P077 The acquisition of cancer stemness by Atoh1 in colitis associated cancer
K. Tsuchiya*1, K. Fukushima2, R. Hayashi2, S. Hibiya2, N. Horita2, M. Watanabe2
1Tokyo Medical and Dental University, Advanced Therapeutics for Gastrointestinal Diseases, Tokyo, Japan, 2Tokyo Medical and Dental University, Gastroenterology and Hepatology, Tokyo, Japan
The patients with inflammatory bowel disease have an increased risk of developing colitis-associated colorectal cancer (CAC). CAC often acquires the chemoresistance, resulting in the poorer prognosis than that of sporadic colorectal cancer (CRC). However, how CAC have enhanced malignant potential remains unknown. We therefore focus the pathological characteristic of CAC that shows the enrichment of mucinous carcinoma. We have assessed that APC deletion in CRC directly suppressed the differentiation system of intestinal epithelial cells (IEC), resulting in the non-mucinous form of CRC. The transcription factor Atonal homolog 1 (Atoh1) plays crucial roles in the differentiation of IECs. We have reported that aberrant Wnt signal by APC deletion causes Atoh1 protein degradation by GSK3, resulting in maintaining the undifferentiated state of CRC.
The expression of Atoh1 in mucinous cancer of four patients with CAC were assessed by immunofluorescence. The expression of Atoh1 fused with mCherry in CRC derived cell line was assessed by fluorescence microscopy. The function of GSK3 was assessed by Western blotting. Cancer stemness was assessed by spheroid-forming assay. Cell cycle was assessed using FUCCI system. Chemo-resistance was assessed by MTS assay.
Atoh1 protein was expressed in mucinous cancer of the patients with CAC. The treatment with TNF- α resulted in the stable expression of Atoh1 in CRC cell line by inducing the dysfunction of GSK3 β phosphorylated by AKT. Microarray analysis revealed the acquisition of the mucus-secreting form by Atoh1 protein stabilization. Moreover, Atoh1 protein enriched cancer stem cells with enhanced cell migration. Furthermore, Atoh1 protein induced cell cycle arrest in G0/G1 phase, resulting in the chemo-resistance to oxaliplatin.
Atoh1 protein stabilized by TNF- α might acquire both mucinous phenotype and more malignant potential in CAC, suggesting that the inflammation on carcinogenesis might preserve the differentiation system of IEC, resulting in the acquisition of both mucinous phenotype and enhanced malignant potential including the enrichment of cancer stem cells.