What controls the expression of the core-1 (Thomsen-Friedenreich) glycotope on tumor cells?

Extracellular vesicles and cancer stem cells: a deadly duo in tumor progression

The global incidence of cancer is increasing, with estimates suggesting that there will be 26 million new cases and 17 million deaths per year by 2030. Cancer stem cells (CSCs) and extracellular vesicles (EVs) are key to the resistance and advancement of cancer. They play a crucial role in tumor dynamics and resistance to therapy. CSCs, initially discovered in acute myeloid leukemia, are well-known for their involvement in tumor initiation, progression, and relapse, mostly because of their distinct characteristics, such as resistance to drugs and the ability to self-renew. EVs, which include exosomes, microvesicles, and apoptotic bodies, play a vital role in facilitating communication between cells within the tumor microenvironment (TME). They have a significant impact on cellular behaviors and contribute to genetic and epigenetic changes. This paper analyzes the mutually beneficial association between CSCs and EVs, emphasizing their role in promoting tumor spread and developing resistance mechanisms. This review aims to investigate the interaction between these entities in order to discover new approaches for attacking the complex machinery of cancer cells. It highlights the significance of CSCs and EVs as crucial targets in the advancement of novel cancer treatments, which helps stimulate additional research, promote progress in ideas for cancer treatment, and provide renewed optimism in the effort to reduce the burden of cancer.

CAR T cells redirected against tumor-specific antigen glycoforms: can low-sugar antigens guarantee a sweet success?

Immune-based therapies have experienced a pronounced breakthrough in the past decades as they acquired multiple US Food and Drug Administration (FDA) approvals for various indications. To date, six chimeric antigen receptor T cell (CAR-T) therapies have been permitted for the treatment of certain patients with relapsed/refractory hematologic malignancies. However, several clinical trials of solid tumor CAR-T therapies were prematurely terminated, or they reported life-threatening treatment-related damages to healthy tissues. The simultaneous expression of target antigens by healthy organs and tumor cells is partly responsible for such toxicities. Alongside targeting tumor-specific antigens, targeting the aberrantly glycosylated glycoforms of tumor-associated antigens can also minimize the off-tumor effects of CAR-T therapies. Tn, T, and sialyl-Tn antigens have been reported to be involved in tumor progression and metastasis, and their expression results from the dysregulation of a series of glycosyltransferases and the endoplasmic reticulum protein chaperone, Cosmc. Moreover, these glycoforms have been associated with various types of cancers, including prostate, breast, colon, gastric, and lung cancers. Here, we discuss how underglycosylated antigens emerge and then detail the latest advances in the development of CAR-T-based immunotherapies that target some of such antigens.

Targeting Tumor Glycans for Cancer Therapy: Successes, Limitations, and Perspectives

Simple Summary

Aberrant glycosylation is a common feature of many cancers, and it plays crucial roles in tumor development and biology. Cancer progression can be regulated by several physiopathological processes controlled by glycosylation, such as cell–cell adhesion, cell–matrix interaction, epithelial-to-mesenchymal transition, tumor proliferation, invasion, and metastasis. Different mechanisms of aberrant glycosylation lead to the formation of tumor-associated carbohydrate antigens (TACAs), which are suitable for selective cancer targeting, as well as novel antitumor immunotherapy approaches. This review summarizes the strategies developed in cancer immunotherapy targeting TACAs, analyzing molecular and cellular mechanisms and state-of-the-art methods in clinical oncology.

Abstract

Aberrant glycosylation is a hallmark of cancer and can lead to changes that influence tumor behavior. Glycans can serve as a source of novel clinical biomarker developments, providing a set of specific targets for therapeutic intervention. Different mechanisms of aberrant glycosylation lead to the formation of tumor-associated carbohydrate antigens (TACAs) suitable for selective cancer-targeting therapy. The best characterized TACAs are truncated O-glycans (Tn, TF, and sialyl-Tn antigens), gangliosides (GD2, GD3, GM2, GM3, fucosyl-GM1), globo-serie glycans (Globo-H, SSEA-3, SSEA-4), Lewis antigens, and polysialic acid. In this review, we analyze strategies for cancer immunotherapy targeting TACAs, including different antibody developments, the production of vaccines, and the generation of CAR-T cells. Some approaches have been approved for clinical use, such as anti-GD2 antibodies. Moreover, in terms of the antitumor mechanisms against different TACAs, we show results of selected clinical trials, considering the horizons that have opened up as a result of recent developments in technologies used for cancer control.

Update on the role of C1GALT1 in cancer (Review)

Cancer remains one of the most difficult diseases to treat. In the quest for early diagnoses to improve patient survival and prognosis, targeted therapies have become a hot research topic in recent years. Glycosylation is the most common posttranslational modification in mammalian cells. Core 1β1,3-galactosyltransferase (C1GALT1) is a key glycosyltransferase in the glycosylation process and is the key enzyme in the formation of the core 1 structure on which most complex and branched O-glycans are formed. A recent study reported that C1GALT1 was aberrantly expressed in tumors. In cancer cells, C1GALT1 is regulated by different factors. In the present review, the expression of C1GALT1 in different tumors and its possible molecular mechanisms of action are described and the role of C1GALT1 in cancer development is discussed.

Expression of Thomsen-Friedenreich Antigen in Colorectal Cancer and Association with Microsatellite Instability

Microsatellite instability (MSI) is a molecular phenotype due to a deficient DNA mismatch repair (dMMR). In colorectal cancer (CRC), dMMR/MSI is associated with several clinical and histopathological features, influences prognosis, and is a predictive factor of response to therapy. In daily practice, dMMR/MSI profiles are identified by immunohistochemistry and/or multiplex PCR. The Thomsen-Friedenreich (TF) antigen was previously found to be a potential single marker to identify MSI-high gastric cancers. Therefore, in this study, we aimed to disclose a possible association between TF expression and MSI status in CRC. Furthermore, we evaluated the relationship between TF expression and other clinicopathological features, including patient survival. We evaluated the expression of the TF antigen in a cohort of 25 MSI-high and 71 microsatellite stable (MSS) CRCs. No association was observed between the expression of the TF antigen and MSI-high status in CRC. The survival analysis revealed that patients with MSI-high CRC showed improved survival when the TF antigen was expressed. This finding holds promise as it indicates the potential use of the TF antigen as a biomarker of better prognosis in MSI-high CRCs that should be validated in an independent and larger CRC cohort.

TF-containing MUC1 glycopeptides fail to entice Galectin-1 recognition of tumor-associated Thomsen-Freidenreich (TF) antigen (CD176) in solution

Aberrant Mucin-1 (MUC1) glycosylation with the Thomsen-Friedenreich (TF) tumor-associated antigen (CD176) is a hallmark of epithelial carcinoma progression and poor patient prognosis. Recognition of TF by glycan-binding proteins, such as galectins, enables the pathological repercussions of this glycan presentation, yet the underlying binding specificities of different members of the galectin family is a matter of continual investigation. While Galectin-3 (Gal-3) recognition of TF has been well-documented at both the cellular and molecular level, Galectin-1 (Gal-1) recognition of TF has only truly been alluded to in cell-based platforms. Immunohistochemical analyses have purported Gal-1 binding to TF on MUC1 at the cell surface, however binding at the molecular level was inconclusive. We hypothesize that glycan scaffold (MUC1's tandem repeat peptide sequence) and/or multivalency play a role in the binding recognition of TF antigen by Gal-1. In this study we have developed a method for large-scale expression of Gal-1 and its histidine-tagged analog for use in binding studies by isothermal titration calorimetry (ITC) and development of an analytical method based on AlphaScreen technology to screen for Gal-1 inhibitors. Surprisingly, neither glycan scaffold or multivalent presentation of TF antigen on the scaffold was able to entice Gal-1 recognition to the level of affinity expected for functional significance. Future evaluations of the Gal-1/TF binding interaction in order to draw connections between immunohistochemical data and analytical measurements are warranted.

The Potential Action of Thomsen-Friedenreich Monoclonal Antibody (A78-G/A7) in Thyroid Cancer

Background

Thomsen–Friedenreich antibody (TF-Ab) is a specific antibody against the Thomsen–Friedenreich antigen (TF-Ag). At present, studies on a number of other tumors have shown that TF-Ab can effectively inhibit metastasis and induce apoptosis in tumor cells. However, the role of TF-Ab in thyroid cancer (TC) remains unclear.

Materials and Methods

Normal subjects and patients with primary papillary TC with or without lymph node metastasis were tested for TF-Ab expression by enzyme-linked immunosorbent assays (ELISAs). Immunofluorescence was used to assess the expression of TF-Ag in thyroid papillary carcinoma with or without lymph node metastasis and undifferentiated cancer tissues. To evaluate the role of TF-Ab in TC, the effects of TF monoclonal antibody (mAb A78-G/A7) on cell biological function were investigated by MTT assays, flow cytometry, adhesion assays and transwell experiments.

Results

Compared with normal individuals, TF-Ab levels in patients with TC were decreased, but no changes were observed with respect to lymph node metastasis. The expression of TF-Ag in TC tissues was relatively higher than that detected in adjacent tissues, but it was not affected by the presence or absence of lymph node metastasis. Upon treatment mAb A78-G/A7 treating, TC cell cycles were affected, meanwhile the abilities to adhere, invade and migrate were also significantly reduced.

Conclusion

The results of the present study showed that mAb A78-G/A7 could affect the invasion and migration of all assayed TC cell lines. The effects of mAb A78-G/A7 on the cell cycle, adhesion, invasion and migration of TC cells were more significant than those observed for proliferation and apoptosis.

Profiling of Naturally Occurring Antibodies to the Thomsen-Friedenreich Antigen in Health and Cancer: The Diversity and Clinical Potential

The Thomsen-Friedenreich (TF) antigen is expressed in a majority of human tumors due to aberrant glycosylation in cancer cells. There is strong evidence that humoral immune response to TF represents an effective mechanism for the elimination of cancer cells that express TF-positive glycoconjugates. The presence of naturally occurring antibodies to tumor-associated TF and cancer-specific changes in their levels, isotype distribution and interrelation, avidity, and glycosylation profile make these Abs a convenient and ubiquitous marker for cancer diagnostics and prognostics. In this review, we attempt to summarize the latest data on the potential of TF-specific Abs for cancer diagnostics and prognostics.

Evaluation of the anti-Thomsen-Friedenreich antibodies Nemod-TF1 and Nemod-TF2 as prognostic markers in breast cancer

PURPOSE

The TF (Thomsen-Friedenreich, CD176, Galβ1-3GalNAc) carbohydrate moiety is known as a specific oncofetal carbohydrate epitope present in fetal and neoplastic tissue as well as in stem cells. TF was demonstrated to mediate tumor-promoting features and to be highly immunogenic. The current study aimed to evaluate whether presence of the TF antigen is associated with clinico-pathological parameters and prognosis of early breast cancer (BC).

METHODS

Primary BC tissue (n = 226) was stained for TF using two monoclonal anti-TF antibodies (Nemod-TF1, Nemod-TF2). Staining results were correlated to clinical data including survival.

RESULTS

Nemod-TF1 staining was positively correlated to lymph node metastasis (p = 0.03) and the presence of tumor-associated MUC1 (TA-MUC1; p = 0.003). Further, the presence of the Nemod-TF1 epitope predicted worse prognosis in TA-MUC1 positive (overall survival: p = 0.026) as well as in triple negative (overall survival: p = 0.002; distant metastasis-free survival: p = 0.012) BC.

CONCLUSIONS

The data presented here further support a role of TF in BC tumor biology. Whether anti-TF directed treatment approaches may gain clinical relevance in those cases determined as triple negative or TA-MUC1 positive remains to be determined.

Cluster binding studies with two anti-Thomsen-Friedenreich (anti-core-1, CD176, TF) antibodies: Evidence for a multiple TF epitope

Antibodies to carbohydrate epitopes are often of the IgM isotype and require multiple binding for sufficient avidity. Therefore clusters of epitopes are preferred antigenic sites in these cases. We have examined the type of clusters recognized by two anti-Thomsen-Friedenreich (TF, core-1, CD176) IgM antibodies, NM-TF1 and NM-TF2, using several different sets of TF-carrying synthetic glycoconjugates in ELISA experiments. To our surprise, the single most important factor determining binding strength was a close vicinity of several TF glycans at distances of ≤1 nm. Considering the known dimensions of IgM antibodies, our data strongly suggest that a cluster of up to four TF moieties, presenting as a "multiple epitope", is required to attach to a single combining site in order to result in adequate binding strength. This effect can also be achieved by "surrogate-multiple epitopes" consisting of separate TF-carrying molecules in close vicinity. In addition, it was found that serine-linked TFs are stronger bound than threonine-linked TFs by both antibodies. This peculiar type of cluster recognition may contribute to improved avidity and explicit tumor specificity.

The Thomsen-Friedenreich Antigen-Specific Antibody Signatures in Patients with Breast Cancer

Alterations in the glycosylation of serum total immunoglobulins show these antibodies to have a diagnostic potential for cancer but the disease-related Abs to the tumor-associated antigens, including glycans, have still poorly been investigated in this respect. We analysed serum samples from patients with breast carcinoma (n = 196) and controls (n = 64) for the level of Thomsen-Friedenreich (TF) antigen-specific antibody isotypes, their sialylation, interrelationships, and the avidity by using ELISA with the synthetic TF-polyacrylamide conjugate as an antigen and the sialic acid-specific Sambucus nigra agglutinin (SNA) and ammonium thiocyanate as a chaotrope. An increased sialylation of IgG and IgM, but a lower SNA reactivity of IgA TF antibodies, and a higher level and avidity of the TF-specific IgA were found in cancer patients. Other cancer-related signatures were the highly significant increase of the IgG/IgA ratio and the very low SNA/IgA index in cancer, including patients with an early stage of the disease. These changes showed a good diagnostic potential with about 80% accuracy. Thus, the level of naturally occurring anti-TF antigen antibodies, their sialylation profile, isotype distribution, and avidity displayed cancer-specific changes that could serve as novel noninvasive Ab-based biomarkers for early breast cancer.

The Synthesis and Biological Characterization of Acetal-Free Mimics of the Tumor-Associated Carbohydrate Antigens

Carcinomas express unique carbohydrates, known as tumor-associated carbohydrate antigens (TACAs), on their surface. These are potential targets for anticancer vaccines; however, to date, no such vaccine has reached the clinic. One factor that may complicate the success of this effort is the lability of the glycosidic bond. Acetal-free carbohydrates are analogues that lack the glycosidic linkage by replacing either the endo or exo oxygen with a methylene. This chapter summarizes the seminal syntheses of the mucin TACAs, provides an overview of common techniques for the synthesis of carbasugars and C-glycosides, reviews the syntheses published to date of acetal-free TACA analogues, and provides an overview of their observed biological activity. We conclude by offering a summation of the challenges remaining to the field biologically and the potential that acetal-free TACAs have of answering several basic questions in carbohydrate immunology.

Tumor-associated antigens: Tn antigen, sTn antigen, and T antigen

Glycosylation is one of the major posttranslational modifications of proteins. N-glycosylation (Asn-linked) and O-glycosylation (Ser/Thr-linked) are the two main forms. Abnormal O-glycosylation is frequently observed on the surface of tumor cells, and is associated with an adverse outcome and poor prognosis in patients with cancer. O-glycans (Tn, sTn, and T antigen) can be synthesized in the Golgi apparatus with the aid of several glycosyltransferases (such as T-synthase and ST6GalNAc-I) in a suitable environment. The unique molecular chaperone of T-synthase is Cosmc, which helps T-synthase to fold correctly in the endoplasmic reticulum. Dysregulation of these glycosyltransferases, molecular chaperones, or the environment is involved in the dysregulation of O-glycans. Tn, sTn, and T antigen neo- or over-expression occurs in many types of cancer including gastric, colon, breast, lung, esophageal, prostate, and endometrial cancer. This review discusses the major synthetic pathway of O-glycans and the mechanism by which Tn, sTn, and T antigens promote tumor metastasis.

A Bitter Sweet Symphony: Immune Responses to Altered O-glycan Epitopes in Cancer

The appearance of aberrant glycans on the tumor cell surface is one of the emerging hallmarks of cancer. Glycosylation is an important post-translation modification of proteins and lipids and is strongly affected by oncogenesis. Tumor-associated glycans have been extensively characterized regarding their composition and tumor-type specific expression patterns. Nevertheless whether and how tumor-associated glycans contribute to the observed immunomodulatory actions by tumors has not been extensively studied. Here, we provide a detailed overview of the current knowledge on how tumor-associated O-glycans affect the anti-tumor immune response, thereby focusing on truncated O-glycans present on epithelial tumors and mucins. These tumor-associated O-glycans and mucins bind a variety of lectin receptors on immune cells to facilitate the subsequently induction of tolerogenic immune responses. We, therefore, postulate that tumor-associated glycans not only support tumor growth, but also actively contribute to immune evasion.

Interaction of the Oncofetal Thomsen-Friedenreich Antigen with Galectins in Cancer Progression and Metastasis

Aberrant glycosylation of cell membrane proteins is a universal feature of cancer cells. One of the most common glycosylation changes in epithelial cancer is the increased occurrence of the oncofetal Thomsen–Friedenreich disaccharide Galβ1–3GalNAc (T or TF antigen), which appears in about 90% of cancers but is rarely seen in normal epithelium. Over the past few years, increasing evidence has revealed that the increased appearance of TF antigen on cancer cell surface plays an active role in promoting cancer progression and metastasis by interaction with the β-galactoside-binding proteins, galectins, which themselves are also frequently overexpressed in cancer and pre-cancerous conditions. This review summarizes the current understanding of the molecular mechanism of the increased TF occurrence in cancer, the structural nature, and biological impact of TF interaction with galectins, in particular galectin-1 and -3, on cancer progression and metastasis.