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* = Presenting author

P040 Sonic hedgehog inhibitor prevented colitis-associated cancer via concerted mechanisms of IL-6/gp130 inhibition, 15-prostaglandin dehydrogenase induction, Bcl-2 abrogation, and tumour sphere inhibition

K. B. Hahm*1, N. Kangwan1, Y. J. Kim2

1CHA University, Gastroenterology, Seongnam, South Korea, 2Gachon University, Gastroenterology, Incheon, South Korea

Background

Sonic hedgehog (SHH) signalling is essential in normal development of gastrointestinal (GI) tracts, by which aberrantly activated SHH is implicated in GI cancers through redirecting stem cells to facilitate carcinogenesis. Because colitis-associated cancer (CAC) is associated with inflammatory bowel diseases, in which SHH/ IL-6 signalling/ inflammation/ cancer stem cell (CSC) activation has been engaged, we hypothesised that SHH inhibitors can prevent colitis-associated cancer through blocking above SHH-related carcinogenic pathways.

Methods

Intestinal epithelial cell IEC-6 and colon cancer cell HCT-116 were stimulated by TNF-α. IL-6 expressions and signalling after SHH inhibitors were measured by RT-polymerase chain reaction (PCR), Western blot, confocal imaging, luciferase assay, and ELISA, and levels of other inflammatory mediators and NF-kB, proliferation, apoptosis, and tumour sphere formation, and tumourigenesis were measured after SHH inhibitors. CAC was induced in C57BL/6 mice by 3 mg/kg azoxymethane (AOM) followed by 2% DSS administration. SHH inhibitors were treated by oral gavage, and the mice were sacrificed at 16 weeks.

Results

TNF-α-stimulated IEC-6 cells exhibited increased pro-inflammatory cytokines including IL-6, iNOS, TNF-α, and IL-8, but SHH inhibitors suppressed TNF-α-induced inflammatory signalling, especially significantly emphasising on IL-6/IL-6R/gp130 (p < 0.01). SHH inhibitors significantly induced apoptosis, inhibited cellular proliferation, and suppressed tumour sphere formation, as well as stemness factors. In CAC models, SHH inhibitors significantly reduced tumour incidence and tumour multiplicity, in which SHH inhibitors not only decreased the expressions of IL-6, as well as TNF-α, COX-2, STAT3 and NF-kB, but also induced significant apoptosis. On xenograft using colospheres, SHH significantly inhibited tumourigenesis specifically through inhibiting tumour sphere.

Conclusion

SHH inhibitor could be an effective strategy to prevent colitis-induced colorectal carcinogenesis principally targeted IL-6 signalling and cancer stem cells ablation, in addition to suppression of oncogenic inflammations.