Ricinus communis agglutinin I leads to rapid down-regulation of VEGFR-2 and endothelial cell apoptosis in tumor blood vessels

Structure-Function Relationships of the CMP-Sialic Acid Transporter through Analysis of a Pathogenic Variant in an Alternatively Spliced Functional Isoform

The human CMP-sialic acid transporter (hCST) is a mammalian highly conserved type III antiporter that translocates CMP-sialic acid into the Golgi lumen, supporting sialylation. Although different works have focused on elucidating structure-function relationships in the hCST, this is the first study to address them in an alternatively spliced isoform. We have previously reported the expression of a functional human del177 isoform that has skipping of exon 6, resulting in a loss of 59 amino acids, without change in the open reading frame and conserving its C-terminal region. To elucidate structure-function relationships, we interrogated this isoform with a known pathogenic variant c.303C>T (p.Q101H) for the wt isoform, showing that its pathogenicity is significatively reduced in the mutated del177 isoform (del177Q101H). This is further explained by using a homology model based on previously reported mouse and maize crystal structures.

Form follows function: The endothelial glycocalyx

Three types of capillaries, namely continuous, fenestrated, and sinusoidal, form the microvascular system; each type has a specialized structure and function to respond to the demands of the organs they supply. The endothelial glycocalyx, a gel-like layer of glycoproteins that covers the luminal surface of the capillary endothelium, is also thought to maintain organ and vascular homeostasis by exhibiting different morphologies based on the functions of the organs and capillaries in which it is found. Recent advances in analytical technology have enabled more detailed observations of the endothelial glycocalyx, revealing that it indeed differs in structure across various organs. Furthermore, differences in the lectin staining patterns suggest the presence of different endothelial glycocalyx components across various organs. Interestingly, injury to the endothelial glycocalyx due to various pathologic and physiological stimuli causes the release of these components into the blood. Thus, circulating glycocalyx components may be useful biomarkers of organ dysfunction and disease severity. Moreover, a recent study suggested that chronic injury to the glycocalyx reduces the production of these glycocalyx components and changes their structure, leading it to become more vulnerable to external stimuli. In this review, we have summarized the various endothelial glycocalyx structures and their functions.

3'-Sulfo-TF Antigen Determined by GAL3ST2/ST3GAL1 Is Essential for Antitumor Activity of Fungal Galectin AAL/AAGL

Many lectins have been reported to have antitumor activities; identifying the glycan ligands in tumor cells of lectins is crucial for lectin clinical application. An edible mushroom galectin, Agrocybe aegerita lectin (AAL/AAGL), that has a high antitumor activity has been reported. In this paper, based on the glycan array data, it is showed that the Thomsen-Friedenreich antigen (TF antigen)-related O-glycans were found to be highly correlated with the antitumor activity of AAL/AAGL. Further glycosyltransferase quantification suggested that the ratio between GAL3ST2 and ST3GAL1 (GAL3ST2/ST3GAL1), which determined the 3'-sulfo-TF expression level, was highly correlated with the antitumor activity of AAL/AAGL. Overexpressing the enzyme of GAL3ST2 in HL60 and HeLa cell lines could increase the growth inhibition ratio of AAL/AAGL from 22.7 to 43.9% and 27.8 to 39.1%, respectively. However, ST3GAL1 in Jurkat cells could decrease the growth inhibition ratio from 44.7 to 35.6%. All the data suggested that the 3'-sulfo-TF antigen is one of the main glycan ligands that AAL/AAGL recognizes in tumor cells. AAL/AAGL may potentially serve as a reagent for cancer diagnosis and a targeted therapy for the 3'-sulfo-TF antigen.

Synthetic linear glycopolymers and their biological applications

As typical affinities of carbohydrates with their receptors are modest, polymers of carbohydrates (glycopolymers) are exciting tools to probe the multifaceted biological activities of glycans. In this review, the linear glycopolymers and the multivalency effects are first introduced. This is followed by discussions of methods to synthesize these polymers. Subsequently, the interactions of glycopolymers with plant lectins and viral/bacterial carbohydrate binding proteins are discussed. In addition, applications of the glycopolymers in facilitating glycan microarray studies, mimicking cell surface glycans, modulation of the immune system, cryoprotection of protein, and electron-beam lithography are presented to stimulate further development of this fascinating technology.

Plant lectins in cancer therapeutics: Targeting apoptosis and autophagy-dependent cell death

Plant lectins are non-immunoglobin in nature and bind to the carbohydrate moiety of the glycoconjugates without altering any of the recognized glycosyl ligands. Plant lectins have found applications as cancer biomarkers for recognizing the malignant tumor cells for the diagnosis and prognosis of cancer. Interestingly, plant lectins contribute to inducing cell death through autophagy and apoptosis, indicating their potential implication in cancer inhibitory mechanism. In the present review, anticancer activities of major plant lectins have been documented, with a detailed focus on the signaling circuit for the possible molecular targeted cancer therapy. In this context, several lectins have exhibited preclinical and clinical significance, driving toward therapeutic potential in cancer treatment. Moreover, several plant lectins induce immunomodulatory activities, and therefore, novel strategies have been established from preclinical and clinical investigations for the development of combinatorial treatment consisting of immunotherapy along with other anticancer therapies. Although the application of plant lectins in cancer is still in very preliminary stage, advanced high-throughput technology could pave the way for the development of lectin-based complimentary medicine for cancer treatment.

Evaluation of Different N-Glycopeptide Enrichment Methods for N-Glycosylation Sites Mapping in Mouse Brain

N-Glycosylation of proteins plays a critical role in many biological pathways. Because highly heterogeneous N-glycopeptides are present in biological sources, the enrichment procedure is a crucial step for mass spectrometry analysis. Five enrichment methods, including IP-ZIC-HILIC, hydrazide chemistry, lectin affinity, ZIC-HILIC-FA, and TiO2 affinity were evaluated and compared in the study of mapping N-glycosylation sites in mouse brain. On the basis of our results, the identified N-glycosylation sites were 1891, 1241, 891, 869, and 710 and the FDR values were 3.29, 5.62, 9.54, 9.54, and 20.02%, respectively. Therefore, IP-ZIC-HILIC enrichment method displayed the highest sensitivity and specificity. In this work, we identified a total of 3446 unique glycosylation sites conforming to the N-glycosylation consensus motif (N-X-T/S/C; X ≠ P) with (18)O labeling in 1597 N-glycoproteins. N-glycosylation site information was used to confirm or correct the transmembrane topology of the 57 novel transmembrane N-glycoproteins.

COG Complex Complexities: Detailed Characterization of a Complete Set of HEK293T Cells Lacking Individual COG Subunits

The Conserved Oligomeric Golgi complex is an evolutionarily conserved multisubunit tethering complex (MTC) that is crucial for intracellular membrane trafficking and Golgi homeostasis. The COG complex interacts with core vesicle docking and fusion machinery at the Golgi; however, its exact mechanism of action is still an enigma. Previous studies of COG complex were limited to the use of CDGII (Congenital disorders of glycosylation type II)-COG patient fibroblasts, siRNA mediated knockdowns, or protein relocalization approaches. In this study we have used the CRISPR approach to generate HEK293T knock-out (KO) cell lines missing individual COG subunits. These cell lines were characterized for glycosylation and trafficking defects, cell proliferation rates, stability of COG subunits, localization of Golgi markers, changes in Golgi structure, and N-glycan profiling. We found that all KO cell lines were uniformly deficient in cis/medial-Golgi glycosylation and each had nearly abolished binding of Cholera toxin. In addition, all cell lines showed defects in Golgi morphology, retrograde trafficking and sorting, sialylation and fucosylation, but severities varied according to the affected subunit. Lobe A and Cog6 subunit KOs displayed a more severely distorted Golgi structure, while Cog2, 3, 4, 5, and 7 knock outs had the most hypo glycosylated form of Lamp2. These results led us to conclude that every subunit is essential for COG complex function in Golgi trafficking, though to varying extents. We believe that this study and further analyses of these cells will help further elucidate the roles of individual COG subunits and bring a greater understanding to the class of MTCs as a whole.

Anti-tumor innate immunity activated by intermittent metronomic cyclophosphamide treatment of 9L brain tumor xenografts is preserved by anti-angiogenic drugs that spare VEGF receptor 2

Background

Metronomic cyclophosphamide given on an intermittent, 6-day repeating schedule, but not on an exposure dose-equivalent daily schedule, activates an anti-tumor innate immune response that leads to major regression of large implanted gliomas, without anti-angiogenesis.

Methods and approach

Mice bearing implanted 9L gliomas were used to investigate the effects of this 6-day repeating, immunogenic cyclophosphamide schedule on myeloid-derived suppressor cells, which are pro-angiogenic and can inhibit anti-tumor immunity, and to elucidate the mechanism whereby the innate immune cell-dependent tumor regression response to metronomic cyclophosphamide treatment is blocked by several anti-angiogenic receptor tyrosine kinase inhibitors.

Results

Intermittent metronomic cyclophosphamide scheduling strongly increased glioma-associated CD11b⁺ immune cells but not CD11b⁺Gr1⁺ myeloid-derived suppressor cells, while bone marrow and spleen reservoirs of the suppressor cells were decreased. The inhibition of immune cell recruitment and tumor regression by anti-angiogenic receptor tyrosine kinase inhibitors, previously observed in several brain tumor models, was recapitulated in the 9L tumor model with the VEGFR2-specific inhibitory monoclonal antibody DC101 (p < 0.01), implicating VEGFR2 signaling as an essential step in metronomic cyclophosphamide-stimulated immune cell recruitment. In contrast, sorafenib, a multi-receptor tyrosine kinase inhibitor with comparatively weak VEGF receptor phosphorylation inhibitory activity, was strongly anti-angiogenic but did not block metronomic cyclophosphamide-induced innate immunity or tumor regression (p > 0.05).

Conclusions

The interference by receptor tyrosine kinase inhibitors in the immunogenic actions of intermittent metronomic chemotherapy is not a consequence of anti-angiogenesis per se, as demonstrated in an implanted 9L tumor model. Furthermore, this undesirable interaction with tyrosine kinase inhibitors can be avoided by using anti-angiogenic drugs that spare the VEGFR2 pathway.

Role of uterine contraction in regeneration of the murine postpartum endometrium

The endometrium undergoes continuous repair and regeneration without scarring throughout the reproductive life of women. However, the mechanisms responsible for this complete restoration remain mostly unexplored. We hypothesized that the ischemic state and local hypoxia present after parturition may create a special microenvironment for endometrial healing, and that this ischemia might be caused by reduction in organ volume via postpartum uterine contraction. Here, we developed a mouse model using a combination of cesarean section and the administration of a beta 2 adrenergic receptor agonist (ritodrine hydrochloride) in postpartum mice that had been ovariectomized to exclude the effect of ovarian hormones. Our results revealed that transient hypoxia indeed occurred in postpartum uteri. Furthermore, we found that the number of M2 macrophages, which play a central role in wound healing, peaked on Postpartum Day 3 and gradually decreased thereafter in hypoxic injury sites. Almost concurrently, significant upregulation of vascular endothelial growth factor and transforming growth factor beta (TGFbeta) was observed. In particular, the antifibrotic factor TGFbeta3 was released during the endometrial healing process. These changes were significantly suppressed by inhibition of uterine contraction. Taken together, these results suggest that uterine contraction is essential, not only for hemostasis, but also for endometrial regeneration, leading to a process that involves the activation of macrophages, increased endometrial cell proliferation, and upregulation of nonfibrotic growth factors. This study paves the way to a novel approach for investigating the process of scarless wound healing.

Blebbishields, the emergency program for cancer stem cells: sphere formation and tumorigenesis after apoptosis

Caspases mediate apoptosis and have also been implicated in stem-cell biology. How caspases are linked to stem-cell biology is not known. Here, we show that the apoptotic blebs of cancer cells fuse together to form novel structures called 'blebbishields'. Blebbishields form spheres by fusion. Both blebbishield formation and sphere formation involve active caspases and N-linked glycosylation. Sphere formation is enhanced by acidic pH and is counteracted by inhibitors of proton pump, caspases, and cholesterol. The blebbishields from VEGFR2(High) cells are capable of enhanced sphere formation. Blebbishields express transiently downregulated stem-cell markers and the sphere-forming blebbishield-derived cells are tumorigenic. Our study demonstrates that the cancer stem cells can survive after apoptosis by blebbishield formation and subsequent sphere formation.

Collagen VI ablation retards brain tumor progression due to deficits in assembly of the vascular basal lamina

To investigate the importance of the vascular basal lamina in tumor blood vessel morphogenesis and function, we compared vessel development, vessel function, and progression of B16F10 melanoma tumors in the brains of wild-type and collagen VI-null mice. In 7-day tumors in the absence of collagen VI, the width of the vascular basal lamina was reduced twofold. Although the ablation of collagen VI did not alter the abundance of blood vessels, a detailed analysis of the number of either pericytes or endothelial cells (or pericyte coverage of endothelial cells) showed that collagen VI-dependent defects during the assembly of the basal lamina have negative effects on both pericyte maturation and the sprouting and survival of endothelial cells. As a result of these deficits, vessel patency was reduced by 25%, and vessel leakiness was increased threefold, resulting in a 10-fold increase in tumor hypoxia along with a fourfold increase in hypoxia-inducible factor-1α expression. In 12-day collagen VI-null tumors, vascular endothelial growth factor expression was increased throughout the tumor stroma, in contrast to the predominantly vascular pattern of vascular endothelial growth factor expression in wild-type tumors. Vessel size was correspondingly reduced in 12-day collagen VI-null tumors. Overall, these vascular deficits produced a twofold decrease in tumor volume in collagen VI-null mice, confirming that collagen VI-dependent basal lamina assembly is a critical aspect of vessel development.

In situ force mapping of mammary gland transformation

Tumor progression is characterized by an incremental stiffening of the tissue. The importance of tissue rigidity to cancer is appreciated, yet the contribution of specific tissue elements to tumor stiffening and their physiological significance remains unclear. We performed high-resolution atomic force microscopy indentation in live and snap-frozen fluorescently labeled mammary tissues to explore the origin of the tissue stiffening associated with mammary tumor development in PyMT mice. The tumor epithelium, the tumor-associated vasculature and the extracellular matrix all contributed to mammary gland stiffening as it transitioned from normal to invasive carcinoma. Consistent with the concept that extracellular matrix stiffness modifies cell tension, we found that isolated transformed mammary epithelial cells were intrinsically stiffer than their normal counterparts but that the malignant epithelium in situ was far stiffer than isolated breast tumor cells. Moreover, using an in situ vitrification approach, we determined that the extracellular matrix adjacent to the epithelium progressively stiffened as tissue evolved from normal through benign to an invasive state. Importantly, we also noted that there was significant mechanical heterogeneity within the transformed tissue both in the epithelium and the tumor-associated neovasculature. The vascular bed within the tumor core was substantially stiffer than the large patent vessels at the invasive front that are surrounded by the stiffest extracellular matrix. These findings clarify the contribution of individual mammary gland tissue elements to the altered biomechanical landscape of cancerous tissues and emphasize the importance of studying cancer cell evolution under conditions that preserve native interactions.

Reduced VEGF production, angiogenesis, and vascular regrowth contribute to the antitumor properties of dual mTORC1/mTORC2 inhibitors

The mammalian target of rapamycin (mTOR) pathway is implicated widely in cancer pathophysiology. Dual inhibition of the mTOR kinase complexes mTORC1 and mTORC2 decreases tumor xenograft growth in vivo and VEGF secretion in vitro, but the relationship between these two effects are unclear. In this study, we examined the effects of mTORC1/2 dual inhibition on VEGF production, tumor angiogenesis, vascular regression, and vascular regrowth, and we compared the effects of dual inhibition to mTORC1 inhibition alone. ATP-competitive inhibitors OSI-027 and OXA-01 targeted both mTORC1 and mTORC2 signaling in vitro and in vivo, unlike rapamycin that only inhibited mTORC1 signaling. OXA-01 reduced VEGF production in tumors in a manner associated with decreased vessel sprouting but little vascular regression. In contrast, rapamycin exerted less effect on tumoral production of VEGF. Treatment with the selective VEGFR inhibitor OSI-930 reduced vessel sprouting and caused substantial vascular regression in tumors. However, following discontinuation of OSI-930 administration tumor regrowth could be slowed by OXA-01 treatment. Combining dual inhibitors of mTORC1 and mTORC2 with a VEGFR2 inhibitor decreased tumor growth more than either inhibitor alone. Together, these results indicate that dual inhibition of mTORC1/2 exerts antiangiogenic and antitumoral effects that are even more efficacious when combined with a VEGFR antagonist.