IL25 Enhanced Colitis-Associated Tumorigenesis in Mice by Upregulating Transcription Factor GLI1

Abstract

Interleukin-25 (IL17E/IL25) plays a critical role in colitis and intestinal homeostasis. However, the expression and biological role of IL25 in colorectal cancer is not properly understood. In this study, we show that IL25 is mainly expressed by cancer stem cells in the colorectal cancer microenvironment. Genetic deletion of IL25 inhibited tumor formation and growth and prolonged survival in AOM/DSS-treated mice. IL25 stimulated cancer organoid and cancer cells sphere formation and prevented the tumor from chemotherapy-induced apoptosis. Mechanistically, IL25 upregulated stem cell genes LGR5, CD133, and ABC transporters via activating the Hedgehog signaling pathway. IL25 inhibited phosphorylation of AMPK and promoted GLI1 accumulation to maintain cancer stem cells. Moreover, IL25 expression was associated with poor survival in patients with metastatic colorectal cancer. Taken together, our work reveals an immune-associated mechanism that intrinsically confers cancer cell stemness properties. Our results first demonstrated that IL25, as a new potent endogenous Hedgehog pathway agonist, could be an important prognostic factor and therapeutic target for CRC.

Emerging roles for IL-25 and IL-33 in colorectal cancer tumorigenesis

“…Analysis of IL-25 expression in healthy colons and CRC showed comparable levels in one report (78), while a more recent study found IL-25 expression to be elevated in human CRC tumours compared to the adjacent normal gut (80). Similar to the homeostatic intestine and mirroring IL-25 expression during parasitic infection (30), DCLK1 + tuft cells were found to be the main source of IL-25 in tumours in mouse models of APCmutation-mediated CRC (Apc 1322T/+ ) (81) and azoxymethane (AOM)/dextran sodium sulphate (DSS)-mediated model of colitis associated cancer (CAC) (80), indicating that IL-25 expression by tuft cells is conserved across different subtypes of CRC. Recently, analysis of the publicly available gene expression databases found that high IL25 expression by CRC tumours was associated with reduced CRC patient disease-free survival (81).…”

“…Conversely, conflicting reports have shown that both IL-33 and IL-25 may either promote or inhibit CAC (Table 1) (80,82,90,92,96,97), and therefore caution should be taken when considering IL-25 or IL-33-based therapy in this cohort. Another strategy would be to target IL-25 or IL-33 during early stages of IBD, to delay or prevent progression into intestinal cancer while resolving the colitis.…”

“…Conversely, IL-25 has conflicting roles in CAC. Genetic deficiency of IL-25 reduced CAC tumour burden and prolonged survival in one study (80), however others reported that antibody-mediated blockade of IL-25 instead enhanced CAC (82). As both studies employed the AOM/DSS-model of CAC, this suggests that congenital deficiency of IL-25 may have distinct effects compared to acute blockade in CAC.…”

“…Recently, analysis of the publicly available gene expression databases found that high IL25 expression by CRC tumours was associated with reduced CRC patient disease-free survival ( 81 ). Others have shown that human patients with high CRC IL-25 expression have worse 5-year overall survival than stage IV CRC patients with low IL-25 expression ( 80 ), indicating that IL-25 may contribute to CRC disease pathogenesis. As unselected CRC patients were assessed in these studies, the majority of patients would have sporadic APC-mutation-mediated CRC (85% of total CRC).…”

“…In vitro treatment with IL-33 enhanced sphere formation by primary human CRC cells and HT29 cell line, with a concomitant increase in expression of stem cell markers NANOG , NOTCH3 , OCT3 , OCT4 and LGR5 resulting in treatment resistance against 5-fluorouracil in a ST2-dependent manner ( 94 ). Others have identified that a small proportion of DCLK1 + tuft cells are Lgr5 + (stem cell marker) and may act as tumour stem cells during intestinal tumorigenesis, and that DCLK1 expression readily differentiates intestinal tumour stem cells from normal stem cells ( 80 , 150 ). DCLK1 + Lgr5 + cells can be identified in intestinal tumours that arose following activation of Wnt signaling in Lgr5 + stem cells ( 150 ), and a recent study confirmed DCLK1 as a downstream target of Wnt signaling ( 151 ).…”