Transition of Mesenchymal and Epithelial Cancer Cells Depends on α1-4 Galactosyltransferase-Mediated Glycosphingolipids

Nuclear and cytosolic fractions of SOX2 synergize as transcriptional and translational co-regulators of cell fate

Stemness and pluripotency are mediated by transcriptional master regulators that promote self-renewal and repress cell differentiation, among which is the high-mobility group (HMG) box transcription factor SOX2. Dysregulated SOX2 expression, by contrast, leads to transcriptional aberrations relevant to oncogenic transformation, cancer progression, metastasis, therapy resistance, and relapse. Here, we report a post-transcriptional mechanism by which the cytosolic pool of SOX2 contributes to these events in an unsuspected manner. Specifically, a low-complexity region within SOX2's C-terminal segment connects to the ribosome to modulate the expression of cognate downstream factors. Independent of nuclear structures or DNA, this C-terminal functionality alone changes metabolic properties and induces non-adhesive growth when expressed in the cytosol of SOX2 knockout cells. We thus propose a revised model of SOX2 action where nuclear and cytosolic fractions cooperate to impose cell fate decisions via both transcriptional and translational mechanisms.

Single-cell profiling of surface glycosphingolipids opens a new dimension for deconvolution of breast cancer intratumoral heterogeneity and phenotypic plasticity

Glycosylated sphingolipids (GSLs) are a diverse group of cellular lipids typically reported as being rare in normal mammary tissue. In breast cancer (BCa), GSLs have emerged as noteworthy markers associated with breast cancer stem cells, mediators of phenotypic plasticity, and contributors to cancer cell chemoresistance. GSLs are potential surface markers that can uniquely characterize the heterogeneity of the tumor microenvironment, including cancer cell subpopulations and epithelial-mesenchymal plasticity (EMP). In this study, mass spectrometry analyses of the total sphingolipidome in breast epithelial cells and their mesenchymal counterparts revealed increased levels of Gb3 in epithelial cells and significantly elevated GD2 levels in the mesenchymal phenotype. To elucidate if GSL-related epitopes on BCa cell surfaces reflect EMP and cancer status, we developed and rigorously validated a 12-color spectral flow cytometry panel. This panel enables the simultaneous detection of native GSL epitopes (Gb3, SSEA1, SSEA3, SSEA4, and GD2), epithelial-mesenchymal transition markers (EpCAM, TROP2, and CD9), and lineage markers (CD45, CD31, and CD90) at the single-cell level. Next, the established panel was used for the analysis of BCa primary tumors and revealed surface heterogeneity in SSEA1, SSEA3, SSEA4, GD2, and Gb3, indicative of native epitope presence also on non-tumor cells. These findings further highlighted the phenotype-dependent alterations in GSL surface profiles, with differences between epithelial and stromal cells in the tumor. This study provides novel insights into BCa heterogeneity, shedding light on the potential of native GSL-related epitopes as markers for EMP and cancer status in fresh clinical samples. The developed single-cell approach offers promising avenues for further exploration.

High expression of embryonic stem cell marker SSEA3 confers poor prognosis and promotes epithelial mesenchymal transition in hepatocellular carcinoma

BACKGROUND

Malignant cells may arise from dedifferentiation of mature cells and acquire features of the progenitor cells. Definitive endoderm from which liver is derived, expresses glycosphingolipids (GSLs) such as stage-specific embryonic antigen 3 (SSEA3), Globo H, and stage-specific embryonic antigen 4 (SSEA4). Herein, we evaluated the potential prognosis value of the three GSLs and biological functions of SSEA3 in hepatocellular carcinoma (HCC).

METHODS

The expression of SSEA3, Globo H, and SSEA4 in tumor tissues obtained from 328 patients with resectable HCC was examined by immunohistochemistry staining. Epithelial mesenchymal transition (EMT) and their related genes were analyzed by transwell assay and qRT-PCR, respectively.

RESULTS

Kaplan Meier survival analysis showed significantly shorter relapse-free survival (RFS) for those with higher expression of SSEA3 (p < 0.001), Globo H (p < 0.001), and SSEA4 (p = 0.005) and worse overall survival (OS) for those with high expression of either SSEA3 (p < 0.001) or SSEA4 (p = 0.01). Furthermore, multivariable Cox regression analysis identified the SSEA3 as an independent predictor for RFS (HR: 2.68, 95% CI: 1.93-3.72, p < 0.001) and OS (HR: 2.99, 95% CI: 1.81-4.96, p < 0.001) in HCC. Additionally, SSEA3-ceramide enhanced the EMT of HCC cells, as reflected by its ability to increase migration, invasion and upregulate the expression of CDH2, vimentin, fibronectin, and MMP2, along with ZEB1. Moreover, ZEB1 silencing abrogated the EMT-enhancing effects of SSEA3-ceramide.

CONCLUSIONS

Higher expression of SSEA3 was an independent predictor for RFS and OS in HCC and promoted EMT of HCC via upregulation of ZEB1.

Gangliosides and Their Role in Multilineage Differentiation of Mesenchymal Stem Cells

Gangliosides (GGs) are a glycolipid class present on Mesenchymal Stem Cells (MSCs) surfaces with a critical appearance role in stem cell differentiation, even though their mechanistic role in signaling and differentiation remains largely unknown. This review aims to carry out a critical analysis of the predictive role of gangliosides as specific markers of the cellular state of undifferentiated and differentiated MSCs, towards the osteogenic, chondrogenic, neurogenic, and adipogenic lineage. For this reason, we analyzed the role of GGs during multilineage differentiation processes of several types of MSCs such as Umbilical Cord-derived MSCs (UC-MSCs), Bone Marrow-derived MSCs (BM-MSCs), Dental Pulp derived MSCs (DPSCs), and Adipose derived MSCs (ADSCs). Moreover, we examined the possible role of GGs as specific cell surface markers to identify or isolate specific stem cell isotypes and their potential use as additional markers for quality control of cell-based therapies.

Implications of cancer stem cells in diabetes and pancreatic cancer

This review provides a detailed study of pancreatic cancer (PC) and the implication of different types of cancers concerning diabetes. The combination of anti-diabetic drugs with other anti-cancer drugs and phytochemicals can help prevent and treat this disease. PC cancer stem cells (CSCs) and how they migrate and develop into malignant tumors are discussed. A detailed explanation of the different mechanisms of diabetes development, which can enhance the pancreatic CSCs' proliferation by increasing the IGF factor levels, epigenetic modifications, DNA damage, and the influence of lifestyle factors like obesity, and inflammation, has been discussed. It also explains how cancer due to diabetes is associated with high mortality rates. One of the well-known diabetic drugs, metformin, can be combined with other anti-cancer drugs and prevent the development of PC and has been taken as one of the prime focus in this review. Overall, this paper provides insight into the relationship between diabetes and PC and the methods that can be employed to diagnose this disease at an earlier stage successfully.

Novel Thieno [2,3-b]pyridine Anticancer Compound Lowers Cancer Stem Cell Fraction Inducing Shift of Lipid to Glucose Metabolism

Due to the role of cancer stem cells (CSCs) in tumor resistance and glycosphingolipid (GSL) involvement in tumor pathogenesis, we investigated the effect of a newly synthesized compound (3-amino-N-(3-chloro-2-methylphenyl)-5-oxo-5,6,7,8-tetrahydrothieno[2,3-b]quinoline-2-carboxamide 1 on the percentage of CSCs and the expression of six GSLs on CSCs and non-CSCs on breast cancer cell lines (MDA-MB-231 and MCF-7). We also investigated the effect of 1 on the metabolic profile of these cell lines. The MTT assay was used for cytotoxicity determination. Apoptosis and expression of GSLs were assessed by flow cytometry. A GC–MS-coupled system was used for the separation and identification of metabolites. Compound 1 was cytotoxic for both cell lines, and the majority of cells died by treatment-induced apoptosis. The percentage of CSCs was significantly lower in the MDA-MB-231 cell line. Treatment with 1 caused a decrease of CSC IV⁶Neu₅Ac-nLc₄Cer+ MDA-MB-231 cells. In the MCF-7 cell line, the percentage of GalNAc-GM1b+ CSCs was increased, while the expression of Gg₃Cer was decreased in both CSC and non-CSC. Twenty-one metabolites were identified by metabolic profiling. The major impact of the treatment was in glycolysis/gluconeogenesis, pyruvate and inositol metabolism. Compound 1 exhibited higher potency in MBA-MB-231 cells, and it deserves further examination.

Glycosphingolipids are mediators of cancer plasticity through independent signaling pathways

The molecular repertoire promoting cancer cell plasticity is not fully elucidated. Here, we propose that glycosphingolipids (GSLs), specifically the globo and ganglio series, correlate and promote the transition between epithelial and mesenchymal cells. The epithelial character of ovarian cancer remains stable throughout disease progression, and spatial glycosphingolipidomics reveals elevated globosides in the tumor compartment compared with the ganglioside-rich stroma. CRISPR-Cas9 knockin mediated truncation of endogenous E-cadherin induces epithelial-to-mesenchymal transition (EMT) and decreases globosides. The transcriptomics analysis identifies the ganglioside-synthesizing enzyme ST8SIA1 to be consistently elevated in mesenchymal-like samples, predicting poor outcome. Subsequent deletion of ST8SIA1 induces epithelial cell features through mTOR^S2448 phosphorylation, whereas loss of globosides in ΔA4GALT cells, resulting in EMT, is accompanied by increased ERK^Y202/T204 and AKT^S124. The GSL composition dynamics corroborate cancer cell plasticity, and further evidence suggests that mesenchymal cells are maintained through ganglioside-dependent, calcium-mediated mechanisms.

Sphingolipids in embryonic development, cell cycle regulation, and stemness - Implications for polyploidy in tumors

The aberrant biology of polyploid giant cancer cells (PGCC) includes dysregulation of the cell cycle, induction of stress responses, and dedifferentiation, all of which are likely accompanied by adaptations in biophysical properties and metabolic activity. Sphingolipids are the second largest class of membrane lipids and play important roles in many aspects of cell biology that are potentially relevant to polyploidy. We have recently shown that the function of the sphingolipid enzyme acid ceramidase (ASAH1) is critical for the ability of PGCC to generate progeny by depolyploidization but mechanisms by which sphingolipids contribute to polyploidy and generation of offspring with stem-like properties remain elusive. This review discusses the role of sphingolipids during embryonic development, cell cycle regulation, and stem cells in an effort to highlight parallels to polyploidy.

GBA1-dependent membrane glucosylceramide reprogramming promotes liver cancer metastasis via activation of the Wnt/β-catenin signalling pathway

The effect of glucosylceramide (GlcCer) reprogramming on liver cancer metastasis remains poorly understood. In this study, we demonstrated that the protein expression of GBA1, which catalyses the conversion of GlcCer to ceramide, was downregulated in liver cancer tissue. A clinical relevance analysis revealed that low expression of GBA1 was associated with the metastatic potential of liver cancer cells. Furthermore, loss- and gain-of-function studies confirmed that low expression of GBA1 promoted metastasis of liver cancer both in vitro and in vivo. Mechanistic studies indicated that low expression of GBA1 enhanced the metastatic ability of liver cancer by promoting the epithelial-mesenchymal transition (EMT), in which Wnt signalling pathway is involved. In the plasma membrane (PM), GBA1-dependent GlcCer reprogramming increased LRP6 location in the PM leading to an interaction between GlcCer and LRP6, subsequently promoting LRP6 phosphorylation at Ser1490, and finally activating the Wnt/β-catenin signalling pathway. To our knowledge, this is the first time to be found that GlcCer interacted with a protein. In addition, the results of mass spectrometry indicated that GlcCer d18:1/18:0 was the most notably increased studied species in the PM when GBA1 was downregulated, suggesting that GlcCer d18:1/18:0 may be the major functional lipid that promotes GBA1-dependent liver cancer metastasis. Thus, GBA1-mediated GlcCer reprogramming in the PM promotes metastasis of liver cancer via activation of the Wnt/β-catenin signalling pathway, upregulation of GBA1 may be a potential therapeutic strategy to combat liver cancer metastasis.

Maintenance Therapy with Aromatase Inhibitor in epithelial Ovarian Cancer (MATAO): study protocol of a randomized double-blinded placebo-controlled multi-center phase III Trial

Background

A high percentage of epithelial ovarian cancers (EOC) express the estrogen receptor (ER), which is an ideal target for endocrine therapy. Letrozole is a proven, potent aromatase inhibitor, extensively tested and used in the treatment of ER positive breast cancer. In addition, it seems a potent drug for patients with heavily pre-treated OC as demonstrated in several distinctive settings. However, it has never been evaluated prospectively in a maintenance setting for ovarian cancer after standard of care. The here proposed trial aims to define a population of EOC patients, who would benefit from the effectiveness of the generic agent letrozole, with little expected toxicity and thus beneficial impact on overall quality of life (QoL).

Methods

In this international multicenter randomized, placebo-controlled phase III trial at clinical centers in Switzerland, Germany and Austria, we plan to include 540 patients with primary, newly diagnosed FIGO Stage II to IV and histologically confirmed low- or high-grade serous or endometrioid epithelial ovarian/fallopian tube/peritoneal cancer. Patients are randomized in a 1:1 ratio into two groups: receiving blinded study treatment (letrozole or placebo tablets). When assuming a HR of 0.7, a median PFS of 18 months in the control arm and a median PFS of 25.7 months in the treatment arm, a two-sided alpha level of 5%, 3.5 years recruitment and 1.5 years observation time, we expect 330 events to have occurred within these 5 years in the total cohort yielding a power of 90%. Follow-up data for the whole cohort will be collected for up to 10 years and for the low-grade cancer for up to 12 years.

Discussion

The here proposed randomized phase III trial aims to identify patients with EOC in the maintenance setting, who benefit from the effectiveness of the letrozole, by proving its efficacy whilst maintaining a high standard of QoL due to the limited toxicity expected in comparison to the current alternative drugs on the market for this treatment phase.

Trial registration

This trial is registered at clinicaltrials.gov under the identifier NCT04111978. Registered 02 October 2019.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12885-022-09555-8.

Role of the Mosaic Cisternal Maturation Machinery in Glycan Synthesis and Oncogenesis

Tumorigenesis is associated with the deregulation of multiple processes, among which the glycosylation of lipids and proteins is one of the most extensively affected. However, in most cases, it remains unclear whether aberrant glycosylation is a cause, a link in the pathogenetic chain, or a mere consequence of tumorigenesis. In other cases, instead, studies have shown that aberrant glycans can promote oncogenesis. To comprehend how aberrant glycans are generated it is necessary to clarify the underlying mechanisms of glycan synthesis at the Golgi apparatus, which are still poorly understood. Important factors that determine the glycosylation potential of the Golgi apparatus are the levels and intra-Golgi localization of the glycosylation enzymes. These factors are regulated by the process of cisternal maturation which transports the cargoes through the Golgi apparatus while retaining the glycosylation enzymes in the organelle. This mechanism has till now been considered a single, house-keeping and constitutive function. Instead, we here propose that it is a mosaic of pathways, each controlling specific set of functionally related glycosylation enzymes. This changes the conception of cisternal maturation from a constitutive to a highly regulated function. In this new light, we discuss potential new groups oncogenes among the cisternal maturation machinery that can contribute to aberrant glycosylation observed in cancer cells. Further, we also discuss the prospects of novel anticancer treatments targeting the intra-Golgi trafficking process, particularly the cisternal maturation mechanism, to control/inhibit the production of pro-tumorigenic glycans.

Glycosphingolipid-Glycan Signatures of Acute Myeloid Leukemia Cell Lines Reflect Hematopoietic Differentiation

Aberrant expression of certain glycosphingolipids (GSLs) is associated with the differentiation of acute myeloid leukemia (AML) cells. However, the expression patterns of GSLs in AML are still poorly explored because of their complexity, the presence of multiple isomeric structures, and tedious analytical procedures. In this study, we performed an in-depth GSL glycan analysis of 19 AML cell lines using porous graphitized carbon liquid chromatography-mass spectrometry revealing strikingly different GSL glycan profiles between the various AML cell lines. The cell lines of the M6 subtype showed a high expression of gangliosides with α2,3-sialylation and Neu5Gc, while the M2 and M5 subtypes were characterized by high expression of (neo)lacto-series glycans and Lewis A/X antigens. Integrated analysis of glycomics and available transcriptomics data revealed the association of GSL glycan abundances with the transcriptomics expression of certain glycosyltransferases (GTs) and transcription factors (TFs). In addition, correlations were found between specific GTs and TFs. Our data reveal TFs GATA2, GATA1, and RUNX1 as candidate inducers of the expression of gangliosides and sialylation via regulation of the GTs ST3GAL2 and ST8SIA1. In conclusion, we show that GSL glycan expression levels are associated with hematopoietic AML classifications and TF and GT gene expression. Further research is needed to dissect the regulation of GSL expression and its role in hematopoiesis and associated malignancies.

Tumor targeting with bacterial Shiga toxin B-subunit in genetic porcine models for colorectal cancer and osteosarcoma

The B-subunit of bacterial Shiga toxin (STxB) is non-toxic and has low immunogenicity. Its receptor, the glycosphingolipid Gb3/CD77, is overexpressed on the cell surface of human colorectal cancer (CRC). We tested whether genetic porcine models, closely resembling human anatomy and pathophysiology, can be used to exploit the tumor targeting potential of STxB. In accordance with findings on human CRC, the pig model APC1311 bound STxB in colorectal tumors, but not in normal colon or jejunum, except for putative enteroendocrine cells. In primary tumor cells from endoscopic biopsies, STxB was rapidly taken up along the retrograde intracellular route to the Golgi, whereas normal colon organoids did not bind or internalize STxB. Next, we tested a porcine model (TP53LSL-R167H) for osteosarcoma, a tumor entity with a dismal prognosis and insufficient treatment options, hitherto not known to express Gb3. Pig osteosarcoma strongly bound StxB and expressed the Gb3-synthase A4GALT. Primary osteosarcoma cells, but not normal osteoblasts, rapidly internalized fluorescently labelled STxB along the retrograde route to the Golgi. Importantly, six out of eight human osteosarcoma cell lines expressed A4GALT mRNA and showed prominent intracellular uptake of STxB. The physiological role of A4GALT was tested by Crispr/Cas9-mutagenesis in porcine LLC-PK1 kidney epithelial cells and RNA interference in MG-63 human osteosarcoma cells. A4GALT-deficiency or knock-down abolished STxB uptake and led to significantly reduced cell migration and proliferation, hinting towards a putative tumor-promoting role of Gb3. Thus, pig models are suitable tools for STxB-based tumor targeting, and may allow "reverse-translational" predictions on human tumor biology.

Identification and Validation of Three PDAC Subtypes and Individualized GSVA Immune Pathway-Related Prognostic Risk Score Formula in Pancreatic Ductal Adenocarcinoma Patients

Background

With the progress of precision medicine treatment in pancreatic ductal adenocarcinoma (PDAC), individualized cancer-related medical examination and prediction are of great importance in this high malignant tumor and tumor-immune microenvironment with changed pathways highly enrolled in the carcinogenesis of PDAC.

Methods

High-throughput data of pancreatic ductal adenocarcinoma were downloaded from Gene Expression Omnibus (GEO) and The Cancer Genome Atlas (TCGA) database. After batch normalization, the enrichment pathway and relevant scores were identified by the enrichment of immune-related pathway signature using gene set variation analysis (GSVA). Then, cancerous subtype in TCGA and GEO samples was defined through the NMF methods by cancertypes packages in R software, respectively. Subsequently, the significance between the characteristics of each TCGA sample and cancer type and the significant prognosis-related pathway with risk score formula is calculated through t-test and univariate Cox analysis. Next, the prognostic value of gained risk score formula and each significant prognosis-related pathway were validated in TCGA and GEO samples by survival analysis. The pivotal hub genes in the enriched significant prognosis-related pathway are identified and validated, and the TIMER database was used to identify the potential role of hub genes in the PDAC immune environment. The potential role of hub genes is promoting the transdifferentiation of cancer-associated fibroblasts.

Results

The enrichment pathway and relevant scores were identified by GSVA, and 3 subtypes of pancreatic ductal adenocarcinoma were defined in TCGA and GEO samples. The clinical stage, tumor node metastasis classification, and tumor grade are strongly relative to the subtype above in TCGA samples. A risk formula about GSVA significant pathway “GSE45365_WT_VS_IFNAR_KO_CD11B_DC_MCMV_INFECTION_DN ∗ 0.80 + HALLMARK_GLYCOLYSIS ∗ 16.8 + GSE19888_CTRL_VS_T_CELL_MEMBRANES_ACT_MAST_CELL_DN ∗ 14.4” was identified and validated in TCGA and GEO samples through survival analysis with significance. DCN, VCAN, B4GALT7, SDC1, SDC2, B3GALT6, B3GAT3, SDC3, GPC1, and XYLT2 were identified as hub genes in these GSVA significant pathways and validated in silico.

Conclusions

Three pancreatic ductal adenocarcinoma subtypes are identified, and an individualized GSVA immune pathway score-related prognostic risk score formula with 10 hub genes is identified and validated. The predicted function of the 10 upregulated hub genes in tumor-immune microenvironment was promoting the infiltration of cancer-associated fibroblasts. These findings will contribute to the precision medicine of pancreatic ductal adenocarcinoma treatment and tumor immune-related basic research.

Mixed-Up Sugars: Glycosyltransferase Cross-Reactivity in Cancerous Tissues and Their Therapeutic Targeting

The main categories of glycan changes in cancer are: (1) decreased expression of histo-blood group A and/or B antigens and increased Lewis-related antigens, (2) appearance of cryptic antigens, such as Tn and T, (3) emergence of genetically incompatible glycans, such as A antigen expressed in tumors of individuals of group B or O and heterophilic expression of Forssman antigen (FORS1), and (4) appearance of neoglycans. This review focuses on the expression of genetically incompatible A/B/FORS1 antigens in cancer. Several possible molecular mechanisms are exemplified, including missense mutations that alter the sugar specificity of A and B glycosyltransferases (AT and BT, respectively), restoration of the correct codon reading frame of O alleles, and modification of acceptor specificity of AT to synthesize the FORS1 antigen by missense mutations and/or altered splicing. Taking advantage of pre-existing natural immunity, the potential uses of these glycans for immunotherapeutic targeting will also be discussed.

Gene Signatures and Prognostic Values of N6-Methyladenosine Related Genes in Ovarian Cancer

N6-Methyladenosine (m6A) is one of the most prominent modification regulating RNA processing and metabolism. Increasing studies have illuminated the vital role of m6A methylation in carcinogenesis. However, little is known about the interaction between m6A-related genes and survival of ovarian cancer (OC) patients. The purpose of this study was to obtain more reliable m6A-related genes that could be used as prognostic markers of OC using bioinformatics analysis performed on the RNA-seq data of OC. Gene expression datasets of all m6A-related genes as well as corresponding clinical data were obtained from the International Cancer Genome Consortium (ICGC) and The Cancer Genome Atlas (TCGA) databases. We detected differential expressed m6A-related candidate genes as well as their relationship and interaction. m6A RNA methylation regulator ALKBH5 and 35 m6A-related genes are dysregulated in OC. A gene set that could be used as a potential independent prognostic risk feature was further screened including NEBL, PDGFRA, WDR91, and ZBTB4. The results of mRNA expression analysis by PCR were consistent with those of bioinformatics analysis. We applied consensus clustering analysis on the expression of the four prognostic genes and obtained four OC subgroups TM1-TM4. There were significant differences in age, stage and grade among the subgroups, and the overall survival (OS) as well as Disease-free survival (DFS) of TM2 group were shorter than those of the other three groups. Further GO and KEGG enrichment analysis indicated that these differential genes were closely related to biological processes and key signaling pathways involved in OC. In summary, our study has indicated that m6A-related genes are key factors in the progression of OC and have potential effects on the prognostic stratification of OC and the development of treatment strategies.

Bioactive Compounds with Antiglioma Activity from Marine Species

The search for new chemical compounds with antitumor pharmacological activity is a necessary process for creating more effective drugs for each specific malignancy type. This review presents the outcomes of screening studies of natural compounds with high anti-glioma activity. Despite significant advances in cancer therapy, there are still some tumors currently considered completely incurable including brain gliomas. This review covers the main problems of the glioma chemotherapy including drug resistance, side effects of common anti-glioma drugs, and genetic diversity of brain tumors. The main emphasis is made on the characterization of natural compounds isolated from marine organisms because taxonomic diversity of organisms in seawaters significantly exceeds that of terrestrial species. Thus, we should expect greater chemical diversity of marine compounds and greater likelihood of finding effective molecules with antiglioma activity. The review covers at least 15 classes of organic compounds with their chemical formulas provided as well as semi-inhibitory concentrations, mechanisms of action, and pharmacokinetic profiles. In conclusion, the analysis of the taxonomic diversity of marine species containing bioactives with antiglioma activity is performed noting cytotoxicity indicators and to the tumor cells in comparison with similar indicators of antitumor agents approved for clinical use as antiglioblastoma chemotherapeutics.

Glycobiology of the Epithelial to Mesenchymal Transition

Glycosylation consists in the covalent, enzyme mediated, attachment of sugar chains to proteins and lipids. A large proportion of membrane and secreted proteins are indeed glycoproteins, while glycolipids are fundamental component of cell membranes. The biosynthesis of sugar chains is mediated by glycosyltransferases, whose level of expression represents a major factor of regulation of the glycosylation process. In cancer, glycosylation undergoes profound changes, which often contribute to invasion and metastasis. Epithelial to mesenchymal transition (EMT) is a key step in metastasis formation and is intimately associated with glycosylation changes. Numerous carbohydrate structures undergo up- or down-regulation during EMT and often regulate the process. In this review, we will discuss the relationship with EMT of the N-glycans, of the different types of O-glycans, including the classical mucin-type, O-GlcNAc, O-linked fucose, O-linked mannose and of glycolipids. Finally, we will discuss the role in EMT of galectins, a major class of mammalian galactoside-binding lectins. While the expression of specific carbohydrate structures can be used as a marker of EMT and of the propensity to migrate, the manipulation of the glycosylation machinery offers new perspectives for cancer treatment through inhibition of EMT.

Deciphering the Importance of Glycosphingolipids on Cellular and Molecular Mechanisms Associated with Epithelial-to-Mesenchymal Transition in Cancer

Every living cell is covered with a dense and complex layer of glycans on the cell surface, which have important functions in the interaction between cells and their environment. Glycosphingolipids (GSLs) are glycans linked to lipid molecules that together with sphingolipids, sterols, and proteins form plasma membrane lipid rafts that contribute to membrane integrity and provide specific recognition sites. GSLs are subdivided into three major series (globo-, ganglio-, and neolacto-series) and are synthesized in a non-template driven process by enzymes localized in the ER and Golgi apparatus. Altered glycosylation of lipids are known to be involved in tumor development and metastasis. Metastasis is frequently linked with reversible epithelial-to-mesenchymal transition (EMT), a process involved in tumor progression, and the formation of new distant metastatic sites (mesenchymal-to-epithelial transition or MET). On a single cell basis, cancer cells lose their epithelial features to gain mesenchymal characteristics via mechanisms influenced by the composition of the GSLs on the cell surface. Here, we summarize the literature on GSLs in the context of reversible and cancer-associated EMT and discuss how the modification of GSLs at the cell surface may promote this process.

Human Gb3/CD77 synthase produces P1 glycotope-capped N-glycans, which mediate Shiga toxin 1 but not Shiga toxin 2 cell entry

The human Gb3/CD77 synthase, encoded by the A4GALT gene, is an unusually promiscuous glycosyltransferase. It synthesizes the Galα1→4Gal linkage on two different glycosphingolipids (GSLs), producing globotriaosylceramide (Gb3, CD77, Pk) and the P1 antigen. Gb3 is the major receptor for Shiga toxins (Stxs) produced by enterohemorrhagic Escherichia coli. A single amino acid substitution (p.Q211E) ramps up the enzyme's promiscuity, rendering it able to attach Gal both to another Gal residue and to GalNAc, giving rise to NOR1 and NOR2 GSLs. Human Gb3/CD77 synthase was long believed to transfer Gal only to GSL acceptors, therefore its GSL products were, by default, considered the only human Stx receptors. Here, using soluble, recombinant human Gb3/CD77 synthase and p.Q211E mutein, we demonstrate that both enzymes can synthesize the P1 glycotope (terminal Galα1→4Galβ1→4GlcNAc-R) on a complex type N-glycan and a synthetic N-glycoprotein (saposin D). Moreover, by transfection of CHO-Lec2 cells with vectors encoding human Gb3/CD77 synthase and its p.Q211E mutein, we demonstrate that both enzymes produce P1 glycotopes on N-glycoproteins, with the mutein exhibiting elevated activity. These P1-terminated N-glycoproteins are recognized by Stx1 but not Stx2 B subunits. Finally, cytotoxicity assays show that Stx1 can use P1 N-glycoproteins produced in CHO-Lec2 cells as functional receptors. We conclude that Stx1 can recognize and use P1 N-glycoproteins in addition to its canonical GSL receptors to enter and kill the cells, while Stx2 can use GSLs only. Collectively, these results may have important implications for our understanding of the Shiga toxin pathology.

Comparative Analysis of Cell-Cell Contact Abundance in Ovarian Carcinoma Cells Cultured in Two- and Three-Dimensional In Vitro Models

Simple Summary

Tumor resistance to therapy is a crucial problem of today’s oncology. The emerging data indicate that tumor microenvironment is the key participant in the resistance development. One of the most basic aspect of tumor microenvironment is intercellular adhesion. Our data obtained using monolayer culture, matrix-free and matrix-based three-dimensional in vitro models indicate that the abundance of cell-cell contact proteins is varying depending on the microenvironment. These differences coincided with the degree of the resistance to therapeutics. The importance of adhesion proteins in tumor resistance may provide the fundamental basis for improving cancer treatment approaches and must be taken into account when screening candidate drugs.

Abstract

Tumor resistance to therapy is associated with the 3D organization and peculiarities of the tumor microenvironment, of which intercellular adhesion is a key participant. In this work, the abundance of contact proteins was compared in SKOV-3 and SKOV-3.ip human ovarian adenocarcinoma cell lines, cultivated in monolayers, tumor spheroids and collagen hydrogels. Three-dimensional models were characterized by extremely low expression of basic molecules of adherens junctions E-cadherin and demonstrated a simultaneous decrease in desmosomal protein desmoglein-2, gap junction protein connexin-43 and tight junction proteins occludin and ZO-1. The reduction in the level of contact proteins was most pronounced in collagen hydrogel, accompanied by significantly increased resistance to treatment with doxorubicin and targeted anticancer toxin DARPin-LoPE. Thus, we suggest that 3D models of ovarian cancer, especially matrix-based models, tend to recapitulate tumor microenvironment and treatment responsiveness to a greater extent than monolayer culture, so they can be used as a highly relevant platform for drug efficiency evaluation.

The impact of the RASSF1C and PIWIL1 on DNA methylation: the identification of GMIP as a tumor suppressor

INTRODUCTION

Recently we have identified a novel RASSF1C-PIWIL1-piRNA pathway that promotes lung cancer cell progression and migration. PIWI-like proteins interact with piRNAs to form complexes that regulate gene expression at the transcriptional and translational levels. We have illustrated in previous work that RASSF1C modulates the expression of the PIWIL1-piRNA gene axis, suggesting the hypothesis that the RASSF1C-PIWI-piRNA pathway could potentially contribute to lung cancer stem cell development and progression, in part, through modulation of gene methylation of both oncogenic and tumor suppressor genes. Therefore, we tested this hypothesis using a non-small cell lung cancer (NSCLC) cell model to identify Candidate Differentially Methylated Regions (DMRs) modulated by the RASSF1C-PIWIL1-piRNA pathway.

MATERIALS AND METHODS

We studied the impact of over-expressing RASSF1C and knocking down RASSF1C and PIWIL1 expression on global gene DNA methylation in the NSCLC cell line H1299 using the Reduced Representation Bisulfite Sequencing (RRBS) method.

RESULTS

DMRs were identified by comparing DNA methylation profiles of experimental and control cells. Over-expression of RASSF1C and knocking down RASSF1C and PIWIL1 modulated DNA methylation of genomic regions; and statistically significant candidate genes residing DMR regions in lung cancer cells were identified, including oncogenes and tumor suppressors. One of the hypermethylated genes, Gem Interacting Protein (GMIP), displays tumor suppressor properties. GMIP expression attenuates lung cancer cell migration, and its over-expression is associated with longer survival of lung cancer patients.

CONCLUSIONS

The RASSF1C-PIWI-piRNA pathway modulates key oncogenes and tumor suppressor genes. GMIP is hypermethylated by this pathway and has tumor suppressor properties.

Collagen-rich omentum is a premetastatic niche for integrin α2-mediated peritoneal metastasis

The extracellular matrix (ECM) plays critical roles in tumor progression and metastasis. However, the contribution of ECM proteins to early metastatic onset in the peritoneal cavity remains unexplored. Here, we suggest a new route of metastasis through the interaction of integrin alpha 2 (ITGA2) with collagens enriched in the tumor coinciding with poor outcome in patients with ovarian cancer. Using multiple gene-edited cell lines and patient-derived samples, we demonstrate that ITGA2 triggers cancer cell adhesion to collagen, promotes cell migration, anoikis resistance, mesothelial clearance, and peritoneal metastasis in vitro and in vivo. Mechanistically, phosphoproteomics identify an ITGA2-dependent phosphorylation of focal adhesion kinase and mitogen-activated protein kinase pathway leading to enhanced oncogenic properties. Consequently, specific inhibition of ITGA2-mediated cancer cell-collagen interaction or targeting focal adhesion signaling may present an opportunity for therapeutic intervention of metastatic spread in ovarian cancer.

S1P Lyase siRNA Dampens Malignancy of DLD-1 Colorectal Cancer Cells

Sphingosine-1-phosphate lyase 1 (S1P lyase or SGPL1) is an essential sphingosine-1-phosphate-degrading enzyme. Its manipulation favors onset and progression of colorectal cancer and others in vivo. Thus, SGPL1 is an important modulator of cancer initiation. However, in established cancer, the impact of retrospective SGPL1 modulation is elusive. Herein, we analyzed how SGPL1 siRNA affects malignancy of the human colorectal cancer cells DLD-1 and found that in parallel to the reduction of SGPL1 expression levels, migration, invasion, and differentiation status changed. Diminished SGPL1 expression was accompanied with reduced cell migration and cell invasion in scratch assays and transwell assays, whereas metabolic activity and proliferation was not altered. Decreased migration was attended by increased cell-cell-adhesion through upregulation of E-cadherin and formation of cadherin-actin complexes. Spreading cell islets showed lower vimentin abundance in border cells. Furthermore, SGPL1 siRNA treatment induced expression of epithelial cell differentiation markers, such as intestinal alkaline phosphatase and cytokeratin 20. Hence, interference with SGPL1 expression augmented a partial redifferentiation of colorectal cancer cells toward normal colon epithelial cells. Our investigation showed that SGPL1 siRNA influenced tumorigenic activity of established colorectal cancer cells. We therefore suggest SGPL1 as a target for lowering malignant potential of already existing cancer.

Glycosphingolipid expression at breast cancer stem cells after novel thieno[2,3-b]pyridine anticancer compound treatment

Glycosphingolipid expression differs between human breast cancer stem cells (CSC) and cancer non-stem cells (non-CSC). We performed studies of viability, type of cell death, cancer stem cell percent and glycosphingolipid expression on CSC and non-CSC after treatment of MDA-MB-231 and MDA-MB-453 triple-negative breast cancer cells with a newly developed thienopyridine anticancer compound (3-amino-N-(3-chloro-2-methylphenyl)-5-oxo-5,6,7,8-tetrahydrothieno[2,3-b]quinoline-2-carboxamide, 1). Compound 1 was cytotoxic for both breast cancer cell lines and the majority of cells died by treatment-induced apoptosis. The percent of cancer stem cells and number of formed mammospheres was significantly lower. Glycosphingolipids IV⁶Neu5Ac-nLc₄Cer and GalNAc-GM1b (IV³Neu5Ac-Gg5Cer) not reported previously, were identified in both CSCs and non-CSCs. IV⁶Neu5Ac-nLc₄Cer had increased expression in both CSCs and non-CSCs of both cell lines after the treatment with 1, while GM3 (II³Neu5Ac-LacCer) had increased expression only on both cell subpopulations in MDA-MB-231 cell line. GalNAc-GM1b, Gb₄Cer (GalNAcβ1-3Galα1-4Galβ1-4Glcβ1-1Cer) and GM2 (II³Neu5Ac-GalNAcβ1-4Galβ1-4Glcβ1-1Cer) were increased only in CSCs of both cell lines while GD3 was decreased in CSC of MDA-MB-231 cell line. Due to its effect in reducing the percentage of cancer stem cells and number of mammospheres, and its influence upon several glycosphingolipid expressions, it can be concluded that compound 1 deserves attention as a potential new drug for triple-negative breast cancer therapy.

MALDI-2 Mass Spectrometry and Immunohistochemistry Imaging of Gb3Cer, Gb4Cer, and Further Glycosphingolipids in Human Colorectal Cancer Tissue

The main cellular receptors of Shiga toxins (Stxs), the neutral glycosphingolipids (GSLs), globotriaosylceramide (Gb3Cer/CD77) and globotetraosylceramide (Gb4Cer), are significantly upregulated in about half of the human colorectal carcinomas (CRC) and in other cancers. Therefore, conjugates exploiting the Gb3Cer/Gb4Cer-binding B subunit of Stx (StxB) have attracted great interest for both diagnostic and adjuvant therapeutic interventions. Moreover, fucosylated GSLs were recognized as potential tumor-associated targets. One obstacle to a broader use of these receptor/ligand systems is that the contribution of specific GSLs to tumorigenesis, in particular, in the context of an altered lipid metabolism, is only poorly understood. A second is that also nondiseased organs (e.g., kidney) and blood vessels can express high levels of certain GSLs, not least Gb3Cer/Gb4Cer. Here, we used, in a proof-of-concept study, matrix-assisted laser desorption/ionization mass spectrometry imaging combined with laser-induced postionization (MALDI-2-MSI) to simultaneously visualize the distribution of several Gb3Cer/Gb4Cer lipoforms and those of related GSLs (e.g., Gb3Cer/Gb4Cer precursors and fucosylated GSLs) in tissue biopsies from three CRC patients. Using MALDI-2 and StxB-based immunofluorescence microscopy, Gb3Cer and Gb4Cer were mainly found in dedifferentiated tumor cell areas, tumor stroma, and tumor-infiltrating blood vessels. Notably, fucosylated GSL such as Fuc-(n)Lc4Cer generally showed a highly localized expression in dysplastic glands and indian file-like cells infiltrating adipose tissue. Our "molecular histology" approach could support stratifying patients for intratumoral GSL expression to identify an optimal therapeutic strategy. The improved chemical coverage by MALDI-2 can also help to improve our understanding of the molecular basis of tumor development and GSL metabolism.

Are Glucosylceramide-Related Sphingolipids Involved in the Increased Risk for Cancer in Gaucher Disease Patients? Review and Hypotheses

The roles of ceramide and its catabolites, i.e., sphingosine and sphingosine 1-phosphate, in the development of malignancies and the response to anticancer regimens have been extensively described. Moreover, an abundant literature points to the effects of glucosylceramide synthase, the mammalian enzyme that converts ceramide to β-glucosylceramide, in protecting tumor cells from chemotherapy. Much less is known about the contribution of β-glucosylceramide and its breakdown products in cancer progression. In this chapter, we first review published and personal clinical observations that report on the increased risk of developing cancers in patients affected with Gaucher disease, an inborn disorder characterized by defective lysosomal degradation of β-glucosylceramide. The previously described mechanistic links between lysosomal β-glucosylceramidase, β-glucosylceramide and/or β-glucosylphingosine, and various hallmarks of cancer are reviewed. We further show that melanoma tumor growth is facilitated in a Gaucher disease mouse model. Finally, the potential roles of the β-glucosylceramidase protein and its lipidic substrates and/or downstream products are discussed.

L1 Cell Adhesion Molecule Confers Radioresistance to Ovarian Cancer and Defines a New Cancer Stem Cell Population

Many solid tumors, including ovarian cancer, contain small populations of cancer stem cells (CSCs). These cells are usually resistant against conventional cancer therapies and play a role in disease recurrence. We demonstrated that the L1 cell adhesion molecule (L1CAM) is a new CSC target in ovarian cancer, triggering radioresistance. Using fluorescence-activated cell sorting, specific cell populations expressing L1CAM alone or in combination with the established CSC marker CD133 were isolated from three ovarian cancer cell lines. Double-positive L1CAM+/CD133+ cells displayed higher spherogenic and clonogenic properties in comparison to L1CAM-/CD133- cells. Furthermore, L1CAM+/CD133+ cells retained highest clonogenic capacity after irradiation and exhibited up-regulation of some CSC-specific genes, enhanced tumor-initiating capacity, self-renewal and higher tumor take rate in nude mice when compared with other cell populations. Superior radioresistance by L1CAM expression was confirmed by deletion of L1CAM using CRISPR-Cas9 technology. Moreover, we found expression signatures associated with epithelial-to-mesenchymal transition phenotype in L1CAM deleted cells. These results indicate that L1CAM in combination with CD133 defines a new cancer cell population of ovarian tumor-initiating cells with the implication of targeting L1CAM as a novel therapeutic approach for ovarian CSCs.

Outcome in serous ovarian cancer is not associated with LATS expression

Background

Large tumor suppressor (LATS) proteins are putative tumor suppressors and poorly expressed associated with poor outcome in many cancers. A recent immunohistochemistry study showed that LATS protein expression correlated with poor outcome in serous ovarian cancer.

Materials and methods

We analyzed LATS expression in various ovarian cancer transcriptomic data sets and immunohistochemically assessed LATS protein expression in a Swiss ovarian tumor cohort. Results were compared to clinicopathological characteristics and outcome. We also compared LATS protein expression in serous ovarian cancer cell lines to their EMT status (Western blotting) and drug sensitivity (MTT assay).

Results

The analysis of 15 different transcriptomic data sets showed that LATS2 was associated with poorer outcome, while LATS1 was irrelevant (HR = 1.19 and HR = 1.00, respectively). The TCGA-RNASeqV2 data set showed that low LATS1 and LATS2 were associated with better survival in serous ovarian carcinoma. Despite heterogeneity among the different data sets, LATS expression is not an indicator of survival in serous ovarian cancer and LATS2 expression may even be tumorigenic. LATS expression was neither associated with survival nor with the stage and grade in the Swiss cohort. It was low in cystadenoma, intermediate in carcinoma, and high in borderline tumors and was higher in serous than mucinous ovarian carcinoma. LATS protein expression extent was comparable in epithelial-, intermediate-, and mesenchymal-type ovarian cancer cells and was not associated with drug sensitivity.

Conclusion

These results are largely incompatible with a tumor-suppressive function of LATS in ovarian cancer, and LATS protein level is also not an indicator for drug sensitivity and EMT status of ovarian cancer cells.

Glycosylation in the Era of Cancer-Targeted Therapy: Where Are We Heading?

This review provides insights on the impact of glycosylation in cancer biology and its influence in the current approaches of targeted cancer therapies in the clinical setting. The roles of glycosylation in cancer signaling, tumor progression, and metastasis are reviewed as well as glycans and glycan-binding proteins in tumor immunomodulation. Moreover, the latest reports on glycans influencing targeted therapeutic approaches in cancer are summarized. Finally, we discuss the future challenges of the field, outlining potential applications of glycan-based biomarkers for patient stratification and strategies for improving personalized cancer treatment.

Zebrafish Xenografts for the In Vivo Analysis of Healthy and Malignant Human Hematopoietic Cells

The zebrafish is a powerful vertebrate model for genetic studies on embryonic development and organogenesis. In the last decades, zebrafish were furthermore increasingly used for disease modeling and investigation of cancer biology. Zebrafish are particularly used for mutagenesis and small molecule screens, as well as for live imaging assays that provide unique opportunities to monitor cell behavior, both on a single cell and whole organism level in real time. Zebrafish have been also used for in vivo investigations of human cells transplanted into embryos or adult animals; this zebrafish xenograft model can be considered as an intermediate assay between in vitro techniques and more time-consuming and expensive mammalian models.Here, we present a protocol for transplantation of healthy and malignant human hematopoietic cells into larval zebrafish; transplantation into adult zebrafish and possible advantages and limitations of the zebrafish compared to murine xenograft models are discussed.