Multiple Interactions Between Cancer Cells and the Tumor Microenvironment Modulate TRAIL Signaling:Implications for TRAIL Receptor Targeted Therapy

Tumor necrosis factor (TNF) related apoptosis-inducing ligand (TRAIL) signaling is far more complex than initially anticipated and can lead to either anti- or protumorigenic effects, hampering the successful clinical use of therapeutic TRAIL receptor agonists. Cell autonomous resistance mechanisms have been identified in addition to paracrine factors that can modulate apoptosis sensitivity. The tumor microenvironment (TME), consisting of cellular and non-cellular components, is a source for multiple signals that are able to modulate TRAIL signaling in tumor and stromal cells. Particularly immune effector cells, also part of the TME, employ the TRAIL/TRAIL-R system whereby cell surface expressed TRAIL can activate apoptosis via TRAIL receptors on tumor cells, which is part of tumor immune surveillance. In this review we aim to dissect the impact of the TME on signaling induced by endogenous and exogenous/therapeutic TRAIL, thereby distinguishing different components of the TME such as immune effector cells, neutrophils, macrophages, and non-hematopoietic stromal cells. In addition, also non-cellular biochemical and biophysical properties of the TME are considered including mechanical stress, acidity, hypoxia, and glucose deprivation. Available literature thus far indicates that tumor-TME interactions are complex and often bidirectional leading to tumor-enhancing or tumor-reducing effects in a tumor model- and tumor type-dependent fashion. Multiple signals originating from different components of the TME simultaneously affect TRAIL receptor signaling. We conclude that in order to unleash the full clinical potential of TRAIL receptor agonists it will be necessary to increase our understanding of the contribution of different TME components on outcome of therapeutic TRAIL receptor activation in order to identify the most critical mechanism responsible for resistance, allowing the design of effective combination treatments

EMT- and MET-related processes in nonepithelial tumors:Importance for disease progression, prognosis, and therapeutic opportunities

The epithelial-to mesenchymal (EMT) process is increasingly recognized for playing a key role in the progression, dissemination, and therapy resistance of epithelial tumors. Accumulating evidence suggests that EMT inducers also lead to a gain in mesenchymal properties and promote malignancy of nonepithelial tumors. In this review, we present and discuss current findings, illustrating the importance of EMT inducers in tumors originating from nonepithelial/mesenchymal tissues, including brain tumors, hematopoietic malignancies, and sarcomas. Among these tumors, the involvement of mesenchymal transition has been most extensively investigated in glioblastoma, providing proof for cell autonomous and microenvironment-derived stimuli that provoke EMT-like processes that regulate stem cell, invasive, and immunogenic properties as well as therapy resistance. The involvement of prominent EMT transcription factor families, such as TWIST, SNAI, and ZEB, in promoting therapy resistance and tumor aggressiveness has also been reported in lymphomas, leukemias, and sarcomas. A reverse process, resembling mesenchymal-to-epithelial transition (MET), seems particularly relevant for sarcomas, where (partial) epithelial differentiation is linked to less aggressive tumors and a better patient prognosis. Overall, a hybrid model in which more stable epithelial and mesenchymal intermediates exist likely extends to the biology of tumors originating from sources other than the epithelium. Deeper investigation and understanding of the EMT/ PMET machinery in nonepithelial tumors will shed light on the pathogenesis of these tumors, potentially paving the way toward the identification of clinically relevant biomarkers for prognosis and future therapeutic targets

Understanding Lung Carcinogenesis from a Morphostatic Perspective:Prevention and Therapeutic Potential of Phytochemicals for Targeting Cancer Stem Cells

Lung cancer is still one of the deadliest cancers, with over two million incidences annually. Prevention is regarded as the most efficient way to reduce both the incidence and death figures. Nevertheless, treatment should still be improved, particularly in addressing therapeutic resistance due to cancer stem cells—the assumed drivers of tumor initiation and progression. Phytochemicals in plant-based diets are thought to contribute substantially to lung cancer prevention and may be efficacious for targeting lung cancer stem cells. In this review, we collect recent literature on lung homeostasis, carcinogenesis, and phytochemicals studied in lung cancers. We provide a comprehensive overview of how normal lung tissue operates and relate it with lung carcinogenesis to redefine better targets for lung cancer stem cells. Nine well-studied phytochemical compounds, namely curcumin, resveratrol, quercetin, epigallocatechin-3-gallate, luteolin, sulforaphane, berberine, genistein, and capsaicin, are discussed in terms of their chemopreventive and anticancer mechanisms in lung cancer and potential use in the clinic. How the use of phytochemicals can be improved by structural manipulations, targeted delivery, concentration adjustments, and combinatorial treatments is also highlighted. We propose that lung carcinomas should be treated differently based on their respective cellular origins. Targeting quiescence-inducing, inflammation-dampening, or reactive oxygen species-balancing pathways appears particularly interesting

Physics of Brain Cancer:Multiscale Alterations of Glioblastoma Cells under Extracellular Matrix Stiffening

The biology and physics underlying glioblastoma is not yet completely understood, resulting in the limited efficacy of current clinical therapy. Recent studies have indicated the importance of mechanical stress on the development and malignancy of cancer. Various types of mechanical stress activate adaptive tumor cell responses that include alterations in the extracellular matrix (ECM) which have an impact on tumor malignancy. In this review, we describe and discuss the current knowledge of the effects of ECM alterations and mechanical stress on GBM aggressiveness. Gradual changes in the brain ECM have been connected to the biological and physical alterations of GBM cells. For example, increased expression of several ECM components such as glycosaminoglycans (GAGs), hyaluronic acid (HA), proteoglycans and fibrous proteins result in stiffening of the brain ECM, which alters inter-and intracellular signaling activity. Several mechanosensing signaling pathways have been identified that orchestrate adaptive responses, such as Hippo/YAP, CD44, and actin skeleton signaling, which remodel the cytoskeleton and affect cellular properties such as cell–cell/ECM interactions, growth, and migration/invasion of GBM cells. In vitro, hydrogels are used as a model to mimic the stiffening of the brain ECM and reconstruct its mechanics, which we also discuss. Overall, we provide an overview of the tumor microenvironmental landscape of GBM with a focus on ECM stiffening and its associated adaptive cellular signaling pathways and their possible therapeutic exploitation

E1A functions as a coactivator of retinoic acid-dependent retinoic acid receptor-beta 2 promoter activation

The retinoic acid (RA) receptor (RAR) beta 2 promoter is strongly activated by RA in embryonal carcinoma (EC) cells. We examined this activation in the P19 EC-derived END-2 cell line and in E1A-expressing counterparts and found strong RA-dependent RAR beta 2 promoter activation in the E1A-expressing cells, which was not observed in the parental cell line, indicating a possible role for E1A in RAR beta 2 activation. In transient transfection assays, E1A functioned as a coactivator of RA-dependent RAR beta 2 promoter activation and, moreover, was able to restore this activation in cells lacking RAR beta 2 activation. By deletion analysis, two regions in the RAR beta 2 promoter were identified that mediate the stimulatory effect of E1A: the RA response element and TATA box-containing region and a more up-stream region between -180 and -63, in which a cAMP response element-related motif was identified as a target element for E1A. In addition, determination of endogenous E1A-like activity by measuring E2A promoter activity in transient transfection assays in EC and differentiated cells revealed a correlation between RA-dependent RAR beta 2 promoter activation and the presence of this activity, suggesting an important role for the cellular equivalent of E1A in regulation of the RAR beta 2 promoter

A unique small cell lung carcinoma disease progression model shows progressive accumulation of cancer stem cell properties and CD44 as a potential diagnostic marker

OBJECTIVES: Cancer stem cells (CSCs) have been implicated in disease progression of aggressive cancers including small cell lung carcinoma (SCLC). Here, we have examined the possible contribution of CSCs to SCLC progression and aggressiveness. MATERIALS AND METHODS: GLC-14, GLC-16 and GLC-19 SCLC cell lines derived from one patient, representing increasing progressive stages of disease were used. CSC marker expressions was determined by RT-qPCR and western blotting analyses, and heterogeneity was studied by CSC marker expression by immunofluorescence microscopy and flow cytometry. Colony formation assays were used to assess stem cell properties and therapy sensitivity. RESULTS: Increasing expression of stem cell markers MYC, SOX2 and particularly CD44 were found in association with advancing disease. Single and overlapping expression of these markers indicated the presence of different CSC populations. The accumulation of more homogeneous double- and triple-positive CSC populations evolved with disease progression. Functional characterization of CSC properties affirmed higher proficiency of colony forming ability and increased resistance to γ-irradiation in GLC-16 and GLC-19 compared to GLC-14. GLC-19 colony formation was significantly inhibited by a human anti-CD44 antibody. CONCLUSION: The progressive increase of MYC, SOX2 and particularly CD44 expression that was accompanied with enhanced colony forming capacity and resistance in the in vitro GLC disease progression model, supports the potential clinical relevance of CSC populations in malignancy and disease relapse of SCLC

Novel insights into vascularization patterns and angiogenic factors in glioblastoma subclasses

Glioblastoma (GBM) is a highly vascularized and aggressive type of primary brain tumor in adults with dismal survival. Molecular subtypes of GBM have been identified that are related to clinical outcome and response to therapy. Although the mesenchymal type has been ascribed higher angiogenic activity, extensive characterization of the vascular component in GBM subtypes has not been performed. Therefore, we aimed to investigate the differential vascular status and angiogenic signaling levels in molecular subtypes. GBM tissue samples representing proneural IDH1 mutant, classical-like and mesenchymal-like subtypes were analyzed by morphometry for the number of vessels, vessel size and vessel maturity. Also the expression levels of factors from multiple angiogenic signaling pathways were determined. We found that necrotic and hypoxic areas were relatively larger in mesenchymal-like tumors and these tumors also had larger vessels. However, the number of vessels, basement membrane deposition and pericyte coverage did not vary between the subtypes. Regarding signaling patterns the majority of factors were expressed at similar levels in the subtypes, and only ANGPT2, MMP2, TIMP1, VEGFA and MMP9/TIMP2 were higher expressed in GBMs of the classical-like subtype. In conclusion, although morphological differences were observed between the subtypes, the angiogenic signaling status of GBM subtypes seemed to be rather similar. These results challenge the concept of mesenchymal GBMs being more angiogenic than other subclasses

The Unfolded Protein Response Sensor PERK Mediates Stiffness-Dependent Adaptation in Glioblastoma Cells

Glioblastoma multiforme (GBM) is the most aggressive brain tumor in adults. In addition to genetic causes, the tumor microenvironment (TME), including stiffening of the extracellular matrix (ECM), is a main driver of GBM progression. Mechano-transduction and the unfolded protein response (UPR) are essential for tumor-cell adaptation to harsh TME conditions. Here, we studied the effect of a variable stiff ECM on the morphology and malignant properties of GBM stem cells (GSCs) and, moreover, examined the possible involvement of the UPR sensor PERK herein. For this, stiffness-tunable human blood plasma (HBP)/alginate hydrogels were generated to mimic ECM stiffening. GSCs showed stiffness-dependent adaptation characterized by elongated morphology, increased proliferation, and motility which was accompanied by F-Actin cytoskeletal remodeling. Interestingly, in PERK-deficient GSCs, stiffness adaptation was severely impaired, which was evidenced by low F-Actin levels, the absence of F-Actin remodeling, and decreased cell proliferation and migration. This impairment could be linked with Filamin-A (FLN-A) expression, a known interactor of PERK, which was strongly reduced in PERK-deficient GSCs. In conclusion, we identified a novel PERK/FLNA/F-Actin mechano-adaptive mechanism and found a new function for PERK in the cellular adaptation to ECM stiffening

Evaluation of Ac-Lys(0)(IRDye800CW)Tyr(3)-octreotate as a novel tracer for SSTR2-targeted molecular fluorescence guided surgery in meningioma

PURPOSE: Meningioma recurrence rates can be reduced by optimizing surgical resection with the use of intraoperative molecular fluorescence guided surgery (MFGS). We evaluated the potential of the fluorescent tracer 800CW-TATE for MFGS using in vitro and in vivo models. It targets somatostatin receptor subtype 2 (SSTR(2)), which is overexpressed in all meningiomas. METHODS: Binding affinity of 800CW-TATE was evaluated using [(177)Lu] Lu-DOTA-Tyr(3)-octreotate displacement assays. Tumor uptake was determined by injecting 800CW-TATE in (SSTR(2)-positive) NCI-H69 or (SSTR(2)-negative) CH-157MN xenograft bearing mice and FMT2500 imaging. SSTR(2)-specific binding was measured by comparing tumor uptake in NCI-H69 and CH-157MN xenografts, blocking experiments and non-targeted IRDye800CW-carboxylate binding. Tracer distribution was analyzed ex vivo, and the tumor-to-background ratio (TBR) was calculated. SSTR(2) expression was determined by immunohistochemistry (IHC). Lastly, 800CW-TATE was incubated on frozen and fresh meningioma specimens and analyzed by microscopy. RESULTS: 800CW-TATE binding affinity assays showed an IC(50) value of 72 nM. NCI-H69 xenografted mice showed a TBR of 21.1. 800CW-TATE detection was reduced after co-administration of non-fluorescent DOTA-Tyr(3)-octreotate or administration of IRDye800CW. CH-157MN had no tumor specific tracer staining due to absence of SSTR(2) expression, thereby serving as a negative control. The tracer bound specifically to SSTR(2)-positive meningioma tissues representing all WHO grades. CONCLUSION: 800CW-TATE demonstrated sufficient binding affinity, specific SSTR(2)-mediated tumor uptake, a favorable biodistribution, and high TBR. These features make this tracer very promising for use in MFGS and could potentially aid in safer and a more complete meningioma resection, especially in high-grade meningiomas or those at complex anatomical localizations. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s11060-021-03739-1