importance, several biomarkers that characterize CSCs have been identified and correlated to diagnosis, therapy and prognosis. However, CSCs have been shown to display a high plasticity, which changes their phenotypic and functional appearance. Such changes are induced by chemo- and radiotherapeutics as well as senescent tumor cells, which cause alterations in the tumor microenvironment. Induction of senescence causes tumor shrinkage by modulating an anti-tumorigenic environment in which tumor cells undergo growth arrest and immune cells are attracted. Besides these positive effects after therapy, senescence can also have negative effects displayed post-therapeutically. These unfavorable effects can directly promote cancer stemness by increasing CSC plasticity phenotypes, by activating stemness pathways in non-CSCs, as well as by promoting senescence escape and subsequent activation of stemness pathways. At the end, all these effects can lead to tumor relapse and metastasis. This review provides an overview of the most frequently used CSC markers and their implementation as biomarkers by focussing on deadliest solid (lung, stomach, liver, breast and colorectal cancers) and hematological (acute myeloid leukemia, chronic myeloid leukemia) cancers. Furthermore, it gives examples on how the CSC markers might be influenced by therapeutics, such as chemo- and radiotherapy, and the tumor microenvironment. It points out, that it is crucial to identify and monitor residual CSCs, senescent tumor cells, and the pro-tumorigenic senescence-associated secretory phenotype in a therapy follow-up using specific biomarkers. As a future perspective, a targeted immune-mediated strategy using chimeric antigen receptor based approaches for the removal of remaining chemotherapy-resistant cells as well as CSCs in a personalized therapeutic approach are discussed.

Cancer-associated fibroblasts-derived gamma-glutamyltransferase 5 promotes tumor growth and drug resistance in lung adenocarcinoma

Gamma-glutamyltransferase 5 (GGT5) is a member of the gamma-glutamyl transpeptidase gene family with the capacity of cleaving the gamma-glutamyl moiety of glutathione, but its role in cancer progression has never been revealed. In this study, we found that gene GGT5 was highly expressed in cancer-associated fibroblasts (CAFs) in lung adenocarcinoma, predicting the unfavorable survival of patients with lung adenocarcinoma. Cell growth, foci formation and spheres formation analyses showed that cancer cell proliferation was attenuated under treatment with the conditioned media from GGT5-silenced CAFs. Moreover, high expression of GGT5 in CAFs enhanced the drug resistance of cancer cells by increasing intracellular glutathione and reducing the intracellular reactive oxygen species in cancer cells. In mouse xenograft model, we proved that targeting GGT5 with a small-molecule inhibitor GGsTop could inhibit tumor growth and increase the chemosensitivity of cancer cells. Taken together, our study illuminates that high level of GGT5 in CAFs contributes to cancer cell survival and drug resistance, indicating that GGT5 may be a promising therapeutic target in lung adenocarcinoma.

Endothelial Progenitors in the Tumor Microenvironment

Tumor vascularization refers to the formation of new blood vessels within a tumor and is considered one of the hallmarks of cancer. Tumor vessels supply the tumor with oxygen and nutrients, required to sustain tumor growth and progression, and provide a gateway for tumor metastasis through the blood or lymphatic vasculature. Blood vessels display an angiocrine capacity of supporting the survival and proliferation of tumor cells through the production of growth factors and cytokines. Although tumor vasculature plays an essential role in sustaining tumor growth, it represents at the same time an essential way to deliver drugs and immune cells to the tumor. However, tumor vasculature exhibits many morphological and functional abnormalities, thus resulting in the formation of hypoxic areas within tumors, believed to represent a mechanism to maintain tumor cells in an invasive state.Tumors are vascularized through a variety of modalities, mainly represented by angiogenesis, where VEGF and other members of the VEGF family play a key role. This has represented the basis for the development of anti-VEGF blocking agents and their use in cancer therapy: however, these agents failed to induce significant therapeutic effects.Much less is known about the cellular origin of vessel network in tumors. Various cell types may contribute to tumor vasculature in different tumors or in the same tumor, such as mature endothelial cells, endothelial progenitor cells (EPCs), or the same tumor cells through a process of transdifferentiation. Early studies have suggested a role for bone marrow-derived EPCs; these cells do not are true EPCs but myeloid progenitors differentiating into monocytic cells, exerting a proangiogenic effect through a paracrine mechanism. More recent studies have shown the existence of tissue-resident endothelial vascular progenitors (EVPs) present at the level of vessel endothelium and their possible involvement as cells of origin of tumor vasculature.

The ATF6-EGF Pathway Mediates the Awakening of Slow-Cycling Chemoresistant Cells and Tumor Recurrence by Stimulating Tumor Angiogenesis

Slow-cycling cancer cells (SCCs) with a quiescence-like phenotype are believed to perpetrate cancer relapse and progression. However, the mechanisms that mediate SCC-derived tumor recurrence are poorly understood. Here, we investigated the mechanisms underlying cancer recurrence after chemotherapy, focusing on the interplay between SCCs and the tumor microenvironment. We established a preclinical model of SCCs by exposing non-small-cell lung cancer (NSCLC) cells to either the proliferation-dependent dye carboxyfluorescein diacetate succinimidyl ester (CFSE) or chemotherapeutic drugs. An RNA sequencing analysis revealed that the established SCCs exhibited the upregulation of a group of genes, especially epidermal growth factor (EGF). Increases in the number of vascular endothelial growth factor receptor (VEGFR)-positive vascular endothelial cells and epidermal growth factor receptor (EGFR) activation were found in NSCLC cell line- and patient-derived xenograft tumors that progressed upon chemotherapy. EGFR tyrosine kinase inhibitors effectively suppressed the migration and tube formation of vascular endothelial cells. Furthermore, activating transcription factor 6 (ATF6) induced the upregulation of EGF, and its antagonism effectively suppressed these SCC-mediated events and inhibited tumor recurrence after chemotherapy. These results suggest that the ATF6-EGF signaling axis in SCCs functions to trigger the angiogenesis switch in residual tumors after chemotherapy and is thus a driving force for the switch from SCCs to actively cycling cancer cells, leading to tumor recurrence.

Role of PI3K/AKT pathway in cancer: the framework of malignant behavior

Given that the PI3K/AKT pathway has manifested its compelling influence on multiple cellular process, we further review the roles of hyperactivation of PI3K/AKT pathway in various human cancers. We state the abnormalities of PI3K/AKT pathway in different cancers, which are closely related with tumorigenesis, proliferation, growth, apoptosis, invasion, metastasis, epithelial-mesenchymal transition, stem-like phenotype, immune microenvironment and drug resistance of cancer cells. In addition, we investigated the current clinical trials of inhibitors against PI3K/AKT pathway in cancers and found that the clinical efficacy of these inhibitors as monotherapy has so far been limited despite of the promising preclinical activity, which means combinations of targeted therapy may achieve better efficacies in cancers. In short, we hope to feature PI3K/AKT pathway in cancers to the clinic and bring the new promising to patients for targeted therapies.

ROS and oncogenesis with special reference to EMT and stemness

Elevation of the level of intracellular reactive oxygen species (ROS) has immense implication in the biological system. On the one hand, ROS promote the signaling cascades for the maintenance of normal physiological functions, the phenomenon referred to as redox biology, and on the other hand increased ROS can cause damages to the cellular macromolecules as well as genetic material, the process known as oxidative stress. Oxidative stress acts as an etiological factor for wide varieties of pathologies, cancer being one of them. ROS is regarded as a "double-edged sword" with respect to oncogenesis. It can suppress as well as promote the malignant progression depending on the type of signaling pathway it uses. Moreover, the attribution of ROS in promoting phenotypic plasticity as well as acquisition of stemness during neoplasia has become a wide area of research. The current review discussed all the aspects of ROS in the perspective of tumor biology with special reference to epithelial-mesenchymal transition (EMT) and cancer stem cells.

Beyond Tumor Suppression: Senescence in Cancer Stemness and Tumor Dormancy

Here, we provide an overview of the importance of cellular fate in cancer as a group of diseases of abnormal cell growth. Tumor development and progression is a highly dynamic process, with several phases of evolution. The existing evidence about the origin and consequences of cancer cell fate specification (e.g., proliferation, senescence, stemness, dormancy, quiescence, and cell cycle re-entry) in the context of tumor formation and metastasis is discussed. The interplay between these dynamic tumor cell phenotypes, the microenvironment, and the immune system is also reviewed in relation to cancer. We focus on the role of senescence during cancer progression, with a special emphasis on its relationship with stemness and dormancy. Selective interventions on senescence and dormancy cell fates, including the specific targeting of cancer cell populations to prevent detrimental effects in aging and disease, are also reviewed. A new conceptual framework about the impact of synthetic lethal strategies by using senogenics and then senolytics is given, with the promise of future directions on innovative anticancer therapies.

GASC1-Adapted Neoadjuvant Chemotherapy for Resectable Esophageal Squamous Cell Carcinoma: A Prospective Clinical Biomarker Trial

Neoadjuvant chemotherapy (NCT) is a standard care for esophageal squamous cell carcinoma (ESCC), but the efficacy is unsatisfactory. Cancer stem cells (CSCs) play key roles in chemotherapy resistance. Gene amplified in squamous cell carcinoma 1 (GASC1) is a neoteric gene in stemness maintaining of ESCC. We aimed to reveal whether GASC1 could be a predictive biomarker for NCT in ESCC. ESCC patients (T2-4N0-2M0) were evaluated for GASC1 expression using immunohistochemical staining and classified as GASC1-low group (GLG) and GASC1-high group (GHG). NCT was delivered in two cycles and then the surgery was completed. Primary endpoints were tumor regression grade (TRG) and objective response rate (ORR); secondary endpoints were radical surgical resection (R0) rate and three-year overall survival (OS). 60 patients were eligible with evaluable outcomes: 24 in GHG and 36 in GLG. Between GHG and GLG, TRG1, TRG2, TRG3, and TRG4 were 0 : 16.7%, 20.8% : 41.7%, 58.3% : 36.1%, and 20.8% : 5.6%, respectively (P=0.006); ORR and R0 rate were 33.3% : 69.4% (P=0.006) and 75% : 94.4% (P=0.046), respectively; the median OS was 20 : 32 (months) (P=0.0356). No significant difference in the three-year OS was observed between GHG and GLG: 29.2% : 41.7% (P=0.24). Furthermore, the GASC1 expression level was associated with poor OS independent of other factors by univariate and multivariate analyses. Therefore, GASC1 might be a potential biomarker to predict NCT efficacy for ESCC.

High FOXK1 expression correlates with poor outcomes in hepatocellular carcinoma and regulates stemness of hepatocellular carcinoma cells

AIMS

Forkhead box (FOX) proteins constitute a huge family of transcriptional regulators, which are involved in a wide range of cancers. FOXK1 is a little studied member of FOXK subfamily. This study aimed to investigate the potential prognostic value of FOXK1 in human hepatocellular carcinoma (HCC) and explore potential underlying mechanisms.

MAIN METHODS

We performed bioinformatic analyses to evaluate the prognostic value of FOXK1 expression in human HCC and to reveal the underlying mechanism by which FOXK1 regulates HCC. RT-PCR, FACS analysis and sphere formation assay were carried out to investigate the role of FOXK1 in regulating liver cancer stem cells.

KEY FINDINGS

Our results demonstrated that FOXK1 was overexpressed in human HCC and positively correlated with cancer progression. DNA hypomethylation and gene copy number variation contributed to the overexpression of FOXK1. Importantly, high FOXK1 expression was associated with both low overall survival probability (OS) and low relapse free survival probability (RFS) of HCC patients. Intriguingly, we found that high FOXK1 expression was correlated with activation of stem cell-regulating pathways in human HCC. Knockdown of FOXK1 resulted in downregulation of the cancer stem cell marker EpCAM and ALDH1 and decreased sphere-forming ability of hepatocellular carcinoma cells.

SIGNIFICANCE

Overall, our study identified FOXK1 as a new biomarker for prognosis of HCC patients and revealed its role in regulating stemness of hepatocellular carcinoma cells.

Chromatin target of protein arginine methyltransferase regulates invasion, chemoresistance, and stemness in epithelial ovarian cancer

Ovarian cancer is one of the most common gynecological cancers with a high mortality rate in females. Chromatin target of protein arginine methyltransferase (CHTOP) is an important intracellular protein that regulates the transcriptional activation of several oncogenic genes in glioblastomagenesis and controls mature mRNA export as a component of TRanscription-Export complex. However, the role of CHTOP in ovarian cancer is unclear. In the present study, we investigated the correlation between tumor-derived CHTOP expression and prognosis and explored its role in the malignant behaviors of epithelial ovarian cancer cells. We found that higher expression of CHTOP was associated with a lower disease-free survival (DFS) rate in ovarian cancer patients. Also, CHTOP was highly expressed in human ovarian cancer tissues compared with normal and adjacent tissues. Moreover, compared with IGROV-1 cell line, higher expression of CHTOP was also confirmed in the malignant ovarian cancer cell lines (OV-90 and SK-OV-3). Further results from wound-healing and Matrigel assay showed that CHTOP knockdown significantly reduced the migration and invasion ability of OV-90 and SK-OV-3 cells, while colony formation assay and apoptosis detection showed that CHTOP knockdown markedly sensitized OV-90 and SK-OV-3 cells to cisplatin treatment by inducing apoptosis. Additionally, CHTOP silence also remarkably weakened the stemness of OV-90 and SK-OV-3 through inhibiting the protein expressions of several transcriptional or surface markers of cancer stem cells. These findings first suggest that CHTOP, as a highly expressed protein in ovarian cancer, is closely associated with the malignant phenotypes of epithelial ovarian cancer cells, including metastasis, chemoresistance, and stemness, which highlights a promising role of CHTOP in ovarian cancer targeted therapy.

GASC1 Promotes Stemness of Esophageal Squamous Cell Carcinoma via NOTCH1 Promoter Demethylation

The highest incidence of esophageal squamous cell carcinoma (ESCC) occurs in China. Cancer stem cells play key roles for tumor progression. Gene amplified in squamous cell carcinoma 1 (GASC1) is essential to maintain self-renewal and differentiation potential of embryonic stem cells. This study aimed to reveal the effect and mechanism of GASC1 on ESCC stemness. The biological function of GASC1 in ESCC was evaluated both in vitro and in vivo. ChIP assay was performed to determine the molecular mechanism of GASC1 in epigenetic regulation of NOTCH1. We found that GASC1 expression was increased in poor differentiated ESCC cells and tissues. ESCC patients with a high level of GASC1 presented a significantly worse survival rate. GASC1 expression in purified ALDH⁺ ESCC cells was significantly higher than that in ALDH⁻ cells. The stemness of ESCC was dramatically decreased after GASC1 blockade. Furthermore, blockade of GASC1 decreased NOTCH1 expression via increase of NOTCH1 promoter H3K9me2 and H3K9me3. Moreover, the impaired stemness after blockade of GASC1 could be reversed after transfection of NOTCH1 overexpression lentiviral vector. GASC1 promoted stemness in ESCC cells via NOTCH1 promoter demethylation. Therefore, GASC1/NOTCH1 signaling might be a potential therapeutic target for the treatment of ESCC patients.

Engineered In Vitro Models of Tumor Dormancy and Reactivation

Metastatic recurrence is a major hurdle to overcome for successful control of cancer-associated death. Residual tumor cells in the primary site, or disseminated tumor cells in secondary sites, can lie in a dormant state for long time periods, years to decades, before being reactivated into a proliferative growth state. The microenvironmental signals and biological mechanisms that mediate the fate of disseminated cancer cells with respect to cell death, single cell dormancy, tumor mass dormancy and metastatic growth, as well as the factors that induce reactivation, are discussed in this review. Emphasis is placed on engineered, in vitro, biomaterial-based approaches to model tumor dormancy and subsequent reactivation, with a focus on the roles of extracellular matrix, secondary cell types, biochemical signaling and drug treatment. A brief perspective of molecular targets and treatment approaches for dormant tumors is also presented. Advances in tissue-engineered platforms to induce, model, and monitor tumor dormancy and reactivation may provide much needed insight into the regulation of these processes and serve as drug discovery and testing platforms.

Lung cancer stem cells: origin, features, maintenance mechanisms and therapeutic targeting

Lung cancer remains the leading cause of cancer-related deaths despite recent breakthroughs in immunotherapy. The widely embraced cancer stem cell (CSC) theory has also been applied for lung cancer, postulating that an often small proportion of tumor cells with stem cell properties are responsible for tumor growth, therapeutic resistance and metastasis. The identification of these CSCs and underlying molecular maintenance mechanisms is considered to be absolutely necessary for developing therapies for their riddance, hence achieving remission. In this review, we will critically address the CSC concept in lung cancer and its advancement thus far. We will describe both normal lung stem cells and their malignant counterparts in order to identify common aspects with respect to their emergence and regulation. Subsequently, the importance of CSCs and their molecular features in lung cancers will be discussed in a preclinical and clinical context. We will highlight some examples on how lung CSCs attain stemness through different molecular modifications and cellular assistance from the tumor microenvironment. The exploitation of these mechanistic features for the development of pharmacological therapy will also be discussed. In summary, the validity of the CSC concept has been evidenced by various studies. Ongoing research to identify molecular mechanisms driving lung CSC have revealed potential new cell intrinsic as well as tumor microenvironment-derived therapeutic targets. Although successfully demonstrated in preclinical models, the clinical benefit of lung CSC targeted therapies has thus far not been demonstrated. Therefore, further research to validate the therapeutic value of CSC concept is required.