Total serum N-glycans associate with response to immune checkpoint inhibition therapy and survival in patients with advanced melanoma

BACKGROUND

Immune checkpoint inhibitors (ICIs) have revolutionized the treatment of melanoma and other cancers. However, no reliable biomarker of survival or response has entered the clinic to identify those patients with melanoma who are most likely to benefit from ICIs. Glycosylation affects proteins and lipids' structure and functions. Tumours are characterized by aberrant glycosylation which may contribute to their progression and hinder an effective antitumour immune response.

METHODS

We aim at identifying novel glyco-markers of response and survival by leveraging the N-glycome of total serum proteins collected in 88 ICI-naive patients with advanced melanoma from two European countries. Samples were collected before and during ICI treatment.

RESULTS

We observe that responders to ICIs present with a pre-treatment N-glycome profile significantly shifted towards higher abundancy of low-branched structures containing lower abundances of antennary fucose, and that this profile is positively associated with survival and a better predictor of response than clinical variables alone.

CONCLUSION

While changes in serum protein glycosylation have been previously implicated in a pro-metastatic melanoma behaviour, we show here that they are also associated with response to ICI, opening new avenues for the stratification of patients and the design of adjunct therapies aiming at improving immune response.

Biophysical characterization of melanoma cell phenotype markers during metastatic progression

Melanoma is the most fatal form of skin cancer, with increasing prevalence worldwide. The most common melanoma genetic driver is mutation of the proto-oncogene serine/threonine kinase BRAF; thus, the inhibition of its MAP kinase pathway by specific inhibitors is a commonly applied therapy. However, many patients are resistant, or develop resistance to this type of monotherapy, and therefore combined therapies which target other signaling pathways through various molecular mechanisms are required. A possible strategy may involve targeting cellular energy metabolism, which has been recognized as crucial for cancer development and progression and which connects through glycolysis to cell surface glycan biosynthetic pathways. Protein glycosylation is a hallmark of more than 50% of the human proteome and it has been recognized that altered glycosylation occurs during the metastatic progression of melanoma cells which, in turn facilitates their migration. This review provides a description of recent advances in the search for factors able to remodel cell metabolism between glycolysis and oxidative phosphorylation, and of changes in specific markers and in the biophysical properties of cells during melanoma development from a nevus to metastasis. This development is accompanied by changes in the expression of surface glycans, with corresponding changes in ligand-receptor affinity, giving rise to structural features and viscoelastic parameters particularly well suited to study by label-free biophysical methods.

Contribution of sialic acids to integrin α5β1 functioning in melanoma cells

PURPOSE

To establish the relationship between sialylation of integrin α5β1 and possible alteration in the function of α5β1 receptor in melanoma cells.

MATERIALS AND METHODS

Integrin α5β1 was isolated from primary WM115 (RGP/VGP-like phenotype) and metastatic WM266-4 (lymph node metastasis) cells via affinity chromatography. Integrin α5β1 sialylation and the shift in relative masses of the enzymatically desialylated subunits were confirmed by confocal microscopy and SDS-PAGE, respectively. The ELISA assay was performed to evaluate sialic acid (SA) influence on integrin α5β1 binding to fibronectin (FN). Cell invasion was investigated by the Transwell invasion assay. The effect of neuraminidases treatment on melanoma cells was assessed by flow cytometry using Maackia amurensis and Sambucus nigra lectins.

RESULTS

Both subunits of integrin α5β1 were found to be more abundantly sialylated in primary than in metastatic cells. The removal of SA had no effect on the purified integrin α5β1 binding to FN. Although metastatic cells underwent more pronounced desialylation than primary cells, invasion of primary WM115 cells was more dependent on the presence of α2-3 linked SA than it was in the case of metastatic WM266-4 cells. In both melanoma cell lines not only integrin α5β1 was involved in invasion, however simultaneous desialylation and usage of anti-integrin α5β1 antibodies resulted in lower invasion abilities of primary WM115 cells.

CONCLUSIONS

Our data suggest that in primary melanoma cells integrin α5β1 action is more likely dependent on its glycosylation profile, i.e. the presence of SA residues, which influence (decreased) their invasion properties and may facilitate malignant melanoma progression.

The glycomic effect of N-acetylglucosaminyltransferase III overexpression in metastatic melanoma cells. GnT-III modifies highly branched N-glycans

N-acetylglucosaminyltransferase III (GnT-III) is known to catalyze N-glycan "bisection" and thereby modulate the formation of highly branched complex structures within the Golgi apparatus. While active, it inhibits the action of other GlcNAc transferases such as GnT-IV and GnT-V. Moreover, GnT-III is considered as an inhibitor of the metastatic potential of cancer cells both in vitro and in vivo. However, the effects of GnT-III may be more diverse and depend on the cellular context. We describe the detailed glycomic analysis of the effect of GnT-III overexpression in WM266-4-GnT-III metastatic melanoma cells. We used MALDI-TOF and ESI-ion-trap-MS/MS together with HILIC-HPLC of 2-AA labeled N-glycans to study the N-glycome of membrane-attached and secreted proteins. We found that the overexpression of GnT-III in melanoma leads to the modification of a broad range of N-glycan types by the introduction of the "bisecting" GlcNAc residue with highly branched complex structures among them. The presence of these unusual complex N-glycans resulted in stronger interactions of cellular glycoproteins with the PHA-L. Based on the data presented here we conclude that elevated activity of GnT-III in cancer cells does not necessarily lead to a total abrogation of the formation of highly branched glycans. In addition, the modification of pre-existing N-glycans by the introduction of "bisecting" GlcNAc can modulate their capacity to interact with carbohydrate-binding proteins such as plant lectins. Our results suggest further studies on the biological function of "bisected" oligosaccharides in cancer cell biology and their interactions with carbohydrate-binding proteins.

β1,6-branched complex-type N-glycans affect FAK signaling in metastatic melanoma cells

Integrin-dependent binding of the cell to extracellular matrix (ECM) is a key activator of the focal adhesion kinase (FAK) signaling pathway. N-glycosylation of integrins affects their interactions with ECM proteins. Using WM266-4 cells with overexpression of β1,6-acetylglucosaminyltransferase V, we showed that β1,6-branched N-glycans increased tyrosine phosphorylation of FAK in metastatic melanoma cells, resulting in enhanced migration on vitronectin (VN). The co-localization of αvβ3 integrin and FAK in focal adhesions of melanoma cells growing on VN indicates their interaction in signal transduction. Melanoma cell migration on VN was mediated by αvβ3 caring overexpressed β1,6-branched structures, important for FAK upregulation.

Visualization of melanoma tumor with lectin-conjugated rare-earth doped fluoride nanocrystals

AIM

To develop specific fluorescent markers for melanoma tumor visualization, which would provide high selectivity and reversible binding pattern, by the use of carbohydrate-recognizing proteins, lectins, combined with the physical ability for imaging deep in the living tissues by utilizing red and near infrared fluorescent properties of specific rare-earth doped nanocrystals (NC).

METHODS

B10F16 melanoma cells were inoculated to C57BL/6 mice for inducing experimental melanoma tumor. Tumors were removed and analyzed by lectin-histochemistry using LABA, PFA, PNA, HPA, SNA, GNA, and NPL lectins and stained with hematoxylin and eosin. NPL lectin was conjugated to fluorescent NaGdF4:Eu(3+)-COOH nanoparticles (5 nm) via zero length cross-linking reaction, and the conjugates were purified from unbound substances and then used for further visualization of histological samples. Fluorescent microscopy was used to visualize NPL-NaGdF4:Eu(3+) with the fluorescent emission at 600-720 nm range.

RESULTS

NPL lectin selectively recognized regions of undifferentiated melanoblasts surrounding neoangiogenic foci inside melanoma tumor, PNA lectin recognized differentiated melanoblasts, and LCA and WGA were bound to tumor stroma regions. NPL-NaGdF4:Eu(3+) conjugated NC were efficiently detecting newly formed regions of melanoma tumor, confirmed by fluorescent microscopy in visible and near infrared mode. These conjugates possessed high photostability and were compatible with convenient xylene-based mounting systems and preserved intensive fluorescent signal at samples storage for at least 6 months.

CONCLUSION

NPL lectin-NaGdF4:Eu(3+) conjugated NC permitted distinct identification of contours of the melanoma tissue on histological sections using red excitation at 590-610 nm and near infrared emission of 700-720 nm. These data are of potential practical significance for development of glycans-conjugated nanoparticles to be used for in vivo visualization of melanoma tumor.

Studies on primary uveal and cutaneous melanoma cell interaction with vitronectin

We have examined the diversity between primary uveal (92-1 and Mel202) and cutaneous (FM55P and IGR-39) melanoma cells in their interaction with vitronectin, and established the effect of integrins and β1,6-branched N-oligosaccharides on this process. The adhesion level of uveal melanoma cells to vitronectin was at least twice lower than that of cutaneous ones, but all cells tested repaired scratch wounds on vitronectin-coated surfaces with similar speed. Swainsonine treatment, by reducing the amount of β1,6-branches, significantly decreased cell attachment in all cases, but reduction of wound healing efficiency was compromised only in cutaneous melanoma cell. Functional blocking antibodies used in adhesion and migration assays revealed that integrin αvβ3 was strongly involved in adhesion and migration only in cutaneous melanoma cells, but its role here was less pronounced than that of integrin αvβ5. However, in uveal melanoma the specific anti-αvβ5 integrin antibody had no impact on migration speed. Therefore, the anti-α3β1 integrin antibody was used in order to explain the nature of uveal melanoma interaction with vitronectin, which caused a mild decrease in adhesion efficiency and reduced their motility. Expression of αvβ5 integrin differed between the cell lines, but there was no distinct pattern to distinguish uveal melanoma from cutaneous melanoma. In conclusion, αvβ5, but not αvβ3 integrin is heavily involved in uveal melanoma cell interaction with vitronectin. The role of β1,6-branched N-glycans in the adhesion, but not during migration, of all cells to vitronectin has been confirmed.

Expression of integrins α3β1 and α5β1 and GlcNAc β1,6 glycan branching influences metastatic melanoma cell migration on fibronectin

Acquisition of metastatic potential is accompanied by changes in cell surface N-glycosylation. One of the best-studied changes is increased expression of N-acetylglucosaminyltransferase V enzyme (GnT-V) and its products, β1,6-branched N-linked oligosaccharides, observed in the tumorigenesis of many cancers. In this study we demonstrate that during the transition from the vertical growth phase (VGP) (WM793 cell line) to the metastatic stage (WM1205Lu line), β1,6 glycosylation of melanoma cell surface proteins increases as a consequence of elevated expression of the GnT-V-encoding Mgat-5 gene. Treatment with swainsonine led to reduced cell motility on fibronectin in both cell lines; the effect was stronger in metastatic cells, probably due to the higher content of GlcNAc β1,6-branched glycans on the main fibronectin receptors - integrins α5β1 and α3β1. Our results show that GlcNAc β1,6 N-glycosylation of cell surface receptors, which increases with the aggressiveness of melanoma cells, is an important factor influencing melanoma cell migration.

Thigmotropism of malignant melanoma cells

During malignant melanoma (MM) progression including incipient metastasis, neoplastic cells follow some specific migration paths inside the skin. In particular, they progress along the dermoepidermal basement membrane, the hair follicles, the sweat gland apparatus, nerves, and the near perivascular space. These features evoke the thigmotropism phenomenon defined as a contact-sensing growth of cells. This process is likely connected to modulation in cell tensegrity (control of the cell shape). These specifically located paucicellular aggregates of MM cells do not appear to be involved in the tumorigenic growth phase, but rather they participate in the so-called "accretive" growth model. These MM cell collections are often part of the primary neoplasm, but they may, however, correspond to MM micrometastases and predict further local overt metastasis spread.