Stemness underpinning all steps of human colorectal cancer defines the core of effective therapeutic strategies

Different states of stemness of glioblastoma stem cells sustain glioblastoma subtypes indicating novel clinical biomarkers and high-efficacy customized therapies

BACKGROUND

Glioblastoma (GBM) is the most malignant among gliomas with an inevitable lethal outcome. The elucidation of the physiology and regulation of this tumor is mandatory to unravel novel target and effective therapeutics. Emerging concepts show that the minor subset of glioblastoma stem cells (GSCs) accounts for tumorigenicity, representing the true target for innovative therapies in GBM.

METHODS

Here, we isolated and established functionally stable and steadily expanding GSCs lines from a large cohort of GBM patients. The molecular, functional and antigenic landscape of GBM tissues and their derivative GSCs was highlited in a side-by-side comprehensive genomic and transcriptomic characterization by ANOVA and Fisher's exact tests. GSCs' physio-pathological hallmarks were delineated by comparing over time in vitro and in vivo their expansion, self-renewal and tumorigenic ability with hierarchical linear models for repeated measurements and Kaplan-Meier method. Candidate biomarkers performance in discriminating GBM patients' classification emerged by classification tree and patients' survival analysis.

RESULTS

Here, distinct biomarker signatures together with aberrant functional programs were shown to stratify GBM patients as well as their sibling GSCs population into TCGA clusters. Of importance, GSCs cells were demonstrated to fully resemble over time the molecular features of their patient of origin. Furthermore, we pointed out the existence of distinct GSCs subsets within GBM classification, inherently endowed with different self-renewal and tumorigenic potential. Particularly, classical GSCs were identified by more undifferentiated biological hallmarks, enhanced expansion and clonal capacity as compared to the more mature, relatively slow-propagating mesenchymal and proneural cells, likely endowed with a higher potential for infiltration either ex vivo or in vivo. Importantly, the combination of DCX and EGFR markers, selectively enriched among GSCs pools, almost exactly predicted GBM patients' clusters together with their survival and drug response.

CONCLUSIONS

In this study we report that an inherent enrichment of distinct GSCs pools underpin the functional inter-cluster variances displayed by GBM patients. We uncover two selectively represented novel functional biomarkers capable of discriminating GBM patients' stratification, survival and drug response, setting the stage for the determination of patient-tailored diagnostic and prognostic strategies and, mostly, for the design of appropriate, patient-selective treatment protocols.

Settling the uncertainty about unconventional circulating tumor cells: Epithelial-to-mesenchymal transition, cell fusion and trogocytosis

Circulating tumor cells (CTCs) were first described 150 years ago. The so-called "classical" CTC populations (EpCAM+/CK+/CD45-) have been fully characterized and proposed as the most representative CTC subset, with clinical relevance. Nonetheless, other "atypical" or "unconventional" CTCs have also been identified, and their critical role in metastasis formation was demonstrated. In this chapter we illustrate the studies that led to the discovery of unconventional CTCs, defined as CTCs that display both epithelial and mesenchymal markers, or both cancer and immune markers, also in the form of hybrid cancer-immune cells. We also present biological explanations for the origin of these unconventional CTCs: epithelial to mesenchymal transition, cell-cell fusion and trogocytosis. We believe that a deeper knowledge on the biology of CTCs is needed to fully elucidate their role in cancer progression and their use as cancer biomarkers.

1'-O-methyl-averantin isolated from the endolichenic fungus Jackrogersella sp. EL001672 suppresses colorectal cancer stemness via sonic Hedgehog and Notch signaling

Endolichenic fungi are host organisms that live on lichens and produce a wide variety of secondary metabolites. Colorectal cancer stem cells are capable of self-renewal and differentiation into cancer cells, which makes cancers difficult to eradicate. New alternative therapeutics are needed to inhibit the growth of tumor stem cells. This study examined the ability of an extract of Jackrogersella sp. EL001672 (derived from the lichen Cetraria sp.) and the isolated compound 1'-O-methyl-averantin to inhibit development of cancer stemness. The endolichenic fungus Jackrogersella sp. EL001672 (KACC 83021BP), derived from Cetraria sp., was grown in culture medium. The culture broth was extracted with acetone to obtain a crude extract. Column chromatography and reverse-phase HPLC were used to isolate an active compound. The anticancer activity of the extract and the isolated compound was evaluated by qRT-PCR and western blotting, and in cell viability, spheroid formation, and reporter assays. The acetone extract of EL001672 did not affect cell viability. However, 1'-O-methyl-averantin showed cytotoxic effects against cancer cell lines at 50 μg/mL and 25 μg/mL. Both the crude extract and 1'-O-methyl-averantin suppressed spheroid formation in CRC cell lines, and downregulated expression of stemness markers ALDH1, CD44, CD133, Lgr-5, Msi-1, and EphB1. To further characterize the mechanism underlying anti-stemness activity, we examined sonic Hedgehog and Notch signaling. The results showed that the crude extract and the 1'-O-methyl-averantin inhibited Gli1, Gli2, SMO, Bmi-1, Notch-1, Hes-1, and the CSL complex. Consequently, an acetone extract and 1'-O-methyl-averantin isolated from EL001672 suppresses colorectal cancer stemness by regulating the sonic Hedgehog and Notch signaling pathways.

Patient-derived xenograft model in colorectal cancer basic and translational research

Colorectal cancer (CRC) is one of the most popular malignancies globally, with 930 000 deaths in 2020. The evaluation of CRC-related pathogenesis and the discovery of potential therapeutic targets will be meaningful and helpful for improving CRC treatment. With huge efforts made in past decades, the systematic treatment regimens have been applied to improve the prognosis of CRC patients. However, the sensitivity of CRC to chemotherapy and targeted therapy is different from person to person, which is an important cause of treatment failure. The emergence of patient-derived xenograft (PDX) models shows great potential to alleviate the straits. PDX models possess similar genetic and pathological characteristics as the features of primary tumors. Moreover, PDX has the ability to mimic the tumor microenvironment of the original tumor. Thus, the PDX model is an important tool to screen precise drugs for individualized treatment, seek predictive biomarkers for prognosis supervision, and evaluate the unknown mechanism in basic research. This paper reviews the recent advances in constructed methods and applications of the CRC PDX model, aiming to provide new knowledge for CRC basic research and therapeutics.

Growth factor independence underpins a paroxysmal, aggressive Wnt5aHigh/EphA2Low phenotype in glioblastoma stem cells, conducive to experimental combinatorial therapy

Background

Glioblastoma multiforme (GBM) is an incurable tumor, with a median survival rate of only 14–15 months. Along with heterogeneity and unregulated growth, a central matter in dealing with GBMs is cell invasiveness. Thus, improving prognosis requires finding new agents to inhibit key multiple pathways, even simultaneously. A subset of GBM stem-like cells (GSCs) may account for tumorigenicity, representing, through their pathways, the proper cellular target in the therapeutics of glioblastomas. GSCs cells are routinely enriched and expanded due to continuous exposure to specific growth factors, which might alter some of their intrinsic characteristic and hide therapeutically relevant traits.

Methods

By removing exogenous growth factors stimulation, here we isolated and characterized a subset of GSCs with a “mitogen-independent” phenotype (I-GSCs) from patient’s tumor specimens. Differential side-by-side comparative functional and molecular analyses were performed either in vitro or in vivo on these cells versus their classical growth factor (GF)-dependent counterpart (D-GSCs) as well as their tissue of origin. This was performed to pinpoint the inherent GSCs’ critical regulators, with particular emphasis on those involved in spreading and tumorigenic potential. Transcriptomic fingerprints were pointed out by ANOVA with Benjamini-Hochberg False Discovery Rate (FDR) and association of copy number alterations or somatic mutations was determined by comparing each subgroup with a two-tailed Fisher’s exact test. The combined effects of interacting in vitro and in vivo with two emerging GSCs’ key regulators, such as Wnt5a and EphA2, were then predicted under in vivo experimental settings that are conducive to clinical applications. In vivo comparisons were carried out in mouse-human xenografts GBM model by a hierarchical linear model for repeated measurements and Dunnett’s multiple comparison test with the distribution of survival compared by Kaplan–Meier method.

Results

Here, we assessed that a subset of GSCs from high-grade gliomas is self-sufficient in the activation of regulatory growth signaling. Furthermore, while constitutively present within the same GBM tissue, these GF-independent GSCs cells were endowed with a distinctive functional and molecular repertoire, defined by highly aggressive Wnt5aHigh/EphA2Low profile, as opposed to Wnt5aLow/EphA2High expression in sibling D-GSCs. Regardless of their GBM subtype of origin, I-GSCs, are endowed with a raised in vivo tumorigenic potential than matched D-GSCs, which were fast-growing ex-vivo but less lethal and invasive in vivo. Also, the malignant I-GSCs’ transcriptomic fingerprint faithfully mirrored the original tumor, bringing into evidence key regulators of invasiveness, angiogenesis and immuno-modulators, which became candidates for glioma diagnostic/prognostic markers and therapeutic targets. Particularly, simultaneously counteracting the activity of the tissue invasive mediator Wnt5a and EphA2 tyrosine kinase receptor addictively hindered GSCs’ tumorigenic and invasive ability, thus increasing survival.

Conclusion

We show how the preservation of a mitogen-independent phenotype in GSCs plays a central role in determining the exacerbated tumorigenic and high mobility features distinctive of GBM. The exploitation of the I-GSCs' peculiar features shown here offers new ways to identify novel, GSCs-specific effectors, whose modulation can be used in order to identify novel, potential molecular therapeutic targets. Furthermore, we show how the combined use of PepA, the anti-Wnt5a drug, and of ephrinA1-Fc to can hinder GSCs’ lethality in a clinically relevant xenogeneic in vivo model thus being conducive to perspective, novel combinatorial clinical application.

Connexin46 Expression Enhances Cancer Stem Cell and Epithelial-to-Mesenchymal Transition Characteristics of Human Breast Cancer MCF-7 Cells

Connexins (Cxs) are a family of proteins that form two different types of ion channels: hemichannels and gap junction channels. These channels participate in cellular communication, enabling them to share information and act as a synchronized syncytium. This cellular communication has been considered a strong tumor suppressor, but it is now recognized that some type of Cxs can be pro-tumorigenic. For example, Cx46 expression is increased in human breast cancer samples and correlates with cancer stem cell (CSC) characteristics in human glioma. Thus, we explored whether Cx46 and glioma cells, can set up CSC and epithelial-to-mesenchymal transition (EMT) properties in a breast cancer cell line. To this end, we transfected MCF-7 cells with Cx46 attached to a green fluorescent protein (Cx46GFP), and we determined how its expression orchestrates both the gene-expression and functional changes associated with CSC and EMT. We observed that Cx46GFP increased Sox2, Nanog, and OCT4 mRNA levels associated with a high capacity to form monoclonal colonies and tumorspheres. Similarly, Cx46GFP increased the mRNA levels of n-cadherin, Vimentin, Snail and Zeb1 to a higher migratory and invasive capacity. Furthermore, Cx46GFP transfected in MCF-7 cells induced the release of higher amounts of VEGF, which promoted angiogenesis in HUVEC cells. We demonstrated for the first time that Cx46 modulates CSC and EMT properties in breast cancer cells and thus could be relevant in the design of future cancer therapies.

Patient-derived tumor models: a more suitable tool for pre-clinical studies in colorectal cancer

Colorectal cancer (CRC), despite the advances in screening and surveillance, remains the second most common cause of cancer death worldwide. The biological inadequacy of pre-clinical models to fully recapitulate the multifactorial etiology and the complexity of tumor microenvironment and human CRC's genetic heterogeneity has limited cancer treatment development. This has led to the development of Patient-derived models able to phenocopy as much as possible the original inter- and intra-tumor heterogeneity of CRC, reflecting the tumor microenvironment's cellular interactions. Implantation of patient tissue into immunodeficient mice hosts and the culture of tumor organoids have allowed advances in cancer biology and metastasis. This review highlights the advantages and limits of Patient-derived models as innovative and valuable pre-clinical tools to study progression and metastasis of CRC, develop novel therapeutic strategies by creating a drug screening platform, and predict the efficacy of clinical response to therapy.

BRAFV600E mutation impinges on gut microbial markers defining novel biomarkers for serrated colorectal cancer effective therapies

BACKGROUND

Colorectal cancer (CRC) harboring BRAF^V600E mutation exhibits low response to conventional therapy and poorest prognosis. Due to the emerging correlation between gut microbiota and CRC carcinogenesis, we investigated in serrated BRAF^V600E cases the existence of a peculiar fecal microbial fingerprint and specific bacterial markers, which might represent a tool for the development of more effective clinical strategies.

METHODS

By injecting human CRC stem-like cells isolated from BRAF^V600E patients in immunocompromised mice, we described a new xenogeneic model of this subtype of CRC. By performing bacterial 16S rRNA sequencing, the fecal microbiota profile was then investigated either in CRC-carrying mice or in a cohort of human CRC subjects. The microbial communities' functional profile was also predicted. Data were compared with Mann-Whitney U, Welch's t-test for unequal variances and Kruskal-Wallis test with Benjamini-Hochberg false discovery rate (FDR) correction, extracted as potential BRAF class biomarkers and selected as model features. The obtained mean test prediction scores were subjected to Receiver Operating characteristic (ROC) analysis. To discriminate the BRAF status, a Random Forest classifier (RF) was employed.

RESULTS

A specific microbial signature distinctive for BRAF status emerged, being the BRAF-mutated cases closer to healthy controls than BRAF wild-type counterpart. In agreement, a considerable score of correlation was also pointed out between bacteria abundance from BRAF-mutated cases and the level of markers distinctive of BRAF^V600E pathway, including those involved in inflammation, innate immune response and epithelial-mesenchymal transition. We provide evidence that two candidate bacterial markers, Prevotella enoeca and Ruthenibacterium lactatiformans, more abundant in BRAF^V600E and BRAF wild-type subjects respectively, emerged as single factors with the best performance in distinguishing BRAF status (AUROC = 0.72 and 0.74, respectively, 95% confidence interval). Furthermore, the combination of the 10 differentially represented microorganisms between the two groups improved performance in discriminating serrated CRC driven by BRAF mutation from BRAF wild-type CRC cases (AUROC = 0.85, 95% confidence interval, 0.69-1.01).

CONCLUSION

Overall, our results suggest that BRAF^V600E mutation itself drives a distinctive gut microbiota signature and provide predictive CRC-associated bacterial biomarkers able to discriminate BRAF status in CRC patients and, thus, useful to devise non-invasive patient-selective diagnostic strategies and patient-tailored optimized therapies.

Chemical compound cinobufotalin potently induces FOXO1-stimulated cisplatin sensitivity by antagonizing its binding partner MYH9

In this study, we present novel molecular mechanisms by which FOXO1 functions as a tumor suppressor to prevent the pathogenesis of nasopharyngeal carcinoma (NPC). First, we observed that FOXO1 not only controlled tumor stemness and metastasis, but also sensitized NPC cells to cisplatin (DDP) in vitro and in vivo. Mechanistic studies demonstrated that FOXO1-induced miR-200b expression through the GSK3β/β-catenin/TCF4 network-mediated stimulation of ZEB1, which reduced tumor stemness and the epithelial-mesenchymal transition (EMT) signal. Furthermore, we observed FOXO1 interaction with MYH9 and suppression of MYH9 expression by modulating the PI3K/AKT/c-Myc/P53/miR-133a-3p pathway. Decreased MYH9 expression not only reduced its interactions with GSK3β, but also attenuated TRAF6 expression, which then decreased the ubiquitin-mediated degradation of GSK3β protein. Increased GSK3β expression stimulated the β-catenin/TCF4/ZEB1/miR-200b network, which increased the downstream tumor stemness and EMT signals. Subsequently, we observed that chemically synthesized cinobufotalin (CB) strongly increased FOXO1-induced DDP chemosensitivity by reducing MYH9 expression, and the reduction in MYH9 modulated GSK3β/β-catenin and its downstream tumor stemness and EMT signal in NPC. In clinical samples, the combination of low FOXO1 expression and high MYH9 expression indicated the worst overall survival rates. Our studies demonstrated that CB potently induced FOXO1-mediated DDP sensitivity by antagonizing its binding partner MYH9 to modulate tumor stemness in NPC.