A unified model of the hierarchical and stochastic theories of gastric cancer

The SIX2/PFN2 feedback loop promotes the stemness of gastric cancer cells

BACKGROUND

The roles of the transcriptional factor SIX2 have been identified in several tumors. However, its roles in gastric cancer (GC) progression have not yet been revealed. Our objective is to explore the impact and underlying mechanisms of SIX2 on the stemness of GC cells.

METHODS

Lentivirus infection was employed to establish stable expression SIX2 or PFN2 in GC cells. Gain- and loss-of-function experiments were conducted to detect changes of stemness markers, flow cytometry profiles, tumor spheroid formation, and tumor-initiating ability. ChIP, RNA-sequencing, tissue microarray, and bioinformatics analysis were performed to reveal the correlation between SIX2 and PFN2. The mechanisms underlying the SIX2/PFN2 loop-mediated effects were elucidated through tissue microarray analysis, RNA stability assay, IP-MS, Co-Immunoprecipitation, and inhibition of the JNK signaling pathway.

RESULTS

The stemness of GC cells was enhanced by SIX2. Mechanistically, SIX2 directly bound to PFN2's promoter and promoted PFN2 activity. PFN2, in turn, promoted the mRNA stability of SIX2 by recruiting RNA binding protein YBX-1, subsequently activating the downstream MAPK/JNK pathway.

CONCLUSION

This study unveils the roles of SIX2 in governing GC cell stemness, defining a novel SIX2/PFN2 regulatory loop responsible for this regulation. This suggests the potential of targeting the SIX2/PFN2 loop for GC treatment (Graphical Abstracts).

Wnt signaling in gastric cancer: current progress and future prospects

Levels of the Wnt pathway components are abnormally altered in gastric cancer cells, leading to malignant cell proliferation, invasion and metastasis, poor prognosis and chemoresistance. Therefore, it is important to understand the mechanism of Wnt signaling pathway in gastric cancer. We systematically reviewed the molecular mechanisms of the Wnt pathway in gastric cancer development; and summarize the progression and the challenges of research on molecular agents of the Wnt pathway.

Radioresistance or/and radiosensitivity of head and neck squamous cell carcinoma: biological angle

OBJECTIVE

This narrative review aimed to compile and summarize clinically relevant literature in radiation therapy and to discuss the potential in radioresistant and radiosensitive head and neck squamous cell carcinoma (HNSCC).

METHODS AND MATERIALS

Google Scholar, PubMed, and the Cochrane Library were retrieved using combined key words such as "radiotherapy" and "head and neck cancer." Search strings additionally queried were "radioresistant," "radiosensitive," "head and neck region," "squamous cell carcinoma," in combination with Boolean operators 'AND' and 'OR.' Subsequently, the resulting publications were included for review of the full text.

RESULTS

Radiotherapeutic responses currently in clinical observation referred to HNSCC scoping were selected into this review. The compiled mechanisms were then detailed concerning on the clinical significance, biological characteristics, and molecular function.

CONCLUSIONS

Brachytherapy or/and external-beam radiotherapy are crucial for treating HNSCC especially the early stage patients, but in some patients with locally advanced tumors, their outcome with radiation therapy is poor due to obvious radioresistance. The curative effects mainly depend on the response to radiation therapy so an updated review is needed to optimize further applications in HNSCC radiotherapy.

A radiobiological perspective on radioresistance or/and radiosensitivity of head and neck squamous cell carcinoma

Background

This article aimed to compile and summarize clinically relevant literature in radiation therapy, and to discuss the potential in radioresistant and radiosensitive head and neck cancer.

Study Design

Narrative review.

Materials and methods

Google Scholar, PubMed and the Cochrane Library were retrieved using combined key words such as "radiotherapy" and "head and neck cancer". Search strings additionally queried were "radioresistant", "radiosensitive", "head and neck region", "squamous cell carcinoma", in combination with Boolean Operators 'AND' and 'OR'. Subsequently, the resulting publications were included for review of the full text.

Results

Radiotherapeutic response currently in clinical observation referred to HNSCC scoping were selected into this review. The compiled mechanisms were then detailed concerning on the clinical significance, biological characteristics, and molecular function.

Conclusions

Brachytherapy or/and external-beam radiotherapy are crucial for treating HNSCC, especially the early stage patients, but in patients with locally advanced tumors, their outcome with radiation therapy is poor due to obvious radioresistance. The curative effects mainly depend on the response of radiation therapy, so an updated review is needed to optimize further applications in HNSCC radiotherapy.

Celastrus orbiculatus extract suppresses gastric cancer stem cells through the TGF-β/Smad signaling pathway

Cancer stem cells (CSCs) are the primary source of tumor recurrence and chemoresistance, which complicates tumor treatment and has a significant impact on poor patient prognosis. Therefore, the discovery of inhibitors that specifically target CSCs is warranted. Previous research has established that the TGF-β/Smad signaling pathway is critical for the maintenance of CSCs phenotype, thus facilitating CSCs transformation. In this regard, Celastrus orbiculatus ethyl acetate extract (COE) was shown to exert anticancer properties; however, its therapeutic impact on gastric cancer stem cells (GCSCs) remains unknown. We here demonstrate that COE displayed a strong inhibitory effect on GCSCs growth and CSCs markers. Moreover, COE was shown to efficiently inhibit the development of tumor spheres and accelerate GCSCs apoptosis. Mechanistically, we established that COE could suppress the stemness phenotype of GCSCs by inhibiting the activity of the TGF-β/Smad signaling pathway. To summarize, our data indicate that COE suppresses the malignant biological phenotype of GCSCs via the TGF-β/Smad signaling pathway. These findings shed new light on the anticancer properties of COE and suggest new strategies for the development of efficient GCSCs therapeutics.

Past, present, and future of chemically induced hepatocarcinogenesis rodent models: Perspectives concerning classic and new cancer hallmarks

Hepatocellular carcinoma (HCC), the main primary liver cancer, accounts for 5 % of all incident cases and 8.4 % of all cancer-related deaths worldwide. HCC displays a spectrum of environmental risk factors (viral chronic infections, aflatoxin exposure, alcoholic- and nonalcoholic fatty liver diseases) that result in molecular complexity and heterogeneity, contributing to a rising epidemiological burden, poor prognosis, and non-satisfactory treatment options. The emergence of HCC (i.e., hepatocarcinogenesis) is a multistep and complex process that addresses many (epi)genetic alterations and phenotypic traits, the so-called cancer hallmarks. "Polymorphic microbiomes", "epigenetic reprogramming", "senescent cells" and "unlocking phenotypic plasticity" are trending hallmarks/enabling features in cancer biology. As the main molecular drivers of HCC are still undruggable, chemically induced in vivo models of hepatocarcinogenesis are useful tools in preclinical research. Thus, this narrative review aimed at recapitulating the basic features of chemically induced rodent models of hepatocarcinogenesis, eliciting their permanent translational value regarding the "classic" and the "new" cancer hallmarks/enabling features. We gathered state-of-art preclinical evidence on non-cirrhotic, inflammation-, alcoholic liver disease- and nonalcoholic fatty liver-associated HCC models, demonstrating that these bioassays indeed express the recently added hallmarks, as well as reflect the interplay between classical and new cancer traits. Our review demonstrated that these protocols remain valuable for translational preclinical application, as they recapitulate trending features of cancer science. Further "omics-based" approaches are warranted while multimodel investigations are encouraged in order to avoid "model-biased" responses.

Epstein-Barr Virus Promotes Oral Squamous Cell Carcinoma Stemness through the Warburg Effect

Epstein-Barr virus (EBV) is associated with various human malignancies. An association between EBV infection and oral squamous cell carcinoma (OSCC) has recently been reported. We established EBV-positive OSCC cells and demonstrated that EBV infection promoted OSCC progression. However, the mechanisms by which EBV promotes OSCC progression remain poorly understood. Therefore, we performed metabolic analyses of EBV-positive OSCC cells and established a xenograft model to investigate the viral contribution to OSCC progression. Here, we demonstrated that EBV infection induced mitochondrial stress by reducing the number of mitochondrial DNA (mtDNA) copies. Microarray data from EBV-positive OSCC cells showed altered expression of glycolysis-related genes, particularly the upregulation of key genes involved in the Warburg effect, including LDHA, GLUT1, and PDK1. Furthermore, lactate production and LDH activity were elevated in EBV-positive OSCC cells. EBV infection significantly upregulated the expression levels of cancer stem cell (CSC) markers such as CD44 and CD133 in the xenograft model. In this model, tumor growth was significantly increased in EBV-positive SCC25 cells compared with that in uninfected cells. Furthermore, tumorigenicity increased after serial passages of EBV-positive SCC25 tumors. This study revealed the oncogenic role of EBV in OSCC progression by inducing the Warburg effect and cancer stemness.

PTBP1 drives c-Myc-dependent gastric cancer progression and stemness

BACKGROUND

Gastric cancer (GC) tumorigenesis and treatment failure are caused by cancer stem cells. Polypyrimidine tract binding protein 1 (PTBP1) was shown to be involved in the development of embryonic stem cells and is now being considered as a therapeutic target for tumour progression and stem-cell characteristics.

METHODS

PTBP1 expression in GC samples was detected using tissue microarrays. Proliferation, colony formation, spheroid formation and stem-cell analysis were used to examine PTBP1's role in tumorigenesis and stem-cell maintenance. In AGS and HGC-27 cells with or without PTBP1 deficiency, ubiquitin-related protein expression and co-precipitation assays were performed.

RESULTS

We identified that PTBP1 was aberrantly highly expressed and represented a novel prognostic factor in GC patients. PTBP1 maintained the tumorigenic activity and stem-cell characteristics of GC in vitro and in vivo. PTBP1 directly interacts with c-Myc and stabilises its protein levels by preventing its proteasomal degradation. This is mediated by upregulating the ubiquitin-specific proteases USP28 and limiting FBW7-mediated ubiquitination of c-Myc. Moreover, the depletion of PTBP1-caused tumour regression was significantly compromised by exogenous c-Myc expression.

CONCLUSIONS

By preserving the stability of c-Myc through the ubiquitin-proteasome pathway, the oncogene PTBP1 supports stem-cell-like phenotypes of GC and is involved in GC progression.

The origin of gastric cancer stem cells and their effects on gastric cancer: Novel therapeutic targets for gastric cancer

Gastric cancer (GC) is one of the most prevalent malignancies and the most common causes of cancer-related mortality worldwide. Furthermore, the prognosis of advanced GC remains poor even after surgery combined with chemoradiotherapy. As a small group of cells with unlimited differentiation and self-renewal ability in GC, accumulating evidence shows that GC stem cells (GCSCs) are closely associated with the refractory characteristics of GC, such as drug resistance, recurrence, and metastasis. With the extensive development of research on GCSCs, GCSCs seem to be promising therapeutic targets for GC. However, the relationship between GCSCs and GC is profound and intricate, and its mechanism of action is still under exploration. In this review, we elaborate on the source and key concepts of GCSCs, systematically summarize the role of GCSCs in GC and their underlying mechanisms. Finally, we review the latest information available on the treatment of GC by targeting GCSCs. Thus, this article may provide a theoretical basis for the future development of the novel targets based on GCSCs for the treatment of GC.

Potential to Eradicate Cancer Stemness by Targeting Cell Surface GRP78

Cancer stemness is proposed to be the main cause of metastasis and tumor relapse after conventional therapy due to the main properties of cancer stem cells. These include unlimited self-renewal, the low percentage in a cell population, asymmetric/symmetric cell division, and the hypothetical different nature for absorbing external substances. As the mechanism of how cancer stemness is maintained remains unknown, further investigation into the basic features of cancer stemness is required. Many articles demonstrated that glucose-regulated protein 78 (GRP78) plays a key role in cancer stemness, suggesting that this molecule is feasible for targeting cancer stem cells. This review summarizes the history of finding cancer stem cells, as well as the functions of GRP78 in cancer stemness, for discussing the possibility of targeting GRP78 to eradicate cancer stemness.

Requirement of transcription factor NME2 for the maintenance of the stemness of gastric cancer stem-like cells

Cancer stem cells (CSCs), which can self-renew and produce heterogeneous cancer cells, are the key factors during tumorigenesis. Transcription factors take essential effects on CSCs. However, the role of transcription factors in regulating the stemness of gastric cancer stem-like cells has not been well explored. In this investigation, it was found that transcription factor NME2 (NME/NM23 nucleoside diphosphate kinase 2) was upregulated in gastric cancer stem-like cells that sorted from the solid tumors of patients with gastric cancer and gastric cancer cell lines. NME2 could preserve the stemness of gastric cancer stem-like cells via suppressing their apoptosis. In vitro and in vivo data revealed that NME2 was crucial for maintaining the stemness of gastric cancer stem cells by enhancing the expression of anti-apoptosis genes. Consequently, our data contributed a new perspective to the relationship between transcription factor and the stemness maintenance of gastric cancer stem cells.

Translational models of 3-D organoids and cancer stem cells in gastric cancer research

It is postulated as a general concept of cancer stem cells (CSCs) that they can produce cancer cells overtly and repopulate cancer progenitor cells indefinitely. The CSC niche is part of a specialized cancer microenvironment that is important to keep the phenotypes of CSCs. Stem cell- and induced pluripotent stem cell (iPSC)-derived organoids with genetic manipulation are beneficial to the investigation of the regulation of the microenvironment of CSCs. It would be useful to assess the efficiency of the cancer microenvironment on initiation and progression of cancers. To identify CSCs in cancer tissues, normal cell organoids and gastric cancer organoids from the cancerous areas, as well as iPSCs, were established several years ago. However, many questions remain about the extent to which these cultures recapitulate the development of the gastrointestinal tract and the mechanism of Helicobacter pylori-induced cancer progression. To clarify the fidelity of human organoid models, we have noted several key issues for the cultivation of, and differences between, normal and cancerous organoids. We developed precise culture conditions for gastric organoids in vitro to improve the accuracy of the generation of organoid models for therapeutic and medical applications. In addition, the current knowledge on gastrointestinal CSC research, including the topic of CSC markers, cancer cell reprogramming, and application to target cancer cell plasticity through niches, should be reinforced. We discuss the progression of cancers derived from human gastric organoids and the identification of CSCs.

Asporin represses gastric cancer apoptosis via activating LEF1-mediated gene transcription independent of β-catenin

Asporin (ASPN) presents in the tumor microenvironment and exhibits a cancer-promoting effect as a stroma protein. Even though ASPN has already been observed inside cancer cells, the functions of intracellular ASPN and its underlying mechanisms remain unknown. Here we reported that ASPN was upregulated in different stages of gastric cancer (GC), and associated with a poor prognosis. Moreover, we found that ASPN markedly inhibited GC cell apoptosis and promoted cell growth in vitro and in vivo. Further mechanism investigations revealed that ASPN directly binding to lymphoid enhancer-binding factor 1 (LEF1) and promoted LEF1-mediated gene transcription independent of β-catenin, the classic co-factor in the Wnt/LEF1 pathway. We also demonstrated that ASPN selectively facilitated LEF1 binding to and activating the promoters of PTGS2, IL6, and WISP1 to promote their transcription. The suppression of cell apoptosis by ASPN overexpression could be attenuated by LEF1 knockdown or 100 µM aspirin (PTGS2 inhibitor), and siASPN mediated apoptosis could be rescued by LEF1 ectopic expression or adding recombinant IL6. Therefore, we concluded that ASPN repressed GC cell apoptosis via activating LEF1-mediated gene transcription independent of β-catenin, which could serve as a potential prognostic biomarker in GC patients.

Adamantinomatous craniopharyngioma as a model to understand paracrine and senescence-induced tumourigenesis

Cellular senescence is a process that can prevent tumour development in a cell autonomous manner by imposing a stable cell cycle arrest after oncogene activation. Paradoxically, senescence can also promote tumour growth cell non-autonomously by creating a permissive tumour microenvironment that fuels tumour initiation, progression to malignancy and metastasis. In a pituitary tumour known as adamantinomatous craniopharyngioma (ACP), cells that carry oncogenic β-catenin mutations and overactivate the WNT signalling pathway form cell clusters that become senescent and activate a senescence-associated secretory phenotype (SASP). Research in mouse models of ACP has provided insights into the function of the senescent cell clusters and revealed a critical role for SASP-mediated activities in paracrine tumour initiation. In this review, we first discuss this research on ACP and subsequently explore the theme of paracrine tumourigenesis in other tumour models available in the literature. Evidence is accumulating supporting the notion that paracrine signalling brought about by senescent cells may underlie tumourigenesis across different tumours and cancer models.

Eradicating the Roots: Advanced Therapeutic Approaches Targeting Breast Cancer Stem Cells

Accumulating evidences have demonstrated that the existence of breast cancer-initiating cells, which drives the original tumorigenicity, local invasion and migration propensity of breast cancer. These cells, termed as breast cancer stem cells (BCSCs), possess properties including self-renewal, multidirectional differentiation and proliferative potential, and are believed to play important roles in the intrinsic drug resistance of breast cancer. One of the reasons why BCBCs cause difficulties in breast cancer treating is that BCBCs can control both genetic and non-genetic elements to keep their niches safe and sound, which allows BCSCs for constant self-renewal and differentiation. Therapeutic strategies designed to target BCSCs may ultimately result in effective interventions for the treatment of breast cancer. Novel strategies including nanomedicine, oncolytic virus therapy, immunotherapy and induced differentiation therapy are emerging and proved to be efficient in anti-BCSCs therapy. In this review, we summarized breast tumor biology and the current challenges of breast cancer therapies, focused on breast cancer stem cells, and introduced promising therapeutic strategies targeting BCSCs.

Evaluation of miR-302 promoter activity in transgenic mice and pluripotent stem cell lines

Some miRNAs, including the miR-302 cluster, are critical regulators of the stemness state of embryonic stem cells and cell fate patterning. In this study, we evaluated the activity of the miR-302 core promotor in mice and human pluripotent stem cells, somatic tissue derivatives, and generated transgenic mice expressing EGFP under a miR-302 promoter. The expression of EGFP under the control of the miR-302 promotor was examined in the cell lines and somatic tissues of transgenic mice, transgenic blastocysts, and embryonic stem cells derived from transgenic blastocysts. Our results showed that the miR-302 promoter is highly expressed in the mouse and human pluripotent cells, weakly expressed in the somatic tissue derivatives, is highly expressed in both blastocysts and the first passages of transgenic embryonic stem cells, and lowly expressed in the somatic tissues of transgenic mice. It can be concluded that different temporal and spatial gene expression patterns occur during the embryonic and adult stages of cells in mice.

Cell Competition Boosts Clonal Evolution and Hypoxic Selection in Cancer

The comparison of fitness between cells leads to the elimination of less competent cells in the presence of more competent neighbors via cell competition (CC). This phenomenon has been linked with several cancer-related genes and thus may play an important role in cancer. Various processes are involved in the regulation of tumor initiation and growth, including tumor hypoxia, clonal stem cell selection, and immune cell response, all of which have been recently shown to have a potential connection with the mechanisms involved in CC. This review aims to unravel the relation between these processes and competitive cell interactions and how this affects disease progression.

Lycorine hydrochloride inhibits cell proliferation and induces apoptosis through promoting FBXW7-MCL1 axis in gastric cancer

Background

Lycorine hydrochloride (LH), an alkaloid extracted from the bulb of the Lycoris radiata, is considered to have anti-viral, anti-malarial, and anti-tumorous effects. At present, the underlying mechanisms of LH in gastric cancer remain unclear. MCL1, an anti-apoptotic protein of BCL2 family, is closely related to drug resistance of tumor. Therefore, MCL1 is considered as a potential target for cancer treatment.

Methods

The effect of LH on gastric cancer was assessed in vitro (by MTT, BrdU, western blotting…) and in vivo (by immunohistochemistry).

Results

In this study, we showed that LH has an anti-tumorous effect by down-regulating MCL1 in gastric cancer. Besides, we unveiled that LH reduced the protein stability of MCL1 by up-regulating ubiquitin E3 ligase FBXW7, arrested cell cycle at S phase and triggered apoptosis of gastric cancer cells. Meanwhile, we also demonstrated that LH could induce apoptosis of the BCL2-drug-resistant-cell-lines. Moreover, PDX (Patient-Derived tumor xenograft) model experiment proved that LH combined with HA14–1 (inhibitor of BCL2), had a more significant therapeutic effect on gastric cancer.

Conclusions

The efficacy showed in our data suggests that lycorine hydrochloride is a promising anti-tumor compound for gastric cancer.

Emergence of informative higher scales in biological systems: a computational toolkit for optimal prediction and control

The biological sciences span many spatial and temporal scales in attempts to understand the function and evolution of complex systems-level processes, such as embryogenesis. It is generally assumed that the most effective description of these processes is in terms of molecular interactions. However, recent developments in information theory and causal analysis now allow for the quantitative resolution of this question. In some cases, macro-scale models can minimize noise and increase the amount of information an experimenter or modeler has about "what does what." This result has numerous implications for evolution, pattern regulation, and biomedical strategies. Here, we provide an introduction to these quantitative techniques, and use them to show how informative macro-scales are common across biology. Our goal is to give biologists the tools to identify the maximally-informative scale at which to model, experiment on, predict, control, and understand complex biological systems.

Targeting MAD2 modulates stemness and tumorigenesis in human Gastric Cancer cell lines

Rationale: Gastric cancer (GC) is a solid tumor that contains subpopulations of cancer stem cells (CSCs), which are considered drivers of tumor initiation and metastasis; responsible for therapeutic resistance; and promoters of tumor relapse. The balance between symmetric and asymmetric division is crucial for stem cell maintenance. The objective of this study is to evaluate the role of MAD2, a key protein for proper mitotic checkpoint activity, in the tumorigenesis of GC.

Methods: Gastric cancer stem cells (GCSCs) were obtained from MKN45, SNU638 and ST2957 cell lines. Pluripotency and stemness markers were evaluated by RT-qPCR and autofluorescence and membrane markers by flow cytometry. Relevant signal transduction pathways were studied by WB. We analysed cell cycle progression, migration and invasion after modulation of MAD2 activity or protein expression levels in these in vitro models. In vivo assays were performed in a nude mouse subcutaneous xenograft model.

Results: We found that NANOG, CXCR4 and autofluorescence are common and consistent markers for the GCSCs analysed, with other markers showing more variability. The three main signalling pathways (Wnt/β-catenin; Hedgehog and Notch) were activated in GCSCs. Downregulation of MAD2 in MKN45^CSCs decreased the expression of markers CXCR4, CD133, CD90, LGR5 and VIM, without affecting cell cycle profile or therapy resistance. Moreover, migration, invasion and tumor growth were clearly reduced, and accordingly, we found that metalloprotease expression decreased. These results were accompanied by a reduction in the levels of transcription factors related with epithelial-to-mesenchymal transition.

Conclusions: We can conclude that MAD2 is important for GCSCs stemness and its downregulation in MKN45^CSCs plays a central role in GC tumorigenesis, likely through CXCR4-SNAI2-MMP1. Thus, its potential use in the clinical setting should be studied as its functions appear to extend beyond mitosis.

Cancer stem cells in Epstein-Barr virus-associated gastric carcinoma

Cancer stem cells (CSCs) play a decisive role in the development and progression of cancer. To investigate CSCs in Epstein-Barr virus (EBV)-associated carcinoma (EBVaGC), we screened previously reported stem cell markers of gastric cancer in EBV-infected gastric cancer cell lines (TMK1 and NUGC3) and identified CD44v6v9 double positive cells as candidate CSCs. CD44v6/v9^+/+ cells were sorted from EBVaGC cell line (SNU719) cells and EBV-infected TMK1 cells and these cell populations showed high spheroid-forming ability and tumor formation in SCID mice compared with the respective CD44v6/v9^-/- cells. Sphere-forming ability was dependent on the nuclear factor-κB (NF-κB) signaling pathway, which was confirmed by decrease of sphere formation ability under BAY 11-7082. Small interfering RNA knockdown of latent membrane protein 2A (LMP2A), one of the latent gene products of EBV infection, decreased spheroid formation in SNU719 cells. Transfection of the LMP2A gene increased the sphere-forming ability of TMK1 cells, which was mediated through NF-κB signaling. Together, these results indicate that CD44v6v9^+/+ cells are CSCs in EBVaGC that are maintained through the LMP2A/NF-κB pathway. Future studies should investigate CD44v6/v9^+/+ cells in normal and neoplastic gastric epithelium to prevent and treat this specific subtype of gastric cancer infected with EBV.

Stearoyl-CoA-desaturase-1 regulates gastric cancer stem-like properties and promotes tumour metastasis via Hippo/YAP pathway

Background

Stearoyl-CoA desaturase-1 (SCD1) is reported to play essential roles in cancer stemness among several cancers. Our previous research revealed significant overexpression of SCD1 in primary gastric cancer stem cells (GCSCs), with its functional role still unknown.

Methods

We stably established three primary GCSCs by sphere-forming assays and flow cytometry. Protein quantification and bioinformatics analysis were performed to reveal the differential protein pattern. Lentivirus-based small-interfering RNA (siRNA) knockdown and pharmacological inhibition approaches were used to characterise the function and molecular mechanism role of SCD1 in the regulation of GC stemness and tumour metastasis capacity both in vitro and in vivo.

Results

SCD1 was found to increase the population of GCSCs, whereas its suppression by an SCD1 inhibitor or knockdown by siRNA attenuated the stemness of GCSCs, including chemotherapy resistance and sphere-forming ability. Furthermore, SCD1 suppression reversed epithelial-to-mesenchymal transition and reduced the GC metastasis probability both in vitro and in vivo. Downregulation of SCD1 in GCSCs was associated with the expression of Yes-associated protein (YAP), a key protein in the Hippo pathway, and nuclear YAP translocation was also blocked by the SCD1 decrease.

Conclusions

SCD1 promotes GCSC stemness through the Hippo/YAP pathway. Targeting SCD1 might be a novel therapeutic strategy, especially to suppress GC metastasis and sensitise chemotherapy.

PAK1 silencing is synthetic lethal with CDK4/6 inhibition in gastric cancer cells via regulating PDK1 expression

Gastric cancer (GC) is one of the most common malignancies worldwide. The prognosis of GC is unsatisfied owning to widespread metastasis. P21-activated kinase 1 (PAK1), a member of serine/threonine kinases, is associated with the progression of multiple types of human cancers. Here, we demonstrated that CDK4/6 inhibitor reduced GC cell viability and decreased PAK1 expression. Consistently, PAK1 ablation increased GC cell sensitivity exposed to CDK4/6 inhibitor and promoted DNA damage. We also revealed PAK1 depletion notably affected PDK1-AKT pathway, and PDK1 overexpression totally abrogated the effect of PAK1 deletion on DNA damage in GC cells. Additionally, PDK1 overexpression also rescued the increased GC cell sensitivity towards CDK4/6 inhibitor and the cell cycle arrest caused by PAK1 depletion. Our findings, therefore, suggested that PAK1 silencing increased sensitivity to CDK4/6 inhibition in gastric cancer cells via PDK1-AKT pathway. We, therefore, thought PAK1 as a promising therapeutic target for the treatment of CDK4/6 inhibitor-resistant gastric cancer.

Helicobacter pylori infection and gastric cancer biology: tempering a double-edged sword

Helicobacter pylori (H. pylori) infection affects an estimated 4.4 billion people globally. Moreover, H. pylori presents the most significant risk factor for gastric cancer and low-grade mucosa-associated lymphoid tissue (MALT) lymphoma, and it is the first example of bacterial infection linked to carcinogenesis. Here, we contend that H. pylori research, which focuses on a cancer-causing pathogen resident in a relatively accessible organ, the stomach, could constitute an exemplar for microbial-related carcinogenesis in less tractable organs, such as the pancreas and lung. In this context, molecular biological approaches that could reap rewards are reviewed, including: (1) gastric cancer dynamics, particularly the role of stem cells and the heterogeneity of neoplastic cells, which are currently being investigated at the single-cell sequencing level; (2) mechanobiology, and the role of three-dimensional organoids and matrix metalloproteases; and (3) the connection between H. pylori and host pathophysiology and the gut microbiome. In the context of H. pylori's contribution to gastric cancer, several important conundrums remain to be fully elucidated. From among them, this article discusses (1) why H. pylori infection, which causes both gastric and duodenal inflammation, is only linked to gastric cancer; (2) whether a "precision oncomicrobiology" approach could enable a fine-tuning of the expression of only cancer-implicated H. pylori genes while maintaining beneficial H. pylori-mediated factors in extra-gastric tissues; and (3) the feasibility of using antibiotics targeting the microbial DNA damage system, which shares commonalities with mechanisms for human cell replication, as chemopreventives. Additional therapeutic perspectives are also discussed.

Isolation of cancer stem cells by selection for miR-302 expressing cells

BACKGROUND

Cancer stem cells are believed to be a major reason for long-term therapy failure because they are multi-drug resistant and able to rest mitotically inactive in the hypoxic center of tumors. Due to their variable number and their often low proliferation rate, cancer stem cells are difficult to purify in decent quantities and to grow in cell culture systems, where they are easily outcompeted by faster growing more 'differentiated', i.e., less stem cell-like tumor cells.

METHODS

Here we present a proof of principle study based on the idea to select cancer stem cells by means of the expression of a stem cell-specific gene. A selectable egfp-neo coding sequence was inserted in the last exon of the non-coding murine miR-302 host gene. As a stem cell specific regulatory element, 2.1 kb of the genomic region immediately upstream of the miR-302 host gene transcription start site was used. Stable transgenic CJ7 embryonic stem cells were used to induce teratomas.

RESULTS

After three weeks, tumors were removed for analysis and primary cultures were established. Stem cell-like cells were selected from these culture based on G418 selection. When the selection was removed, stem cell morphology and miR-302 expression were rapidly lost, indicating that it was not the original ES cells that had been isolated.

CONCLUSIONS

We show the possibility to use drug resistance expressed from a regulatory sequence of a stem cell-specific marker, to isolate and propagate cancer stem cells that otherwise might be hidden in the majority of tumor cells.

NK cells shape pancreatic and oral tumor microenvironments; role in inhibition of tumor growth and metastasis

We have recently shown that natural killer (NK) cells select and differentiate cancer stem cells (CSCs)/undifferentiated tumors via secreted and membrane bound IFN-gamma (IFN-γ) and TNF-alpha (TNF-α), preventing tumor growth and inducing remodeling of the tumor microenvironment. Since many conventional therapeutic strategies, including chemotherapy and radiotherapy remain fairly unsuccessful in treating CSCs/poorly differentiated tumors, there has been an increasing interest in NK cell-targeted immunotherapy for the treatment of aggressive tumors. In our recent studies, we used humanized-BLT (hu-BLT) mouse model with transplanted human bone marrow, liver and thymus to demonstrate the efficacy of adoptive transfer of ex vivo expanded, super-charged NK cells in selection and differentiation of stem-like tumors within the context of a fully reconstituted human immune system. Furthermore, we have demonstrated that CSCs differentiated with split-anergized NK cells prior to implantation in hu-BLT mice were not able to grow or metastasize. However, when NK cell-mediated tumor differentiation was blocked by the addition of antibodies to IFN-γ and TNF-α, tumors grew and metastasized. In this review, we present current advances in NK cell expansion and therapeutic delivery, and discuss the utility of allogeneic super-charged NK cells in treatment of cancer patients. In addition, NK suppression occurs not only at the stage of overt cancer, but also at the pre-neoplastic stage. Therefore, due to the indispensable role of NK cells in targeting CSCs/undifferentiated tumors and their role in differentiation of the tumors, NK cells should be placed high in the armamentarium of tumor immunotherapy.

Gastric cancer: Basic aspects

Gastric cancer is one of the most incident and deadliest malignancies in the world. Gastric cancer is a heterogeneous disease and the end point of a long and multistep process, which results from the stepwise accumulation of numerous (epi)genetic alterations, leading to dysregulation of oncogenic and tumor suppressor pathways. Gastric cancer stem cells have emerged as fundamental players in cancer development and as contributors to gastric cancer heterogeneity. For this special issue, we will report last year's update on the gastric cancer molecular classification, and in particular address the gastric cancer groups who could benefit from immune checkpoint therapy. We will also review the latest advances on gastric cancer stem cells, their properties as gastric cancer markers and therapeutic targets, and associated signaling pathways. The understanding of the molecular basis underlying gastric cancer heterogeneity and of the role played by gastric cancer stem cells in cancer development and heterogeneity is of major significance, not only for identifying novel targets for cancer prevention and treatment, but also for clinical management and patient stratification for targeted therapies.