Fig. 6.

Sialic acid blockade can prevent/inhibit prostate cancer bone metastasis. (a) Inhibition of sialylation in TRAMPC2 cells using P-SiaFNEtoc detected using pan-specific Lectenz lectin flow cytometry.⁷⁴ Cells were treated with a range of concentrations of P-SiaFNEtoc inhibitor from 2 μM to 512 μM for 72 h. The intensities were normalised to a DMSO control. (b) Detection of α2-6 linked sialylated N-glycans in TRAMPC2 cells using SNA lectin flow cytometry. TRAMPC2 cells treated with 64 μM P-SiaFNEtoc for 72 h had reduced levels of SNA binding indicating a reduction in α2-6 linked sialylation in these cells (unpaired t test, p = 0.0001). (c) Luciferase tagged TRAMPC2 cells (control or pre-treated with 64 μM P-SiaFNEtoc for 72 h) were injected into immunocompetent C57BL/6 mice via sub-cutaneous injection and tumours were monitored using in vivo bioluminescence imaging. Pre-treatment of TRAMPC2 cells with P-SiaFNEtoc (which removed sialylated glycans) significantly reduced tumour burden over 6 weeks (n = 10, Mann–Whitney test, p = 0.0233) thus suggesting that sialic acid blockade has the potential to inhibit the growth of prostate tumours. (d) Inhibition of sialylation in RM1 cells using P-SiaFNEtoc detected using pan-specific Lectenz lectin flow cytometry.⁷⁴ Cells were treated with a range of concentrations of P-SiaFNEtoc inhibitor from 2 μM to 512 μM for 72 h. The intensities were normalised to a DMSO control. (e) Detection of α2-6 linked sialylated N-glycans in RM1 cells using SNA lectin flow cytometry. RM1 cells treated with 256 μM P-SiaFNEtoc for 72 h had reduced levels of SNA binding indicating a reduction in α2-6 linked sialylation in these cells (unpaired t test, p < 0.0001). (f) Luciferase tagged RM1 cells (control or pre-treated with 256 μM P-SiaFNEtoc for 72 h) were injected into immunocompetent C57BL/6 mice via intra cardiac injection. Tumours were monitored over 15 days using in vivo bioluminescence imaging. (g,h) Pre-treatment of RM1 cells with P-SiaFNEtoc (to remove sialylated glycans) significantly reduced the number of skeletal tumours formed (Mann–Whitney test, p = 0.0454), the incidence of tumour in left tibias (Chi-square test, p = 0.0455), and significantly increased survival time in mice (Log-rank test, p = 0.012). (i) Micro-CT analysis demonstrated that P-SiaFNEtoc significantly alleviated bone destruction in the trabecular bone of tibias and increased trabecular bone volume (BV/TV, p = 0.0211) and trabecular number (Tb. N, p = 0.035) (n = 9, unpaired t test, ∗p < 0.05). Representative images are shown. Scale bar is 200 μm.