Aberrant glycosylation is a hallmark of cancer and is not just a consequence, but also a driver of a malignant phenotype. In prostate cancer, changes in fucosylated and sialylated glycans are common and this has important implications for tumor progression, metastasis, and immune evasion. Glycans hold huge translational potential and new therapies targeting tumor-associated glycans are currently being tested in clinical trials for several tumor types. Inhibitors targeting fucosylation and sialylation have been developed and show promise for cancer treatment, but translational development is hampered by safety issues related to systemic adverse effects. Recently, potent metabolic inhibitors of sialylation and fucosylation were designed that reach higher effective concentrations within the cell, thereby rendering them useful tools to study sialylation and fucosylation as potential candidates for therapeutic testing. Here, we investigated the effects of global metabolic inhibitors of fucosylation and sialylation in the context of prostate cancer progression. We find that these inhibitors effectively shut down the synthesis of sialylated and fucosylated glycans to remodel the prostate cancer glycome with only minor apparent side effects on other glycan types. Our results demonstrate that treatment with inhibitors targeting fucosylation or sialylation decreases prostate cancer cell growth and downregulates the expression of genes and proteins important in the trajectory of disease progression. We anticipate our findings will lead to the broader use of metabolic inhibitors to explore the role of fucosylated and sialylated glycans in prostate tumor pathology and may pave the way for the development of new therapies for prostate cancer.

Prostate cancer is a lethal solid malignancy and a leading cause of cancer-related deaths in males worldwide. Treatments, including radical prostatectomy, radiotherapy, and hormone therapy, are available and have improved patient survival; however, recurrence remains a huge clinical challenge. Enzalutamide is a second-generation androgen receptor antagonist that is used to treat castrate-resistant prostate cancer. Among patients who initially respond to enzalutamide, virtually all acquire secondary resistance, and an improved understanding of the mechanisms involved is urgently needed. Aberrant glycosylation, and, in particular, alterations to sialylated glycans, have been reported as mediators of therapy resistance in cancer, but a link between tumour-associated glycans and resistance to therapy in prostate cancer has not yet been investigated. Here, using cell line models, we show that prostate cancer cells with acquired resistance to enzalutamide therapy have an upregulation of the sialyltransferase ST6 beta-galactoside alpha-2,6-sialyltransferase 1 (ST6GAL1) and increased levels of α2,6-sialylated N-glycans. Furthermore, using the sialyltransferase inhibitor P-SiaFNEtoc, we discover that acquired resistance to enzalutamide can be partially reversed by combining enzalutamide therapy with sialic acid blockade. Our findings identify a potential role for ST6GAL1-mediated aberrant sialylation in acquired resistance to enzalutamide therapy for prostate cancer and suggest that sialic acid blockade in combination with enzalutamide may represent a novel therapeutic approach in patients with advanced disease. Our study also highlights the potential to bridge the fields of cancer biology and glycobiology to develop novel combination therapies for prostate cancer.

Prostate cancer is a common cancer in males and there is an urgent unmet clinical need to improve early diagnosis and identify new treatments for advanced disease. Despite huge progress in understanding changes to the genome and proteome in prostate cancer, there is a relative delay in revealing the full aspects of the prostate cancer glycome and glycoproteome. Glycobiology has been fundamental in recent discoveries in the medical field, including translational cancer research. Glycans functionally contribute to the cancer hallmarks and serve as important diagnostic biomarkers and targets for therapeutic intervention. Changes to glycans are common in prostate cancer and include increased branching of complex N- glycans, changes in sialylation, increased fucosylation, altered PSA glycosylation and the expression of truncated O- glycans. This review discusses the role of glycans in fundamental mechanisms controlling prostate cancer growth, metastasis and immune evasion. Emphasis is placed on discoveries made during the last decade, including new insights provided by N- glycan imaging mass spectrometry (IMS) profiling of prostate cancer tissues, new discoveries into the role of aberrant glycosylation in prostate tumour biology, as well as recent studies investigating glycans, glycosyltransferase enzymes and glycan binding proteins as therapeutic targets.

CYLD cutaneous syndrome (CCS) skin tumours develop from puberty onwards, can number in the hundreds and progressively grow over time. CCS patients lack medical therapies and require repeated surgery to control tumour burden. CYLD loss of heterozygosity (LOH) drives tumour growth, and CCS tumours have previously been shown to demonstrate increased canonical NF-κB and Wnt signalling. Here, we demonstrate evidence of non-canonical NF-κB signalling in CCS tumour keratinocytes, with increased p100 to p52 processing and RelB protein expression compared to normal skin. Utilizing complementary transcriptomics and proteomics on patient derived CCS tumour cell fractions, we identify IκB kinase alpha (IKKα) as a candidate target in the non-canonical NF-κB signalling pathway. A novel, highly selective, IKKα inhibitor (SU1644) used in patient derived CCS tumour spheroid cultures demonstrated that IKKα inhibition reduced tumour spheroid viability. These data provide the pre-clinical rationale for the assessment of topical IKKα inhibitors as a novel preventative treatment for CCS.

CYLD cutaneous syndrome (CCS) skin tumors develop from puberty onwards, can number in the hundreds and progressively grow over time. CCS patients lack medical therapies and require repeated surgery to control tumor burden. CYLD loss of heterozygosity (LOH) drives tumor growth, and CCS tumors have previously been shown to demonstrate increased canonical NF-κB and Wnt signalling. Here, we demonstrate evidence of non-canonical NF-κB signalling in CCS tumor keratinocytes, with increased p100 to p52 processing and RelB protein expression compared to normal skin. Utilizing complementary transcriptomics and proteomics on patient derived CCS tumor cell fractions, we identify IκB kinase alpha (IKKα) as a candidate target in the non-canonical NF-κB signalling pathway. A novel, highly selective, IKKα inhibitor (SU1644) used in patient derived CCS tumor spheroid cultures demonstrated that IKKα inhibition reduced tumor spheroid viability. These data provide the pre-clinical rationale for the assessment of topical IKKα inhibitors as a novel preventative treatment for CCS. Teaser: Topical IKKα inhibition emerges as a potential therapy for CYLD cutaneous syndrome by targeting non-canonical NF-κB signalling Graphical